Accommodative behaviour and retinal defocus in highly myopic eyes fitted with a dual focus myopia control contact lens

Abstract

Purpose: To evaluate the myopic and hyperopic defocus delivered to the retina by a dual focus (DF) myopia control contact lens when myopia exceeds 6.00 D.

Methods: Individuals with high myopia were fitted bilaterally with high-powered DF lenses containing power profiles matching a Coopervision MiSight 1 day contact lens (omafilcon A) and a Coopervision Proclear 1 day single vision (SV) lens. Wavefront measurements along the primary line of sight and across the central ±20° of the horizontal retina were acquired using a pyramidal aberrometer, while subjects accommodated to high-contrast letter stimuli (6/12 equivalent) at six target vergences (-0.25 and -1.00 to -5.00 D). Linear mixed-effects regression models explored the relationship between the spherical equivalent refractive error (SERE) and induced defocus.

Results: Thirteen teenagers and young adults (ages 13-32 years, mean [standard deviation, SD] age = 22.8 [4.9] years) with high myopia (SERE -6.50 to -9.25 D) were tested. The treatment optic zone of the DF lens shifted retinal defocus by the expected -2.00 D, with a mean (SD) difference (DF-SV) of -2.21 (0.18) D for the inner treatment ring. Inclusion of the treatment optic had no significant impact on accommodative accuracy (p = 0.51). Accommodative lags were larger at the nearer viewing distances, with lag increasing by approximately 0.30 D for every additional dioptre of SERE. Measured retinal defocus within the annular treatment zone was approximately -2.00 D at the foveal centre, 10° nasal and temporal and 20° nasal and reduced to -1.90 (0.57) D at 20° temporal.

Conclusions: Relative to eyes with lower levels of myopia, the increased accommodative lags and more prolate retinas of highly myopic eyes reduced the myopic retinal defocus from the DF myopia control lens, while the treatment optical zones generated the combined effect of reducing hyperopic and introducing myopic retinal defocus relative to an SV correction.

Keywords: accommodative behaviour; contact lenses; dual focus contact lenses; high myopia; myopia control; retinal defocus.

FIGURE 1

Experimental set‐up featuring the Osiris aberrometer aligned to the right eye's primary line of sight with 0.30 logMAR fixation targets located at target vergences (TV) of −0.25 D, and −1.00 to −5.00 D in 1.00 D steps. Fixation targets were positioned either coaxial to the measurement axis or ±10° or ±20° to the right or left at a TV = −1.00 D.

FIGURE 2

Sample refractive state maps from one subject's right eye while wearing the dual‐focus lens measured along the primary line of sight at six target vergences (TV) (top row) and five horizontal retinal eccentricities for a −1 D TV (bottom row). D, dioptres; N, nasal retina; T, temporal retina.

FIGURE 3

Refractive state is plotted as a function of minus target vergence (a, b) and as a function of retinal eccentricity at −1.00 D target vergence (c, d) for eyes fitted with either the dual‐focus lens dual focus (DF) (a, c) or single vision (SV) lenses (b, d). Refractive states averaged across geometric zones corresponding to the centre zone (CZ) (blue) and the annular ring 1 (R1) treatment zone (red) regions of the DF lens are plotted for each of the 13 individual eyes (narrow lines) and the sample mean ± SD (bold lines). Using the same geometrical pupil locations and colour code, parallel data are plotted for eyes fitted with SV lenses. The black dashed line in a and b represents the 1:1 line.

FIGURE 4

Retinal defocus (refractive state – target vergence) plotted as a function of target vergence (a) and retinal eccentricity at −1.00 D target vergence (b) for both the centre zone (CZ) and ring 1 (R1) of the dual focus (DF) and single vision (SV) lenses.

FIGURE 5

Retinal defocus (dioptres, D) for 13 participants wearing dual focus (DF) lenses plotted as a function of spherical equivalent refractive error (SERE, dioptres [D]) for the six target vergences measured. Defocus values for the correction zones, centre zone (CZ) (blue circles) and ring 2 (R2) (blue triangles) are compared with defocus generated by treatment zones (red circles) ring 1 (R1) and ring 3 (R3) (red diamonds). Solid lines are fitted regressions to CZ and R1 data.

FIGURE 6

Retinal defocus (dioptres, D) for 13 participants wearing dual focus (DF) lenses plotted as a function of spherical equivalent refractive error (SERE, dioptres [D]) for five central retinal locations at −1.00 D target vergence. Defocus values for the correction zones, centre zone (CZ) (blue circles) and ring 2 (R2) (blue triangles) were compared with defocus generated by treatment zones ring 1 (R1) (red circles) and ring 3 (R3) (red diamonds). Solid lines are fitted regressions to CZ and R1 data. N, nasal; T, temporal.

FIGURE 7

Kernel density plots representing the proportion of pupil area exhibiting hyperopic (coral) retinal defocus, emmetropic focus (blue) and myopic (red) retinal defocus (dioptres, D) plotted separately for each target vergence for eyes fitted with the single vision (SV) lens (top) or dual‐focus (DF) lens (bottom). TV, target vergence.