MiSight’s Impact on Binocular and Accommodative Function

Authors: Alicia Ruiz-Pomeda (1), Belen Perez-Sanchez (2), Pilar Canadas (3), Francisco Luis Prieto-Garrido (4), Ramon Gutierrez-Ortega (5), Cesar Villa-Collar (1)

1. Faculty of Biomedical and Health Sciences, Department of Pharmacy, Biotechnology, Nutrition, Optics and Optometry, European University of Madrid, Madrid, Spain
2. Department of Statistics, Mathematics and Information, Area of Languages and Computer Systems, Miguel Hernandez University of Elche, Alacant, Spain
3. Ocular Surface Group, Institute of Applicate Ophthalmobiology (IOBA), Department of Theoretical Physics, Atomic and Optic, University of Vallodolid, Valladolid, Spain
4. Department Optics I: Optometry and Vision, Universidad Complutense de Madrid, Madrid, Spain
5. Clinica oftalmologica Novovision, Madrid, Spain

Date: 2019

Reference: Graefe’s Archive for Clinical and Experimental Ophthalmology. 2019; 257:207-215. [Link to open access paper]

It is crucial to understand the accommodative and binocular behaviour of young eyes while wearing multi-focal contact lenses (MFCL's) for myopia control. This is important for two reasons. Firstly, alterations to accommodative behaviour can have implications on the induced sign and magnitude of peripheral retinal defocus, and consequently efficacy in myopia control. Secondly, MFCL's were designed to be worn by adults, and children are known to have very different accommodative and binocular systems.¹ The purpose  of this 2 year study was to determine the effect of MiSight contact lenses used to control myopia on binocular vision and accommodation in children, as compared with children wearing SV spectacles, with the researches finding no significant differences in binocular and accommodative measures between the study groups.

None of the ocular parameters of binocular vision and accommodation for the MiSight group underwent significant changes across the 2 year period.

• Some studies have observed decreased accommodative response (increased lag) in children wearing MFCL's.²  It has been postulated that children "utilise" the near portion of the contact lens to relax their accommodative response, thereby negating the myopia control effect as hyperopic retinal defocus is induced by the distance portion of the lens.³ However, this phenomenon was not observed in this study. Similar findings of unchanged binocular functioning with MFCL wear has been reported in other studies.³ 
• Based on these findings, when prescribing MiSight for myopia control in a child aged 8-12 years, eye care practitioners should not anticipate a change in their patients binocular or accommodative function.

Myopia progression was higher (p<0.005) in the single vision group than in the MiSight group, supporting the efficacy of MiSight in reducing myopia progression.

• Examining the efficacy of MiSight was not the primary intention of this paper; however, it acts as additional evidence that Eye care practitioners can utilise when discussing MiSight with patients and their parents.

In the control group, amplitude of accommodation and accommodative response at 33cm (3D) and 25cm (4D) were greater at 24 month visit compared with baseline (p<0.05).

• This indicates that the accommodative ability of the single vision group decreased during the 2 years. Other studies have reported similar findings, in that accommodative response decreases with age.⁴ Accommodative lag is often reported to be characteristic of the accommodative behaviour of young myopes.^5,6
  
  

The design of the study potentially affected the credibility of the results obtained. 

• Single vision spectacles were utilised as the control group, rather than single vision contact lenses. Using single vision contact lenses in the control group may have potentially reduced confusion when comparing results between the groups, as the accommodative response is known to differ when wearing spectacles and contact lenses.⁷ 
• Both groups wore their best subjective refraction in a trial frame while their binocular and accommodative function was examined. While it is unlikely that the accommodative/binocular function would change in the few hours without contact lens wear, this could potentially affect the results obtained. 
• There is potential bias introduced in the study, as neither the subjects nor the investigators were blinded, as it was apparent if a child was in the single vision or control group. 

Accommodative response has been demonstrated to change with age.⁴ At baseline, there was a significant difference in age between groups. This discrepancy complicated the direct comparison of accommodative behaviour between the two groups.

Five subjects dropped out from MiSight group during the two year study; however, no subjects dropped out from the single vision group. Reasons for drop-out were not included in the study, which would have provided further insight into tolerance and potential adverse events when wearing MiSight lens.

To evaluate the binocular and accommodative function in children wearing MiSight contact lenses for myopia control compared with children wearing single vision (SV) spectacles.

This is a randomised controlled clinical trial involving children aged 8-12 years, with myopia ranging from -0.75D to -4.00D and astigmatism <1.00DC. Subjects were allocated to MiSight study group or control group wearing SV spectacles. Binocular and accommodative function was determined at baseline, 12 and 24 month visits, and was assessed by distance and near horizontal phoria, accommodative convergence/accommodation (AC/A) ratio, stereopsis, accommodative amplitude (AA) and accommodative response (AR) at 33, 25 and 20cm.

