title: Topographical mapping and in-office modification in the management of an orthokeratology patient.
abstract: A 20-year-old female was fitted with rigid gas permeable (RGP) orthokeratology (ortho-k) lenses for overnight wear. Both lenses decentred nasally due to the tight fit of the alignment zone (AZ) and the peripheral zone (PZ). The AZ and PZ of both lenses were flattened using an in-office modification unit. Centration of the right lens improved but a small central island was also observed. The left lens still decentred nasally. Both findings indicated that the AZ and PZ of the right lens were too steep leading to 'lens vaulting' or excessive central clearance and inadequate tear exchange, respectively. The AZ and PZ of both lenses were flattened further using the modification unit and after the adjustment, both lenses centred well and the central island in the right eye was eliminated. This case demonstrates the usefulness of topographical corneal mapping and in-office modification of lenses in the management of ortho-k patients.
authors.affiliation: Centre for Myopia Research, Department of Optometry & Radiography, The Hong Kong Polytechnic University, HKSAR, China. orvchui@polyu.edu.hk
authors.forename: W S
authors.initials: WS
authors.lastname: Chui
authors.forename: P
authors.initials: P
authors.lastname: Cho
authors.forename: D
authors.initials: D
authors.lastname: Fan