The Effects of Center-near and Center-distance Multifocal Contact Lenses on Peripheral Defocus and Visual Acuity

Advances in the study of the influence of photoreceptors on the development of myopia

This review examines the pivotal role of photoreceptor cells in ocular refraction development, focusing on dopamine (DA) as a key neurotransmitter. Contrary to the earlier view favoring cone cells, recent studies have highlighted the substantial contributions of both rod and cone cells to the visual signaling pathways that influence ocular refractive development. Notably, rod cells appeared to play a central role. Photoreceptor cells interact intricately with circadian rhythms, color vision pathways, and other neurotransmitters, all of which are crucial for the complex mechanisms driving the development of myopia. This review emphasizes that ocular refractive development results from a coordinated interplay between diverse cell types, signaling pathways, and neurotransmitters. This perspective has significant implications for unraveling the complex mechanisms underlying myopia and aiding in the development of more effective prevention and treatment strategies.

The induced defocus by Defocus Incorporated Soft Contact lenses is dependent on visual distance and ambient illuminance

PURPOSE

Defocus Incorporated Soft Contact (DISC) lenses, a commonly used type of multifocal lens in clinical practice, may slow down myopia progression by inducing myopic retinal defocus. The purpose of this study was to explore whether the induced defocus across the retina could be affected by visual environments encountered in the real world, such as differences in viewing distance and ambient illuminance.

METHODS

In this cross-over trial, 30 myopic adults wore both DISC lenses and single vision contact (SVC) lenses in random order. An open-view Hartmann-Shack scanning wavefront sensor was used to measure defocus at different retinal locations along the horizontal meridian under four experimental conditions: far target (3 m) and near targets (0.33 m) under scotopic (<1 lux) or photopic (~300 lux) conditions.

RESULTS

The results showed that DISC lenses induced more myopic retinal defocus than SVC lenses in all conditions (all p < 0.05), except for the scotopic near target. In addition, for DISC lenses, the defocus was greater in the photopic than the scotopic conditions for both the far and near targets (both p < 0.05).

CONCLUSION

In conclusion, the retinal defocus induced by these multifocal lenses was dependent on both visual distance and ambient illuminance, indicating that the visual conditions might affect the anti-myopia efficacy of these devices.

Refractive power profiles of commercially available soft multifocal contact lenses for myopia control

PURPOSE

Lens power profiles can provide valuable insights on the imposed optical defocus and visual experience of contact lens wearers, especially in the context of myopia control. This study measured the refractive power profiles of multifocal soft contact lenses (MFCLs) currently used or that have the potential for use in myopia control using high spatial resolution aberrometry. The instrument's repeatability for determining MFCLs power profiles was also assessed.

METHOD

The power profiles of 10 MFCLs of various designs (centre-distance, centre-near and extended depth of focus) were measured using the Lambda-X NIMOEVO, a phase shifting Schlieren-based device. Power profiles were graphically expressed as measured power at each chord position and the maximum add power was calculated. The repeatability of the NIMOEVO was expressed as the within-subject standard deviation at each chord position for a subset of five MFCLs.

RESULTS

The measured distance powers differed from nominal powers for more than half of the MFCLs with a definable distance zone. There were variations in the chord position of the distance and near correction zones, rate of power transitions and calculated maximum add between the MFCLs which did not depend on lens design. For half of the MFCLs, the power profile shape was inconsistent between different nominal back vertex powers of the same design. The repeatability of the NIMOEVO was dependent on the lens design, with designs featuring faster rates of power change exhibiting worse repeatability.

CONCLUSIONS

Significant differences in MFCL power profiles were found which were not adequately represented in labelling. This is likely due to the small number of parameters used to define lens power characteristics. Eye health care practitioners should be aware of potential differences in power profiles between different MFCLs, which will impact the retinal defocus introduced during lens wear and the wearer's visual experience.

