Dual-focus contact lenses for myopia control modify central retinal electrophysiology in humans

INTRODUCTION

Dual-focus contact lenses create two focal planes, one providing a clear retinal image while the other imposes myopic defocus on the retina to slow myopia progression. This study used global-flash multifocal electroretinogram (gmfERG) response amplitudes to compare central versus peripheral retinal responses under dual-focus conditions and to assess the optimal degree of myopic defocus compared with a single-vision control lens.

METHODS

Twenty participants each underwent three gmfERG trials, wearing a spectacle correction over dual-focus contact lenses with plano central power and peripheral secondary focal powers of either +2.00D, +4.00D or a plano single-vision lens. We compared amplitudes and latencies of the gmfERG direct and induced components (DC and IC) within participants, between the three different contact lens powers and at different retinal eccentricities (gmfERG ring).

RESULTS

We observed significant differences in the gmfERG responses between the single-vision and dual-focus contact lenses. Overall, DC amplitudes peaked between zero and +2.00D secondary power, while IC amplitudes were maximal between +2.00D and +4.00D. Compared with the single-vision control, the greatest increase in DC and IC amplitudes while wearing dual-focus lenses occurred within the central 10° of the retina. There was no interaction effect between gmfERG ring (eccentricity) and secondary power, and no difference in the latency of the gmfERG responses between different powers.

CONCLUSION

We found that dual-focus contact lenses with a +2.00D secondary power are close to that expected to induce the greatest increase in gmfERG responses relative to a single-vision lens. Dual-focus lenses produced the highest DC and IC response amplitudes relative to a single-vision lens in the central 10° of the retina. This suggests that dual-focus contact lenses slow myopia progression by modifying central rather than peripheral retinal activity.

Changes in relative peripheral refraction in children who switched from single-vision lenses to Defocus Incorporated Multiple Segments lenses

PURPOSE

To investigate changes in relative peripheral refraction (RPR) associated with myopia progression in children who wore single-vision (SV) lenses for 2 years and switched to Defocus Incorporated Multiple Segments (DIMS) lenses in the third year versus children who wore DIMS lenses for 3 years.

METHODS

In the first 2 years, children were allocated randomly to wear either DIMS or SV lenses. In the third year, children in the DIMS group continued to wear these lenses, while those in the SV group were switched to DIMS lenses (Control-to-DIMS group). Central and peripheral refraction and axial length were monitored every 6 months.

RESULTS

Over 3 years, the DIMS group (n = 65) showed good myopia control and maintained a relatively constant and symmetrical RPR profile without significant changes. In the first 2 years, children who wore SV lenses (n = 55) showed asymmetrical RPR changes, with significant increases in hyperopic RPR at 20° nasal (N) (mean difference: 0.88 ± 1.06 D, p < 0.0001) and 30N (mean difference: 1.07 ± 1.09 D, p < 0.0001). The Control-to-DIMS group showed significant myopia retardation after wearing DIMS lenses in the third year. When compared with the RPR changes in the first 2 years, significant reductions in hyperopic RPR were observed at 20N (mean difference: -1.14 ± 1.93 D, p < 0.0001) and 30N (mean difference: -1.07 ± 1.17 D, p < 0.0001) in the third year. However, no significant difference between the RPR changes found in the nasal retina and temporal retina (p > 0.05) was noted in the third year.

CONCLUSION

Symmetrical changes in RPR were found in children switching from SV to DIMS lenses, and a symmetrical pattern of RPR was noted in children who wore DIMS for 3 years. Myopia control using myopic defocus in the mid-periphery influenced the RPR changes and retarded myopia progression by altering the eye's growth pattern.

