|Year : 2013 | Volume
| Issue : 4 | Page : 263-266
Transepithelial photorefractive keratectomy versus LASIK in correction of mild and moderate myopia
Waleed A Ghobashy, Mohammed E Helmy, Ahmad A Abdel Ghani
Department of Ophthalmology, Faculty of Medicine, Suez Canal University Hospital, Egypt
|Date of Submission||10-Oct-2013|
|Date of Acceptance||10-Dec-2013|
|Date of Web Publication||28-Apr-2014|
Waleed A Ghobashy
MD, PhD, Suez Canal University Hospital, Ophthalmology Department
Source of Support: None, Conflict of Interest: None
The aim of this study was to compare both transepithelial photorefractive keratectomy (trans-PRK) and LASIK in correction of mild and moderate myopia in terms of effectiveness, visual recovery, and safety.
Materials and methods
This was a prospective case - control series. Group I included 30 myopic eyes (16 patients) with spherical equivalent -1.00 to -6.00 D that were subjected to trans-PRK using a Schwind Amaris 500E excimer laser, with a trans-PRK platform. A case-adjusted group II (control group) included 30 myopic eyes (18 patients) with spherical equivalent -1.00 to -6.00 D that were subjected to LASIK using a Schwind Amaris 500E excimer laser, with a LASIK platform. Uncorrected visual acuity (UCVA) was measured on the first day, first week, 1 month, and at 6 months, together with manifest refraction. Postoperative pain was assessed using a visual analog scale. The occurrence of complications was documented.
Patients in group I showed slower visual recovery, with a mean of UCVA 0.34 ± 0.19 on the first postoperative day compared with group II (0.76 ± 0.42). However, both groups achieved a mean UCVA of 1.00 by the end of the sixth month. Manifest refraction was comparable in both groups, with a mean of −0.60 ± 1.07 D in group I and −0.15 ± 0.06 D in group II, by the end of the study. Pain was significant in group I, with an average score of 3.2 ± 1.09 in the first day decreasing to zero by the end of the first week in comparison with group II with no pain in the first day until the end of the first week. No complications were recorded in either of the two groups during the study period.
Trans-PRK may offer a safe and effective alternative to LASIK in the treatment of mild and moderate myopia, especially in cases of thin cornea.
Keywords: Transepithelial photorefractive keratectomy, lasik, myopia, uncorrected visual acuity, postoperative pain
|How to cite this article:|
Ghobashy WA, Helmy ME, Abdel Ghani AA. Transepithelial photorefractive keratectomy versus LASIK in correction of mild and moderate myopia. J Egypt Ophthalmol Soc 2013;106:263-6
|How to cite this URL:|
Ghobashy WA, Helmy ME, Abdel Ghani AA. Transepithelial photorefractive keratectomy versus LASIK in correction of mild and moderate myopia. J Egypt Ophthalmol Soc [serial online] 2013 [cited 2020 Jun 5];106:263-6. Available from: http://www.jeos.eg.net/text.asp?2013/106/4/263/131623
| Introduction|| |
Increasingly, more patients are willing to become independent of use of their glasses. This has been spurred by the recognizable cost effectiveness of keratorefractive surgery, which gained a momentum with the invention of LASIK in the early 1990s. However, the limitations of LASIK, such as limited available corneal thickness, as well as potential flap-related concerns, led to the era of surface ablation to emerge as an alternative. Photorefractive keratectomy (PRK)-associated discomfort, relatively delayed visual recovery, and the potential development of haze  are still significant concerns for both surgeons and patients when making the decision to perform PRK. Transepithelial photorefractive keratectomy (trans-PRK) is a relatively new modification of the conventional PRK, in which the epithelial removal is achieved using the excimer laser instead of alcohol and manual scraping. This is supposed to create a smoother crater, allowing relatively rapid healing of the epithelium, resulting in faster visual recovery and less discomfort . With these issues in mind, we designed this study to measure visual outcome, postoperative pain, and occurrence of complications among patients with mild and moderate myopia treated by LASIK and trans-PRK to determine whether one procedure offers any advantages or disadvantages over the other .
| Materials and methods|| |
Patients with systemic or ocular disease that may interfere with the healing process of the cornea, such as rheumatoid arthritis, dry-eye syndrome, anterior or posterior uveitis, keratoconus, and also corneal dystrophy or degeneration, glaucoma, retinal diseases, lens opacity, history of severe ocular trauma, and previous ocular surgery, were excluded from the study.
This was a prospective case - control study. Group I included 30 myopic eyes (16 patients) with spherical equivalent −1.00 to −6.00 D that were subjected to trans-PRK using a Schwind Amaris 500E excimer laser (Schwind Eye-Tech, Germany), with a trans-PRK platform (both epithelial removal and ametropia are performed in a single step) with a 500 Hz excimer laser with spot size of 0.54 mm, and active 5 D eye tracking, after standard disinfection and ocular draping, with instillation of topical benoxinate hydrochloride 0.4% as a topical anesthetic.
