Corneal epithelial healing after photorefractive keratectomy: analytical study

Clinical Outcomes of Aberration-Free All Surface Laser Ablation (ASLA) vs. Aberration-Free ASLA Assisted by Smart Pulse Technology in High Myopia: A One-Year Follow-Up Study

Purpose

To compare the clinical outcomes of aberration-free all surface laser ablation (ASLA) with and without the use of smart pulse technology (SPT) in high myopia.

Methods

This study retrospectively analyzed 138 eyes (138 patients, only the right eye was selected) treated for high myopia (spherical equivalent ≥−6.00 diopters) using aberration-free ASLA (non-SPT group; 85 eyes) and aberration-free ASLA assisted by SPT (SPT group; 53 eyes). Examinations such as visual acuity, refraction, and haze were performed before the 12-month follow-up. Corneal epithelial healing time was assessed in the first postoperative day. Visual acuity and refraction examination were performed at 7 days and 1, 3, 6, and 12 months postoperatively. Corneal haze was evaluated in 1, 3, 6, and 12 months. Safety, efficacy, and corneal wavefront aberrations were assessed 12 months after the treatment.

Results

At 12 months postoperatively, 60% versus 40% of eyes achieved 20/16 Snellen lines or better, and 92% versus 82% of eyes achieved 20/20 Snellen lines or better visual acuity in the SPT and the non-SPT groups, respectively. The average postoperative epithelial healing time was 3.75 ± 1.00 days in the SPT group and 3.73 ± 1.30 days in the non-SPT group (P ≥ 0.05). The safety and the efficacy index of the SPT group were better than those of the non-SPT group in the follow-ups. The attempted spherical equivalent before the surgery and the achieved spherical equivalent at 12 months were comparable between the two groups. Regarding the aberrations, the results of Coma 90° in the SPT group were better than those in the non-SPT group (P ≤ 0.05), but the increase of RMS HOAs (root mean square higher order aberrations), Coma 0°, and spherical aberration postoperatively had no statistical difference between the two groups (P ≥ 0.05). Conclusions: Both aberration-free ASLA with and without SPT showed favorable safety, effectiveness, and predictability within 12 months for high myopia. And, ASLA using SPT might have potential advantages in the long-term visual quality.

Transepithelial photorefractive keratectomy for myopia: effect of age and keratometric values

AIM

To investigate demographic and preoperative factors increasing the risk of ametropia following transepithelial photorefractive keratectomy (transPRK) in myopia and myopic astigmatism.

METHODS

This retrospective cohort study included myopic eyes (-0.50 to -8.75 D) with or without astigmatism (up to 3.50 D) enrolled at Dr. Yap Eye Hospital Yogyakarta. TransPRK was performed using Technolaz 217z100 excimer laser. Subjects were clustered into ametropia and emmetropia group based on uncorrected distance visual acuities (UDVA) 3mo post-operatively. Multiple preoperative and intraoperative parameters were analyzed using Logistic regression to obtain their effect on ametropia risk following transPRK.

RESULTS

A total of 140 eyes of 87 consecutive subjects were studied. Prevalence of ametropia following transPRK was 20 (14.29%) eyes. Subjects in ametropia group were significantly older than the emmetropia group (31.80±14.23 vs 18.88±2.41, respectively; P<0.001). Bivariate Logistic regression analysis showed that older age (OR=1.23), higher preoperative spherical equivalent (>-6 D; OR=12.78), steeper anterior keratometric readings (Kmax>45 D and mean K>44 D; OR=4.28 and 4.35, respectively) increased the risk of ametropia following transPRK. Adjusted multivariate Logistic regression analysis showed that age was the strongest predictor for the incidence of ametropia following transPRK. Complications of transPRK were overcorrection, suspected posterior keratoectasia and accommodation insuffiency.

CONCLUSION

Older age can be the strongest factor for increasing ametropia risk following transPRK. Cut-off points of Kmax and mean K at 45 and 44 D respectively are proposed as the predictors for ametropia following transPRK.

LASIK versus PRK for high astigmatism

PURPOSE

To compare the refractive outcomes of laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) for myopic astigmatism of 3 diopters (D) or more.

STUDY DESIGN

Retrospective matched comparative study.

METHODS

This study include consecutive myopic patients (SE 0 to -10 D) undergoing LASIK or PRK between 2007 and 2016 with astigmatism of 3 to 6 D, and postoperative follow-up of at least 30 days for LASIK and 60 days for PRK, compared outcomes of LASIK and PRK eyes.

