Ophthalmology

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Ophthalmology is the branch of medicine which deals with the diseases of the eye and their treatment. The word ophthalmology comes from the Greek roots ophthalmos meaning eye and logos meaning word; ophthalmology literally means "The science of eyes." As a discipline it applies to animal eyes also, since the differences from human practice are surprisingly minor and are related mainly to differences in anatomy or prevalence, not differences in disease processes. By convention the term ophthalmologist is more restricted and implies a medically trained specialist. Since ophthalmologists perform operations on eyes, they are generally categorized as surgeons.

Contents

[edit] History of ophthalmology

The eye, including its structure and mechanism, has fascinated scientists and the public in general since ancient times. The discovery of the eye went through two cycles of limiting speculation and freeing observation, which led to a dark age between Galen and Vesalius.

Arab scientists are some of the earliest to have written about and drawn the anatomy of the eye—the earliest known diagram being in Hunain ibn Is-hâq's Book of the Ten Treatises on the Eye. Earlier manuscripts exist which refer to diagrams which are not known to have survived. Current knowledge of the Græco-Roman understanding of the eye is limited, as many manuscripts lacked diagrams. In fact, there are very few Græco-Roman diagrams of the eye still in existence. Thus, it is not clear to which structures the texts refer, and what purpose they were thought to have.

The pre-Hippocratics largely based their anatomical conceptions of the eye on speculation, rather than empiricism. They recognised the sclera and transparent cornea running flushly as the outer coating of the eye, with an inner layer with pupil, and a fluid at the centre. It was believed, by Alcamaeon and others, that this fluid was the medium of vision and flowed from the eye to the brain via a tube. Aristotle advanced such ideas with empiricism. He dissected the eyes of animals, and discovering three layers (not two), found that the fluid was of a constant consistency with the lens forming (or congealing) after death, and the surrounding layers were seen to be juxtaposed. He, and his contemporaries, further put forth the existence of three tubes leading from the eye, not one. One tube from each eye met within the skull.

Alexandrian studies extensively contributed to knowledge of the eye. Aëtius tells us that Herophilus dedicated an entire study to the eye which no longer exists. In fact, no manuscripts from the region and time are known to have survived, leading us to rely on Celsius' account—which is seen as a confused account written by a man who did not know the subject matter. From Celsius it is known that the lens had been recognised, and they no longer saw a fluid flowing to the brain through some hollow tube, but likely a continuation of layers of tissue into the brain. Celsius failed to recognise the retina's role, and did not think it was the tissue that continued into the brain.

Rufus recognised a more modern eye, with conjunctiva, extending as a fourth epithelial layer over the eye. Rufus was the first to recognise a two chambered eye - with one chamber from cornea to lens (filled with water), the other from lens to retina (filled with an egg-white-like substance). Galen remedied some mistakes including the curvature of the cornea and lens, the nature of the optic nerve, and the existence of a posterior chamber. Though this model was roughly a correct but simplistic modern model of the eye, it contained errors. Yet it was not advanced upon again until after Vesalius. A ciliary body was then discovered and the sclera, retina, choroid and cornea were seen to meet at the same point. The two chambers were seen to hold the same fluid as well as the lens being attached to the choroid. Galen continued the notion of a central canal, though he dissected the optic nerve, and saw it was solid, He mistakenly counted seven optical muscles, one too many. He also knew of the tear ducts.

After Galen a period of speculation is again noted by Arab scientists - the lens modified Galen's model to place the lens in the middle of the eye, a notion which lasted until Versalius reversed the era of speculation. He, however, was not an ophthalmologist and taught that the eye was a more primitive notion than the notion of both Galen and the Arabian scientists - the cornea was not seen as being of greater curvature and the posterior side of the lens wasn't seen to be larger.

Understanding of the eye had been so slow to develop because for a long time the lens was perceived to be the seat of vision, not a tool of vision. This mistake was corrected when Fabricius and his successors correctly placed the lens and developed the modern notion of the structure of the eye. They removed the idea of Galen's seventh muscle (the retractor bulbi) and reinstated the correct curvatures of the lens and cornea, as well as stating the ciliary body as a connective structure between the lens and the choroid.

The seventeenth and eighteenth century saw the use of hand-lenses (by Malpighi), microscopes (van Leeuwenhoek), preparations for fixing the eye for study (Ruysch) and later the freezing of the eye (Petit). This allowed for detailed study of the eye and an advanced model. Some mistakes persisted such as: why the pupil changed size (seen to be vessels of the iris filling with blood), the existence of the posterior chamber, and of course the nature of the retina. In 1722 Leeuwenhoek noted the existence of rods and cones though they were not properly discovered until Treviranus in 1834 by use of a microscope.

The establishment of the first dedicated ophthalmic hospital in 1805 - now called Moorfields Eye Hospital in London, England was a transforming event in modern ophthalmology. Clinical developments at Moorfields and the founding of the Institute of Ophthalmology by Sir Stewart Duke-Elder established the site as the largest eye hospital in the world and a nexus for ophthalmic research.

[edit] Professional requirements

Ophthalmologists are medical doctors who have completed medical school and embark on a training schedule that generally lasts four years after medical school in most countries. Many ophthalmologists also undergo additional specialized training in one of the many subspecialities. Ophthalmology was the first branch of medicine to offer board certification, now a standard practice among all specialties.

In the United States, four years of training after medical school are required, with the first year being an internship in surgery, internal medicine, pediatrics, or a general transition year. The scope of a physician's licensure is such that he or she need not be board certified in ophthalmology to practice as an ophthalmologist. The American Academy of Ophthalmology (AAO) promotes the use of the phrase "Eye MD" to distinguish ophthalmologists from optometrists who hold the degree OD (Doctor of Optometry). (This, however, sometimes leads to confusion among patients, since a few ophthalmologists' primary medical degree is a D.O., or Doctor of Osteopathy, rather than an M.D. In both cases, the same residency and certification requirements must be fulfilled.) Completing the requirements of continuing medical education is mandatory for continuing licensure and re-certification. Professional bodies like AAO, ASCRS organise conferences and help members through CME programs to maintain certification, in addition to congress advocacy and peer support.

