Collagen cross-linking (CCL) with sequential topography-guided PRK: a temporizing alternative for keratoconus to penetrating keratoplasty

Merging Photorefractive Keratectomy and Collagen Crosslinking: An Analysis of Literature and a Guide to Prevalent Protocols

PURPOSE

The purpose of this review was to summarize the different surgical approaches combining photorefractive keratectomy (PRK) and corneal crosslinking (CXL), present each protocol template in a simple format, and provide an overview of the primary outcomes and adverse events.

METHODS

A literature review was conducted as outlined by the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Eight different databases were searched. Papers were included if PRK was immediately followed by CXL.

RESULTS

Thirty-seven papers met the inclusion criteria of a total yield of 823. The latest research into simultaneous PRK and CXL has been shown to not only stabilize the cornea and prevent keratoconus progression but also improve the visual acuity of the patient. Improvements in uncorrected distance visual acuity and (spectacle) corrected distance visual acuity were found to be significant when considering all protocols. There were also significant reductions in K1, K2, mean K, Kmax, sphere, cylinder, and spherical equivalent. Random-effects analysis confirmed these trends. Corrected distance visual acuity was found to improve by an average of 0.18 ± 1.49 logMAR (Cohen's D [CD] 0.12; P <0.02). There was also a significant reduction of 2.57 ± 0.45 D (CD 5.74; P <0.001) in Kmax. Cylinder and spherical equivalent were also reduced by 1.36 ± 0.26 D (CD 5.25; P <0.001) and 2.61 ± 0.38 D (CD 6.73; P <0.001), respectively.

CONCLUSIONS

Combining the 2 procedures appears to be of net benefit, showing stabilization and improvement of ectatic disease, while also providing modest gains in visual acuity. Since customized PRK and CXL approaches appear superior, a combination of these would likely be best for patients.

Topography-guided photorefractive keratectomy combined with accelerated corneal collagen cross-linking versus cross-linking alone for progressive keratoconus: a long-term prospective cohort study

Purpose

To comprehensively compare the long-term outcome of the combined topography guided photorefractive keratectomy (TG-PRK) with accelerated corneal cross-linking (ACXL) and ACXL alone in eyes with progressive keratoconus. The analysis focused on the changes in the detailed corneal aberrometric values.

Methods

This single-center, prospective cohort study included 28 patients (30 eyes) of the TG-PRK plus ACXL group and 14 patients (15 eyes) of the ACXL alone group. The mean duration of the follow-up was 44 ± 10.18 months (ranged from 31 to 65 months). The preoperative data and the postoperative measurement data at the last follow-up visit, including demographic data, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, corneal topography, pachymetry, aberrometry and densitometry were analyzed.

Results

The CDVA significantly improved in the TG-PRK plus ACXL group at the last follow-up visit (p = 0.006), while no significant improvement was found in the ACXL alone group (p = 0.432). The maximal keratometry of the anterior corneal surface (Kmax) of both groups significantly decreased at the last follow-up visit (p < 0.05). Compared with the ACXL alone group, the Kmax of the TG-PRK plus ACXL group showed a greater decline (p = 0.008). The total corneal aberrations, the corneal lower-order aberrations (LOAs), the corneal higher order aberrations (HOAs), the vertical coma and the spherical aberration (SA) at the 4.0 mm and 6.0 mm zone of the TG-PRK plus ACXL group significantly decreased at the last follow-up visit (all p < 0.05). The declines of the total corneal aberrations, the corneal LOAs, the corneal HOAs and the vertical coma at the 4.0 mm and 6.0 mm zone of the TG-PRK plus ACXL group were significantly higher than those in the ACXL alone group (p < 0.001).

Conclusion

Compared with ACXL alone, combined TG-PRK with ACXL procedure had a significantly higher reduction in the corneal HOAs and better CDVA, while providing a similar long-term stability and safety. For progressive keratoconus patients with adequate corneal thickness, the combined procedure might be a recommended treatment option.

Combined topography-guided photorefractive keratectomy and corneal collagen crosslinking

PURPOSE

This study aimed to report the long-term results of combined topography-guided photorefractive keratectomy (PRK) and accelerated corneal collagen cross-linking (CXL) for keratoconus using the Zeiss refractive coordinated system.

METHODS

A prospective interventional study was conducted in a tertiary eye care hospital in South India. Patients with mild-to-moderate progressive keratoconus and corneal pachymetry greater than 450 µm were included. They underwent customized topography-guided PRK followed by CXL. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), and keratometry readings and complications were evaluated at 1, 3, 6, 12, and 24 months postoperatively.

RESULTS

Thirty patients (30 eyes) were included in the study. All study parameters showed a statistically significant improvement postoperatively over baseline values. At 24 months, the mean UDVA improved from 0.8 ± 0.180 logarithm of the minimum angle of resolution (logMAR) to 0.38 ± 0.118 logMAR ( P -value <0.001) and CDVA improved from 0.467 ± 0.142 logMAR to 0.227 ± 0.078 logMAR ( P -value <0.001). The mean flat, steep, and maximum keratometry values were significantly reduced by 2.133, 3, and 4.54 diopters, respectively, at the last follow-up examination ( P -value <0.001).

CONCLUSION

The combined topography-guided PRK and accelerated CXL procedure seem to be a promising treatment alternative for early keratoconus. This is the first such study on the Zeiss refractive coordinated system. However, further studies with a larger study population and longer follow-up periods are required to draw final conclusions about the benefits of this procedure in keratoconus.

Comparison of long-term outcomes of simultaneous accelerated corneal crosslinking combined with intracorneal ring segment or topography-guided PRK

PURPOSE

To compare long-term outcomes of simultaneous accelerated corneal crosslinking (CXL) with intrastromal corneal ring segments (CXL-ICRS) with simultaneous accelerated CXL with topography-guided photorefractive keratectomy (CXL-TG-PRK) in progressive keratoconus (KC).

SETTING

Kensington Eye Institute and Bochner Eye Institute, Toronto, Canada.

DESIGN

Prospective nonrandomized interventional study.

METHODS

The change in visual and topographical outcomes of CXL-ICRS and CXL-TG-PRK 4 to 5 years postoperatively were compared using linear regression models adjusted for preoperative corrected distance visual acuity (CDVA) and maximum keratometry (Kmax).

RESULTS

57 eyes of 43 patients with progressive KC who underwent simultaneous accelerated (9 mW/cm 2 , 10 minutes) CXL-ICRS (n = 32) and CXL-TG-PRK (n = 25) were included. Mean follow-up duration was 51.28 (9.58) and 54.57 (5.81) months for the CXL-ICRS and CXL-TG-PRK groups, respectively. Initial mean Kmax was higher in the CXL-ICRS group compared with the CXL-TG-PRK group (60.68 ± 6.81 diopters [D] vs 57.15 ± 4.19 D, P = .02). At the last follow-up, change (improvement) in logMAR uncorrected distance visual acuity (UDVA) compared with that preoperatively was significant with CXL-ICRS (-0.31 ± 0.27, P < .001, which is equivalent to approximately 3 lines) and not significant with CXL-TG-PRK (-0.06 ± 0.42, P = .43). The logMAR CDVA improved significantly with CXL-ICRS (-0.22 ± 0.20, P < .001), but not with CXL-TG-PRK (-0.05 ± 0.22, P = .25). Adjusting for baseline Kmax and CDVA, the improvement in UDVA was significantly greater with CXL-ICRS than with CXL-TG-PRK (-0.27, 95% CI, 0.06-0.47, P = .01). Improvement in CDVA was not significantly different.

CONCLUSIONS

In this cohort of progressive KC with long-term follow-up, UDVA showed more improvement with accelerated CXL-ICRS than with CXL-TG-PRK.

