Cyclocryotherpay and noncontact Nd:YAG laser cyclophotocoagulation in cats.

PURPOSE: To investigate physiological and histologic alterations of the cat eye in response to cyclocryotherapy (CCT) and noncontact transscleral Nd:YAG laser cyclophotocoagulation (TSNYC). METHODS: One eye of 29 cats was treated with 12 applications (1 minute, -80 degrees C) of CCT or 80 applications of noncontact TSNYC (7 to 9 J, retrofocus 3.6 mm). Blood-aqueous barrier function was studied measuring aqueous protein and fluorescein concentration after intravenous dye injection. Ocular blood flow was determined using 85Sr microspheres. RESULTS: Intraocular pressure after CCT was 29% lower in the treated than in the control eye after 3 and 12 weeks. After TSNYC, pressure was reduced by 34% at 3 weeks and by 27% after 12 weeks. Aqueous protein concentration was elevated in all treated eyes. Neither technique altered tonographic outflow facility or episcleral venous pressure. Calculated aqueous flow was lower in the treated eye than in the control eye 3 and 12 weeks after each cyclodestructive procedure. After CCT, anterior chamber fluorescein concentration was 2.5 times greater in 3-week and 3 times greater in 12-week eyes. After TSNYC, fluorescein concentration was 3 and 3.5 times greater at 3 and 12 weeks, respectively. Ciliary body blood flow in control eyes was similar to CCT and TSNYC eyes. Histopathology 12 weeks after CCT and TSNYC showed pigment dispersion, disorganized architecture, and cystic elevation of the nonpigmented ciliary epithelium. Areas of absent pigmented and nonpigmented epithelium at the ciliary process base were more discrete in TSNYC eyes. Electron microscopy demonstrated normal junctional complexes. CONCLUSIONS: CCT and TSNYC lower pressure by reducing aqueous formation. Ciliary body blood flow is not altered after either technique. Both techniques result in similar histologic disruption of the ciliary epithelium, resulting in breakdown of the blood-aqueous barrier.

Apraclonidine and anterior segment laser surgery. Comparison of 0.5% versus 1.0% apraclonidine for prevention of postoperative intraocular pressure rise.

PURPOSE: To compare the efficacy of 0.5% and 1.0% apraclonidine in preventing laser-induced intraocular pressure (IOP) elevation after trabeculoplasty, neodymium: YAG (Nd: YAG) iridotomy, and capsulotomy. METHODS: This is a prospective, masked, and randomized study of 83 patients undergoing trabeculoplasty, 62 patients undergoing iridotomy, and 57 patients undergoing capsulotomy. Surgical eyes received one drop of 0.5% or 1.0% apraclonidine immediately after surgery. RESULTS: Intraocular pressure reduced 2 hours after trabeculoplasty in the 0.5% (P = 0.028) and 1.0% (P = 0.004) groups. Intraocular pressure was higher than baseline in a greater number of eyes treated with 0.5% (12 of 39 eyes, 31%) compared with 1.0% apraclonidine (5 of 44 eyes, 11%) (P = 0.032). Intraocular pressure in eyes with a narrow chamber angle was reduced in 16 (85%) of 19 eyes treated with 0.5% and in 10 (84%) of 12 eyes treated with 1.0% apraclonidine after iridotomy. Of patients with chronic angle-closure glaucoma, IOP was similar to prelaser values in 11 (69%) of 16 eyes treated with 0.5% (P > 0.7) and 12 (80%) of 15 eyes treated with 1.0% apraclonidine (P > 0.3). In patients undergoing capsulotomy, pressure was significantly lowered in the 0.5% group (P = 0.04) but not in the 1.0% apraclonidine group. After capsulotomy, both treatment groups had similar (P > 0.3) numbers of eyes with an IOP less than baseline (83% for 0.5% apraclonidine and 81% for 1.0% apraclonidine). CONCLUSION: The single postoperative administration of 0.5% apraclonidine is as effective as the 1.0% concentration in preventing IOP elevation immediately after trabeculoplasty, iridotomy, or capsulotomy.

The effect of acute changes in blood glucose on lenses in diabetic and non-diabetic subjects using quasi-elastic light scattering spectroscopy.

Quasi-elastic light scattering spectroscopy was used to non-invasively monitor affects of transient blood glucose changes on lenses of non-diabetic subjects undergoing glucose tolerance testing and diabetic subjects undergoing glucose clamping protocols. Non-diabetic subjects exhibited a characteristic biphasic change in lens protein diffusion coefficient in response to glucose loading. There was an initial rapid decrease in diffusion coefficient followed by an increase to a maximum attained approximately 30 minutes after peak blood glucose levels had been reached. The diffusion coefficients then returned to baseline values approximately 60 minutes later. These changes in diffusion coefficient in the non-diabetic lens may be related to changes in lens hydration in response to glucose loading. Diabetic subjects, in contrast, did not exhibit a marked change in diffusion coefficient in response to acute blood glucose level changes. This may be attributed to an osmotic buffering in the diabetic lens which could offset the transient changes in aqueous glucose levels.