Subjective versus objective refraction in healthy young adults.

PURPOSE: To evaluate objective and subjective refraction differences in healthy young adults. METHODS: Data concerning candidates for the Israeli Air Force Flight Academy, as well as active air force pilots in all stages of service who underwent a routine health checkup between the years 2018 and 2019 were retrospectively analyzed. Objective refraction measured using a single autorefractometer was compared with subjective refraction measured by an experienced military optometrist during the same visit. The results were converted to power vectors (spherical equivalent [SE], J0, and J45). To interpret astigmatism using power vector values, the cylinder power (Cp) was determined. RESULTS: This study included 1,395 young adult participants. The average age was 22.17 years (range, 17-39, 84.8% males). The average SE was - 0.65 ± 1.19 diopter (D) compared with - 0.71 ± 0.91D in the auto- and subjective refraction, respectively (p = 0.001). Cp was 0.91 ± 0.52D and 0.67 ± 0.40D, respectively (p < 0.001). This difference was more common in older participants (p < 0.001). J0 and J45 value differences were not significant. The absolute SE value of subjective refraction was lower in the myopic (p < 0.001) and hyperopic (p < 0.001) patients. CONCLUSIONS: Young hyperopic participants tended to prefer "less plus" in subjective refraction compared with autorefraction. Young myopic participants tended to prefer "less minus" in subjective refraction compared with autorefraction. All participants, but mainly older participants, preferred slightly "less Cp" than that measured using autorefraction; The astigmatic axis did not differ significantly between the methods.

The influence of refractive state and heterophorias on visual acuity and stereoacuity in healthy young adults.

PURPOSE: To evaluate associations of refractive error and heterophoria with best-corrected visual acuity and stereoacuity in a population of healthy young adults. METHODS: Data extracted from the Israeli Defense Forces Air Force candidates database was analyzed retrospectively. Myopia and hyperopia were defined as spherical equivalent of ≤ -0.50 D and ≥ +0.50 D. Cylinder of ≥0.75 D was considered astigmatism. Oblique astigmatism was defined as axis between 30°-60° and 120°-150°. Heterophoria of ≥8Δ for near was considered exo- or esophoria. RESULTS: The study population included 5,491 subjects (75.8% male), with a mean age of 17.6 ± 0.9 years: 2,355 (42.9%) had myopia, 640 (11.6%) had hyperopia, and the rest were emmetropic. Astigmatism was present in 2,006 participants (36.5%), and of those, 619 (30.9%) had oblique astigmatism. Emmetropia was correlated with better best-corrected visual acuity; astigmatism and high hyperopia, with poorer best-corrected visual acuity. A total of 331 subjects (6%) had heterophoria of ≥8Δ; of those, 300 (90.6%) had exophoria and 31 (9.4%) had esophoria. The prevalence of exophoria was higher in the myopic group, and exophoria was not associated with stereoacuity. Esophoria and anisometropia were associated with worse stereoacuity. The best stereopsis was achieved by emmetropic subjects with no astigmatism. CONCLUSIONS: Emmetropia is associated with better best-corrected visual acuity and stereoacuity. Astigmatism and high hyperopia are correlated with poorer best-corrected visual acuity. Exophoria does not interfere with stereopsis, but both esophoria and anisometropia do.