Ray-Tracing Transepithelial Excimer Laser Central Corneal Remodeling Plus Pachymetry-Guided Accelerated Corneal Crosslinking for Keratoconus

PURPOSE

The aim of this study was to report the 12 to 96 months results of a tissue-preservation algorithm based on ray-tracing-guided transepithelial excimer laser central corneal ablation (RT t-PRK) combined with individualized pachymetry-guided accelerated crosslinking (M nomogram ACXL) in young adult patients with stable keratoconus (KC).

METHODS

This was a prospective interventional study including 38 eyes of 38 young adult patients (stage II KC) with a mean age of 35 years (range 26-46 years) who underwent simultaneous RT with t-PRK plus pachymetry-based ACXL in the worst eye. The treatments were performed using the iViS Suite iRES Excimer Laser (Ligi, Taranto, Italy). Ray-tracing-guided treatments were planned using the customized interactive programmed transepithelial ablation (CIPTA) 2 web software and diagnostic data were assessed by the Precisio 2 tomographer (Ligi, Taranto, Italy) and Sirius tomographer (C.S.O., Florence, Italy). The main outcome measures included uncorrected distance visual acuity, best spectacle-corrected visual acuity, Kmax, high-order aberrations, minimum corneal thickness, and posterior elevation, with a mean follow-up of 52 months (range 12-96 m).

RESULTS

The mean UDVA improved + 3.5 ±1.28 Snellen lines (SL); 38% gained ≥ 4 ±1.34 SLs, 35% ≥ 3 ±1.21 SLs, 22% ≥ 2 ±1.12 SLs, and 5% ≥ 1 ±0.75 SLs. The mean best spectacle-corrected visual acuity increased by + 4.3 ±1.3 SL. Sixty-eight percent gained ≥ 4 ±0.88 SLs and 30% ≥ 3 ±0.78 SL. No SLs were lost.

CONCLUSIONS

RT t-PRK plus ACXL significantly improved the quality of vision in patients with KC, preventing overcorrection and minimizing tissue consumption.

Application of a Revised Tissue Saving Protocol for Combined Topography-Guided Photorefractive Keratectomy and Cross-Linking in a Cohort Having Pellucid Marginal Degeneration

Purpose

To evaluate the efficiency, safety, and stability of a revised tissue-saving treatment protocol in a cohort having pellucid marginal degeneration (PMD).

Methods

A retrospective cohort study was conducted on patients with PMD and no previous treatments. A revised protocol of topo-guided photorefractive keratectomy to be followed by customized phototherapeutic keratectomy and then corneal crosslinking was evaluated by comparing the pre and postoperative outcomes regarding visual (subjective refraction) and topographic (using data from Sirius CSO topography software) outcomes.

Results

There were both statistically significant and clinically relevant improvements in the postoperative parameters, where each of the unaided and corrected visual acuity, spherical equivalent, refractive cylinder, K readings, topographic cylinder, inferior minus superior difference at the 2- and 4- mm diameters, coma aberration, and higher order aberrations were significantly better postoperatively (all p values were less than 0.01, except for maximum k readings where the p-value was 0.017). The safety and efficacy indices for the surgical procedure were remarkably high (1.53 ± 0.70 and 0.90 ± 0.32, respectively).

Conclusion

Our proposed tissue-saving protocol (which showed satisfactory results in keratoconus cases according to a previously published article by our research team) has proven its successful outcomes (both topographically and visually) in cases of PMD, which is a rare ectatic entity with guarded prognosis using the available conventional ectasia treatment modalities.

A comprehensive review on corneal crosslinking

Corneal crosslinking (CXL) represents a paradigm shift in the management of corneal ectatic disorders. Before CXL was introduced, patients would need specialty contact lenses and possible corneal transplantation. CXL involves a biochemical reaction in which ultraviolet A light is used in conjunction with Riboflavin to form crosslinks in between corneal stromal collagen. This leads to strengthening and stabilizing of the collagen lamellae, resulting in mechanical stiffening of the cornea. Multiple protocols have been proposed including epithelium on versus off and varying light intensity and duration of treatment. All protocols appear to be safe and effective with few reported complications including infection, stromal haze, scarring, and endothelial toxicity. Overall, CXL has demonstrated to halt the progression of the disease clinically and in keratometry readings and improve the quality of life for patients. It is a minimally invasive, cost-effective procedure that can be performed in an outpatient setting with a fast recovery time and long-lasting results.

Refractive surgical correction and treatment of keratoconus

Keratoconus is an ectatic corneal disorder that causes severe vision loss. Surgical options allow us to correct, partially or totally, the induced refractive error. Intracorneal ring segments (ICRS) implantation represents a minimally invasive surgical option that improves visual acuity, with a high success rate and a low overall complication rate. Corneal allogenic ICRS consists of ring segments derived from allogenic eye bank-processed donor corneas. Selective topography-guided transepithelial photorefractive or phototherapeutic keratectomy combined with CXL is another way in selected cases to improve spectacles corrected distance visual acuity. The microphotoablative remodeling of the central corneal profile is generally planned by optimizing the optical zones and minimizing tissue consumption. Phakic intraocular lens (PIOL) implant is considered in patients with stable disease and acceptable anatomical requirements. The two types of pIOLs, depending on their implantation inside the eye, are anterior chamber-pIOLs, which fixate to the anterior surface of the iris by using a polymethomethacrolate claw at the two haptics, and posterior chamber-pIOLs. In patients with both cataracts and keratoconus, the correct IOL power is difficult to obtain due to the irregular corneal shape and K values. Toric IOL is recommended, but carefully judging the topography and the possible need of subsequent keratoplasties.

Less Complex Contact Lens Required for a Patient With Keratoconus After Topography-Guided Photorefractive Keratectomy

ABSTRACT

In this report, we discuss contact lens (CL) fitting in a patient with a history of keratoconus (KC), before and after undergoing topography-guided photorefractive keratectomy (TG PRK). Before TG PRK, the patient failed multiple CL modalities and reported difficulty with his habitual CLs and inadequate spectacle-corrected visual acuity to perform his activities of daily living. In this case, a collaborative, comprehensive approach to visual management in a patient with KC was used, and after TG PRK was performed to improve his corneal contour and symmetry, our patient was fit with a standard soft CL and additionally had improved spectacle-corrected visual acuity.

Combined Photorefractive Keratectomy and Corneal Cross-Linking for Keratoconus and Ectasia: The Athens Protocol

ABSTRACT

Customized photorefractive keratectomy with minimal tissue ablation combined with corneal cross-linking seems to be a long-term safe and effective strategy for anatomical and visual management of keratoconus, postsurgical ectasia, and other ectasia management. Multiple published studies, many with long-term follow-up, have supported the Athens Protocol and its various forms as a means to manage corneal ectatic disorders, which not only stabilize corneal shapes but also improve functional vision.

Outcomes of topography-guided PRK/CXL in keratoconus using the NIDEK CXIII system-"Bharat Protocol" (Pilot study)

Purpose

Outcome of topography-guided excimer laser ablation in conjunction with accelerated, high-fluence cross-linking in corneal ecstatic disease using the NIDEK CXIII equipped with CATz algorithm from the FinalFit software-"Bharat Protocol."

Methods

Retrospective case record review of 30 eyes of 17 patients of stage 1-3 keratoconus who underwent the procedure was performed. Data collected were for visual acuity, distortion-induced eye pain, and keratometry. Pachymetry, lower order and higher order aberrations, spherical aberrations, and topographic cylinder were documented from by Scheimpflug imaging (Pentacam 70700: Oculus, Wetzlar, Germany).

Results

At a minimum follow-up of 6 months (range 6.2-13 months), there was significant improvement in UCVA (P < 0.00001), BCVA (P = 0.0061), decrease in Kmax (P = 0.0349), Ksteep (P < 0.0411), Kflat (P = 0.0099), and pachymetry (P = 0.0001). Significant improvement was also seen in distortion-induced eye pain (27/30 to 2/30; P < 0.00001). A more than two-line improvement in UCVA and BCVA was seen in 23/30 and 17/30 cases, respectively. Ectasia was stabilized in all cases at the last follow-up, and no complications were seen.

