Testing spectacle lenses for myopia control in relation to changes in axial length

Dr Eva Chamorro points out that myopia control spectacle lenses affect the diurnal rhythms in the AL in young adult human and produced a small short-term increase in the AL that varies in intensity and time interval for each of the 3 studied lenses.

A team of Spanish investigators, led by Dr Eva Chamorro, director of clinical research, and colleagues from Indizen Optical Technologies SL, Madrid, are studying the effects of different spectacle lenses that add different levels of defocus to the peripheral retina to control myopia.

In a poster presented at the Association for Research in Vision and Ophthalmology’s 2022 annual meeting in Denver, Colorado, United States, the investigators noted that the axial length (AL) changes over the course of a day (diurnal rhythms) with imposed defocus. This suggested, they pointed out, that these short-term changes in the AL might predict the efficacy of treatments to control myopia.

With this in mind, they conducted a pilot study to evaluate the effects of different types of myopia control spectacle lenses on the diurnal AL changes in young adults who were either emmetropic or wore contact lenses. The Als were measured in 6 subjects who wore glasses with a myopia control lens that had a plano central region and imposed peripheral defocus over the dominant eye; the fellow non-dominant eye had a plano control lens.

Three different myopia control lenses were used to induce the defocus, specifically, the Miyosmart (Hoya, Kuala Lumpur, Malaysia); Stellest (Essilor, Kuala Lumpur), and a non-commercial prototype (IOT, Madrid). All measurements of the AL were obtained at baseline without the lenses and then performed over 4 consecutive days with the lenses. After the measurements were completed, the investigators analysed the differences both between the control and study eyes with each type of myopia control lens and the differences between baseline and the treatment days in the treated eyes, they described.

Analysis results

The investigators observed a significant increase in the AL between the control and treatment eyes with the Stellest and the noncommercial prototype lenses after 2 hours in the treated eyes. With the Miyosmart lens, they observed non-significant differences between the eyes at all times during the lens use.

The comparison of the AL changes in the treatment eye between baseline and the treatment day showed significant differences with the 3 myopia control lenses, which indicated that the use of all 3 resulted in increases in the AL. Minimal daily changes in the AL, they reported, were seen at baseline that day, with variations of less than 0.01 mm across all time intervals.

“Myopia control spectacle lenses affect the diurnal rhythms in the AL in young adult human and produced a small short-term increase in the AL that varies in intensity and time interval for each of the 3 studied lenses,” Dr Chamorro concluded. “Additional studies with a larger sample size and longer follow-up periods are necessary to confirm that short-term variations of diurnal rhythms can be used as predictor of myopia control efficacy.”