Photorefractive Keratectomy (PRK) : Comparison of Corneal Haze Between Two Modes of De-epithelialisation (Laser Versus Manual Alcohol) (H-TransPKR)

Photorefractive Keratectomy (PRK) : Comparison of Corneal Haze Between Two Modes of De-epithelialisation (Laser Versus Manual Alcohol)

Prospective Randomised Controlled Study in 2 Parallel Arms Comparing Corneal Haze, Visual and Refractive Outcomes and Postoperative Pain According to the Mode of De-epithelialisation (Laser Versus Manual Alcohol) During Photorefractive Keratectomy

surgical correction of ametropia. A number of improvements have been introduced to overcome the side effects and complications such as corneal haze, epithelial irregularities induced by wound healing, pain and delayed visual acuity recovery associated with PRK surgery. During traditional PRK, the corneal epithelium is mechanically debrided before stromal ablation is performed. Alcohol PRK is frequently used as an alternative to mechanical epithelial debridement and is considered simpler and faster. Transepithelial PRK (TransPRK) is a new method in which the corneal epithelium is photoablated by the laser in one step using a specific ablation profile. This study attempts to establish a means of quantitatively and objectively measuring corneal haze, using patented software based on optical coherence tomography (OCT) of the cornea. This will confirm or refute the hypothesis of a lower occurrence of corneal haze after TransPRK (experimental group) versus PRK with alcohol (control group). Each patient will have one eye randomised to one of the two groups being compared.

Myopia, Astigmatism, Corneal haze, Trans Photorefractive Keratectomy, Alcohol Photorefractive Keratectomy

A Merocel sponge is soaked in a saline solution to expand before being gently applied to the corneal surface in three gestures similar to painting. This standardised procedure avoids inhomogeneous wetting of the cornea, which would result in uneven ablation. The laser ablation is then performed.

A ring is placed in the centre of the cornea and filled with 20% alcohol. After 20 seconds of exposure, the alcohol is absorbed with a small sponge and the corneal epithelium is debrided with a polyvinyl alcohol expanding sponge (Merocel, Medtronic). The entire cornea is rinsed with balanced salt solution and the epithelium is peeled away from the corneal stroma. The corneal bed is then dried with a small sponge and laser ablation is performed.

Corneal haze assessed by the intensity of the luminosity of the whole cornea (expressed as a percentage) evaluated by the software analysing the corneal OCT images.

Inclusion Criteria: Planned Photorefractive Keratectomy in both eyes Simple myopia or myopic astigmatism, refractive spherical equivalent between -0.50 and -9.0 diopters in both eyes with regular corneal topography Exclusion Criteria: Only one eye operated on At least one contraindication to refractive surgery, namely : keratoconus, minimum corneal thickness < 400 µm, severe dry syndrome, progressive corneal infection Personal history of corneal surgery Personal history of ocular pathology other than simple myopia or myopic astigmatism Pregnant or breastfeeding woman