Conclusions

The "Bharat" Protocol to arrest keratectasia progression and improve corneal regularity is a safe and efficacious alternative as a keratoconus management option. This is the first such study on Nidek Platform for the same.

Ten-year follow-up of corneal cross-linking and refractive surface ablation in patients with asymmetric corneal topography

Purpose

Compare the safety and efficacy of wavefront-guided photorefractive keratotomy (PRK) 6 months after cross-linking (CXL) to wavefront-guided PRK alone for refractive correction in patients with bilateral asymmetric corneal topography.

Methods

Prospective randomized clinical trial with 16 patients (32 eyes). CXL with subsequent PRK after 6 months in one eye, and PRK alone was performed in contralateral eyes. The follow-up was 10 years. We analyzed visual outcomes, Scheimpflug topography, and corneal haze evaluation.

Results

Eyes in the PRK group showed better results than in the CXL + PRK group. Mean postoperative CDVA was 0.044 logmar (SD, 0.073) in the PRK group and 0.1 logmar (SD, 0.21) in the CXL + PRK group, the mean sphere was + 0.21 (SD, 0.6) D in the PRK group and 0.87 (SD, 2.3) D in the CXL + PRK group, and mean SE was -0.35 (SD, 0.65) D in the PRK group and 0.62 (SD, 2.32) D in the CXL + PRK group. In one patient, a steepening of 2.5 D and a thinning of 17 μm occurred in PRK alone group. Two patients in the CXL + PRK group presented corneal haze. The overall complication rate was 18,75% (haze and ectasia).

Conclusion

Non-simultaneous CXL and PRK procedures yielded good refractive results, but worse than those obtained with PRK alone. Although one patient in the PRK group developed corneal ectasia, the CXL + PRK group had a higher loss of vision lines, indicating less safety.

The Keratectasia Volume (KEV) in Corneal Topography to Evaluate the Effect of Corneal Collagen Cross-linking in Pediatric Keratoconus

The study aimed to evaluate the keratectasia volume (KEV) before and after corneal cross-linking (CXL) in pediatric patients. This study included 40 eyes of 25 pediatric patients (10-19 years) undergoing standard CXL. The support vector machine (SVM) algorithm was applied to transform mass pixels in corneal topography into a three-dimensioned model to calculate the KEV. The KEV, Kmax, K1, K2, Kave, keratectasia area (KEA), and thinnest corneal thickness (TCT) were determined before CXL and at 3, 6, and 12 months after surgery. The correlation between KEV and other parameters (Kmax, TCT, max decentration, eccentricity, and so on) was calculated. The KEV was 4.75 ± 0.74 preoperatively and 4.43 ± 1.22 postoperatively at last follow-up (p < 0.002). There was strong positive correlation between the KEV and Kmax (r = 0.806, p < 0.0005). The preoperat ive KEV was 4.32 ± 0.69 in mild to moderate keratoconus (Kmax < 58D) and 5.27 ± 0.37 in advanced keratoconus (Kmax > 58D) (p < 0.0005, t-test). Postoperative KEV and K readings remained stable at the early stage, and the KEV showed a more drastic decreasing trend than Kmax at sixth month. Statistical significance was found in the KEV between preoperative and 6 months after surgery (p < 0.0005), but not in Kmax and other parameters. In 83.3% (15 eyes out of 18 eyes) of the eyes, the preoperative KEV was greater than 4.6 in patients with significant flattening after CXL. Compared with K readings, the KEV can be regarded as a more sensitive index to evaluate the postoperative morphological changes after CXL in pediatric patients.

Introducing a Revised Tissue Saving Protocol for Combined Topography-Guided Photorefractive Keratectomy and Cross-Linking in Keratoconic Corneas

PURPOSE

The aim of this study was to introduce a revised tissue-saving technique for combined topography-guided photorefractive keratectomy (PRK) and cross-linking for keratoconus (KC) treatment and to evaluate its efficacy, safety, and stability.

METHODS

This retrospective, noncontrolled study was performed at Maadi Eye Subspecialty Center and Eye Care Center, Cairo, Egypt. The technique was performed on virgin keratoconic corneas with 3 different morphological patterns of ectasia. It involves performing topography-guided PRK before epithelial removal, followed by customized phototherapeutic keratectomy (PTK) that is tailored to each cornea after studying the treatment profile on the laser treatment screen. The electronic medical records were explored for preoperative and postoperative data, including subjective refraction and topographic data (using Sirius topographer).

RESULTS

The study was conducted on 123 eyes of 93 patients with a mean age of 27.98 years ±6.06. The follow-up ranged from 6 to 36 months (mean ± SD of 16.2 months ±10.4). The results showed statistically nonsignificant differences among the 3 ectasia subgroups in treatment spherical equivalent, treatment maximum depth, thickness of removed epithelium, and thinnest residual stromal bed. There were statistically significant differences in almost all values between the preoperative and postoperative data, with significant postoperative patients' improvement ( P value <0.001). The subgroups' results were almost the same as the whole cohort's results. The safety and efficacy indices of the performed procedure showed remarkably high values (1.48 ± 0.21 and 0.87 ± 0.40, respectively).

CONCLUSIONS

This revised protocol for KC management maximally preserves stromal tissue with proven efficacy, safety, and stability.

Independent-effect comparison of five crosslinking procedures for Progressive Keratoconus based on Keratometry and the ABCD Grading System using Generalized Estimating Equations (GEE)

PURPOSE

Corneal collagen crosslinking (CXL) is an effective treatment for progressive keratoconus. Multiple CXL modalities are clinically available. The present study compared the 1 year outcomes of five types of CXL procedures for progressive keratoconus in a Chinese population using generalized estimating equations (GEE).

METHODS

This retrospective study included 239 eyes in 171 patients with keratoconus who underwent CXL and were followed up for 1 year. Five CXL procedures were assessed, including Accelerated Transepithelial CXL, Iontophoresis CXL for 10 min, CXL plus phototherapeutic keratectomy (CXL-plus-PTK), High-Fluence Accelerated CXL, and Accelerated CXL. Patients treated with the Accelerated CXL procedure represented the reference group. Primary outcomes were visual acuity change, spherical equivalence, endothelial cell density, mean keratometry (K_mean), maximum keratometry (K_max), minimum corneal thickness (MCT), and the ABCD Grading System, consisting of A (staging index for ARC; ARC = anterior radius of curvature), B (staging index for PRC, PRC = posterior radius of curvature), and C (staging index for MCT) values 1 year postoperatively compared to baseline. Secondary outcomes were corrected GEE comparisons from each procedure versus the Accelerated CXL group.

RESULTS

The Accelerated Transepithelial CXL group had lower performance than the Accelerated CXL group according to K_mean and K_max. The CXL-plus-PTK group performed significantly better than the reference group as reflected by K_max (β = -0.935, P = 0.03). However, the CXL-plus-PTK group did not perform as well for B and C, and the Iontophoresis CXL group performed better for C.

CONCLUSIONS

The CXL-plus-PTK procedure was more effective than the Accelerated CXL procedure based on K_max, and the Iontophoresis CXL procedure performed better on the C value based on the ABCD Grading System.

Clinical Outcomes Comparison of Combined Small Incision Lenticule Extraction with Collagen Cross-Linking Versus Small Incision Lenticule Extraction Only

Purpose

To evaluate clinical outcome during 24 months follow-up between small incision lenticule extraction combined with cross-linking (SMILE Xtra) and small incision lenticule extraction (SMILE) only. Setting. Ophthalmology Division of San Rossore Medical Center, Pisa, Italy.

Design

Retrospective comparative case series.

Methods

The study comprised 70 eyes (35 patients); 40 eyes were corrected using SMILE and 30 eyes were corrected using SMILE Xtra using a low energy protocol. The outcomes were compared at 1, 6, 12, and 24 months postoperatively.