In the United Kingdom, there are four Colleges that grant post graduate degree. The Royal College of Ophthalmologists grants MRCOphth and FRCOphth (postgraduate exams), Royal college of Edinburgh grants MRCSEd, Royal college of Glasgow grants FRCS and Royal college of Ireland grants FRCSI. Work experience as specialist registrar and one of these degrees is required for specialisation in eye diseases.

In Australia and New Zealand, the FRACO/FRANZCO is the equivalent postgraduate specialist qualification. They do not generally accept outsiders with equivalent qualifications and require repeat training on case by case basis, with possibility of certification for doctors with numerous international publications, desirous of joining academic institutions in Australia.

In India, after completing MBBS degree, post-graduation in the form of a Junior Residency at a Medical College, Hospital or Institution under the supervision of experienced faculty leading to degree of Doctor of Medicine (M.D.) or Master of Surgery (M.S.), or Diplomate of National Board (D.N.B.) degree, or a diploma course leading to (Diploma in Ophthalmic Medicine and Surgery (D.O.M.S.) in Ophthalmology is necessary before one can expertly deal with various problems of the eye. Further work experience in form of fellowship, registrar or senior resident refines the skills of these eye surgeons. All India Ophthalmological Society (AIOS) and various state level Ophthalmological Societies hold regular conferences and actively promote continuing medical education.

In Pakistan, there is a residency program leading into FCPS which is composed of two parts.

In Canada, an Ophthalmology residency after medical school and FRCSC is the requirement for becoming a licenced Ophthalmologist. There are about 10 seats per year in whole of Canada for Ophthalmology residency.

Formal specialty training programs in veterinary ophthalmology now exist in some countries [1] [2] [3].

[edit] Sub-specialities

Ophthalmology includes sub-specialities which deal either with certain diseases or diseases of certain parts of the eye. Some of them are:

Ophthalmic investigations

[edit] Anatomy of Eye

Schematic diagram of the human eye.

The structure of the human eye owes itself completely to the task of focusing light onto the retina. All of the individual components through which light travels within the eye before reaching the retina are transparent, minimising dimming of the light. The cornea and lens help to converge light rays to focus onto the retina. This light causes chemical changes in the photosensitive cells of the retina, the products of which trigger nerve impulses which travel to the brain.

Light enters the eye from an external medium such as air or water, passes through the cornea, and into the first of two humours, the aqueous humour. Most of the light refraction occurs at the cornea which has a fixed curvature. The first humour is a clear mass which connects the cornea with the lens of the eye, helps maintain the convex shape of the cornea (necessary to the convergence of light at the lens) and provides the corneal endothelium with nutrients. The iris, between the lens and the first humour, is a coloured ring of muscle fibres. Light must first pass though the centre of the iris, the pupil. The size of the pupil is actively adjusted by the circular and radial muscles to maintain a relatively constant level of light entering the eye. Too much light being let in could damage the retina; too little light makes sight difficult. The lens, behind the iris, is a convex, springy disk which focuses light, through the second humour, onto the retina.

Diagram of a human eye. Note that not all eyes have the same anatomy as a human eye.

To clearly see an object far away, the circularly arranged ciliary muscles will pull on the lens, flattening it. Without muscles pulling on it, the lens will spring back into a thicker, more convex, form. Humans gradually lose this flexibility with age, resulting in the inability to focus on nearby objects, which is known as presbyopia. There are other refraction errors arising from the shape of the cornea and lens, and from the length of the eyeball. These include myopia, hyperopia, and astigmatism.

On the other side of the lens is the second humour, the vitreous humour, which is bounded on all sides: by the lens, ciliary body, suspensory ligaments and by the retina. It lets light through without refraction, helps maintain the shape of the eye and suspends the delicate lens.

Light from a single point of a distant object and light from a single point of a near object being brought to a focus.

Three layers, or tunics, form the wall of the eyeball. The outermost is the sclera which gives the eye most of its white colour. It consists of dense connective tissue filled with the protein collagen to both protect the inner components of the eye and maintain its shape. On the inner side of the sclera is the choroid, which contains blood vessels that supply the retinal cells with necessary oxygen and remove the waste products of respiration. Within the eye, only the sclera and ciliary muscles contain blood vessels. The choroid gives the inner eye a dark colour, which prevents disruptive reflections within the eye. The inner most layer of the eye is the retina, containing the photosensitive rod and cone cells, and neurons.

To maximise vision and light absorption, the retina is a relatively smooth (but curved) layer. It does have two points at which it is different; the fovea and optic disc. The fovea is a dip in the retina directly opposite the lens, which is densely packed with cone cells. It is largely responsible for color vision in humans, and enables high acuity, such as is necessary in reading. The optic disc, sometimes referred to as the anatomical blind spot, is a point on the retina where the optic nerve pierces the retina to connect to the nerve cells on its inside. No photosensitive cells whatsoever exist at this point, it is thus "blind".

In some animals, the retina contains a reflective layer (the tapetum lucidum) which increases the amount of light each photosensitive cell perceives, allowing the animal to see better under low light conditions.

[edit] Other articles regarding eye anatomy

Aqueous humour, Annulus of Zinn, Anterior chamber, Ciliary body, Ciliary muscle, Cornea, Conjunctiva, Choroid, Fovea, Iris, Lens, Macula, Nictitating membrane, Optic disc, Optic nerve, Ora serrata, Posterior chamber, Pupil, Retina, Schlemm's canal, Sclera, Suspensory ligament, Tapetum lucidum, Trabecular meshwork, Vitreous humour, Zonule of Zinn.


