Methods for assessing forward and backward light scatter in patients with cataract
Alja Crnej1, Nino Hirnschall1, Con Petsoglou1
1From Moorfields Eye Hospital (Crnej, Hirnschall, Petsoglou, Findl), London, United Kingdom; Massachusetts Eye and Ear Infirmary (Crnej), Harvard University, Boston, Massachusetts, USA; Vienna Institute of Research in Ocular Surgery (Hirnschall, Findl), Karl Landsteiner Institute, Hanusch Hospital, Vienna, Austria; Sydney Eye Hospital (Petsoglou), Sydney, Australia.
Purpose:
To compare objective methods for assessing backward and forward light scatter and psychophysical tests in patients with cataracts.
Setting:
Moorfields Eye Hospital NHS Foundation Trust, London, United Kingdom.
Design:
Prospective case series.
Methods:
This study included patients scheduled for cataract surgery. Lens opacities were grouped into predominantly nuclear sclerotic, cortical, posterior subcapsular, and mixed cataracts. Backward light scatter was assessed using a rotating Scheimpflug imaging technique (Pentacam HR), forward light scatter using a straylight meter (C-Quant), and straylight using the double-pass method (Optical Quality Analysis System, point-spread function [PSF] meter). The results were correlated with visual acuity under photopic conditions as well as photopic and mesopic contrast sensitivity.
Results:
The study comprised 56 eyes of 56 patients. The mean age of the 23 men and 33 women was 71 years (range 48 to 84 years). Two patients were excluded. Of the remaining, 15 patients had predominantly nuclear sclerotic cataracts, 13 had cortical cataracts, 11 had posterior subcapsular cataracts, and 15 had mixed cataracts. Correlations between devices were low. The highest correlation was between PSF meter measurements and Scheimpflug measurements (r = 0.32). The best correlation between corrected distance visual acuity was with the PSF meter (r = 0.45).
Conclusions:
Forward and backward light-scatter measurements cannot be used interchangeably. Scatter as an aspect of quality of vision was independent of acuity. Measuring forward light scatter with the straylight meter can be a useful additional tool in preoperative decision-making.
