Retina

Q. What is “retina”?
A. This is the light sensitive layer of the eye, which behaves somewhat like the film of a camera. It lines the inner surface of the back of the eye and is made up in turn of several layers. Each cell of the innermost layer contributes a nerve fibre- millions of these nerve fibres join together to form the optic nerve or nerve of vision.

Q. How do we see?
A. The front of the eye, chiefly the cornea and the lens of the eye focus the rays of light from any object onto the retina. Here the light energy is converted by means of chemical reactions into electrical energy, which is transmitted by the optic nerve to the back of the brain. This signal, coming from both eyes, is interpreted by the brain resulting in the perception by us of the object we were looking at. In other words, the 2 eyes function like 2 TV cameras at a cricket stadium, with the brain acting as a master control room which fuses the 2 pictures sent by the 2 cameras into one enabling us to not only see a single image, but also to perceive depth.

Q. I sometimes get pain at the back of my eyes. Is this due to some retinal problem?
A. No. The retina has no pain sensations. Whenever it is inflamed or stimulated it responds by giving you the sensation of a flash of light. Hence pain in the back of the eye is usually due to non-ocular causes such as sinusitis or some forms of migraine or tension headaches.

Q. I occasionally see flashes of light and sometimes some floating particles as well. Is this dangerous?
A. Usually these are harmless. In adults above the age of 50 years, the jelly in front of the retina called the vitreous or vitreous humour can detach from its attachment to the retina. While this is happening, there may be occasional flashes of light. Also, around this age and later, part of this jelly liquefies. In this liquefied part of the jelly, some of your own cells may float. When these float into your field of vision, you see them as black spots or ‘floaters’. When they float out of your field of vision they may disappear from view. Sometimes, these may link up to form ‘lines’ or ‘cobwebs’. If they do not increase in size or number, they can be ignored. However, if there is a sudden increase in size or number of black spots or persistent flashes of light or if you are diabetic (see chapter on diabetes and the eye) or hypertensive or short-sighted, it is better to consult your eye surgeon. He will dilate your pupils and examine the retina with an instrument called an ‘ophthalmoscope’ to rule out any serious cause for your symptoms.

Q. You are scaring me doc, what do you mean by ‘serious cause’ for flashes of light or floaters?
A. Both these symptoms could indicate an early retinal tear or even a retinal detachment or haemorrhage either in the retina or the space in front called ‘vitreous haemorrhage’. As these are more common in diabetics, hypertensives and short sighted people (those with minus numbered spectacles) and patients with bleeding disorders, I mentioned them specifically. Patients with these diseases in any case should be visiting their eye surgeon for a retinal checkup at least once a year or more often as advised by their eye surgeon.

Q. Don’t just fling words at me like that. What do you mean by retinal tear or detachment?
A.Short sighted persons generally speaking have slightly larger eyes. Hence the inner lining of the eyeball, called the retina also needs to be of larger size. Unfortunately, the Creator only makes them in a single size. This is like asking a fat (sorry, I meant horizontally challenged) person to wear the same shirt as a thin (is he also horizontally challenged?) person. The shirt is naturally put to a stretch and over the course of time may get frayed or even tear at some weak area. This is what happens to shortsighted persons. The retina, which is under stretch, may give way at some peripheral area. This is known as a retinal tear. If there is a blood vessel running just under the area which is tearing, the blood vessel may tear too, causing leakage of blood or haemorrhage, under the retina or through the tear, into the jelly of the eye (vitreous haemorrhage). In the initial stage, these floating blood cells or clots are seen as floaters. When more such bleeding occurs, it may obscure vision as well.
If the tear is not immediately detected and sealed, blood or fluid may seep through the tear and go under the retina, lifting it off from its attachment to the underlying layer. This is known as a retinal detachment.

Q. How will I know that I may have a retinal detachment?
A. I thought I already answered that question. However, in brief, if you develop
a) sudden and persistent increase in number of black spots in front of your eyes
b) sudden and persistent increase in flashes of light or decreasing duration between flashes or
c) sudden drop in quality or quantity of vision or cutout of a particular field of vision, you are justified in getting alarmed and should immediately rush to an eye surgeon.

Q. Why the urgency, doc? Can I not wait for a couple of weeks or months – maybe the symptoms are due to stress or maybe things will improve over time?
A. No, retinal detachment is an emergency. The earlier it is examined by an eye surgeon and operated upon, the better the prognosis (likelihood of success). If the surgery is delayed beyond a time, in some cases the detached retina develops ‘fixed folds’ – like a cheap shirt which develops fixed creases if kept crumpled for a long time. These make the retinal detachment surgery more difficult and time consuming. It may also then involve additional procedures such as vitrectomy – the removal of the jelly of the eye in front of the retina and replacing it with some heavy gases or silicon oil which serve to iron out those retinal creases or fixed folds from the inside. In spite of these complex procedures, the retina may not settle in some cases. Also, the longer the retina is left detached, the lesser the chances of a full visual recovery, even if anatomically the retina is successfully re-attached after the surgery!

