Article Text

Download PDFPDF

P-16 Predicting ablation spherical equivalent of prior LASIK treatment from corneal pachymetry map
  1. Arthur Hammer1,
  2. Tjebo FC Heeren1,
  3. Romesh Angunawela1,2,
  4. Kamran Saha1
  1. 1Moorfields Eye Hospital, London, UK
  2. 2OCL Vision, London, UK


*Correspondence – Arthur Hammer:

Purpose To provide a metric to differentiate between hyperopic and myopic ablation of a prior LASIK treatment based on the corneal pachymetry profile after laser vision correction.

Methods Pachymetry data were recovered retrospectively from patients who had previous LASIK for refractive purposes between 2019 and 2020. Patients with any corneal disorder were excluded. Ablation spherical equivalent was predicted from central to semi-peripheral corneal thickness (CPT) ratio, both for values provided by Pentacam, and values computed from extracted raw pachymetry data.

Results Data were analysed for 140 eyes of 73 patients (42% female, mean age 40.9, SD 12.8). CPT-ratio cut-off for distinction between myopic and hyperopic LASIK was 0.86 for pentacam-provided values. Sensitivity and specificity were 0.7 and 0.95, respectively. Accuracy increased with computation of CPT ratio based on extracted raw data. Sensitivity and specificity were 0.87 and 0.99, respectively. There was a marked linear correlation between CPT-ratio and ablation spherical equivalent (R2=0.93).

Conclusions CPT ratio cut-offs can correctly classify hyperopic versus myopic spherical equivalent of previous LASIK ablation. This could prove useful for increased accuracy of intraocular lens (IOL) calculations for patients with no historical data of their prior LASIK surgery at the time of cataract surgery planning.

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: .

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.