Short-term Metamorphopsia Induced by Overnight Orthokeratology and Its Association to Changes in Optical Quality Measured with Double-pass Technique

Nova Southeastern University, Davie, Florida, USA

Objectives: To map the time course of changes in perceived distortion and optical quality during the first month following orthokeratology lens wearing, and to explore the association between those two. Background: Orthokeratology lens is an effective device to slow down the axial elongation in myopia development. However, some patients experience visual distortion after lens wear. Methods: A total of 43 subjects (20 boys and 23 girls) with age ranging from 8 to 12 years completed the study. All subjects were fitted with spherical four-zone orthokeratology lenses following the procedures recommended by the lens manufacturer. The subjects were required to wear the lens for at least eight consecutive hours at night. After lens removal during the daytime, orientation discrimination threshold was quantified with groups of briefly displayed short line segments in a two-alternative forced choice task by adaptive staircase paradigm. Objective scattering index (OSI) was evaluated using the double-pass technique (OQAS-II, Visiometrics). Measurements were scheduled prior to lens dispatch (baseline), followed by evaluations at 1day, 1 week, 2 weeks, and 1 month after the initial lens wearing. Results: At baseline, 1w, 2w, and 1 month after lens wearing, the mean ODT values were 3.99±1.33, 6.76±2.58 (p< 0.01), 6,65±2.66 (p< 0.01), 5.41±2.14 (p Conclusions: Both subjectively perceived metamorphopsia and objectively measured ocular scatter index significantly increased following the start of orthokeratology treatment. However, visual distortion peaked earlier and showed a quicker recovery than optical quality. This discrepancy may be contributed by a swift neural adaptation.