Corneal nerve alterations in diabetes mellitus

The morphologic status of corneal innervation was studied in rats with streptozocin-induced diabetes. Animals were killed at 1, 4, 16, and 36 weeks. Corneal innervation was studied by light and electron microscopy using nonspecific cholinesterase reaction, gold chloride impregnation, and plastic-embedded sections. Increased irregularity in the periodicity of nerve fiber beading was observed in diabetic corneas with gold impregnation. Ultrastructural evidence of irregularities in the basal lamina of Schwann cells was demonstrated in 16- and 36-week-old diabetic animals, along with occasional axonal degeneration. These alterations constitute a constellation of early pathologic manifestations in the innervation of diabetic cornea. To our knowledge, this study represents the first demonstration of neural changes in diabetic corneas as well as nerve fiber changes in an avascular tissue in diabetes

Correlations Among Upper and Lower Tear Menisci, Noninvasive Tear Break-up Time, and the Schirmer Test

To determine the relationships among tear meniscus parameters, noninvasive tear break-up time (NITBUT), and the Schirmer test. Experimental study. Thirty-six subjects were tested on one randomly selected eye. Real-time corneal optical coherence tomography (OCT) was used to image the upper and lower tear menisci during normal and delayed blinking followed by measurement of NITBUT and the Schirmer test. Digital images of the eye were taken for measuring the lid lengths to estimate tear volume in the menisci. Compared with normal blinking, significant increases of tear menisci occurred during delayed blinking (post hoc, P < .01). NITBUT was weakly but significantly correlated with the height ( r = 0.36; P = .03) and area ( r = 0.37; P = .03) of the lower tear meniscus during normal blinks. NITBUT was also correlated with the lower tear meniscus volume ( r = 0.45; P < .05) and total tear meniscus volume ( r = 0.43; P < .05) during normal blinking. The Schirmer test was not significantly related to any parameters of the tear menisci, volumes, or NITBUT; however, it was negatively correlated with the age of the subjects ( r = −0.47; P = .004). The age was negatively correlated with the upper tear meniscus ( r ranged from 0.36 to 0.37 for the radius, height, and area, P < .05) measured during delayed blinking. NITBUT appears correlated with the lower tear meniscus during normal blinking, and the Schirmer test appears not correlated with the noninvasively measured tear meniscus

Extended wear contact lenses using high water contact lenses in aphakia

This article does not have an abstract

Effect of Blinking on Tear Volume After Instillation of Midviscosity Artificial Tears

To determine by optical coherence tomography (OCT) the effect of blinking on ocular surface tear volume after instillation of artificial tears. Experimental study. Normal human eyes (n = 21) were imaged to obtain dimensions of the tear film and menisci during blinking. The imaging was carried out immediately and five minutes after the instillation of 35 μl midviscosity artificial tears (1.0% carboxymethylcellulose; Refresh Liquigel; Allergan, Irvine, California, USA). The exposed ocular surface area and the lid lengths were used to calculate the volumes. Immediately after the instillation, total tear volume was increased ( P < .001) compared with five minutes after the instillation, with the major increases in the lower tear meniscus volume and tear film volume. After the instillation, blinking caused tear loss in total tear volume because of the decrease of the lower tear meniscus volume ( P < .05). In contrast, blinking increased the tear film volume ( P < .05). At the end of the eye-opening period, tear film volume decreased and lower tear meniscus volume increased significantly ( P < .05), with no significant changes in total tear volume ( P > .05). During the blink cycle immediately after the instillation, net loss was evident in tear film volume, lower tear meniscus volume, and total tear volume ( P < .05). Blinking plays a crucial role in distribution and removal of instilled tears. When the tear system is overloaded, the increase in blink output helps restore balance

Normal human corneal epithelium

A new contact wide-field specular microscope was used to examine and photograph the normal in vivo appearance of human superficial corneal epithelium. The cells were polygonal in structure and were divisible into bright and dark groups on the basis of their appearance. Intracellular detail, including the nuclear outline, was often discernible along with microscopic debris in the overlying tear film

Corneal stromal innervation: a quantitative analysis of distribution

The density of stromal nerve trunks and their branches was determined at the peripheral and the central areas of the four corneal quadrants in the Long-Evans hooded rat by using a nonspecific cholinesterase histochemical reaction. It was found that the density of stromal innervation is the same in the different quadrants and in the 2 eyes of the same animal. However, the density of stromal innervation was higher at the periphery that at the center of the cornea. The study provides quantitative information on the density of corneal stromal innervation in a commonly used laboratory animal. These data were unavailable in the literature, and can be used as a baseline for experimental studies