Measurements of lens transparency or its disturbances by densitometric image analysis of scheimpflug photographs

Abstract

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.

External factors in the development of cataract

“…Implementing Scheimpflug and retroillumination digital photography with computerised analysis of lens opacities has allowed progression of cataract to be measured with great precision. [71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88] This method, cost effective for the large epidemiological studies, 89 is probably the best technique for recording cataract changes.…”

Spatial distribution of back scattering in the nuclear area of the non-cataractous human lens

“…The film (Kodak TX 5063) was devel oped according to a standard method. 2 The spatial distribution of back scattering in the nucleus was measured with a modified Leitz microscope pho tometerl5 equipped with a recording device that allowed two-dimensional positioning of the measuring area with a micrometer resolution. The measuring area was 0.2 x 0.2 mm in the object plane, and the linear magni fication was 30 times.…”

An Index for Human Lens Transparency Related to Age and Lens Layer: Comparison between Normal Volunteers and Diabetic Patients with Still Clear Lenses

“…Shibata et al [1,2] measured the thickness of transparent lenses in Japanese and German subjects and found that the thickness of a transparent lens increased 0.02 mm per year in both groups. It was also reported that the light scattering intensities of single lens layers increased with aging [3][4][5][6][7][8][9]. From these changes, we proposed a concept for 'lens age' as an indicator of lens transparency in an individual lens [8].…”

“…Several studies evaluated the changes with aging of lens thickness and light scattering intensity using Scheimpflug photography [1][2][3][4][5][6][7][8][9] and the reliability of this method has been widely accepted. Shibata et al [1,2] measured the thickness of transparent lenses in Japanese and German subjects and found that the thickness of a transparent lens increased 0.02 mm per year in both groups.…”