Transepithelial Photorefractive Keratectomy Group Research Articles

Comparative study of transepithelial versus alcohol-assisted photorefractive keratectomy

Aim The aim of this study was to compare the clinical, refractive, and visual outcome of transepithelial photorefractive keratectomy (T-PRK) to the alcohol-assisted photorefractive keratectomy (AA-PRK). Patients and methods This is a prospective randomized controlled trial that included 60 myopic patients (120 eyes). They were randomized into two groups, 60 eyes each: group I (AA-PRK) and group II (T-PRK). The operation was performed in both groups by the same Excimer laser machine (EX 500 Excimer laser WaveLight). In the alcohol-assisted group, the corneal epithelium was removed by 20% ethyl alcohol followed by Excimer laser to correct the amount of ametropia. In the T-PRK group, the Streamlight PRK software (WaveLight EX 500) was used, which incorporated Excimer laser stromal ablation and epithelial removal in a single step. After completion of each procedure in both groups, mitomycin C with a concentration of 0.02% was used for 30 s, followed by copious irrigation with a cold balanced salt solution. A soft bandage contact lens was applied until epithelial healing was complete for 5 days and changed after 48 h. The patients were evaluated postoperatively on the first, third, and fifth day, then after 1 week, 1 month, and 3 months. On the first visit, uncorrected visual acuity (UCVA), epithelial healing, and postoperative pain were evaluated. At 1-week and 1-month follow-up visits, UCVA, best-corrected visual acuity (BCVA), manifest refraction spherical equivalent (MRSE), Schirmer’s I, and tear break-up time (TBUT) tests were evaluated. The corneal haze was evaluated using a slit lamp biomicroscope and subjectively graded. At the 3-month follow-up, UCVA, BCVA, MRSE, Schirmer’s I test, TBUT test, and root mean square (RMS) assessment for total higher-order aberration were evaluated. Results There was an insignificant difference between the studied groups regarding all baseline ophthalmological assessments including UCVA, BCVA, MRSE, central corneal thickness, RMS, TBUT, and Schirmer’s test (P=0.839, 0.057, 0.187, 0.537, 0.219, 0.013, and 0.151, respectively). After 3 months, the median UCVA was the same in both groups (1.0), while the MRSE did not differ significantly between the two groups (P=0.126), with a median (interquartile range) of −0.25 D (−0.75 to 0.25 D) in the AA-PRK group compared to −0.25 D (−0.50 to 0.3125 D) in the T-PRK group. The healing duration was significantly shorter in the T-PRK group (median=3.0 days) than in the AA-PRK group (5.0 days, P<0.001). The median postoperative pain was also significantly higher in the AA-PRK group (4.0) than in the T-PRK group (3.0, P<0.001). The RMS was significantly lower in the T-PRK group (median=0.35) than in the AA-PRK group (median=0.65, P<0.001). The corneal haze did not differ significantly between the two groups after 1 month (P=0.783). After 3 months, the Schirmer’s test was significantly lower in the AA-PRK group (median=18.0 mm) than in the T-PRK group (19.0 mm, P<0.001), while the TBUT test showed no significant difference (P=0.055). Conclusion The T-PRK technique provided a faster visual recovery with a better refractive outcome, faster healing response, less pain score, and less dryness than the AA-PRK.

Effect of mitomycin C on the corneal endothelial cells of Saudi patients with myopia after transepithelial photorefractive keratectomy: a two-armed cohort study.

To study the effect of mitomycin C (MMC) applied during transepithelial photorefractive keratectomy (TPRK) on the corneal endothelium one week (W1) and three months (M3) after surgery and its determinants. In this two-armed cohort study conducted in 2022, eyes treated with MMC during TPRK (group 1) were compared with eyes not treated with MMC (group 2). The corneal endothelial cell (EC) count, EC density (ECD; cells/mm2), average (µm2), standard deviation (µm2), coefficient of variation (CV%), ECmax, ECmin, and EC percentage of hexagonality were estimated at W1 and M3. The postoperative changes in the EC count in the two groups were compared and correlated with the other independent variables. Group 1 had 26 eyes, and group 2 had 78 eyes. All TPRK indices were significantly higher for the eyes in group 1 than for those in group 2. The MMC usage was not a significant predictor of the change in ECD (P=0.644), change in CV (P=0.374), and change in the percentage of hexagonality of EC (P=0.164) at W1. However, the use of MMC was a significant predictor of changes in CV (P=0.014) and the change in the percentage of hexagonality of EC (P=0.039) at M3. The duration of laser exposure and the size of the optical zone influenced the correlation of MMC use with the changes in EC indices, postoperatively. The use of MMC doesn't affect ECD, CV, and percentage of hexagonality at W1 if other surgical indices are considered. At M3 after operating myopic eyes by TPRK, MMC significantly influence the CV and percentage of hexagonality. The duration of the laser application and the size of the optical zone should be considered when determining the effect of MMC on the EC indices.

