The Unique Properties of Tear Film Break-up Process in Patients with Nasal Unilateral Pterygium

Abstract

Significance This study found that the unique properties of tear film break-up process in eyes with pterygium, which, combined with ocular surface parameters, further revealed specific dynamic mechanism. It suggested the thickness of pterygium was especially valuable in deciding the necessity of surgical management. Purpose To explore the dynamics mechanism of tear film instability in eyes with pterygium. Methods A paired-eye controlled cross-sectional study. 78 patients with nasal pterygium were enrolled. Fluorescein tear film breakup was observed. Several key parameters related to tear film quality were defined and analyzed, including total break-up area (mathematically derived from pixel size using MATLAB), break-up velocity, fluorescein break-up time, break-up location and pattern, tear meniscus height (TMH), score of fluorescein corneal staining (SCSF) and meiboscore. Results With comparable TMH, SCSF and meiboscore between paired eyes (P > .05), eyes with pterygium had shorter break-up time, larger break-up area and faster break-up velocity (P < .05). In eyes with pterygium, a positive correlation between meiboscore and pterygium parameters including length, thickness and size were observed (P < .001). As the thickness increased, difference of break-up time and area between paired eyes increased (P = .02 and .046). Eyes with pterygium had more fixed inferonasal break-up location and often presented as dimple break (60.3%) while random break was the most common in contralateral normal eyes (61.5%). A unique break-up pattern named pterygium-induced local dimple break was found. It displayed as irregular but vertical line-like shape appearing after lipid layer spreading, which adjacent to lower margin of pterygium and presented unique properties including inferonasal break-up location, local break-up area, shorten break-up time and faster break-up velocity. Conclusions Eyes with pterygium showed a unique tear film break-up process and novel break-up pattern named pterygium-induced local dimple break. Dynamic mechanism played a significant role in tear film instability of eyes with pterygium rather than aqueous-deficiency and increased-evaporation.