An eye examination is a battery of tests performed by an ophthalmologist or optometrist assessing vision and ability to focus on and discern objects, as well as other tests and examinations pertaining to the eyes. All people should have periodic and thorough eye examinations as part of routine care by the primary care physician, especially since many eye diseases are silent or asymptomatic.

Eye examinations may detect potentially treatable blinding eye diseases, ocular manifestations of systemic disease, or signs of tumours or other anomalies of the brain.

[edit] Comprehensive eye examination

Traditional Snellen chart used for visual acuity testing. Illustration only; this is a scaled image and hence not suitable for vision testing.
Slit lamp examination of the eyes in an ophthalmology clinic

[edit] Case history

[edit] Entrance tests

[edit] Refraction

  • Monocular
  • Binocular balance

[edit] Functional tests

[edit] Health assessment

[edit] Setting

Ideally, the eye examination consists of an external examination, followed by specific tests for visual acuity, pupil function, extraocular muscle motility, visual fields, intraocular pressure and ophthalmoscopy through a dilated pupil.

A minimal eye examination consists of tests for visual acuity, pupil function, and extraocular muscle motility, as well as direct ophthalmoscopy through an undilated pupil.

[edit] Basic examination

[edit] External examination

External examination of eyes consists of inspection of the eyelids, surrounding tissues and palpebral fissure. Palpation of the orbital rim may also be desirable, depending on the presenting signs and symptoms. The conjunctiva and sclera can be inspected by having the individual look up, and shining a light while retracting the upper or lower eyelid. The cornea and iris may be similarly inspected.

[edit] Visual acuity

Main article: Visual acuity

Visual acuity is the eye's ability to detect fine details and is the quantitative measure of the eye's ability to see an in-focus image at a certain distance. The standard definition of normal visual acuity (20/20 or 6/6 vision) is the ability to resolve a spatial pattern separated by a visual angle of one minute of arc. This is often measured with a Snellen chart.

[edit] Pupil function

Main article: Pupil

An examination of pupilary function includes inspecting the pupils for equal size (1 mm or less of difference may be normal), regular shape, reactivity to light, and direct and consensual accommodation. These steps can be easily remembered with the mnemonic PERRLA (D+C): Pupils Equal and Regular; Reactive to Light and Accommodation (Direct and Consensual).

A swinging-flashlight test may also be desirable if neurologic damage is suspected. The swinging-flashlight test is the most useful clinical test available to a general physician for the assessment of optic nerve anomalies. This test detects the afferent pupil defect, also referred to as the Marcus Gunn pupil. In a normal reaction to the swinging-flashlight test, both pupils constrict when one is exposed to light. As the light is being moved from one eye to another, both eyes begin to dilate, but constrict again when light has reached the other eye.

If there is an efferent defect in the left eye, the left pupil will remain dilated regardless of where the light is shining, while the right pupil will respond normally. If there is an afferent defect in the left eye, both pupils will dilate when the light is shining on the left eye, but both will constrict when it is shining on the right eye.

If there is a unilateral small pupil with normal reactivity to light, it is unlikely that a neuropathology is present. However, if accompanied by ptosis of the upper eyelid, this may indicate Horner's syndrome.

If there is a small, irregular pupil that constricts poorly to light, but normally to accommodation, this is an Argyll Robertson pupil, which is a sign of tertiary syphilis.

[edit] Ocular motility

Main article: Extraocular muscles

Ocular motility should always be tested, especially when patients complain of double vision or physicians suspect neurologic disease. First, the doctor should visually assess the eyes for deviations that could result from strabismus, extraocular muscle dysfunction, or oculomotor nerve dysfunction. Saccades are assessed by having the patient move his or her eye quickly to a target at the far right, left, top and bottom.

Slow tracking is assessed by the 'follow my finger' test, in which the examiner's finger traces an imaginary "H", which touches upon the six cardinal fields of gaze. These test the inferior, superior, lateral and medial rectus muscles of the eye, as well as the superior and inferior oblique muscles.

[edit] Visual field (confrontation) testing

Main article: Visual field
Main article: Visual field test

Evaluation of the visual fields should never be omitted from the basic eye examination. Testing the visual fields consists of confrontation field testing in which each eye is tested separately to assess the extent of the peripheral field. To perform the test, the individual occludes one eye while fixated on the examiner's eye with the non-occluded eye. The patient is then asked to count the number of fingers that are briefly flashed in each of the four quadrants. This method is preferred to the wiggly finger test that was historically used because it represents a rapid and efficient way of answering the same question: is the peripheral visual field affected?

Common problems of the visual field include scotoma (area of reduced vision), hemianopia (half of visual field lost), homonymous quadrantanopia (involving both eyes) and bitemporal hemianopia.

[edit] Intraocular pressure

Intraocular pressure can be measured by any of a series of devices designed to measure the outflow (and resistance to outflow) of the aqueous humour from the eye.

[edit] Ophthalmoscopy

A red reflex can be seen when looking at a patient's pupil through a direct ophthalmoscope. This part of the examination is done from a distance of about 50 cm. The actual colour varies with the patient's complexion, but should be symmetrical between the two eyes. An opacity may indicate a cataract.

Ophthalmoscopy allows the physician to look directly at the retina and other tissue at the back of the eye. This is best done after the pupil has been dilated with eye drops. A limited view can be obtained through an undilated pupil, in which case best results are obtained with the room darkened and the patient looking towards the far corner.

The optic disc and retinal arteries and veins are the main focus of examination during ophthalmoscopy. The optic disc should appear slightly oval, with a pink colour.

[edit] Slit lamp

Close inspection with a slit lamp is performed to detect eye diseases. A small vertical beam of light is run over the eye horizontally. It allows inspection of all the media, from cornea to vitreous, and ophthalmoscopy can also be performed through the slit lamp. The binocular slit-lamp examination provides stereoscopic magnified view of the eye structures in striking detail, enabling exact anatomical diagnoses to be made for a variety of eye conditions. Combined with special lenses like Goldmann 3-mirror lens, Gonioscopy single-mirror/ Zeiss 4-mirror lens for angle structures and +90D lens, +78D lens, +66D lens & Hruby (-56D) lens, the examination of retinal structures is accomplished.

