Topographic Guided Custom Ablation Phototherapeutic Keratectomy With Central Corneal Regularization In Keratoconus

Advances in the ability to halt progression in keratoconus has led to a shift in the paradigm of treatment. With the success of Collagen Cross Linking (CXL) the goal of treatment has transitioned from preservation to maximization of vision. Topography guided custom ablation demonstrates an advantage in the management of corneal irregularity. The efficacy and stability following CXL has allowed us to reconsider the application of this technology in keratoconus. The innovative Central Corneal Regularization (CCR) modality of custom ablation, delivered by the iVis Suite, provides a further theoretical advantage. This treatment promises efficacious reduction in irregularity, while providing maximal preservation of tissue.

A retrospective case review of all patients undergoing CCR with a preoperative diagnosis of keratoconus was undertaken. Patients attended a single Ophthalmology practice, with two specialist refractive surgeons in Adelaide, Australia from November 2015 to March 2023. Data was collected on 16 eyes, from 12 patients. All patients completed 3-month follow-up, 8 eyes completed 6-month follow-up.

Preoperative unaided visual acuity (UAVA) and best spectacle corrected visual acuity (BSCVA) were collected on all patients. An up to date subjective refraction, preoperative keratometry, pachymetry and topography were also obtained. The topographic guided custom ablation treatment in the form of CCR was provided by the dedicated iVis Excimer laser Suite programme using a transepithelial method. The iVis modality treats the central 1-1.5mm. Preoperative measures were then compared to post-operative BSCVA at 3 and 6 months. Repeat subjective refraction, keratometry, pachymetry and topography were undertaken at each postoperative visit.

At 3 months there was an improvement in BSCVA by 1.15 lines of logMAR visual acuity. The improvement appeared to be maintained at 6 months with a suggested improvement to 1.62 lines.

Topographic guided custom ablation delivered with the novel CCR modality resulted in an improvement in BSCVA. This has been demonstrated previously when the procedure was combined with simultaneous CXL. In our cohort the treatment was provided as a stand-alone procedure, either following previous CXL or proven corneal stability. Therefore, the outcomes presented can be directly attributed to the CCR procedure. Further information regarding the longevity of outcomes is still required. However, the customized regularization demonstrates promising results in improving spectacle corrected vision, in turn providing keratoconic patients with improved visual quality and a greater range of options for their refractive correction.