Development of Pseudophakic Model in Young Non-Human Primates

Abstract

Purpose: To develop a model of the pseudophakic eye with and without posterior capsulorhexis in young non-human primates.

Methods: Thirteen male 2-3 year old cynomolgus monkeys underwent intraocular lens (IOL) removal via a 25g vitrector and IOLs were placed in the right eyes. Posterior capsulorhexis was performed in the right eyes of six monkeys at the time of surgery. Eyes were assessed via ophthalmic exams and histopathology and immunochemistry.

Results: Immediate postoperative findings included significant anterior segment inflammation characterized by varying degrees of hyphema, fibrin formation, varying degrees of aqueous cell and flare, a degraded view of the fundus due to fibrin and anterior chamber inflammation, and synechia formation starting few days post surgery. The severity of inflammation in the first animals to undergo surgery necessitated administration of intracameral tissue plasminogen activator and modification of the peri- and postoperative treatment regimen to include systemic steroids, increased duration of topical steroids, addition of topical atropine starting on the day of surgery, and placement of an anterior chamber air bubble at the end of surgery. Inflammation gradually decreased and by 4 weeks post-surgery all pseudophakic eyes had varying degrees of posterior synechia, capsular fibrosis, and peripheral anterior synechia. Other variable findings included incomplete pupil dilation, vitreous to the incisions, vitreous to endothelium, and small anterior synechia. Due to post surgery complications two animals were euthanized approximately 1 month following surgery. One animal developed phthisis bulbi and the other animal developed complete posterior synechia resulting in elevated intraocular pressure. Histopathology revealed capsular and extra-capsule lens epithelial cell (LEC) proliferation associated with posterior synechia and pigment dispersion in the trabecular meshwork membrane. Proliferating LEC showed epithelial to mesenchymal transition including expression of smooth muscle actin.

Conclusions: A pseudophakic model in young NHP was successfully developed. Aggressive peri- and post-operative anti-inflammatory therapy was necessary for successful lens removal and IOL placement. The clinical observation of posterior synechia correlated with LEC proliferation.

Keywords: 743 treatment outcomes of cataract surgery • 567 intraocular lens • 512 EMT (epithelial mesenchymal transition)