Refractive changes after excimer laser phototherapeutic keratectomy

Safety and Efficacy of the Phototherapeutic Keratectomy for Treatment of Recurrent Corneal Erosions: A Systematic Review and Meta-Analysis

BACKGROUND

Phototherapeutic keratectomy (PTK) has been increasingly used to treat severe recurrent corneal erosion syndrome (RCES) patients who do not respond to other treatments. However, the efficacy and complication of each study are currently uncertain due to varying rates.

OBJECTIVES

The objective of this study was to investigate the safety and efficacy of the PTK for recurrent corneal erosions.

METHODS

This article performed a systematic literature research in Cochrane, Embase, PubMed, Scopus, and the Web of Science for the literature on PTK treatment of RCES until December 20, 2022. The extracted data including recurrence rate and the adverse event rate were used for meta-analysis.

RESULTS

The recurrence rate was 18% (95% CI, 13%-24%) (129/700 eyes). Subgroup analysis showed that the RCE recurrence was 17% (95% CI, 9%-24%) after trauma and 22% (95% CI, 11%-32%) in the corneal dystrophy group. Treatment-related adverse events included subepithelial haze, hyperopic shift, and decrease of the best spectacle-corrected visual acuity. In this study, the incidence of these events was 13% (95% CI, 6%-21%), 20% (95% CI, 11%-28%), and 11% (95% CI, 5%-16%), respectively.

CONCLUSIONS

PTK represented a valuable treatment option for patients with recurrent corneal erosions, especially those with traumatic injuries, which had minimal side effects.

Sequential Custom Therapeutic Keratectomy for the Treatment of Granular Corneal Dystrophy Type 1: A Long-term Study

PURPOSE

To evaluate the effectiveness of sequential custom phototherapeutic keratectomy (SCTK) for granular corneal dystrophy type 1 (GCD1).

METHODS

Thirty-seven eyes of 21 patients with GCD1 were treated with SCTK to remove superficial opacifications, regularize the corneal surface, and decrease optical aberrations. SCTK is a sequence of custom therapeutic excimer laser keratectomies with step-by-step intraoperative corneal topography monitoring of results. Six eyes of 5 patients previously treated with penetrating keratoplasty received SCTK for disease recurrence. Pre-operative and postoperative corrected distance visual acuity (CDVA), refractive values, mean pupillary keratometry, and pachymetry were retrospectively analyzed. The mean follow-up period was 41.3 months.

RESULTS

SCTK provided significant decimal CDVA improvement, from 0.33 ± 0.22 to 0.63 ± 0.24 (P < .0001) at the last available follow-up visit. One eye, initially treated with penetrating keratoplasty, showed visually significant disease 8 years after the first SCTK and was re-treated. Mean corneal pachymetry difference between preoperative and final follow-up values was 78.42 ± 62.26 µm. Mean corneal curvature and the spherical component did not show a statistically significant change or hyperopic shift. Astigmatism and higher order aberration reduction were statistically significant.

CONCLUSIONS

SCTK is a powerful tool for the treatment of anterior corneal pathologies hindering vision and quality of life, such as GCD1. SCTK is less invasive and fosters more rapid visual recovery than penetrating keratoplasty or deep anterior lamellar keratoplasty. Providing significant visual improvement, SCTK can be the preferred initial treatment in eyes with GCD1. [J Refract Surg. 2023;39(6):422-429.].

Comparison of the Predictive Accuracy of Intraocular Lens Power Calculations after Phototherapeutic Keratectomy in Granular Corneal Dystrophy Type 2

Granular corneal dystrophy type 2 (GCD2) is an autosomal dominant disease affecting vision. Phototherapeutic keratectomy (PTK) is advantageous in removing vision-threatening corneal opacities and postponing keratoplasty; however, it potentially disturbs accurate intraocular lens (IOL) power calculation in cataract surgery. The myopic/hyperopic Haigis-L method with or without the central island has been reported; nevertheless, an optimal method has not yet been established. To compare the predictive accuracy of post-PTK IOL power calculations in GCD2, the retrospective data of 30 eyes from July 2017 to December 2020 were analyzed. All GCD2-affected eyes underwent post-PTK standard cataract surgery using the WaveLight EX500 platform (Alcon Laboratories, Inc., Fort Worth, TX, USA) under a single surgeon. The mean prediction error (MPE) and absolute error (MAE) with the myopic/hyperopic Haigis-L, Barrett Universal II, Barrett True-K, Haigis, and SRK/T by standard keratometry (K) and total keratometry (TK), where possible, were analyzed. Barrett Universal II and SRK/T showed significantly superior MPE, and MAE compared with the myopic/hyperopic Haigis-L method. TK was not significantly superior to K in the same formula. In conclusion, this study suggests that these biometries and formulas, especially Barrett Universal II and SRK/T, are potentially useful in IOL power calculation in GCD2 after PTK.

Hyperopia-Correcting Phototherapeutic Keratectomy and Its Comparison With Conventional Phototherapeutic Keratectomy

Purpose

To evaluate hyperopia-correcting phototherapeutic keratectomy (HC-PTK) and to compare the visual and refractive outcomes of HC-PTK and conventional PTK.

Methods

This study comprised a total of 72 eyes of 72 consecutive patients who underwent HC-PTK and conventional PTK for granular corneal dystrophy or band-shaped keratopathy. Preoperatively and 6 months postoperatively, we assessed visual acuity, manifest refraction, and mean keratometry, as well as postoperative corneal higher-order aberrations and adverse events in each PTK group, and compared these metrics between the two groups.

Results

LogMAR BSCVA significantly improved from 0.43 ± 0.47 preoperatively to 0.21 ± 0.38 postoperatively in the HC-PTK group (Wilcoxon signed-rank test, p < 0.001). It was also significantly improved from 0.22 ± 0.21 preoperatively to 0.15 ± 0.12 postoperatively in the conventional PTK group (p = 0.031). Mean refraction significantly changed from 0.27 ± 1.55 diopter (D) preoperatively to 0.50 ± 1.77 D postoperatively, in the HC-PTK group (p = 0.313). By contrast, it was significantly hyperopic from −0.15 ± 2.41 D preoperatively to 1.45 ± 2.46 D postoperatively, in the conventional PTK group (p < 0.001). No significant complications occurred in any case during the follow-up period.

