Anterior Segment Changes Produced in Response to Long-Term Overnight Orthokeratology

Purpose: To evaluate the effect of overnight orthokeratology (OK) on anterior chamber depth (ACD), posterior radius of corneal curvature (PRCC) and axial length (AL) over one year. Methods: In this prospective longitudinal study, measurements were made in 34 right eyes of 34 subjects at baseline, 15 days, 1 and 12 months after starting OK treatment. ACD and PRCC measurements were obtained using a Pentacam system and AL was measured using an IOL-Master. ACD and PRCC were measured along the horizontal and vertical meridians at 1 mm intervals. These measurements were expressed as the distance from the center in the nasal (N), temporal (T), superior (S) and inferior (I) directions. Results: A significant reduction in ACD was observed in both meridians during treatment. PRCC flattened significantly in the (T) direction after 15 d (1mm, p<0.05), at the corneal center after 15 d (p<0.01), in the (T) direction after 1 month (1 mm, p<0.05), in the (S) direction after 12 months (1mm p<0.05), in the (N) direction after 12 months (1mm p<0.05), in the (N) and (T) directions after 12 months (3 mm, p<0.05) and in the (T) direction after 12 months (4 mm p<0.05), at the corneal center after 12 months (p<0.01). AL was significantly reduced during treatment (p<0.05). Conclusions: A long period of OK reduces ACD and AL and changes PRCC.