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S. Schneider, D. Fonn, T. Simpson; Central Corneal Clouding Induced by PMMA Lens Wear During Eye Closure . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2397.
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To characterize edema and central corneal clouding induced by PMMA lens wear during eye closure.
12 Subjects wore a PMMA lens on one randomly selected eye, with the other eye as a control. The lens was fitted 0.1mm steeper than the flattest meridian. With the lens in situ, the study eye was closed and patched for 4 hours to induce corneal swelling. Measurements were made immediately following lens removal, as well as after 20, 40, 60 and 120 minutes. Three images of the cornea were taken with a digital camera (Nikon D70) attached to a slit–lamp biomicroscope using the sclerotic scatter technique. Three central corneal and midperipheral thickness and light scatter measurements were obtained with an Optical Coherence Tomographer (Humphrey–Zeiss OCT II). Baseline measurements with both instruments were taken before lens insertion. The average mean grey value of 3 images was calculated using image processing software (ImageJ). Custom software designed for the OCT was used to determine average corneal and epithelial thickness and integrated light scatter.
Corneal and epithelial thickness increased after lens removal (p≈0.000 and p=0.003, respectively) and then decreased over time (p≈0.000 and p=0.0026, respectively). Epithelial thickness returned to baseline by 20 minutes (p=0.38) but it took 2 hours (p=0.46) for corneal thickness to return to baseline. Overall light scatter increased after lens wear (image grey value, p=0.001) with recovery taking 120 minutes (p=0.36).The OCT results showed a slight increase in anterior and posterior corneal light scatter but the differences from baseline were not significant.
We could objectively quantify a variety of attributes that constitute central corneal clouding. Next to morphological changes (increased corneal and epithelial thickness) there is a quantifiable increase in accompanying light scatter in the central cornea, which we were able to demonstrate photographically.
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