Comparison Between TPRK Versus AAPRK in Correction of Myopia
Condition: Refractive Surgery; Myopia
MeSH terms: Myopia
Study type: Interventional

Summary: 
      PURPOSE: The aim of the study is to compare visual acuity means, refractive results, safety,
      and efficacy of TPRK with AAPRK as primary outcomes and surgical time, pain scores, haze
      levels, and healing time as secondary outcomes.

      SETTING: Security Forces Hospital, Ophthalmology Department, Riyadh, Kingdom of Saudi Arabia.

      DESIGN: Prospective, consecutive, nonrandomized case-control comparative study.

      . METHODS: A total of 200 eyes of 100 patients were included. One hundred eyes underwent TPRK
      in the right eye (study group) and 100 eyes underwent AAPRK in the left eye (control group).
      Ablations performed with the Schwind Amaris, 750S. Clinical outcomes were compared Paired
      student's t-tests and Mann-Whitney tests were used for statistical analysis.
    

Detailed description: 
      Introduction Previous studies document that, although Laser in situ keratomileusis (LASIK) is
      the most worldwide performed refractive procedure, surface ablation may be safer to avoid
      flap complications, corneal weakening, and a higher risk of iatrogenic keratectasia
      associated with LASIK and thus the era of surface ablation emerged as an alternative (1).
      Photorefractive keratectomy (PRK) is one of the surface ablation procedures and performed
      after corneal epithelial debridement accompanied by post-operative pain, discomfort, and high
      grade of corneal haze, all of which limit its popularity (2). The traditional method for
      corneal epithelium removal before excimer LASER was manual scraping, which was later enhanced
      by using an alcohol solution 20% or brush (3). In 2003, Camellin introduced a new
      alcohol-assisted technique called laser-assisted subepithelial keratectomy (LASEK) that
      allowed the epithelium to be preserved as a flap and applied back to the stromal corneal bed
      after laser treatment (4). Also in 2003, Pallikaris invented epithelial laser in situ
      keratomileusis (Epi-LASIK) which is another method that uses the epithelial flap and
      performed with a microkeratome (called epi-keratome) with a blunt oscillating blade. After
      trans-epithelial photorefractive keratectomy (TPRK) was introduced, where removal of the
      epithelium is done by phototherapeutic ablation followed by refractive ablation of the
      corneal stroma. Several studies emerged and advocated many techniques for epithelial removal
      , but this 2-step technique was not worldwide used due to the prolonged surgery time with the
      older generation of lasers, corneal dehydration, increased post-operative pain, and a
      deficiency of adjusted nomograms (5). When new generations of faster lasers, improved
      ablation algorithms, and nomograms have emerged, it allowed development of a new TPRK non
      touch: all-surface ablation technique which allows ablation the corneal epithelium and stroma
      in a single-step with one ablation profile. This aspheric profile is calculated according to
      data from the literature estimating that the normal corneal epithelial thickness is 55 μm
      centrally and 65 peripherally at 4 mm radially from the center (6). A number of recent
      studies demonstrated that this single-step TPRK is a relatively new procedure with many
      advantages such as, reduced surgical time, minimizing the size of epithelial defect to that
      required for stromal ablation, no alcohol use avoiding potential toxicity to the limbal
      cells, less post-operative pain and corneal haze with rapid healing time and faster visual
      recovery (7).Thus, there is a need for an updated comparative evaluation based on a larger
      number of eyes. The aim of our study is to compare 6-months un-corrected distant visual
      acuity (UDVA) and best corrected distant visual acuity (BCDVA) means, refractive results,
      safety, and efficacy of single-step TPRK with alcohol-assisted PRK (AAPRK) as primary
      outcomes and comparison of surgical time, pain scores, and haze levels, complete epithelial
      healing time, as secondary outcomes among the two procedures when used to correct mild to
      moderate myopia and myopic astigmatism.

      Subjects and methods This study is a prospective, consecutive, nonrandomized case-control
      study that includes eyes that underwent either single-step TPRK or AAPRK between February
      2017 and April 2018, at the Security Forces Hospital, Ophthalmology department, Riyadh,
      Kingdom of Saudi Arabia. The study was approved by the local ethical board committee. Before
      the surgical procedure, each patient was adequately informed about the study as well as the
      risks and benefits of the surgery, and signed informed consent in accordance with the
      Declaration of Helsinki.

      A total of 200 eyes of 100 consecutive patients were included; One hundred eyes underwent
      TPRK (study group) and 100 eyes underwent AAPRK (control group). The study design choice of
      the procedure was fixed for each patient: the right eye underwent TPRK and the contra-lateral
      left eye AAPRK. Patients demographics and preoperative variables are demonstrated in Table
      (1). There are no significant differences in pre-operative variables of patients in the TPRK
      and AAPRK groups except the patients' genders. The percentage of females is 77% and males
      23%. Patients who attended all visits, without any missing data, were included in the
      statistical analysis.

      Preoperative Examination The preoperative examination included UDVA, BCDVA, manifest and
      cycloplegic refraction, slit lamp biomicroscopy, tonometry, Pentacam camera (OCULUS- Netzteil
      Art., pentacam HR, Germany), tomography (Sirius, SCHWIND eye-tech-solutions GmbH,
      Kleinostheim, Germany), and dilated fundus examination using binocular ophthalmoscopy.
      Contact lenses use and medical history, including any systemic diseases, were recorded.

