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Zheng Shao, Kaitlin Bunghardt, Marsha L Kisilak, Melanie C W Campbell; Eye Dimensions during Lens Induced Myopia (LIM) and Recovery in the Chick. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3606.
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The chick eye refocuses out of focus images, primarily through changes in ocular growth rates. We reported changes in eye power during recovery from lens induced myopia (LIM) in the chick eye. Here we analyze changes in eye dimensions in LIM and recovery.
Nine Ross Ross chicks were unilaterally goggled (-15D) on the day of hatching. The goggle was removed on day 7. Retinoscopy and ultrasound were performed; measurements continued up to day 10 at 10 time points. Mean ocular refraction (MOR), axial length, the distance from the cornea to the back of the lens (CBL), lens thickness, and vitreous chamber depth (VCD) were measured; power changes were calculated. All data were fitted with linear functions of age, and paired t tests were performed.
During LIM, MOR of the goggled eye partially emmetropized (-11.3 D) to the goggle by day 7, primarily due to faster increases in VCD. The lengths and MORs predicted a -3.2 D power difference between treated and control eyes on day 7. The lens and CBL were significantly thicker in treated versus control eyes. After goggle removal, axial length, CBL, and lens thickness for the treated eye didn’t change significantly between days 7 and 8, while VCD decreased. Dimensions continued to increase in the control eye. Lens thickness was still significantly larger in the treated eye on day 8. Recovery from LIM was complete by day 9 and resulting dimensions did not differ significantly from the control eye for both days 9 and 10. Power decreased significantly between days 7 and 8 in the treated eye and relative to the control eye. After day 8, power of the treated eye didn’t change significantly while power of the control eye decreased, and they were not significantly different by day 9.
By day 7 in LIM, the differences in axial length and MOR between eyes predict a slightly lower power in the goggled eye. The thicker lens and CBL are consistent with a small power decrease. During recovery, lens thickness and eye power, as well as length, are significantly different between treated and control eyes. Days 7 to 9, these properties do not change significantly in the treated eye but continue to change in the control eye. Differences between the treated and control eyes, in power and in dimensions, in addition to length, are present during LIM and recovery. After emmetropization is complete in recovery, none of the properties considered differ between the two eyes.
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