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Results for “CORNEAL OPACITY”

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At least 163 records · Page 9Linked to original sources
PubMed1992

[Corneal opacity after photorefractive keratectomy with an excimer laser. Cause, objective measurement and functional consequences].

A marginal loss of corneal transparency or 'haze' is a phenomenon commonly experienced after photorefractive keratectomy using excimer lasers (193 nm). The putative causes of this phenomenon are the presence in the surgical site of (1) activated keratocytes, (2) vacuoles and (3) newly synthesized collagen. A CCD camera device was employed in order to measure the corneal transparency. Both scattered and reflected light in the slit image of patients' corneas was measured using polarizing filters and image analysis software. We observed an increase in reflected and scattered light until the second postoperative month, followed by a subsequent decline. However, the combined signal generated by reflected and scattered light showed a second increase at 4 months postoperatively, whereas the signal generated by scattered light alone stayed at lower levels. These objective measures of changes in corneal transparency were correlated with changes in visual performance using psychophysical tests measuring visual acuity at different contrast levels (100%, 20% and 5%). In all patients we observed a good correlation between the signal generated by scattered light alone and the reduction in the 5% contrast visual acuity performance. These disturbances in low contrast visual performance were only significant during the first 3-4 months postoperatively, and thereafter most patients returned to their preoperative value. Eighteen percent of our patients discontinued topical steroids postoperatively. No difference in corneal transparency was observed.

Adult↗
PubMed2002

[Corneal haze after photorefractive keratectomy. Role of individual collagen type IV synthesis on postoperative corneal opacity].

PURPOSE: Histological studies on human corneas have shown that collagen type IV plays a major role in the development of haze after photoreactive keratectomy (PRK). Currently, there is no clinically available pharmaceutical agent which can inhibit the synthesis of collagen IV. The aim of this study was to determine if there are individual differences in the expression of collagen IV and if there is a correlation between the amount of collagen IV and haze. This would give new options to prevent haze after PRK. PATIENTS AND METHODS: PRK was carried out on 26 eyes (26 patients) with a myopia ranging between -1.50 to -6.00 D. Prior to the surgery a small sample of epithelium was taken from the cornea and the individual concentration of collagen IV alpha 3 mRNA was quantitatively determined by a newly developed PCR test. RESULTS: In all samples collagen IV alpha 3 mRNA was measured with levels between 0.11 and 6.42 (mean: 1.68; SD: 1.64). There was a correlation between haze and the amount of collagen IV alpha 3 mRNA. (r = 0.92). CONCLUSIONS: With this quantitative PCR-based test we were able to measure the individual collagen IV mRNA concentration in corneal epithelial cells. Further development of this test could establish a screening test which identifies patients with a pronounced synthesis of collagen IV as high risk individuals in terms of haze.

Adult↗