[Postgraduate teaching of orthopedic surgery: experiences with the Edouard Samson course, in effect since 1962].
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Education, Medical, Graduate↗
Biomedical subjects
G Lafond
Publications and source records attributed to G Lafond.
Treatment of halos after photorefractive keratectomy.
BACKGROUND: Some patients, despite a good visual outcome after photorefractive keratectomy (PRK), have severe problems with halos. METHODS: Ten eyes with a near-plano refraction after PRK were treated again with PRK to reduce halos. The goal of the second surgery was to enlarge the diameter of the treatment zones without changing the refraction obtained by the first surgery. The treatment zone was enlarged from 5 or 6 mm to 7 mm. In eyes in which a multizone technique was used in the first PRK, the amount of correction was increased in the transition zone. However, the refractive power in the central 4 or 5-mm zone was not altered. This result was obtained by calculating the amount of desired increased correction on a large zone (6 or 7 mm) and then for the same amount on a smaller zone (4 or 5 mm). The latter, which would produce changes of curvature in the central zone, is subtracted from the overall treatment. Only the part of the treatment where the laser beam increased from 4 or 5 mm to 6 or 7 mm was delivered to the eye. In this process, only the peripheral zones were modified. The central 4 or 5 mm zone was deepened but its curvature and the refraction remained the same. RESULTS: A decrease of symptoms was noticed by seven of the ten patients. In all eyes, the refraction obtained by the initial surgery was not significantly changed by the second surgery. The best results were obtained in milder myopic patients who had their first surgery with a small diameter ablation zone. CONCLUSION: Halos can be reduced by repeating the PRK and by increasing the treatment zone without changing the refraction obtained by the first PRK.
Cornea↗
[Changes in the B wave of cones and rods in diabetes mellitus induced by streptozotocin in rats].
The purpose of the present study was to evaluate the electroretinophysiological effects of streptozotocin-induced diabetes in the rat. More specifically, both B wave amplitudes and implicit times generated with various intensities of light stimulation were examined in diabetic animals adapted to either scotopic or photopic conditions. Results indicate that B wave amplitudes, but not implicit times, were differentially affected by these two conditions of light adaptation: amplitudes were significantly enhanced but markedly decreased under photopic and scotopic conditions respectively. The possible functional relationships between these specific ERG changes and our previous observations of selective alterations in retinal dopaminergic systems in this animal model of diabetes are discussed.
Animals↗