Quantitative Measurement of Crystalline Lens Opacification

Abstract

Purpose: : To identify a quantitative measure of crystalline lens light characteristics that may provide insight into cataract progression over time.

Methods: : Archived fundus images from 105 phakic and 104 pseudophakic eyes with stable open angle glaucoma underwent retrospective analysis. A Zeiss FF4 fundus camera and Topcon TRC 50 VT fundus camera/Nikon D2 digital camera back were used. Standardized regions within the optic cup, disc, and vessels were analyzed for their spectral characteristics using Adobe Photoshop^® CS2. Eyes with cortical or posterior subcapsular cataracts and capsular opacities were excluded.

Results: : Of the ten spectral characteristics analyzed, blue light value showed the greatest difference between phakic and pseudophakic eyes when measured in the optic cup, disc, and vessel. Mean blue value in the cup of phakic patients was significantly less than that of pseudophakic patients (79.7±43.77 vs 105.6±36.5; p=0.01). No difference was noted when comparing clear phakic and pseudophakic lenses (91.5±44 vs 105.6±36.5; p=0.16). Analysis within the phakic population found differences in blue values between patients with 0+NS and 1+NS (91.5±44 vs 56.8±36; p=0.0001). There was little association between 0 and 2+NS (91.5±44 vs 67±43.3; p=0.08) and no association between 1+ and 2+NS (56.8±36 vs 67±43.3; p=0.48). Overall, phakic patients without opacification had blue values greater than phakic patients with opacification, 91.5±44 and 59.7±35.7 (p=0.00002).

Conclusions: : Our analysis reveals that there are quantifiable differences in spectral light characteristics between phakic and pseudophakic eyes. Blue light absorption was shown to be inversely associated with increasing lens opacification. Major limitations of this study were the subjective grading of crystalline lens opacity and variable use of camera flash, more accurate identification and revised imaging protocol may improve the spectral correlations. These findings may aid in the development an objective cataract grading scale to improve correlation with visual symptoms, clinical diagnosis, and assessment of longitudinal progression.

Keywords: cataract • imaging/image analysis: clinical • optical properties