[Indentation of large retinal tears (author's transl)]

According to us large retinal tears are between 20 degrees and 70 degrees in their largest dimension, which excludes true giant tears. Study of the data collected on 42 patients has shown us the following facts:--these retinal tears occur in phakic and often highly myopic eyes;--our global success rate is 73,8%;--tears smaller than 2 to 3 papillary diameters radially are on the whole easy to indent and failures are quite often related to a surgical fault;--tears wider than 3 papillary diameters radially are on the whole difficult to indent and failures are not always related to an obvious surgical fault, fishmouth phenomenon plays an important role;--in every case presence of blood in the vitreous seems to be unfavourable to the prognosis;--use of episcleral pockets solves must of times surgical problems related to fishmouth or tear dimension;--post operative intern limiting membrane retraction is frequent (10% vs 5,7% for all the retinal tears and detachments cured in the same period of time).

[Silicone sponges rejection (author's transl)]

Out of 633 retinal tears or detachments treated by cryocoagulation and Lincoff sponges without scleral dissection, our rate of sponge rejection is 8 per cent (51 out of 633). Out of these 51 rejections we have 4 spontaneous expulsions and 45 surgical removals. In 2 cases we could preserve the buckle by medical treatment. The most pre-eminent causes are in decreasing frequency: --the peroperative sponge infection, mostly by staphylococcus epidermidis, --the existence of an anterior positioned sponge, more than a quadrant long, factor of bad mechanical tolerance, --several operations. The rate of anatomical success is of 86% in this group of 51 patients (80% if we only number successes at six months). We have had 8 recurrences after sponge removals (15%). Recurrences are due to sponge infection; they are mainly due to the reopening of the primitive lesions (6 times out of 8). Only 5 recurrences have been cured (62,5%). This result seems, however, better than the one reached by authors using scleral dissection techniques; according to us this is due to the relatively rare severe vitreous reactions when episcleral sponges' infection occurs.

[Retinal detachment and argon laser prophylactic treatment (author's transl)]

We have studied 6 retinal detachments which hapened after a preventive photocoagulation with argon laser in 6 patients who had already had a severe retinal detachment on the other eye (2 anatomical success on 5 operated cases). This preventive photocoagulation was done on eyes which at the term were free of any retinal dehiscence. In this group of 6 we notice 2 giant tears (greater than 70 degrees) or 33% and 3 large tears (between 20 degrees and 70 degrees) or 33%. These high amounts do not correspond to what has been noticed before: - on the non photocoagulated fellow eyes (neither giant nor large tear) - on the whole lot of operated retinal detachments during the same period of time in our unit (2% of giant and 5,7% of large tears). We think that the responsability of laser in the development of these large lesions in predisposed eyes must be thought about. Studies on a larger scale will be necessary to have a more definite idea on this subject.

[Surgical treatment of retinoschisis (author's transl)]

We have made a review of 20 retinoschisis without retinal detachment operated on 12 patients. There is no case of hereditary retinoschisis, the affection may occur at any age, and there is no preferential refractive error. Main surgical indications were macular involvement or impending involvement, and associated retinal tears. A good anatomical result has been obtained in 90% of our cases (18 out of 20) with 2/3 complete reattachments and 1/3 almost complete reattachments (with minimal and well sealed residual schisis). Association of cryocoagulation and indentation is more effective than cryocoagulation alone. On the functional point of view we have had 15% of improved visual acuities and 30% of worsened ones, thus surgical intervention implies macular risks that one must try to prevent by using procedures as atraumatic as possible.

[Drainage of subretinal fluid: technic and results]

The drainage of subretinal fluid (S.R.F.) after choroidal diathermy offers a distinct advantage: important reduction of massive haemorrhages from the drainage site (4% vs 48% in the non diathermy group in our series). According to us it is not a decisive factor for the anatomical prognosis because complications of drainage in themselves seem to be a quite infrequent cause of anatomical failure. On the other hand we think that visual outcome is better in the diathermy group because of a diminution of macular haemorrhages.

Enzymatic variation at seven loci in nine natural populations of Drosophila melanogaster

Allozyme polymorphisms at seven loci have been studied in nine natural populations of Drosophila melanogaster from the Saône and Rhône valleys sampled in 1973 and 1974. A great deal of polymorphism was observed; an individual was on the average heterozygous at 20.2% of its loci. The populations were genetically very homogeneous throughout the region sampled. The number of ovariolae per female varied from one group of populations to another depending on their geographical separation. Yet the number of ovariolae remained constant from one year to the next. The results show that migration alone cannot explain the homogeneity of the allozyme frequencies. It seems reasonable to conclude that selection plays a major role in maintaining the homogeneity of populations living in proximal biotopes.