The Role of Prostaglandins in the Progression of Diabetic Retinopathy

Overview

Objective of the research study: 1. To measure anterior chamber and vitreous ketorolac (Acuvail®) concentrations after topical administration in patients undergoing routine vitrectomy to determine the ability of the medication to penetrate into the anterior chamber and vitreous cavity, and to compare these levels to the IC50 for the cyclooxygenase-1 and -2 enzymes (COX-1 and COX-2) 2. To measure vitreous concentrations of prostaglandin subtypes (PGE, PGD, PGF) and other inflammatory mediators (Interleukin-1β \[IL-1β\], IL-6, IL-8, tumor necrosis factor \[TNF\]-α, VEGF) in both diabetic and nondiabetic patients undergoing vitrectomy 3. To determine if topical ketorolac (Acuvail®) can penetrate the anterior chamber and vitreous cavity sufficiently to decrease levels of intraocular inflammatory mediators that have been shown to be elevated in diabetic patients 4. To serve as a precursor to a 5-year longitudinal clinical trial to determine if chronically administered topical ketorolac (Acuvail®) can prevent, delay or slow diabetic retinopathy. Research hypothesis 1. Ketorolac (Acuvail®) will penetrate the anterior chamber and vitreous cavity sufficiently to achieve levels above the IC50 for COX-1 and COX-2 2. Prostaglandin and other inflammatory mediator levels in the anterior chamber and vitreous cavity will be significantly higher among diabetic patients than nondiabetic controls 3. Acuvail® can significantly lower anterior chamber and vitreous cavity levels of prostaglandins and other inflammatory mediators in diabetic patients

Patients who require vitrectomy for any indication and those meeting the inclusion/exclusion criteria will be included. Patients will be consented to participate in the study and for surgery. Nondiabetic patients will be included in one of two groups. Twenty will receive topical ketorolac (Acuvail®) preoperatively for 3 days and then samples will be taken at the time of surgery. Twenty other patients will serve as controls for intraocular prostaglandin and cytokine levels (to be compared to diabetic patients). This group will not receive preoperative ketorolac (Acuvail®). Diabetic patients will be included in one of two groups. Twenty patients will have intraocular prostaglandin and cytokine levels measured. Twenty other patients will be in the interventional group to determine if topical ketorolac (Acuvail®) can successfully lower intraocular prostaglandin and inflammatory cytokine levels. In all cases, patients are undergoing vitreoretinal surgery as the surgical treatment of choice for their condition. For this study, undiluted samples will be drawn from the vitreous cavity and anterior chamber at the beginning of the vitrectomy. These samples will be stored, analyzed and frozen. Samples will be tested for prostaglandin levels, in addition to other inflammatory cytokines, and ketorolac levels. Three days of Acuvail® given four times per day was chosen, as previous studies have shown that one dose of ketorolac 0.4% achieves a peak aqueous concentration of 57.5 ng/mL,1 and that 12 doses over two days achieves an aqueous concentration of 1079 ng/mL.2 Both values are well above the IC50 for COX-1 (5.3 to 7.5 ng/mL) and COX-2 (33.9-45.2 ng/mL). The upper end of this dosing spectrum was chosen, as more doses and a longer duration of therapy is likely required to achieve sufficient vitreous levels to inhibit COX-1 and COX-2. This dosing regimen was also used in another clinical study that assessed ketorolac levels and prostaglandin levels in the vitreous cavity after topical administration four times a day for three days preoperatively.3