Peripheral refraction of myopic eyes with spectacle lenses correction and lens free emmetropes during accommodation

Purpose To measure axial and off-axis refraction patterns in myopic eyes with spectacle lenses correction and lens free emmetropes in young healthy subjects at different target distances from 2.00 m (0.50 D) to 0.20 m (5.00 D) in terms of sphere, astigmatism, and spherical equivalent refraction. Methods Refraction was measured at the center, 20 and 40 degrees from the line of sight both nasally and temporally in 15 emmetropic and 25 myopic young healthy subjects with an open field, binocular, infrared autorefractor (Grand Seiko WAM-5500, Hiroshima, Japan). Fixation target was a Maltese cross set at 2.00, 0.50, 0.33 and 0.20 m from the corneal plane. Changes in off-axis refraction with accommodation level were normalized with respect to distance axial values and compared between myopic eyes with spectacle lenses correction and lens free emmetropes. Results Off-axis refraction in myopic eyes with spectacle lenses correction was significantly more myopic in the temporal retina compared to lens free emmetropes except for the closest target distance. Relative off-axis refractive error changed significantly with accommodation when compared to axial refraction particularly in the myopic group. This change in the negative direction was due to changes in the spherical component of refraction that became more myopic relative to the center at the 0.20 m distance as the J0 component of astigmatism was significantly reduced in both emmetropes and myopes for the closest target. Conclusion Accommodation to very near targets (up to 0.20 m) makes the off-axis refraction of myopes wearing their spectacle correction similar to that of lens free emmetropes. A significant reduction in off-axis astigmatism was also observed for the 0.20 m distance.

Comparing Patient- and Clinician-Administered Near Point of Convergence After Concussion

Objective: (1) To compare patient- and clinician-administered measurements of near point of convergence (NPC) distance including the percentage of patients exceeding clinical cutoffs among concussed adolescents and (2) to assess the reliability of patient- and clinician-measured NPC distances. Methods: A total of 762 patients (mean = 15.51, SD = 3.09 y) within 30 days of concussion participated. The NPC distance was measured consecutively with the patient and clinician controlling the fixation target. The differences between patient (PT) and clinician (CLIN) measurements and cases exceeding cutoffs (ie, ≥5 cm) were examined with a series of t tests and chi-square tests, respectively. Intraclass correlation coefficients and unbiased estimate of reliability were performed. Results: The NPC measurements were similar, t(761) = −.26, P = .79, between the PT (mean = 3.52, SD = 3.77 cm) and CLIN (mean = 3.54, SD = 3.97 cm) conditions. The number of measurements that exceeded cutoffs was similar among the PT (2.5%; 19/762) and CLIN conditions (3%; 23/762) (P = .10), and the number of measurements classified as abnormal/invalid was also similar among the PT (2.5%; 19/762) and CLIN conditions (3%; 23/762) (P = .10). There was excellent reliability between the methods (intraclass correlation coefficients = .85, unbiased estimate of reliability = .92). Conclusion: The findings support the application of this assessment in clinical settings where the clinician may not have direct contact with their patient and rely on the patient (eg, telehealth).

Third-Eye Rivalry

We showcase an optical phenomenon that we call Third-Eye Rivalry. The effect is most easily induced by viewing one’s own reflection in a mirror. Using the pupil of the opposing eye as a fixation target, people can easily cross their eyes in free fusion to experience vivid rivalry. The resulting percept is of a prominent central “third” eye and two peripheral faces rivaling for perceptual dominance. We illustrate the process of achieving third-eye rivalry and discuss historical connotations of the third eye in scientific and mystical contexts.

Third-eye Rivalry

We showcase an optical phenomenon that we call “Third-eye Rivalry”. The effect is most easily induced by viewing one’s own reflection in a mirror. Using the pupil of the opposing eye as a fixation target, people can easily cross their eyes in free-fusion to experience vivid rivalry. The resulting percept is of a prominent central “third” eye and two peripheral faces rivalling for perceptual dominance. We illustrate the process of achieving third-eye rivalry and discuss historical connotations of the third eye in scientific and mystical contexts.