Mark P. Nasisse

The lens influences aqueous humor levels of transforming growth factor-β2

Abstract · Background: Transforming growth factor-beta 2 (TGF-β2) is a pluripotent cytokine which has been suggested to play a number of roles in ocular physiologic and pathologic states. Intraocular fluid (IOF) levels of TGF-β2 are quite high. Although the sources of ocular TGF-β are not completely defined, the retinal pigment epithelium, the epithelium of the ciliary body and trabecular meshwork cells all secrete it. In this study we utilized canine lens and rabbit ciliary pigmented epithelial cell cultures to quantitate the in vitro secretion of TGF-β2. In addition, the effects of aphakia or the presence of cataractous lenses on IOF TGF-β2 levels were determined. · Methods: Lens and ciliary body epithelial cell culture supernatants and aqueous humors were assayed for total TGF-β2 levels by ELISA and bioassay. · Results: TGF-β2 accumulated in the media bathing lens epithelial cell cultures (0.7 ± 0.03 ng/ml at day 2) and ciliary pigmented epithelial cell cultures (0.8 ± 0.06 ng/ml at day 2) in a time-dependent manner. Surprisingly, aqueous humor from aphakic rabbit eyes contained significantly higher levels of TGF-β2 than their contralateral phakic controls. Furthermore, aqueous humor from canine eyes with cataracts also contained significantly higher levels of TGF-β2 than normal eyes. · Conclusions: These results suggest that the lens secretes TGF-β2 and that the presence and status of the lens may influence IOF TGF-β2 levels.

Surgery for Lens Instability

Lens luxation is a common and potentially blinding disease of dogs. If left untreated, degenerative changes in the pathways for aqueous humor result in glaucoma; however, if the lens is removed by ICLE before significant secondary changes occur, vision can be preserved. In addition, it is now possible to restore excellent vision by replacing the luxated lens with a synthetic IOL.

Principles of Microsurgery

The surgical principles and techniques used in ophthalmic microsurgery differ considerably from those used in general surgery. Successful ophthalmic microsurgery requires that the surgeon understand not only the design and complexities of the operating microscope, but how tissues are affected by minute manipulations with microsurgical instruments. Furthermore, ophthalmic microsurgery requires a detailed understanding of how microsurgical techniques need to be adjusted to accommodate the unique features of ocular tissues such as conjunctiva, cornea, and lens. A diligent effort to master the principles of ophthalmic microsurgery is probably the single most important prerequisite to becoming an accomplished ophthalmic surgeon.

Effects of intracameral administration of α-chymotrypsin on intracapsular lens extraction and postoperative outcome in clinically normal dogs

OBJECTIVE To assess the intraoperative and postoperative clinical effects and histologic effects of intracameral administration of α-chymotrypsin in clinically normal dogs undergoing standard intracapsular lens extraction (ICLE). ANIMALS 6 young adult male dogs without evidence of systemic or ocular disease. PROCEDURES All dogs underwent bilateral ICLE 7 minutes following injection of 75 U of α-chymotrypsin or an identical volume (0.5 mL) of a commercially available balanced saline solution (BSS) into the posterior chamber of the eye. Ease of lens extraction was subjectively assessed and intraoperative intraocular hemorrhage and fibrin accumulation scored. For 27 days after surgery, ocular hyperemia and discharge, chemosis, corneal edema, hyphema, and aqueous flare were scored, and intraocular pressure (IOP) was measured. Thirty days after surgery, histologic evidence of anterior synechia, collapse of and inflammation within the iridocorneal angle, and iritis were scored. RESULTS In 5 of 6 dogs, the surgeon was able to correctly identify the eye treated with α-chymotrypsin on the basis of ease of lens extraction. Mean intraoperative intraocular hemorrhage and fibrin scores for BSS-treated eyes were significantly higher than for α-chymotrypsin-treated eyes. Postoperatively, there were no significant differences between treatments for any clinical variables, including IOP Histologic scores were not significantly different between treatments for any variable. Vision was lost as a result of glaucoma in 1 α-chymotrypsin-treated eye and 1 BSS-treated eye. CONCLUSIONS AND CLINICAL RELEVANCE Intracameral administration of 75 U of α-chymotrypsin 7 minutes before ICLE facilitated lensectomy without apparent adverse effects in clinically normal dogs.