Postoperative mapping benefits
Post-operatively, corneal epithelial changes are known to play a role in refractive regression. This refractive effect should be considered when planning surgery, since it may help to increase the accuracy of the surgery results.
Corneal epithelium contributes to the refractive power of the cornea, and thus to total ocular refraction. The refractive power of the epithelium alone ranges from 0.55–1.85 D at the central 2.0-mm diameter zone and 0.29–1.60 D at the 3.6-mm diameter zone.3
Therefore, it is helpful to differentiate between regression due to epithelial hypertrophy and early corneal ectasia, where it thins over areas of relative increases in corneal curvature and thickens over areas of relative flattening in corneal curvature. Determining these findings could entirely change the management of a patient presenting with residual power for solution.
In the case of regression, enhancement is possible provided that adequate tissue is available. If the patient is an ectasia suspect, one would either only do crosslinking of the cornea or perform topography-guided PRK with a crosslinking procedure.