Retinal Detachment can cause blindness

This article has been designed for educated lay public. It will also be useful to qualified doctors, ophthalmologist and even health care professionals in communicating with patients or potential patients of Retinal Detachment.

Retina is to the eye what the film is to the camera - only more complex. The points of similarity between a human eye and a camera are many.

The photographic film is held stretched on the back of a camera, a light tight box, to receive the image focused on it by the lens system of the camera. The retina is similarly placed at the back of an eye to receive images focused by the lens system of the eye. While the photographic film is meant to retain a single image permanently, the retina receives and transmits to the brain successive images as the eye looks on, somewhat similar to a television camera. The aperture of the camera diaphragm has to be manually adjusted to permit only certain quantity of light into the camera to give a good photograph on a particular film.

The aperture(pupil) in the iris(diaphragm) of the eye is automatically adjusted, similar to certain automatic cameras available. Similarly, while focusing is done in most cameras by the photographer, the focusing of the eye is automatic through certain changes in human lens. In order to prevent scattering of the light inside the camera, which could fog the film and give a hazy photograph, the inside of the camera is covered with absorbent black paint. For precisely similar reason, just outside the retina, the eye has been provided with dark pigment in the pigmented epithelium and choroid. Unlike a photographic film, the retina is a living tissue requiring a huge quantity of nutrition(fuel) and oxygen for it’s survival and function.

The most sensitive and complex outer portion of the retina has no blood vessels to supply it with oxygen or nutrition directly. For these, the retina has to depend on the choroid which is highly vascular (with plenty of blood vessels) for the sole purpose of feeding the retina.

For the retina to be able to use the nutrients, it must remain in ‘position’ - in close proximity with the pigmented epithelium and the choroid. Under certain circumstances discussed below, the retina gets detached from the pigmented epithelium and the choroid: the condition is known as detachment of retina.

Anatomically there is no definite attachment between the retina and the pigmented epithelium, the correct expression should have been separation of retina rather than detachment of retina. Immediately following the detachment, the retina fails to receive or transmit an image with any amount of clarity. When the detachment is partial involving a part of the retina, the corresponding part of field of vision(the area visible) is lost.

When the central(macula) - the area of the retina used for seeing things we ‘look at’, things we wish to see - is detached, the result is catastrophic. As the retina gets lifted up, it relapses into wrinkles and folds. The patient sees things wavy, tilted and distorted before total loss of vision. Only a strong source of light or a bright object can be seen.

When the retina is totally detached, all vision is lost. If the retina can be attached quickly, most of the vision can be recovered. However if the retina remains detached from the choroid, i.e. away from it’s source of nutrition and oxygen, it’s outer layers containing the important visual elements slowly die and degenerate. The retina could be dead completely but for the fact that it’s inner layers have their own vascular supply which can delay death but can not save it. The result is total and permanent blindness. Therefore the longer the retina remains detached, the greater is the degeneration and lesser the chance of visual recovery.

Causes of Retinal Tears

Tears or holes in the retina do not develop in normal, healthy eyes except when the retina is directly pierced, as in perforating injuries of the eye or when the retina is stretched beyond endurance following terrible blows to the eye, as amongst boxers.

Degeneration of the retina resulting in its weakening, degeneration of the vitreous resulting in its partial collapse and adhesion of the degenerated vitreous to the retina are some of the most important factors which predispose the eye to the development of retinal breaks.

Actual breaks could develop if individuals with such eyes receive a jolt or jerk or are subjected to sudden acceleration or deceleration while travelling in a vehicle on a rough road, or in a car which speeds up too fast and is suddenly brought to a halt. Even a bump on the head, a fall in a slippery bathroom, or a massage by an enthusiastic barber could precipitate retinal tears.

The degeneration of the retina and the vitreous is determined by a genetic abnormality. Such an abnormal gene is closely related to another abnormal gene which causes short sightedness (myopia). Therefore, most cases ofd vitreo-retinal degeneration (VRD) are to be seen among the myopes - specially the progressive types(patients needing rapid change of glasses) and high myopes. However, such degeneration is also possible in people with normal eye sight. These are often members of a myopic family carrying the gene of VRD but not of myopia.

