Population prevalence of tilted optic disks and the relationship of this sign to refractive error

Abstract

To assess the prevalence of tilted disks and its association with refractive error and visual field defects. Population-based cohort study. The Blue Mountains Eye Study examined urban Australians aged 49 years or older between 1992-1994. Of 4,433 eligible participants, 3,654 (82.4%) participated. The eye examination included logMAR visual acuity, standardized refraction, cover testing, stereoscopic optic disk photography, and Humphrey automated perimetry. Inferior or nasal optic disk tilting was graded from stereoscopic photographs. Of 3,583 participants with gradable photographs, inferior or nasal optic disk tilting was observed in 77 eyes of 56 participants (1.6%). The prevalence of tilted disks increased from 0.4% in eyes with astigmatism < 1.0 diopters to 17.9% in eyes with astigmatism >or= 5.0 diopters. The mean astigmatic error was 2.2 diopters in eyes with tilted disks compared with 0.7 diopters in eyes with normal disk appearance, P <.001. Myopia was present in 66.2% of eyes with tilted disks compared with 12.4% of eyes with a normal disk appearance, P <.001. The most common associated features were astigmatism (93.5%), pallor, and tessellation of the adjacent chorioretinal tissues (74.0%), situs inversus of the retinal vessels (70.1%), beta-peripapillary atrophy (64.9%), strabismus (30.4%), visual field defects (19.4%), posterior staphyloma (18.2%), inferonasal pigmentary accumulation (9.1%), and chorioretinal atrophy (5.2%). Superotemporal (33.3%) and superior (25.0%) visual field defects were most frequent. A tilted disk appearance was not a rare finding in our study population and was strongly associated with astigmatism and higher levels of spherical refractive error, particularly myopia. The tilted disk and its associated visual field defect should be distinguished from other sinister causes.