Myopia Control Effect Is Influenced by Baseline Relative Peripheral Refraction in Children Wearing Defocus Incorporated Multiple Segments (DIMS) Spectacle Lenses

The aim of this study is to investigate if baseline relative peripheral refraction (RPR) influences the myopia control effects in Chinese myopic children wearing Defocus Incorporated Multiple Segments (DIMS) lenses. Peripheral refraction at 10°, 20°, and 30° nasal (10 N, 20 N, 30 N) and temporal (10 T, 20 T, 30 T) retina were measured at six-month intervals for children who participated in a 2-year randomized controlled trial. The relationship between the baseline peripheral refractions and myopia progression and axial length changes were analysed. A total of 79 children and 81 children in the DIMS and single vision (SV) group were investigated, respectively. In the DIMS group, more baseline myopic RPR spherical equivalent (SE) was associated with more myopic progression (10 N: r = 0.36, p = 0.001; 20 N: r = 0.35, p = 0.001) and greater axial elongation (10 N: r = −0.34, p = 0.001; 20 N: r = −0.29, p = 0.006) after adjusting for co-factors. In the SV group, baseline RPR had association with only myopia progression (10 N: r = 0.37, p = 0.001; 20 N: r = 0.36, p = 0.001; 30 N: r = 0.35, p = 0.002) but not with axial elongation after Bonferroni correction (p > 0.008). No statistically significant relationship was found between temporal retina and myopia progression or axial elongation in both groups. Children with baseline myopic RPR had statistically significant more myopia progression (mean difference around −0.40 D) and more axial elongation (mean difference 0.15 mm) when compared with the children having baseline hyperopic RPR in the DIMS group but not in the SV group. In conclusion, the baseline RPR profile may not influence future myopia progression or axial elongation for the SV lens wearers. However, DIMS lenses slowed down myopia progression and was better in myopia control for the children with baseline hyperopic RPR than the children with myopic RPR. This may partially explain why myopia control effects vary among myopic children. Customised myopic defocus for individuals may optimise myopia control effects, and further research to determine the optimal dosage, with consideration of peripheral retinal profile, is warranted.

Effect of Defocus Incorporated Multiple Segments Spectacle Lens Wear on Visual Function in Myopic Chinese Children

Purpose

To compare visual function of myopic children who had worn either defocus incorporated multiple segment (DIMS) spectacle lenses or single vision (SV) spectacle lenses over two years.

Methods

We included 160 Chinese myopic (−1 diopter [D] to −5 D) children aged 8 to 13 years in a randomized clinical trial; they wore either DIMS lenses (DIMS; n = 79) or regular SV spectacles lenses (n = 81) full time for 2 years. Visual function, including high-contrast visual acuity (VA) and low-contrast VA at distance and near, binocular functions, and accommodation, before, during, and after 2 years of spectacle wear were assessed when both groups wore SV corrections. Changes of visual function between the two groups and within groups were compared.

Results

There were no statistically significant differences in the 2-year visual function changes between DIMS and SV groups (repeated measures analysis of variance with group as factor; P > 0.05). Statistically significant improvement in the best-corrected distance high-contrast VA (P < 0.001) and stereoacuity score (P < 0.001) were found after DIMS lens wear over 2 years. Similar findings were observed after SV spectacle lens wear. For both the DIMS and SV groups, there were statistically significant decreases in accommodative lag, monocular and binocular amplitude of accommodation after two years (P < 0.01), but not in the changes in distance low-contrast VA, near high-contrast VA, near low-contrast VA, or phoria.

Conclusions

Although changes in some visual function were shown during 2 years of DIMS lens wear, similar changes were found with SV lens wear. Wear of DIMS spectacle lenses for 2 years does not adversely affect major visual function when children return to SV corrections.

Translational Relevance

DIMS spectacle lenses did not cause any adverse effects on visual function.

Defocus Incorporated Multiple Segments Spectacle Lenses Changed the Relative Peripheral Refraction: A 2-Year Randomized Clinical Trial

Purpose

To compare changes in relative peripheral refraction (RPR) associated with myopia progression in myopic children wearing Defocus Incorporated Multiple Segments (DIMS) lenses and single vision (SV) spectacle lenses over 2 years.