Outcomes of Single-Step Transepithelial Photorefractive Keratectomy Compared With Alcohol-Assisted Photorefractive Keratectomy Using Wave-Light EX500 Platform.

Purpose To compare the visual outcome of transepithelial photorefractive keratectomy (PRK) against alcohol-assisted PRK in treating low-to-moderate myopia with or without astigmatism. Setting Dhahran Eye Specialist Hospital, Dhahran, Saudi Arabia. Design This is a retrospective study. Methods Forty eyes of 22 patients with myopia from -0.75 to -6.00 diopters (D) with or without astigmatism from 0 to -3D were included in this study. Preoperative and postoperative data of 20 eyes from 11 patients who underwent transepithelial PRK were compared with 20 eyes from 11 patients who underwent alcohol-assisted PRK were collected and analyzed. The uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest spherical equivalence (SE), manifest cylinder, vector analysis of astigmatism, and efficacy and safety indices were compared between the groups at a mean follow-up of one year postoperatively. Results Baseline characteristics were similar between groups, except the transepithelial PRK group had lower cylinder values than the alcohol-assisted PRK group by 0.69D. Regression analysis was used to control for the difference in the cylinder in all outcome parameters. Both groups had similar mean UDVA (p=0.73), CDVA (p=0.98), the proportion of eyes in either group achieved (20/20, 20/25, and 20/30) UDVA (p=0.72, 0.68 and 0.31 respectively) and percentage of eyes lost two lines of CDVA (p=1.0). There was no statistically significant difference between the two groups in regard to both efficacy and safety indices (p=0.55 and 0.67, respectively). Both groups had similar residual SE (p=0.72), the proportion of eyes within ±0.5D of SE (p=0.29), and residual refractive astigmatism (p=0.87). Both groups had similar difference vectors, surgically induced astigmatism, and correction index (p=0.82, 0.10, and 0.26, respectively). However, the transepithelial PRK group had lower target-induced astigmatism (TIA; p=0.01), higher magnitude of error (ME; p=0.05), and higher angle of error (AE; p=0.02) than the alcohol-assisted PRK group. Conclusion Transepithelial PRK had similar visual and refractive outcomes as alcohol-assisted PRK. This approach was considered as safe and effective as alcohol-assisted PRK in treating patients with low-to-moderate myopia with or without astigmatism.

Role of corneal epithelial thickness during myopic regression in femtosecond laser-assisted in situ keratomileusis and transepithelial photorefractive keratectomy

The study aimed to investigate the relationship between changes in corneal epithelial thickness and the outcome of myopic regression after femtosecond laser-assisted in situ keratomileusis (FS-LASIK) and transepithelial photorefractive keratectomy (TPRK). This study included 45 eyes of 25 patients undergoing FS-LASIK and 44 eyes of 24 patients undergoing TPRK. Myopic regression occurred in these patients postoperatively from 8 to 21 months. The corneal epithelial thickness was measured using a spectral-domain optical coherence tomography at the onset of regression, 3 months after treatment, and 3 months after drug withdrawal. Compared with that of preoperation, corneal epithelial thickness increased when regression occurred in both groups (all P < 0.05). The thickness of central corneal epithelium in FS-LASIK and TPRK groups reached 65.02 ± 4.12µm and 61.63 ± 2.91µm, respectively. The corneal epithelial thickness decreased when myopic regression subsided after 3 months of steroid treatment compared to the onset (P < 0.05). With a decrease in corneal epithelial thickness, the curvature of the anterior corneal surface, central corneal thickness, and refractive power all decreased (all P < 0.05). The corneal epithelial thickness and refractive error remained relatively stable after 3 months of treatment withdrawal (P > 0.05). The corneal epithelial thickness determined the outcome of myopic regression similarly in FS-LASIK and TPRK. When the corneal epithelium thickened, regression occurred. After steroid treatment, epithelial thickness decreased whereas regression subsided.

