Digital imaging system for assessing posterior capsular opacification: a preliminary report

Journal Article

2002

Published in: http://onlinelibrary.wiley.com/doi/10.1046/j.1475-1313.2002.00086_33.x/abstract

, H. Al-Farhan1, C. C. Hull1, R. Hameed2, S. E. Horgan2 and E. G. Woodward1 . 2002

Purpose:  Posterior capsular opacification (PCO) is the commonest complication of cataract surgery. The aim of this work is to develop a system that could be used by primary care practitioners to monitor the progression of PCO using familiar equipment.

Methods:  A Kodak DCS 100 (Eastman Kodak, Rochester, NY, USA) digital data back, which uses a Nikon F3 body, was connected to the camera port of a Nikon FS-2 photo slit-lamp. A fixation stimulus was developed and systematic studies carried out to determine optimum exposure and slit-lamp settings using patients recruited from the YAG laser capsulotomy clinic at the Royal Eye Unit, Kingston Hospital. In all cases conventional illumination was used. Inter and intraobserver trials were then carried out using observers ranging from a non-clinician to an experienced ophthalmologist. All images were analysed using ImagePro Plus image processing software prior to statistical analysis.

Results:  Optimum slit-lamp parameters were found to be a 45° slit beam angle, 3 mm slit width and 25× magnification. The flash intensity was set to 2. The optimum camera and digital storage unit speed settings were both ISO 200 for fibrotic PCO but 800 and 1600, respectively, for Elschnig pearl type PCO. Intra-observer repeatability gave ±0.375 mm (95% confidence) variation in fixation. However, initial results from interobserver trials showed significant variability.

Conclusions:  The current digital assessment system uses a standard piece of consulting room equipment coupled to a digital 35 mm camera. Initial results indicate that it should be suitable for use in monitoring PCO although a more exact measurement protocol is required to reduce interobserver variability. Work is currently underway to complete validation trials and to find suitable image statistics.

• Publication Work Type: article
• Volume Number: 22
• Issue Number: 6
• Magazine \ Newspaper: Ophthalmic and Physiological Optics