Besides myopia, old age and certain ocular inflammations (chorioretinitis) are the common causes for vitreo retinal pathology. If a cataract develops in such an individual, an operation is done to remove the lens. This causes the vitreous to shift forwards. In a bad operation the vitreous flows out of the eye during the cataract operation producing a pull on the retina, and chances of development of retinal tears increase. In an analysis and get stuck at the wound, of cases of retinal tears registered at the Retina Care Unit of the Department of Ophthalmology, Maulana Azad Medical College, myopia accounted for 68%, cataract operations(aphakia) for 16% of the cases and trauma accounted for 6%. With an anticipated increase in number of cataract operations in the coming years, aphakia may become the most important cause of retinal detachment in India. Specially if the quacks and the old fashioned surgeons, who are extremely casual about vitreous loss and disturbance, are encouraged and glorified about their instant surgery, blindness due to retinal detachment will be on the increase. Fortunately, modern technique of extracapsular cataract surgery , where back portion of the capsule of the lens is left in place , does not encourage Vitreous disturbances as much as the Intracapsular techniques of the past, where the entire lens along with it’s capsule used to be removed.

Vitreous in the Mechanism of development of Retinal tears

Vitreous is a transparent jelly like tissue filling the space bounded by lens in front and retina behind. Normally it has no firm attachment to the retina it supports except at its base. The vitreous consists of molecules of hyaluronic acid, swollen with water(hydrated), suspended in a meshwork of collagen fibers. In a healthy state their arrangement is compact and looks like a soft transparent jelly.

When the vitreous undergoes degeneration, the fat hyaluronic acid molecules dissolve to form pockets of fluid. The collagen network collapses and the vitreous shrinks. A sudden movement of the vitreous cavity of the eye would produce differential movement of the collapsed vitreous in relation to the tunics of the eye including the retina. If the vitreous has any abnormal adhesions to the retina, it would produce a tear.

Tears by themselves do not lead to detachment. When fluid vitreous exists close to the tear, it flows through the tear to lift the retina and accumulates behind it starting detachment. As more fluid accumulates lifting more of retina, the detachment spreads. In due course detachment becomes total. There is usually a considerable time difference between development of a retinal break and onset of retinal detachment.

If during this time interval retinal tear is detected, it can be sealed without an operation by focussing strong light(photocoagulation) around it or by freezing it(cryopexy). Also dangerously degenerated areas of the retina which could break down to cause retinal breaks can similarly be treated to forestall a detachment. This is the basis of a system for prevention of a retinal detachment through prophylactic(preventive) therapy.

Cause of retinal detachment

The cause of spontaneous or primary retinal detachment was shrouded in mystery until Jules Gonin(1870-1935), the great Swiss ophthalmologist, at the beginning of this century made a well reasoned observation. It laid the foundation of modern detachment surgery. He noticed that often ophthalmologists recorded a tear or a hole in the retina in cases of retinal detachment without assigning any significance to it. In his view, if retinal holes are the cause of retina detachment, every case of detachment must have a tear. He began re-examining all cases of retinal detachment where no holes had been detected. Many of the cases re-examined revealed retinal holes. He concluded that retinal hole or a break is the cause of primary retinal detachment.

Treatment of Retinal Detachments

A surgical operation is the only treatment for retinal detachment. This involves essentially four steps:

(1) Exposure of the back of the eye globe by cutting through the thin membrane, conjunctiva, which covers the front half of the globe and then continues to cover the back of the eyelids

(2) Producing a choroidal reaction (a sticky surface) under the retinal tear so that retina around the tear could stick to the underlying choroid ultimately forming a firm chorio-retinal adhesion.

(3) producing a scleral buckle(bulge) which pushes the choroid with the sticky surface towards the retina with the tear and

(4) removing the fluid which had accumulated between the retinal and the pigmented epithelium and choroid so that that the retina can settle on the sticky choroid - made easier by the buckle.

The details of the steps are given below:

Exposing the back of the eye globe

The lids are kept open by ‘retractors’ or ‘speculum’. The conjunctiva is cut close to the cornea and lifted up to expose the outer coat of the eye ball sclera and the eye muscles attached to it.

Producing a Choroidal Reaction

Choroid is like a carpet of blood vessels where the soft surface is innermost and is close to the retina. It consists of loop and masses of fine thin walled blood vessels(capillaries). When damaged, these capillaries leak a sticky fluid (exudates) on to which the retina with the tear can stick. The choroid capillaries can be carefully damaged using heating or freezing. Heat can be produced to damage the choroid capillaries by two methods.

