December 2, 2024
By Dwight Akerman, OD, MBA, FAAO, Dipl AAO, FBCLA, FIACLE
Photo Credit: Getty Images
Orthokeratology has gained popularity as a method for temporarily correcting myopia and reducing the progression of juvenile-onset myopia through specially designed gas-permeable contact lenses. These lenses are typically worn overnight to reshape the cornea, allowing for clear vision during the day without the need for corrective eyewear. While this treatment offers significant advantages, there are concerns regarding the risk of microbial keratitis.
The study conducted by Hiraoka et al. (2024) aims to shed light on the incidence of microbial keratitis among patients using overnight OrthoK lenses in Japan. This retrospective multicenter investigation involved four hospitals and 1,438 patients aged between 3 and 30, all of whom had been prescribed OrthoK lenses for at least three months. The researchers systematically gathered data from medical records, focusing on patient demographics, lens characteristics, lens care systems, and documented cases of microbial keratitis.
The primary purpose of the study was to evaluate the incidence of microbial keratitis in patients using OrthoK lenses, hypothesizing that the incidence would be relevant for understanding the safety of this treatment modality. The study gathered demographic data, including the gender and mean age of the patients, and examined the average duration for which these patients had been using OrthoK lenses. The methodology calculated the duration of lens wear based on the time from the initial fitting to the last clinical visit. By computing total person-years of lens use for all participants, the researchers aimed to obtain a robust estimate of the incidence of microbial keratitis.
Among the 1,438 patients, the cohort consisted of 753 males and 685 females, with a mean age of 12.7 years. Notably, the average duration of OrthoK lens wear was reported to be 5.2 years, with a mean lens power of -3.52D. Across the entire participant group, the cumulative duration of lens wear amounted to 7,415 person-years. From this extensive dataset, the researchers identified four cases of microbial keratitis. This resulted in an incidence rate of 5.4 cases per 10,000 patient-years, with a 95% confidence interval ranging from 1.0 to 9.8.
The findings underscore that the incidence of microbial keratitis among OrthoK lens wearers is comparable to, or potentially lower than, data from previous studies related to microbial keratitis in OrthoK and daily-wear soft contact lenses. This observation is particularly relevant, as it emphasizes that while overnight wear presents specific risks, the incidence of infection remains relatively controlled within the studied population.
The study by Hiraoka et al. represents the most extensive collective analysis to date investigating the correlation between overnight OrthoK and microbial keratitis. The findings contribute substantial evidence, advocating for the continued use of OrthoK lenses and supporting the safety profile of this treatment option. The researchers indicate that maintaining proper lens care systems is crucial in mitigating the risks of microbial keratitis. With appropriate hygiene practices, the safety of OrthoK lenses remains favorable, especially compared to traditional soft contact lenses. This research ultimately adds to the growing body of knowledge facilitating informed decision-making for those considering OrthoK as a viable option for vision correction or myopia management.
Abstract
Incidence of Microbial Keratitis Associated with Overnight Orthokeratology: A Multicenter Collaborative Study
Takahiro Hiraoka , Saiko Matsumura , Yuichi Hori , Kazutaka Kamiya , Kazunori Miyata , Tetsuro Oshika
Purpose: To investigate the incidence of microbial keratitis among Japanese patients wearing orthokeratology (orthoK) lenses
Study Design: Retrospective multicenter study
Method: This study was conducted at 4 hospitals in Japan and involved 1438 patients who had been prescribed orthoK lenses and had worn them for at least 3 months. Data on patient demographics, lens characteristics, lens care systems, and presence of microbial keratitis were extracted from the medical records. Duration of orthoK lens wear was calculated from the original fitting date to the patient’s last visit, with the total years of lens wear used as person-years of lens wear. The incidence of microbial keratitis was calculated by dividing the number of infected cases by the total person-years of lens wear for all enrolled participants.
Results: Among the 1438 patients, 753 were male and 685 were female, with a mean age of 12.7 ± 5.4 years. The mean duration of orthoK lens wear was 5.2 ± 4.5 years, and the mean lens power was -3.52 ± 1.41 D. The total person-years of lens wear for all enrolled patients was 7415. Four cases of microbial keratitis were identified, resulting in an overall incidence of microbial keratitis of 5.4 (95% CI: 1.0-9.8) per 10,000 patient-years among orthoK lens wearers.
Conclusion: This study represents the largest sample size to date for estimating the incidence of microbial keratitis associated with orthoK lenses. The incidence was similar to or slightly lower than that of previous studies on orthoK-related microbial keratitis and also comparable to that of daily wear soft contact lenses.
Hiraoka, T., Matsumura, S., Hori, Y., Kamiya, K., Miyata, K., & Oshika, T. (2024). Incidence of microbial keratitis associated with overnight orthokeratology: a multicenter collaborative study. Japanese journal of ophthalmology. Advance online publication.
DOI: https://doi.org/10.1007/s10384-024-01137-4
