Article

The Effect of Simultaneous Negative and Positive Defocus on Eye Growth and Development of Refractive State in Marmosets

SUNY College of Optometry, New York, New York.
Investigative ophthalmology & visual science (Impact Factor: 3.66). 08/2012; 53(10):6479-87. DOI: 10.1167/iovs.12-9822
Source: PubMed

ABSTRACT Purpose. We evaluated the effect of imposing negative and positive defocus simultaneously on the eye growth and refractive state of the common marmoset, a New World primate that compensates for either negative and positive defocus when they are imposed individually. Methods. Ten marmosets were reared with multizone contact lenses of alternating powers (-5 diopters [D]/+5 D), 50:50 ratio for average pupil of 2.80 mm over the right eye (experimental) and plano over the fellow eye (control) from 10 to 12 weeks. The effects on refraction (mean spherical equivalent [MSE]) and vitreous chamber depth (VC) were measured and compared to untreated, and -5 D and +5 D single vision contact lens-reared marmosets. Results. Over the course of the treatment, pupil diameters ranged from 2.26 to 2.76 mm, leading to 1.5 times greater exposure to negative than positive power zones. Despite this, at different intervals during treatment, treated eyes were on average relatively more hyperopic and smaller than controls (experimental-control [exp-con] mean MSE ± SE +1.44 ± 0.45 D, mean VC ± SE -0.05 ± 0.02 mm) and the effects were similar to those in marmosets raised on +5 D single vision contact lenses (exp-con mean MSE ± SE +1.62 ± 0.44 D. mean VC ± SE -0.06 ± 0.03 mm). Six weeks into treatment, the interocular growth rates in multizone animals were already lower than in -5 D-treated animals (multizone -1.0 ± 0.1 μm/day, -5 D +2.1 ± 0.9 μm/day) and did not change significantly throughout treatment. Conclusions. Imposing hyperopic and myopic defocus simultaneously using concentric contact lenses resulted in relatively smaller and less myopic eyes, despite treated eyes being exposed to a greater percentage of negative defocus. Exposing the retina to combined dioptric powers with multifocal lenses that include positive defocus might be an effective treatment to control myopia development or progression.

Download full-text

Full-text

Available from: David Troilo, Jun 20, 2014
1 Follower
 · 
147 Views
  • Source
    • "To relieve this spasm, the fogging method [9] and the dilating drops like atropine have been widely used and it was reported to have substantial effects with non-accomodative mechanism as observed in chick-eye experiment reported by McBrien et al. [18,19]. Others included electrostimulation [19] and multifocal contact lens [20-25]. In addition, 3D image stimulator which was approved as a medical device has been used in our clinics for purposes such as relaxing the over-tensed muscle [26,27]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: To evaluate the efficacy of two non-surgical interventions of vision improvement in children. A prospective, randomized, pilot study to compare fogging method and the use of head mounted 3D display. Subjects were children, between 5 to 15 years old, with normal best corrected visual acuity (BCVA) and up to -3D myopia. Subjects played a video game as near point work, and received one of the two methods of treatments. Measurements of uncorrected far visual acuity (UCVA), refraction with autorefractometer, and subjective accommodative amplitude were taken 3 times, at the baseline, after the near work, and after the treatment. Both methods applied after near work, improved UCVA. Head mounted 3D display group showed significant improvement in UCVA and resulted in better UCVA than baseline. Fogging group showed improvement in subjective accommodative amplitude. While 3D display group did not show change in the refraction, fogging group's myopic refraction showed significant increase indicating the eyes showed myopic change of eyes after near work and treatment. Despite our lack of clear knowledge in the mechanisms, both methods improved UCVA after the treatments. The improvement in UCVA was not correlated to measured refraction values. UCVA after near work can be improved by repeating near and distant accommodation by fogging and 3D image viewing, although at the different degrees. Further investigation on mechanisms of improvements and their clinical significance are warranted.
    The Open Ophthalmology Journal 10/2013; 7:69-48. DOI:10.2174/1874364101307010069
  • [Show abstract] [Hide abstract]
    ABSTRACT: Postnatal eye growth is controlled by visual signals. When wearing a positive lens that causes images to be focused in front of the retina (myopic defocus), the eye reduces its rate of ocular elongation and increases choroidal thickness to move the retina forward to meet the focal plane of the eye. When wearing a negative lens that causes images to be focused behind the retina (hyperopic defocus), the opposite happens. This review summarizes how the retina integrates the constantly changing visual signals in a non-linear fashion to guide eye growth in chicks: (1a) When myopic or hyperopic defocus is interrupted by a daily episode of normal vision, normal vision is more effective in reducing myopia caused by hyperopic defocus than in reducing hyperopia caused by myopic defocus; (1b) when the eye experiences alternating myopic and hyperopic defocus, the eye is more sensitive to myopic defocus than to hyperopic defocus and tends to develop hyperopia, even if the duration of hyperopic defocus is much longer than the duration of myopic defocus; (2) when the eye experiences brief, repeated episodes of defocus by wearing either positive or negative lenses, lens compensation depends on the frequency and duration of individual episodes of lens wear, not just the total daily duration of lens wear; and (3) further analysis of the time constants for the hypothesized internal emmetropization signals show that, while it takes approximately the same amount of time for the signals to rise and saturate during lens-wearing episodes, the decline of the signals between episodes depends strongly on the sign of defocus and the ocular component. Although most extensively studied in chicks, the nonlinear temporal integration of visual signals has been found in other animal models. These findings may help explain the complex etiology of myopia in school-aged children and suggest ways to slow down myopia progression.
    Experimental Eye Research 03/2013; 114. DOI:10.1016/j.exer.2013.02.014 · 3.02 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Purpose. To determine the effect of wearing a lens with a unique peripheral optical design, on the development and progression of defocus-induced myopia in newly hatched chickens. Methods. Eighty-five newly hatched chickens underwent bilateral retinoscopy and A-scan ultrasound to determine their refractive error and axial length. They were randomly divided into Control and two Test groups, in which each chicken was fitted with a goggle-lens over the right eye, with the left eye remaining untreated. The Control group wore a lens of power -10.00D of standard spherical optical design. The two Test lenses both had a central optical power -10.00D, but used different peripheral myopia progression control (MPC) designs. For all groups, retinoscopy was repeated on days 3, 7, 10 and 14; ultrasound was repeated on day 14. Results. On day 0 there was no statistical difference in refractive error (mean +6.92D) or axial length (mean 8.06mm) between Test and Control groups or treated and untreated eyes (all p>0.05). At day 14, 37/85 chickens (43.5%) had not experienced goggle detachment and were included in the final analyses. In this cohort there was a significant refractive difference between the treated eyes of the Control group (n=17) and those of Test1 (n=14) and Test2 (n=6) groups (both p<0.01); Control -4.65D±2.11, Test1 +4.57D±3.11, Test2 +1.08D±1.24 (mean ± standard error of the mean). There was also a significant axial length difference (both p<0.01); Control 10.55mm±0.36, Test1 9.99mm±0.14, Test2 10.17mm±0.18. Conclusions. Use of these unique MPC lens designs over 14-days caused a significant reduction in the development of defocus-induced myopia in chickens; the degree of reduction appeared to be design specific.
    Investigative ophthalmology & visual science 03/2013; 54(4). DOI:10.1167/iovs.12-10742 · 3.66 Impact Factor
Show more