Unilateral Corneal Ectasia After Bilateral Transepithelial Photorefractive Keratectomy

Abstract

We present the case of a 23-year-old male who experienced vision loss in his left eye 15 months after undergoing bilateral transepithelial photorefractive keratectomy (T-PRK). Despite the absence of any significant preoperative topographical risk factors in either eye, corneal ectasia was later confirmed in the left eye, while the right eye remained normal. Subtle asymmetry in topometric indices and a borderline high Index of vertical asymmetry (IVA) reading suggested the possibility of early subclinical keratoconus, potentially increasing the risk of post-refractive ectasia. The patient received corneal cross-linking (CXL) treatment in the affected eye to halt further progression, while the right eye remained under observation. This report reviews the rare instances of post-refractive ectasia. It highlights the potential role of subtle corneal irregularities in predisposing to ectasia, even without traditional risk factors.

Keywords: cornea; ectasia; laser refractive surgeries; myopia; trans prk.

Figure 1. Preoperative corneal tomography map

Preoperative corneal tomography for the right eye (above) and left eye (below): both eyes appear symmetrically normal and no risk factors for ectasia were seen bilaterally. OD: Oculus dexter, OS: Oculus sinister.

Figure 2. Belin/Ambrósio enhanced ectasia display preoperatively

No high-risk features were noted. OD: Oculus dexter, OS: Oculus sinister.

Figure 3. Postoperative corneal topography map

Postoperative corneal topography for the right eye (above) and left eye (below): signs of corneal ectasia noted in the left eye, including inferior focal steepening on axial curvature map, a marked increase in keratometry readings, high Inferior-Superior (I-S) Asymmetry Index and increased elevation of the posterior corneal surface. None of these signs were seen in the right eye. OD: Oculus dexter, OS: Oculus sinister.