Methods

A 2-year double-blind, randomized controlled trial was conducted on 183 myopic children. Subjects were allocated to either wearing DIMS (n = 93) or SV spectacle lenses (n = 90). Peripheral refraction at 10°, 20°, and 30° of the nasal (10N, 20N, 30N) and temporal (10T, 20T, 30T) retinal eccentricities, central refraction, and axial length after cycloplegia were monitored every 6 months.

Results

DIMS group showed symmetrical peripheral myopic shifts between the nasal and temporal retina (comparing myopic shifts between the nasal and temporal retina, the difference between the corresponding eccentricities were nonclinically significance). SV group showed asymmetrical peripheral myopic shifts between the nasal and temporal retina, with more myopic shifts (all P ≤ 0.001) at 10T (-0.32 ± 0.62 diopters [D]), at 20T (-0.69 ± 0.95 D), and 30T (-0.85 ± 1.52 D). No significant changes in RPR spherical equivalent (M) were noted in the DIMS group, whereas significant increases (all P < 0.0001) in hyperopic RPR M were observed at 10N (0.27 ± 0.45 D), 20N (0.75 ± 0.72 D), and 30N (0.98 ± 0.76 D) in the SV group.

Conclusions

Wearing DIMS lenses resulted in a significantly different peripheral refraction profile and RPR changes, as well as significant myopia control effects when compared with SV lenses. Myopia control adopting myopic defocus in the midperiphery influenced peripheral refraction and slowed central myopia progression, most likely through alteration of overall retinal shape.

Defocus Incorporated Multiple Segments (DIMS) spectacle lenses slow myopia progression: a 2-year randomised clinical trial

AIM

To determine if 'Defocus Incorporated Multiple Segments' (DIMS) spectacle lenses slow childhood myopia progression.

METHODS

A 2-year double-masked randomised controlled trial was carried out in 183 Chinese children aged 8-13 years, with myopia between -1.00 and -5.00 D and astigmatism ≤1.50 D. Children were randomly assigned to wear DIMS (n=93) or single vision (SV) spectacle lenses (n=90). DIMS lens incorporated multiple segments with myopic defocus of +3.50 D. Refractive error (cycloplegic autorefraction) and axial length were measured at 6month intervals.

RESULTS

160 children completed the study, n=79 in the DIMS group and n=81 in the SV group. Average (SE) myopic progressions over 2 years were -0.41±0.06 D in the DIMS group and -0.85±0.08 D in the SV group. Mean (SE) axial elongation was 0.21±0.02 mm and 0.55±0.02 mm in the DIMS and SV groups, respectively. Myopia progressed 52% more slowly for children in the DIMS group compared with those in the SV group (mean difference -0.44±0.09 D, 95% CI -0.73 to -0.37, p<0.0001). Likewise, children in the DIMS group had less axial elongation by 62% than those in the SV group (mean difference 0.34±0.04 mm, 95% CI 0.22 to 0.37, p<0.0001). 21.5% children who wore DIMS lenses had no myopia progression over 2 years, but only 7.4% for those who wore SV lenses.

CONCLUSIONS

Daily wear of the DIMS lens significantly retarded myopia progression and axial elongation in myopic children. Our results demonstrated simultaneous clear vision with constant myopic defocus can slow myopia progression.

TRIAL REGISTRATION NUMBER

NCT02206217.

[Long-term results of perifocal defocus spectacle lens correction in children with progressive myopia]

Peripheral defocus plays a significant role in the formation of refraction. Perifocal spectacles allow differentiating correction of central and peripheral refraction of the eye along the horizontal meridian and can correct or reduce peripheral hyperopia.

PURPOSE

To study the long-term results of wearing perifocal spectacles on the refraction in children with progressive myopia.

