Prevention of complications in pediatric cataract surgery

Abstract

This thesis was performed to find ways to lessen the complications to pediatric cataract surgery, which is an increasingly safe procedure, also in infants. However, there are some complications to the surgery, which threatens the visual development. The most common complication is aftercataract. The most feared complication is secondary glaucoma, which is hard to manage, and can lead to blindness and a cosmetically disturbing eye. The younger the infant is at surgery, the higher the risk of secondary glaucoma, and the more the after-cataract develops. The children must have surgery early in life though, to avoid irreversible amblyopia.

The first study is a retrospective evaluation of a new surgical technique that was developed to inhibit after-cataract. A dry anterior vitrectomy was performed after implantation of the intraocular lens (IOL), through the anterior chamber. The study showed that an anterior vitrectomy was needed in younger children, below the age of seven. In older children, anterior vitrectomy was not necessary. It also showed that an AcrySof IOL seems to be a better choice in the pediatric eye than an HSMPMMA IOL since patients implanted with the first IOL developed less after-cataract.

The second study is a prospective randomised study of the same surgical method used in the first study. Children aged 3-15 years in Ukraine received cataract surgery with posterior capsulorhexis, with or without anterior vitrectomy and were implanted with a singlepiece AcrySof SA30AL IOL. The IOL stayed centered and fitted well into the pediatric eye. Results showed that anterior vitrectomy was advantageous in younger children, approximately below the age of five years, concerning after-cataract.

In the third study we evaluated a single-piece IOL in the small eyes of newborn rabbits, which have an anterior segment approximately the same size as the newborn child. The results showed the AcrySof SA30AT IOL seems to inhibit secondary glaucoma compared to aphakic eyes, lessen the total amount of after-cataract compared to aphakic eyes, and it also makes the eye grow better than most intraocular tenses studied in this animal model.

The cause of secondary glaucoma is yet not fully understood. It might be the strong postoperative inflammatory response in the smallest children that causes synechiae in the chamber angle, thereby the intraocular pressure rises. Treatment with glucocorticoid eye drops would then lessen the secondary glaucoma. However, it is known that treatment with systemic-, peroral-, intranasal- and inhalation glucocorticoids can cause growth retardation in children.

The fourth study in the thesis was performed in the above-mentioned animal model to investigate the effect on growth of topical treatment with glucocorticoids. The results showed that dexamethasone eye drops caused impaired body growth in a dose-dependant way.

In the fifth study the left femurs of the rabbits in the fourth study were analysed with Dual X-ray Absorptiometry and peripheral Quantitative Computerized Tomography to measure different bone parameters. It showed that the glucocorticoid eye drops causes osteoporosis. The rabbits had a dose dependent reduction in bone mineral density, cortical bone mineral content, cortical thickness, femur periosteal and endosteal circumference. This is in accordance with earlier studies when glucocorticoids were given systemically.