Q. It is easy for you to say “rush to the eye surgeon”. Retinal detachment surgery must be pretty expensive. Should I not arrange for finance first before |I seek an appointment?
A. No. First take an emergency appointment with the eye surgeon and let him confirm the diagnosis. He will then discuss with you the surgical options and give you an estimate of the charges and how long you can safely wait before the surgery. In case he is not doing the surgery himself he may refer you to a retina specialist. At that point you can discuss your budget with him. Excellent retinal surgery is done at several trust and charitable hospitals as well, which will be well within your budget. Do not let fear of raising funds prevent you from an initial consultation.

Q. What are the chances of success?
A. In a fresh detachment (one which is detected early) where the macula (the central light sensitive area of the retina) is not yet detached, the chances of anatomical success are close to 90%. The ‘older’ the detachment, the more the fixed folds, the higher the chances that the macula is also detached, the lesser the chances for success. Each case is different –you should discuss the chances of success with your eye surgeon before the surgery.

Q. What exactly is done in retinal detachment surgery?
A. First, the hole or tear in the retina responsible for the detachment is sealed either with use of a laser beam directed through the pupil or the use of a cryoprobe. The latter is a pencil like instrument applied to the sclera or white outer coat of the eye just over the hole in the retina. This probe generates a very low temperature of minus 40-70degrees centigrade. This causes the formation of a temporary ice ball, which seals the hole or tear. After this the sclera is pushed towards the detached retina by placing rigid or soft silicon explants (like pieces of a tyre), encouraging the retina to come so close to its underlying coat that it will stick there permanently.

Q. When is vitrectomy indicated?
A. This is indicated in the following conditions:
a) If the retina does not settle after the first surgery, it indicates there may be some traction or ‘pull’ from the vitreous that is causing it to stay detached.
b) If the retinal detachment is accompanied by a vitreous haemorrhage, sufficient to prevent the surgeon from getting a good view of the retina
c) If the surgeon sees traction bands in the vitreous which are responsible for the detachment. This is especially true in diabetics who get a retinal detachment as a complication of their diabetic retinopathy.
d) In case the patient has an advanced cataract along with the retinal detachment. The surgeon may then decide to remove the cataract as well as the vitreous to facilitate a better view of the retina.
e) In cases where the patient already has had a cataract surgery some time ago and has a thick ‘after cataract’ or thickening of the capsule at the back of the intra ocular lens implant which again precludes a view of the retina. The surgeon will then excise the capsule along with the vitreous, using the same vitrectomy cutter.
f) In cases where the retinal detachment has been caused by ‘endophthalmitis’ or infection spread to the back of the eye. The vitreous is a wonderful culture medium for all sorts of germs, i.e. all germs find the vitreous an excellent soil on which to thrive and multiply. Hence, in cases of endophthalmitis, the vitreous is always removed.

Q. I am a shortsighted person, wearing minus numbered glasses. You have already scared me by saying I am more prone to retinal detachment as compared to my friend who has no numbers. Should I give up reading or watching TV or studying too hard? What about sports and exercises?
A. Just as over use of your legs for walking does not ‘spoil’ your legs, so also, overuse of the eyes for reading, studying, watching TV, will not harm the eyes or make them more susceptible to retinal detachment. You can also lift normal weights; bend as much as you like, swim, walk, jog or exercise. Only remember to visit your eye doctor for your regular checkups as and when called and to rush to your eye doctor when you suddenly see less or there is a sudden increase in black spots or persistence of flashes of light.

Q. My grandmother finds increasing difficulty reading small print. She also cannot recognise people even when they are close. She says their outlines are visible, but their faces are a blur. She has already been successfully operated for cataract in both eyes. What could be wrong?
A. She probably suffers from age related macular degeneration (ARMD or AMD). This condition used to be called ‘senile macular degeneration’ till senior citizens objected to the word ‘senile’ and society became more sensitive to the feelings of our senior citizens. The macula is the most sensitive portion of the retina, located almost in the centre of the retina. It is responsible for fine vision and for reading. Due to age related changes, there is a loss of efficiency in the working of the retinal cells in the retina (‘dry ARMD’), which may or may not result in mild scar formation at the macula. Sometimes, (approx.20% of cases) there may be formation of new, extra leaky blood vessels below the macula. These may leak blood or fluid under the macula, causing marked drop in vision (‘wet ARMD’).