Conclusion

Both HC-PTK and conventional PTK showed a significant improvement of BSCVA and no vision-threatening complications at any time in this series. HC-PTK significantly reduced a hyperopic shift in refraction compared with conventional PTK, suggesting its viability for patients requiring PTK, especially in consideration of preventing this hyperopic issue.

Phototherapeutic keratectomy: Indications, methods and decision making

Phototherapeutic keratectomy (PTK) involves treating anterior corneal lesions by superficial corneal ablation using an excimer laser (193 nm). Some of the commonly treated conditions include recurrent corneal erosions (RCE), corneal dystrophies, spheroidal degeneration, keratoconus, and corneal scars. We discuss various techniques of PTK including large area PTK, focal PTK, and multifocal PTK and alternatives to PTK. Masking agents like hyaluronate, methylcellulose, and dextran are recommended to help achieve a better outcome when ablating irregular corneal surfaces. Antifibrotic agents like mitomycin C reduce the chances of recurrence of the disease, apart from minimizing the postoperative scarring. Some of the complications include induced hyperopia and irregular astigmatism, haze, recurrence, and corneal thinning. However, earlier postoperative recovery, possibility of a repeat procedure, and ability to control the depth of ablation make PTK a promising, minimally invasive alternative to keratoplasty in cases with anterior corneal pathologies.

Clinical outcomes of simultaneous phototherapeutic keratectomy and photoastigmatic keratectomy

This study was aimed to assess the outcomes of simultaneous phototherapeutic keratectomy (PTK) and photoastigmatic keratectomy (PAK), with special attention to astigmatic correction. We comprised 70 eyes of 70 patients who underwent simultaneous PTK and PAK in patients having granular corneal dystrophy and band keratopathy with refractive astigmatism of 1 diopter (D) or more. Preoperatively and 6 months postoperatively, we assessed corrected uncorrected distance visual acuity (UDVA), distance visual acuity (CDVA), manifest spherical equivalent, refractive astigmatism, corneal astigmatism, and higher-order aberrations (HOAs). LogMAR CDVA significantly improved, from 0.27 ± 0.27 preoperatively, to 0.13 ± 0.21 postoperatively (Paired t test, p < 0.001). LogMAR UDVA also significantly improved, from 0.70 ± 0.32 preoperatively, to 0.57 ± 0.41 postoperatively (p = 0.043). Refractive astigmatism significantly decreased, from 2.12 ± 0.95 D preoperatively, to 0.89 ± 0.81 D postoperatively (p < 0.001). Corneal astigmatism also significantly decreased, from 2.17 ± 0.90 D preoperatively, to 1.08 ± 0.71 D postoperatively (p < 0.001). Corneal HOAs did not significantly change, from 0.54 ± 0.30 µm preoperatively, to 0.48 ± 0.20 µm postoperatively (p = 0.140). No significant complications occurred in any eye. Simultaneous PTK and PAK treatment is effective not only for improving visual acuity, but also for reducing astigmatism.

Fourier-domain optical coherence tomography-guided phototherapeutic keratectomy for the treatment of anterior corneal scarring

AIM

To evaluate the safety, visual and anatomic outcomes of fourier-domain optical coherence tomography (FD-OCT)-guided excimer laser phototherapeutic keratectomy (PTK) combined with photorefractive keratectomy (PRK) surgery in treating anterior corneal scarring.

METHODS

Clinical data of 23 eyes of 21 patients with anterior corneal scarring underwent FD-OCT-guided PTK and PRK from Dec. 2014 to Jul. 2016 were reviewed. Patients were assessed for preoperative and postoperative uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), contrast sensitivity (CS), FD-OCT, corneal topography and colour figures of anterior segments.

RESULTS

The preoperative corneal pathologic conditions included viral keratitis (7 patients, 7 eyes), band keratopathy (2 patients, 4 eyes), corneal dystrophy (4 patients, 4 eyes), traumatic corneal disease (2 patients, 2 eyes) and corneal chemical injury (6 patients, 6 eyes). Mean follow-up time was 10.65 (range, 3-19)mo. UCVA (in logMAR) improved from a mean of 0.79 (95%CI, 0.28-1.29) preoperatively to a mean of 0.45 (95%CI, 0.29-0.62) postoperatively (P=0.021). BSCVA (in logMAR) improved from 0.57 (95%CI, 0.27-0.88) preoperatively to a mean of 0.28 (95%CI, 0.15-0.41) postoperatively (P=0.001). Corneal topographic indices postoperatively showed significant improvement in corneal cylinder (P=0.009), the surface regularity index (P=0.007) and surface asymmetry index (P=0.00). Postoperative spherical equivalent averaged -0.53 diopters (-1.49 to 0.42). No complications were associated with the treatment.

CONCLUSION

FD-OCT-guided PTK combined with PRK is safe and effective for the treatment of anterior corneal scarring by eliminating or reducing corneal opacities.

Myopic outcomes after excimer laser phototherapeutic keratectomy (PTK)

PURPOSE

To evaluate refractive outcomes following excimer laser phototherapeutic keratectomy (PTK).

METHODS

A retrospective non-randomized review of refractive outcomes of 146 consecutive eyes treated with excimer laser PTK at the Rothschild Foundation, Paris, France. Inclusion criteria were all patients undergoing PTK laser using a flying spot excimer laser system (Wavelight Allegretto, Alcon Surgical, Inc.) from October 2016 to June 2018. Exclusion criteria were incomplete data, irregular astigmatism and dystrophies of uncertain diagnosis. Preoperative diagnoses included recurrent corneal erosion syndrome without dystrophy and Cogan corneal dystrophies. The primary outcome measure was the change in spherical equivalent (SEQ) at M1 post PTK. The secondary outcome measure was the creation of a regression equation for predicting refractive outcomes after PTK, by analyzing the effect of ablation depth (AD) and optical zone (OZ) diameter.

RESULTS

Fifty-eight eyes of 54 patients were included. The mean OZ was 7.352 mm±0.622. The mean AD was 18.362μm±21.406. At M1 postoperatively, the mean SEQ was -2.485 D±2.628 and mean final SEQ was -1.052 D±1.260. Both OZ and AD were independent variables with significant effects on the final visual outcome. A regression equation for predicting refractive outcomes was established. No complications were observed.