Diathermy A diathermy applicator(electrode) is positioned on the sclera outside the globe, and a high frequency (13.56Mhz) low voltage current is passed. Heat is produced as the high frequency current labours through the resistance offered by the body tissue as a semi conductor. The process is known as diathermy coagulation. By careful regulation of the current made to flow through the sclera and choroid an appropriate reaction can be produced. Diathermy is one of the oldest and surest methods to produce choroidal reaction. Yet, it has the disadvantage of damaging the sclera which becomes weak, and heating the vitreous could shrink it further. With minimal use of diathermy, these disadvantages can be minimised.

Photocoagulation

The other method of damaging the choroid capillaries by heat is to focus a very strong light through the pupil on to the pigments of the epithelium (a single layer of heavily pigmented cells lying between the choroid and the retina) and the choroid. The focused strong light energy gets concentrated on the dark pigment, which absorbs it to produce intense local heat, damaging the choroidal capillaries in the vicinity.

The process is known as photocoagulation and is similar to the way children burn paper by focussing sun rays by means of a thick convex lens. The cornea and the lens act as the focusing system and a strong artificial source such as xenon arc or a laser system replaces the sun as the source of the light energy. However, photocoagulation is not effective in the presence of a detached retina. Therefore, it is usually used to seal a tear and prevent detachment. Photocoagulation is rarely used as a part of surgery of retinal detachments.

Cryopexy

The choroid capillaries can also be damaged by freezing. Ice crystals are formed inside the cells lining the capillaries. When water (cell content is 98% water) turns into ice it expands in volume and breaks the cell wall. The capillaries produce an exudate as in diathermy and photocoagulation. The freezing is done by the cryopencil applied on to the surface of the globe.The tip temparature of the cryoprobe is lowered to as low as -70oC. The tissue in contact cools rapidly and ultimately gets frozen.

This method and has many advantages. Unlike diathermy, the freezing does not damage the sclera or the vitreous. It can even be used through the conjunctiva without damaging it’s structure.

Scleral Buckles are produced by burying a material (an implant) of suitable size and shape in the layers of the sclera (intra-scleral buckle) or by suturing the implant on the surface of the sclera (episceral buckle). When a more prominent and permanent buckle is desired, an encircling band or string is passed all round the globe over the implants and is tightened to contract the globe all round.

Various materials have been used as implants. Silicon rubber or sponge is the most popular among non-absorbable materials.

Removal of the subretinal fluid If a patient with retinal detachment is made to lie down flat on his back with both eyes bandaged, there is a good chance that the subretinal fluid will disappear resulting in a reattachment of the retina. The vision will improve. Infact before Gonin, patients were kept on their back for years. However, if the retinal tears are not closed, the retinal detachment is sure to recur as soon as the patient moves about. Occasionally, when the retina settles completely on bed rest, the retinal tears can be sealed by photocoagulation alone and surgery becomes unnecessary.

In the majority, however, the sub-retinal fluid has to be drained out during the surgical operation. A tiny is cut made on the sclera to expose the choroid. It is then punctured with a finely pointed instrument to drain the sub retinal fluid. Alternatively, the sclera and the choroid are perforated by a needle connected to the diathermy (+ve) or catholysis (-ve) current. The procedure of draining the fluid could be risky. There is yet another technique where a choroidal reaction is produced by diathermy or cryopexy over the retinal tears, scleral buckles are produced, but no attempt is made to drain the subretinal fluid. In a few days the subretinal fluid disappears and the retina settles.

All these procedures are carried out, outside the globe (An out side job). It is possible to reattach retina from inside the eye by a recent technique known as Vitreous surgery ( An inside job) many difficult cases are now days operated with this technique.

Routine use of indirect opthalmoscope (an instrument to visualise the retina) during preoperative examination and during operation is the perhaps the most important single factor in success of detachment surgery. For instance, the success rate in detachment operations at he Irwin Hospital before 1969 was less than 25%.Opthalmic surgeons with no special training used direct ophthalmoscopes - completely inadequate instruments for retinal work.. However, since then, the routine use of indirect ophthalmoscope by the retina surgeons of the Retina Care unit of Irwin Hospital has resulted in a success rate of over 75% by 1975. With improved operation theater conditions and availability of special materials for operation, the success rate has improved even further. Today the success rate of standard retinal detachment surgery is as high as 95%. The complicated cases with special problems or those cases failed by standard techniques can now be treated with Vitreo Retinal Surgical techniques. ( See Pars Plana Vitreous Surgery Techniques).

