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Yue (Maria) Liu, Christine F. Wildsoet; Title: The Effects Of Multifocal Lenses On Experimental Emmetropization In Young Chicks After Ciliary Nerve Section (cnx) And Iridectomy (id). Invest. Ophthalmol. Vis. Sci. 2011;52(14):6295.
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We previous reported results from studies using 2-zone spectacle lenses fitted to chicks to study this regulation. As a follow-up to these studies, we combined this lens design with two types of surgery, i.e., CNX, which produces a fixed dilated pupil and eliminates accommodation, and ID, which provides a fixed enlarged optical aperture with minimal effect on accommodation.
Unilateral CNX or ID was performed on young chicks 5 days prior to fitting the same eyes with 2-zone spectacle lenses, which were worn for 5 days from 17 days of age. The study used four 2-zone concentric lens designs as follows: (i) +5D center (+5C), (ii) +5 D periphery (+5P), (iii) -5 D center (-5C), (iv) -5 D peripheral (-5P), with plano in periphery for all C-designs and in the center for all P-designs. Central zone diameters (CZD) of 3.5 and 6.5 mm were tested.
Neither CNX nor ID alone significantly affected refractive error and vitreous chamber depth although the surgeries lead to increased variability compared to that observed in nonS eyes. Both SV lenses (-5 & +5 D), and 2-zone-3.5 mm CZD lenses induced similar on-axis refractive changes in CNX and ID eyes to those in nonS eyes. In contrast, both surgeries significantly affected refractive error outcomes for all four 2-zone-6.5 mm CZD lenses. Despite their strong influence on on-axis refractive error changes in lenses with 6.5 CZD, the surgeries did not significantly alter changes in relative peripheral refractive errors (RPR). Nontheless, both the change in on-axis refractive error and lens design significant influenced RPR.
CNX and ID surgeries both increase the optical aperture of the eye, and CNX also eliminates accommodation yet induced similar responses to 2-zone spectacle lenses, which differ from the responses of normal eyes only when the CZD is large. Changes in the pattern of optical defocus experienced at on- and/or off-axis retinal regions in the presence of multifocal lenses with large central optical zones are a plausible explanation for these results.
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