Clinical outcomes of single-step transepithelial photorefractive keratectomy and off-flap epipolis-laser in situ keratomileusis in moderate to high myopia: 12-month follow-up

BackgroundTo compare the quantitative and qualitative optical outcomes of single-step transepithelial photorefractive keratectomy (TPRK) and off-flap epipolis-laser in situ keratomileusis (Epi-LASIK) in moderate to high myopia.MethodsIn this prospective self-control study, we included patients with moderate to high myopia who were randomized to undergo TPRK in one eye and Epi-LASIK in the other eye. Twelve-month follow-up results for visual acuity, refraction, ocular high-order aberrations, contrast sensitivity, postoperative pain, epithelial healing, and haze grade were assessed.ResultsA total of 64 eyes (32 patients) were enrolled in the study. More eyes completed re-epithelialization in the TPRK group than in the Off-flap Epi-LASIK group 3–4 days postoperatively, while all eyes completed re-epithelialization by 7 days. More eyes achieved a visual acuity (both UDVA and CDVA) of better than 20/20 in the TPRK group than in the Off-flap Epi-LASIK group. The ±0.50 D predictability for correction of the spherical equivalent (SE) was higher in the eyes of the TPRK group (91%) than in those of the off-flap Epi-LASIK group (80%) 12 months after surgery. No significant differences in ocular aberrations, including coma, spherical, and trefoil, were found between the two groups at 12 months. There were also no significant differences in visual acuity, contrast sensitivity, pain, and haze grading between the two groups.ConclusionsBoth TPRK and off-flap Epi-LASIK are safe, effective, and predictable treatments for moderate to high myopia with comparable surgical outcomes.Trial registrationThis study was retrospectively registered on ClinicalTrial.gov (NCT05060094, 17/09/2021).

Comparison of Long-Term Visual and Refractive Results of Transepithelial and Mechanical Photorefractive Keratectomy.

Objectives:The aim of the study was to present and compare 2 years results of mechanical photorefractive keratectomy (M-PRK) and transepithelial photorefractive keratectomy (T-PRK) for myopia.Methods:One hundred and nine eyes of 55 patients were included in this retrospective study. The mean age of the patients was 26.9±5.2 years. Forty-four eyes (40.4%) had M-PRK and 65 eyes (59.6%) had T-PRK. Follow-up time was 2 years. Refractive errors (RE), uncorrected visual acuity (UCVA), and high-order corneal aberrations were compared.Results:The mean RE was −2.33±0.88 D and the mean UCVA was 0.24±0.17 logMAR at baseline for M-PRK patients. At month 24, those measurements were changed to −0.27±0.32 D and 0.99±0.04 logMAR. The mean RE was 2.19±0.73 D and the mean UCVA was 0.23 ± 0.15 logMAR at baseline for T-PRK patients. At month 24, those measurements were changed to −0.14±0.32 D and 0.99±0.01 logMAR. The mean REs significantly decreased and the mean UCVA significantly increased after both type of surgeries (all p<0.001). In M-PRK group, 4 mm zone total corneal aberration and 6 mm total-coma-spherical corneal aberrations were statistically significantly increased in post-operative term. In T-PRK group, only 6 mm total-spherical corneal aberrations were statistically significantly increased in post-operative term. There was no serious complication during surgeries or follow-up time.Conclusion:M-PRK and T-PRK were a safe and effective in the treatment of myopia in 2 years term. Some high-order aberrations may be increase after those treatments.

Transepithelial Laser versus Alcohol Assisted Photorefractive Keratectomy Safety and Efficacy: 1-Year Follow-up of a Contralateral Eye Study.