Results

The mean spherical equivalent (SEQ) reduced from −7.18 ± 1.21 D to −0.01 ± 0.09 D in the SMILE group and from −6.20 ± 2.99 D to −0.04 ± 0.1 D postoperatively in SMILE Xtra (p < 0.05). At 24 months the mean SEQs were −0.01 ± 0.24 D for SMILE and −0.15 ± 0.33 D for SMILE Xtra (p > 0.05). At 1, 6, 12, and 24 months, there were no statistically significant differences between the SMILE and SMILE Xtra groups in logarithm of the minimum angle of resolution (logMAR) uncorrected distance visual acuity (UDVA), safety, and efficacy index (p > 0.05). The mean average keratometry (K-avg) at 1, 6, 12, and 24 months after surgery did not shown any statistically significant difference between SMILE and SMILE Xtra group (p > 0.05). The mean maximum keratometry (K-max) readings at 1, 6, 12, and 24 months were not statistically significant between SMILE and SMILE Xtra group (p > 0.05). The preoperative mean thinnest point pachymetry (TTP) was 543.90 ± 22.85 μm in the SMILE group and 523.40 ± 37.01 μm in the SMILE Xtra group (p < 0.05). At 1, 6, 12, and 24 months the mean TTP was not statistically significant between the SMILE and SMILE Xtra groups (p > 0.05). At 24 months, the TTP was 408.29 ± 38.75 μm for the SMILE group and 402.22 ± 37 μm for the SMILE Xtra group (p > 0.05). In the preoperative period, the mean maximum posterior elevation (MPE) was 8.63 ± 4.35 μm for SMILE and 8.13 ± 2.54 μm for SMILE Xtra (p > 0.05). After the surgical procedure, both groups showed a statistically significant increase of the MPE (p < 0.05). At 24 months, the MPE was 11.00 ± 4.72 μm for SMILE Xtra and 10.14 ± 3.85 μm for the SMILE group (p > 0.05). In the preoperative period, the means of the root mean square (RMS) of high-order aberration (HOA) were 0.08 ± 0.03 μm for the SMILE group and 0.08 ± 0.03 μm for the SMILE Xtra group (p > 0.05). At 24 months, the RMS of HOA was 0.13 ± 0.07 μm for the SMILE group and 0.14 ± 0.07 μm for the SMILE Xtra group (p > 0.05). In the preoperative period, the root mean square of coma aberration (RMS-Coma) aberration was 0.06 ± 0.09 μm for the SMILE group and 0.04 ± 0.03 μm for the SMILE Xtra group (p > 0.05). At 24 months, the coma aberration of SMILE group was 0.12 ± 0.21 μm and 0.16 ± 0.25 μm for SMILE Xtra group (p > 0.05).

Conclusions

SMILE Xtra procedure is a safe and simple procedure that can be offered to patients with high corneal ectasia risk because there were no differences in the indices of ectasia compared to the group treated only with SMILE which has a low corneal ectatic risk.

Combined photorefractive keratectomy and corneal collagen cross-linking for treatment of keratoconus: a 2-year follow-up study

Background:

Corneal collagen cross-linking (CXL) is considered an effective procedure for slowing down or eliminating the progression of keratoconus. New techniques, in combination with CXL, have been proposed to stop the evolution of keratoconus and improve the visual function.

Objective:

To evaluate the effectiveness of combined photorefractive keratectomy (PRK) with mitomycin-C (MMC) application and CXL in the management of grade 1–2 keratoconus over a 2-year follow-up.

Methods:

Fifteen eyes underwent topography-guided PRK with 0.02% MMC application immediately followed by standard CXL.

Results:

Best corrected visual acuity improved from 0.15 ± 0.11 logMAR to 0.08 ± 0.09 logMAR at 24 months (p < 0.0001) in treated eyes. Mean steepest meridian keratometry reduced from 48.79 ± 3.22 D at baseline to 46.16 ± 3.11 D at 24 months (p < 0.0001). Mean flattest meridian keratometry reduced from 45.18 ± 2.17 D preoperatively to 44.35 ± 2.19 D at 24 months (p < 0.0001).

Conclusion:

Simultaneous topography-guided PRK with MMC 0.02% application and standard CXL is a safe, promising and effective procedure in the treatment of mild and moderate keratoconus.

Keratoconus Management With Customized Photorefractive Keratectomy by Artificial Intelligence Ray-Tracing Optimization Combined With Higher Fluence Corneal Crosslinking: The Ray-Tracing Athens Protocol

PURPOSE

The aim of this study was to report novel ray-tracing customization of surface excimer laser ablation combined with higher fluence corneal crosslinking (CXL) in the stabilization and normalization of ectasia and visual rehabilitation of progressive keratoconus.

METHODS

A 28-year-old man with bilateral progressive keratoconus was treated with Athens protocol: CXL combined with photorefractive surface ablation customized by a novel artificial intelligence platform calculating lower- and higher-order aberrations based on wavefront, Scheimpflug tomography, and interferometry axial length data from a single diagnostic device. Visual acuity, refractive error, keratometry, optical coherence tomography and Scheimpflug tomography, and endothelial cell density were evaluated over 12 months.

RESULTS

Keratoconus stabilized in both eyes. Uncorrected distance visual acuity changed from 20/80 to 20/20 in the OD and from 20/40 to 20/25 in the OS at 12 months. Keratometry changes were as follows: from 40.7 and 42.7 at 165.1 degrees to 41.4 and 43.1 at 169.3 degrees in the OD and from 40.9 and 42.6 at 15.9 degrees to 44.1 and 44.7 at 9.8 degrees in the OS. Corneal surface normalization was as follows: index of height decentration from 0.115 to 0.099 and index of surface variance from 77 to 67 in the OD and index of height decentration from 0.066 to 0.014 and index of surface variance from 49 to 31 in the OS.

CONCLUSIONS

We introduced in this study the management of progressive keratoconus with CXL combined with novel excimer laser customization using several independent up-to-now diagnostics calculated by software, evaluating bidirectional theoretical ray tracing. It bears the potential advantage of addressing more accurately normalization of the distorted human eye optics associated with corneal ectasia, compared with using anterior corneal surface data or wavefront data alone.

Safety and Efficacy of Corneal Minimized-Volume Ablation With Accelerated Cross-Linking in Improving Visual Function for Keratoconus

PURPOSE

To evaluate the safety and efficacy of corneal minimized-volume ablation with accelerated cross-linking in improving visual function in keratoconus eyes.

METHODS

Through a pilot study, 25 eyes of 25 consecutive patients with keratoconus grade I-III were recruited that underwent corneal transepithelial photorefractive keratectomy with "minimized volume" ablation profile and accelerated corneal cross-linking in the same session. Corrected and uncorrected distance visual acuities, manifest refraction, corneal curvature and higher-order aberrations, endothelial cells, and the ocular modulation transfer function were assessed preoperatively and postoperatively, with a minimum follow-up of 6 months. A P value < 0.05 was the threshold of statistical significance.

RESULTS

At 8.2 ± 3.6 months postoperatively, the mean corrected and uncorrected distance visual acuities (LogMAR) were 0.07 ± 0.15 and 0.45 ± 0.39, significantly improving from the baseline of 0.24 ± 0.24 (P8m-before = 0.005) and 1.12 ± 0.33 (P8m-before < 0.001), respectively. Spherical equivalent was -2.80 ± 2.72 diopters (D), significantly decreasing from the baseline of -6.61 ± 3.06 D (P8m-before < 0.001), whereas the attempted corrected spherical equivalent was-2.30 ± 1.22 D. Meanwhile, a significant reduction was found in higher-order aberration, along with the postoperative improvement in ocular modulation transfer function. Corneal surface morphological parameters were found with significant decreases postoperatively (index of surface variance: P8m-before = 0.003; index of vertical asymmetry: P8m-before = 0.005; keratoconus index: P8m-before = 0.004; center keratoconus index: P8m-before = 0.003; and index of height decentration: P8m-before < 0.001). Nevertheless, no significant change was found in posterior corneal curvature or endothelial cell density between pre- and post-operative periods.

