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Eva Philippaki, Andy Doraiswamy, Chris C Hull; Association between grade of intraocular lens glistenings and in vitro forward light scatter.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3750.
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The purpose of the study was to test if there was an association between objective in vitro forward light scatter and grade of glistening in intraocular lenses. The study directly measured forward light scatter without the confounding effects of other structures in the eye and subjective responses.
Seven intraocular lenses were subjected to thermal gradients resulting in glistenings graded from 0 (clear) to >4. The angular distribution of forward light scatter was measured using an optical bench system over ±18 degrees. Measurements were made for each of the seven test lenses at 3mm, 4mm and 5mm pupil sizes. Forward light scatter was quantified by calculating the straylight (area under the scatter function) for the large angle domain (> 1 deg.). The scatter index was calculated as a measure of the angular distribution of scattered light within this domain.
There was no significant association between straylight and grade of glistenings for any of the three pupil sizes (P>0.25 all cases; Spearman’s rho). Straylight values for IOLs graded 0 to 4 showed a weak positive correlation (rs = 0.203) that wasn’t statistically significant (P=0.70) but rose sharply for the lens graded >4 whose straylight scores were over 6 times higher than the grade 4 lens. Scatter index varied from 1.97 to 2.63 for the seven IOLs but did not vary with pupil size (within SE) for each lens and similarly was not associated with grade (P>0.35 all cases; Spearman’s rho).
Our results indicate that light scatter produced by glistenings is poorly represented by grading. There is some indication that light scatter may increase non-linearly with the number of glistenings implying there could be a threshold response for tests of visual function when glistenings are present. It remains possible that the grading system is insufficient to pick up the changes in glistenings relevant to light scatter. Further experiments relating in vitro forward light scatter measurements to objective measures of glistening size, density and location are warranted.
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