CONCLUSION

The Wavelight flying spot excimer laser system produces myopic outcomes following PTK. Both OZ and AD are significant variables. A regression equation was created and may aid in prediction of refractive outcomes following PTK.

Transepithelial phototherapeutic keratectomy for the treatment of severe band keratopathy

PURPOSE

The goal of this study was to investigate the clinical outcomes of transepithelial phototherapeutic keratectomy (transepithelial PTK) for the treatment of severe band keratopathy.

METHODS

A consecutive series of severe band keratopathy cases treated with transepithelial PTK were retrospectively analysed between January 2018 and December 2019. Severe band keratopathy was defined as corneal plaques apparent in the obscuration of iris details. Patients' medical histories, preoperative and postoperative symptomatic relief, cosmesis, best-corrected visual acuity (BCVA), complications, and recurrences were analysed.

RESULTS

Seventeen eyes of 16 patients were included in the study, with a mean follow-up of 9.8 ± 5.2 months (3 to 19 months). The mean age of the patients was 15.8 ± 10.2 years (8 to 46 years). Symptoms were significantly or completely relieved in all patients (100%). The results of cosmesis were good in 14 eyes (82.4%). Among those eyes that had BCVA of hand motion or better preoperatively, seven eyes (100%) showed an improvement in BCVA postoperatively. There were no complications or recurrences associated with transepithelial PTK treatment during the follow-up period.

CONCLUSIONS

Transepithelial PTK is an effective treatment to eliminate corneal opacity and alleviate symptoms in patients with severe band keratopathy. This technique could be an alternative approach to managing severe band keratopathy.

Topography-based customized trans-epithelial phototherapeutic keratectomy for anterior corneal scar removal

PURPOSE

To report a case of management of a post-LASIK superficial corneal scar using a novel single-step topography-based customized phototherapeutic keratectomy (PTK).

METHODS

Surgical technique description.

RESULTS

Ablation was planned using Schwind Amaris^® 1050RS excimer laser as decentered trans-epithelial PTK of 5 mm × 3.5 mm of 75 µm depth exactly over the area of the scar. UDVA, CDVA improved from 20/60 and 20/40 pre-operatively to 20/30 and 20/20p post-operatively. Refractive error improved from -2.5 DC @135 to +0.25 DS/-0.25 DC @75. Regularization of topography and stromal surface on ASOCT was noted with minimal hyperopic shift. Another step of ablation to address induced hyperopia was not required.

CONCLUSION

Topography-based customized PTK appears to be an effective novel technique for the management of superficial corneal scars with minimal induced refractive change. This technique holds promise as an alternative in the targeted management of superficial corneal scars, traditionally treated by conventional PTK, without significant ablation of normal tissue.

Predictability of intraocular lens power calculation in eyes after phototherapeutic keratectomy

PURPOSE

To compare the predictability of intraocular lens (IOL) power calculation using several corneal power measurements in eyes that underwent phototherapeutic keratectomy (PTK).

STUDY DESIGN

Retrospective case series.

METHODS

We reviewed the clinical charts of 42 eyes of 25 consecutive patients who underwent cataract surgery after PTK for granular corneal dystrophy or band keratopathy. IOL power calculations were performed using the SRK/T formula with four corneal power measurements [automated keratometry (AK) measured with a partial coherence interferometer, simulated keratometry (Sim K), true net power (TNP), and total corneal refractive power (TCRP) measured with a rotating Scheimpflug camera]; we determined the prediction error, absolute error, and percentage within ± 1.0 D of the targeted refraction, 1 month postoperatively.

RESULTS

The prediction error in the TCRP group was significantly better than those in the AK, Sim K, and TNP groups. The absolute error was also significantly better than those in the AK and Sim K groups, but not significantly different from that in the TNP group. The percentages of within ± 0.5 and 1.0 D in the TCRP group were significantly higher than those in the AK and Sim K groups, but not significantly different from that in the TNP group.

CONCLUSIONS

The TCRP provides the highest predictability of IOL power calculation in post-PTK eyes. This result suggests that the use of the TCRP, rather than of conventional anterior keratometry, may be clinically helpful for improving the refractive accuracy of post-PTK eyes.

Phototherapeutic keratectomy

Phototherapeutic keratectomy is an excimer laser-based surgical procedure widely performed by corneal surgeons for treating anterior corneal stromal pathologies. Phototherapeutic keratectomy helps by ablating the corneal stroma, thereby improving corneal clarity and smoothening the surface. Transient discomfort and induced hyperopia from corneal flattening are the immediate postoperative concerns. The long-term course is often marked by the recurrence of original corneal pathology and corneal haze formation. Phototherapeutic keratectomy, however, allows for repeat stromal ablation for managing recurrences, as the corneal thickness permits, without affecting the outcome of future keratoplasty. Adjunctive methods such as topical mitomycin-C may be additionally used to reduce recurrence rates. Also, various masking agents such as carboxymethyl cellulose, sodium hyaluronate, and dextran are used in eyes with irregular corneal surface to allow for uniform stromal ablation. Overall, phototherapeutic keratectomy has provided corneal surgeons an additional surgical tool, particularly those residing in developing nations where the availability of donor corneal tissue is an important limiting factor.

Comparison of the Accuracy of Newer Intraocular Lens Power Calculation Methods in Eyes That Underwent Previous Phototherapeutic Keratectomy

PURPOSE

To evaluate the accuracy of intraocular lens (IOL) power calculations using ray tracing software in patients who had undergone phototherapeutic keratectomy (PTK).

METHODS

In this retrospective case series, 37 eyes of 22 patients (mean age: 69.4 years; range: 56 to 85 years) who underwent cataract surgery after PTK were reviewed. The prediction error, defined as the difference between the estimated postoperative spherical equivalent and the postoperative manifest refraction at the spectacle plane, was calculated using the following formulas: OKULIX (Tedics, Dortmund, Germany), PhacoOptics (IOL Innovations ApS, Aarhus, Denmark), Barrett True K No History (NH), and Camellin-Calossi. The PhacoOptics formula was used in three different ways: historical method (H), no history method (NH), and C-constant method (C). The median values of the arithmetic and absolute prediction errors among these six IOL calculation methods were compared.