Fluorescein staining before slit lamp examination may reveal corneal abrasions or herpes simplex infection.

[edit] References

[edit] See also

[edit] Conditions diagnosed during eye examinations

Main article: List of eye diseases and disorders

[edit] Other tests that may be performed during eye examinations

[edit] Miscellaneous

Template:Physical exam


[edit] Ophthalmic surgery

See eye surgery for a comprehensive list of surgeries performed by ophthalmologists.

[edit] Famous ophthalmologists

See also: Category:Ophthalmologists.

  • Ioannis Pallikaris (Greece), introduced LASIK surgery.
  • Sir William Adams (UK) Founder of Exeter's West of England Eye Infirmary.
  • Ignacio Barraquer (Spain) carried out the first intracapsular lens extraction using enzymatic zonulolysis.
  • Alan C. Bird (U.K.) pioneer in medical retina and ophthalmic genetics in the second half of the 20th century. Based at Moorfields Eye Hospital and the Institute of Ophthalmology at University College London.
  • Ramon Castroviejo (Spain) pioneer in corneal transplantation surgery.
  • Marie Colinet, wife of Wilhelm Fabry, employs a magnet for removing a foreign body from the eye, 1627.
  • Florent Cunier (Belgium) founded the world's first ophthalmologic journal, Annales d'Oculistique, 1838.
  • Jacques Daviel (Normandy) claimed to be the 'father' of modern cataract surgery in that he performed intracapsular extraction instead of needling the cataract or pushing it back into the vitreous. It is said that he carried out the technique on 206 patients in 1752-3, out of which 182 were reported to be successful. These figures are not very credible, given the total lack of both anaesthesia and aseptic technique at that time.
  • Frans Cornelis Donders (Dutch) published pioneering analyses of ocular biomechanics, intraocular pressure, glaucoma, and physiological optics. Made possible the prescribing of combinations of spherical and cylindrical lenses to treat astigmatism.
  • Sir Stewart Duke-Elder (U.K.) Author of System of Ophthalmology, an immensely influential mid-20th century multivolume compendium of ophthalmic history, embryology, comparative ophthalmology, refraction, ocular basic sciences, medical ophthalmology and therapeutics, but avoiding discussion of surgical techniques (which he viewed as ephemera). Consultant at Moorfields Eye Hospital and founder of the Institute of Ophthalmology (now an integral part of University College London)
  • Svyatoslav Fyodorov (Russia) - creator of radial keratotomy
  • Jules Gonin (Switzerland)
  • Albrecht von Graefe (Germany) Along with Helmholtz and Donders, one of the 'founding fathers' of ophthalmology as a specialty. A brilliant clinician and charismatic teacher who had an international influence on the development of ophthalmology. A pioneer in mapping visual field defects and diagnosis and treatment of glaucoma. Introduced a cataract extraction technique that remained the standard for over 100 years, and many other important surgical techniques such as iridectomy. Rationalised the use of many ophthalmically important drugs, including mydriatics & miotics. The founder of the one of the earliest ophthalmic societies (German Ophthalmological Society, 1857) and one of the earliest ophthalmic journals (Graefe's Archives of Ophthalmology). The most important ophthalmologist of the 19th century.
  • Allvar Gullstrand (Sweden), Nobel Prize winner in 1911 for his research on the eye as a light-refracting apparatus. Described the schematic eye a mathematical model of the human eye based on his measurements known as the optical constants of the eye. His measurements are still used today.
  • Hermann von Helmholtz, great German polymath, invented the ophthalmoscope (1851) and published important work on physiological optics, including colour vision (1850s).
  • Fred Hollows (New Zealand/Australia) pioneered programs in Nepal, Eritrea, and Vietnam, and among Australian aborigines, including the establishment of cheap laboratory production of intraocular lenses in Nepal and Eritrea.
  • Charles Kelman (United States) developed the cryo-probe used in intracapsular cataract extraction; introduced extracapsular cataract extraction and Kelman phacoemulsification.
  • P. Siva Reddy (India) holds the world record for the highest number of cataract operations by an individual doctor.
  • Sir Harold Ridley (U.K.) may have been the first to successfully implant an artificial intraocular lens 1949, after observing that plastic fragments in the eyes of wartime pilots were well tolerated. He fought for decades against strong reactionary opinions to have the concept accepted as feasible and useful.
  • Charles Schepens (Belgium), "father of modern retinal surgery", developer of the Schepens indirect binocular ophthalmoscope whilst at Moorfields Eye Hospital, founder of the Schepens Eye Research Institute, Boston, USA. This premier research institute is associated with Harvard Medical School and Massachusetts Eye & Ear Infirmary.
  • Hermann Snellen (Netherlands) introduced the Snellen chart to study visual acuity.
  • Carl Ferdinand Ritter von Arlt, the elder (Austrian) proved that myopia is largely due to an excessive axial length, published influential textbooks on eye disease, and ran annual eye clinics in needy areas long before the concept of volunteer eye camps became popular. His name is still attached to some disease signs, eg, von Arlt's line in trachoma. His son Ferdinand Ritter von Arlt, the younger, was also an ophthalmologist.
  • Vladimir Petrovich Filatov (Ukraine) (1875-1956) His contributions to the medical world include the tube flap grafting method, corneal transplantation and preservation of grafts from cadaver eyes and tissue therapy. He founded The Filatov Institute of Eye Diseases & Tissue Therapy, Odessa, one of the leading eye care institutes in the world.

[edit] See also

[edit] External links

Template:Medicine


Eye surgery, also known as ophthalmic surgery or ocular surgery, is a surgical procedure performed on the eye or its adnexa, typically by an ophthalmologist. [1]

[edit] Laser surgery and incisional surgery

Although the terms "laser eye surgery" and "refractive surgery" are commonly used as if they were interchangeable, this is not the case. Lasers may be used to treat nonrefractive conditions (e.g. to seal a retinal tear), while radial keratotomy is an example of refractive surgery without the use of a laser.