      Surgical Technique All surgeries were performed with 6th-generation Amaris excimer LASER 193,
      version 750 S (Schwind eye-tech-solutions GmbH& Co.KG, Mainparkstrasse, Kleinostheim,
      Germany). Ablations were based on aberration-free algorithms calculated using ORK-CAM
      software with beam size 0.54 mm full width and high-speed eye tracking. Treatments were
      performed by 2 surgeons (BA & ESH ) using an identical surgical protocol. The treatments were
      mostly aimed at emmetropia. Before the surgery, tetracaine hydrochloride 0.5% ophthalmic
      solution (Bausch & Lomb, Minims) and moxifloxacin 0.5% (Vigamox, Alcon Co.) drops were
      instilled 3 times within a 5-minutes interval. The eyelids were prepared with antiseptic
      Chlorohexidine Gluconate 0.05% solution (Saudi Medical Solution Company) and opened using a
      wire lid speculum. In the AAPRK group, the cornea was exposed to a 20% ethyl alcohol solution
      for 25 seconds with the use of a well. Subsequently, a superficial cut of the epithelium was
      made with either an 8.5 or 9.5 mm diameter trephine. The epithelium was mechanically debrided
      with the well or with a blunt spatula, then LASER treatment with the same machine was
      initiated. In the TPRK group, where aspheric aberration-free TPRK ablation algorithm was used
      (Schwind eye-tech-solutions), the epithelium was removed during laser ablation only from the
      area of the total ablation zone. In both groups and in all cases, immediately after
      treatment, the eye was washed with a balanced salt solution (BSS) for 20 seconds. Then, to
      fight against post-operative corneal haze, mitomycin C 0.02% (MMC) was applied for 30 seconds
      followed by copious irrigation of the eye with BSS. Intra-operative complications were not
      noted and surgical time starting from eye lid speculum insertion to the time of its removal
      at the end of the procedure were recorded. After the surgery, a bandage contact lens was
      applied (BIOMEDICS Evolution CL ocufilcon D 45%, water 55%) for 7 days. The postoperative
      regimen included tobradex eye drops 0.3% (Tobramycin 0.3% - dexamethazone 0.1% sterile eye
      drops, Alcon Co.) with tapering dose for 1 month starting with QID/ 1 week, TID/ 1 week, BID/
      1 week and once a day/1 week, moxifloxacin drops 0.5% (Vigamox, Alcon Co.) for 2 weeks, and
      sodium hyaluronate 0.2% (Hyfresh eye drops, Jamjoom Pharma Co.) drop / 2 hours and a gradual
      decreasing of the frequency for 3 months. Pain killer oral medication tablet/ 6 hours was
      used in the first post-operative days if needed.

      Postoperative Examinations Patients were instructed to visit the clinic for postoperative
      examinations and follow up after 1 day, 1 week, 1 month, 3 months and 6 months. Examinations
      at 1 day, 1 week, 1 month, 3 months, and 6 months included UDVA ,but the BCDVA and manifest
      refraction were measured at 1, 3, and 6 months. Slit lamp biomicroscopy was done in each
      visit. Corneal haze grading was evaluated according to Fantes et al., 1990 proposal (0 = no
      haze; 0.5 = trace haze on oblique illumination; 1 = corneal cloudiness not interfering with
      the visibility of fine iris details; 2 = mild effacement of fine iris details; 3 and 4 =
      details of the lens and iris not discernible). Healing time in which complete
      re-epithelialisation occurred in both eyes were recorded. In post-operative day 1, day 3 and
      week 1, We used a discrete, 11-category numeric pain scale (NPS, 0 = no pain and 10 = the
      worst possible pain) to evaluate pain score in each eye and patients response were recorded
      at early postoperative period. Six months post-operatively, patients were asked about the
      overall satisfaction with each procedure as high, moderate, low, and not satisfied, and
      whether they would decide to have the surgery again (yes, no) were recorded.

      Statistical Analysis Patients' data were entered in Microsoft Excel, copied and analyzed
      using Sigma Plot-Scientific Data Program for the 2 groups, Paired student's t-test was used
      for the UDVA & BCDVA means in decimal values and for MRSE means. Mann-Whitney test was used
      for pain scores, haze levels, and healing time. For all tests, a (P value < 0.05) was
      considered statistically significant. A Graph Pad Prism 5 program was used for graphs
      constructions.
    

Intervention name(s): Transepithelial photorefractive keratectomy; Alcohol assisted photorefractive keratectomy
Intervention type(s): Procedure; Procedure
Intervention description(s): ablations were performed with the Schwind Amaris excimer LASER 750S. Paired student's t-tests and Mann-Whitney tests were used for statistical analysis.; ablations were performed with the Schwind Amaris excimer LASER 750S. Paired student's t-tests and Mann-Whitney tests were used for statistical analysis.
Other intervention name(s): TPRK; APRK
Allocation: Non-Randomized
Intervention model: Parallel Assignment
Intervention model description: Prospective, consecutive, nonrandomized case-control comparative study.
Masking: None (Open Label)
Primary purpose: Treatment