RESULTS

The median arithmetic errors (in diopters [D]) and percentages of eyes within ±0.50 D of the absolute errors were as follows: OKULIX (0.33, range: -2.20 to 2.50, 30.6%), PhacoOptics (H) (-0.12, range: -3.28 to 4.85, 22.2%), PhacoOptics (NH) (-0.25, range: -2.08 to 1.70, 48.4%), PhacoOptics (C) (0.04, range: -1.40 to 2.18, 48.5%), Barrett True K (NH) (-0.35, range: -1.90 to 1.89, 48.6%), and Camellin-Calossi (-0.19, range: -1.78 to 1.47, 59.5%).

CONCLUSIONS

The PhacoOptics, especially the C-constant method (C), and Camellin-Calossi formulas were good options for calculating IOL powers in eyes that underwent PTK. [J Refract Surg. 2019;35(5):310-316.].

Phototherapeutic keratectomy for recurrent granular dystrophy in postpenetrating keratoplasty eyes

Purpose:

The purpose is to assess the clinical and visual outcome after phototherapeutic keratectomy (PTK) procedure in eyes with prior penetrating keratoplasty (PKP) for granular corneal dystrophy (GCD) and the time of performance of repeat PTK for recurrence.

Methods:

PTK was performed for visually significant recurrence: A reduction in best-corrected visual acuity (BCVA) by >2 lines over BCVA before recurrence was considered as visually significant recurrence. Three eyes had amniotic membrane patch performed with PTK. The main outcome measures were a recurrence of GCD, clinical course, and visual outcome. Intervals between repeat PTK procedures were noted.

Results:

Six patients (n = 10 eyes; males: 4, mean age 39 ± 13.97 years) underwent PTK. The mean pachymetry before first PTK was 527.1 ± 34 microns. The mean duration between PKP and first PTK was 85.1 months (range: 37–108 months). Two and three PTK procedures were done for seven and five eyes, respectively. Mean duration between first and second and second and third PTK was 62.12 ± 34.41 and 42.8 ± 13.54 months respectively. The average cut depth was 43.66 ± 19.57, 75 ± 43.30 and 39 ± 19.79 microns after the first, second and third PTK procedures, respectively. All eyes had a corneal haze. Prefirst PTK mean BCVA was 20/200 and improved significantly after the first two PTK procedures to 20/40 and after the third PTK procedure to 20/32 (P < 0.001). Five eyes had hyperopia. One acute graft rejection was managed successfully at 5 months with medical therapy.

Conclusion:

Multiple PTK procedures can be performed safely with improved visual acuity in grafts without compromising graft survival.

Outcomes of photorefractive keratectomy instead of phototherapeutic keratectomy for patients with granular corneal dystrophy type 2

PURPOSE

The purpose of this study was to evaluate visual function and postoperative refractive errors in patients with granular corneal dystrophy type 2 (GCD2) and cataracts who underwent photorefractive keratectomy (PRK) instead of phototherapeutic keratectomy (PTK) following cataract surgery to avoid PTK-induced central island formation and reduce refractive errors after cataract surgery.

METHODS

The medical records of 14 eyes from nine patients (one man and eight women; mean age, 69.0 ± 8.5 years) with GCD2 and cataracts were evaluated. All patients underwent PTK using the PRK mode 3 months after cataract surgery. We analyzed corrected distance visual acuity (CDVA), refractive errors, and corneal astigmatism derived from Fourier analysis and assessed the incidence of complications in cataract surgery and PTK.

RESULTS

The mean CDVA logMAR values were 0.42 ± 0.19, 0.38 ± 0.18, and 0.16 ± 0.12 before and after cataract surgery and after PTK, respectively. CDVA improved significantly after PTK, as compared with both before and after cataract surgery (P < 0.001). The mean absolute errors after cataract surgery and PTK were 0.53 ± 0.43 and 1.61 ± 1.01 diopters, respectively. Pre- and postoperative Fourier indices did not significantly vary in the 3-mm diameter zone, and only the asymmetry component of the 6-mm diameter zone significantly (P <0.01) increased postoperatively. No central island formation and no other marked complications were observed postoperatively in any case.

CONCLUSIONS

Performing PTK using the PRK mode following cataract surgery may be effective for patients with GCD2 and cataracts.

Comparison of the accuracy of intraocular lens power calculations for cataract surgery in eyes after phototherapeutic keratectomy

PURPOSE

To compare the accuracy of several methods of intraocular lens (IOL) power calculations used for cataract surgery in eyes treated with phototherapeutic keratectomy (PTK) that results in changes in the anterior corneal surface and axial length; these results make power calculations less predictable.

METHODS

We evaluated the medical records of 23 eyes of 13 patients (mean age, 68.8 years; range 62-80 years) who underwent cataract surgery after PTK at Keio University Hospital, Tokyo, Japan. The prediction error, defined as the difference between the estimated postoperative spherical equivalent and the postoperative manifest refraction at the spectacle plane, was calculated using five formulas: SRK/T, Haigis-L, Shammas-PL, Camellin-Calossi, and OKULIX ray tracing software. We compared the median values of the arithmetic and absolute prediction errors among the five formulas.

RESULTS

The median arithmetic errors after cataract surgery for the five formulas were 0.70 D (diopter) (range -0.41 to 2.78), -0.96 D (range -2.14 to 0.81), -0.81 D (range -1.89 to 1.15), -0.04 D (range -1.35 to 1.47), and 0.68 D (range -0.61 to 2.50), respectively.

CONCLUSION

The Camellin-Calossi formula is a good option for calculating IOL powers in eyes that underwent PTK.

Efficacy of Hyperopic Photorefractive Keratectomy Simultaneously Performed With Phototherapeutic Keratectomy for Decreasing Hyperopic Shift

PURPOSE

To investigate the efficacy of hyperopic photorefractive keratectomy (HPRK) that was performed simultaneously with phototherapeutic keratectomy (PTK) with regard to decreasing hyperopic shift.