Q. What are the early symptoms of ARMD?
A. As I said, this affects chiefly the central vision. If there is leakage of blood or fluid, as in the ‘wet’ type, this drop in vision may be sudden. In many cases, there is a gradual loss of central vision. There may also be distortion of vision- the patient typically describes a window border as being crooked or bent. During reading, straight lines may appear crooked. Words may appear ‘bunched up’ or spread out. Colour discrimination may become faulty.

Q. What are the treatment options available?
A. For the dry type, there is no specific treatment. Anti-oxidant rich foods and anti-oxidant pills are supposed to delay the progress of ARMD, but the jury is still out on that one. There is no conclusive proof to indicate that these pills do or do not work. Many eye surgeons prescribe them nonetheless, as they feel “at least they do no harm” (except to the pocket of the patient!).
For the wet type, usually an angiography is done using a dye known as ‘fluorescein’. This dye is injected into the vein, usually in the forearm. It takes 10 seconds to reach the retina in sufficient concentration that it stains the blood vessels of the retina green. The patient is made to sit in front of a ‘fundus’ camera and serial pictures are taken at regular intervals. The eye surgeon then examines the pictures later. He looks for evidence of the new vessels, site of leakage, distance of the leakage from the centre of the macula etc. Based on the findings of the FFA (fluorescein fundus angiography) test, he may decide to apply laser to the retina at or near the macula. There are several options now even in the laser treatment, with argon laser or diode laser being used. 2 new treatment modalities are TTT or transpupillary thermo therapy (where a modified diode laser gently heats or ‘cooks’ the retina for about a minute) and PDT or Photodynamic therapy. In the latter method, a dye called verteporfin in injected into the vein in the forearm. This dye enjoys residing in new vessels under the macula. When laser light is applied, only the new vessels containing this dye are destroyed while leaving all other tissue undamaged. Unfortunately, only 10-15% of all macular degenerations are amenable to any form of laser treatment.

Q. What about intravitreal injections of antiVEGF agents?
A. It has been recognised for some time now that a lot of the damage in wet ARMD is caused by abnormal proliferation of new vessels just under the retina. Growth of new vessels in the body is promoted by vascular Endothelial Growth Factors or VEGF. Hence injecting an anti-VEGF into the vitreous, where it is close to the retina helps prevent new vessels from sprouting and allows the existing vessels to close down. Currently there are 3 such AntiVEGF agents in the market, all with unpronounceable generic names. They are therefore known commonly by their trade names which are Avastin, Lucentis and Macugen. There are conflicting reports in literature about which of these is better, so it is wisest to let your eye doctor decide which is best for your grandmother. Lucentis and Macugen are more expensive; they are approved by the US FDA for treatment of wet ARMD. Avastin is cheaper, is available in a multidose vial, but is an approved drug for treatment of colon cancer. By chance it was discovered to be effective in the treatment of wet ARMD as well! Usually there is a treatment course of 3 injections with a gap of 4-6 weeks between injections. However, in some cases, more injections may be required. So it is wise to learn from your doctor exactly how much of a hole the treatment regime will burn in your pocket!

Q. What can we do to make my poor grandmother at least read large print, to pass her time?
A. We can try special magnifiers called LVA or Low Vision Aids. Previously all we had at our disposal were hand held magnifying glasses. However, now there are well equipped LVA clinics, where you can get stand magnifiers, telescopic glasses and even use of the computer and TV screens to magnify a printed word and project it onto a TV or computer screen so that it appears many times its actual size.

Q. We are in the 21st century, doc; can I not get a new retina or a retinal transplant for her? I can afford it.
A. Experimentation with retinal transplants is going on in several centres around the world, including Hyderabad in India. However, this technology is in its infancy. It will still take several years before we even know whether it will be at all effective in humans. If at all, it may help those who are bilaterally blind to see blurred forms from one eye.

Q. What about an artificial retinal chip or use of miniature TV cameras that I read about somewhere?
A. These are also being experimented with. At present, after spending millions of dollars in research, scientists have succeeded in making a bilaterally blind man appreciate the difference between light and dark. We are still several years away from affordable technology to help the average blind man see his loved ones.

Q. Can those who have had retinal detachment surgery or those who had ARMD donate their eyes after death?
A. Yes provided their corneas are clear. It does not matter if the eye was blind due to retinal detachment or the detachment surgery was not successful or if they had poor vision due to ARMD. As long as the cornea is clear, they can donate their eyes. Their corneas will be used to restore sight to at least 2 blind persons, suffering from corneal blindness. Isn’t it wonderful to know that a blind person (due to a retinal cause) can help restore sight to 2 blind persons (blind due to opaque corneas)?