Purchase this article with an account.
C. F. Wildsoet, S. A. McFadden; Optic Nerve Section Does Not Prevent Form Deprivation-Induced Myopia or Recovery From it in the Mammalian Eye. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1737.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
In chickens, disconnecting the eye from the brain by optic nerve section (ONS) does not prevent form deprivation (FD)-induced myopia. Moreover, the response is slightly exaggerated, although the endpoint of recovery has a hyperopic offset compared to normal. In the study reported here, we looked for a parallel between guinea pigs and chicks with respect to the effect of ONS on FD myopia. In an earlier ONS study involving lens-wearing guinea pigs, we reported that exaggerated responses to negative lenses.
Fifteen guinea pigs underwent ONS or Sham surgery on the right eye at 4-5 days of age. These eyes were subsequently form deprived with diffusers for 2 weeks from 3 days after the surgery. Nine additional animals underwent only ONS. Refractive error and axial ocular parameters were measured before, during and after FD (at 8, 15 and 22 days of age), and 18 and 33 days after diffuser removal, using retinoscopy and high frequency A-scan ultrasonography.
While Sham eyes responded like normal eyes to FD, becoming moderately myopic over the first 2 weeks (1 week: -4.9D; 2 weeks -5.5D), ONS eyes showed higher myopia (1 week: -7.5D: 2 weeks: -8.5D). Nonetheless, all eyes recovered from their myopia when the diffusers were removed, losing 6.0D (Sham) and 4.9D (ONS) after 18 days. By 33 days, ONS eyes showed a small residual myopic offset (-1.6D), which was not present in Sham eyes. Eyes subjected to ONS alone also showed small myopic shifts in refraction (-1.3 to -2.9D).
Guinea pigs show exaggerated myopic responses to FD in the absence of an intact ON, suggesting that myopic eye growth is driven by local retinal circuits. Changes in the retinal circuitry after ONS, either due to loss of centrifugal fibers or secondary to RGC degeneration, offer a plausible explanation for the increased gain in FDM, which is also seen in chickens. Recovery from FD myopia is also independent of an intact ON, although different from chickens, guinea pigs do not exhibit a hyperopic offset in their endpoint refractions, unlike chicks, perhaps related to differences in the choroidal response.
This PDF is available to Subscribers Only