Treatment of Rapid Progression of Myopia: Topical Atropine 0.05% and MF60 Contact Lenses

This retrospective study evaluates the effectiveness of combining 0.05% atropine with MF60 contact lenses in managing rapid myopia progression in children over one year. The study involved three groups: the treatment group (TG) with 15 children (53% male, average age 12.9 ± 1.04), the MF group (MF) with 12 children (50% male, average age 12.8 ± 0.8) using only MF60 lenses, and the control group (CG) with 14 children (43% male, average age 12.1 ± 0.76). Baseline myopia and axial length (AL) were similar across groups, with the TG, MF, and CG showing -4.02 ± 0.70 D, -4.18 ± 0.89 D, -3.86 ± 0.99 D, and 24.72 ± 0.73 mm, 24.98 ± 0.70 mm, 24.59 ± 1.02 mm, respectively. Prior to the study, all groups exhibited significant myopia and AL progression, with no previous myopia control management. The treatment involved daily 0.05% atropine instillation, the use of MF60 lenses and increased outdoor activity. Biannual cycloplegic refraction and slit lamp evaluations confirmed no adverse reactions. After one year, the TG showed a significant reduction in myopia and AL progression (-0.43 ± 0.46 D, p < 0.01; 0.22 ± 0.23 mm, p < 0.01), whereas the CG showed minimal change (-1.30 ± 0.43 D, p = 0.36; 0.65 ± 0.35 mm, p = 0.533). The MF group also exhibited a notable decrease (-0.74 ± 0.45 D, p < 0.01; 0.36 ± 0.23 mm). Increased outdoor activity during the treatment year did not significantly impact myopia control, suggesting its limited additional effect in this cohort. The study concludes that the combination of 0.05% atropine and peripheral defocus soft contact lenses effectively controls myopia progression in children.

Peripheral Defocus, Pupil Size, and Axial Eye Growth in Children Wearing Soft Multifocal Contact Lenses in the BLINK Study

Purpose

The purpose of this study was to evaluate the relationship between peripheral defocus and pupil size on axial growth in children randomly assigned to wear either single vision contact lenses, +1.50 diopter (D), or +2.50 D addition multifocal contact lenses (MFCLs).

Methods

Children 7 to 11 years old with myopia (-0.75 to -5.00 D; spherical component) and ≤1.00 D astigmatism were enrolled. Autorefraction (horizontal meridian; right eye) was measured annually wearing contact lenses centrally and ±20 degrees, ±30 degrees, and ±40 degrees from the line of sight at near and distance. Photopic and mesopic pupil size were measured. The effects of peripheral defocus, treatment group, and pupil size on the 3-year change in axial length were modeled using multiple variables that evaluated defocus across the retina.

Results

Although several peripheral defocus variables were associated with slower axial growth with MFCLs, they were either no longer significant or not meaningfully associated with eye growth after the treatment group was included in the model. The treatment group assignment better explained the slower eye growth with +2.50 MFCLs than peripheral defocus. Photopic and mesopic pupil size did not modify eye growth with the +2.50 MFCL (all P ≥ 0.37).

Conclusions

The optical signal causing slower axial elongation with +2.50 MFCLs is better explained by the lens type worn than by peripheral defocus. The signal might be something other than peripheral defocus, or there is not a linear dose-response relationship within treatment groups. We found no evidence to support pupil size as a criterion when deciding which myopic children to treat with MFCLs.

Impact of zone geometry on the introduction of myopic defocus in young adult eyes wearing multi-zone lenses

PURPOSE

Multizone contact lenses control myopia progression by proposed introduction of myopic defocus. This project investigated how much of the pupil area and how many dioptres of myopic defocus are introduced by different lens zone geometries with near- and off-axis viewing.

METHODS

Ten young myopic adults (18-25 years) binocularly wore four soft contact lenses including a single vision (SV), concentric-ring dual-focus (DF), centre-distance multifocal (MF) and a RingBoost™ (RB) multi-zone design containing a combination of coaxial and non-coaxial zones. A modified aberrometer captured aberrations and pupil sizes at four target vergences between -0.25 and -4.00 D (on-axis) and across the central ±30° of the horizontal retina (off-axis). Defocus was quantified as the difference between the measured refractive state and the target vergence within each zone of a multi-zone design within the pupil and compared with that of equivalent zone areas of the SV lens. The percentage of the pupil containing myopic defocused light for each lens was calculated.

