[Photocoagulation in diabetic retinopathy]. / La photocoagulation dans la rétinopathie diabétique.

At the present time, photocoagulation is the treatment of choice of diabetic retinopathy. It is founded on well-defined principles. The results are better than in the non-treated cases, on the condition that the indications are well established and the techniques appropriate. Fluorescein angiography remains indispensable. The objective of the photocoagulation is the destruction of ischaemic and avascular zones by large coagulations (avascular retinal photocoagulation). Depending on the severity and the rapidity of the evolution of the retinopathy, more extensive coagulations have to be performed in non-ischaemic zones (vascular retinal photocoagulation). The association of these two techniques is the so-called panretinal photocoagulation. This step need not be taken at once, but is indicated in some well-defined cases. The newly formed vessels are not coagulated, except when they are intraretinal.

Electrophysiological studies before and after argon-laser photocoagulation in diabetic retinopathy.

50 eyes with diabetic retinopathy were studied before and after treatment with argon-laser coagulation. After treatment, decreases of the L/D ratios of the EOGs and of the amplitudes of all ERG components were found. The scotopic b waves were more involved than the photopic b waves. The peak times were hardly modified. The dark-adaptation curves were not modified. Interesting was the fact that in the pretreatment findings the EOGs were involved before the ERGs. The decreases of the L/D ratios started when avascular and ischemic zones were seen on fluorescein angiography.

Further vision deterioration after argon laser photocoagulation in diabetic retinopathy.

Out of 222 eyes with diabetic retinopathy, observed during a period of 6-42 months after argon laser photocoagulation, 66 (30%) became worse. The most common complication was a fast increase of previous existing macular oedema due to extensive and heavy macular treatment. Another complication was an increase of the neovascularisation due to the inadequate treatment of avascular zones and heavy-leaking areas and to the growth of the neovascular tuft after the feeder vessel technique without previous peripheral ablation. Retinal and vitreal haemorrhages were frequent in this group. Fibrous tissue formation and vascular pseudopapillitis were less frequent complications. Large coagulations outside the macular area (peripheral ablation) are necessary to destroy the zones of borderline nutritional supply, which probably are closely related to the new vessel formation. The feeder vessel technique must not be used without a peripheral ablation although it may be of great help in destroying prepapillary or large neovascularisation.

Neovascularization after argon laser photocoagulation of macular lesions.

In three patients treated for macular degeneration with argon laser photocoagulation choroidal neovascularization occurred four to six weeks later at the photocoagulation site. Two of the patients were treated for angioid streaks of the macular region, the third patient was treated for disciform macular degeneration. Argon laser photocoagulation also induced neovascularization experimentally in pigmented rabbits.

Photocoagulation in diabetic retinopathy: focal treatment or partial retinal ablation?

Diabetic retinopathies treated by two different techniques were followed photographically and fluoro-angiographically. With the argon laser we treated the fluoro-angiographical lesions (210 eyes, follow-up 6 to 29 months) and with the xenon arc we made a barrage around the posterior pole without treating the lesions specifically (54 eyes, follow-up 12 to 36 months). In fact, we compared two different techniques and not two types of photocoagulators. After reviewing our results we may conclude that widespread coagulation (indirect method) is better than the topical treatment alone, but the combination of both techniques is the most suitable method.