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T. Lamba, R. K. Grewal; Intraocular Pressure and Aqueous Outflow Facility in Diabetes Mellitus. Invest. Ophthalmol. Vis. Sci. 2008;49(13):1066.
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The purpose of this study was to correlate the intraocular pressure (IOP) and aqueous outflow facility in diabetics with the severity of retinopathy, thereby determining whether diabetes affects the anterior circulation of the eye as it affects the posterior(retinal) circulation.
A total of 150 eye with diabetes were included in the study, while 50 normal age matched subjects were taken as controls. The diabetic patients were divided into three groups to include 50 with no retinopathy, 50 with background/non proliferative diabetic retinopathy(NPDR), and 50 with pre-proliferative or proliferative retinopathy(PDR). IOP was measured by applanation tonometry. Aqueous outflow facility was measured by Schiotz tonography with reference to the simplified tonography table.
The mean IOP in diabetic subjects without retinopathy and with background/non proliferative diabetic retinopathy was found to be higher i.e. 16.16mm Hg and 15.92 mm Hg respectively, as compared with the control group (i.e. 13.70 mm Hg) and the difference was highly statistically significant (p<0.001). On the other hand, the subjects with pre-proliferative/PDR were found to have a mean IOP of 11.12 mm Hg, which was lower than all the other three groups, the difference being highly statistically significant (p<0.001). This shows that there was an increase in the IOP in the diabetic subjects as long as the retinopathic changes were absent or mild. The IOP, however, was seen to fall to levels even lesser than those of controls in the patients with more severe retinopathic lesions. The mean aqueous outflow facility in all the diabetic groups was lower than that of the control group, but this was not statistically significant (p>0.05) except in the pre-proliferative/PDR group where the outflow facility was lower compared to all the other groups and this difference was highly statistically significant (p<0.001).
From the above study we concluded that diabetes was associated with an increased IOP as long as there was no retinopathy or background diabetic retinopathy. However, the development of preproliferative/proliferative diabetic retinopathy was found to be associated with a lower IOP, thus indicating that a higher IOP has a protective effect against advanced diabetic retinopathy. Since the aqueous outflow facility in all the diabetic groups was well within the normal range with no significant difference among them, it does not seem to have any effect on diabetic retinopathy.
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