Abstract
BackgroundMicrovascular complications, including retinopathy and nephropathy are seen with type 1 diabetes. It is unknown whether functional changes in aqueous humor flow or intraocular pressure (IOP) develop in parallel with these complications. This study was designed to test the hypothesis that clinical markers of microvascular complications coexist with the alteration in aqueous humor flow and IOP.MethodsTen patients with type 1 diabetes and ten healthy age- and weight-matched controls were studied. Aqueous flow was measured by fluorophotometry during a hyperinsulinemic-euglycemic clamp (insulin 2 mU/kg/min). Intraocular pressure was measured by tonometry at -10, 90 and 240 minutes from the start of the clamp, and outflow facility was measured by tonography at 240 minutes.ResultsDuring conditions of identical glucose and insulin concentrations, mean aqueous flow was lower by 0.58 μl/min in the diabetes group compared to controls (2.58 ± 0.65 versus 3.16 ± 0.66 μl/min, respectively, mean ± SD, p = 0.07) but statistical significance was not reached. Before the clamp, IOP was higher in the diabetes group (22.6 ± 3.0 mm Hg) than in the control group (19.3 ± 1.8 mm Hg, p = 0.01) but at 90 minutes into the clamp, and for the remainder of the study, IOP was reduced in the diabetes group to the level of the control group. Ocular pulse amplitude and outflow facility were not different between groups. Systolic blood pressure was significantly higher in the diabetes group, but diastolic and mean arterial pressures were not different.ConclusionsWe conclude that compared to healthy participants, patients with type 1 diabetes having microalbuminuria and retinopathy have higher IOPs that are normalized by hyperinsulinemia. During the clamp, a reduction in aqueous flow was not statistically significant.
Highlights
Microvascular complications, including retinopathy and nephropathy are seen with type 1 diabetes
We previously reported that aqueous flow was decreased by 15% in patients with type 1 diabetes without evidence of microvascular complications, compared to healthy control participants [3]
This study examines aqueous flow under conditions of hyperinsulinemia and euglycemia in eyes of patients with type 1 diabetes with evidence of retinopathy and microalbuminuria and eyes of healthy non-diabetic age-matched controls
Summary
Microvascular complications, including retinopathy and nephropathy are seen with type 1 diabetes. It is unknown whether functional changes in aqueous humor flow or intraocular pressure (IOP) develop in parallel with these complications. The production rate can be assessed by measuring the aqueous flow rate from the posterior chamber into the anterior chamber. We previously reported that aqueous flow was decreased by 15% in patients with type 1 diabetes without evidence of microvascular complications, compared to healthy control participants [3]. Measurements were made under rigorous conditions utilizing a hyperinsulinemic-euglycemic clamp Such conditions were necessary to control insulin and glucose concentrations in both study groups during the measurements, as these factors could impact vascular blood flow, an important determinant of aqueous flow [5,6,7]. Other published studies did not control for the levels of insulin and glucose during the assessment of aqueous flow [2,4,6] making it difficult to separate the disease effect from the effect of insulin and glucose
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