METHODS

A total of 63 eyes of 47 consecutive patients with granular corneal dystrophy (GCD) or band-shaped keratopathy (BSK) underwent PTK or PTK + HPRK. PTK alone was performed in 40 eyes (20 GCD and 20 BSK), and PTK + HPRK was performed in 23 eyes (15 GCD and 8 BSK). All patients underwent examinations including uncorrected distance visual acuity, corrected distance visual acuity, refractometry, and keratometry before and at 1, 3, and 6 months after PTK. Medical charts were reviewed retrospectively.

RESULTS

Superficial corneal opacity was successfully removed from all eyes, and uneventful reepithelialization was completed within 7 days after PTK or PTK + HPRK. The average uncorrected distance visual acuity was significantly better in the PTK + HPRK group than in the PTK group preoperatively and at 1, 3, and 6 months postoperatively. The corrected distance visual acuities were similar in both groups preoperatively and postoperatively. The hyperopic change in the PTK group was approximately 1.5 diopters, and that in the PTK + HPRK group was almost zero. There were significant differences in the average changes of the spherical equivalent from preoperation between the PTK and PTK + HPRK groups at all postoperative time points.

CONCLUSIONS

Simultaneous performance of PTK and HPRK can effectively reduce hyperopic shift after PTK and is as safe as PTK alone. It is recommended that HPRK be added to PTK to treat eyes in which hyperopic shift is undesirable.

Predicting transepithelial phototherapeutic keratectomy outcomes using Fourier domain optical coherence tomography

PURPOSE

The aim of this study was to use Fourier domain optical coherence tomography to predict transepithelial phototherapeutic keratectomy outcomes.

METHODS

This is a prospective case series. Subjects with anterior stromal corneal opacities underwent an excimer laser phototherapeutic keratectomy (PTK) combined with a photorefractive keratectomy using the VISX S4 excimer laser (AMO, Inc, Santa Ana, CA). Preoperative and postoperative Fourier domain optical coherence tomography images were used to develop a simulation algorithm to predict treatment outcomes. Main outcome measures included preoperative and postoperative uncorrected distance visual acuities and corrected distance visual acuity.

RESULTS

Nine eyes of 8 patients were treated. The nominal ablation depth was 75 to 177 μm centrally and 62 to 185 μm peripherally. Measured PTK ablation depths were 20% higher centrally and 26% higher peripherally, compared with those for laser settings. Postoperatively, the mean uncorrected distance visual acuity was 20/41 (range, 20/25-20/80) compared with 20/103 (range, 20/60-20/400) preoperatively. The mean corrected distance visual acuity was 20/29 (range, 20/15-20/60) compared with 20/45 (range, 20/30-20/80) preoperatively. The MRSE was +1.38 ± 2.37 diopters (D) compared with -2.59 ± 2.83 D (mean ± SD). The mean astigmatism magnitude was 1.14 ± 0.83 D compared with 1.40 ± 1.18 D preoperatively. Postoperative MRSE correlated strongly with ablation settings, central and peripheral epithelial thickness (r = 0.99, P < 0.00001). Central islands remained difficult to predict and limited visual outcomes in some cases.

CONCLUSIONS

Optical coherence tomography measurements of opacity depth and 3-dimensional ablation simulation provide valuable guidance in PTK planning. Post-PTK refraction may be predicted with a regression formula that uses epithelial thickness measurements obtained by optical coherence tomography. The laser ablation rates described in this study apply only to the VISX laser.

Optical coherence tomography-guided transepithelial phototherapeutic keratectomy for the treatment of anterior corneal scarring

PURPOSE

To report the visual and anatomic outcomes of a novel technique for the management of anterior corneal scarring using optical coherence tomography (OCT)-guided transepithelial phototherapeutic keratectomy (transepithelial PTK).

DESIGN

Retrospective, consecutive case series.

METHODS

The charts of 22 patients with anterior corneal scarring associated with irregularities in the Bowman layer who had undergone transepithelial PTK according to a novel protocol were reviewed. The protocol consisted of a preoperative OCT-measured depth-of-treatment calculation, followed by a dual excimer laser treatment profile set to achieve the desired refractive outcome while eliminating or reducing corneal scarring. The primary outcomes were change in best spectacle-corrected visual acuity (BSCVA) and change in corneal topography indices at 4 months after ablation.

RESULTS

BSCVA (in logMAR) improved from a mean of 0.82 (0.61-1.02; 95% confidence interval) preoperatively to a mean of 0.40 postoperatively (0.19-0.61) (P = 0.0070). All patients gained a minimum of 1 line of BSCVA postoperatively. Preoperative and postoperative corneal topographic indices showed significant improvement in corneal cylinder (P = 0.0173) and projected visual acuity (P = 0.0261) but not in the surface asymmetry index (P = 0.0849) or the surface regularity index (P = 0.0543). Postoperative spherical equivalent averaged 0.78 diopters (0.49-1.07) of error from the intended target refractive outcome. No complications were associated with the treatment, and no patients required or desired subsequent treatment with either repeat PTK or with more invasive surgery such as lamellar or penetrating keratoplasty.

CONCLUSIONS

OCT-guided transepithelial PTK using a dual ablation excimer laser profile can provide favorable results as well as predictable refractive outcomes in the treatment of corneal scarring associated with Bowman layer irregularities. Future investigations are warranted to further validate the technique reported in this study.

Diamond burr superficial keratectomy with mitomycin C for corneal scarring and high corneal astigmatism after pterygium excision

Background

The purpose of this paper is to report the successful treatment of corneal scarring and high corneal astigmatism secondary to previous pterygium surgery with diamond burr superficial keratectomy using mitomycin C.

Methods

Four patients with corneal scarring and high corneal astigmatism related to previous pterygium surgery underwent diamond burr superficial keratectomy with application of mitomycin C. Anterior segment photography and corneal topographic analysis were obtained preoperatively and postoperatively in all patients.

Results

Six months after surgery, corneal astigmatism and corneal aberrations were reduced in all patients. A clear cornea was achieved in all cases. No complications were noted during the follow-up period.

Conclusion

Diamond burr superficial keratectomy with application of mitomycin C is a potentially effective and simple procedure for treating patients with corneal scarring and high corneal astigmatism secondary to previous pterygium surgery.

