Duration 5min, Q&A 3min
Correlating Retroillumination Images of Lens Opacity Subtype with the Change in Vision
To demonstrate to eye physicians and surgeons the close association between vision deterioration and several lens opacity subtypes, including retrodots, with the latter quantified through retro-illumination photography.
212 eyes from patients with retrodots (a representative subtype of lens opacity) visited the Department of Ophthalmology, Kanazawa Medical University Hospital from April to June, 2013, and were selected for analysis. Their ages and sex distribution were 36-88 (71.1±9.4) years and 45/82=male/female, respectively. Retro-illumination photography was utilized to document lens opacities.
Retro-illumination photography under maximal mydriasis was performed with the Casey Eye Institute (CEI) camera system.The CEI camera system comprises an optical reflex housing paired with a consumer-grade digital camera with pop-up flash. Flash illumination passing through the reflex housing is redirected coaxial to the camera objective lens, resulting in "red-reflex" retro-illumination of the anatomical lens. Patients were positioned in a chinrest and the camera system was attached to an adjustable stage. Focus was set to the iris plane. A supplemental convex lens provided additional magnification of the subject. Two versions of the camera were constructed (Ver. 1 and Ver. 2). Ver. 2 utilized polarization filters to eliminate illumination reflex from the cornea. Analysis was performed on images obtained with Ver. 1. The visual acuity of each patient was taken and recorded in logMar which was then correlated through Point Spread Function analysis with % retinal image contrast. A higher % contrast indicated less retinal masking from light scattering of lens opacities, and lower % contrast suggested more undesirable, vision-degrading retinal masking. Image analysis in all cases was done with Adobe Photoshop® .
Results and Conclusion
To demonstrate the effect of the opacity subtypes locating inside the central 3-mm pupillary area on vision, patients were divided into two groups: one with the total opacity area of >15% of the total pupillary area, and the other, <15% of the total area. Point Spread Function analysis showed that in both groups, there was a nearly linear trend associating less retinal masking (i.e., higher % retinal image contrast) with higher visual acuity. The >15% group was characterized by both lower visual acuity and higher retinal masking, i.e., more vision deterioration, than the <15% group. And all differences between these two groups were statistically significant (P<0.05).
Our results have shown a close association between the subtype opacities with vision deterioration. Retro-illumination photography with our system therefore can yield crucial information useful for decision-making prior to cataract surgery.
[ Keyword ]
retrodot / retro-illumination / cataract / contrast / analysis
[ Conflict of Interest ]