ESCRS - P030 - PREDICTING SPHERICAL EQUIVALENT OF PRIOR LASIK ABLATION FROM CORNEAL PACHYMETRY

PREDICTING SPHERICAL EQUIVALENT OF PRIOR LASIK ABLATION FROM CORNEAL PACHYMETRY

Published 2022 - 26th ESCRS Winter Meeting

Reference: P030 | Type: Abstracts | DOI: 10.82333/rcfj-hs93

Authors: Arthur Hammer* 1 , Tjebo Heeren 2 , Romesh Angunawela 3 , Kamran Saha 2

1Cornea and external diseases service,Moorfields eye hospital NHS foundation trust,London,United Kingdom, 2Cataract service,Moorfields eye hospital NHS foundation trust,London,United Kingdom, 3Cornea and external diseases,Ophthalmic consultants of London (OCL)-Vision,London,United Kingdom

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.

Setting

Private Practice (OCL-Vision)

Methods

Pachymetry data was recovered 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 was 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 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). 

Conclusion

CPT ratio cut-offs can correctly classify hyperopic versus myopic spherical equivalent of previous LASIK ablation. In addition, CPT ratio can be used to predict the height of ablation spherical equivalent. 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.