The risks and benefits of myopia control – Q&A with Professor Mark Bullimore

As an internationally renowned myopia scientist and educator, Professor Mark Bullimore often leads conversations about the latest innovations in myopia management. We speak to him about his paper 'The risks and benefits of myopia control',¹ where he clearly outlines that the benefits outweigh the risks with myopia control.

Prof. Bullimore: The timing was right: we're acutely aware of the increasing and increased prevalence of myopia around the world. Because of this, a number of professional bodies have been paying attention to myopia control and its importance. We're very familiar with the risk, but I think it's equally important to talk about the benefits and to quantify it. I brought together some of my friends and colleagues who were in agreement, and their expertise in ophthalmology, epidemiology, visual impairment, and myopia really enhanced the quality of the paper.

Prof. Bullimore: In the paper, we found that spectacles and atropine are seen as the lowest risk options, with spectacles being well-established as safe and atropine is applied topically in very low concentrations. Contact lenses, particularly overnight orthokeratology lenses, being prescribed to children can cause concern among ophthalmologists due to the risk of microbial keratitis (MK). Daily disposable soft contact lenses like MiSight 1 day are considered the safest modality, with a low incidence of about one MK per 10,000 patient years. The risk is higher with overnight orthokeratology, but there are limited studies on the incidence so our paper reports a range of values from the literature.¹

Prof. Bullimore: Well, it's because the risk is so very small. Patient years is used to describe the incidence rate of rare events, such as MK in contact lens wearers, as it provides a more easily interpreted representation of the risk. This measure considers both the number of patients and the duration of their exposure to the risk factor, which is usually expressed in years. Using percentages to describe such risks could be misleading or difficult to contextualize.²

Prof. Bullimore: It took a while to figure out how to compare the incidence of microbial keratitis with the visual impairment associated with myopia. We knew the incidence rate. So we said, let's say a child is wearing soft contact lenses for five years. We also had to consider the percentage of microbial keratitis cases that lead to vision loss, which we estimated to be around 15%,^3-4 but other papers suggest it's lower. The next important thing is, well, the patient is going to live another 70 years and have to live with whatever the impairment is. So, we've got one case of MK per 10,000, 5 cases per 10,000 for five years of wear, but only 15% of cases result in vision loss. Using those numbers, we can estimate that for 10,000 children wearing soft contact lenses for five years, that is going to result in about 50 years of visual impairment, total. 50 years across those 10,000 children. So, putting that into context, 10,000 patients undergoing 1 diopter of myopia control saves you 10,000 years of visual impairment, whereas the contact lens complications would increase visual impairment by 50 years, so you've got 50 years of loss, 10,000 years of gain. The ratio is 200 to 1. And the needle is firmly in the direction of benefit of myopia control compared to risk of contact lens wear.

Prof. Bullimore: Firstly, remember that the risk is extremely low. Again, when we express incidence of microbial keratitis, we don't talk about percentages. We talk about one or two cases per 10,000 years. In fact, it's unlikely that most eye care professionals will ever encounter a case of microbial keratitis, especially a severe one that could result in vision loss. Our Each Diopter Matters paper highlights several reasons for slowing down myopia progression. Slowing down myopia can result in improved vision both with and without glasses and make someone a better candidate for LASIK or other refractive procedures. The most significant benefit is the long-term gain in reducing the risk of myopic maculopathy and other sight-threatening conditions that increase the risk of visual impairment associated with high myopia.⁵