CONCLUSIONS

Corneal minimized-volume ablation with accelerated cross-linking was an effective and safe option for correction of mild refractive error, leading to significant improvement of visual function in patients with keratoconus.

Topography-guided corneal surface laser ablation combined with simultaneous accelerated corneal collagen cross-linking for treatment of keratoconus

Background

to study the outcomes of topography-guided customized excimer laser subepithelial ablation combined with accelerated CXL for progressive keratoconus.

Methods

Thirty-one eyes of 30 patients with progressive keratoconus were included in this prospective study. Topography-guided excimer laser ablation without refractive correction was performed. Simultaneous accelerated collagen cross-linking with ultraviolet light of 30 mW/cm² for 4 min was followed. Uncorrected distance visual acuity (UCVA), manifest refraction, corrected distance visual acuity (CDVA), tomograghy were examined at postoperative 1, 6, and 12 months.

Results

UDVA improved slightly after surgery (P > 0.05). BSCDVA improved significantly from 0.32 ± 0.20 logMAR to 0.15 ± 0.14 logMAR at postoperative 12 months (P < 0.05). During 12-month follow-ups, there were no significant differences in manifest refraction and corneal keratometry except for maximal keratometry value of the anterior surface (K_apex), which decreased significantly from 57.23 ± 5.09D to 53.13 ± 4.47D (P < 0.05). Even though the thinnest corneal thickness decreased from 465 ± 24 μm to 414 ± 35 μm (P < 0.05), curvature asymmetry index front (SIf), keratoconus vertex front (KVf) and Baiocchi Calossi Versaci index front (BCVf) decreased significantly till postoperative 12 months (P < 0.05). Corneal higher-order aberrations and coma also decreased significantly till 12 months after surgery (P < 0.05).

Conclusions

Topography-guided surface ablation without refractive correction combined with simultaneous accelerated collagen cross-linking provided good stability in refraction and corneal curvature, and also showed significant improvement in BSCDVA, corneal regularity and corneal optical quality.

Keratoconus concordance in monozygotic twins before and after combined CXL/PRK (Athens Protocol) using Scheimflung and OCT tomography

PUPOSE

To describe the concordance of keratoconus expression in two pairs of monozygotic twins before and after a combined CXL/PRK procedure.

SETTING

Private Ambulatory Eye Surgery Unit.

DESIGN

Retrospective Interventional Twin Study.

METHODS

Two pairs of male monozygotic twins with keratoconus (KCN) were studied retrospectively. Improvement of flattest (k1) and steepest (k2) keratometry, Index of Height Decentration (IHD), corneal thickness at thinnest point and corneal epithelial thickness measured by AS-OCT and Scheimpflug tomography was compared between respective eyes of monozygotic twin siblings 1 to 5 years after the application of combined corneal cross linking (CXL) and topography guided photorefractive keratectomy (PRK) of part of the refractive error (the Athens Protocol).

RESULTS

Significant improvement was noted in all the keratometric indices of all 8 eyes after the combined CXL/PRK procedure.The difference in k1, k2, IHD corneal thickness at thinnest point and corneal epithelial thickness percentage improvement between the right eyes of each pair of twins was statistically significant 1 and 5 years post-operatively (P < .05). Statistically significant discordance in the aforementioned parameters percentage improvement was likewise observed between the left eyes of each pair of twins (P < .05).

CONCLUSIONS

Although a genetic predisposition in KCN is well documented, the discordance in keratometric indices improvement after a CXL/PRK procedure between respective eyes of monozygotic twins suggests that environmental influences may contribute to the disease expression as well. Variable degree of synergy in a combined CXL/PRK procedure may also explain the aforementioned discordant improvement.

Selective transepithelial ablation with simultaneous accelerated Corneal Cross-linking for corneal regularization of keratoconus: the STARE-X Protocol

Purpose

To evaluate the changes in refractive outcomes and corneal aberrations in central and paracentral keratoconus after Selective transepithelial topography-guided photorefractive keratectomy combined with Accelerated Corneal Collagen Cross-Linking (STARE-X).

Settings

Centro polispecialistico Mediterraneo, Siena Crosslinking Center and University of Messina (Italy).

Design

Prospective, interventional, multi-centric study.

Methods

One hundred eyes of 100 patients underwent STARE-X protocol. Patients were subdivided into 2 groups: Group 1 with cone located within the central 3-mm zone (50 eyes); and Group 2 (50 eyes) with cone located outside the central 3-mm zone. Follow-up was two years at least for all eyes. Outcome parameters included uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA). Corneal tomography and corneal wavefront aberrations were assessed and compared before and two years after the treatment.

Results

At 2 years UDVA, CDVA improved, as well as sphere, cylinder, K-max reduced after treatment in both groups (p<.001 respectively). Moreover, a statistically significant reduction was observed of total High-Order Aberrations Root Main Square (HOA RMS), Coma RMS and Spherical Aberration (SA RMS) in both groups (p<.001 respectively). However, CDVA improved more in Group 1 than in Group 2 (p<.02).

Conclusion

The STARE-X protocol demonstrated effective results in halting keratoconus progression and improving corneal regularity with a safe and effective profile. STARE-X improved both visual acuity and corneal aberration at 2 years. Longer follow-up studies are warranted to observe further long-term CXL flattening effect on the cone.

Comparison of accelerated CXL alone, accelerated CXL-ICRS, and accelerated CXL-TG-PRK in progressive keratoconus and other corneal ectasias

PURPOSE

To compare accelerated corneal crosslinking (CXL) alone, CXL with simultaneous intrastromal corneal ring segments (CXL-ICRS), and CXL with simultaneous topography-guided photorefractive keratectomy (CXL-TG-PRK) in progressive keratoconus, pellucid marginal degeneration (PMD), or laser in situ keratomileusis (LASIK)-induced ectasia.

SETTING

The Kensington Eye Institute and Bochner Eye Institute, Toronto, Canada.

DESIGN

Prospective nonrandomized interventional study.

METHODS

Visual and topographical outcomes using a comparative analysis adjusting for preoperative maximum keratometry (Kmax) were evaluated 1 year postoperatively.

RESULTS

Four hundred fifty-two eyes from 375 patients with progressive keratoconus, PMD, or LASIK-induced ectasia that underwent accelerated (9 mW/cm, 10 minutes) CXL alone (n = 204), CXL-ICRS (n = 126), or CXL-TG-PRK (n = 122) were included. Change in logarithm of the minimum angle of resolution uncorrected distance visual acuity was significant with CXL-ICRS (-0.31; 95% CI, -0.38 to -0.24) and CXL-TG-PRK (-0.16; 95% CI, -0.24 to -0.09), but not with CXL alone. No significant differences in change were found between the 3 groups. Change in corrected distance visual acuity (CDVA) was significant in all 3 groups: -0.12 (95% CI, -0.15 to -0.10) with CXL alone, -0.23 (95% CI, -0.27 to -0.20) with CXL-ICRS, and -0.17 (95% CI, -0.21 to -0.13) with CXL-TG-PRK. Improvement in CDVA was greater with CXL-ICRS than with CXL alone (-0.08 ± 0.02; P < .0001) and CXL-TG-PRK (-0.05 ± 0.02; P = .005). Change in Kmax was significant with CXL-ICRS [-3.21 diopters (D); 95% CI, -3.98 to -2.45] and CXL-TG-PRK (-3.69 D; 95% CI, -4.49 to -2.90), but not with CXL alone (-0.05 D; 95% CI, -0.66 to 0.55).

CONCLUSIONS

CXL alone might be best for keratoconic patients who meet the inclusion criteria. CXL-ICRS might be more effective for eyes with more irregular astigmatism and worse CDVA and CXL-TG-PRK for eyes requiring improvements in irregular astigmatism but still have good CDVA.