RESULTS

Defocus within the distance correction zones of multi-zone lenses was similar to that of the SV lens. When viewing on-axis at -0.25 D target vergence, on average 11% of the pupil was myopic with SV, whereas 62%, 84% and 50% of the pupil was myopic for the DF, MF and RB designs, respectively. At -4.00 D target vergence, all lenses exhibited a systematic decrease in the percentage of pupil area having myopic defocus (SV: 3%; DF: 18%; MF: 5% and RB: 26%). The off-axis proportions were similar across multi-zone lenses; however, multi-zone lenses retained approximately 1.25-3.0× more myopic defocus than the SV lens.

CONCLUSIONS

Subjects accommodated using the distance-correction zones of multi-zone lenses. Multi-zone contact lenses introduced significant myopic defocus on-axis and across the central ±30° retina. However, the magnitude and proportion of defocus were influenced by zone geometry, add power and pupil size.

Photopic pupil size change in myopic orthokeratology and its influence on axial length elongation

AIM

To explore the photopic pupil size behavior in myopic children undergoing overnight orthokeratology (ortho-k) over 1-year period and its effects on the axial elongation.

METHODS

A total of 202 Chinese myopic children were enrolled in this prospective clinical trial. Ninety-five subjects in ortho-k group and eighty-eight subjects in spectacle group completed the 1-year study. Axial length (AL) was measured before enrollment and every 6mo after the start of ortho-k. The photopic pupil diameter (PPD) was determined using the Pentacam AXL and measured in an examination room with lighting of 300-310 Lx. Stepwise multiple linear regression analysis was used to identify variables contribution to axial elongation.

RESULTS

Compared with spectacle group, the average 1-year axial elongation was significantly slower in the ortho-k group (0.25±0.27 vs 0.44±0.23 mm, P<0.0001). In ortho-k group, PPDs significantly decreased from 4.21±0.62 mm to 3.94±0.53 mm after 1mo of lens wear (P=0.001, Bonferroni correction) and the change lasts for 3-month visit. No significantly change during the other follow-up visits was found (P>0.05, Bonferroni correction). The 4.81 mm PPD may be a possible cutoff point in the ortho-k group. Subjects with PPD below or equal to 4.81 mm tended to have smaller axial elongation compared to subjects with PPD above 4.81 mm after 1-year period (t=-3.09, P=0.003). In ortho-k group, univariate analyses indicated that those with older age, greater degree of myopia, longer AL, smaller baseline PPD (PPD_baseline) experienced a smaller change in AL. In multivariate analyses, older age, greater AL and smaller PPD_baseline were associated with smaller increases in AL. In spectacle group, PPD tended to be stable (P>0.05, Bonferroni correction) and did not affect axial growth.

CONCLUSION

PPDs experience significantly decreases at 1-month and 3-month ortho-k treatment. Children with smaller PPD tend to experience slower axial elongation and may benefit more from ortho-k.

Multifocal contact lens myopia control: central and peripheral retinal image quality

CLINICAL RELEVANCE

That myopic defocus, even if restricted to the peripheral retina, inhibits eye growth in young monkey eyes has motivated the therapy of myopia control through multifocal contact lens wear in children.

BACKGROUND

To understand how eye-length regulating mechanisms are triggered by light requires knowledge of retinal light spread. That is largely lacking for the multifocal contact lenses used in the therapy because empirical methods identifying just the defocus in dioptres are inadequate.

METHODS

"Through-focus" diffraction computations in contact lens/eye models with typical normal eye parameters, including polychromatic light, the chromatic aberrations and an M-cone phototransduction layer, offer estimates of retinal image spread for a range of viewing distances.

RESULTS

Point- and edge-spread distributions of activation of phototransduction in the central retina show that the addition of multifocal zones produces some veiling for in-focus viewing and substantial improvement of image quality for near targets in the unaccommodated eye. These effects are much reduced in the retinal periphery.

CONCLUSION

Whatever therapeutic value there is in prescribing multifocal contact lenses for myopia control, it is not particularly dependent on the precise configuration of the multifocal zones, nor can it be ascribed to changes in image quality specific to the retinal periphery; its origin is more likely less blur for near targets, reducing the stimulus to accommodation.