Scheimpflug photography of the anterior eye segment with densitometric image analysis to measure lens transparency has proven its value in long-term follow-up studies of lens changes. The necessary technical conditions of the SL 45 Topcon camera guarantee high reproducibility. The technical control with respect to quality in case of repeated photography is ensured by an internal standard, the camera being equipped with a five-step scale of known density values. External standardization is done by taking the densitometer height of the cornea as standard. The coefficients of variation of internal and external standards were nearly equal (approximately 5%) over the 9-month period of observation of 100 patients (3,200 photos). The coefficients of variation correspond to the standard error found with repeated lens photos of volunteers' eyes evaluated by analysis of variance of the respective data sets. The standard error for distance measurements on the x-axis (cornea thickness, depth of anterior chamber, lens thickness, etc.) is less than 3%. Evaluation of follow-up examinations may most successfully be done by densitometric planimetry, which, in case of follow-up studies on opacified lenses, is superior to the usual measurements of densitometer height. The light scatter registered by Scheimpflug photography is highly individual. This is demonstrated by densitograms of normal lenses of persons of different age groups. Besides linear densitometry, various other procedures of densitometric planimetry are possible. The best results so far were obtained by multilinear densitometry, but the enormous amount of data obtained in this way renders routine application rather difficult.
Experimental cataract development can be objectively monitored in rats by Scheimpflug slit-image photography and microdensitometric image analysis. Zeiss (Oberkochen, Federal Republic of Germany) has developed a new computerized slit-lamp measuring system that works according to the Scheimpflug principle; we have very successfully applied it to rats with streptozotocin-induced cataracta diabetica vera and with naphthalene-induced opacities. With these cataract models we tested the gyrase inhibitor compound, Ciprofloxacin (Bayer 09867), after 6 weeks' daily peroral application (20 mg/kg body weight) for differences in cataract progression indicating a possible cocataractogenic effect of the compound. When we compared the two different Scheimpflug methods, we found that the Zeiss-Scheimpflug measuring system SLC has some handling advantages with respect to animal cataract studies. If the equipment is to be fully used, complements to the program of the integrated computer part are necessary. The image-analytical results from the animals treated with Ciprofloxacin did not show any indication of cocataractogenic potential with respect to cataracta diabetica vera or naphthalene cataract.
Scheimpflug photos of 262 cataract patients, classified according to various forms of opacifications characteristic for senile cataracts were evaluated by biometric methods. The measured values on cornea thickness, depth of anterior chamber, lens thickness, and radii of curvatures of cornea and anterior lens surface show that a correlation between some of the parameters and certain forms of opacities must be assumed.
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