[Clinical secondary cataract evaluation in pseudophakic eyes. Method and reproducibility]

According to the literature, the frequency of secondary cataract reported following different studies of posterior chamber intraocular lens (IOL) implantation varies widely. The nonstandardized definition of a clinically significant secondary cataract is one of the reasons for this. We present a morphological scoring system for secondary cataract that does not require visual acuity testing.

Following dilatation of the pupil standardized photographs of the pseudophakic anterior segments were obtained by means of a Zeiss photoslit-lamp (model 40 SL/P). The posterior capsule opacification (PCO) was scored by evaluating retroillumination photographs. The individual PCO score was calculated by multiplying the density of the opacification (graded from 0 to 4) by the area involved behind the IOL optic (calculated between 0 and 1). In order to evaluate the reliability of the morphological scoring system, in experiment A six observers examined photographs of five eyes each (interindividual reliability), and in experiment B the same observers each scored the PCO of three eyes on 5 different days (intraindividual reliability). In experiment C seven different pairs of photographs taken on the same day were scored for PCO by the same observer (influence of photographic variations).

Morphological PCO scores were reliable. With PCO scoring ranging from 0 to 4, interindividual reliability revealed standard deviations between 0.08 and 0.25. The intraindividual reliability showed standard deviations between 0.06 and 0.19 of any individual PCO score. The standard deviation was 0.12 when different photographs of the same eye were scored.

When the entire area behind the IOL optic is evaluated a larger area of the posterior capsule is taken into account than during testing of visual acuity alone. This method revealed high reliability and only minimal investigator-dependent variations. With a standardized photographic set-up, systematic errors otherwise caused by variations in individual photographs of the same eye are insignificant. Use of this method may help in the achievement of more accurate testing for differences in secondary cataract formation with various types of IOL and different surgical techniques.