[Analysis of energy levels for Nd:YAG laser capsulotomy in secondary cataract]

Formation of secondary cataract is influenced by various factors, such as IOL material, IOL design, age, follow-up time and ocular and systemic diseases. It has not yet been studied whether these factors have an clinical impact on the energy used for Nd:YAG laser capsulotomy.

We examined 172 patients, aged 67.3+/-15.9 years, concerning energy levels required for Nd:YAG laser capsulotomy. We analysed the influence of age, implant duration, IOL fixation and ocular conditions on total energy and repetition rate of Nd:YAG laser capsulotomy. Sixty-nine patients (43. 7%) had no other ocular pathology (control), 24 (15.2%) glaucoma, 14 (8.9%) diabetic retinopathy, 12 (7.6%) retinitis pigmentosa, 8 (5. 1%) high myopia, 7 (4.4%) triple procedure with perforating keratoplasty. Twenty-four (15.2%) presented with various additional ocular conditions such as pseudoexfoliation syndrome. Patients had undergone cataract surgery between 1988 and 1995 with implantation of PMMA-IOLs.

Nd:YAG laser capsulotomies were performed on average 28.2+/-17.7 months postoperatively. The average total energy used was 12.7+/-9.4 mJ. Visual acuity (Pre-YAG) was 0.3+/-0.2. In the control group there was no correlation between energy and implant duration or age (P>0.43). 26 patients required a second Nd:YAG laser capsulotomy. Patients with retinitis pigmentosa showed a significantly higher re-YAG rate than the other patient groups (P=0.00059). In eyes with sulcus fixation of the IOL, capsulotomies were performed earlier and with higher energy levels than for in-the-bag fixation.

The different ocular conditions of the anterior and posterior segment showed a different profile for Nd:YAG laser capsulotomy energy level and Nd:YAG laser repetition rate. Sulcus fixation of an IOL resulted in earlier capsulotomies with higher energy levels.