PurposeTo compare single-step transepithelial photorefractive keratectomy (TPRK) to conventional alcohol assisted epithelial removal then photorefractive keratectomy (AAPRK) regarding pain, epithelial healing, visual acuity, corneal haze measured subjectively and objectively, higher order aberrations changes, contrast sensitivity and vector analysis of astigmatic correction with one year follow-up.MethodsA prospective double-blind randomized study of 29 subjects (58 eyes) who underwent myopic aberration-free laser correction by smart pulse technology using Schwind Amaris 1050 Hz with 1-year follow-up. Right eye was randomly treated by AAPRK or TPRK. Postoperative assessment was performed on day 1 and 3, at 1st week, and 1st, 3rd, 6th, and 12th months. Patients were assessed for pain, epithelial healing, visual acuity, corneal haze, astigmatic correction, higher order aberrations and contrast sensitivity.ResultsEpithelial healing was complete by the 3rd day in 62.1% of AAPRK eyes and in 89.7% of TPRK eyes. First day postoperative pain was higher in TPRK group (p = 0.0134). The decimal uncorrected visual acuity at 12 months was 1.47 ± 0.39 and 1.57 ± 0.38 in the AAPRK and TPRK groups respectively (p = 0.3719). Post-photorefractive keratectomy haze reached a final level of 0.04 ± 0.14 and 0.02 ± 0.1 in AAPRK and TPRK groups respectively (p = 0.5607). Contrast sensitivity was comparable in low and high frequency cycles per degree. Vector analysis of astigmatic correction showed correction index at one year of 0.99 and 1.05 for AAPRK and TPRK groups respectively.ConclusionsAlcohol assisted and transepithelial photorefractive keratectomy have comparable results regarding safety and efficacy.

Comparison of clinical results between trans-PRK and femtosecond LASIK for correction of high myopia

BackgroundTo compare the clinical outcomes of transepithelial photorefractive keratectomy (TPRK) with femtosecond laser-assisted in situ keratomileusis (FS-LASIK) for correction of high myopia.MethodsIn this prospective, non-randomised, cohort study, 85 eyes of 46 patients treated with TPRK and 80 eyes of 42 patients treated with FS-LASIK were included. All eyes were highly myopic (spherical equivalent refraction <− 6.00 diopters). Both TPRK and FS-LASIK were performed by Schwind Amaris 750S excimer laser. Visual acuity, refraction, corneal high order aberration (HOA) and other variables were analyzed before and at 1, 3, 6, 12 months after surgery.ResultsAt 12 months after surgery, uncorrected logMAR distance visual acuity (UDVA) in the TPRK and FS-LASIK groups was − 0.04 ± 0.04 and − 0.01 ± 0.08, respectively (P = 0.039). Corrected logMAR distance visual acuity (CDVA) was − 0.06 ± 0.05 and − 0.04 ± 0.05 in both groups (P = 0.621). For UDVA, 86% of eyes in the TPRK group and 80% in the FS-LASIK group remained unchanged or improved one or more logMAR lines (P = 0.314), compared to preoperative CDVA. For CDVA, 97% of eyes in the TPRK group and 90% in the FS-LASIK group remained unchanged or improved one or more lines (P = 0.096), compared to preoperative CDVA. Spherical equivalent refraction was − 0.05 ± 0.39 and − 0.26 ± 0.47 in both groups (P = 0.030). 87% of eyes in the TPRK group and 73% in the FS-LASIK group achieved ±0.50 D target refraction (P = 0.019). All 85 eyes (100%) in the TPRK group and 75 eyes (92%) in the FS-LASIK group were within ±1.00 D of target (P = 0.003). Root mean square (RMS) of corneal total HOA and vertical coma in the TPRK group were lower compared with the FS-LASIK group (P < 0.001 for both variables).ConclusionsTPRK and FS-LASIK showed good safety, efficacy and predictability for correction of high myopia. Clinical outcomes of TPRK were slightly better than FS-LASIK.

Clinical outcomes of immediate transepithelial photorefractive keratectomy after suction loss during small-incision lenticule extraction.

To investigate the surgical outcomes of immediate transepithelial photorefractive keratectomy (PRK) after suction loss during small-incision lenticule extraction (SMILE) and compare the outcomes with those of uneventful SMILE. Eyereum Eye Clinic, Seoul, South Korea. Retrospective case series. This study included 24 eyes of 12 patients who had uneventful SMILE in one eye and immediate transepithelial PRK after the development of suction loss during the lenticule cut in the contralateral eye. Visual acuity assessments, manifest refraction, and measurements of corneal wavefront aberrations were performed preoperatively and 6 months postoperatively. At 6 months, the mean uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and spherical equivalent were -0.04 ± 0.05, -0.09 ± 0.05, and -0.02 ± 0.24 diopter (D), respectively, in the transepithelial PRK group and -0.10 ± 0.07, -0.06 ± 0.07, and -0.04 ± 0.17 D, respectively (P = .036, P = .109, and P = .671, respectively), in the uneventful SMILE group. The 6-month Snellen UDVA was better than 20/20 for 11 (92%) and 12 (100%) of eyes in the transepithelial PRK and uneventful SMILE groups, respectively. All 24 eyes showed unchanged or improved CDVA and a significant increase in the total corneal higher-order aberrations postoperatively. Corneal spherical aberrations exhibited a significant postoperative increase only in the transepithelial PRK group. Immediate transepithelial PRK after early suction loss during SMILE might be safe and effective, with refractive outcomes that are comparable with those after uneventful SMILE.