Immediately after laser ablation, a topical application of mitomycin-C 0.02% (0.2 mg/ml) diluted in a balanced salt solution was instilled in each eye with a microsponge placed over the ablated stroma for 15-30 s . The corneal surface and the entire conjunctiva were then irrigated vigorously with 20 ml cold balanced salt solution to remove the residual mitomycin-C. At the end of the procedure, a bandage contact lens was applied, followed by one drop of a tobramycin-dexamethasone suspension 0.1%.
Patients were instructed to use topical prednisolone acetate suspension 1% four times daily, tapered over 4 weeks according to corneal haze and intraocular pressure, ketorolac tromethamine ophthalmic solution 0.4% three times daily for 2 weeks, moxifloxacin hydrochloride ophthalmic solution 0.5% four times daily for 1 week, as well as ibuprofen 400 mg tablet orally twice daily for 4 days .
Bandage contact lens was removed on the fourth to the sixth postoperative day guided by epithelial healing and patient comfort.
A case-adjusted group II (control group) included 30 myopic eyes (18 patients) with spherical equivalent -1.00 to −6.00 D that were subjected to LASIK using a Schwind Amaris 500E excimer laser, with a LASIK platform. After standard disinfection and ocular draping, with instillation of topical benoxinate hydrochloride 0.4% as a topical anesthetic, a Moria II microkeratome (Moria, Paris, France) was used to create a 120-160 μm flap with a superior hinge. The flap was elevated with a special spatula. A 500 Hz laser with a spot size of 0.54 mm was used to achieve the desired ammetropia. Irrigation of the ablated stromal bed with balanced salt solution, reposition of the premarked flap, and drying of the edges with microsponge, followed by application of one drop of a tobramycin-dexamethasone suspension 0.1% were performed.
Patients were instructed to use a topical prednisolone acetate suspension 1% four times daily, for 1 week, moxifloxacin hydrochloride ophthalmic solution 0.5% four times daily for 1 week, as well as ibuprofen 400 mg tablet orally twice daily for 4 days.
Uncorrected visual acuity (UCVA) and best-corrected visual acuity were measured using the Snellen chart on the first day, first week, 1 month, and at 6 months along with manifest refraction by retinoscopy. Postoperative pain was assessed using a visual analog scale . The occurrence of complications was documented.
In the first postoperative week, all patients were examined with a slit lamp and the area of the epithelial defect was measured with its ruler to identify the time of complete healing.
For evaluation of haze, we used Hanna's grading scale from 0 (no haze) to 4+ (dense white corneal haze) .
Decimal values for UCVA and best-corrected visual acuity were used for statistical purposes; preoperative central corneal thickness, preoperative and postoperative K-readings, optical zone of ablation, depth of ablation, and residual stromal thickness were documented using Sirius 3D corneal analysis, merging Scheimpflug technology, with placido topography (Costruzioni Strumenti Oftalmici, Italy).
Mean, SD, and correlation coefficient were calculated for variables, with a paired Student's t-test as a significant test. P value less than 0.05 was considered statistically significant.
| Results|| |
Sixty eyes of 34 patients were included in this study, assigned to two groups. Group I included 30 myopic eyes of 16 patients, mean UCVA 0.14 ± 0.05, subjected to trans-PRK; 13 patients (81%) of this group were women. Group II included 30 myopic eyes of 18 patients, mean UCVA 0.16 ± 0.05, subjected to LASIK; with 12 patients (75%) of this group were women.
Preoperative data are listed in [Table 1] and [Table 2].
In group I, contact lens was removed on average by the sixth postoperative day, and there was a strong negative correlation (-0.723) between depth of ablation and the period needed to achieve healing of the epithelium.
There was a strong positive correlation (0.896) between a wider optical zone and postoperative pain on the first postoperative day.
Postoperative data are shown in [Table 3].
Ablation depth was significantly higher (mean 119.3 ± 18.8 μm) in group I than in group II (mean 53.2 ± 22.6 μm); still, the residual stromal thickness was greater in group I than in group II, and this relationship was highly significant (P = 0.00299).
The UCVA was significantly better in group II on the first day, with a mean of 0.76±0.42, and also by the end of the first week, with a mean of 0.96 ± 0.05. By the end of the first month, there was no significant difference between the two groups in refraction and UCVA. This remained up to the end of the study.
Pain was significantly worse in group I on the first day, with a mean score of 3.2 ± 1.09; however, the difference between both groups was insignificant by the end of the first postoperative week.
Minimal and insignificant haze was noticed in patients of group I, which tended to fade away by the end of the sixth month of the study.
