December 1, 2021
By Geetha Sravani, PhD Candidate at the Brien Holden Vision Institute
Peripheral retinal defocus plays an important role in emmetropization and influences eye growth despite clear central vision. Optical interventions that result in myopic defocus at the peripheral retina, such as orthokeratology and multifocal contact lenses (MFCL), are associated with slower myopia progression (Schulle et al., 2018). However, such lenses may affect visual performance, and therefore it is of interest to determine if the visual acuity obtained with such lenses is comparable to single vision spectacle wear or if there is a need to vary the power of the contact lens. In the Bifocal Lenses in Nearsighted Kids (BLINK) trial, Schulle et al. (2018) measured visual acuity and spherical over-refraction required to achieve the best corrected visual acuity (BCVA) with Biofinity center distance “D” multifocal lens with high add (+2.50D). Photopic pupil size was measured using a pupilometer.
The trial included 294 children aged 7 to 11 years with myopia of -0.75D to -5.00D and astigmatism < 1D with best corrected visual acuity +0.10 logMAR or better. All the participants were fitted with 2.50D Biofinity “D” MFCL. The non-cycloplegic spherical equivalent refraction was used to determine the initial contact lens power. After the insertion, spherical over-refraction was performed monocularly to achieve best corrected visual acuity.
The spherical over-refraction required to achieve BCVA was −0.61 ± 0.24D and −0.58 ± 0.27D in the right and left eye, respectively. Visual acuity with MFCL ranged from -0.20 to +0.10 logMAR. There was no significant difference in visual acuity with over-refraction between MFCL correction and spectacle correction (difference between spectacle minus contact lens correction p=0.59). No correlation was found between the photopic pupil size and lens centration on the eye with the magnitude of overcorrection required to achieve best corrected VA.
Although not measured in this study, in a previous trial involving the same lens, even after accounting for the over-refraction, the peripheral plus power of the lens resulted in myopic defocus at most points across the peripheral retina.
In summary, the study results indicate that most children required an over-refraction of between -0.50D and -0.75D to achieve best visual acuity with Biofinity Multifocal “D” lenses. The resultant visual acuity was similar to that observed with single vision lenses. The good distance acuity combined with peripheral defocus makes it a viable candidate for myopia control.
Visual Acuity and Over-Refraction in Myopic Children Fitted with Soft Multifocal Contact Lenses
Krystal L. Schulle, David A. Berntsen, Loraine T. Sinnott, Katherine M. Bickle, Anita T. Gostovic, Gilbert E. Pierce, Lisa A. Jordan-Jones, Donald O. Mutti, Jeffrey J. Walline, for The Bifocal Lenses in Nearsighted Kids (BLINK) Study Group
Significance: Practitioners fitting contact lenses for myopia control frequently question whether a myopic child can achieve good vision with a high-add multifocal. We demonstrate that visual acuity is not different than spectacles with a commercially available, center-distance soft multifocal contact lens (Biofinity Multifocal “D”; +2.50D add).
Purpose: To determine the spherical over-refraction (SOR) necessary to obtain best-corrected visual acuity (BCVA) when fitting myopic children with a center-distance soft multifocal contact lens (MFCL).
Methods: Children (n = 294) ages 7 to 11 years with myopia (spherical component) of −0.75 D to −5.00 D (inclusive) and 1.00 D cylinder or less (corneal plane) were fitted bilaterally with +2.50 D add Biofinity “D” MFCLs. The initial MFCL power was the spherical equivalent of a standardized subjective refraction, rounded to the nearest 0.25 D step (corneal plane). A spherical over-refraction was performed monocularly (each eye) to achieve BCVA. Binocular, high contrast log MAR acuity was measured with manifest spectacle correction and MFCLs with over-refraction. Photopic pupil size was measured with a pupilometer.
Results: The mean (±SD) age was 10.3 ± 1.2 years, and the mean (±SD) SOR needed to achieve BCVA was OD: −0.61 ± 0.24 D / OS: −0.58 ± 0.27 D. There was no difference in binocular high-contrast visual acuity (logMAR) between spectacles −0.01 ± 0.06 and best-corrected MFCLs −0.01 ± 0.07 (p = 0.59). The mean (±SD) photopic pupil size (5.4 ± 0.7 mm) was not correlated with best MFCL correction or the over-refraction magnitude (both p ≥ 0.09).
Conclusions: Children achieved BCVA with +2.50 D add MFCLs that was not different than with spectacles. Children typically required an over-refraction of −0.50 D to −0.75 D to achieve BCVA. With a careful over-refraction, these +2.50 D add MFCLs provide good distance acuity, making them viable candidates for myopia control.
Schulle, K. L., Berntsen, D. A., Sinnott, L. T., Bickle, K. M., Gostovic, A. T., Pierce, G. E., … & Walline, J. J. (2018). Visual acuity and over-refraction in myopic children fitted with soft multifocal contact lenses. Optometry and vision science: official publication of the American Academy of Optometry, 95(4), 292.