Toric phakic IOLs in keratoconus-evaluation of preoperative parameters on the outcome of phakic anterior chamber lens implantation in patients with keratoconus

Purpose

To evaluate the influence of the type of the keratectasia and preoperative keratometry readings on the efficacy of implantation of iris-fixated phakic anterior chamber intraocular lenses (pIOL) in patients with keratoconus.

Methods

In this retrospective study, iris-fixated pIOLs (Artisan/Artiflex (Ophtec®), Verisyse/Veriflex (AMO®)) were implanted in 38 eyes of 22 patients with stable keratoconus. Thirty-six eyes underwent corneal crosslinking (CXL) prior to the lens implantation. The refractive outcome was evaluated 6 weeks postoperatively and the influence of preoperative refraction and topo- and tomographical factors were analyzed.

Results

The mean postoperative uncorrected distance visual acuity (UDVA_post) was 0.25 ± 0.15 logMAR and was not statistically different from the mean preoperative corrected distance visual acuity (CDVA_pre), which was 0.24 ± 0.13 logMAR. Twenty-seven eyes (71%) reached UDVA_post/CDVA_pre ≥ 1 (efficacy index), whereas patients with PMD-like ectasia (n = 14) showed significantly (p = 0.003) higher efficacy index (100%) than patients diagnosed with keratoconus (n = 24) (54%). Higher eccentricity of the maximum posterior elevation showed a significant beneficial influence on the efficacy index (p = 0.021). Furthermore, a higher Amsler-Krumeich stage and preoperative MAE were correlated with a worse UDVA_post. The mean absolute spherical equivalent was significantly decreased from 5.71 ± 4.96 D to 1.25 ± 1.20 D (p < 0.001). No significant difference was found in endothelial cell count.

Conclusion

The results indicate that the implantation of phakic iris-fixated anterior chamber IOLs is a reasonable refractive option for patients with keratoconus. Keratoconus patients with a pellucidal marginal degeneration (PMD)-like appearance ectasia seem to benefit most from such procedures.

Corneal cross-linking (CXL) combined with refractive surgery for the comprehensive management of keratoconus: CXL plus

The past two decades have witnessed an unprecedented evolution in the management of keratoconus that demands a holistic approach comprising of inhibiting the ectatic progression as well as visual rehabilitation. The advent of corneal cross-linking (CXL) in the late 1990s resulted in long-term stabilization of the ectatic cornea along with limited reduction in corneal steepening and regularization of corneal curvature. However, CXL as a standalone procedure does not suffice in rehabilitating the functional vision especially in patients who are unwilling or intolerant towards contact lenses. The concept of “CXL plus” was proposed which incorporates adjunctive use of refractive procedures with CXL in order to overcome the optical inefficiency due to corneal irregularity, decrease the irregular astigmatism, correct the residual refractive error and improve functional visual outcome in keratoconus. Several refractive procedures such as conductive keratoplasty (CK), photorefractive keratectomy (PRK), transepithelial phototherapeutic keratectomy (t-PTK), intrastromal corneal ring segments (ICRS) implantation, phakic intraocular lens (PIOL) implantation and multiple other techniques have been combined with CXL to optimize and enhance the CXL outcome. This review aimed to summarize the different protocols of CXL plus, provide guidelines for selection of the optimum CXL plus technique and aid in decision-making for the comprehensive management of cases with primary keratoconus in addition to discussing the future and scope for innovations in the existing treatment protocols.

Topography-guided treatment in regular and irregular corneas

Over the last decade, refractive surgery has been revolutionized by advancements in ablation profiles, available for the treatment of both regular and irregular corneas. Advances in corneal imaging have helped highlight the presence of higher-order aberrations, the correction of which could result in a better quality of vision. Topographic measurements being static are more repeatable and pupil independent and therefore provide the ideal platform for correction of both lower and higher-order aberrations and could result in improved visual quality even in patients with seemingly regular corneas. The combination of topography-guided treatment with collagen cross-linking has further increased the scope of treating irregular corneas like keratoconus, post-laser in-situ keratomileusis ectasia, and pellucid marginal degeneration. This review delves into the current literature and guidelines available for the topographic treatment of regular and irregular corneas.

Comparison of Visual, Tomographic, and Biomechanical Outcomes of 360 Degrees Intracorneal Ring Implantation With and Without Corneal Crosslinking for Progressive Keratoconus: A 5-Year Follow-up

PURPOSE

To evaluate the long-term (5 years) results of 360 degrees intracorneal ring (ICR) implantation with and without corneal crosslinking (CXL) in patients with progressive keratoconus (KCN).

METHOD

This historical cohort study was performed on 35 eyes with progressive KCN, which was randomly divided into 2 groups. Fourteen patients were implanted only with ICR, and 21 patients with KCN were treated with ICR plus CXL simultaneously. Uncorrected distance visual acuity (UCDVA), corrected distance visual acuity (CDVA), and refractive components were collected from patients' medical records. The biomechanical properties of patients were measured using the Corvis ST (Oculus, Inc, Weltzar, Germany). Corneal topography and aberrometry parameters were also recorded from the Pentacam HR device (Oculus).

RESULTS

Both UCVA and CDVA increased in both groups after ICR implantation; however, this improvement was more significant in the ICR plus CXL group (P = 0.002 and P = 0.001, respectively). The mean improvement of CDVA in patients with ICR implantation with and without CXL was 0.56 ± 0.67 and 0.33 ± 0.61, respectively. A comparison of the long-term postoperative Tomographic and Biomechanical Index between 2 groups showed a better result in the ICR plus CXL group (P = 0.012). Topographic findings of the anterior corneal surface (flat-K, steep-K, mean-K, and astigmatism) after surgery were significantly better than before surgery in both groups (P < 0.05).

CONCLUSIONS

Although ICR implantation alone might halt the KCN progression with acceptable visual, topographic, and biomechanical outcomes, the combination of ICR and CXL has an adjuvant and synergistic effect, especially in long-term follow-up.

Simultaneous photorefractive keratectomy and accelerated collagen cross-linking in high-risk refractive surgery (Tehran protocol): 3-year outcomes

PURPOSE

To evaluate safety and efficacy of performing simultaneous photorefractive keratectomy (PRK) and collagen cross-linking (CXL) in myopic patients with preoperative risk factors for developing keratectasia.

METHODS

Seventeen eyes of 15 patients with at least one of the following risk factors were recruited: central keratometry (K_max) between 48 and 50, difference between inferior, superior corneal power (I-S value) between 1.4 and 1.9 and corneal thickness between 450 and 480 µm. Upon final stage of standard PRK, 0.02% mitomycin was applied for 30-50 s, and then, accelerated CXL was performed for 5 min. Pre- and postoperative Oculus Pentacam^® imaging for keratometry values, measurement of uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) were done for all patients.

RESULTS

Mean follow-up time was 32.08 ± 7.79 months (range 25-49 months). Mean age of patients was 28.78 ± 3.80 years. Mean postoperative spherical equivalent was + 0.19 ± 0.42 (- 0.5 to + 1.0 [D]). Mean UDVA and CDVA improved from 0.9062 ± 0.485 log MAR and 0.0148 ± 0.043 log MAR to 0.0173 ± 0.040 log MAR and 0.0057 ± 0.023 log MAR, respectively (P = 0.011, P = 0.735). Mild degree of early postoperative stromal haze was seen which did not persist more than 6 months. There was no late stromal haze, corneal ectasia or other major postoperative complication in the follow-up period.

CONCLUSION

Combined PRK and accelerated CXL is an efficient and safe procedure for high-risk refractive surgery candidates, with no increased risk of persistent corneal haze.

Refractive approaches to visual rehabilitation in patients with keratoconus

PURPOSE OF REVIEW

As keratoconus is a chronic disease affecting young people, vision-related quality of life is often significantly impaired in patients with this disease. However, successful management of keratoconus, including visual rehabilitation strategies, can improve quality of life in these patients. This review will describe clinical approaches that improve vision-related quality of life in patients with stable keratoconus.