RESULTS

The LASIK and PRK groups comprised 175 eyes of 175 patients each, with median follow-up of 39 and 139 days, respectively (P < 0.001). Mean preoperative manifest astigmatism was -3.35 ± 0.46 and -3.42 ± 0.51 D (P = 0.92), postoperative SE was -0.43 ± 0.55 and -0.16 ± 0.64 D (P < 0.001), and arithmetic astigmatism was -0.59 ± 0.46 and -0.88 ± 0.60 D (P < 0.001), for the LASIK and PRK groups, respectively. Fifty-seven and 64.0% eyes had postoperative SE within ± 0.5 D of emmetropia (P = 0.19), and 57.7 and 38.8% eyes were within 0.5 D of attempted astigmatic correction (P < 0.001) for the LASIK and PRK groups, respectively. More PRK eyes were overtreated regarding both SE and astigmatism than LASIK eyes (P < 0.001). The efficacy and safety indices were close to 1.0 in both groups. The surgically induced astigmatism, magnitude of error, index of success, correction index and flattening index were all better in the LASIK group.

CONCLUSION

Both LASIK and PRK achieve good outcomes in high astigmatism. LASIK achieved mild superiority over PRK.

Predictors of myopic photorefractive keratectomy retreatment

PURPOSE

To determine the factors associated with retreatment after photorefractive keratectomy (PRK) in myopic eyes.

SETTING

Care-Vision Laser Centers, Tel-Aviv, Israel.

DESIGN

Retrospective cohort study.

METHODS

A large database on myopic PRK with mitomycin-C (MMC) performed from 2005 to 2012 was studied. Patients were divided into 2 groups according to whether they had retreatment. Multiple preoperative and intraoperative parameters were analyzed for association with retreatment.

RESULTS

A total of 9699 eyes of 9699 consecutive patients were studied. The mean age was 25.9 years ± 7.3 (SD); 54.1% were men. The mean preoperative subjective spherical equivalent and astigmatism were -4.30 ± 2.18 diopters (D) (range -0.5 to -13.0 D) and 0.77 ± 0.83 D (range 0 to 6.0 D), respectively. Two hundred twenty-three eyes (2.30%) were retreated. The 2-year retreatment rate decreased from 42 (6.17%) for primary PRK treatments done in 2005 to 2 (0.10%) for primary PRK done in 2012 (R² = 0.79, P < .001). Multiple binary logistic regression analysis showed that transepithelial PRK, astigmatism equal to or higher than 3.5 D, and surgeon factor significantly increased the odds of retreatment. Additional parameters significant on univariate analysis alone included age older than 40 years, low preoperative sphere, maximum ablation depth less than 45 μm, preoperative corrected distance visual acuity better than 20/20, MMC application longer than 40 seconds, and optical ablation zone smaller than 7.0 mm.

CONCLUSION

The retreatment incidence of PRK has continued to decrease. High astigmatism and transepithelial PRK were associated with increased myopic PRK retreatment rates.

[Transepithelial photorefractive keratectomy : Results and clinical experiences]

OBJECTIVE

To analyze and assess the refractive outcome after transepithelial photorefractive keratectomy (TransPRK).

MATERIAL AND METHODS

The treatment was performed with the AMARIS 1050RS laser (SCHWIND eye-tech-solutions GmbH, Kleinostheim, Germany). The method used an aspheric, aberration-neutral ablation profile and a standardized epithelial tissue removal of 55 µm in the center and 65 µm at a radius of 4 mm as well as SmartPulse technology. Only spherical and/or cylindrical refraction values were treated. Only untreated eyes with preoperative best corrected visual acuity equal to or better than 0.8 were included in the cohort. Follow-up examinations were performed after 1 and 4 days, after 1 and 3 months and after 1 year RESULTS: A total of 939 consecutive TransPRK laser treatments performed in the period from December 2014 to December 2016 were retrospectively analyzed. The mean age of the patients was 34 years. The preoperative sphere had a range of -7.75 D up to +3.00 D and cylinders up to 5.00 D. The 3‑month follow-up control was performed in 728 eyes (77.5%). The predictability showed 89% of eyes within the target correction of less than 0.50 D and 99% of eyes less than 1.00 D. The astigmatic correction showed 91% of eyes with less than 0.50 D. In the safety 1% of eyes showed a visual loss of 2 Snellen lines because of haze. In 26 eyes (2.7%) follow-up treatment was performed with renewed TransPRK laser treatment, in the myopic cohort in 1.8% and in the hyperopic cohort in 13.0%. A residual refraction occurred in 20 eyes without haze and 6 eyes showed a residual refraction with signs of haze.

CONCLUSION

The TransPRK led to similar results to intrastromal refractive surgery techniques but with fewer clinical complications.

