Pterygium width may help predict corneal optical disturbance

A study published in BMC Ophthalmology found that the size of a pterygium, specifically its length and width rather than its thickness, was the strongest predictor of declining corneal optical quality.¹

Shen and colleagues, of the First Affiliated Hospital, School of Medicine, at Zhejiang University in Hangzhou, China, conducted a retrospective analysis of 41 patients with unilateral primary nasal pterygium. Pterygium dimensions were captured with anterior segment optical coherence tomography, and corneal refractive power, surface irregularity, and higher-order aberrations (HOAs) were subsequently measured using the Pentacam HR system. Patients with recurrent pterygium, concurrent ocular surface pathology, prior intraocular surgery, or systemic conditions affecting ocular blood perfusion were excluded.¹

Size matters more than depth

Pterygium thickness showed no significant correlation with any measured corneal refractive parameter. By contrast, both length and width correlated significantly with flat keratometry (length: |r| = 0.376-0.473; width: |r| = 0.361-0.415; all P < .05) and, more strongly, with corneal astigmatism (length: r = 0.582-0.642; width: r = 0.529-0.581; all P < .001) across the 3-, 5-, and 7-mm zones.¹ These correlations held steady regardless of how far the analysis zone extended from the corneal apex, a pattern the authors said points to a broader mechanical traction effect from pterygium tissue reaching into the mid-peripheral cornea.¹

Length and width also correlated significantly with corneal irregularity indices, including index of surface variance, index of vertical asymmetry, and index of height decentration. The authors reported a further significant link between width and index of height asymmetry. Neither parameter showed a significant relationship with the keratoconus-specific indices.¹

When optics go off-axis

Pterygium length was positively correlated with total, third-order, and fourth-order HOA root mean square values across the anterior surface, posterior surface, and entire cornea (r = 0.455-0.691, P < .05), driven primarily by vertical trefoil, vertical coma, and tetrafoil. Width correlated with anterior and total corneal HOAs (r = 0.519-0.645, P < .05), though its association with posterior surface aberrations was comparatively weaker (r = 0.313-0.472, P < .05).¹ The authors reported that thickness showed only a single weak correlation, with anterior secondary astigmatism, and no association with any other HOA measure, a finding consistent with a prior comparative study of pterygium and corneal aberrations in fellow eyes.²

Spherical aberration showed no significant correlation with any pterygium size parameter, a finding the authors said may reassure surgeons selecting aspheric intraocular lenses (IOLs) for patients with coexisting pterygium and cataract.¹

A simple measurement with outsized value

The authors proposed that pterygium width, given its ease of standardized measurement at the limbus, could serve as a practical surrogate indicator for predicting pterygium-induced deterioration in visual quality, particularly when length is difficult to assess because of ill-defined apical borders. They suggested that a significantly increased width could prompt clinicians to pursue detailed aberrometry and consider earlier surgical intervention, especially in patients planning refractive cataract surgery or premium multifocal IOL implantation.¹

The study's retrospective, single-center design; moderate sample size; absence of a control group; and cross-sectional structure were cited as limitations. The authors called for prospective, longitudinal studies incorporating standardized surgical protocols to assess the reversibility of pterygium-induced topographic and aberrometric changes following excision.¹

No relevant financial or non-financial competing interests were disclosed by the authors. The study was supported by the Zhejiang Provincial Natural Science Foundation of China.¹

References

1. Shen J, Chen Y, Chen Y, Gou B, Cui H. The influence of pterygium size on corneal refractive properties and higher-order aberrations. BMC Ophthalmol. Published online June 5, 2026. doi:10.1186/s12886-026-05009-y

2. Yoon CH, Seol BR, Choi HJ. Effect of pterygium on corneal astigmatism, irregularity and higher-order aberrations: a comparative study with normal fellow eyes. Sci Rep. 2023;13(1):7328. doi:10.1038/s41598-023-34466-4