Excimer laser phototherapeutic keratectomy in eyes with corneal stromal dystrophies with and without a corneal graft

PURPOSE

To evaluate and compare the visual outcomes and recurrence patterns of corneal stromal dystrophies after excimer laser phototherapeutic keratectomy (PTK) in eyes with and without a corneal graft.

DESIGN

Retrospective, comparative case series.

METHODS

setting: Cornea Service, Wills Eye Institute, Philadelphia Pennsylvania. study population: The patients were divided into 2 groups. Group 1 comprised patients with no graft who underwent PTK (22 eyes of 15 patients), and group 2 comprised patients who underwent PTK over a previous full-thickness graft (18 eyes of 14 patients). intervention: All patients underwent PTK for decreased vision, symptoms of recurrent erosions, or both. main outcome measures: Visual outcomes and recurrence patterns of corneal stromal dystrophies.

RESULTS

Preoperative and postoperative best-corrected visual acuities were 0.46 ± 0.25 and 0.51 ± 0.27 (P = .56), respectively, in group 1 and 0.16 ± 0.13 and 0.21 ± 0.18 (P = .25), respectively, in group 2. Mean preoperative spherical equivalent was 1.54 ± 2.59 diopters (D) and -5.10 ± 5.81 D (P = .01) in groups 1 and 2, respectively, and mean postoperative spherical equivalent was 0.44 ± 1.8 D and -1.8 ± 4.25 D (P = .19) in groups 1 and 2, respectively. There was no statistically significant difference in the efficacy (P = .73) and safety (P = .62) indices between the 2 groups. In group 1, mild recurrence was seen in 7 eyes (32%) and significant recurrence was seen in 4 eyes (18%) at a mean of 32 and 47 months after PTK, respectively. In group 2, mild recurrence was seen in 5 eyes (28%) and significant recurrence was seen in 5 eyes (28%) at a mean of 36 and 50 months after PTK, respectively.

CONCLUSIONS

PTK improved central corneal clarity, alleviated symptoms resulting from recurrent erosions, and improved visual acuity in both groups.

Refractive and topographic errors in topography-guided ablation produced by epithelial compensation predicted by 3D Artemis VHF digital ultrasound stromal and epithelial thickness mapping

PURPOSE

To describe and quantify the errors inherent to topography-guided ablation of irregular corneas due to natural epithelial thickness compensatory remodeling.

METHODS

Artemis very high-frequency (VHF) digital ultrasound scanning (ArcScan Inc) was performed on a cornea that had undergone radial keratotomy with inferior and superior trapezoidal keratotomies, resulting 27 years later in high irregular astigmatism (+6.50 -8.00 × 101) and severe loss of corrected distance visual acuity (CDVA) to 20/50. The epithelial thickness profile was highly irregular, masking a significant proportion of the true stromal irregularity from front corneal surface topography, which would have resulted in significant inaccuracies had a topography-guided ablation been performed. The stromal ablation pattern of a transepithelial phototherapeutic keratectomy (PTK) ablation was modeled, which appeared logically to reduce the areas of abnormal stromal surface elevation and resembled a hyperopic astigmatic ablation of approximately 3.50 diopters of cylinder. Artemis-assisted transepithelial PTK was performed to target the stromal irregularity masked by epithelium.

RESULTS

Artemis-assisted transepithelial PTK induced a refractive change similar to that predicted (+2.24 -3.97 × 120), demonstrating the refractive shift produced by the epithelium. The epithelial thickness profile became relatively regular and CDVA returned to 20/20⁻². Two topography wavefront-guided ablations were performed to correct the remaining topographic irregularity and refractive error, resulting in a near plano refraction, significantly lower higher order aberrations, and CDVA of 20/20⁺².

CONCLUSIONS

A knowledge of stromal surface shape and power shift produced by epithelial thickness profile alterations after corneal surgery has the potential of improving the efficacy and safety of custom corneal ablation.

Intraocular lens power calculations for cataract surgery after phototherapeutic keratectomy in granular corneal dystrophy type 2

PURPOSE

To investigate the predictability of various intraocular lens (IOL) power calculation methods in granular corneal dystrophy type 2 (GCD2) with prior phototherapeutic keratectomy (PTK) and to suggest the more predictable IOL power calculation method.

METHODS

Medical records of 20 eyes from 16 patients with GCD2, all having undergone cataract surgery after PTK, were retrospectively evaluated. Postoperative cataract refractive errors were compared with target diopters (D) using IOL power calculation methods as follows: 1) myopic and 2) hyperopic Haigis-L formula in IOLMaster (Carl Zeiss Meditec); 3) SRK/T formula using 4.5-mm zone Holladay equivalent keratometry readings (EKRs) (single-K Holladay EKRs method); 4) central keratometry power of true net power map in the Pentacam system (Oculus Optikgeräte GmbH); and 5) clinical history, Aramberri double-K, and double-K Holladay EKRs methods. Topographic status of corneal curvature after PTK was evaluated.

RESULTS

Fourteen (70%) of 20 eyes showed central island formation after PTK. When central island was present, the mean absolute error (MAE) using the hyperopic Haigis-L formula was 0.25±0.15 D. When central island was not present, the myopic Haigis-L formula showed MAE of 0.33±0.16 D. When central island formation and IOLMaster keratometry underestimation were present, the hyperopic Haigis-L formula showed the least MAE of 0.26±0.08 D when switching the IOL-Master keratometry values equal to 4.5-mm zone Holladay EKRs.

CONCLUSIONS

In planning for cataract surgery after PTK in GCD2, topographic analysis for central island formation is necessary. With or without central island formation, the hyperopic or myopic Haigis-L formula can be applied. When IOLMaster keratometry shows underestimation, the Haigis-L formula using 4.5-mm zone Holladay EKRs can be considered.