[edit] Types of eye surgeries

[edit] Cataract surgery

Main article: Cataract surgery

A cataract is an opacification or cloudiness of the eye's crystalline lens due to aging, disease, or trauma that typically prevents light from forming a clear image on the retina. If visual loss is significant, surgical removal of the lens may be warranted, with lost optical power usually replaced with a plastic intraocular lens (IOL). Due to the high prevalence of cataracts, cataract extraction is the most common eye surgery.[2]


Cataract in Human Eye- Magnified view seen on examination with a slit lamp

Cataract surgery is the removal of the lens of the eye that has developed a cataract. The natural lens is then replaced with an artificial intraocular lens. It is one of the safest and most successful procedures in all of medicine.

The two main types of cataract extraction are intracapsular cataract extraction (ICCE) and extracapsular cataract extraction (ECCE).

Extracapsular cataract extraction involves the removal of the lens while the elastic lens capsule is left partially intact to allow implantation of an intraocular lens[3]. There are two main types of extracapsular surgery: conventional ECCE and phacoemulsification. Conventional extracapsular cataract extraction involves manual expression of the lens through an incision made in the cornea or sclera. Although it requires a larger incision and the use of stitches, the conventional method is indicated for patients with very hard cataracts or lower counts of corneal endothelial cells. Phacoemulsification involves the use of a machine with an ultrasonic handpiece with a titanium or steel needle which vibrates at ultrasonic frequency under continuous irrigation to sculpt, chop and emulsify the cataract, thus making it easier to aspirate the fine particles. Irrigation-aspiration can then be performed with a bimanual system to clean out the cortical matter. Thereafter, a foldable Intraocular lens (IOL) made of Silicone or Acrylic materials of appropriate power is implanted using a holder/folder, or a proprietary insertion device provided along with the IOL. It is placed in the posterior chamber in-the-bag after cleaning out the cataract. Because a smaller incision is required, few or no stitches are needed and the patient's recovery time is usually shorter. [4][3].

Intracapsular cataract extraction (ICCE) involves the removal of the lens and the surrounding lens capsule in one piece. The lens is then replaced with an artificial plastic lens (an intraocular lens implant) of appropriate power which remains permanently in the eye. The procedure has a relatively high rate of complications due to the large incision required and pressure placed on the vitreous body, thus is rarely performed in countries where operating microscopes and high-technology equipment are readily available[3]. Cryoextraction is a form of ICCE that freezes the lens with a cryogenic substance such as liquid nitrogen[5]. Although it is now used primarily for the removal of subluxated lenses, it was the favored form of cataract extraction from the late 1960s to the early 1980s[6].

A capsulotomy, rarely known as cystitomy, is a procedure to open a portion of the lens capsule. An anterior capsulotomy refers to the opening of the front portion of the lens capsule, whereas a posterior capsulotomy refers to the opening of the back portion of the lens capsule. In an extracapsular surgery, the surgeon performs an anterior capsulotomy, or capsulorhexis, to create an opening through which the lens nucleus can be removed and the intraocular lens implant inserted. An opacification or clouding of the posterior lens capsule frequently occurs in those who have had an extracapsular cataract extraction procedure, therefore, a laser posterior capsulotomy, or YAG laser capsulotomy, is used to clear the back implant surface [7]. (Whereas a capsulotomy is the creation of an opening in the lens capsule, a capsulectomy is the acutal removal of lens capsule tissue.)

Cataract operations are mostly performed under a local anaesthetic and the patient will be allowed to go home the same day. Complications after cataract surgery are uncommon. Many people (up to 50%) can develop a posterior capsular opacification after initial cataract surgery. This is a thickening and clouding of the lens capsule (which was left behind when the cataract was removed) and it can be easily corrected using a Nd-Yag laser to make holes in the capsule for the person to see through. Retinal detachment is an uncommon complication of cataract surgery.

Previously, polymethylmethacrylate was used as the lens material, since it was discovered by Sir Harold Ridley in UK. He observed that the Royal Airforce pilots sustained eye injuries with splinters of glass from fighter plane windshield (made of PMMA). However, the eyes did not show any foreign body reaction. Thus the material was inert and useful for implantation in the eye. Sir Harold Ridley was the first to design and implant Intraocular lenses, which were further refined by using lathe cutting machines. Advances in technology have brought about the use of silicone and acrylic both of which are soft foldable inert material. This allows the lens to be folded and inserted into the eye through a smaller incision. Polymethyl methacrylate (PMMA) and Acrylic lenses can also be used with small incisions and are a better choice in people who have a history of uveitis, have diabetic retinopathy requiring vitrectomy with replacement by silicone oil or are at high risk of retinal detachment. Acrylic is not always an ideal choice due to its added expense. Latest advances include IOLs with square-edge design, non-glare edge design and yellow dye added to the IOL.

Couching was an early form of cataract surgery in which a small probe was inserted in the eye to push the lens down into the posterior chamber.

[edit] History

The earliest references to cataract surgery are found in Sanskrit manuscripts dating from the 5th century BC, which show that Susruta in India developed specialised instruments and performed the earliest eye surgery. In the Western world, bronze instruments that could have been used for cataract surgery, have been found in excavations in Babylonia, Greece and Egypt. The first references to cataract and its treatment in the West are found in 29 AD in De Medicinae, the work of the Latin encyclopedist Aulus Cornelius Celsus.

In 1748, Jacques Daviel started with modern cataract surgery, in which the cataract is actually extracted from the eye. In the 1940s Harold Ridley invented the intraocular lens which made efficient and comfortable visual rehabilitation possible after cataract surgery.

According to surveys of members of the American Society of Cataract and Refractive Surgery, approximately 2.85 million cataracts procedures were performed in the United States during 2004 and 2.79 million in 2005[4].

