The effect of simultaneous negative and positive defocus on eye growth and development of refractive state in marmosets

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.

Conflict of interest statement

Disclosure: A. Benavente-Perez, None; A. Nour, None; D. Troilo, None

Figures

Figure 1.

Spherical equivalent refractive state (D) and VC depth (mm) over time on treated eyes (solid symbols and lines) and contralateral control eyes (empty symbols, dotted lines). Solid and empty black symbols: those treated and contralateral eyes, respectively, that remained hyperopic after the end of treatment. Solid and empty red symbols: the animals that had myopia on both eyes after treatment. Grey cloud: 95% confidence interval (CI) from age-matched untreated marmosets, calculated as the average ±2 SD. Note that several eyes began the experiment with slightly more myopia than that normally seen in control animals, but the eye size as measured as VC depth fell within normal range.

Figure 2.

Interocular differences (treated eye-control eye) at pretreatment (pre-treat), baseline (arrow), and during treatment (T1–T4) in refractive error (D) and VC depth (mm) in multizone lens-reared animals. Each line represents one animal, and each symbol indicates the measurement point in time. Grey cloud: 95% CI from age-matched untreated marmosets, calculated as the average ±2 SD.

Figure 3.

Quadrant plot describing the relation between interocular differences (exp-control) in vitreous chamber depth (x axis), and refraction (y axis) in the multizone-lens reared group. The refractive and growth changes of each animal are represented with a line that starts at the baseline measurement and finishes at the last measurement after treatment (arrowhead), plotted over a grey cloud that represents the 95% CI of the age-matched untreated data. Lines outside of the 95% CI indicate significant changes. Data points in the top left quadrant indicate eyes that are smaller and more hyperopic than contralateral control eyes, points in the top right quadrant indicate eyes that are larger but more hyperopic, points in the bottom left quadrant show eyes that are smaller but more myopic than contralateral controls, and points in the bottom right quadrant show eyes that are larger and more myopic.

Figure 4.

Quadrant plots describing the relation between interocular differences (exp-control) in vitreous chamber depth (x axis), and refraction (y axis) in the positive single-vision reared group (blue arrows), and in the negative single-vision reared group (red arrows). For detailed explanation of the graphs, see Figure 3 caption.

Figure 5.

Growth rates in multizone lens-reared marmosets (black), untreated (white), and single vision lens-reared marmosets (positive, blue and negative, red). Before treatment (pretreatment) and at early, mid, and late time intervals during treatment. The data are given as box plots, where the top and bottom end of the box represent the 25th and 75th percentile of the data, and the error bars represent the SD. The underlying dots represent individual data points, and the horizontal line represents the mean.