Prospective Study on Corneal Safety Evaluation of Children/Adolescents with Low and Moderate Myopia after Long-Term Orthokeratology

  Objective   To observe the possible changes in the integrity of the cornea and corneal endothelial cells of children/adolescents with low or moderate myopia after long-term wearing of orthokeratology (ortho-k) lenses, as well as the time when the relevant changes occur, so as to evaluate the safety of long-term wearing of ortho-k lens and to provide a reference for the safety evaluation of subjects wearing ortho-k lenses.

  Methods   Subjects were recruited in the Contact Lens Clinic, West China Hospital, Sichuan University for a three-year prospective study. Ortho-k of the same brand was matched for the subjects. The central corneal thickness (CCT), corneal endothelial cell density (ECD), and hexagonal cell ratio (HEX) were measured prior to the wearing of ortho-k lenses and after wearing ortho-k lenses for 1 month, 3 months, 6 months, and every 3 months until 36 months. The results of corneal fluorescence staining were recorded during each follow-up. When corneal staining was observed, the Efron grading standard was used for grading and corresponding treatment was given.

  Results   A total of 33 (66 eyes) myopic patients were included in the study. 15 cases (46.2%) reported having binocular foreign body sensations and tearing within the first week of wearing the lenses. After the subjects became adapted to wearing the lenses, the symptoms disappeared without intervention. During the follow-up period, 31 cases (93.94%) of binocular corneal staining were observed, of which, 24 cases (72.73%) were graded as G0, receiving no treatment, 5 cases (15.15%) were graded as GⅠ, and 2 cases (6.06%) were graded as GⅡ. Corresponding clinical treatment for corneal staining was given to the GⅠ and GⅡ subjects. This study found that the corneal ECD was inversely proportional to age (r=－0.380, P=0.002). During the three-year follow-up period, the subjects’ left eye ECD decreased from the baseline at 24 months and the right eye ECD decreased from the baseline at 27 months (P<0.05). The CCT results in the subjects showed that CCT became thinner at 1 month after wearing the lens (P<0.05), but the follow-up CCT showed a stable trend.

  Conclusion   After three years of long-term follow-up, no serious corneal complications occurred in children/adolescents with moderate and low myopia after long-term wearing of ortho-k lens. The corneal ECD of both eyes started decreasing 24 months after wearing the ortho-k lenses and the CCT decreased 1 month after wearing the lenses.