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D. Troilo, K. Totonelly, C.-S. Kee, D. Nickla; Aniso Contact Lens Rearing Induces Anisometropia in Marmosets. Invest. Ophthalmol. Vis. Sci. 2007;48(13):1032.
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Monocular treatment with extended wear soft contact lenses produces compensatory changes in eye growth and refractive state in infant marmosets (Whatham and Judge, 2001). In this study we extended this paradigm by rearing marmosets with binocular contact lenses of opposite sign.
Juvenile marmosets (n=27) were raised with extended wear soft contact lenses removed daily overnight for an average duration of 10 wks (range 6-17) beginning at an average age of 76 d (range 41-101). Experimental animals (n=16) wore either a positive or negative contact lens over one eye (±3 stepped up to ±5 D) and a plano contact lens or no lens over the other. Some experimental animals (n=11) wore binocular lenses of equal magnitude but opposite sign (±3 or ±5 D). Untreated marmosets (n=14) served as controls and two wore plano lenses monocularly. Cycloplegic refractive state, corneal curvature, and vitreous chamber depth were measured before, during, and after the period of lens wear. In addition, to investigate the accommodative response to the lenses, the effective refractive state was examined periodically in several animals with and without cycloplegia while wearing the lenses.
Compared to the contralateral untreated eyes, monocular negative power contact lenses produced significantly greater vitreous chamber depth (exp-con, mean ±se, 0.170 ±0.028 mm, p<0.001) and relative myopia (-2.41 ±0.64 D, p<0.01). Monocular positive power lenses produced, on average, a less robust but significant reduction in vitreous chamber depth (-0.082 ±0.029 mm, p<0.05) and relative hyperopia (1.40 ±0.43 D, p<0.05). In marmosets reared binocularly with lenses of opposite sign, we found significant interocular differences in vitreous chamber depths (negative lens - positive lens, 0.275 ±0.047 mm, p<0.001) and refractive state (-5.72 ±0.56 D, p<0.001). All data taken together show that refractive state is significantly correlated with the sign and power of the contact lens (r=0.538, p<0.001). Measures of refractive state through aniso lenses show evidence of effective hyperopia in the negative lens treated eyes and effective myopia in the positive lens treated eyes. Further, compared to the positive lens treated eye, the negative lens treated eyes do not appear to clear the imposed hyperopia by accommodation.
Aniso contact lens rearing paradigms in marmosets effectively alter eye growth and refractive state in a predictable manner. Compensation for negative lens-imposed hyperopia is more complete than compensation for positive lens-imposed myopia and may be related to the pattern of accommodation adopted under conditions of imposed anisometropia.
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