Vector Analysis of Changes in the Higher Order Ocular Aberrations and Central Corneal Thickness After T-PRK and Fs-LASIK.

Introduction:Refractive surgery procedures, transepithelial photorefractive keratectomy (T-PRK) and femtosecond laser in situ keratomileusis (Fs-LASIK) are regarded as safe and efficacious methods for correcting myopia and myopic astigmatism. These two methods do not have much differences in results when treating spherical myopia, while some differences does exist in treatment of myopic astigmatism. Vector analysis presents powerful tool to show the real differences between these two methods regarding higher order ocular aberrations and central corneal thickness of treated eyes.Aim:The aim of the study is to investigate changes in higher order ocular aberrations (HOAs) and central corneal thickness (CCT) following treatment of myopia and myopic astigmatism above -5.00DS and up to -2.00DC after either T-PRK or Fs-LASIK.Methods:Patients (30 eyes per group) underwent T-PRK (group I) or Fs-LASIK (group II) procedure using Schwind Amaris 750S laser. HOAs (3mm&5mm pupil) and CCT were measured objectively at pre-, 1,3 & 6 months postop in each case.Results:Key results at 6 months were: i) mean values of trefoil (5mm pupil) were 0.092μm (sd,0.055,95% CI 0.072 to 0.112) & 0.126μm (sd,0.078,95% CI 0.098 to 0.154) in group I, and 0.088μm (sd,0.058,95% CI 0.067 to 0.109) & 0.064μm (sd,0.034,95% CI 0.052 to 0.076) in group II (P=0.001 at 6 months); ii) Changes in CCT (ΔCCT) and best spherical equivalent correction (ΔBSE) was significant in group II (ΔCCT=-26.55[ΔBSE]-14.06,R=0.486,P=0.006) but not in group I (p=0.034).Conclusions:After T-PRK trefoil is worse than Fs-LASIK. The predictability of corneal changes is better following Fs-LASIK. .

Changes in the Higher Order Ocular Aberrations and Central Corneal Thickness After T-PRK and Fs-LASIK.

Introduction:Refractive surgery procedures, transepithelial photorefractive keratectomy (T-PRK), and femtosecond laser in situ keratomileusis (Fs-LASIK) are regarded as safe and efficacious methods for correcting myopia and myopic astigmatism. These two methods do not have many differences in results when treating spherical myopia while differences exist in the treatment of astigmatism correction. Vector analysis presents a powerful tool to show the real differences between these two methods regarding high ocular aberrations and central corneal thickness of treated eyes.Aim:The aim of the study is to investigate changes in higher order ocular aberrations (HOAs) and central corneal thickness (CCT) following treatment of myopia and myopic astigmatism above -5.00DS and up to -2.00DC after either T-PRK or Fs-LASIK.Methods:Patients (30 eyes per group) underwent T-PRK (group I) or Fs-LASIK (group II) procedure using the Schwind Amaris 750S laser. HOAs (3mm&5mm pupil) and CCT were measured objectively at pre-, 1,3 & 6 months postop in each case.Results:Key results at 6 months were: i) mean values of trefoil (5mm pupil) were 0.092μm (sd,0.055,95% CI 0.072 to 0.112) & 0.126μm (sd,0.078,95% CI 0.098 to 0.154) in group I, and 0.088μm (sd,0.058,95% CI 0.067 to 0.109) & 0.064μm (sd,0.034,95% CI 0.052 to 0.076) in group II (P=0.001 at 6 months); ii) Changes in CTT (ΔCTT) and best spherical equivalent correction (ΔBSE) was significant in group II (ΔCCT=-26.55[ΔBSE]-14.06,R=0.486,P=0.006) but not in group I (p=0.034).Conclusions:After T-PRK trefoil is worse than Fs-LASIK. The predictability of corneal changes is better following Fs-LASIK.

