Quantifying the Size of the Pterygium Head by Evaluating the Fibrous Area or the Vascularized Area

Pterygium is characterized by the development of wing-shaped fibrovascular tissue from the bulbar conjunctiva across the limbus onto the cornea. The purpose of this study was to quantify the discrepancy of the pterygium size between the fibrous area and the vascularized area.

Color photographs of 146 eyes with pterygia obtained with a single-lens reflex camera system were analyzed by 2 independent graders for width (vertical dimension), length (horizontal dimension), and surface area of the pterygium head using 2 methods: the fibrous method, which measures any fibrovascular tissue crossing the corneal limbus, and the vascular method, which measures only tissue with discernible active blood flow, without any avascular tissue or opacity. Statistics of intraclass correlation coefficients for intergrader and intragrader reproducibility were calculated, and the paired t test between methods was used.

Both intergrader and intragrader intraclass correlation coefficients for both methods were above 0.85. The vascular measurement was significantly larger in width (vertical dimension, fibrous 3.97 ± 1.02 mm vs. vascular 4.49 ± 1.33 mm, P = 0.01), whereas the fibrous measurement was significantly larger in length (horizontal dimension, fibrous 2.41 ± 1.16 mm vs. vascular 2.23 ± 1.05 mm, P = 0.04). No significant difference was found in the surface area (fibrous 7.27 ± 4.65 mm vs. vascular 7.40 ± 5.13 mm, P = 0.67).

With both methods, reproducibility of the size of the pterygium head was high. Significant differences were shown between the two methods in quantification of the width and length but not in the surface area. Such methods can be used to standardize the evaluation of pterygia in clinical research and clinical trials.