Case series about physiological astigmatism and the impact of pterygium surgery

Pterygium is a benign conjunctival fibrovascular neoformation progressively encroaching on the cornea, it can cause corneal distortion and induce astigmatism, or aggravate pre-existing physiological astigmatism, which is defined as ≤ 0.50 D and not requiring optical correction. The radical treatment of pterygium is purely surgical, with conjunctivo-limbal grafting and conjunctival autografting emerging as the surgical techniques of choice. The main objective of the study was to investigate whether pterygium surgery does not worsen the preoperative physiological astigmatism.

This is a prospective cohort study conducted in the ophthalmology department of the Mohammed V Military Hospital in Rabat over a period of 12 months, including 43 stage II/III/IV pterygia that were operated on by conjunctival autograft by the same surgeon. First, we looked for an association between pterygium surgery and variations in astigmatism. For quantitative variables we used the Wilcoxon test. In a second step we split the file into two distinct groups according to the value of preoperative astigmatism≤ 0.5 D or >0.5 D in order to detect the impact of pterygium surgery on physiological astigmatism. Statistical analysis of the data was performed by comparing the distribution of these characteristics.

The median astigmatism was 1 D (0.25; 2.50). 35% of our population had preoperative astigmatism ≤0.5 D. The Wilcoxon test showed that there was a statistically significant difference between preoperative and postoperative astigmatism (p = 0.001). The paired sample T-test showed no statistically significant difference between the preoperative and postoperative outcome in the physiological astigmatism population (p = 0.53).

Many studies have shown the benefits of pterygium excision on astigmatism, but few studies have specified the impact of this surgery on physiological astigmatism. Our study showed that pterygium surgery does not alter physiological astigmatism.