Purchase this article with an account.
C. Kee, L. Hung, Y. Qiao, R. Ramamirtham, E.L. Smith III; Astigmatism Associated with Experimentally Induced Ametropia in Infant Monkeys (Macaca mulatta) . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1990.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Purpose: Astigmatism is the most common ametropia found in the human population. However, other than obvious mechanical factors, little is known about the etiology of astigmatism. To gain insight into the genesis of astigmatism, we examined the prevalence and nature of the astigmatism that is associated with experimentally induced ametropias in infant monkeys. Methods: We analyzed biometric data obtained from infant monkeys that underwent a variety of lens-rearing regimens that altered normal emmetropization. These visual manipulations included form deprivation imposed by diffusers (n = 24) and optical defocus imposed by either spherical (n = 39) or sphero-cylindrical lenses (n = 39). Refractive development of all monkeys was closely followed by performing cycloplegic retinoscopy, keratometry and A-scan ultrasonography periodically throughout the treatment and recovery periods. Results from 16 normal monkeys and 3 infants that were reared with bilateral plano-lenses were used for comparison purposes. Results: Significant amounts of astigmatism were associated with experimentally induced ametropia especially when the eyes exhibited relative hyperopic refractive errors and slow axial growth rates. The astigmatism was essentially corneal in origin and the axes, which were relatively constant throughout the treatment and recovery periods, were typically oblique and mirror symmetric in the two eyes. The magnitude of astigmatism was usually matched between the two eyes, even in some monkeys that were treated monocularly. Interestingly, the astigmatism was not permanent; the majority of the monkeys exhibited substantial reductions in astigmatism following the cessation of the lens-rearing procedures. Conclusions: In infant monkeys visual conditions that alter the normal emmetropization process frequently promote the development of astigmatism. Similarities between the astigmatic errors in our monkeys and some astigmatic errors in humans suggest that vision-dependent changes in eye growth may produce astigmatism in humans.
This PDF is available to Subscribers Only