Injuries to the iris and corneal endothelium in intraocular surgeries

The changes in the corneal endothelium at the centre of the cornea were followed after intracapsular cataract extraction and penetrating keratoplasty, by means of specular microscopy and morphometry using a computerized image analyzer. The corneal endothelium undergoes progressive transformation in its size over a period of more than 1 year. In penetrating keratoplasty, progressive increase in the cell size appears to occur over a longer postoperative period. The injury to the iris leaves permanent tissue defects and this is due to insufficient fibroblastic activity of the iris. Iris injury probably initiates synthesis of prostaglandins (PGs) in the human eyes. Topical indomethacin prevents atropine-resistant miosis during aspiration of soft cataract and also reduces intraocular inflammation after intracapsular extraction of senile cataract. It is hypothesized that these responses are related to PG release induced by iris injuries. Topical indomethacin also reduces incidence and severity of the cystoid macular oedema after intracapsular cataract extraction, but systemic administration appears to have little effect. Indomethacin is accumulated in the ciliary processes of rabbits by temperature- and ouabain-sensitive processes and the accumulation is inhibited by probenecid and PGE. It is possible that indomethacin is subject to elimination from the eye by a similar process as are PGs, and this may account for poor intraocular penetration from the systemic route. This justifies topical application of this drug.