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To investigate normal light scattering and cataract formation, the anterior eye segments of farmed Atlantic salmon (Salmo salar) reared in fresh water and sea water were documented in vivo for the first time with a Topcon SL-45 Scheimpflug camera. A total of 40 fish from the fresh-water-rearing period, obtained from 2 groups of identical age but showing a different growth rate, and 24 fish from the sea-water-rearing period, sampled from 2 groups with identical age but being fed different food brands, were included in this study. The fish were anaesthetized before examination. Due to the naturally wide pupil, no mydriatic compound was applied. All fish were removed from the water for photography, which was performed for each eye in 0 degrees = vertical slit position. Images were recorded on Kodak Tmax 400 black-and-white film. Microdensitometric image analysis of all negatives was performed using a Joyce-Loebl online microdensitometer. In spite of the virtual absence of an anterior chamber gap between cornea and lens and very little light scattering in the normal fish lens, a small number of distinct layers could be reproducibly identified in the lens. While there was little abnormal light scattering which could point to cataract development in young fish from the fresh water period, the evaluation of the lenses from the 2 sea water groups showed the presence of specific forms of cataract especially in the cortical and supranuclear layers. There were significant differences between the groups fed different food brands at the sea water site. In conclusion, Scheimpflug photography proved to be applicable to eye research in fish in vivo. It is suggested that this method should be employed for reproducible documentation as an extension to slit lamp monitoring in experimental research to reveal causative factors for cataracts in farmed fish., (Copyright 2001 S. Karger AG, Basel)

Background: Light scattering properties of the cornea and lens change in relation to age. This process is influenced by noxious factors which may induce the formation of cataracts. Four different camera types based on the Scheimpflug principle have been developed for documentation and evaluation of light scattering in the eye. Topcon SL-45. Zeiss SLC, Oxford CASE 2000, Nidek EAS 1000. Only the SL-45 and EAS 1000, however, have found a wider application in clinical and experimental studies., Material and Methods: Documentation of the eye with a Scheimpflug system is performed in a dark room after mydriasis induction. The rotating axis of the camera is aligned to the optical axis of the eye with fixation devices. Four meridians have been found appropriate for routine documentation. Image analysis is based on peak height and distance evaluation of 2 layers in the cornea and 10 layers in the lens. Standardization devices allow correction of technical differences in the recording process., Results: Evaluation of the ageing properties of the lens has evidenced typical density developments for each individual layer, the cortex increasing in density earlier than the nucleus. Cataract classification using a Scheimpflug camera provides an objective characterization of cataract type and progression. The outcome of surgical procedures changing the refractive power of the eye can be evaluated with a Scheimpflug camera as well. Its application in studies dealing with the ocular effects of Quinolones and HMG-CoA-reductase inhibitors, has demonstrated that Scheimpflug photography is the method of choice for establishment of a safety profile for a new drug., Conclusions: Scheimpflug photography has proven to be ideal for objective documentation of the anterior eye segment in human and animal eyes, although both documentation and image analysis demand technical expertise to be reproducible.

The density characteristics of the anterior and posterior surfaces of the lens, although of primary importance for its optical quality, are difficult to determine. Scheimpflug photography, however, allows distinct density measurements from the optical axis towards the periphery with the only limitation of a sufficient mydriasis, so that a 3-dimensional scatter profile of both capsular surfaces can be calculated via multilinear densitometric evaluation of a sufficient number of meridians. On this methodical basis, we analysed Scheimpflug images recorded with the Topcon SL-45 on Kodak T-Max 400 film from 25 patients in an age range between 19 and 63 years. Images from the 0 degree + 45 degree meridians were scanned with multilinear microdensitometry and the data computed to get a density profile. In general, most scattering profiles show a marked interindividual variability. Nevertheless, a general trend can be established between the periphery and the center of the anterior and posterior capsules: (a) the anterior capsule generally has a higher density than the posterior; (b) in most cases, the center of the posterior capsule has a higher density than the periphery; (c) the anterior capsule has a more uniform spatial density distribution in all cases. From the cases evaluated, it can be concluded that the density of the peripheral posterior capsule is more importantly influenced by shading effects of the iris, so that geometrical correction is needed.

Lens density has been followed-up in 32 healthy volunteers (mean age 65 years) over a period of 3.5 years. The negatives of Scheimpflug-photos (Topcon SL-45) were evaluated by linear microdensitometry in three measure planes (Joyce Loebl 3 CS). Correlation coefficients, curves of regression as well as calculations of the percentage of density change made obvious, that a minimal increase in lens density occurred in the anterior cortical region.

Ultraviolet (UV) filter photography with the Topcon SL-45 Scheimpflug camera has provided valuable informations about age-related and cataract-type-dependent changes in the spectral properties of the human lens. The present study deals with the same phenomenon in normal lenses of the Brown-Norway rat and in those with true diabetic and naphthalene cataracts. The lenses of all animals of the 3 groups were photographed at the middle and final examination of a 6-week experiment on Kodak Tri-X-pan ASA 400 black-and-white film, using visible light (xenon flash) and UV-filtered light (320-390 nm transmission) from the same light source for recording. The results clearly demonstrate that both cataract models exhibit characteristic fluorescence properties, different from each other and from normal rat lenses. The naphthalene cataract shows the most drastic increase in fluorescence in the cortex, compared to the increase in scattering with visible light. The versatility of the method in preclinical research and the versatility of the cataract models open new aspects of drug-related research in drug toxicity studies.

