Presented in Fort Lauderdale, Florida April 2004, sponsored by the Association for Research in Vision and Ophthalmology (ARVO). Published in Invest Ophthalmol Vis Sci 44: 350.

W.J. Donnelly¹, E.J. Sarver², K. Pesudovs¹, J. Marsack¹, N. Bedell¹ and R.A. Applegate¹.

¹ Visual Optics Institute, Univ of Houston College of Optometry, Houston, TX
² Sarver & Associates, Merritt Island, FL

Commercial Relationships: W.J. Donnelly, None, E.J. Sarver, Sarver & Associates C, K. Pesudovs, None, J. Marsack, None, N. Bedell, None, R. Applegate, None.

Grant Identification: NIH/NEI R01 08520

Abstract

Purpose. To quantify forward scattering due to cataract using Shack–Hartmann (S/H) images and use the derived metric to predict visual function (logMAR visual acuity).

Methods. We obtained S/H images from 149 patients in the University of Houston’s Visual Optics Institute Cross–Sectional Cataract Study. Patient age ranged from 22 to 84 years with Lens Opacities Classification System (LOCSIII) nuclear opalescence (NO) scores ranging from 0.8 to 5.6. High–Contrast–Low–Luminance (HCLL) letter visual acuities ranged from 0.0 to 0.6 logMAR. Scattering was described by eight single–valued metrics characterizing S/H lenslet PSF spread using an image thresholding technique and image pixel statistics. For example, the average maximum centroid neighborhood value was assigned the Max_Mean metric. The eight scatter metrics were tested for their ability to predict variance in visual acuity by stepwise multiple linear regression.

Results. As Max_Mean increased HCLL logMAR acuity decreased where HCLL_logMAR = .168 + .004 * Max_Mean; R^2 = .19, P<0.0001. Similarly, as LOCSIII NO increased HCLL logMAR acuity decreased where HCLL_logMAR = .069 + .094 * NO_; R^2 = .391, P<0.0001. Multiple regression using Max_Mean and LOCSIII NO as independent variables improved the ability to predict HCLL logMAR acuity to HCLL_logMAR = 0.002(Max_Mean) + 0.082(LOCSIII NO) + 0.008; R^2 = 0.47, P<0.0001.

Conclusions. An automated, objective, noninvasive method to measure forward light scattering in the lens due to nuclear cataract can be made using S/H images. The Max_Mean metric of forward scatter from S/H images in combination with LOCSIII NO, a metric of back scatter, increases the coefficient of determination. Better metrics may be available and there are ongoing investigations into improving correlations. Supported by: NIH/NEI R01 08520 grant to RAA.