Advanced Surface Ablation With a New Software for the Reduction of Ablation Irregularities

PURPOSE

To compare visual outcomes and postoperative aberrations after surface ablation performed with a 750-Hz versus a 1,050-Hz excimer laser coupled with an ablation software designed to reduce corneal surface irregularity.

METHODS

Retrospective comparative trial of myopic eyes that had refractive surgery consecutively treated with transepithelial advanced surface ablation with a 750-Hz excimer laser (750 group) versus a 1,050-Hz excimer laser coupled with the Smart Pulse Technology ablation software (SPT group). The SPT algorithm is a laser pulse technology software aimed at reducing surface irregularity of the stromal bed at the end of treatment. The authors evaluated the effect of this smoothing on final visual acuity. Patients were observed for 6 months.

RESULTS

A total of 139 eyes in the 750 group and 40 eyes in the SPT group were evaluated. Epidemiological and preoperative refractive data of the two groups were comparable. Uncorrected distance visual acuity improved with time and was significantly better in the SPT group (-0.04 ± 0.61 logMAR for the SPT group vs 0.02 ± 0.78 logMAR for the 750 group) (P < .001). At 6 months, 55% versus 21% achieved 20/16 or better (P = .005) and 90% versus 65% achieved 20/20 or better (P = .019) visual acuity in the SPT and 750 groups, respectively. Corrected distance visual acuity improved with time and appeared to be influenced by group (P = .054), with better results in the SPT group. Coma and trefoil improved significantly with time in a similar manner in both groups.

CONCLUSIONS

Surface ablation with the 1,050-Hz excimer laser and SPT software, aimed at reducing the final superficial stromal irregularity, led to improvement of 6-month uncorrected visual acuity. [J Refract Surg. 2017;33(2):89-95.].

Trans advanced surface laser ablation (TransPRK) outcomes using SmartPulseTechnology

PURPOSE

To evaluate early visual rehabilitation, post-operative pain, epithelial healing and haze after transepithelial photorefractive keratectomy (TransPRK) using the SmartPulseTechnology (SPT) of Schwind Amaris (Schwind eye-tech-solutions GmbH, Kleinostheim, Germany).

METHODS

This was a retrospective comparative evaluation of a cohort of myopic patients undergoing TransPRK with SPT (group 1), with one matched control group that underwent conventional TransPRK (group 2). All cases had a 6-month post-operative follow-up including visual acuity and slit-lamp examination. Subjective evaluation of pain was recorded post-operatively.

RESULTS

49 eyes of 25 patients in group 1 and 40 eyes of 20 patients in group 2 were enrolled. The patients' visual rehabilitation was significantly faster in group 1, one day and one week post-operatively (P<0.05). From one month onward there was no significant difference between the groups. The epithelial defect size was significantly smaller on post-operative days 1 and 2 for group 1 (P<0.05 in both cases). The pain score was also significantly less in group 1 (P<0.05). The haze level had no significant difference between the groups at any post-operative point (P>0.05).

DISCUSSION

TransPRK using SPT provides promising results in the early post-operative period. Visual rehabilitation, re-epithelialization and pain were faster in the early post-operative period in group 1 in comparison with group 2. Haze formation was not significantly different between the two groups; however, it was consistently less in group 1.

Efficacy of systemic vitamin C supplementation in reducing corneal opacity resulting from infectious keratitis

The objective of this study was to determine the effect of vitamin C supplementation on reducing the size of corneal opacity resulting from infectious keratitis.The study included 82 patients (82 affected eyes), admitted for infectious keratitis from January 2009 to August 2013, who were followed for more than 3 months. Patients were divided into control, oral vitamin C (3 g/d), and intravenous vitamin C (20 g/d) groups during hospitalization. Corneal opacity sizes were measured using anterior segment photographs and Image J program (version 1.27; National Institutes of Health, Jinju, South Korea) at admission, discharge, and final follow-up. The corneal opacity size used for analysis was the measured opacity size divided by the size of the whole cornea.The corneal opacity size decreased by 0.03 ± 0.10 in the oral vitamin C group, 0.07 ± 0.22 in the intravenous vitamin C group, and 0.02 ± 0.15 in the control group. Intravenous vitamin C reduced the corneal opacity size more than oral vitamin C (P = 0.043). Intravenous vitamin C produced greater reduction in corneal opacity size in younger patients (P = 0.015) and those with a hypopyon (P = 0.036).Systemic vitamin C supplementation reduced the size of corneal opacity resulting from infectious keratitis. Intravenous vitamin C was more beneficial than oral supplementation, especially in younger patients and those with hypopyon.

