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Translucent Occluder (translucent + occluder)

Distribution by Scientific Domains

Medical Sciences	100%

Selected Abstracts

The prevalence of suppression in amblyopic individuals

OPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 1 2008
Brendan Barrett
Purpose:, A popular view of visual functioning in individuals with amblyopia is that the weaker eye is suppressed in key regions of the binocular visual field. Indeed, some have argued that chronic interocular suppression may represent the cause of amblyopia. Here we evaluate the prevalence of amblyopic-eye suppression in a simple light detection task when the eyes are open, minimally dissociated and in their habitual motor position. Methods:, A custom program on the Humphrey Field Analyzer (Carl Zeiss Meditec Inc., Dublin, CA, USA) was used to measure detection thresholds for a blue light on a yellow background along the horizontal meridian at two-degree intervals to an eccentricity of 25 degrees on either side of the fixation mark. The fellow eye was prevented from seeing the target using three different methods: (1) full-occlusion (i.e. no light entered the fellow eye), (2) a translucent occluder (3) a yellow filter in front of the fellow eye. In (3), the yellow filter only prevented the fellow eye from seeing the blue stimulus; the fixation mark and the background remained visible (minimal-dissociation condition). Fourteen amblyopes participated in the study, of whom 11 had strabismus. Results:, Three basic patterns of results were observed. (1) Only three of the fourteen participants (,21%) showed evidence of suppression, where amblyopic-eye sensitivity was lower with the fellow eye open. In these cases, the retinal locations that showed greatest suppression corresponded to the direction and angle of the strabismus. (2) Three participants (,21%) showed the opposite effect to the result in (1); i.e. amblyopic-eye sensitivity was greatest when the fellow was open with minimal dissociation between the eyes. One possible explanation is that the dominance of the fellow eye caused this reduction. (3) Seven participants (50%) exhibited patterns of amblyopic sensitivity that did not depend upon the occlusion status of the fellow eye. The results for one participant did not fit into any of the above patterns. Conclusions:, Suppression appears not to be a universal feature of central amblyopic vision. Our results for this simple detection task suggest that suppression may exist in as few as 20% of amblyopes. These results present a challenge to the view that suppression represents a root cause of amblyopia but they are consistent with the view that the amblyopic eye makes a useful contribution under habitual viewing conditions. [source]

Ganzfeld changes in short wavelength automated perimetry

OPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 6 2002
S. Sukumar
Purpose:, The change in perception of background illumination known as Ganzfeld changes occurs while performing perimetry test. It occurs under higher background illumination and whilst covering the non-tested eye with a black patch. We investigated the occurrence of Ganzfeld changes in Short Wavelength Automated Perimetry (SWAP) and assessed the performance while covering the non-tested eye with a standard black patch and with a translucent occluder. Methods:, Twenty-eight volunteers of age 22 ± 3 years participated in the study. A custom made 16-point test was used to analyse the sensitivity with a standard black patch and with the translucent occluder. The number and duration of Ganzfeld changes in each condition were detected by subjective responses. The visual comfort of the subjects under each patching condition was assessed using a comfort scale (0,5) and subject's preference. Results:, Ganzfeld changes occurred when a standard black patch was used and appears to influence the ability to see the test targets. With a standard black patch 5 Ganzfeld changes were observed per minute and it varied between 2 and 8 s. The duration and occurrence increased towards the end of the test. Using a translucent occluder almost eliminates the occurrence of Ganzfeld changes and improved the sensitivity (p = 0.001). Of the 28 subjects, 22 preferred translucent occluder to black patch. Conclusion:, Use of a translucent spectacle occluder over the non-tested eye significantly reduces the Ganzfeld changes and improves the performance in SWAP. [source]

Effects of prostaglandins on form deprivation myopia in the chick

ACTA OPHTHALMOLOGICA, Issue 5 2000
Niyun Jin
ABSTRACT. Purpose: To investigate the possible role of endogenous prostaglandins in the development of form deprivation myopia, as well as the effects of exogenous prostaglandins using atropine as a positive control. Methods: Monocular form deprivation was accomplished by mounting a translucent occluder on one eye of 2,3 day old chicks for 1,4 weeks. Ocular occlusion for 1,2 weeks was used for pharmacological blocking experiments. The axial length of the eye was measured by ultrasonography. Results: Indomethacin, administered intramuscularly, subconjunctivally or intra-vitreally had no significant effect on myopia development. Exogenous PGE2, PGF2, and latanoprost acid administered subconjunctivally, or topically as isopropyl ester eyedrops had no statistically significant effect on the myopia development. However, PGF2, significantly (p<0.01) attenuated the development of myopia after intravitreal injection. The other two prostaglandins had no statistically significant effect. Conclusions: Endogenous prostaglandins are unlikely to play a significant role in the development of form deprivation myopia in the chick. However, PGF2, suprisingly seems to retard the development of form deprivation myopia, but only when administered intravitreally. Whether the mechanism of the myopia retardation is direct or indirect remains unknown. [source]