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D. L. Nickla, F. Schroedl; Influences of the Autonomic Nervous System on the Compensatory Responses of the Chick Eye to Defocus: Single- and Double-lesion Studies of the Pterygopalatine Ganglion. Invest. Ophthalmol. Vis. Sci. 2008;49(13):3590.
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It is unknown to what extent the autonomic nervous system plays a role in eye growth regulation. We lesioned the pterygopalatine ganglion (PPG) alone, and in combination with the superior cervical ganglion (SCG), or the ciliary ganglion (CG), to study influences on the compensatory responses to defocus in chicks.
The PPG was deafferented in 19-28d-old birds by lesioning the pre-ganglionic facial nerve (N. VII), as described in Schroedl et al. (IOVS; 2006). Double lesions were also done. Eyes were measured 1-3 days prior to surgery, and at various intervals before and after onset of the visual manipulation, using A-scan ultrasonography. Refractive errors were measured using a Hartingers refractometer. Appropriate non-lesioned controls were done. PPGX: No manipulation (n=7). Form deprivation (n=4). Lesioned eyes were deprived of form vision using a translucent diffuser for 7d. Myopic defocus: Recovery from deprivation (n=4). Positive (+10 D) lens wear (n=5). Hyperopic defocus: Removal of lenses (n=4). Negative lens (-10 D) wear (n=7). PPGX/SCGX: Myopic defocus (+10D lenses; n=5). Hyperopic defocus was induced by removing the lenses. PPGX/CGX: Myopic defocus (+10D lenses, n=13).
PPGX: There were no significant effects on ocular dimensions; eyes responded normally to all visual manipulations. PPGX/SCGX: There was a significant inhibition in the choroidal response to myopic defocus (change over 3d: 274 vs 376 um; p<0.05), and a tendency towards reduced refractive compensation (4.6 D vs 6.7 D; p=0.06). There was no effect on the response to hyperopic defocus. PPGX/CGX: There was a significant lesion-induced increase in choroidal thickness over 5d (X vs C: 83 vs 1 um; p<0.001). Furthermore, the refractive compensation to myopic defocus was reduced (1.6 D vs 6.7 D; p<0.01), as was the choroidal response (72 hrs: 66 vs 319 um; p<0.001) (despite the surgery-induced thickening, the response was still incomplete: 149 vs 319 um; p<0.01). The difference in the axial growth response was not significant, however, there was a significant inhibition in the growth of the anterior chamber (X vs fellow: 62 vs 111 um/72 hrs; p<0.001).
While lesioning the PPG alone had little effect, transection of both parasympathetic inputs, and the PPG/SCG altered the refractive and choroidal compensation to myopic defocus, with the ciliary input being more prominent. A role for the PPG in these responses however, cannot be excluded, because of the potential for as yet unknown interganglionic circuitries.
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