Morphometric Measurement of Pterygium with Anterior Segment Optical Coherence Tomography and Relationship with Astigmatism

Abstract

Purpose: We used anterior segment optical coherence tomography (AS-OCT) to measure the pterygial subepithelial invasion length and thickness before and after surgery, and to evaluate the corneal epithelium and the extent of astigmatism.Methods: This was a retrospective study. Ten eyes that underwent pterygial excision surgery were analyzed. We used corneal topographic data to assess astigmatism before surgery and employed AS-OCT to measure corneal epithelial thickness and the length of subepithelial invasion. We measured the relative pterygial length, width, and area on anterior segment photographs. Corneal topographic assessment and AS-OCT were repeated 1 month after surgery. Multiple regression and Pearson correlation analyses were used to analyze the relationships between normalization of astigmatism and the size and thickness of the excised pterygium.Results: The mean With-the-Rule proportion of preoperative astigmatism was 2.9 ± 2.3 D and the mean corneal epithelial thickness 269.60 ± 84.17 µm. The mean thickness of the excised pterygia was 210.73 ± 80.36 µm. Pterygial thickness was significantly associated with the extent of preoperative With-the-Rule astigmatism and the normalized With-the-Rule astigmatism after pterygial excision. These correlations were stronger than those of the relative pterygial length, width, and area. The mean subepithelial invasion length was 595.00 ± 310.32 µm.Conclusions: An increase in pterygial epithelial thickness influenced the extent of With-the-Rule astigmatism to a much greater extent than did the relative pterygial length, width, and area. AS-OCT measurement of the subepithelial invasion length identifies the required excisional area prior to surgery.