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At least 109 records · Page 6Linked to original sources
PubMed1993

[Monocular diplopia caused by pressure of the upper eyelid on the cornea. Diagnosis based on the "Venetian blind phenomenon" in streak retinoscopy].

BACKGROUND: Abnormal pressure from the upper eye lid can cause a kink in the corneal vault along the lid margin. Depending on whether the lower or upper part of the lid exerts the higher pressure, the upper segment of the cornea acquires a prismatic effect which is base up or down, respectively. This causes a ghost image below or above the main image. In patients whose upper eye lid occasionally reaches down such that the kink traverses the pupillary area, the ghost image appears whenever they raise their lid above its usual position. The purpose of the present paper is to describe a retinoscopic phenomenon that allows an easy diagnosis of this condition. PATIENTS AND METHODS: About 20 patients with a ghost image below or above the main image were examined with a Placido disc, with a photokeratometer, and with a streak retinoscope. RESULTS: Photokeratometry revealed a slight deformation of the ring reflexes along a horizontal line at the border of the upper third of the cornea. This deformation was obvious only in a minority of the patients. The retinoscopic findings were more characteristic. With the streak horizontal, two or three light bands separated by dark intervals were seen in a "with movement", suggesting the impression of a Venetian blind being lowered or raised behind the pupil. Because of this impression, the author suggests the term ""Venetian blind phenomenon." DISCUSSION AND CONCLUSION: Monocular diplopia caused by abnormal lid pressure can be easily diagnosed by the "Venetian blind phenomenon". The optics can be explained as follows. Both the beams entering into, and emerging out of the patient's eye are being split by the prismatic effect of the upper cornea. Principally, this should result in four images; since, however, two of them overlay each other, only three separate images remain. In cases where the upper cornea is deflected backwards, resulting in a prismatic effect base down, the examiner can see all three images. In cases where the upper cornea is deflected forwards, resulting in a prismatic effect base up, the beams emerging from the patient's eye diverge, and the uppermost beam falls upon the examiner above his pupil, so that he can see only two of the three images.

Adult↗
PubMed1971

Retinoscopy.

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Humans↗
PubMed1994

Comparison of cycloplegic and noncycloplegic retinoscopy in Chinese pre-school children.

Twenty-seven Hong Kong Chinese children, aged 3 to 5 1/2 years, were recruited in this study to evaluate the relation between refractive error as measured retinoscopically before and after cycloplegia using cyclopentolate 1%. The noncycloplegic spherical refractive error of these children ranged from -0.75 to +2.50 D and approximately 98% of the Hong Kong pre-school children have a manifest spherical error within this range. The cycloplegic refractive error can be approximated by multiplying the spherical component of the manifest error by 1.45 and adding +0.39 D to the product, while keeping the astigmatic power and axis unchanged. Cyclopentolate 1% requires more time to produce mydriasis and cycloplegia in eyes with heavily pigmented irides; however, its final effect on refractive error is apparently independent of iris pigmentation and depends on the amount of spherical refractive error present.

Accommodation, Ocular↗
PubMed2002

Monocular estimate method retinoscopy: central tendency measures and relationship to refractive status and heterophoria.

BACKGROUND: Monocular estimate (estimation) method (MEM) is a widely used clinical test of accommodative response. Normative data for MEM are available based on the central tendency measures from a population of schoolchildren but not a clinical population. Also, the relationship of accommodative response to refractive status and heterophoria has been researched, but not with MEM as the determinant of the manifestation of accommodative response. METHODS: A group of 211 pre-presbyopic clinical subjects were tested with MEM for purposes of comparing the central tendency measures of a clinical population to established normative data and determining whether MEM varied with refractive status or near phoria. RESULTS: A lag of about one-third diopter was the mean MEM result for this clinical population. The median was +0.25 D. Myopia and near esophoria have a statistically significant relationship to MEM. CONCLUSIONS: The central tendency measures derived from MEM administered to this population replicate the central tendency measures found in a previous normative study. This study provides preliminary evidence that the difference between accommodative response and accommodative stimulus, as measured by MEM, may be influenced by myopia and esophoria.

Accommodation, Ocular↗