Clinical outcomes of mechanical and transepithelial photorefractive keratectomy in low myopia with a large ablation zone

To evaluate the clinical outcomes, vector parameters, and aberrations between mechanical photorefractive keratectomy (PRK) and transepithelial PRK in eyes with low myopia. Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, Korea. Retrospective, comparative case series. Eighty-four eyes of 84 patients with low myopia (≤2.00 diopters) were treated with mechanical or transepithelial PRK (41eyes and 43 eyes, respectively), with the application of alargeoptical zone (OZ). Visual acuity, manifest refraction, slitlampevaluation, autokeratometry, corneal topography, and the evaluation of corneal wavefront aberrations were measured preoperatively and at 1, 3, and 6months after surgery. The efficacy, predictability, vector parameters, corneal aberrations, and safety at 6months after surgery were compared between the two treatment groups. The mean uncorrected distance visual acuity was comparable, at -0.13±0.05 (SD) and -0.15±0.05, in the mechanical and transepithelial PRK groups, respectively, at 6months after surgery. The safety and efficacy indices, vector parameters, and aberrometric values were also comparable between the two groups. The OZ was large in both groups (7.09±0.20mm and 7.12±0.27mm in the mechanical PRK and transepithelial PRK groups, respectively), and showed no significant difference between groups. The corneal total root-mean-square higher-order aberrations and coma significantly reduced after treatment in both groups, and spherical aberrations significantly decreased after transepithelial PRK. Mechanical and transepithelial PRK with a large OZ provided effective and safe outcomes for the correction of low myopia without differences in visual acuity and refractive outcomes between procedures.

Clinical outcomes after laser epithelial keratomileusis (LASEK) and transepithelial photorefractive keratectomy (TPRK) in myopia

Objective: To compare the clinical outcomes between laser epithelial keratomileusis (LASEK) and transepithelial photorefractive keratectomy (TPRK) for treatment of myopia. Methods: Case-control study. We reviewed a total of 90 right eyes that underwent either LASEK or TPRK, with 45 eyes in each group (aged between 18 and 40 years; 9 males and 16 females in the LASEK group, and 30 males and 15 females in the TPRK group) from 2015 to 2016 in Peking Union Medical College Hospital and Tangshan Eye Hospital. All the patients were followed up for 6 months postoperatively. Pain, uncorrected visual acuity (UCVA), and haze were measured at postoperative 3 days, 7 days, 1 month, 3 months and 6 months, and compared using an independent Student t-test between the two groups. Degree of haze, eye pain score, and visual acuity were compared by the Mann-Whitney U test. Results: At 3 days, the pain score was 1 (0,3) in the LASEK group versus 0 (0,1) in the TPRK group (Z=5.643, P=0.001). The UCVA was 4.80±0.10 in the LASEK group versus 4.97±0.07 in the TPRK group (Z=6.930, P=0.000) at 3 days, 4.98±0.08 in the LASEK group versus 5.05±0.06 in the TPRK group (Z=8.147, P=0.000) at 7 days, and 5.02±0.05 in the LASEK group versus 5.06±0.06 in the TPRK group (Z=2.381, P=0.017) at 1 month. The UCVA was also measured at 3 months, 5.07±0.07 versus 5.10±0.07 (Z=1.632, P=0.103), and at 6 months, 5.10±0.07 versus 5.11±0.07 (Z=0.798, P=0.425), respectively, with no statistical significance. The residual diopter was (0.17±0.19) D in the LASEK group versus (0.17±0.20) D in the TPRK group (Z=0.097, P=0.923) at 1 month, (0.03±0.11) D versus (0.07±0.14) D (Z=0.166, P=0.096) at 3 months, (0.07±0.13) D versus (0.07±0.14) D (Z=0.002, P=0.978) at 6 months, respectively. The surface regularity index (SRI) was 0.48±0.09 in the LASEK group and 0.46±0.06 in the TPRK group (t=0.88, P=0.37) at 1 month, and 0.49±0.07 in the LASEK group versus 0.47±0.06 in the TPRK group (t=1.53, P=0.132) at 3 months. Transient haze was documented in 1 eye in each group at 1 month (4.4%), with a maximum index of 0.5. No haze was observed in either group at 6 months. Conclusion: TPRK has the advantages of faster early vision recovery and significantly less pain over LASEK. (Chin J Ophthalmol, 2019, 55: 122-126).

