Influence of Pterygium on Refractive Status in Older Adults: The Brazilian Amazon Region Eye Survey (BARES)

Abstract

Purpose : Pterygium is a proliferative overgrowth of bulbar conjunctiva that can induce refractive changes and cause visual impairment. The purpose of this study is to determine the influence of pterygium on the refractive status in older adults.

Methods : BARES is a population-based cross sectional study conducted using cluster random sampling, to enumerate subjects ≥45 years of age from Parintins city. Eligible subjects were enumerated through a door-to-door household survey and invited for an eye exam including measurement of uncorrected (UCVA), presenting (PVA) and best-corrected (BCVA) visual acuity. Pterygium was assessed in each eye considering its location (nasal, temporal or both), size (> 3mm) and pupillary invasion. The influence of pterygium on spherical and cylinder components from subjective and auto refraction and lines of improvement of visual acuity from UCVA and PVA to BCVA were analyzed. Eyes with previous ocular surgery, other anterior segment abnormalities and fundus changes were excluded.

Results : From a total of 2384 eligible subjects, 2041 (85.6%) were examined, with 2933 eyes included in the study. When compared to eyes without pterygium (N=1511), eyes with any pterygium (N=1422) had significantly higher subjective means of spherical component (1.00D vs 0.85 D, p=0.0026) and cylinder component (-0.79D vs -0.48D, p=0.0001) as well as auto-refraction means of spherical (1.68D vs 1.07D, p=0.0001) and cylinder (-1.49D vs -0.74D, p=0.0001) disregarded the lesion’s location and size. Significantly larger subjective spherical equivalent (0.91 vs 0.56SE; p = 0.0001) was found only for pterygium >3mm. In auto-refraction significantly larger spherical equivalent was found for any pterygium (0.92 vs 0.70 SE; p=0.0002) and for pterygium >3mm (1.67 vs 0.68; p=0.0001). The number of lines of improvement from UCVA to BCVA was significantly higher (2.75 vs 2.25, p=0.0001) only for pterygium > 3mm. Improvement from PVA to BCVA was significantly higher for any pterygium (1.71 vs 1.52, p=0.0052) and for pterygium >3mm (1.98 vs 1.56; p=0.0001).

Conclusions : Pterygium was associated with increase of refractive error with direct effect on visual acuity. Advanced cases showed substantial effect of refractive correction probably due to significant pterygium-induced refractive error. As a treatable condition the access to surgical excision should be improved for this specific population.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.