Characterization of Pterygium as Primary Cause of Visual Impairment/Blindness in Older Adults from Urban Areas of Parintins: The Brazilian Amazon Region Eye Survey

Abstract

Purpose: Ultraviolet (UV) radiation is the most commonly reported risk factor associated to the occurrence of pterygium. Parintins is located 02^o37’42”S latitude and 56^o44’09’’W longitude in the center of the Brazilian Amazon region, an equatorial territory with high exposure to UV rays. The purpose of this study is to characterize visually impaired/blind eyes attributable to pterygium in older adults from urban Parintins City, Brazil.

Methods: The Brazilian Amazon Region Eye Survey (BARES) is an ongoing population-based cross-sectional study to determine prevalence and causes of visual impairment/blindness of residents of urban and rural areas, aged 45 years and older. Eligible participants from urban areas were invited for ophthalmic assessment including presenting (PVA), best-corrected visual acuity (BCVA), anterior segment evaluation by slit-lamp, refraction and fundoscopy. Eyes with pterygium as the principal cause of BCVA ≤20/40 were photographed and the size of the lesion was calculated. Thickness of the lesion was measured in the most prominent section with anterior segment spectral-domain optical coherence tomography (ASSD-OCT). Correlations between size and thickness of the lesions with best-corrected visual acuity, gender, refractive errors and schooling were performed.

Results: In a cohort of 579 participants, pterygium was detected in 322 (55.5%), bilaterally occurring in 201. Out of these, 18 subjects (13 females) with 22 eyes (14 unilateral and 4 bilateral) had visual impairment caused by pterygium (5.6%). Nasal lesions only were present in 20 eyes, temporal lesions only in 2 eyes and both nasal and temporal lesions in 10 eyes. Lesion sizes ranged from 0.15 to 0.64 (mean= 0.36±0.13) of corneal diameter. Pterygium thickness ranged from 222 to 736 mm (mean=389±104 mm). Visual impairment (BCVA <20/40) was found in 19 eyes and blindness (BCVA <20/200) was present in 3 eyes. No correlations were found between lesion size/thickness with BCVA, gender, refractive error and schooling.

Conclusions: In this cohort of this at-risk population, pterygium was highly prevalent and caused visual impairment/blindness in 3.1% of participants. Lesion size wasn’t a good predictor of visual impairment as well as thickness. Further studies with larger sample sizes are needed to better understand the visual deficit associated with this disorder.