Spectacle lens compensation in the pigmented guinea pig

School of Psychology, Faculty of Science and Information Technology, The University of Newcastle, Australia.
Vision research (Impact Factor: 1.82). 12/2008; 49(2):219-27. DOI: 10.1016/j.visres.2008.10.008
Source: PubMed

ABSTRACT When a young growing eye wears a negative or positive spectacle lens, the eye compensates for the imposed defocus by accelerating or slowing its elongation rate so that the eye becomes emmetropic with the lens in place. Such spectacle lens compensation has been shown in chicks, tree-shrews, marmosets and rhesus monkeys. We have developed a model of emmetropisation using the guinea pig in order to establish a rapid and easy mammalian model. Guinea pigs were raised with a +4D, +2D, 0D (plano), -2D or -4D lens worn in front of one eye for 10 days or a +4D on one eye and a 0D on the fellow eye for 5 days or no lens on either eye (littermate controls). Refractive error and ocular distances were measured at the end of these periods. The difference in refractive error between the eyes was linearly related to the lens-power worn. A significant compensatory response to a +4D lens occurred after only 5 days and near full compensation occurred after 10 days when the effective imposed refractive error was between 0D and 8D of hyperopia. Eyes wearing plano lenses were slightly more myopic than their fellow eyes (-1.7D) but showed no difference in ocular length. Relative to the plano group, plus and minus lenses induced relative hyperopic or myopic differences between the two eyes, inhibited or accelerated their ocular growth, and expanded or decreased the relative thickness of the choroid, respectively. In individual animals, the difference between the eyes in vitreous chamber depth and choroid thickness reached +/-100 and +/-40microm, respectively, and was significantly correlated with the induced refractive differences. Although eyes responded differentially to plus and minus lenses, the plus lenses generally corrected the hyperopia present in these young animals. The effective refractive error induced by the lenses ranged between -2D of myopic defocus to +10D of hyperopic defocus with the lens in place, and compensation was highly linear between 0D and 8D of effective hyperopic defocus, beyond which the compensation was reduced. We conclude that in the guinea pig, ocular growth and refractive error are visually regulated in a bidirectional manner to plus and minus lenses, but that the eye responds in a graded manner to imposed effective hyperopic defocus.