MATERIAL AND METHODS

Perifocal spectacles were assigned to children of 7-14 years old with progressive myopia from -1.0 to -6.0 D in terms of refractive spherical equivalent. The children were examined before the prescription of perifocal spectacles and after 6 months, 12-18 months, 2 years, 3 years and 4-5 years. We measured visual acuity, the character of vision, refractive error before and after cycloplegia, performed biomicroscopy, ophthalmoscopy and biometry. Peripheral refraction was studied at 15° and 30° points in the nasal (N15 and N30) and temporal (T15 and T30) meridians without correction and while wearing perifocal spectacles.

RESULTS

In perifocal spectacles, in the 15° zone, 100% of the eyes formed myopic defocus, which averaged -0.05±0.1 D in T15°, -0.25±0.16 D in N15° and -0.44±0.03 D in T30°. In the N30° zone, the hypermetropic defocus decreased by 4 times and amounted to 0.38±0.03 D. The rate of progression of myopia decreased from 0.8 D of baseline values to 0.17 D at 4-5 years of follow-up. After 6 months of wearing perifocal spectacles, the refraction gain was -0.2±0.02 D (in the control group it was -0.38±0.04 D), after 12-18 months - (-)0.38±0.04 D (-0.63±0.09 D in the control group), after 2 years - (-)0,78±0,06 D (-1.18±0,15 D in the control group), after 3 years - (-)0.99±0.12 D (-1.65±0.20D in the control group). During the 4-5 years of the follow-up, the refractive error in the main group was -1.16±0.2 D, which is 60% less than in the control group (-1.95±0.2 D).

CONCLUSION

Constant wearing of perifocal spectacles reduces the rate of myopia progression in children by 4.5 times compared with the initial rate, and by 1.6 times (by 60%) in comparison with the control group. Perifocal spectacles are recommended as optical means to slow the progression of myopia.

Regional alterations in human choroidal thickness in response to short-term monocular hemifield myopic defocus

PURPOSE

To examine the regional changes in human choroidal thickness following short-term exposure to hemifield myopic defocus using optical coherence tomography (OCT).

METHODS

The central 26˚ visual field of the left eye of 25 healthy young adults (mean age 26 ± 5 years) was exposed to 60 min of clear vision (control session), +3 D full-field, +3 D superior retinal and +3 D inferior retinal myopic defocus, with the right eye occluded. Choroidal thickness across the central 5 mm (17°) macular region was examined before and after 60 min of defocus using a high-resolution, foveal centred vertical OCT line scan, with optical defocus simultaneously imposed using a Badal optometer and cold mirror system mounted on a Spectralis OCT device.

RESULTS

Averaged across the central 5 mm macular area, choroidal thickness decreased by -4 ± 7 μm during the control session (p = 0.01), most likely due to the unique stimulus conditions of this study. The mean macular choroidal thickness increased during full-field (+2 ± 8 μm), inferior retinal (+3 ± 7 μm) and superior retinal myopic defocus (+5 ± 9 μm), representing a significant thickening of the choroid compared to the control session (all p < 0.05). The defocus induced changes in macular choroidal thickness differed between the superior and inferior hemiretinal regions (F_{2.26, 54.27}  = 29.75, p < 0.001). When only the superior retina was exposed to myopic defocus, the choroid thickened in the superior region (+7 ± 8 μm, p < 0.001), but did not change significantly in the inferior region (+3 ± 9 μm, p = 0.12). When only the inferior retina was exposed to myopic defocus, the choroid thickened inferiorly (+4 ± 8 μm, p = 0.005), with no significant change observed in the superior region (+1 ± 8 μm, p = 0.46).

CONCLUSIONS

These findings provide evidence supporting a local regional choroidal response to myopic defocus in the human eye, with hemifield myopic defocus leading to significant thickening of the choroid localised to the retinal region exposed to defocus. The novel finding of a localised response of the human choroid to hemifield myopic defocus, particularly in the superior hemiretina, may have important implications in optimising the optical design of myopia control interventions.