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.

Analytical and statistical survey of early stages of open-angle glaucoma with low luminance visual field.

The purpose of this study was to show the early visual field signs in glaucoma using the 'Moniteur Ophtalmologique' at a background mesopic luminance of 0.3 apostilbs. Forty-five patients were selected, and 68 eyes with suspected early glaucoma were examined. Among the defects which were studied, we noticed a predominance of what we called pericaecal scotoma (PCS) and levelling. These two first signs appear as an alarm signal. To detect the early visual field signs of open-angle glaucoma developing, this study recommends the use of a background mesopic luminance of 0.3 apostilbs and observation for two uncommon visual field signs: PCS in evolution around the blind spot and a slight decrease in central mesopic sensitivity called levelling.

Ocular growth in the fetus. 1. Comparative study of axial length and biometric parameters in the fetus.

The knowledge of ocular growth during fetal life, when compared with other fetal biometric parameters, could not only provide a better definition of malformation syndromes but could also give a better understanding of certain pathological processes in premature babies and in newborns. As the literature concerning prenatal ocular dimensions contains few data, the aim of this study was to measure the axial length of the globe (AL) in fetuses and compare this measurement with their gestational age, weight, height, head circumference (HC) and thoracic circumference (TC) in order to compile a reference table. In the present study, 76 globes from 38 fetuses (18-41 weeks gestational age) from the Department of Pathology (Timone University Hospital, Marseille) were examined. Ultrasonography A and B were used to measure the AL, and a pathological examination determined fetal weight, HC, TC and height. We were interested to find out which of the parameters studied would give the best correlation with ocular growth. Statistical analysis showed that HC remained the most discriminant factor and correlated best with ocular growth. We thus obtained an equation for ocular size according to HC that could serve as a basis for detecting pre- or postnatal ocular defects.

[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.

[Early postoperative campimetric outcome after trabecular surgery of chronic advanced glaucoma]. / Evolution campimétrique post-opératoire précoce après chirurgie filtrante dans les glaucomes chroniques évolués.

The authors report about the results of a preliminary study concerning the changes of glaucomatous visual field just after glaucoma filtering surgery in patients with advanced glaucoma. The visual field was established preoperatively, then 7 and 30 days in post operative period. Mesopic campimetry had been selected because of its precision for central field defects. The results appear to be favourable with 13 improvements 14 stabilizations, and 7 aggravations without loss of central vision. The authors have tried to determine predictive risk factors. The most important one are preoperative campimetric shape, angle anatomy, refraction and cardiovascular diseases.

[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.