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Melanie C W Campbell, Kaitlin Bunghardt, Marsha L Kisilak, Elizabeth L Irving; Both Lens Induced Hyperopia and Recovery Increase the Amplitude of Diurnal Rhythm in Refractive Error. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3604.
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We have reported a larger amplitude of circadian variation in mean ocular refraction (MOR) in the previously goggled eye compared with the control eye on removal of positive or negative lenses. Here we compare the circadian rhythm present during lens induction of hyperopia in the goggled and control eyes with that following goggle removal.
Short term changes in MOR were measured immediately before and after goggle removal following 6 days of emmetropization to lens induced hyperopia. Eleven birds, unilaterally treated with a +10D goggle on the day of hatching, were raised on a 14h/10h light dark cycle. On day 6, beginning at 8:30 am, Hartmann-Shack refractive error and A scan ultrasound axial length (to the retina) were measured every 4 hours, ending on day 9. The goggle was permanently removed after the 8:30am measurement on day 7. MOR was analyzed for the largest common pupil. Linear variations were subtracted and residual sinusoidal variations were fitted before and after goggle removal. Comparisons were made to previously presented results. Paired t tests were used, p≤0.05 for significance and if normalcy or equal variance tests failed, a Wilcoxon Signed Rank Test was performed.
On day 6 after partial emmetropization (+5.5D), sinusoidal amplitudes in goggled eyes vs control eyes were significantly larger for MOR and smaller for length. This implies a difference in the amplitude of power variation between goggled and control eyes. Control eyes were not different from eyes of control birds on day 6. Day 7 diurnal amplitudes for length and MOR after goggle removal were significantly larger than before removal. The eyes’ amplitudes no longer differed for length but MOR amplitude was larger in previously goggled eyes than in control eyes. Acrophases on days 6 and 7 for MOR of goggled eyes were significantly clustered, while those for control eyes were not (Rayleigh test).
Unlike in previously reported emmetropization to -15D lenses, after 6 days, following incomplete emmetropization to +10D lenses, the amplitude of circadian rhythms differed in the control and goggled eyes. Nonetheless, following goggle removal, as for the -15D lenses, the amplitude of oscillation of mean ocular refraction in the treated eye increased. Circadian rhythms could provide enhanced signals to the direction of defocus both during goggling and following goggle removal.
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