Advanced Surface Ablation in a Patient With Suspect Topography: A Case Report

Abstract

The purpose of this clinical report is to describe a 10-year clinical outcome of advanced surface ablation with photorefractive keratectomy (PRK) in a patient who had been previously incorrectly diagnosed with keratoconus (KC). Corneal ectasia is a rare but extremely relevant complication of laser vision correction, and KC represents a major contraindication for these procedures. Nonetheless, some surface ablation procedures, such as PRK, might be a valid option for particular patients with atypical corneal topography or subclinical or mild forms of KC. Patient education and complete preoperative refractive multimodal imaging are essential for a more conscious therapeutic decision, minimizing iatrogenic ectasia, as well as decreasing the number of patients who are incorrectly denied refractive surgery, as was the patient presented in this study.

Keywords: corneal ectasia; keratoconus; keratoconus suspect; photorefractive keratectomy; surface ablation.

Figure 1. Pentacam anterior axial/sagittal curvature color maps with different scales.

In (a), the Ambrósio 2 scale is displayed; in (b), the Klyce scale is displayed; in (c), the Belin scale is displayed (with a 0.25 D increment and 15-color relative scale); in (d), the Holladay scale is displayed, also with a 0.25 D increment and 15-color relative scale. There is no clear evidence of anterior axial/sagittal curvature abnormalities with the appropriate scales, though scales displayed in (c) and (d) can be misleading and result in a misdiagnosis of mild keratoconus, if not carefully interpreted.

Figure 2. Pentacam and Corvis biomechanical/tomographic assessment (Ambrósio, Roberts & Vinciguerra (ARV)) and pre-laser vision correction assessment of the patient’s right eye (OD) and left eye (OS).

The Corvis biomechanical index (CBI) and the tomographic biomechanical index (TBI) were 0.00 and 0.45 units, respectively, for the OD (a), and 0.00 and 0.6 units, respectively, for the OS (b) (indexes calculated from the data from 2013). There is no clear evidence of mild keratoconus (KC) or an ectatic disease. The Belin/Ambrósio enhanced ectasia index (BAD-D) is also depicted for both eyes, with a borderline value, but also without any clear evidence of an ectatic disease.

Figure 3. Pentacam tomographic comparison of the corneal anterior curvature pre and post-laser vision correction of the patient’s right (OD) and left (OS) eyes.

(a and c): Anterior curvature maps of OD in 2013 and 2023, respectively. (b and d): Anterior curvature maps of OS in 2013 and 2023, respectively. The two panels on the right represent the difference in anterior corneal curvature between both exams, for each eye. (e and f): Note there is no evidence of the development or progression of an ectatic disease in both eyes (C–A; D–B).

Figure 4. Pentacam tomographic comparison of the corneal posterior elevation pre and post-laser vision correction of the patient’s right (OD) and left (OS) eyes.

(a and c): Posterior elevation maps of OD in 2013 and 2023, respectively. (b and d): Posterior elevation maps of OS in 2013 and 2023, respectively. The two panels on the right represent the difference in posterior elevation between both exams for each eye. (e and f): Note there is no evidence of the development or progression of an ectatic disease in both eyes (C–A; D–B).

Figure 5. Pentacam tomographic comparison of the corneal thickness pre and post-laser vision correction of the patient’s right (OD) and left (OS) eyes.

(a and c): Thickness maps of OD in 2013 and 2023, respectively. (b and d): Thickness maps of OS in 2013 and 2023, respectively. The two panels on the right represent the difference in corneal thickness between both exams, for each eye. (e and f): Note there is no evidence of the development or progression of an ectatic disease in both eyes (C–A; D–B).