How common is microbial keratitis in children wearing orthokeratology?

Paper title: Pediatric Microbial Keratitis With Overnight Orthokeratology in Russia

Authors: Mark Bullimore, Dmitry Mirsayafov, Aslan Khurai, Leonid Kononov, Suzanna Asatrian, Andrei Shmakov, Kathryn Richdale, Valery Gorev

Date: 2021

Reference: Bullimore M, Mirsayafov D, Khurai A, et al. Pediatric Microbial Keratitis With Overnight Orthokeratology in Russia. Eye & Contact Lens. 2021;47(7):420-425.[link]

This study estimated the incidence of microbial keratitis (MK) in children wearing overnight orthokeratology lenses in a group practice in Russia. The study observed a rate of MK of approximately 5 cases per 10,000 patient years, which is lower than previous reports from clinical data gathered over a decade ago, and similar to that associated with daily-wear soft contact lenses. The previous reported rate of MK was around 14 per 10,000 patient years,¹ utilizing data gathered from a survey of almost 200 eye care practitioners in the United States, with the clinical care occurring between 2004 and 2006. In this new study, data was gathered from a single, large group of eye care practices, with OK fits occurring between 2010 and 2018 and outcomes surveyed from 2018. The improved safety profile in this recent study likely reflects the effect of gathering data from a single group of practices with standardized training, whereas the previous study obtained data from numerous different practices. It could also reflect a concerted effort to improve OK safety and compliance in the past decade or so. 

This should give both practitioners and parents confidence in considering overnight orthokeratology as a means of myopia control. The mean age of MK was 15.2±1.1 versus the mean age of fitting 12 years, indicating children are more likely to experience MK years after being fitted, rather than in the first few months. This highlights the importance of remaining vigilant in educating patients on good hygiene and lens care for the duration of their treatment period. The finding of a higher safety profile compared to previous reports could be due to the data being gathered from a single group of practices with standardized training and care protocols, and/or reflecting a concerted effort to improve OK safety and compliance in the past decade or so.

OK is perhaps safer than originally indicated, at least in the setting of an experienced group practice. The risk of MK appears similar to rates associated with use of daily wear soft contact lenses, which should give eye care practitioners and parents confidence in fitting OK to children.

The variation in outcomes over time, and with data coming from different countries, this indicates that we have more to learn about the safety profile of orthokeratology in different geographic and ethnic populations.

Title: Pediatric Microbial Keratitis With Overnight Orthokeratology in Russia

Authors: Mark Bullimore, Dmitry Mirsayafov, Aslan Khurai, Leonid Kononov, Suzanna Asatrian, Andrei Shmakov, Kathryn Richdale, Valery Gorev

Purpose: To estimate the incidence of microbial keratitis in children wearing overnight orthokeratology lenses in Moscow, Russia.

Methods: To estimate the number of children wearing overnight orthokeratology lenses in 2018, 1,368 patient records from 13 Doctors Lens clinics were selected at random and extrapolated to the entire patient base. To identify cases of microbial keratitis, all episodes of infiltrative keratitis from Morozovskaya City Children's Clinical Hospital in 2018 were recorded and adjudicated by three experienced ophthalmologists. Incidence was calculated as the number of cases divided by the estimated number of wearers.

Results: There were 23,049 overnight orthokeratology fits between 2010 and 2018. Among the 1,368 records surveyed, 1,078 (79%) were younger than 18 years at initial fitting. Based on a 7% or 10% annual discontinuation rate, the estimated number of children wearing lenses in 2018 was 10,307 or 9,422, respectively. During 2018, there were 139 cases of corneal infiltrative keratitis in children and 45 were adjudicated as microbial keratitis (32%). Of these, 20 cases were associated with contact lens wear (44%): 15 soft lens wearers (33%) and 5 overnight orthokeratology wearers (11%). Based on the 5 cases and assuming a 7% or 10% discontinuation rate, the annual incidence is 4.9 (95% confidence interval[CI]: 2.1-11.4) or 5.3 (95% CI: 2.3-12.4) per 10,000 patient years.

Conclusions: The incidence of microbial keratitis in children wearing overnight orthokeratology is lower than a previous United States study and similar to rates associated with use of daily wear soft contact lenses.