[edit] See also

[edit] References

  1. ↑ Surgery Encyclopedia - Ophthalmologic surgery
  2. ↑ Uhr, Barry W. History of ophthalmology at Baylor University Medical Center. Proc (Bayl Univ Med Cent). 2003 October; 16(4): 435–438. PMID 16278761
  3. ↑ a b c Surgery Encyclopedia - Extracapsular cataract extraction
  4. ↑ Surgery Encyclopedia - Phacoemulsification for cataracts
  5. ↑ Surgery Encyclopedia - Cryotherapy for cataracts
  6. ↑ Meadow, Norman B. Cryotherapy: A fall from grace, but not a crash. Ophthalmology Times. October, 15, 2005.
  7. ↑ Surgery Encyclopedia - Laser posterior capsulotomy


[edit] Glaucoma surgery

Glaucoma is a group of diseases affecting the optic nerve that results in vision loss and is frequently characterized by raised intraocular pressure (IOP). There are many glaucoma surgeries, and variations or combinations of those surgeries, that facilitate the escape of excess aqueous humor from the eye to lower intraocular pressure, and a few that lower IOP by decreasing the production of aqueous.

[edit] Procedures that facilitate outflow of aqueous humor

Laser trabeculoplasty

A trabeculoplasty is a modification of the trabecular meshwork. Laser trabeculoplasty (LTP) is the application of a laser beam to burn areas of the trabecular meshwork, located near the base of the iris, to increase fluid outflow. LTP is used in the treatment of various open-angle glaucomas.[1] The two types of laser trabeculoplasty are argon laser trabeculoplasty (ALT) and selective laser trabeculoplasty (SLT). As its name suggests, argon laser trabeculoplasty uses an argon laser to create tiny burns on the trabecular meshwork.[2] Selective laser trabeculoplasty is newer technology that uses a Nd:YAG laser to target specific cells within the trabecular meshwork and create less thermal damage than ALT.[3][4]

Iridotomy

An iridotomy involves making puncture-like openings through the iris without the removal of iris tissue. Performed either with standard surgical instruments or a laser, it is typically used to decrease intraocular pressure in patients with angle-closure glaucoma. A laser peripheral iridotomy (LPI) is the application of a laser beam to selectively burn a hold through the iris near its base. LPI may be performed with either an argon laser or Nd:YAG laser.[5][6]

Iridectomy

An iridectomy, also known as a corectomy or surgical iridectomy, involves the removal of a portion of iris tissue.[7][8] A basal iridectomy is the removal of iris tissue from the far periphery, near the iris root; a peripheral iridectomy is the removal of iris tissue at the periphery; and a sector iridectomy is the removal of a wedge-shaped section of iris that extends from the pupil margin to the iris root, leaving a keyhole-shaped pupil.

Filtering procedures: penetrating vs. non-penetrating

Filtering surgeries are the mainstay of surgical treatment to control intraocular pressure.[9] An anterior sclerotomy or sclerostomy is used to gain access to the inner layers of the eye [5] [6] [7] in order to create a drainage channel from the anterior chamber to the external surface of the eye under the conjunctiva, allowing aqueous to seep into a bleb from which it is slowly absorbed. Filtering procedures are typically divided into either penetrating or non-penetrating types depending upon whether an intraoperative entry into the anterior chamber occurs [8] [9].

Penetrating filtering surgeries are further subdivided into guarded filtering procedures, also known as protected, subscleral, or partial thickness filtering procedures (in which the surgeon sutures a scleral flap over the sclerostomy site [10]), and full thickness procedures [11]. Trabeculectomy is a guarded filtering procedure that removes of part of the trabecular meshwork[10][12]. Full thickness procedures include sclerectomy, posterior lip sclerectomy (in which the surgeon completely excises the sclera on the area of the sclerostomy [13]), trephination, thermal sclerostomy (Scheie procedure), iridenclesis, and sclerostomy (including conventional sclerostomy and enzymatic sclerostomy) [14] [15].

Non-penetrating filtering surgeries do not penetrate or enter the eye's anterior chamber [16] [17]. There are two types of non-penetrating surgeris: Bleb-forming and viscocanalostomy [18] [19]. Bleb forming procedures include ab externo trabeculectomy and deep sclerectomy[20]. Ab externo trabeculectomy (AET) involves cutting from outside the eye inward to reach Schlemm's canal, the trabecular meshwork, and the anterior chamber. Also known as non-penetrating trabeculectomy (NPT), it is an ab externo (from the outside), major ocular procedure in which Schlemm's canal is surgically exposed by making a large and very deep scleral flap. The inner wall of Schlemm's canal is stripped off after surgically exposing the canal [21]. Deep sclerectomy, also known as nonpenetrating deep sclerectomy (PDS) or nonpenetrating trabeculectomy is a filtering surgery where the internal wall of Schlemm's canal is excised, allowing subconjunctival filtration without actually entering the anterior chamber [22]; it is commonly performed with the Aquaflow® collagen wick [23]. Viscocanalostomy is also an ab externo, major ocular procedure in which Schlemm's canal is surgically exposed by making a large and very deep scleral flap. In the VC procedure, Schlemm's canal is cannulated and viscoelastic substance injected (which dilates Schlemm's canal and the aqueous collector channels)[24].