RECENT FINDINGS

Several types of contact lenses including scleral lenses have been used successfully to manage keratoconus. Eyes with severe keratoconus, even those in which fitting with other types of lenses is challenging, can be successfully fitted with scleral lenses. Although laser ablative procedures, such as photorefractive keratectomy (PRK) have been traditionally contraindicated in patients diagnosed with or suspected of having keratoconus, PRK has been attempted to partially correct refractive errors in keratoconus. Although phototherapeutic keratectomy and radial keratotomy have been reported to be used in eyes with keratoconus, effectiveness and safety results have varied. Implantation of phakic intraocular lenses and intraocular lenses, including toric intraocular lenses, which primarily correct regular astigmatism, with cataract extraction or refractive lens exchange can improve vision-related quality of life in patients with keratoconus by significantly reducing cylinder while improving uncorrected visual acuity.

SUMMARY

Appropriate selection and application of treatment options based on consideration of multiple factors will help patients with keratoconus, improving their vision-related quality of life and delaying or avoiding keratoplasty.

High-Resolution Wavefront-Guided Photorefractive Keratectomy and Accelerated Corneal Crosslinking for Stabilization and Visual Rehabilitation of Keratoconus Eyes

PURPOSE

To evaluate the visual and refractive outcomes after high-resolution wavefront-guided (HRWG) surface ablation with corneal crosslinking (CXL) in keratoconus eyes.

PATIENTS AND METHODS

In this prospective, interventional case series, 47 eyes of 28 progressive keratoconus patients older than age 18 were enrolled. All patients underwent HRWG photorefractive keratectomy (PRK) with simultaneous accelerated CXL. The study parameters were manifest refraction spherical equivalent (MRSE), keratometric outcomes, uncorrected (UDVA) and corrected distance visual acuity (CDVA) at postoperative 6 and 12 months.

RESULTS

There was improvement in mean MRSE from -2.39±1.89 D preoperatively to -0.13 ± 0.68 D at 12 months, with corresponding improvement in UDVA from 0.77 ± 0.35 logMAR to 0.08 ± 0.12 logMAR and CDVA from 0.10 ± 0.11 logMAR to 0.02 ± 0.04 logMAR. Preoperative flat and steep keratometry (K) were 4wct 32.49 ± 1.67 D and 45.94 ± 2.10 D, respectively, and at postoperative 12 months were 41.36 ± 2.08 D and 42.65 ± 2.78 D, respectively. At postoperative 12 months, visual and refractive outcomes were maintained. Comparisons between preoperative and postoperative 12 month timepoints were statistically significant for all parameters.

CONCLUSION

Simultaneous wavefront-guided PRK followed by CXL is a promising treatment for the visual rehabilitation of keratoconus patients.

Comparative Evaluation of Central Corneal Thickness in Cross-Linked Keratoconic Eyes

PURPOSE

To compare the central corneal thickness (CCT) measurements measured by using the Pentacam Scheimpflug system with the CCT measured using ultrasound pachymetry (UP) and to compare the compatibility between the methods in normal, keratoconic, and cross-linked keratoconic corneas.

METHODS

The study included 50 eyes of 50 patients with keratoconus (keratoconus group), 50 eyes of 50 patients with progressive keratoconus who underwent corneal cross-linking treatment (CCL group), and 50 eyes of 50 healthy subjects (control group). Patients in the keratoconus and CCL groups were further classified into mild (mean keratometry [Km] ≤ 47 D) and moderate keratoconus subgroups (47.0 < Km < 52.0 D). CCT values were noted from the Pentacam Scheimpflug and UP.

RESULTS

The difference between the Pentacam and UP values was largest in the CCL group (-20.9 0.21.5 μm), followed by the keratoconus and control groups (-10.6 0.20.3 and 0.4 0.6.8 μm). The Pentacam and UP measurements were not comparable in the keratoconus and CCL groups (P = 0.001 and P < 0.001), whereas they were comparable in the control group (P = 0.62). In subgroup analysis, the 2 methods were comparable in the mild keratoconus subgroup (P = 0.12) and not comparable in the moderate keratoconus subgroup and in both mild and moderate subgroups of the CCL group (P = 0.001, P < 0.001 and P < 0.001).

CONCLUSIONS

Pentacam Scheimpflug tomography and UP can be used interchangeably in normal and mild keratoconic eyes, but not in moderate keratoconic and cross-linked keratoconic eyes. Pachymetry measurements from Scheimpflug must be interpreted with extreme caution with different methods before planning an invasive procedure in these eyes.

Ten-Year Outcomes of Progressive Keratoconus Management With the Athens Protocol (Topography-Guided Partial-Refraction PRK Combined With CXL)

PURPOSE

To report the safety and long-term efficacy of topography-guided partial-refraction PRK combined with corneal cross-linking (CXL) (the Athens Protocol), refractive, topographic, and pachymetric changes of keratoconic eyes treated were studied.

METHODS

Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refraction, keratometry, qualitative and quantitative assessment of corneal keratometric, and pachymetric properties recorded by topography and tomography were evaluated for 10 years postoperatively.

RESULTS

A total of 144 eyes were followed up for a mean 128 ± 4 months (range: 120 to 146 months). Mean UDVA markedly improved at 1 year (0.19 ± 0.17 to 0.53 ± 0.21 decimal) with further improvement to 0.55 ± 0.19 decimal at 10 years. CDVA increased from 0.59 ± 0.21 to 0.80 ± 0.17 decimal at 1 year and further to 0.81 ± 0.19 decimal at 10 years. Corneal thickness decreased from 468.74 ± 35.05 to 391.14 ± 40.07 μm at 1 year (P < .01) and up to 395.42 ± 32.21 μm at 10 years. Steep keratometry decreased from 50.57 ± 2.80 to 45.87 ± 2.70 diopters (D) (P < .01) at 1 year and to 44.00 ± 3.22 D at 10 years. Maximum keratometry decreased from 53.43 ± 2.97 to 46.17 ± 1.18 D at 1 year and 44.75 ± 2.14 D at 10 years (P < .01). A total of 94.4% demonstrated ectasia stabilization and 3.5% showed progressive "overcorrection" or "hyperopic" shift.

CONCLUSIONS

The Athens Protocol confirms long-term safety and efficacy for corneal ectasia and visual function. Most parameters had little change after 1 year, through year 10. [J Refract Surg. 2019;35(8):478-483.].

Central corneal regularization (CCR): an alternative approach in keratoconus treatment

Background

To evaluate the safety and efficacy of an approach that combines corneal customized transepithelial therapeutic ablation to treat irregular corneal optics and accelerated corneal collagen cross-linking (CXL) to strengthen the corneal tissue and stop the progression of keratoconus. The transepithelial therapeutic ablation applied a novel concept named central corneal regularization (CCR) which could correct the corneal morphological irregularities and the eye’s spherocylindrical refractive error with minimal stromal tissue removal.

Methods

Retrospective study. Eyes that underwent CCR combined with CXL were evaluated preoperatively and up to 12 months postoperatively for visual acuity, subjective refraction, corneal haze, pachymetry and maximum keratometry (Kmax).

Results

Twenty four eyes of 24 patients with a mean age of 28.92 ± 9.88 years were treated. The mean spherical equivalent (SE) refractive error changed from − 0.74 ± 1.17 D preoperatively to − 1.05 ± 1.52 D at 12 months postoperatively. The mean uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) improved. No eye lost lines of CDVA, 21 had a mean improvement of 3.21 lines. The mean cylinder error and Kmax value dropped from − 3.06 ± 1.83 D and 51.38 ± 3.29 D to − 1.04 ± 0.80 D and 48.70 ± 2.58 D, respectively. The mean haze score at 3, 6 and 12 months was 0.56, 0.19 and 0.06, respectively.

Conclusions

CCR combined with CXL offers promising results as a safe and effective treatment in keratoconic patients.

