Optometry and Vision Sciences - Research Publications

Permanent URI for this collection

Search Results

Now showing 1 - 3 of 3
  • Item
    No Preview Available
    The Effect of Daily Transient+4 D Positive Lens Wear on the Inhibition of Myopia in the Tree Shrew
    McBrien, NA ; Arumugam, B ; Metlapally, S (ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2012-03)
    PURPOSE: Negative-lens-induced defocus causes accelerated ocular elongation and myopia, whereas positive-lens-induced defocus produces reduced ocular elongation and hyperopia. Short durations of positive lens wear result in markedly stronger temporal effects than do short periods of negative lens wear in the chick model of refractive development. In mammalian and nonhuman primate models, there have been equivocal results in inhibiting myopia by short periods of positive lens wear when compared with data from the chick model. The purpose of the present study was an evaluation of full-time -9.5 D negative lens wear interrupted by short periods of daily +4 D positive lens wear in preventing experimental myopia in the tree shrew. METHODS: One treatment group wore negative lenses (-9.5 D) binocularly for 23 hours a day (10 hours of which were spent in total darkness), interrupted by 1 hour of wearing positive lenses (+4 D) binocularly for 12 days. Another group of animals wore negative lenses (-9.5 D) binocularly for 23 hours a day, interrupted by two 30-minute periods of positive lens (+4 D) wear daily, again for 12 days. The animals were raised on a 14-hour/10-hour light-dark cycle. Animals wearing -9.5 D lenses binocularly, interrupted by 0-powered lenses for either 1 hour or two 30-minute periods daily for 12 days, acted as controls. RESULTS: Continuous wear of -9.5 D lenses binocularly induced a -10.8 D myopic shift in refraction. Full-time wear of -9.5 D lenses binocularly, interrupted by 1 hour of 0-power lens wear binocularly, caused a myopic shift of 3.6 D over 12 days, whereas wearing -9.5 D lenses, interrupted by 1 hour every day of +4.0 D lens wear binocularly, whether it was continuous or divided into two 30-minute periods, caused a myopic shift of only 0.7 D over 12 days. CONCLUSIONS: Daily intermittent +4 D positive lens wear effectively inhibits experimentally induced myopia and may prove a viable approach for preventing myopia progression in children.
  • Item
    No Preview Available
    Eyes in Various Species Can Shorten to Compensate for Myopic Defocus
    Zhu, X ; McBrien, NA ; Smith, EL ; Troilo, D ; Wallman, J (ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2013-04)
    PURPOSE: We demonstrated that eyes of young animals of various species (chick, tree shrew, marmoset, and rhesus macaque) can shorten in the axial dimension in response to myopic defocus. METHODS: Chicks wore positive or negative lenses over one eye for 3 days. Tree shrews were measured during recovery from induced myopia after 5 days of monocular deprivation for 1 to 9 days. Marmosets were measured during recovery from induced myopia after monocular deprivation, or wearing negative lenses over one or both eyes, or from wearing positive lenses over one or both eyes. Rhesus macaques were measured after recovery from induced myopia after monocular deprivation, or wearing negative lenses over one or both eyes. Axial length was measured with ultrasound biometry in all species. RESULTS: Tree shrew eyes showed a strong trend to shorten axially to compensate for myopic defocus. Of 34 eyes that recovered from deprivation-induced myopia for various durations, 30 eyes (88%) shortened, whereas only 7 fellow eyes shortened. In chicks, eyes wearing positive lenses reduced their rate of ocular elongation by two-thirds, including 38.5% of eyes in which the axial length became shorter than before. Evidence of axial shortening in rhesus macaque (40%) and marmoset (6%) eyes also occurred when exposed to myopic defocus, although much less frequently than that in eyes of tree shrews. The axial shortening was caused mostly by the reduction in vitreous chamber depth. CONCLUSIONS: Eyes of chick, tree shrew, marmoset, and rhesus macaque can shorten axially when presented with myopic defocus, whether the myopic defocus is created by wearing positive lenses, or is the result of axial elongation of the eye produced by prior negative lens wear or deprivation. This eye shortening facilitates compensation for the imposed myopia. Implications for human myopia control are significant.
  • Item
    No Preview Available
    Muscarinic Antagonist Control of Myopia: Evidence for M4 and M1 Receptor-Based Pathways in the Inhibition of Experimentally-Induced Axial Myopia in the Tree Shrew
    Arumugam, B ; McBrien, NA (ASSOC RESEARCH VISION OPHTHALMOLOGY INC, 2012-08)
    PURPOSE: The broadband muscarinic antagonist atropine is effective in stopping the progression of myopia in animals and humans. The partially selective M(1)/M(4) antagonist pirenzepine also slows progression of myopia, although not as effectively as atropine. Due to the supra maximal doses utilized in these studies, it is unclear if this antimyopia effect occurs through a receptoral-based mechanism, and if so, which receptors are involved. Studies in chicks indicate the involvement of the M(4) muscarinic receptor. The current study investigated the effect of the highly selective muscarinic antagonists Muscarinic Toxin 3 (MT3) (M(4) selective) and Muscarinic Toxin 7 (MT7) (M(1) selective) on experimental myopia in a mammalian model. METHODS: Tree shrews (n = 23) underwent daily intravitreal injections of MT3, MT7, or vehicle (phosphate buffered saline) for five days in the treated eye, combined with deprivation of vision with a translucent occluder (MD). The contralateral eye was unocccluded and underwent intravitreal injections of vehicle for the same period. Two additional groups (n = 10) underwent daily intravitreal injections of MT7 or vehicle for 10 days in the treated eye combined with negative lens (-9.5 diopter [D]) defocus (LIM). The control eye was injected with saline and wore a plano lens. RESULTS: Both MT3 and MT7 treatment reduced the development of deprivation-induced myopia (treated-control eye [T-C]; vehicle-MD; -4.3 ± 0.6 D versus MT3-MD; -0.7 ± 0.2 D and MT7-MD; -0.7 ± 0.4 D; P < 0.001). MT7 treatment was effective at inhibiting lens-induced myopia (T-C; vehicle-LIM; -4.6 ± 0.5 D versus MT7-LIM; 0.2 ± 0.2 D; P < 0.05). CONCLUSIONS: The findings demonstrate that inhibition of form-deprivation myopia by muscarinic antagonists involves both M(4) and M(1) muscarinic receptor signaling pathways in mammals.