Other surgical procedures

Goniotomy and trabeculotomy are similar simple and directed techniques of microsurgical dissection with mechanical disruption of the trabecular meshwork [25] [26] [27]. Gonotomy procedures include surgical goniotomy and laser goniotomy. A surgical goniotomy involves cutting the fibers of the trabecular meshwork to allow aqueous fluid to flow more freely from the eye [28][29].[11] Laser goniotomy is also known as goniophotoablation and laser trabecular ablation [30]. In many patients suffering from congenital glaucoma, the cornea is not clear enough to visualize the anterior chamber angle. Although an endoscopic goniotomy, which employs an endoscope to view the anterior chamber angle, may be performed [31], a trabeculotomy which accesses the angle from the exterior surface of the eye, thereby eliminating the need for a clear cornea, is usually preferred in these instances. A specially designed probe is used to tear through the trabecular meshwork to open it and allow fluid flow [32].Video

Tube-shunt surgery or drainage implant surgery involves the placement of a tube to facilitate aqueous outflow from the anterior chamber[12] [33][34]. Trabeculopuncture uses a Q switched Nd:YAG laser to punch small holes in the trabecular meshwork with [35][36] [37]. Goniocurretage is an "ab interno" (from the inside) procedure that used an instrument "to scrape pathologically altered trabecular meshwork off the scleral sulcus" [38][39] [40]. A surgical cyclodialysis is a rarely used procedure that aims to separate the ciliary body from the sclera to form a communication between the suprachoroidal space and the anterior chamber.[8] A cyclogoniotomy is a surgical procedure for producing a cyclodialysis, in which the ciliary body is cut from its attachment at the scleral spur under gonioscopic control.[8]

[edit] Procedures that decrease production of aqueous humor

Certain cells within the eye's ciliary body produce aqueous humor. A ciliary destructive or cyclodestructive procedure is one that aims to destroy those cells in order to reduce intraocular pressure [41]. Cyclocryotherapy, or cyclocryopexy, uses a freezing probe [42]. Cyclophotocoagulation, also known as transscleral cyclophotocoagulation, ciliary body ablation,[43], cyclophotoablation [44], and cyclophototherapy [45], uses a laser[13][46]. Cyclodiathermy uses heat generated from a high frequency alternating electric current passed through the tissue,[8] while cycloelectrolysis uses the chemical action caused by a low frequency direct current.[8]

[edit] Refractive surgery

Main article: Refractive surgery
  • Refractive surgery aims to correct errors of refraction in the eye, reducing or eliminating the need for corrective lenses
    • Keratomilleusis is method of reshaping the cornea surface to change its optical power. A disc of cornea is shaved off, quickly frozen, lathe-ground, then returned to its original power.
    • Automated lamellar keratoplasty (ALK)
    • Laser assisted in-situ keratomileusis (LASIK)[14]
    • Laser assisted sub-epithelial keratomileusis (LASEK), aka Epi-LASIK
    • Photorefractive keratectomy (PRK)[15]
    • Laser thermal keratoplasty (LTK)
    • Conductive keratoplasty (CK) uses radio frequency waves to shrink corneal collagen. It is used to treat mild to moderate hyperopia.[14]
    • Limbal relaxing incisions (LRI)
    • Astigmatic keratotomy (AK), aka Arcuate keratotomy or Transverse keratotomy
    • Radial keratotomy (RK)
    • Hexagonal keratotomy (HK)
    • Epikeratophakia is the removal of the corneal epithelium and replacement with a lathe cut corneal button.[16]
    • Intracorneal rings (ICRs), or corneal ring segments (Intacs) [47]
    • Implantable contact lenses
  • Presbyopia reversal
    • Anterior ciliary sclerotomy (ACS)
      • Laser reversal of presbyopia (LRP)
    • Scleral expansion bands

[edit] Corneal surgery

[edit] Vitreo-retinal surgery

Vitrectomy.
  • Vitreo-retinal surgery includes the following
    • Vitrectomy [48]
      • Anterior vitrectomy is the removal of the front portio of vitreous tissue. It is used for preventing or treating vitreous loss during cataract or corneal surgery, or to remove misplaced vitreous in conditions such as aphakia pupillary block glaucoma.
      • Pars plana vitrectomy (PPV), or trans pars plana vitrectomy (TPPV), is a procedure to remove vitreous opacities and membranes through a pars plana incision. It is frequently combined with other intraocular procedures for the treatment of giant retinal tears, tractional retinal detachments, and posterior vitreous detachments [49].
    • Pan retinal photocoagulation (PRP) is a type of photocoagulation therapy used in the treatment of diabetic retinopathy.[19]
    • Retinal detachment repair
      • Ignipuncture is an obsolete procedure that involves cauterization of the retina with a very hot pointed instrument.[20]
      • A scleral buckle is used in the repair of a retinal detachment to indent or "buckle" the sclera inward, usually by sewing a piece of preserved sclera or silicone rubber to its surface.[21]
      • Laser photocoagulation, or photocoagulation therapy, is the use of a laser to seal a retinal tear.[19]
      • Pneumatic retinopexy
      • Retinal cryopexy, or retinal cryotherapy, is a procedure that uses intense cold to induce a chorioretinal scar and to destroy retinal or choroidal tissue.[22]
    • Macular hole repair
    • Partial lamellar sclerouvectomy[23]
      • Partial lamellar sclerocyclochoroidectomy
      • Partial lamellar sclerochoroidectomy
    • Posterior sclerotomy is an opening made into the vitreous through the sclera, as for detached retina or the removal of a foreign body [50].
  • Radial optic neurotomy

macular translocation surgery

 through 360 degree retinotomy
 through scleral imbrication technique

[edit] Eye muscle surgery

With approximately 1.2 million procedures each year, extraocular muscle surgery is the third most common eye surgery in the United States [51].

  • Eye muscle surgeries typically correct strabismus and include the following[24] [52]:
    • Loosening / weakening procedures
      • Recession involves moving the insertion of a muscle posteriorly towards its origin.
      • Myectomy
      • Myotomy
      • Tenectomy
      • Tenotomy
    • Tightening / strengthening procedures
      • Resection
      • Tucking
      • Advancement is the movement of an eye muscle from its original place of attachment on the eyeball to a more forward position.
    • Transposition / repositioning procedures
    • Adjustable suture surgery is a method of reattaching an extraocular muscle by means of a stitch that can be shortened or lengthened within the first post-operative day, to obtain better ocular alignment [53].

