Quantitative morphometry of conjunctival microcirculation in diabetes mellitus

Abstract

The minute vessels of the bulbar conjunctiva were examined by vital microscopy in diabetics and age-matched nondiabetics in order to establish a quantitative index of the vascular changes reported to accompany diabetes mellitus. Photographic enlargements were analyzed by the use of stereological techniques. Initially, microvascular density was approximated by using grid analysis to measure the total length of given-sized microvessels per unit area of conjunctival tissue ( L A). The microscopic blood vessels ranged in diameter from 10 to about 100 μm and were separated into three general categories: total L A of all visible vessels; L A for vessels over 30 μm in diameter (primarily venules); and L A for vessels from 10 to 30 μm in diameter (primarily capillaries and postcapillaries). The patient pool was subdivided into four cohorts, each covering an age span of 15 years. In both diabetics and nondiabetics, the total L A or vascularity increased progressively with age, the primary factor being an increase in the number of venules. An important distinction, however, was that in each of the four age cohorts, diabetics had substantially fewer small vessels.