Advanced Surface Ablation In Keratoconus Suspect: A Case Report

Keratoconus (KC) is a bilateral, progressive, asymmetric, and degenerative ectatic disease of the cornea. Corneal refractive surgery, especially laser vision correction (LVC) with laser in situ keratomileusis (LASIK), in patients with such irregular corneas has long been contraindicated due to the risk of increasing postoperative progression of the disease. However, numerous long-term studies report the safety of surface ablation procedures in milder forms of
KC (which include subclinical and forme frustre KC), with photorefractive keratectomy (PRK) alone or even PRK followed by corneal collagen crosslinking. Current regimes for PRK in such cases use topography-guided ablation profiles intended to reduce corneal surface irregularities.

This case report outlines the 10-year clinical outcome of a patient initially misdiagnosed with KC and denied the opportunity for corneal LVC. Subsequently, the patient underwent advanced surface ablation in both eyes (OU). The corneal topographic, tomographic, and biomechanical properties of the patient have remained stable for the past decade.

In 2013, a 35-year-old male patient was denied corneal refractive surgery with LVC, due to an alleged KC topographic pattern in OU. He sought a second opinion and at our first observation, uncorrected distance visual acuity (UDVA) was 20/400 in the right eye (OD) and 20 /200 in the left eye (OS), while corrected distance visual acuity was 20/40 (-4.75) in OD and 20/20 (-2.50/-0.75 x 75 o ) in OS. There were no apparent subclinical or forme frustre keratoconus patterns in the topometric, tomographic, and biomechanical exams: (1) simulated keratometry results were 44.3 diopters (D) x 44.6 D @ 108.4 o in OD and 44.0 D x 44.7 D @ 100.5 o in OS; (2) thinnest pachymetry measurements were 546 µm OD and 534 µm OS; (3) maximum keratometry results were 44.9 D in OD and 45.2 D in OS. The Belin/Ambrósio enhanced ectasia index (BAD-D) was 1.20 OD and 2.18 OS. The Corvis biomechanical index (CBI) and the tomographic biomechanical index were: 0.00 and 0.45, respectively, for the OD; 0.00 and 0.16, respectively, for the OS. The patient was intolerant to glasses and contact lenses (CL) and he underwent customized topography-guided PRK in both eyes. Ten years after surgery, a stable flattening could still be observed in both eyes. On his last visit, the UDVA was 20/30 in the OD and 20/20 in the OS. The Biomechanical/Tomographic Assessment post-LVC from OD and OS demonstrated a post-LVC CBI of 0.00 in the OD and 0.00 in the OS, as well as a BAD-D score of 2.82 in the OD and 2.35 in the OS.

Surface ablation may be an option for selected cases of mild KC and cases with suspect or atypical topography. We advocate considering Tamayo et al.’s criteria for enhancing safety when planning custom ablations for such procedures, which can be an excellent surgical option in patients with CL intolerance and low tolerance to glasses. This case highlights the importance of performing multimodal eye imaging, to increase diagnostic accuracy and choose
the best individual treatment strategy. In this particular case, tomographic and biomechanical corneal evaluation were essential to our decision to perform a customized topography-guided PRK. This was a successful case of LVC as demonstrated by our 10-year follow-up.