Noninvasive glucose monitoring of the aqueous humor of the eye: Part II. Animal studies and the scleral lens.

We have discussed the nature of a scleral lens that will allow us to follow changes in aqueous humor glucose levels in animals by a method based on optical rotation and a technique described in an earlier paper. We have shown how this lens can be micro-miniaturized and can be used in humans as a non-invasive glucose monitor. We have described preliminary experiments designed to show the correlation between the blood glucose assay (BGA) and the aqueous humor glucose concentration as determined by chemical assay (AGA) and by optical rotation determination (ARD). The last mentioned has been obtained by paracentesis directly into a microcell used in conjunction with instrumentation capable of measuring optical rotations as low as 0.0013 degrees (4.5") corresponding to 20 mg/dl glucose with a sensitivity of 0.0001 degrees (0.36"). The variability among normal rabbits as a function of individuality and diurnal changes is described, and the correlation between AGA and ARD shown to be essentially 1.0. Such rabbits are examined when undergoing very rapid decreases in BGA (insulin treatment) or very rapid increases in BGA (bolus of glucose). The AGA and ARD are shown to lag behind the BGA, and this is discussed in terms of the rate of change of BGA with respect to time and its concomitant change in AGA/ARD as well as a simple procedure that would materially reduce this lag.