New designs and paradigms in myopia spectacles – Q&A with Prof. Padmaja Sankaridurg

Building on decades of successful development and application of cutting-edge myopia management solutions in Asia, ZEISS MyoCare technology is the latest advance in ZEISS’s myopia portfolio. This new solution developed in cooperation with Wenzhou Medical University, China is designed to introduce competing myopic defocus at the retina to effectively slow the progression of myopia. ZEISS MyoCare technology integrates two advanced lens concepts to actively slow progression of myopia and to optimise visual performance:

1. The lens design incorporates a central zone for vision correction.
2. Surrounding this central zone is a treatment zone, that includes Cylindrical Annular Refractive Elements, also referred to as C.A.R.E. These elements have relatively more positive power compared to the base surface power, are arranged in concentric rings, and are alternated between the clear zones to enhance the performance of the lens.

Due to distinct geometry of the cylindrical elements, light passing through the C.A.R.E. elements does not refract to a single point. Instead, it creates a blended distribution of myopic defocus in front of the retina. The myopic defocus is thought to slow myopia progression.^1-4  Furthermore, ZEISS MyoCare technology features a non-spherical back surface design that incorporates a point-by-point optimization and referred to as  ZEISS ClearFocus design. In contrast to a traditional single vision spectacle lens where myopic eyes experience hyperopic defocus due to lens aberrations especially towards the lens periphery, the ClearFocus design of the ZEISS MyoCare lens aims to minimize these aberrations and allow for visual clarity and myopic defocus across all gaze directions.

The two designs referred to as ZEISS MyoCare and MyoCare S are tailored to address the needs of the growing eye. Whilst it is crucial to provide a sizeable treatment zone to ensure that competing myopic defocus is present across a substantial region of the retina, the size of the central zone is significant for visual performance.   Additionally, the strength or the dioptric power of the cylindrical annual refractive elements as well as the proportion of the surface area occupied by these elements are also important for myopia management. Following wearability and visual performance assessments, two design variants ZEISS MyoCare and MyoCare S were selected for efficacy evaluations. ZEISS MyoCare incorporates a 7 mm central zone, while the softer ZEISS MyoCare S incorporates a 9 mm central zone. Furthermore, the nominal power of the cylindrical annual refractive elements for ZEISS MyoCare is +9.2D that translates to a mean relative surface power of +4.6D, whereas with ZEISS MyoCare S, the nominal power is +7.6D and translates to a mean relative surface power of +3.8D.

Multiple clinical trials with approximately 1700 children are currently underway across both Asia and Europe.^5-6  Based on interim data from a prospective clinical trial at Wenzhou University Eye Hospital involving 240 children randomised to ZEISS MyoCare, MyoCare S or single vision spectacles, all children reported adaptation to their lenses within a day. This was regardless of whether they wore test or control lenses. At 3 months of lens wear (first visit after dispensing), 97.5% or more of children wearing MyoCare or MyoCare S reported their vision for distance, near, during sporting activities, perception of moving objects and going up and down stairs to be very good (on a scale of 1-4 where 1 = very poor and 4 = very good). Additionally, an interim analysis was conducted on the 12-month efficacy of these lenses. The performance was benchmarked against the eye growth of an emmetropic eye using the “emmetropic progression ratio”. With this metric, a value of 100% indicates eye growth similar to that of an emmetropic eye, while 0% indicates eye growth similar to that of a myopic eye wearing single vision spectacle lens. Both ZEISS MyoCare and MyoCare S slowed eye growth across all ages assessed.  In younger children aged 7 to 9 years, ZEISS MyoCare demonstrated an emmetropic progression ratio of 63% and in older children aged 10 to 12 years ZEISS MyoCare S demonstrated an emmetropic progression ratio of 86% (ZEISS Vision Care, data on file).

I would like to use this opportunity to clarify that the results published in the article by Liu et al.  titled “One-year myopia control efficacy of cylindrical annular refractive element spectacle lenses" and published in Acta Ophthalmologica, 101(6), 2023 do not refer to or  reflect the performance of ZEISS MyoCare or MyoCare S. The design used in the published article refers to an earlier prototype that served as a starting point for optimisation.⁷  

Our knowledge of eye growth indicates that even in emmetropic or non-myopic eyes, there is continued axial elongation during childhood and early teenage years. Eye growth is highest in young children and progressively slows with age. This rate of axial elongation in emmetropic or non-myopic eyes is considerably lower compared to a myopic eye. It appears that axial elongation serves to balance the refractive power of different ocular components thus guiding the eye to an emmetropic state.  Based on these observations, it appears that it might be more realistic to focus on slowing axial elongation in myopic eyes to the physiological axial elongation rates observed in emmetropic eyes.  

Currently, much of the reporting of the efficacy of myopia control treatments is based on the difference in progression between test and control groups. In other words, performance of the myopia control strategies is benchmarked against progression observed with a myopic eye wearing single vision spectacles.  Developed by Ohlendorf and colleagues at ZEISS, the new metric ”Emmetropic Progression Ratio (EPR)” determines how close an eye with a myopia control intervention approaches physiological emmetropic growth. EPR is calculated as:

On this metric, 100% indicates that the eye growth is similar to that of an emmetropic eye and 0% indicates that the eye growth is similar to that of a myopic eye wearing single vision spectacles.

For example, if the annual axial elongation of a myopic eye is 0.35mm and that of a non-myopic eye is 0.10 mm and if with a myopia control intervention, the axial elongation is 0.20mm, then:

In both Asia and Europe, multiple trials are currently in progress to assess the safety, efficacy, and subjective performance of ZEISS MyoCare technology through both single-centre and multi-centre randomised clinical trials. In China, approximately 1400 children are enrolled in these trials⁶ and in Europe, a multi-centre clinical trial with 300 participants is ongoing.⁵ Plans are underway to present information on the performance of these lenses commencing with presentations at the Association for Research in Vision and Ophthalmology (ARVO) meeting to be held in Seattle, May 2024.