Corneal thickness and endothelial density before and after cataract surgery

Abstract

Background/aims - Deturgescence of the corneal stroma is controlled by the pumping action of the endothelial layer and can be monitored by measurement of central corneal thickness (pachymetry). Loss or damage of endothelial cells leads to an increase in corneal thickness, which may ultimately induce corneal decompensation and loss of vision. Little is known about the effect of moderate reductions in endothelial cell number on the thickness of the corneal stroma. This study aimed to investigate this matter further using patients who had incurred moderate decreases in their endothelial cell counts as a result of cataract surgery. Methods - Central corneal thickness was measured 1 day before surgery, 1 day after surgery, and again at 3 months or 1 year. Endothelial cell counts were also performed 1 day before surgery and thereafter at 3 months or 1 year after surgery. The relationship between these two parameters was assessed statistically. Precise measurements of central corneal thickness were made by optical low coherence reflectometry. For comparative purposes, this parameter was also determined by ultrasonic pachymetry. Central corneal endothelial cell numerical density was estimated on photomicrographs taken with a specular microscope. Results - All patients had significant post-operative corneal swelling on the day after surgery; preoperative values were restored by 3 and 12 months, even though significant endothelial cell losses had occurred. No correlation existed between central corneal thickness and central corneal endothelial cell numerical density. Measurements estimated by ultrasonic pachymetry were more variable and significantly higher than those determined by optical low coherence reflectometry. Conclusion - As long as the numerical density of the corneal endothelial cells does not fall below the physiological threshold, a moderate decrease in this parameter does not compromise the pumping activity of the layer as a whole.