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 post-LASIK ectasia: a case series

Session Details

Session Title: Presented Poster Session: Cross-Linking

Session Date/Time: Sunday 06/09/2015 | 15:00-16:30

Paper Time: 16:00

Venue: Poster Village: Pod 4

First Author: : A. Davidson UK

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

Abstract Details

Purpose:

Post-LASIK ectasia is a severe progressive biomechanical complication of refractive surgery, which in severe cases requires lamellar or penetrating keratoplasty. Corneal collagen crosslinking (CXL) is shown to be a viable therapeutic modality that prevents or delays the need for keratoplasty. We propose a new protocol for phototherapeutic epithelial guided keratectomy (PTEK) which utilizes epithelial thickness measurements to customise treatment and safely optimise post CXL refractive results in patients with post-LASIK ectasia.

Setting:

Ophthalmic private practice, London, UK.

Methods:

Case Series of 2 eyes of 2 patients (N=2), In phototherapeutic epithelial-guided keratectomy (PTEK), ablation depth is set to maximum measured epithelial thickness (ET) but limited to 20µm more than the thinnest portion of epithelium in order to minimise tissue loss. Measurements were performed within a 6mm zone using optical coherence tomography. PTEK with an ablation zone of 8.9mm, an optical zone of 7mm and a 60µm ablation depth was performed. Simultaneous CXL was performed according to the Dresden protocol after de-epithelialization with PTEK. The patients were followed up at 1, 2, 5, and 31 weeks post-op.

Results:

Results expressed as means (N=2). Mean pre-op unaided visual acuity (UVA), spherical equivalent, magnitude of cylinder, Kmax and minimum corneal thickness were 6/48 (snellen chart), -1.25D, -3.5D, 63.8D and 439µm respectively. At one week post-op there was good re-epithelialization with mild punctate epithelial erosions in both cases. At 2 weeks post-op the corneal examination revealed healed corneal epithelium in both cases and a mean spherical equivalent and magnitude of cylinder of -1.4D and -0.5D respectively. At 31 weeks post-op, topography showed a mean minimum corneal thickness, UVA and reduction of Kmax of 409µm, 6/7.5 and 9.5D respectively.

Conclusions:

PTEK is a new protocol for trans-epithelial PTK, which is customised to the patients' ET. Epithelial thickness is higher in the periphery relative to the apex of the cornea in ectatic disorders. Adjusting trans-epithelial ablation depth to the thicker end of the corneal epithelium therefore allows for customised smoothing of the corneal apex, limiting stromal loss. These cases showed a substantial reduction in Kmax and an improvement in unaided visual acuity. Combined PTEK with CXL represents a safe therapeutic alternative for patients with post-LASIK ectasia, which prevents or slows disease progression and decreases dependency on contact lenses or glasses.

Financial Interest:

NONE