Visual Rehabilitation for Keratoconus

Long-term follow-up of patients with keratoconus treated with combined corneal cross-linking (CXL) and excimer laser surface ablation is causing Paolo Vinciguerra MD to raise a red flag and caution colleagues and patients about the potential for massive corneal flattening as a late-onset occurrence.

“This is a new finding, and it indicates surgeons should be aware that combining CXL and refractive surgery can be very dangerous,” Dr Vinciguerra said. “Therefore, they should be prepared to expect a surprise many years after patients undergo a combination procedure with CXL to stabilise disease progression and excimer laser surface ablation for visual rehabilitation, and they may need to warn patients that the long-term outcome is unpredictable.”

Having been an investigator in the clinical trial conducted to gain regulatory approval of CXL for keratoconus, Dr Vinciguerra has accrued a group of patients he has been following for almost two decades. This cohort now includes more than 20 patients whose keratometry remained stable for 10 to 14 years, but then manifested significant central flattening of 5.0 to 6.0 D and peripheral steepening resulting in hyperopic refraction.

Imaging of these eyes showed stability of epithelial thickness and corneal pachymetry. However, changes in anterior and posterior corneal elevation maps were documented along with shallowing of the anterior chamber depth. In addition, the CXL demarcation line was very deep centrally and became progressively more superficial, extending out to the periphery.

Dr Vinciguerra proposed minimising/avoiding tissue ablation might offer a solution for avoiding late-onset flattening. With that idea in mind, he expressed an interest in Phototherapeutic keratectomy-Assisted Customised Epi-on corneal cross-linking (PACE-CXL), introduced by Farhad Hafezi MD, PhD and colleagues at the ELZA Institute in Zurich, Switzerland.

“PACE-CXL involves only a localised epithelial ablation followed by a proprietary irradiation protocol specifically designed to improve corneal shape. Although it is a promising technique, longer follow-up is needed to establish its efficacy and safety compared to other approaches,” Dr Vinciguerra said.

“The deeper question is whether we fully understand the long-term remodelling dynamics of cross-linked corneas and how different techniques (e.g., epi-on vs. epi-off) and energy delivery methods interact with the corneal biomechanics. Until we have more data, it would be prudent to individualise treatment plans, focusing on minimal tissue ablation when excimer laser ablation is needed and leaning toward approaches like PACE-CXL when corneal stability is the priority.”

To rehabilitate vision in eyes with keratoconus, Dr Vinciguerra now performs a customised ablation based on the total corneal wavefront that targets the most visually significant aberration in keratoconic eyes while minimising tissue ablation. It uses Schwind’s ORK-CAM planning software and links the total wavefront map obtained with the company’s combined topographer/aberrometer (Peramis) to the Amaris excimer laser. The system discriminates between coma and astigmatism and prioritises correction of coma that impacts visual acuity by >0.5 D, regardless of sphere and cylinder.

“Coma is the most important HOA in eyes with keratoconus, but it should not be fully corrected on the anterior surface, considering there will be compensation from posterior surface coma,” Dr Vinciguerra explained. “Because this custom ablation treats only the most vision-impairing aberrations, it is very shallow and tissue-saving and therefore maintains corneal stability.”

Dr Vinciguerra spoke at the 2024 ESCRS Congress in Barcelona.

Paolo Vinciguerra MD is Professor and Head of the Ophthalmology Unit, Humanitas Research Hospital, Milan, Italy. paolovinciguerra@me.com