Clinical observation on the efficacy at the early stage of TPRK with assistance of smart pulse technology

Objective To compare the efficacy at the early stage between smart pulse technology (SPT)-assisted transepithelial photorefractive keratectomy (TPRK) and traditional TPRK for correcting of myopia. Methods The data of 90 eyes of 45 cases with myopia were retrospectively analyzed. All cases were divided into two groups randomly. The smart group, 46 eyes of 23 patients, received SPT-TPRK. Contral group, 44 eyes of 22 patients, received traditional TPRK. All patients were followed up for 3 months. Results The stimulus syndrome of eye in the smart group was lighter than that in the TPRK group. After SPT-TPRK the visual acuity in the smart group was better than that at 1 and 3 days after surgery (P=0.000, 0.024). The difference in visual acuity was not statistically significant between the two groups at 10 days, 1 and 3 months after surgery(P=0.277, 0.504, 0.164). The differences of the surface regularity index (SRI) and surface asymmetry index(SAI)of topography in the two groups were statistically significant between preoperative and postoperative 3 months(P=0.090, 0.130, 0.126, 0.201). Conclusion After SPT-TPRK the stimulus syndrome is less serious and visual acuity is better at the early stage after surgery. Key words: Lasers, excimer; Keratectomy, photorefractive (PRK); Myopia; Technology, assisted, smart pulse

Comparing corneal higher-order aberrations in corneal wavefront-guided transepithelial photorefractive keratectomy versus small-incision lenticule extraction

To evaluate the changes in corneal higher-order aberrations (HOAs) after corneal wavefront-guided transepithelial photorefractive keratectomy (PRK) and small-incision lenticule extraction (SMILE). Yonsei University College of Medicine and Eyereum Eye Clinic, South Korea. Retrospective case series. Medical records of patients having either corneal wavefront-guided transepithelial PRK or small-incision lenticule extraction were examined. The root-mean-square total HOAs,3rd-order coma aberration, and 4th-order spherical aberration were measured preoperatively and 6months postoperatively. Independent t tests and analysis of covariance were used to compare changes in corneal HOAs between the 2 groups. The study comprised 77 eyes having corneal wavefront-guided transepithelial PRK and 81 eyes having small-incision lenticule extraction. The total HOAs and spherical aberration increased after transepithelial PRK (all P<.001), whereas coma aberration was stable after transepithelial PRK. The total HOAs, spherical aberration, and coma aberration increased after small-incision lenticule extraction (P<.001 for total HOAs, spherical aberration; P=.004 for coma). At 6months postoperatively, total HOAs and spherical aberration were significantly larger in the transepithelial PRK group than in the small-incision lenticule extraction group. Coma aberration was larger in the small-incision lenticule extraction group than in the transepithelial PRK group. Spherical aberration induction was significantly smaller in the small-incision lenticule extraction group than in the transepithelial PRK group (P<.001), and coma aberration induction was larger in the small-incision lenticule extraction group than in the transepithelial PRK group (P=.011). Small-incision lenticule extraction demonstrated that the induction of total HOAs was comparable to corneal wavefront-guided transepithelial PRK, accompanied by smaller spherical aberration induction and larger coma aberration induction. During small-incision lenticule extraction, surgeons should aim to obtain optimum centration for smaller induction of corneal HOAs.

Effect of accelerated corneal crosslinking combined with transepithelial photorefractive keratectomy on dynamic corneal response parameters and biomechanically corrected intraocular pressure measured with a dynamic Scheimpflug analyzer in healthy myopic patients

To evaluate the effect of accelerated corneal crosslinking (CXL) combined with transepithelial photorefractive keratectomy (PRK) on changes in new dynamic corneal response parameters and the biomechanically corrected intraocular pressure (IOP) measured using a dynamic Scheimpflug analyzer (Corvis ST). Yonsei University College of Medicine and Eyereum Eye Clinic, Seoul, South Korea. Retrospective case series. Medical records of eyes of healthy myopic patients having transepithelial PRK or transepithelial PRK with CXL were examined. Main outcome variables were the biomechanically corrected IOP and new dynamic corneal response parameters including the deformation amplitude ratio at 1.0mm (DAR1) and at 2.0mm (DAR2), stiffness at first applanation and at highest concavity, and the integrated inverse radius preoperatively and 6months postoperatively. The study comprised 69 eyes (69 patients); 35 had transepithelial PRK and 34, transepithelial PRK with CXL. The DAR1, DAR2, and integrated inverse radius significantly increased, while stiffness at first applanation and at highest concavity decreased postoperatively in both groups. Changes in the DAR2 and integrated inverse radius in the transepithelial PRK group were significantly larger than in the transepithelial PRK with CXL group without and with analysis of covariance with the spherical equivalent change or corneal thickness change as a covariate. No significant differences in the biomechanically corrected IOP occurred preoperatively or postoperatively in either group. Results indicate that prophylactic CXL combined with transepithelial PRK has a role in reducing the change in corneal biomechanical properties. The dynamic Scheimpflug analyzer showed stable biomechanically corrected IOP measurements preoperatively and postoperatively.