Phototherapeutic keratectomy

Phototherapeutic keratectomy (PTK) is done regularly for anterior corneal diseases such as corneal dystrophies, corneal degenerations, scars, and band-shaped keratopathy. The various indications include both therapeutic and visual. The aim of this article is to discuss the therapeutic indications for PTK, the specific technique pertaining to a specific etiology, the various other procedures like amniotic membrane graft combined with PTK or PTK being done for recurrences in the grafts, and PTK done before cataract surgery when the anterior corneal pathology coexists with the cataract. Post PTK management such as healing of an epithelial defect, use of steroids in the post PTK period, recurrences of primary disease pathology, and infections, will be discussed. Methods of literature search: A Medline search was carried out for articles in the English language, with the keywords, phototherapeutic keratectomy, band-shaped keratopathy, spheroidal degeneration, scars, bullous keratopathy, and corneal dystrophy. The relevant references are mentioned here.

Phototherapeutic keratectomy for the treatment of corneal opacities after epidemic keratoconjunctivitis

PURPOSE

To assess visual results and compare methods of measuring central corneal thickness (CCT) and corneal opacity thickness (COT) in patients with corneal opacities induced by epidemic keratoconjunctivitis (EKC) and treated with phototherapeutic keratectomy (PTK) using low-dose mitomycin C (MMC).

DESIGN

Prospective consecutive case series.

METHODS

Patients with chronic adenoviral corneal opacity underwent transepithelial PTK with MMC 0.002% for 1 minute. The presence of photophobia, the best spectacle-corrected visual acuity (BSCVA), and the contrast sensitivity were evaluated. CCT measurements were obtained with ultrasound pachymeter (US), ultrasound biomicroscopy (UBM), Scheimpflug tomography (Pentacam Oculus), and optical coherence tomography (OCT Visante). COT measurements were obtained with UBM, Pentacam, and OCT.

RESULTS

Thirty-one eyes of 23 patients, comprising 15 women (65.2%) and 8 men (34.8%), mean age 41.8 years, were enrolled in the study. Duration of visual disturbance was 19.1 ± 14 months. The number of patients with photophobia was reduced from 100% to 29% after surgery. BSCVA improved 2 or more lines in 78% of the patients at 12 months. A hyperopic shift of 1.52 ± 0.91 diopters was achieved. Contrast sensitivity improved in both photopic and mesopic conditions. For each of the instruments, the CCT postoperative mean was significantly smaller than the preoperative measurement (P < .0001) and COT values were significantly reduced in comparison to the preoperative values (P < .001).

CONCLUSION

Improvements in photophobia, BSCVA, and contrast sensitivity were observed in patients treated using excimer laser PTK with low-dose MMC for subepithelial infiltrates.

Anterior stromal puncture for treatment of contact lens-intolerant keratoconus patients

Purpose

To report the results and effectiveness of anterior stromal puncture for contact lens-intolerant keratoconus patients with subepithelial fibrotic nodules.

Methods

Nine eyes of nine keratoconus patients who were rigid gas-permeable contact lenses (RGP)-intolerant due to subepithelial nodular scars were included in this study. The nine patients were enrolled in the study between March 2008 and December 2008. After confirming nodular elevation from slit-lamp biomicroscopy, the area where the epithelium of nodular scars had sloughed was punctured by anterior stromal puncture using a 26-gauge needle attached to a 1-ml syringe under slit-lamp biomicroscopy. The RGPs of all patients were refitted around 4 weeks after the puncture.

Results

Five of the nine patients were male, and the average patient age was 29.6 years (SD ± 5.22 years). Mean follow-up time was 13.7 months (SD ± 4.8 months), and the epithelial defect healed in 1.4 days on average. After the puncture, four of nine patients presented with a recurrent erosion of the nodule during follow-up and needed a second puncture. All the patients showed good contact lens tolerance and satisfactory contact lens fit. No complications such as corneal perforation or keratitis developed.

Conclusions

Anterior stromal puncture using a 26-gauge needle can be a successful and effective method to induce corneal epithelium and Bowman’s layer reattachment. It can be used as an outpatient procedure to improve RGP tolerance in patients with keratoconus with elevated subepithelial nodules.

Indications and outcomes of phototherapeutic keratectomy in the developing world

PURPOSE

To analyze the indications and outcomes of phototherapeutic keratectomy (PTK) in the developing world.

METHODS

In this retrospective study, the records of 203 consecutive eyes of 191 patients who had undergone PTK at a tertiary eye care center were evaluated. The parameters assessed were indications of PTK, demographic features, best spectacle-corrected visual acuity (BSCVA), and pachymetry. PTK was done by using a 193-nm Ar-F Excimer laser (Chiron Technolas Keracor 217 C) in a 6-mm optic zone. Patients were followed up for 6 months.

RESULTS

The most common indication of PTK was symptomatic bullous keratopathy (103 eyes). The patients were divided into 2 groups: those with bullous keratopathy (PTK BK) and those with superficial corneal pathologies (PTK CS). In the PTK CS group, the most common indications were Salzmann nodular degeneration (n = 27) and spheroidal degeneration (n = 22). BSCVA improved from 20/222 (0.09) to 20/86 (0.23) in the PTK CS group and 20/384 (0.05) to 20/202 (0.09) in the PTK BK group (P < 0.0001 in both groups). There was a significant decrease in the number of patients with severe symptoms in the PTK-BK (P < 0.0001) and PTK-CS (P = 0.017) groups. The change in BSCVA was significantly related to both pre-PTK BSCVA and pachymetry in PTK-BK.

CONCLUSIONS

PTK is an efficacious treatment modality for symptomatic relief and visual gain in cases with superficial corneal involvement and bullous keratopathy.

Intraocular lens power calculation after phototherapeutic keratectomy: case report and a new method

To report a case of cataract extraction and intraocular lens (IOL) implantation after phototherapeutic keratectomy (PTK). The IOL power was calculated using the single-K and the double-K SRK/T formula, as well as the Haigis formula after modifying the post PTK corneal power using methods described for corneal power measurements after myopic excimer laser treatment (photorefractive keratectomy (PRK) and LASIK). A new method for IOL power calculation after PTK is introduced.

Phototherapeutic Keratectomy in Children

PURPOSE

Children with dense superficial opacities of the cornea are at risk for developing amblyopia. This study evaluated the efficacy of phototherapeutic keratectomy (PTK) in severe cases of anterior stromal scarring.

