Diabetes, Hypertension and the Eye
Q. Why are you devoting an entire chapter to such uncommon diseases?
A. You will be surprised to learn that India has perhaps the world’s second largest population with diabetes and the number of new diabetics is growing by leaps and bounds. This is due in large measure to our aping the couch potato culture of the west and their junk food habits. So also, hypertension or high blood pressure, which was earlier restricted to those with Type A personalities (perfectionists, high achievers etc.) is increasingly affecting the urban poor as well as the rural population.
Q. Okay, so diabetes is a common disease, but isn’t that the concern of the physician and the diabetes doctors?
A. Diabetes affects the eye in a myriad of ways, affecting almost all structures of the eye. Eye affection increases with duration of diabetes and with poor control. Both factors are important. This means that if you have diabetes of say 20 years duration, you have greater than 50% chance of developing eye affection, even though you have had it in superb control for all those years! Your risk however increases even further if you have been a ‘naughty’ diabetic who has paid scant regard to your doctor’s advice on diet, medication and exercise.
Q. How often should I get my eyes examined if I am a diabetic or hypertensive?
A. As soon as you are made aware of your diabetes or hypertension, you should have a complete eye examination. If the diabetes or hypertension has not affected your eye, your eye doctor may recommend annual visits. The frequency of visits may increase if you are detected to have diabetic or hypertensive eye disease.
Q. Doc, will you quit talking in abstract terms and lay it on straight – tell me, what are the ways diabetes can affect my eyes?
A. The commonest affections due to diabetes are retinal problems, glaucoma, cataract and the increased risk of eye infections. Other, less common problems are paralysis of one or more eye muscles, dry eye and affections of the optic nerve (the nerve of sight).
Q. I refuse to be scared by your answer. I think I will just wait till I develop some eye symptoms before I visit an eye specialist. After all each consultation costs money!
A. That may be being penny- wise and pound-foolish. Many a problem can be detected and treated even before symptoms develop. Treating it later may be more expensive and more importantly, less effective! The blood vessels of the retina are the only blood vessels in the whole body that can be viewed with a simple non-invasive technique (ophthalmoscopy). These blood vessels mirror the changes taking place in the rest of the body’s blood vessels. This is why, an eye doctor can tell you are a diabetic or hypertensive simply by examining your retinal blood vessels. At the next check-up, he can tell if your retinal blood vessels are showing progressive changes of diabetes or hypertension and warn you to discuss stricter control with your treating physician.
Q. Could you elaborate on the retinal problems (retinopathy)?
A. The tiny retinal blood vessels in diabetics are more prone to leakages. This can result in leakage of blood in the retina (retinal haemorrhage) or into the jelly of the eye in front of the retina (vitreous haemorrhage). In case fluid containing protein leaks out into the retina, it tends to collect in the centre i.e. the macular area causing macular oedema. Fatty material, cholesterol etc may also leak into the retina, either in the centre or in the periphery. All leakages, whether of blood, fluid or cholesterol in the macular area will result in distorted vision or a drop in vision. This may be sudden, such as when bleeding occurs, or gradual, when fluid oozes slowly into the macular area. The patient will detect this provided he has been educated to examine his vision at home at regular intervals, covering one eye at a time. This vision testing should be done with the correct glasses worn, for both distance and near. He should obviously visit his eye doctor, the moment he detects this fall in vision. However, if the same leakages are not in the centre of the retina, the patient may not notice them till much damage has occurred. Therefore it is essential that he visit his eye doctor at regular intervals as suggested by him. The eye doctor will dilate his pupils as required and carefully examine the macula and periphery of the retina using an instrument called an ophthalmoscope. If he does detect these leaking areas, he may ask for a fluorescein angiography test to detect the site of leakage. He may decide to use laser treatment to treat these leakages.
Q. Will use of the laser cure my diabetic retinopathy?
A. The aim of laser treatment is to preserve whatever vision there is left, rather than improve it. Also, as the duration of diabetes increases, especially if it is poorly controlled, fresh hemorrhages and leakages can occur. This may necessitate repeated sittings of laser. Unfortunately, our retinal cells do not have the capacity to grow. Hence, whatever cells are damaged, will result in permanent loss of vision in the affected area.
Q. What if I decide to ignore the doctor’s advice or delay the treatment?
A. This is a very common tactic employed by patients – I call it the ‘ostrich’ approach. Stick your head in the sand and pretend the problem is not there or will not affect you or will somehow become better with time! Unfortunately, the problem only gets aggravated if not tackled in time. The diabetic retinopathy (affection of the retina) which only consisted of a few haemorrhages and/or cholesterol deposits on the surface of the retina – called background diabetic retinopathy can gradually lead to the formation of new, fragile tiny blood vessels in the retina. These repeatedly burst, giving rise to fresh haemorrhages. The vessels can ultimately burst into the jelly in front of the retina, giving rise to a vitreous haemorrhage, with tremendous drop in vision. Worse still, formation of scar tissue by nature may cause a pull or traction on the retina causing a traction retinal detachment. Proliferation of these new vessels on the retina or into the vitreous is known (quite obviously) as proliferative vitreo-retinopathy. This condition requires complicated (and therefore expensive!) vitreoretinal surgery, carrying a much-reduced visual prognosis. In advanced cases, permanent blindness can result.
The simple fact is, in most cases, with timely intervention during the background diabetic retinopathy stage, progression of the disease to the next stage can be arrested or at least markedly delayed. All it takes is for the diabetic patient to visit his eye doctor at regular intervals as advised, so that the retina can be examined, instead of simply going once a year to his neighbourhood optician for a new pair of glasses.
Q. Enough said about the retina – are there any other eye problems with diabetes?
A. You have a remarkably short attention span – I did mention in answer to an earlier question that diabetics are more prone to cataract, glaucoma and dry eye. This is another reason why a diabetic should have at least an annual check up with an eye doctor. He will not only look at the retina, but will also check the pressure of the eye, rule out glaucoma, examine the eye on a slit lamp biomicroscope to rule out early cataracts and test you for dry eye. The adage ‘a stitch in time saves nine’ was possibly dreamt up by a diabetic!
Q. In case I am advised eye surgery, is there any precaution I should take with my diabetic or hypertensive medications?
A. Most eye surgery is done under local anaesthesia, hence you need not starve yourself before the surgery. If you are on oral anti-diabetic agents, we usually recommend discontinuation of the medication on the morning of surgery. You may resume the medication along with your next major meal. In case you are on insulin, it is best you follow the advice of your diabetic specialist. You should find out from your eye doctor the time of surgery and inform your physician, so that he can alter your insulin schedule accordingly. For hypertensives, it is very important that they continue their medications as per their schedule and not miss a single dose, especially on the morning of the surgery. They should of course, inform their eye doctor about the medications they are on and the fact that they are hypertensive. He may wish to avoid the use of adrenaline and similar compounds during surgery as they may cause a rise in blood pressure.