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The potential off-axis performance and accuracy of the PowerRef 3 for measurements in nystagmus

Amiebenomo, Onyekachukwu M., McIlreavy, Lee ORCID:, Erichsen, Jonathan T. ORCID: and Woodhouse, J. Margaret 2020. The potential off-axis performance and accuracy of the PowerRef 3 for measurements in nystagmus. Presented at: AVA Christmas Meeting, Cardiff, Wales, UK, 16 Dec 2019. Perception. (49(6)) Sage, pp. 707-708.

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Accommodation is vital to produce a clear, focussed image for close work. In nystagmus, a continuous conjugate oscillation of the eyes, studies on accommodation are lacking. Ong et al. (1993) demonstrated normal static accommodation, apart from increased depth of focus, in nystagmats. However, in determining the dynamics of accommodation in people with nystagmus, it is unknown how accurate refractive findings will be off-axis. We therefore sought to discover the effect of off-axis positions on measured refractive error during convergence. In six presbyopes without nystagmus (age: 43–70), we used the PowerRef 3 (PlusoptiX R09), which provides continual recording of refractive error, to quantify the effect of imposing different values of defocus (+4, +3, +2, +1, −2 and −4 D) off-axis and centrally. At 1 m, measurements were obtained when participants fixated the PowerRef 3 and at four gaze positions spaced c.2° apart, on either side of the instrument. For positions to the left, readings were obtained for the right eye and vice versa. The lens-induced refractive changes did not differ from the expected change both at the centre and off-gaze positions (except for a −2 D lens at 4°; p = .037). However, these values were all significantly correlated. For gaze position up to 8°, refraction measured was not significantly different from that at the central position (F value range: 0.048–0.778; p value range: 0.624–1.000). Therefore, off- axis refraction measured using the PowerRef 3 remains reliable up to 8°, implying that we will be able to record the stability of refraction during nystagmus eye movement.

Item Type: Conference or Workshop Item (Poster)
Date Type: Publication
Status: Published
Schools: Optometry and Vision Sciences
Publisher: Sage
ISSN: 0301-0066
Last Modified: 14 Jun 2023 09:08

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