Histopathologic evaluation of the anterior segment of eyes enucleated due to glaucoma secondary to primary lens displacement in 13 canine globes.

PURPOSE  To describe histologic anterior segment changes in eyes affected with primary lens displacement (PLD) and secondary glaucoma. METHODS  Histologic sections stained with H&E from canine eyes enucleated because of PLD and secondary glaucoma were examined. RESULTS  Thirteen eyes from 12 patients were evaluated. Four dogs were castrated males and eight spayed females. Median age was 8 years of age (range 3-13). Breeds included seven terriers and five other breeds. All eyes examined demonstrated varying degrees of inflammation involving the iris and cleft. Mononuclear and melanophagic infiltration of the cleft was found in all specimens. Four globes also showed polymorphonuclear infiltrate. Pre-iridal fibrovascular membranes were clearly identified in 10 of 13 eyes. Total inflammatory score was significantly greater in all globes examined compared with an age-matched group of normal dogs. The posterior pigmented iris epithelium demonstrated a consistent pattern of hyperplasia and/or hypertrophy and cystic degeneration, more prominent in the more central regions. In some cases, hyperplasia was of greatest severity in the mid-iris and associated with thinning or flattening of the pupillary region. CONCLUSIONS  These results suggest that lens instability may be associated with chronic inflammation and secondary glaucoma. Mechanical irritation from an unstable lens may result in hypertrophy and/or hyperplasia of the posterior pigmented iris epithelium and subsequent cellular exfoliation and release of melanin. An inflammatory reaction directly or indirectly related to melanin release may obstruct the outflow pathways ultimately leading to glaucoma and loss of vision. Use of topical steroids may be warranted in dogs with PLD.