Orthokeratology in Moderate Myopia: A Study of Predictability and Safety

Abstract

Purpose: Literature is relatively silent on safety profile and predictability of orthokeratology lenses in terms of myopia correction and prevention of further progression, especially in semi-tropical countries; this study was designed to fill this gap.
 Methods: This prospective, intervention case series enrolled 30 eyes of 30 patients with myopia up to –5.5 diopters (D). Patients were randomized into two groups of 15 each; the study group was prescribed overnight orthokeratology (OK) lenses, while the control group used daily wear conventional soft contact lenses. Follow-up examinations were performed after 1 h and 6 h, and then at 1, 7, 15, 30 days, and 4 months post lens wear. Uncorrected visual acuity (UCVA), contrast sensitivity, keratometry, central corneal thickness (CCT), and tear film break up time (TBUT) were evaluated at each follow-up examination.
 Results: All patients attained a visual acuity of 0.00 Logarithm of the Minimum Angle of Resolution (logMAR) after one week of lens use, which was maintained throughout the study period. While patients allotted to the study group had a gain of 8.1 Snellen lines (UCVA), those in the control group gained 8.9 lines (BCVA) at the end of follow-up period. In the OK group, cornea showed a flattening of 0.8 D (mean keratometry) after single overnight usage of OK lens and overall flattening of 1.2 D compared to baseline, at the end of four months. The change in contrast sensitivity, corneal endothelial specular count, axial length and tear film status was not significant in either group.
 Conclusion: Orthokeratology is an effective and safe modality to correct moderate myopia in motivated young adults. No side effects were encountered after a short-term follow-up in participants who resided in semi-tropical environments.

The Biomechanical Response of the Cornea in Orthokeratology

“…As the refractive target increased, both the central and peripheral corneal stress responses increased significantly, especially in the corneal center. Although the FDA or other health authorities approve the use of ortho-k treatment in myopia up to −6.00 D in some lens designs, the safest and most successful outcome will be achieved for those patients with lower baseline levels of myopia ( Mika et al, 2007 ; Liu and Xie, 2016 ; Singh et al, 2020 ; Hu et al, 2021 ). Therefore, for patients with high myopia or for doctors who used to increase the target degrees, more attention must be paid to the possible side effects of the ortho-k lens wear, such as damage to the integrity of the cornea, since those lenses are designed with increased compressive pressure.…”

Efficacy, predictability and safety of long-term orthokeratology: An 18-year follow-up study

“…Interestingly, complications in children were not only less frequent, but also less severe than in adults, even accounting for the higher baseline SE in children. It has been suggested that children may benefit from parental oversight with regards to contact lens care and maintenance, and may be more motivated than adults for this particularly demanding modality of lens wear [10,12]. In addition, better tear film integrity and corneal endothelium response in children may also help to explain these findings.…”

“…Research on the efficacy and predictability of ortho-k is commonly conducted within a relatively short time frame, given that refraction stability is reached between seven and 30 days, depending on target refraction and age of patients, with younger patients showing a more rapid corneal response [8][9][10][11][12]. Conversely, studies on the safety of orthokeratology have focussed mainly on children using their lenses for myopia control, describing their findings in terms of incidence, with limited information on the predominant moment of occurrence of each type of adverse effect within the course of the ortho-k treatment.…”

Predicting factors for progression of the myopia in the MiSight assessment study Spain (MASS)

“…There is also strong evidence that myopia progression can be significantly reduced by a range of interventions, the most effective being the use of atropine, 14 , 15 , 16 , 17 , 18 , 19 followed by orthokeratology (OK) 20 , 21 , 22 , 23 and peripheral defocus modifying CLs. 24 , 25 , 26 , 27 , 28 , 29 , 30 Despite the good results reported for these treatments, not all study participants responded in the same way.…”