© 2014 Elsevier Ltd.Objective: Acromegaly has various impacts on many organs. The ophthalmologic effects of acromegaly have not yet been investigated in detail. The aim of the current study was to evaluate qualitative and quantitative changes in corneal endothelial cells and central corneal thickness (CCT) of the patients with acromegaly. Design: In this prospective, cross-sectional study, 128 eyes of 64 patients with acromegaly (female/male. =. 40/24) and 208 eyes of 104 age and gender-matched healthy volunteers (female/male. =. 69/35) were included. Endothelial cell density (ECD), cellular area (CA), coefficient of variation (CV) in cell size, percentage of hexagonal cells, and CCT were measured in patients with acromegaly and in healthy volunteers using the noncontact specular microscopy (SP-3000P: Topcon Corporation, Tokyo, Japan). Results: ECD and CA were lower in cases with acromegaly than in controls (ECD in acromegaly: 2615.65 cell/mm2 and in controls: 2700.35 cell/mm2; p=0.002. CA in acromegaly: 382.30μm2 and in controls: 400.30μm2; p=0.02). In the entire group with acromegaly, the time elapsed since diagnosis was positively correlated with CA and was negatively correlated with ECD (r=+0.39, p=0.001 and r=-0.42, p=0.001). Conclusions: The endothelial layer of the cornea may be under risk of impairment with prolonged disease duration in acromegaly. Consistency of the corneal endothelium should be also sought during long-term follow-up of the cases with acromegaly.