The short-wavelength mechanisms of Stiles in age-related macular degeneration.

Clinical measurements by the increment-threshold technique of W.S. Stiles are reported in five cases of age-related macular degeneration. Measurements were made on a modified Tübingen perimeter using 1 degree, short-wavelength targets presented on a red field.

[Changes in the visual fields following filtering surgery in advanced glaucoma]. / Modification du champ visuel au décours des interventions filtrantes dans les glaucomes évolués.

The authors report about the results of a preliminary study concerning the changes of glaucomatous field after glaucoma filtering surgery in patients with advanced glaucoma. Mesopic campimetry had been selected because of its precision for central field defects. The first results appear to be favourable. No patient lost central vision suddenly after surgery. The authors have tried to research predictive risk factors. The factors that seem to be the most important to consider are the preoperative campimetric shape and the angle anatomy.

[A color after-effect: the McCollough effect]. / Etude d'un post-effet coloré: l'effet McCollough.

Coloured after-effect parameters have already been studied but the process involved in these events remains unknown. In the case of the McCollough effect, Shute has shown that the induced colour decreases rapidly at first and then more slowly. In a normal subject the effect can no longer be detected after approximately 2 hours. Results have been used to determine a relationship between the purity of the induced colour and time: I = I0 e-bt, where b is a typical parameter of the subject related to his physiological state. A figure of b approximately 0.03 min-1 was obtained in the normal subject. The rate of decay is influenced by certain drugs. In particular, a greater decrease in induced colour is obtained when caffeine is taken. In this case, the value of the decay constant b is about 0.06 min-1. Results obtained with anticholinergic agents are contrasted with those obtained with caffeine: slowed decay occurs. Hence the value of the decay constant is about 0.01 min-1. Data show that the McCollough effect could be an inhibitory mechanism in a visual pathway and which tends to suppress neural connections. It should be noted that the geometrical structures of patterns play an important part in the perception of the induced colour. For example, with square-wave gratings, the strength of the induced colour depends on spatial frequency and orientation. The McCollough effect mainly concerns the ways in which we perceive both pattern and colour. It may be located either within the retina or more centrally in the visual system.

[Phototoxicity of ultraviolet rays on crystalline lens and retina. Study of the optic transmission of implants with or without anti-UV treatment]. / Phototoxicité des ultraviolets sur le cristallin et la rétine. Etude de la transmission optique d'implants traités et non traités anti-U.V.

The authors have checked absorbing U.V. IOLs. The use of these IOLs seems to be necessary because of the retinal damage due to direct exposure to near U.V., after lens extraction. Since about ten years a growing body of works has shown phototoxicity on lens and retina by U.V. radiation between 392 and 400 nm. This radiation transmitted by the cornea is not absorbed during the first decade. Progressively, cumulative effects of near U.V. on the lens involve fluorescent chromophore formations, pigmentation, and interferes with synthesis of lens proteins, catalyse insoluble proteins. Finally, cataract are produced as well as experimentally with U.V. lasers. In aphakic eyes the risk of retinal damage increases dramatically. Consequently IOLs absorbing U.V. radiation could protect the retina. A spectrographic check of U.V transmittance by standard IOLs and U.V. absorbing IOLs has shown that the U.V. absorbing IOLs block all radiations below 400 nm.

[Age and photopic and mesopic visual acuity]. / L'âge et les acuités visuelles photopiques et mésopiques.

Visual acuity at high luminance (100 cdm2) and at low luminance (0.8 cdm2) was measured in normal subjects aged between 20 and 50 years. A decrease of visual acuity at Low luminance was noted with increasing age whereas high luminance acuity remained unchanged (20/20). At thirty years of age, low luminance visual acuity was an average of 20/30 decreasing at 40 years to 20/40. Results were confirmed by statistical analysis. A short study with interference fringes, formed by a coherent light (neon-helium laser) produced directly on the retina and thus by-passing optical effects on the eye, suggested that the retina-brain system was responsible for decreased mesopic visual acuity, night myopia or right presbyopia not playing any part in this decrease as suggested by some authors. Consequences of these findings, concerning particularly workers at low luminance such as pilots or drivers, are discussed.

[Functional aniseikonia: clinical study of 110 cases (author's transl)]. / Etude clinique de l'aniséiconie fonctionnelle (A propos de 110 case).

A clinical study was conducted in 110 cases of subjective aniseikonia, a syndrome that is often neglected. After in practice summarizing the different distortions composing the phenomenon of aniseikonia, a description of the prototype apparatus used for the experiments is given: it is eikonometric stereo-projector the originality of which lies in the measuring system, constituted by the projected stereograms. Three parameters were studied: depth-perception, peerception threshold of anseiikonic disparity, and value of the found aniseikonia. The results are presented in relation to 3 groups of subjects: 14 emmetropic, 32 isometropic, and 64 anisometropic, 32 isometropic, and 64 anisometropic patients, including 24 monocular aphakic. The author shows the advantage of contact lens correction in the last cases: with an average of 3.5 p. cent, the found aniseikonia was always inferior to 6 p. cent and to the theorectical levels currently accepted. Finally, the phenomenon of "cortical malleability" arises in the adaptation of the patient to his optical correction and could regularly and progressively be increased.