[edit] Oculoplastic surgery

[edit] Other

  • A ciliarotomy is a surgical division of the ciliary zone in the treatment of glaucoma.[8]
  • A ciliectomy is 1) the surgical removal of part of the ciliary body, or 2) the surgical removal of part of a margin of an eyelid containing the roots of the eyelashes.[8]
  • A ciliotomy is a surgical section of the ciliary nerves.[8]
  • A corectomedialysis, or coretomedialysis, is an excision of a small portion of the iris at its junction with the ciliary body to form a artificial pupil.[8]
  • A corectomy is any surgical cutting operation on the iris at the pupil.[8]
  • A corelysis is a surgical detachment of adhesions of the iris to the capsule of the crystalline lens or cornea.[8]
  • A coremorphosis is the surgical formation of an artificial pupil.[8]
  • A coreplasty, or coreoplasty, is plastic surgery of the iris, usually for the formation of an artificial pupil.[8]
  • A coreoplasy, or laser pupillomydriasis, is any procedure that changes the size or shape of the pupil.[29]
  • A cyclectomy is an excision of portion of the ciliary body.[8]
  • A cyclotomy, or cyclicotomy, is a surgical incision of the ciliary body, usually for the relief of glaucoma.[8]
  • A cycloanemization is a surgical obliteration of the long ciliary arteries in the treatment of glaucoma.[8]
  • An iridectomesodialsys is the formation of an artificial pupil by detaching and excising a portion of the iris at its periphery.[8]
  • An iridodialysis, sometimes known as a coredialysis, is a localized separation or tearing away of the iris from its attachment to the ciliary body.[8][29]
  • An iridencleisis, or corenclisis, is a surgical procedure for glaucoma in which a portion of the iris is incised and incarcerated in a limbal incision.[8] (Subdivided into basal iridencleisis and total iridencleisis.[30])
  • An iridesis is a surgical procedure in which a portion of the iris is brought through and incarcerated in a corneal incision in order to reposition the pupil.[8][57]
  • An iridocorneosclerectomy is the surgical removal of a portion of the iris, the cornea, and the sclera.[8]
  • An iridocyclectomy is the surgical removal of the iris and the ciliary body.[8]
  • An iridocystectomy is the surgical removal of a portion of the iris to form an artificial pupil.[8]
  • An iridosclerectomy is the surgical removal of a portion of the sclera and a portion of the iris in the region of the limbus for the treatment of glaucoma.[8]
  • An iridosclerotomy is the surgical puncture of the sclera and the margin of the iris for the treatment of glaucoma.[8]
  • A trepanotrabeculectomy is used in the treatment of chronic open and chronic closed angle glaucoma.[30]

[edit] References

  1. ↑ University of Michigan Health System - Surgery for Glaucoma
  2. ↑ EyeMDLink.com - Argon Laser Trabeculoplasty (ALT)
  3. ↑ Review of Optometry - SLT: The Laser Picks Up Where Medications Leave Off
  4. ↑ Glaucoma Research Foundation - SLT: A New Type of Glaucoma Surgery
  5. ↑ Surgery Encyclopedia - Laser iridotomy
  6. ↑ EyeMDLink.com - Laser Peripheral Iridotomy (PI)
  7. ↑ Surgery Encyclopedia - Iridectomy
  8. ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z aa Cline D; Hofstetter HW; Griffin JR. Dictionary of Visual Science. 4th ed. Butterworth-Heinemann, Boston 1997. ISBN 0-7506-9895-0
  9. ↑ Jacobi PC, Dietlein TS, Krieglstein GK. "Technique of goniocurettage: a potential treatment for advanced chronic open angle glaucoma." Br J Ophthalmol. 1997 Apr;81(4):302-7. PMID 9215060.
  10. ↑ Surgery Encyclopedia - Trabeculectomy
  11. ↑ Surgery Encyclopedia - Goniotomy
  12. ↑ Surgery Encyclopedia - Tube-shunt surgery
  13. ↑ EyeMDLink.com - Cyclophotocoagulation
  14. ↑ a b Surgery Encyclopedia - LASIK
  15. ↑ Surgery Encyclopedia - PRK
  16. ↑ a b Surgery Encyclopedia - Corneal transplantation
  17. ↑ Indiana University Department of Ophthalmology - Phototherapeutic Keratectomy (PTK)
  18. ↑ MDAdvice.com - Pterygium removal
  19. ↑ a b Surgery Encyclopedia - Photocoagulation therapy
  20. ↑ Wolfensberger TJ. "Jules Gonin. Pioneer of retinal detachment surgery." Indian J Ophthalmol. 2003 Dec;51(4):303-8. PMID 14750617.
  21. ↑ Surgery Encyclopedia - Scleral Buckling
  22. ↑ Surgery Encyclopedia - Retinal_cryopexy
  23. ↑ Shields JA, Shields CL. Surgical approach to lamellar sclerouvectomy for posterior uveal melanomas: the 1986 Schoenberg lecture. Ophthalmic Surg. 1988 Nov;19(11):774-80. PMID 3222038.
  24. ↑ Surgery Encyclopedia - Eye Muscle Surgery
  25. ↑ Surgery Encyclopedia - Blepharoplasty
  26. ↑ Cherkunov BF, Lapshina AV. ["Canaliculodacryocystostomy in obstruction of medial end of the lacrimal duct."] Oftalmol Zh. 1976;31(7):544-8. PMID 1012635.
  27. ↑ Surgery Encyclopedia - Enucleation
  28. ↑ Surgery Encyclopedia - Exenteration
  29. ↑ a b Cassin, B. and Solomon, S. Dictionary of Eye Terminology. Gainsville, Florida: Triad Publishing Company, 1990.
  30. ↑ a b Cvetkovic D, Blagojevic M, Dodic V. ["Comparative results of trepanotrabeculectomy and iridencleisis in primary glaucoma."] J Fr Ophtalmol. 1979 Feb;2(2):103-7. PMID 444110.

[edit] External links

Retrieved from "http://en.wikibooks.org/wiki/Ophthalmology"