• Groups
  • MiSight Group (n start, end= 46, 41): follow up at 1 week, then 1, 6, 12, 24 months
    • Subjects were asked to wear their lenses at least 6 days per week, without exceeding 15 hours/day. At the 24 months visit, wear time was 11.69±2.12 from Monday to Friday and 8.45±4.50 on weekend. Average number of days/week of wear at 24 months was 6.32±1.08. 
• Control Group (single vision spectacles) (n start, end= 33, 33): follow up at baseline, 6, 12, 18 and 24 months
  • Subjects were asked to wear their spectacles full time 

Baseline, 12 and 24 month visits included case history, habitual and best-corrected visual acuity measured using 4m and 40cm ETDRS charts. Various methods of refraction were conducted, including cycloplegic and non-cycloplegic autorefraction, as well as manifest subjective refraction. Biomicroscopy and fluorescein assessment was conducted, as well as binocular indirect ophthalmoscopy. Axial length, anterior chamber depth and corneal power using IOL master were measured. 

Binocular and accommodative examination was assessed with subjects wearing a trial-frame with best subjective refraction. Unilateral and alternating cover test was conducted at both distance (4m) and near (40cm), with magnitude and direction of neutralising prisms recorded. Inter-pupillary distance (mm) was recorded with an interpupillometric ruler. AC/A ratio was assessed using the calculated method, and the near point of convergence (NPC) measured using the push-up technique (both break and recovery). Stereoacuity was measured using randot with polarising spectacles. Accommodative response was measured using binocular autorefractor WAM-5500 (Grand Seiko) at 33cm, 25cm and 20cm, providing accommodative demands of 3D, 4D and 5D respectively. Binocular push-up accommodation was measured using Donder's push up method.

74 children completed the study, 41 wearing MiSight, 33 wearing SV spectacles. Inter-pupillary distance increased across the duration of the study for both groups, as could be expected due to the growth of the subjects in 2 years. 

In the single vision group, distance and near phoria, stereopsis, AC/A and accommodative response at 20cm did not show any significant change; however, there was a statistically significant change in accommodative amplitude and response at 3D and 4D for the single vision group.

No statistically significant difference was reported in accommodative response between single vision and MiSight group, except for at 25cm at baseline, in which the single vision group was greater. It is difficult to interpret this finding, as similar results were not observed at 33cm or 25cm.  

Mean distance phoria for both groups were more exophoric over time, although this result was not statistically significant.

Mean near phoria for MiSight at baseline was esophoric, orthophoric at 12 months and exophoric at end. The authors noted an exophoric tendency after wearing MiSIght contact lenses. However, this result was not statistically significant, and featured very high standard deviations, which diminishes the credibility of the finding. The authors postulate that this could indicate that the MiSight children are utilising positive addition provided by the multi-focal design to relax their accommodation,^2,8 however, this was not observed in the study.

Mean NPC, AC/A and stereopsis presented normal values in both groups at all follow ups, and there was no significant differences between groups over time. 

Results from this study are in agreement with previous reports indicating  that MiSight contact lenses are an effective treatment for myopia control in children,⁹ and indicate that MiSight does not induce changes in binocular and accommodative function over 2 years of follow up compared to wearing single vision glasses. 

Title: Binocular and accommodative function in the controlled randomised clinical trial MiSight Assessment Study Spain (MASS)

Authors: Alicia Ruiz-Pomeda (1), Belen Perez-Sanchez (2), Pilar Canadas (3), Francisco Luis Prieto-Garrido (4), Ramon Gutierrez-Ortega (5), Cesar Villa-Collar (1)

Purpose: The purpose of this study was to quantify the effectiveness of MiSight daily disposable soft contact lens in slowing the progression of juvenile-onset myopia.

Methods: Myopic children (spherical equivalent refraction, −0.75 to −4.00 D; astigmatism, <1.00 D) aged 8 to 12 years with no prior contact lens experience were enrolled in a 3-year, double-masked, randomized clinical trial at four investigational sites in four countries. Subjects in each group were matched for age, sex, and ethnicity and were randomized to either a MiSight 1-day contact lens (test) or Proclear 1-day (control; omafilcon A) and worn on a daily disposable basis. Primary outcome measures were the change in cycloplegic spherical equivalent refraction and axial length.

Results: Of the subjects enrolled, 75.5% (109/144) completed the clinical trial (53 test, 56 control). Unadjusted change in spherical equivalent refraction was −0.73 D (59%) less in the test group than in the control group (−0.51 ± 0.64 vs. -1.24 ± 0.61 D, P < .001). Mean change in axial length was 0.32 mm (52%) less in the test group than in the control group (0.30 ± 0.27 vs. 0.62 ± 0.30 mm, P < .001). Changes in spherical equivalent refraction and axial length were highly correlated (r = −0.90, P < .001). Over the course of the study, there were no cases of serious ocular adverse events reported. Four asymptomatic corneal infiltrative (one test, three control) events were observed at scheduled study visits.

Conclusion: Results of this clinical trial demonstrate the effectiveness of the MiSight daily disposable soft contact lens in slowing change in spherical equivalent refraction and axial length.

[Link to open access paper]