METHODS

Five eyes of five patients, aged 6 to 8 years, were included. Three children suffered from uveitis-associated band keratopathy, one child had anterior corneal stromal scarring due to viral infection, and one child had anterior basement membrane dystrophy. Phototherapeutic keratectomy was performed under general anesthesia using the 200 Hz ALLEGRETTO excimer laser. Optical treatment zone was 7.0 mm (one eye) and 8.0 mm (four eyes), and ablation depths were between 20 and 100 microm. Postoperative treatment consisted of bandage soft contact lens, topical preservative-free antibiotics, steroids, and artificial tears. Part-time occlusion therapy was continued, as prior to PTK. Because of the small cohort, statistical evaluation was not performed.

RESULTS

Mean follow-up was 23.4 +/- 13.7 months (range: 10 to 41 months). Surgery and postoperative follow-up were uneventful, and no signs of infection or haze were noted. Preoperative best spectacle-corrected visual acuity was 0.4 to 3.0 logMAR (mean: 1.22 +/- 1.07 logMAR). Best spectacle-corrected visual acuity improved in four eyes and stabilized in one eye due to uveitis recurrence (mean 0.64 +/- 0.65 logMAR). Mean preoperative keratometric values changed from 45.60 +/- 0.90 to 44.90 +/- 3.00 diopters postoperatively.

CONCLUSIONS

Dense superficial corneal opacity in children may be successfully treated with PTK. Phototherapeutic keratectomy was performed to increase corneal transparency and corneal surface smoothing thereby avoiding amblyopia.

Combined Artemis very high-frequency digital ultrasound-assisted transepithelial phototherapeutic keratectomy and wavefront-guided treatment following multiple corneal refractive procedures

We present a patient with severe visual symptoms following multiple corneal refractive procedures including automated lamellar keratoplasty, arcuate keratotomy, laser in situ keratomileusis (LASIK), LASIK enhancement by cutting another flap, followed by a further LASIK enhancement by flap lifting. Topography was irregularly irregular, and the best spectacle-corrected visual acuity (BSCVA) was 20/25. Artemis very high-frequency digital ultrasound (US) analysis of the anatomical irregularities of the epithelium and stroma was used in conjunction with the topography to determine the cause of the visual symptoms. Very high-frequency digital US-assisted transepithelial phototherapeutic keratectomy together with a wavefront-guided treatment was used to reduce the stromal surface irregularities and the higher-order aberrations (HOAs), respectively. The treatment successfully regularized the stromal surface, dramatically reduced the HOAs, improved the contrast sensitivity to the high normal range, and improved the BSCVA to 20/20.

Excimer Laser Phototherapeutic Keratectomy

Anterior corneal pathology, such as corneal scars and corneal stromal dystrophies, can be visually devastating. Over the past decade, there was a shift in treatment of these conditions from corneal transplantation to phototherapeutic keratectomy (PTK) using the 193 nm excimer laser for visual restoration. We have reviewed the recent literature on techniques for performing and refining PTK and also on various pathologic conditions that can be treated with PTK. The primary indications for PTK include anterior corneal dystrophies, such as lattice, granular, and Reis-Bückler's dystrophy. PTK can produce significant visual improvement in these patients, and corneal transplantation or retransplantation can be delayed. Corneal degenerations, such as Salzmann's nodular degeneration, keratoconus nodules, and climatic droplet keratopathy, also can be successfully treated with PTK. Additionally, anterior corneal scars from such etiologies as trauma, corneal ulcers, and prior refractive surgery can have visual improvement with PTK. In summary, PTK is a powerful tool for the management of anterior corneal pathology. In a properly selected and well-counseled patient, PTK can significantly improve vision and quality of life.

Correlations Between Central and Peripheral Changes in Anterior Corneal Topography After Myopic LASIK and Their Implications in Postsurgical Contact Lens Fitting

PURPOSE

To investigate the changes in central and peripheral anterior corneal curvatures after myopic laser in situ keratomileusis (LASIK) and to correlate them with the manifest refractive change to discuss how such results could affect post-LASIK corneal topography profiles and midterm stability and their implications in postsurgical contact lens fitting.

METHODS

Topographic and refractive data from 18 eyes of 11 patients that had undergone myopic LASIK were collected for 6 months after surgery. Short-term and midterm topographic responses were investigated and correlated with spherical equivalent manifest refractive changes.

RESULTS

There was a strong correlation between eccentricity changes and manifest refractive change 15 days after surgery (r = 0.753, P < 0.001), with no significant changes thereafter for the following 6 months (r = 0.148, P = 0.114). A strong linear relationship was found between baseline manifest refraction and changes in corneal curvature at the center (r = 0.810, P < 0.001), 4-mm chord (r = 0.895, P < 0.001), and 6-mm chord (r = 0.696, P < 0.001). Statistically significant changes were also found after the first 15 days (P < 0.005) and showed a regression effect that affects the three zones. In this case, a weaker relationship was found between curvature regression and the final refractive change for the central location (r = 0.412, P = 0.004), 4-mm chord area (r = 0.430, P = 0.003), and 6-mm chord area (r = 0.283, P = 0.023). CONCLUSIONS.: After myopic LASIK, the anterior corneal dioptric power is expected to change, on average, approximately 77% of the attempted spherical equivalent correction at the center; 60% at the 4-mm chord region, where the stronger correlation between topographic and refractive change is found; and 30% at the 6-mm chord area. The paracentral area 4 mm from the center seems to be more likely to predict baseline corneal curvature from manifest refractive change. Some degree of regression in the midterm period is expected to occur after myopic LASIK, which shows a significant correlation with the manifest refractive change. Again, this effect is more evident and more accurately predicted at the 4-mm chord area. The results of the current study are of interest for those fitting contact lenses after myopic LASIK.

Phototherapeutische Keratektomie (PTK)

The conceptual advantage of phototherapeutic keratectomy (PTK) include the option to remove diseased tissue on a micrometer scale. Although less invasive than other forms of corneal surgery, it remains a surgical procedure which carries inherent risks. In phototherapeutic indications this risk is higher than in otherwise healthy eyes undergoing photorefractive surgery. Potential general complications include wound-healing problems, infection, inflammation, or a recurrence of the underlying disease. More specifically, PTK is associated with unwanted refractive changes, such as a hyperopic shift or an irregular astigmatism. In this review, we discuss these problems along with prevention and treatment strategies in detail.