A double-masked study was performed to investigate a possible side effect of the antiallergic substance Picumast dihydrochloride on lens transparency. 372 patients with Picumast dihydrochloride- or Ketotifen-treatment regularly underwent ophthalmologic examinations and Scheimpflug photography of the anterior eye segment. Results of slitlamp examinations as well as microdensitometric analyzes of the film negatives after one year treatment did not reveal any evidence that Picumast dihydrochloride compromised lens transparency in humans.

Scheimpflug photography has become the basic method for documentation of lens transparency changes in clinical and experimental ophthalmology, due to its high reproducibility. In animal cataract studies, the reproducibility is strongly influenced by the handling characteristics of the camera used, due to limited cooperation of the animal. The reproducibility of the Zeiss SLC system, which offers a direct quality control of the image on the video screen, was tested with 2 animal cataract models, the ultraviolet B (UVB)-induced cataract and the true diabetic cataract in the Brown-Norway rat. 10 rats each of the 2 cataract models and of an untreated control group were photographed in a random order on 3 occasions on the same day by the same photographer. Quality control and densitometry were performed by the same system operator, the measurement window was positioned standardly, coincident with the optical axis of the eye. Statistical comparison was carried out in the capsular layer, that is the area of initial cataract development in both models, and in the cortical layer, into which the diabetic cataract progresses during its later stages of development. The nuclear layer was also evaluated, but has no direct relation to one of the models employed. The results clearly indicate that the reproducibility is predominantly influenced by the homogeneity or inhomogeneity of the cataract model employed. The system operator and the photographer provided that they are well trained, have minor influence on the reproducibility of the Zeiss SLC system.

A double-masked placebo-controlled clinical trial with hard data evaluation by image analysis of Scheimpflug photographs taken at baseline and 6, 12 and 18 months after starting treatment was performed to assess the efficacy of bendazac lysine in four different types of senile cataract. The study had a classical split-plot design. For statistical evaluation, the analysis of variance and covariance for repeated measures were used for three different lens sections: anterior capsule and superficial layer, anterior cortex and nucleus. In the entire group of 53 evaluable patients (without separation into cataract-type subgroups), there was a significantly less increase over time in light scattering (i.e. film blackening) of the anterior cortex and nucleus with bendazac lysine than with placebo. There was also a strong trend in favour of the active drug at the anterior capsular level. Patients with water clefts and spokes showed a significantly less light scattering of the anterior capsule and cortex when treated with bendazac lysine. Those with nuclear changes also showed significantly less light scattering of the anterior cortex and nuclear region with the active drug than with placebo. The number of patients with subcapsular and wedge-shaped (cuneiform) cataracts was too small to be adequately assessed by statistical procedures. Nevertheless, there were indications of a beneficial effect of bendazac lysine on all the lens sections in patients with subcapsular cataracts and on the anterior cortical region in those with wedge-shaped cataracts. In conclusion, this study showed that the increase in light scattering over time, i.e. the progression of cataract, is less in bendazac lysine-treated patients than in those treated with placebo.

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 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.

This article reports on changes in lenses of diabetics, detected by means of Scheimpflug photos. Diabetics aged between 20 and 70 have been undergoing regular ophthalmogical check-ups for 26 months. Linear densitometry of negatives revealed an increase in light scatter at the anterior adjacent clear zone of disjunction (areas 1,2) and the anterior cortex (areas 3,4) in clinically clear lenses over the 26-month period. This change in light scatter is not related to the age of the patients; it is correlated to the duration of diabetes and fasting blood sugar.

Development of experimental cataract can be objectively monitored in rats by application of Scheimpflug photography with the SL 45 Topcon camera and subsequent densitometric image analysis. The method has been used to study naphthalene cataract in Brown-Norway rats (BN-CPB), as well as diabetic cataract induced by streptozotocin injection in Sprague-Dawley rats. The values obtained by linear microdensitometric image analysis allowed precise characterization of the opacification with respect to size, topography, and time progress so that statistical evaluation of the efficacy of certain drugs in prevention or delay of experimental cataracts was possible.

Evaluation of various long-term studies on changes of different lens opacities, as had been rendered possible by microdensitometric image analysis of the film blackening of Scheimpflug photographs, showed that only in a few special cases an extension of the opacification to adjacent lens layers is to be expected within the observation period of 2-3 years. This means that one of the reasons for evaluating the densitometer curve by area planimetry is no longer valid and may be neglected. A further advantage of the measurement of film blackening by height evaluation (height of densitometer deflection above baseline, i.e., noise level) is the fact that it is highly independent of subjective factors and, therefore, ensures a far better reproducibility with respect to data acquisition. The results of both evaluation procedures, obtained by evaluating the identical film material (2 photoexaminations) of 14 volunteers, are presented, and the advantage of height measurement as opposed to planimetry is demonstrated.