Myopia correction with transepithelial photorefractive keratectomy versus femtosecond−assisted laser in situ keratomileusis: One-year case-matched analysis

To compare the postoperative clinical outcomes of single-step transepithelial photorefractive keratectomy (PRK) and femtosecond-assisted laser in situ keratomileusis (LASIK). Bergman Clinics, Utrecht, the Netherlands. Retrospective case series. The eyes of consecutive patients who had transepithelial PRK were retrospectively compared with the same number of case-matched eyes (based on the preoperative refractive components) treated with femtosecond-assisted LASIK. The clinical outcomes evaluated were predictability, refractive outcomes, and visual acuity. The Student t test and chi-square test were used for statistical analysis. The study compared 98 patients (196 eyes) who had transepithelial PRK with the outcomes in 196 case-matched eyes that had femtosecond-assisted LASIK. All patients completed the 1-year follow-up. At 1year, 130 eyes (66%) in the transepithelial PRK group and 91 eyes (46%) in the femtosecond-assisted LASIK group achieved an uncorrected distance visual acuity of -0.1 logMAR or better (P<.005), 4 eyes (2%) in the transepithelial PRK and 2 eyes (1%) in the femtosecond-assisted LASIK group lost 2 lines of corrected distance visual acuity (P=.04), and 163 eyes (83%) in the transepithelial PRK and 167 eyes (85%) in the femtosecond-assisted LASIK group were within ±0.50 diopter (D) of emmetropia. The postoperative mean spherical equivalent was +0.11 D ± 0.56 (SD) for transepithelial PRK and -0.09±0.46 D for femtosecond-assisted LASIK (P<.0001). Transepithelial PRK outcomes 1year postoperatively were equivalent to those of femtosecond-assisted LASIK. Transepithelial PRK was efficacious and safe; however, the procedure had a longer recovery time than the femtosecond-assisted LASIK. Mr. Ewering and Dr. Arba-Mosquera are employees of Schwind eye-tech-solutions GmbH and Co. KG. Dr. Luger has no financial or proprietary interest in any material or method mentioned.

Differences in Keratocyte Apoptosis Following Transepithelial and Laser-scrape Photorefractive Keratectomy in Rabbits

Anterior stromal keratocyte cells undergo programmed cell death (apoptosis) in response to corneal epithelial injury. Keratocyte apoptosis may be an initiator of the corneal wound healing response that includes keratocyte proliferation and activation, as well as changes to the overlying epithelium, occurring following refractive surgical procedures such as photorefractive keratectomy (PRK). This study compared the effect of laser-scrape and transepithelial PRK on keratocyte apoptosis. Photorefractive keratectomy was performed in both eyes of 10 New Zealand white rabbits using the Summit Apex excimer laser. Surgery was performed using transepithelial PRK in one eye and laser-scrape PRK in the other. The central cornea was analyzed at 4 hours after surgery using a quantitative TUNEL assay that detects fragmented DNA characteristic of apoptosis. Hepatocyte growth factor (HGF) production by keratocytes was detected by immunocytochemistry. Average apoptotic cells per 400X microscopic field determined by 2 independent masked observers were 0.9 +/- 0.5 (scanning electron microscopy) and 0.2 +/- 0.2 in the transepithelial PRK group compared with 5.1 +/- 2.9 and 4.1 +/- 3.2 in the laser-scrape group. The difference between the two groups was statistically significant for both observers (P < .05, ANOVA). HGF was detected within keratocytes throughout the corneal stroma. Less HGF was detected in the anterior stroma in the laser-scrape group at 4 hours after surgery, consistent with more anterior keratocyte apoptosis in this group. Transepithelial PRK induced less anterior keratocyte apoptosis in rabbits than laser-scrape PRK. This suggests that transepithelial PRK could be useful in preventing or minimizing refractive regression and subepithelial scarring.