Abstract
Abstract: :
Purpose: As glucose concentrations in aqueous humor (aq) and blood plasma (pl) are known to be correlated [3], it seems to be feasable to monitor blood glucose levels by determining the glucose concentrations in the anterior chamber (AC) of the eye with near infrared spectroscopic methods in diabetic subjects[1]. For this non-invasive method, knowledge of the ratio (R=aq/pl) of glucose and other substrates (e.g. lactate) with possible influence on glucose measurements is necessary [2]. Methods: In 9 fasting patients with diabetes mellitus (type I or II) and 36 non diabetics scheduled for cataract surgery (CS) or pars plana victrectomy (PPV) pl and aq were sampled to determine lactate (lac) and glucose (glc) concentrations (glucose-/lactate-oxidase and peroxidase-method, dry chemical analysis). Exclusion criteria were inflammatory eye disease, recent intraocular surgery and impurities of aqueous humor. Samples of blood plasma were drawn few minutes before and 0.1 ml of aqueous humor at the beginning of surgery. Results:For all 45 samples the mean lactate concentration was 4.92±1.44 mmol/l in the AC and 1.12±0.37 mmol/l in the blood. The mean ratio R(lac) = aq/pl = 4.59. The mean glucose level was 3.02±1.30 mmol/l in the AC and 5.97±1.60 mmol/l in the blood, the mean ratio R(glc) was 0.51. In the diabetic group R(lac) was 5.23±1.74 (SD; range 3.27 - 7.91), R(glc) measured 0.56±0.13 (range 0.32 - 0.72). For 36 non-diabetics R(lac) was 4.43±1.32 (range 1.86 - 8.33) and R(glc) was 0.50±0.08 (range 0.40 - 0.64). The proportion of lactate/glucose concentrations in the AC was 1.78±0.73 with a broad range (0.67 - 3.13) and no difference between diabetics and non-diabetics. Conclusion: Lactate concentrations in the anterior chamber of the human eye were measured simultaneously with glucose concentrations for the first time. They vary largely between individuals and are not closely correlated to the AC glucose levels. It needs to be ruled out with artifical AC-fluids, whether these variations may interfere with noninvasive glucose measurements in the AC. Ref: 1. Backhaus J, Böcker D, Schrader B, Schrader W, Menzebach HU , Schmidt E (1996) US Patent 5 535 743. 2. Schrader WF (1998) Invest. Ophthalmol. Vis. Sci. 39: S926. 3. Schrader WF, Grajewski RS , Meuer P (2000) Invest. Ophthalmol. Vis. Sci. 41: S77 Acknowledgements: Central laboratory at the Univ. of Würzburg for the determination of lactate and glucose levels
Keywords: 324 aqueous • 387 diabetes • 317 anterior chamber