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    • "In contrast, Schaeffel et al. (Schaeffel et al., 1988) demonstrated through the use of positive and negative lenses of specific refractive powers that chicks could accurately compensate for imposed myopic or hyperopic defocus by modulating the axial length of the eye. Lens compensation was subsequently demonstrated in tree shrews (Norton et al., 2010), monkeys (Smith et al., 2010), guinea pigs (Howlett and McFadden, 2009), and mice (Tkatchenko et al., 2010). Remarkably, studies using animal models have demonstrated that young eyes can recover from induced myopia following removal of the diffuser or negative lens (Siegwart and Norton, 1998; Wallman and Adams, 1987). "
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    ABSTRACT: Myopia is a common ocular condition, characterized by excessive elongation of the ocular globe. The prevalence of myopia continues to increase, particularly among highly educated groups, now exceeding 80% in some groups. In parallel with the increased prevalence of myopia, are increases in associated blinding ocular conditions including glaucoma, retinal detachment and macular degeneration, making myopia a significant global health concern. The elongation of the eye is closely related to the biomechanical properties of the sclera, which in turn are largely dependent on the composition of the scleral extracellular matrix. Therefore an understanding of the cellular and extracellular events involved in the regulation of scleral growth and remodeling during childhood and young adulthood will provide future avenues for the treatment of myopia and its associated ocular complications. Copyright © 2014 Elsevier Ltd. All rights reserved.
    Experimental Eye Research 04/2015; 133. DOI:10.1016/j.exer.2014.07.015 · 2.71 Impact Factor
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    • "Previous studies with chickens have also reported a significant disruption of the natural diurnal rhythms in choroidal thickness in eyes exposed to myopic defocus, with choroidal rhythms found to be significantly phase advanced (Nickla et al., 1998; Nickla, 2006; Papastergiou et al., 1998). Choroidal thickening, associated with periods of myopic defocus has also been widely noted in avians (Nickla et al., 2005; Park et al., 2003; Wallman et al., 1995; Wildsoet and Wallman, 1995; Zhu et al., 2003), mammals (Howlett and McFadden, 2009), and primates (Hung et al., 2000; Troilo et al., 2000). Previous studies of daily rhythms of choroidal thickness in human eyes have only examined subfoveal measures (Brown et al., 2009; Chakraborty et al., 2011). "
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    ABSTRACT: Recent research indicates that brief periods (60 min) of monocular defocus lead to small but significant changes in human axial length. However, the effects of longer periods of defocus on the axial length of human eyes are unknown. We examined the influence of a 12 h period of monocular myopic defocus on the natural daily variations occurring in axial length and choroidal thickness of young adult emmetropes. A series of axial length and choroidal thickness measurements (collected at ∼3 hourly intervals, with the first measurement at ∼9 am and the final measurement at ∼9 pm) were obtained for 13 emmetropic young adults over three consecutive days. The natural daily rhythms (Day 1, baseline day, no defocus), the daily rhythms with monocular myopic defocus (Day 2, defocus day, +1.50 DS spectacle lens over the right eye), and the recovery from any defocus induced changes (Day 3, recovery day, no defocus) were all examined. Significant variations over the course of the day were observed in both axial length and choroidal thickness on each of the three measurement days (p < 0.0001). The magnitude and timing of the daily variations in axial length and choroidal thickness were significantly altered with the monocular myopic defocus on day 2 (p < 0.0001). Following the introduction of monocular myopic defocus, the daily peak in axial length occurred approximately 6 h later, and the peak in choroidal thickness approximately 8.5 h earlier in the day compared to days 1 and 3 (with no defocus). The mean amplitude (peak to trough) of change in axial length (0.030 ± 0.012 on day 1, 0.020 ± 0.010 on day 2 and 0.033 ± 0.012 mm on day 3) and choroidal thickness (0.030 ± 0.007 on day 1, 0.022 ± 0.006 on day 2 and 0.027 ± 0.009 mm on day 3) were also significantly different between the three days (both p < 0.05). The introduction of monocular myopic defocus disrupts the daily variations in axial length and choroidal thickness of human eyes (in terms of both amplitude and timing) that return to normal the following day after removal of the defocus.
    Experimental Eye Research 08/2012; 103:47-54. DOI:10.1016/j.exer.2012.08.002 · 2.71 Impact Factor
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    • "Genetic, as well as environmental, factors have been implicated in the development of myopia, but the relative importance of genes versus environment remains controversial [4]. Myopia can be artificially induced in animal models like chicks [5], tree shrews [6], monkeys [7,8], and guinea pigs [9] by placing negative lenses, which induce hyperopic defocus [10], in front of the animal’s eye. The shift of the focal plane behind the photoreceptor layer triggers substantially increased eye growth. "
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    ABSTRACT: Insulin stimulates eye growth in chicks and this effect is greatly enhanced if the retinal image is degraded by the defocus of either sign. However, it is unclear whether the insulin receptor (IR) is expressed at all in the chicken retina in animals 1-2 weeks post-hatching. We have investigated IR expression and whether IR transcript abundance varies in the fundal layers. To elucidate the possible role of insulin and insulin-like growth factor (IGF)-1 signaling in eye growth regulation, mRNA (mRNA) levels were measured for insulin, IGF-1, IR, and IGF-1 receptor (IGF-1R) during imposed negative or positive defocus. Chicks were treated binocularly with positive or negative spectacle lenses for 4 or 24 h, or they remained untreated (n=6, for each treatment group). Northern blot analyses were performed to screen for transcription variants in the different fundal layers of untreated animals. Real-time PCR was used to quantify IR, IGF-1R, IGF-1, and insulin mRNA levels in the different fundal layers of the chick eye in the three treatment groups. IR mRNA was found in all the studied tissues, although there is evidence of tissue-specific transcript variations. Three major transcripts were detected for IR. The brain, retina, and choroid showed the longest transcript (4.3 kb), which was not present in the liver. Nevertheless, the liver and brain showed a second transcript (2.6 kb) not present in the retina and choroid. A short transcript (1.3 kb) was the predominant form in the liver and choroid, and it seems to be present in the retinal pigment epithelium (RPE) and sclera as well. In the retina, no significant gene expression changes were found when defocus was imposed. Interestingly, in the RPE, both IR and IGF-1R were already downregulated after short periods (4 h) of positive lens wear. In contrast, IR and IGF-1R were upregulated in the choroid and fibrous sclera during treatment with negative, but not positive, lenses. Differences observed in the IR transcript length in different tissues suggest possibly different functions. The differential regulation of IR and IGF-1R in the RPE, choroid, and fibrous sclera is consistent with their involvement in a signaling cascade for emmetropization.
    Molecular vision 05/2011; 17:1436-48. · 1.99 Impact Factor
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