Validity of axial length measurements for monitoring myopic progression in orthokeratology.
OBJECTIVE
To investigate the short-term effect of orthokeratology (ortho-k) lens wear on the anterior segment length for validating the use of axial length for monitoring myopic progression after ortho-k treatment.


METHODS
THIRTY-SEVEN AND 39 SUBJECTS (AGES: 7-10 years) were randomly assigned to wear ortho-k and single-vision spectacles, respectively. Central corneal thickness (CCT), anterior chamber depth (ACD), crystalline lens thickness (LT), and anterior segment length (ASL: summation of CCT, ACD, and LT) were measured before and 6 months after the treatment under cycloplegia. Changes in these parameters were evaluated and compared between the two groups of subjects.


RESULTS
There were no significant between-group differences in the baseline data (P > 0.37). After 6 months of lens wear, in the ortho-k group, CCT was significantly reduced by 0.009 ± 0.009 mm (P < 0.001), whereas ACD and LT remained unchanged (P > 0.15). In the spectacle group, ACD was significantly increased by 0.01 ± 0.03 mm (P = 0.008), whereas CCT and LT remained unchanged (P > 0.06). In both groups of subjects, ASL did not appreciably change but axial length was significantly increased by 0.10 ± 0.10 mm and 0.20 ± 0.11 mm in the ortho-k and the spectacle groups, respectively (P < 0.001).


CONCLUSIONS
Eyeball elongation occurred in children wearing both ortho-k and single-vision spectacles. Since ASL was not affected by ortho-k treatment, axial length measured reflects the true growth of the eyeball and is a valid parameter for monitoring myopic progression in ortho-k treated eyes.
School of Optometry, HJ502, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China. sopeggy@polyu.edu.hk
Sin-Wan
SW
Cheung
Pauline
P
Cho
D000867:Anterior Chamber / Q000473:pathology; D000869:Anterior Eye Segment / Q000473:pathology; D002648:Child; D003261:Contact Lenses; D003315:Cornea / Q000473:pathology; D018450:Disease Progression; D005139:Eyeglasses; D005260:Female; D006801:Humans; D007908:Lens, Crystalline / Q000473:pathology; D008297:Male; D009216:Myopia / Q000628:therapy*; D054158:Orthokeratologic Procedures