Nodular epithelial hyperplasia after photorefractive keratectomy followed by corneal collagen cross-linking

This study describes a case of nodular epithelial hyperplasia and stromal alterations in a patient with keratoconus who was submitted to topography-guided photorefractive keratectomy (PRK) followed by corneal collagen cross-linking. Debridement of the epithelial nodule was performed. After a 2-year followup, a new topography-guided PRK was indicated.

Corneal transparency: genesis, maintenance and dysfunction

Optimal vision is contingent upon transparency of the cornea. Corneal neovascularization, trauma and, surgical procedures such as photorefractive keratectomy and graft rejection after penetrating keratoplasty can lead to corneal opacification. In this article we identify the underlying basis of corneal transparency and factors that compromise the integrity of the cornea. With evidence from work on animal models and clinical studies, we explore the molecular mechanisms of both corneal avascularity and its dysfunction. We also seek to review therapeutic regimens that can safely salvage and restore corneal transparency.

The Effect of Moxifloxacin and Gatifloxacin on Long-term Visual Outcomes Following Photorefractive Keratectomy

PURPOSE

To compare the effect of gatifloxacin and moxifloxacin on visual outcomes after photorefractive keratectomy (PRK).

METHODS

Thirty-five PRK patients were treated postoperatively with gatifloxacin (Zymar) in one eye and moxifloxacin (Vigamox) in the fellow eye. Postoperative regimens were otherwise identical. In a previous study (initial phase), we evaluated epithelial healing. In this study (second phase), we compared uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), manifest spherical equivalent (MSE), and corneal haze at 6 months postoperatively for 32 patients using the Wilcoxon signed ranks test.

RESULTS

No statistically significant difference was noted between eyes treated with Zymar and Vigamox in terms of UCVA, BSCVA, MSE, or corneal haze at 6 months postoperatively. Two (6%) Vigamox-treated eyes versus 0 (0%) Zymar-treated eyes lost one line of BSCVA from preoperative examination. Median UCVA and MSE were equivalent for both groups.

CONCLUSIONS

At 6 months after PRK, there was no significant difference in visual outcomes with either antibiotic.

Interocular high-order corneal wavefront aberration symmetry

The interocular symmetry of the high-order corneal wavefront aberration (WA) in a population of myopic eyes was analyzed before and after photorefractive keratectomy (PRK). The preoperative and one-year postoperative corneal aberration data (from third to seventh Zernike orders) for 4- and 7-mm pupils from right and left eyes were averaged after correcting for the effects of enantiomorphism to test for mirror symmetry. Also, the mean corneal point-spread function (PSF) for right and left eyes was calculated. Preoperatively, a moderate and high degree of correlation in the high-order corneal WA between eyes was found for 4- and 7-mm pupils, respectively. Myopic PRK did not significantly change the interocular symmetry of corneal high-order aberrations. No discernible differences in the orientation PSF between eyes were observed one year after surgery in comparison with the preoperative state over the two analyzed pupils.

Roughness of Excimer Laser Ablated Corneas With and Without Smoothing Measured With Atomic Force Microscopy

PURPOSE

To analyze the surface roughness of porcine corneas after excimer laser ablation with and without the smoothing procedure by means of atomic force microscopy.

METHODS

Excimer laser photorefractive keratectomy (PRK) was performed on eight porcine corneas. Immediately following the procedure, smoothing was performed on four corneas using a viscous solution of 0.25% sodium hyaluronate. The corneas were examined in balanced salt solution after fixation in 2.5% glutaraldehyde solution using atomic force microscopy. Quantitative analysis of the ablated stromal surface topography was performed using the section analysis module of the atomic force microscopy software. Repeated measurements were made over small areas (< or =50 microm2) near the center of each ablation, with a vertical resolution of <1 nm.

RESULTS

Images of the ablated stromal surface showed undulations and granule-like features on the ablated surface of the specimens. The specimens on which the smoothing procedure was performed (root-mean-square [RMS] rough: 0.152 +/- 0.014 microm) were more regular (P < .001) than those on which PRK alone was performed (RMS rough: 0.229 +/- 0.018 microm).

CONCLUSIONS

Atomic force microscopy analysis requires a simpler preparation of the specimens with respect to that necessary for scanning electron microscopy; for this reason, atomic force microscopy techniques are more reliable for the study of biological surfaces and prove to be a feasible method to establish the differences when comparing different laser techniques. Our investigations highlight that although the laser cut of scanning-spot excimer laser systems is precise in removing even the smallest amounts of tissue, the smoothing technique may still be useful to reduce post-ablation roughness.