Single-step Transepithelial PRK for Hyperopia

Twelve-Month Outcome of Single-step Transepithelial Photorefractive Keratectomy for Moderate Hyperopia and Hyperopic Astigmatism

Hyperopia is one of the commonest refractive errors encountered in ophthalmology practice. Laser in situ keratomileusis (LASIK) has been widely used to correct hyperopia especially with the advent of femtosecond laser technology allowing larger flap creation suitable for peripheral hyperopic ablations with resultant predictable, effective, and safe refractive outcomes. However, the encountered LASIK flap complications encouraged many surgeons to assess efficiency and safety of surface ablation techniques such as photorefractive keratectomy (PRK) to correct hyperopia.

Although the initial refractive results of conventional manual or alcohol assisted PRK for hyperopia were encouraging, the frequently encountered post-PRK complications including undercorrection, overcorrection and regression of the hyperopic error had downgraded the conventional PRK as a preferred procedure for hyperopic correction. Transepithelial PRK provides an alternative technique to uniformly remove the epithelium using the excimer laser to minimize the potential complications caused by mechanical or alcohol assisted epithelial removal in conventional PRK. Advances in transepithelial PRK technology have allowed refractive surgeons to remove the epithelium followed by stromal laser ablation in a single step instead of performing the procedure in 2 separate steps known as phototherapeutic keratectomy-photorefractive keratectomy (PTK-PRK). Most of the previous studies paid particular attention to investigate the accuracy and safety of single-step transepithelial PRK in correcting myopia and myopic astigmatism. The aim of the current study is to evaluate the visual and refractive outcomes of the single-step transepithelial PRK procedure in correcting moderate hyperopia and hyperopic astigmatism.

Patients with moderate hyperopia or hyperopic astigmatism were planned to undergo transepithelial PRK using the new single-step StreamLight PRK Technology.

Single-step transepithelial Photorefractive keratectomy (PRK) is a corneal refractive surgical procedure utilized to correct myopia, hyperopia and astigmatism where excimer laser is used in a single step to remove the corneal epithelium followed by stromal laser ablation to correct the patient's refractive error.

Uncorrected and corrected distance visual acuity (UDVA,CDVA) measurement using logMAR distant charts.

Cycloplegic sphere, cylinder and refractive spherical equivalent (SEQ) were measured with auto-keratorefractometer (KR-8900:Topcon, Korea republic)

Postoperative keratorefractive changes in mean keratometry (Km) and Q value were recorded using pentacam (Oculus GmbH, Germany)

Post-PRK haze was evaluated using slit lamp based on Fantes et al. scale: Grade 0: No haze, completely clear cornea Grade 0.5: Trace haze seen with careful oblique illumination Grade 1: Haze not interfering with the visibility of fine details of the iris Grade 2: Mild obstruction of iris details Grade 3: Moderate obstruction of the iris and lens Grade 4: Complete opacification of the stroma in the area of the scar, anterior chamber is totally obscured.

Inclusion Criteria: Patients with moderate hyperopia with a hyperopic cycloplegic spherical equivalent between +2 and + 4.5 diopters D. A steep keratometry (Ks) ≤ 46 D. Minimum pachymetry of 500 μm with a calculated residual stromal bed exceeding 350 μm after epithelial and stromal ablation. Exclusion Criteria: Patients not candidate for corneal refractive surgery, Steep cornea (Ks > 46 D) with an expected postoperative keratometry > 48 D, Large angle kappa as estimated by Chord mu > 0.25 mm, Hyperopic amblyopia whether unilateral or bilateral with CDVA less than 0.2 . logMAR acuity, Recent contact lens wear, dry eye disease and autoimmune disorders.

Adib-Moghaddam S, Arba-Mosquera S, Walter-Fincke R, Soleyman-Jahi S, Adili-Aghdam F. Transepithelial Photorefractive Keratectomy for Hyperopia: A 12-Month Bicentral Study. J Refract Surg. 2016 Mar;32(3):172-80. doi: 10.3928/1081597X-20160121-01.