Objective: The light scattering intensity of normal, clear lenses varies with age and with the localization within the lens. Realizing the biometry of single lens areas together with their relevant light scattering intensity one should be able to calculate an index to express the lens transparency properties of normal human lenses in dependence on age. Performing the same procedure in cases of diabetic patients with still clear lenses it should become possible to obtain an index for the lens transparency properties of lenses under the ‘risk factor’ diabetes. Methods: 748 eyes with transparent lenses in 383 healthy individuals and 134 eyes with clear lenses in 70 subjects with diabetes were examined. Scheimpflug slit images of the lens were documented by a Nidek EAS-1000 instrument. Biometry for measuring the distance of the single lens layers from the anterior capsule and densitometry for determining the light scattering intensity of six defined lens layers along the (theoretical) optical axis were performed. The index of the lens transparency properties was calculated using the light scattering intensity of a defined lens layer and its distance from the anterior capsule. Results: Lens thickness and light scattering intensities increased linearly with increasing age in the normal population as well as in the diabetic patients. The densitogram pattern of the light scattering intensities in the defined representative six points was similar in both populations, but in the diabetic group the lens thickness was larger and the light scattering intensities were higher at all ages. Conclusion: The index of lens transparency properties calculated with the light scattering intensities of a certain lens area and its distance from the anterior capsule is a useful measure of lens clarity in dependence on age. ‘Clear’ lenses of the diabetic population show significantly higher indices for the lens transparency properties in all age groups.

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Purpose: To confirm whether long-term administration of prednisolone sodium succinate (prednisolone) alone is able to induce cataract in rat eyes. Materials and Methods: A 1% solution of prednisolone was administered topically as eye drops to Brown Norway rat eyes, and a systemic pulse administration of 10 mg/kg/day was given via the tail vein. Both administration methods were applied in different combinations. Eighty-three 6-week-old male rats were divided into 8 groups: group 1 = control; group 2 = topical instillation every day; group 3 = single pulse; group 4 = single pulse + eye drops; group 5 = 3 times pulse; group 6 = 3 times pulse + eye drops; group 7 = 3 times pulse per 2 months; group 8 = 3 times pulse per 2 months + eye drops. Observations for changes of lens transparency were made by slitlamp microscopy and documented by an anterior eye segment analysis system (Nidek EAS-1000^®) from the onset of drug administration to a maximum period of 16 months. Results: Lens opacity in the shallow anterior and posterior lens layers developed from the tenth month following commencement of prednisolone administration. The incidence of anterior and/or posterior cortical cataract at the sixteenth month was 15% in group 2, 12.5% in group 5, 25% in group 6, 17.9% in group 7 and 35.3% in group 8. The lenses of groups 1, 3 and 4 maintained their transparency throughout the observation period. Light scattering intensity in groups 8 and 7 was the highest, followed by groups 6 and 5, then groups 2, 4, 3 and 1. Conclusion: Cortical cataract was successfully induced in Brown Norway rat eyes by sustained administration of prednisolone succinate alone applied as systemic pulse.

Purpose: To predict the postoperative anterior chamber (AC) depth from the preoperative in situ position of the lens central clear zone (CCZ) using Scheimpflug slit photography. Methods: 111 eyes of 78 cases that underwent phacoemulsification and intraocular lens (IOL) implantation were examined. 748 eyes of 383 healthy subjects with transparent lenses were used as the control. Scheimpflug slit photography was done under maximal mydriasis, and biometry was performed on the photographs. Two types of acrylic IOLs (MA30BA and MA60BM, both from Alcon) were used in this study. The preoperative AC depth (L1), the distance between the anterior lens capsule and lens CCZ (L2) and the postoperative AC depth (I1) were determined. I2, the predicted postoperative AC depth, was then determined from a linear regression of L1 + L2 and I1. Results: L2 thickened by 0.014 mm/year, and L1 decreased by 0.016 mm/year in the transparent lenses. L1 + L2 changed little with aging in both cataractous and transparent lenses. L1 + L2 and I1 showed a linear correlation with r = 0.80 in the MA30BA and r = 0.77 in the MA60BM groups. The mean error values between I1 and I2 were 0.095 ± 0.096 and 0.123 ± 0.114 mm in MA30BA and MA60BM, respectively. The error between I1 and I2 was within ± 0.17 and ± 0.33 mm or less in 72.9 and 91.5% of MA30BA and in 82.7 and 96.2% of MA60BM. In contrast, the error between I2 and I1 when calculated using the SRK/T formula was much larger – in excess of ± 0.33 mm in 38.7% of the eyes. Conclusions: L1 + L2 changes little with aging and is considered a useful marker of the position of the crystalline lens in situ. There was a high correlation between I1 and L1 + L2. These allow a far more accurate prediction of I1 than previous methods. In combination with the conventional regression formula and ray tracing, a highly accurate IOL power calculation can be attained.