No complications were recorded in any of the patients in the two groups.
| Discussion|| |
This study suggests that trans-PRK as well as LASIK are effective procedures for the correction of mild and moderate myopia. Although the LASIK group (group II) showed superior visual results in the early postoperative period, there was no statistically significant difference in the outcomes of UCVA by 6 months. Similar results were obtained by Hatch and colleagues ,,,, as they both compared PRK with thin-flap LASIK in terms of visual outcome. Our visual outcome was better than those obtained by Wang and colleagues as 80% of trans-PRK eyes in our study achieved UCVA of 1.00 by the end of the first postoperative month compared with only 39% of the patients in their study; this shows the superior outcome to the single-step trans-PRK provided by Schwind Amaris 500E compared with the older Schwind ESIRIS, which utilized the PTK mode, followed by PRK in the study of Wang et al. . Another older study carried out by Clinch et al.  to compare trans-PRK with mechanical removal of epithelium showed more humble results with only 17.9% of patients in trans-PRK group achieving a UCVA of 1.0 by the end of the first postoperative month.
Emmetropia (± 0.5 D) was achieved in 80% of patients in group I and in 100% of patients in group II by the end of the sixth postoperative month. These are comparable with the results reported by Wang and colleagues ,.
Pain was significantly worse in the trans-PRK group (group I), with an average score of 3.2 ± 1.1 until the end of the first postoperative week, and then subsided considerably, with no significant difference in pain between the two groups later. A similar average pain (3 ± 1.2) score was found by Buzzonetti et al.  as they utilized a Nidek CXIII excimer laser to perform trans-PRK.
Haze was not a significant issue in the trans-PRK group; it never exceeded the score of 2, and in all patients, it regressed to a level below score 1 by the end of the study. This could be attributed to the routine use of intraoperative mitomycin-C in these patients as well as the smoother surface created by the laser removal of epithelium. These results could be compared with those obtained by Hashemi et al. , with a slightly higher score of haze (score 3).
| Conclusion|| |
Trans-PRK may offer a safe and effective alternate to LASIK in the treatment of mild and moderate myopia, especially in cases of thin cornea, with tolerable discomfort and delayed visual recovery limited to the early postoperative week.
| Acknowledgements|| |
Conflicts of interest
There are no conflicts of interest.
| References|| |
|1.||Hashemi H, Taheri SMR, Fotouhi A, Kheiltash A. Evaluation of the prophylactic use of mitomycin-C to inhibit haze formation after photorefractive keratectomy in high myopia: a prospective clinical study. BMC Ophthalmol 2004; 4:12. |
|2.||Wang DM, Du Y, Chen GS, Tang LS, He JF. Transepithelial photorefractive keratectomy mode using SCHWIND-ESIRIS excimer laser: initial clinical results. Int J Ophthalmol 2012; 5:334-337. |
|3.||Manche EE, WW Haw. Wavefront-guided laser in situ keratomileusis (Lasik) versus wavefront-guided photorefractive keratectomy (Prk): a prospective randomized eye-to-eye comparison (an American Ophthalmological Society thesis). Trans Am Ophthalmol Soc 2011; 109:201-220. |
|4.||Hatch BB, Moshirfar M, Ollerton AJ, Sikder S, Mifflin MD. A prospective, contralateral comparison of photorefractive keratectomy (PRK) versus thin-flap LASIK: assessment of visual function. Clin Ophthalmol 2011; 5:451-457. |
|5.||Pakravan M, Roshani M, Yazdani S, Faramazi A, Yaseri M. Pregabalin and gabapentin for post-photorefractive keratectomy pain: a randomized controlled trial. Eur J Ophthalmol 2012; 22:S106-S113. |
|6.||Szabo V, Balogh K, Suveges I, Racz K, Hunyady L, Nagy ZZ. The role of lumican and keratocan genes in persistent subepithelial corneal haze following excimer laser photorefractive keratectomy. Mol Vis 2006; 12:597-605. |
|7.||He TG, XR Shi. Clinical study of ultrathin flap LASIK and LASEK for the treatment of high myopia with thin cornea [article in Chinese]. Zhonghua Yan Ke Za Zhi 2006; 42:517-521. |
|8.||Khoramnia R, et al. Precision, morphology, and histology of corneal flap cuts using a 200-kHz femtosecond laser. Eur J Ophthalmol 2012; 22:161-167. |
|9.||Slade SG. Thin-flap laser-assisted in situ keratomileusis. Curr Opin Ophthalmol 2008; 19:325-329. |
|10.||Clinch TE, Moshirfar M, Weis JR, Ahn CS, Hutchinson CB, Jeffrey JH. Comparison of mechanical and transepithelial debridement during photorefractive keratectomy. Ophthalmology 1999; 106:483-489. |
|11.||Buzzonetti L, Petrocelli G, Laborante A, Mazzilli E, Gaspari M, Valente P, Francia E. A new transepithelial phototherapeutic keratectomy mode using the NIDEK CXIII excimer laser. J Refract Surg 2009; 25:S122-S124. |
[Table 1], [Table 2], [Table 3]