SUMMARY A randomised controlled study of photocoagulation compared with no treatment in central retinal vein occlusion is reported. Forty-eight patients were allocated into treated and control groups by a random procedure 3 months after their first visual symptoms. For the analysis they were subdivided into (1) ischaemic type, and (2) hyperpermeability-response macular-oedema type of central retinal vein occlusion.In neither group did treatment confer benefit as far as visual acuity was concerned. However, iris, disc, and retinal neovascularisation improved after treatment in the ischaemic group. In addition none of the treated patients progressed to neovascular glaucoma. Macular-oedema improved in treated patients with the hyperpermeability response, but the visual field was affected and atrophic changes at the macula precluded visual improvement.It is concluded that photocoagulation should be used only to prevent complications in the ischaemic type of central retinal vein occlusion. It does not appear to be of value in the hyperpermeability group.Photocoagulation has been shown to be effective in the treatment of both macular oedema and neovascularisation in diabetic retinopathy. It is therefore reasonable to assume that similar results can be achieved in retinal vein occlusion, where macular oedema and new vessel formation are common complications. There are several reports indicating 'good results' (Zweng et al., 1974;Theodossiadis et al., 1974;Freyler and Nichorlis, 1974;Wetzig and Thatcher, 1974;Oosterhuis and Sedney, 1975;Sedney, 1976) 3 months after initial visual symptoms. At the 3-month examination patients whose visual acuity was 6/24 or worse entered the study provided they did not have neovascular glaucoma or other eye disease affecting vision and precluding treatment, and provided they agreed to randomisation.Randomisation was by the use of pre-prepared sealed envelopes which indicated whether an eye was for treatment by photocoagulation or remained untreated, i.e., control. No other therapy for vein occlusion was given to any of the patients, but glaucoma and medical conditions were treated as required. There were 24 treated and 24 control patients. The mean age of the patients was 62 years (range 44-79 years) in the treated and 61 6 years (range 36-79 years) in the untreated group.The patients were followed up for at least 1 year after entering the trial whenever possible. Five patients were not followed up for the required time. Two died, 4 and 10 months after entering the trial, 1 left the country, and 2 defaulted from follow-up.During the course of the study the initial scheme was slightly modified so that eyes with considerable capillary closure were entered into the trial as soon as the first fluorescein angiogram became available, i.e., before 3 months expired.Prior to analysis patients were subdivided into two subgroups according to the main cause of visual loss as revealed by fluorescein angiography. The 741
IT IS generally agreed that simple myopia and degenerative myopia are separate conditions, the former being a normal chance variant in the biological series which includes emmetropia and hypermetropia (Duke-Elder, 1949) and the latter a pathological condition. Degenerative myopia in its advanced stage consists of an association of defects: a highly myopic refraction, chorio-retinal degeneration and atrophy, thinning of the posterior sclera, and an increased axial length of the eye. Additional defects, such as cupuliform cataract, glaucoma, and retinal detachment, are relatively common in patients with degenerative myopia, and a hereditary element is often present. In the investigation here reported the function of eyes with degenerative myopia has been studied using electroretinography and electro-oculography.Although degenerative myopia may be congenital, it usually takes many years to develop. In its early stages a myopic refraction, straight temporal vessels, and a temporal crescent at the optic disc may be the only physical signs, and these cannot be distinguished from cases of simple myopia (Blach, Jay, and MacFaul, 1965). It is hoped that the electrical tests described here may prove to be of some diagnostic and prognostic value, and be of some help in pointing to the primary defect in degenerative myopia.Review Karpe (1945) performed ERGs on four eyes with high myopia; in three the ERG was definitely subnormal, while in the last it was probably subnormal. Fran9ois and de Rouck (1954) studied the ERG in patients with both simple and degenerative myopia; those with simple myopia had normal ERGs, while in 75 per cent. of those with high myopia the b waves were depressed and the a waves varied from strongly positive to completely absent. They claimed that the ERG changes preceded the ophthalmoscopic changes in degenerative myopia, although they classified degenerative myopia by the fundus changes. They found no correlation between the amplitude of the b wave and the degree of myopia. From the changes occurring in the b waves, they argued that the retina rather than the choroid was primarily involved in this disease. Franceschetti, Dieterle, and Schwarz (1960) investigating fourteen cases of uniocular myopia, found that the b waves were reduced in the scotopic ERG and that this reduction was related to the degree of myopia. Jayle and Boyer (1960) found that myopic patients with good visual function had normal ERGs, while those with poor visual function had subnormal ERGs; they suggested that the photopic system was involved before the scotopic system. Ponte (1962) found that in simple myopia the mean amplitude of the b wave was slightly reduced, while in severe myopia the ERG was considerably affected, the most frequent finding being a subnormal ERG of negative type.Franqois, Verriest, and de Rouck (1956) examined four patients with high myopia and pronounced choroidal changes and found that the resting potential level was normal. On the other hand, Arden, Barrada, and Kelsey (1962) performed EOGs on a number...
IN 1953 it was found that exposure of kittens to high ambient concentrations of oxygen resulted in obliteration of their retinal vessels, and that subsequent return to air resulted in vasoproliferation (Ashton, Ward, and Serpell, 1953). It was later briefly reported that the retina of the ratling was considerably less susceptible to hyperoxia than that of the kitten, since only the posterior vessels were obliterated, but no opinion was given on vasoproliferation at that time as the ratlings had not survived on transfer to air (Ashton, Ward, and Serpell, 1954).Other workers, however, have reported that the retina of the ratling behaves in an exactly similar way to that of the kitten (Patz, 1954a,b;Brands, Hofmann, and Klees, 1958); indeed ratlings were some of the chief experimental animals used by Patz, Eastham, Higginbotham, and Kleh (1953) and by Patz (1954a,b) in demonstrating retinal vasoproliferation due to oxygen exposure in their studies on retrolental fibroplasia. Patz (1954a) also reported complete obliteration of the retinal vessels of the rat after 3 days' exposure to hyperoxia and he obtained vasoproliferation in oxygen -a finding which was not confirmed by Brands and others (1958).In view of these conflicting results and because the ratling would be a more convenient animal than the kitten for this type of work, we have carried out a further series of experiments to determine the effect of hyperoxia on the retinal vessels of the ratling. ANATOMICAL CONSIDERATIONSThe anatomy and development of the retinal vasculature of the rat have been described in detail by
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