Cataract classification

Abstract

Opacifications of the eye lens--generally defined as cataracts--develop in various different parts of the lens. Therefore, one has to differentiate the types of opacities. For epidemiological studies it is prerequisite to classify the cataracts according to their localization within the lens as well as to the size and intensity of the opacified area. Two approaches have been used in the past: 1) subjective methods of lens observation (based on slit lamp microscopy) and 2) objective methods with measurements of lens transparency or lens opacity respectively based on slit image documentation according to the Scheimpflug principle combined with the retroillumination technique. With ageing, the light transparency of the lens is subjected to considerable changes. Even without the formation of an opacity the transmission of the wavelengths in the UV-B/UV-A and the visible range is diminished. The single lens layers are affected by this phenomenon to different degrees. These changes which might also indicate an early stage of 'cataract formation' cannot be discerned by subjective methods. The densitometric image analysis of Scheimpflug slit images, however, allows the exact measurement of the light scatter in the single lens layers and enables the early recognition of disturbances in transparency which is of crucial importance particularly in cataract epidemiology. In view of our present knowledge the evaluation of risk factors which might be of importance in multifactorial cataract processes will hardly be possible by carrying out prevalence and/or incidence studies involving a single examination of the population. In this case follow-up studies (cohort studies) with repeated examinations are prerequisite. The 'objective methods' for classification alone are able to ensure the necessary reproducibility and the possibility to measure transparency changes in the lens before visible (and therefore subjectively recognizable) opacifications occurred. The methodical procedure with respect to an epidemiological study on the involvement of UV-B radiation in the processes of cataract formation in man requires the application of objective methods for cataract classification.

Changes in the lens epithelium with respect to cataractogenesis—light microscopic and Scheimpflug densitometric analysis of the cataractous and the clear lens of diabetics and non-diabetics

“…Further test parameters were: mean cell density (cells/mm 2 ), mean nucleus area (μm 2 ), mean nucleus volume (μm 3 ), mean cell area (μm 2 ) and nucleusplasma-ratio [23]. Further test criteria were: durability of diabetes, appearance of diabetic retinopathy, classification of cataract types according to the classification originating from the Scheimpflug densitometric method (Scheimpflug camera OCULUS PENTACAM, 12 types of cataract [13]) -the light-scattering intensity of the lens layers was automatically quantified and numerically described with the help of the software (Fig. 1) -preoperative protein content in the anterior chamber (laser flare meter 500 KOWA, non-invasive tyndallometry) as the measure for the disruption of blood-aqueous humour barrier [20], and the blood parameters fasting blood sugar (NBZ) and glycosylated haemoglobin (HbA1c) as well as determination of glucose content in the anterior chamber from the operatively gained material.…”

External factors in the development of cataract

“…Several clinical systems of cataract grading have been suggested. [60][61][62][63][64][65][66][67][68][69][70] Most of them use a set of standard photos of nuclear opacities and assess the proportion of the pupil occupied by the cortical/PSC opacities.…”

Lens Opacities in Valencia, Spain

“…Accepted: March 3, 2011 ORIGINAL ARTICLE type of cataracts (5), depending on the morphology, etiology, when the cataract appears, and stage of development.…”

“…However, when this change diffuses light beams that reach the retina, precluding vision, cataracts are diagnosed. This deterioration depends on the location and degree of opacity the cataract (5) presents. There are several classifications for differentiating diverse…”