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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 post-LASIK ectasia

Poster Details

First Author: S.Zormpas UK

Co Author(s):    A. Barsam   A. Davidson   O. Bowes   E. Trocme     

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:

2 eyes of 2 patients (N=2) were included. In phototherapeutic epithelial-guided keratectomy (PTEK), ablation depth is set to maximum measured epithelial thickness (ET) but limited to 19-21µm 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 to 6-12 months 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 DISCLOUSRE: NONE

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