That the eye surgeons trained in old English Schools are usually poor retina surgeons is just being recognised at a terrible cost to the detachment patients in India. Unfortunately, there are only a handful of ophthalmic centers in India which are equipped for retinal work. What is even more unfortunate is that even in those few centers, there are not enough retina specialists. There are a few ophthalmic surgeons in private practice in the large cities who have taken to retinal surgery in right earnest. They are a welcome addition to the extremely small group of retina specialists working in public institutions.

While lack of trained retina surgeons is the most pressing problems before the country today, there are the following factors which must be attended to:

Popularisation of indirect ophthalmoscopes among post graduate students of ophthamology.

Indigenous manufacture of such basic equipment as diathermy machines, cryo units, indirect ophthalmoscopes and later photocoagulators and vitreous-surgery equipment.

The age old adage 'Prevention is better than cure' is perhaps nowhere more appropriate than in retinal detachment. The cure of retinal detachment involves a very delicate, time consuming operation. It is true that the prospects (prognosis) of success have increased to about 95% today. Yet, even the most delicate of surgeries can not restore 100% of the vision. The moment the retina is detached, it wrinkles. Even if it is reattached immediately, the retina fails to assume the same perfect smoothness it had before the detachment. The result: everything looks a little wavy - the sharpness of vision is lost forever. The greater the delay in treatment the greater is the loss of visual perfection. Also the process of surgical treatment of retinal detachment involves scarring of the areas of the retina with inevitable loss of it's function. The most successful techniques in reattaching the detached retina are also somewhat drastic. While such techniques preserve the most important central vision, to some extent the peripheral vision is sacrificed. Therefore it should be obvious that the ideal solution is to prevent a retinal detachment rather than trying to cue it after it has detached.

Is it really possible to prevent a retinal detachment? The answer is yes. Retinal detachment is not a disease which could afflict just anyone. The vast majority are myopics (short sighted) wearing thick glasses (high myopics) or members of the family of myopes. The other important groups are those who have got their cataract operations done, and those who have been hit and have injuries of the eye. A comparatively small percentage of these patients would develop weakness (degeneration) of the retina to which the degenerated vitreous will be attached. Some day retinal tears would form. After the tears are formed it takes months, even years, but rarely days before a retinal detachment develops. As such it is not really a sudden accident as it appears.

As long as the retina is not detached, the retinal degeneration and even retinal tears can be successfully treated without surgical operations. In other words, if a patient predisposed to develop retinal detachment with retinal degeneration and holes happens to come across a trained retinal surgeon who on a thorough retinal examination detects these lesions and completes what is known as prophylactic (preventive) treatment, there is no reason why the patient should develop retinal detachment. It is possible that after the first treatment patient may develop some more of retinal detachment or retinal holes. This only means that such an individual must continue to get himself examined at regular intervals as an insurance against retinal detachment.

People who are prone to develop retinal detachment (target population) belong to the following categories :

(a) Myopics (short sighted), especially the high myopes (using glasses of -4D or more) and rapidly progressive myopes (those who have to change their spectacles frequently) constitute the largest group.(68%)

(b) Aphakics - those who have been operated upon for cataract are the next important group (16%)

(c) Those who had sustained injury to the eye. (6%)

The majority of the cases of retinal detachment that we see in this country are between the age groups 30 to 60 years; of which people between 40-50 years account for 42% of all cases of retinal detachment. Retinal Detachment is much more common in males than in females. Greater outdoor and physical activity among Indian males seems to be the most important cause for this difference.

The least these people could do for themselves is get the retina thoroughly examined by a competent retina specialist. The modern retina specialist use with skill such examination systems such as indirect ophthalmoscopes and Goldmann's 3 mirror contact glass, developed over years of painstaking research.Out of these procedures, one that is most useful and the most difficult to master, is the indirect ophthalmoscope. Unfortunately, the vast majority of ophthalmologists trained in this country or in Great Britain are poorly trained in the use of this technique. Most of them who hear about it's usefulness go as far as acquiring the instrument. The process of mastering the technique is too time consuming and requires hours of back breaking practice. Few find the time or inclination to do so. As a result there are surprisingly few competent retina surgeons in the country today. However, the younger generation among the ophthalmologists seems to be getting the message. The number of retina surgeons is likely to increase slowly. It is almost totally useless for the purpose of prevention of retinal detachment to consult ophthalmologists who are not retina specialists.

