I have had type�1 diabetes for 34 years and have severe retinopathy. My right eye has been treated for proliferative diabetic retinopathy (with Pan Retinal Photocoagulation), and according to my last doctor, is “doing well”. There is some macular edema in the eye, but it is not at this time clinically significant. I see 20/20 in that eye. The left eye is legally blind. I underwent treatment for macular edema, and the macula reacted very poorly to the laser. A choroidal neovascular membrane formed, and I lost virtually all central vision. I see about 20/200 in this eye. In both eyes, I notice a marked decrease in “contrast sensitivity” which I am afraid is due to macular ischemia. At this point it’s mostly just annoying and not a severe handicap.

Except for some peripheral neuropathy my health is okay. Good kidneys, no microalbumin after repeated tests and no heart disease, after several stress tests.

I have had excellent control (A1c of 5.3%) for about a year, but my vision still seems to be getting worse. Before the catastrophe in my left eye, my A1c was about 7.5% for about four years, and prior to that, it was much worse. Is there any hope that my retinopathy might stabilize with good control, or is it too late? Please be honest — I need to know so I can prepare for this. My feeling is that it is probably too late. I just need to know if there’s any hope that I might save my vision at this point. I see a retinal specialist every two months. I’m trying my best to keep the control as good as possible.

Your main problem at the moment appears to be a gradual worsening of vision, mostly noticed as a reduction in contrast sensitivity. You still retain visual acuity of 20/20 in the right eye.

Contrast sensitivity and colour vision deterioration, in the absence of loss of acuity, is not uncommon in someone with diabetes, especially one who has had diabetes for as long as yourself. Visual acuity is a very crude measure of visual function, and the eye can sustain quite a degree of damage before the acuity is reduced. More sensitive functions such as contrast and colour discrimination is affected earlier. Fortunately, however, although patients can notice the difference, in many cases, it does not significantly limit visual function to the extent that it affects the quality of life. I hope that is the case with you.

Why is this happening when you have good diabetic control? Well, first, unfortunately, even with best control, some people continue to loose vision. It is likely, however, that if your control was less good, the deterioration would probably be faster. Secondly, you mention that you have macular edema in the right eye, although it is not Clinically Significant Macular Edema (CSME). There has been plenty of research that has shown that non-CSME macular edema can still lead to colour vision, and less often contrast sensitivity changes.

How could you treat this? Laser is a possibility but there are two reasons for not recommending this. Firstly, in your case, you have already lost central vision in the left eye due to a laser complication, i.e., choroidal neovascular membrane (CNVM). CNVM is a rare complication, and it is very unlikely that the same thing will happen in the other eye. The risk can be further minimised by using very gentle laser applications. Despite all that, however, there has to be good evidence to support macular laser to the eye that you depend upon now.

This takes me to the second issue — there is currently no evidence that laser treatment, at the stage of early visual changes (i.e., contrast and colour) makes any difference. I have myself been involved in research into early visual loss (mainly testing colour vision) and am keen to explore early treatment with laser, but as far as I am aware, nobody has actually done it yet. With one good eye, you should not be the one to try!

In many patients with early retinopathy, good control of diabetes can help to slow down, and in some cases, actually reverse the retinopathy. Your control, however, is excellent. It is unlikely that you could improve on this level of hemoglobin A1c without having hypoglycaemic attacks.

The next thing is your blood pressure — you don’t mention it — I presume that it is okay and that you have it checked regularly. As someone with severe retinopathy, you should aim to keep your BP at about 120/70. If it is higher, even if your internist might consider it okay, you should consider treatment. There is good evidence that “lower normal” BP is better than “higher normal” BP in diabetics. If treatment is considered, an ACE inhibitor would probably be the first choice as there is some evidence to suggest these agents have a protective effect on the kidney, and probably the retina, unrelated to the blood-pressure lowering effect. inally, you should check your lipids and cholesterol regularly and consider treatment with a “statin” even if the level is only slightly high. In the unlikely event that you are, to the slighted degree, anaemic, that should also be corrected.

To return to the problem with your left eye, the complication of CNVM is extremely rare. Can I re-emphasise that the chances of it happening to the right eye as well is astronomically low, especially if gentle laser is performed? If, therefore, you should, unfortunately, develop CSME in the right eye, you should not let what happened to the left deter you from having laser.

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