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PTEK (phototherapeutic epithelial-guided keratectomy): a novel trans-epithelial OCT-guided PTK protocol combined with corneal collagen cross-linking for the reduction of irregular astigmatism in patients with keratoconus

Poster Details

First Author: A. Davidson UK

Co Author(s):    E. Trocme   A. Barsam                 

Abstract Details


Keratoconus is a progressive ectatic corneal dystrophy, which in severe cases requires a lamellar or penetrating keratoplasty. Corneal collagen crosslinking (CXL) is a viable therapeutic modality that prevents or delays the need for keratoplasty. We propose a new protocol for phototherapeutic epithelial guided keratectomy (PTEK) which utilises epithelial thickness measurements to customise treatment and safely optimise post-CXL refractive results in patients with keratoconus.


Ophthalmic private practice, London UK.


Inclusion criteria: progressive keratoconus, contact lens intolerance and a minimum corneal thickness of 400µm. Epithelial thickness (ET) was measured by optical coherence tomography and trans-epithelial PTK was carried out. To minimize tissue loss, a maximum limit of ablation was set to 20µm more than the thinnest portion of epithelium. The ablation zone was 8.9mm with an optical zone of 7.0mm in all cases. Immediate simultaneous CXL was then performed according to the Dresden protocol using riboflavin solution (0.1% riboflavin-5-phosphate, 20% dextran T-500) after de-epithelialization with PTEK. The patients received follow-up at 1-week, 1-month, 3-months, 6-months and 1-year post-op.


7 eyes (N=7) of 6 patients were included. No intra or post-operative complications were observed at the latest follow up. At the 6-month follow-up, unaided visual acuity (UVA) improved by an average of 2 lines (logMAR), topography remained stable and all Kmax readings improved, averaging 3.5 diopters of improvement across the case series. Mean cylindrical refraction improved by 2 diopters post-op, and spherical equivalent improved by 1.5 diopters at 6 months. Minimum corneal thickness decreased by less than 30µm postoperatively.


PTEK is a new protocol for transepithelial PTK, which is customized to the patients’ ET. Epithelial thickness is higher in the periphery relative to the apex of the cornea in ectatic disorders. Adjusting transepithelial ablation depth to the thicker end of the corneal epithelium therefore allows for customized smoothing of the corneal apex, limiting stromal loss. This case series shows a reduction of Kmax and improvement in unaided visual acuity. Combined PTEK with CXL represents a safe therapeutic alternative for patients with keratoconus, which prevents or slows disease progression and decreases the dependency on contact lenses or glasses.

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