To start with, a detailed mapping of the fundus (inside of the eye) is carried out on a special chart. Depending on the nature, the side, and the extent of the retinal pathology, patients are categorised into different risk groups. The high risk groups with imminent retinal detachment are treated for it's prevention (prophylactic treatment). The weak areas of the retina and those with tears are treated with cryopexy (freezing) or photocoagulation, so that the retina surrounding the weak areas or the tears are stuck to the underlying choroid by a scar. The procedures of cryopexy and photocoagulation do not need a surgical operation. However, once a retinal detachment develops, it can be treated only through an operation.

The degeneration of tears (doctors call them lesions) do not develop all at once. It is possible that new lesions continue to develop over a period of time. This would necessarily mean that such patients get themselves examined by a retina surgeon at regular intervals. Retinal tears or degenerations are taken care of as soon as they threaten to develop into retinal detachment. To give an example: there is one patient in our records who developed tears, dangerous ones, on five successive occassions. Each time they were detected before a detachment developed and treated to make them safe. The system of constant watch and preventive treatment has saved him from detachment five times. In course of time, all sites of vitreous pull reveal themselves in the form of retinal tears or retinal degenerations and are treated to make them sake. Thereafter, no new retinal tears should develop.

Warning Premonitary Symptoms

There are certain symptoms which, to the patients of the susceptible group, may mean serious trouble.

(1) When a degenerated vitreous shrinks, a time comes when it gets detached from the back of the eye and collapses forward to crowd behind the lens. While a normal vitreous is transparent and is not visible to the retina, the collapsed vitreous may be seen as multiple, translucent dots dispersed irregularly or in form of chains of various forms. The chains turn or twist with the movement of the eye.

(2) When a vitreous pulling on the retina causes a retinal tear, often the retinal blood vessels passing across the tear snap and bleed into the vitreous. When the bleeding is small, the patient suddenly sees dark spots which gradually disperse, and may disperse with or without treatment. More extensive haemorrhages appear as a mist or a cloud. A massive haemorrhage may obscure vision for variable periods. The wise thing to do in such a case is to take complete bed rest and contact a retina surgeon for a thorough fundus examination to discover the cause of vitreous haemorrhage. If someone is a myope or an aphakic (already operated for cataract) and is not a diabetic and does not suffer from what doctors call Eale’s disease, he has almost certainly bled from a retinal tear. Unfortunately, most of the patients, even the majority of examining doctors and eye specialists, do not appreciate the significance of this sign. As a result, a retinal break which could have been succesfully treated without a surgical operation by photo-coagulation or cryopexy goes on to cause a retinal detachment.

(3) Pull on the retina causes a sensation of light. It may be in the form of tiny twinkling lights or large soft glows moving away painlessly and silently. They are know as photopsae. If they appear suddenly, an immediate investigation is required.

(4) A beginning of retinal detachment can be perceived as a dark veil or shadow appearing and enlarging. As the detached retina moves and shifts, it gives a sensation of soft glows of light moving and breaking up as they move to disappear.

Anyone who is susceptible to develop retinal tears and detachments must consult a retinal specialist the moment he experiences symptoms similar to the ones listed above.

It may be of interest to illustrate a point with a case note. Mr. G, 48, male was a high myope. He was examined at the Retinal Detachment Clinic of Irwin Hospital and was found to have got dangerous looking retinal degeneration. He was asked to avoid jerky vehicles, accident at falls etc. He was also suitably educated on the warning signs indicating dangerous happenings in the retina and kept under close observation for deciding on a preventive treatment. A fortnight later his nephew acquired a new scooter and invited our friend for a joy ride. Mr. G. forgot our warning against such adventures. While the scooter jumped along a bumpy road, two large tears formed in his left eye. A blood vessel passing over the tears got torn. Mr. G. saw all the significant dark spots in front of his eye. He came to us and was operated upon with the use of cryopencils in both eyes. He was thus saved from an imminent retinal detachment in the left eye. The areas of retinal degeneration in the right eye were made safe. Though the risk of retinal detachment was drastically reduced by preventive therapy, he was by no means completely out of danger from new retinal tears. Two months later, during one of his follow up examinations he showed a newly developed giant tear. This was promptly taken care of by us.