Combined Protocols for Corneal Collagen Cross-Linking with Photorefractive Surgery for Refractive Management of Keratoconus: Update on Techniques and Review of Literature

With the development and gradual dissemination of corneal collagen cross-linking (CXL) in the twenty-first century as an early treatment for keratoconus, the management paradigm has shifted to include a greater focus on complete refractive correction for these patients. Though supplemental hard contact lens therapy remains a mainstay of visual rehabilitation in keratoconus, there has been increasing appeal in a completely surgical approach by combining CXL with adjuvant refractive procedures to both halt the ectatic process and enhance functional visual outcomes. Collectively termed "CXL plus" procedures, several combined protocols have been studied to various degrees in conjunction with CXL, involving photorefractive keratectomy (PRK), transepithelial phototherapeutic keratectomy (PTK), conductive keratoplasty (CK), intrastromal corneal ring segments (ICRS) implantation, phakic intraocular lens (PIOL) implantation, or multiple of these techniques together. The scope of this review aims to encompass a summary of current CXL protocols and present the current status of studies involving adjunctive keratorefractive procedures combined with CXL. By discussing the results to date of these CXL plus protocols, we can assess what further areas of investigation are necessary within this field as the next step to optimizing treatment modalities and outcomes for our keratoconus patients, regardless of disease severity.

Long-Term Stability With the Athens Protocol (Topography-Guided Partial PRK Combined With Cross-Linking) in Pediatric Patients With Keratoconus

PURPOSE

To evaluate the safety, efficacy, and stability of topography-guided partial PRK combined with corneal cross-linking (CXL) (the Athens Protocol [AP]) in pediatric patients with keratoconus over a 4-year follow-up period.

METHODS

This prospective study included 39 keratoconic eyes of 21 patients younger than 18 years with clinical and imaging evidence of keratoconus progression. Partial topography-guided excimer laser ablation in conjunction with high-fluence CXL was performed in all patients according to the AP. Uncorrected distance visual acuity, corrected distance visual acuity, refraction, keratometry, endothelial cell density, topography, and tomography using both Scheimpflug and optical coherence tomography (OCT) were evaluated for 4 years postoperatively.

RESULTS

At 4 years postoperative, there was significant improvement in mean uncorrected distance visual acuity from 0.51 ± 0.31 (decimal) to 0.65 ± 0.26 (decimal; P < 0.05). Mean corrected distance visual acuity improved from 0.71 ± 0.22 (decimal) preoperatively to 0.81 ± 0.19 (decimal; P < 0.05), respectively. Mean flat keratometry (K1) and mean steep keratometry (K2) readings reduced from 44.95 ± 3.71 D and 49.32 ± 5.05 D, respectively, preoperatively to 43.14 ± 2.95 D and 46.28 ± 4.87 D, respectively, (P < 0.05) at 4 years. The mean anterior maximum keratometry (Kmax) reading reduced from 56.81 ± 2.94 D preoperatively to 48.11 ± 3.17 D at 48 months. The mean index of height decentration was 0.105 ± 0.054 μm preoperatively and 0.049 ± 0.024 (P < 0.05) at 4 years postoperative. Mean preoperative corneal thickness at the thinnest point was 436.7 ± 42.6 μm preoperatively, 392.50 ± 45.68 μm at 12 months postoperative, and 418.42 ± 17.01 μm at 4-year follow-up. Late-onset deep corneal haze, a potential intrinsic complication of this technique in pediatric patients, was encountered in 2 cases at least 1 year after the procedure.

CONCLUSIONS

Long-term results of the AP seem to be safe and effective in pediatric patients, with marked improvement in visual function and keratometric symmetry indices.

Standard cross-linking versus photorefractive keratectomy combined with accelerated cross-linking for keratoconus management: a comparative study

Purpose

To compare the safety and efficacy of standard 30 min epithelium‐off cross‐linking (CXL) versus photorefractive keratectomy (PRK) combined with accelerated epithelium‐off cross‐linking (AXL) for the treatment of progressive keratoconus (CXL‐Plus).

Methods

This study was a prospective multicentre comparative clinical study. A total of 125 eyes of 75 patients with grade 1 keratoconus and documented progression were divided into two groups. Group A included 58 eyes treated with standard CXL. Group B included 67 eyes treated with combined PRK and AXL. The recorded data included UDVA, CDVA, subjective and objective refraction, keratometry and pachymetry using corneal topographies preoperatively and postoperatively at 3, 6, 12 and 24 months of follow‐up.

Results

In group A, at 24 months of UDVA and CDVA were improved from 1.12 ± 0.38 and 0.58 ± 0.42 to 0.66 ± 0.20 and 0.20 ± 0.12 (LogMAR±SD). The spherical equivalent was reduced from 4.03 ± 1.18 to 1.78 ± 1.04 D. The cylinder reduction was 0.32 ± 0.19 D. In group B, at 24 months of UDVA and CDVA were improved from 1.26 ± 0.52 and 0.68 ± 0.36 to 0.58 ± 0.28 and 0.20 ± 0.16 (LogMAR ± SD). The spherical equivalent was reduced from 4.23 ± 0.95 to 1.92 ± 0.74 D. The cylinder reduction was ±1.76 D.

Conclusion

Surprisingly, standard CXL showed close results to CXL‐Plus at the 24th follow‐up month. Standard CXL acted as a stabilizing procedure associated with a late myopic component reduction. CXL‐Plus acted as a refractive and stabilizing procedure with an early effect on both the myopic and the astigmatic component but no later improvements. Standard CXL seems to be more powerful than AXL in its long‐term effect. Therefore, in the future, we want to test the combination of PRK with standard CXL.

Transepithelial Phototherapeutic Keratectomy Followed by Corneal Collagen Crosslinking for the Treatment of Pellucid Marginal Degeneration: Long-term Results

PURPOSE

To evaluate visual, refractive, topographic, and aberrometric outcomes of transepithelial phototherapeutic keratectomy (PTK) + corneal collagen crosslinking in the treatment of pellucid marginal degeneration.

METHODS

This retrospective study includes 20 eyes of 15 patients with pellucid marginal degeneration treated with transepithelial PTK + accelerated corneal collagen crosslinking. Visual acuity, refraction, topographic keratometry, pachymetry, and aberrations were recorded pretreatment and 6, 12, 24, and 36 months after treatment.

RESULTS

Stabilization in visual acuity was observed throughout the 36 months of follow-up (P > 0.05). The cylindrical value was significantly lower (P < 0.05) during the follow-up compared with the baseline (4.97 ± 2.00, 3.86 ± 2.01, 3.92 ± 2.27, 2.87 ± 1.70, and 3.28 ± 3.12 D at the baseline and postoperative 6th, 12th, 24th, and 36th month, respectively). Spherical equivalent was significantly lower at the 24th (P = 0.02) and 36th month (P = 0.01) follow-up intervals. A significant decrease (P < 0.05) in average keratometry readings was observed in all follow-up points (47.12 ± 4.66, 46.65 ± 4.38, 46.57 ± 4.57, 46.46 ± 4.81, and 46.27 ± 4.46 D, respectively). The maximum keratometry value remained stable (P > 0.05) in all visits (64.30 ± 10.70, 63.49 ± 10.05, 62.97 ± 9.50, 63.33 ± 10.06, and 62.27 ± 10.36 D, respectively). The Baiocchi Calossi Versaci index was significantly lower (P < 0.05) at all follow-up points compared with the baseline (3.21 ± 1.93, 2.99 ± 1.96, 2.96 ± 1.93, 2.82 ± 1.95, and 2.86 ± 1.99 μm, respectively). Central and minimum corneal thicknesses were significantly lower (P ≤ 0.01) compared with the baseline throughout the follow-up. Higher order aberration, trefoil, coma, and spherical aberration values remained stable during the follow-up compared with the baseline (P > 0.05).

CONCLUSIONS

The combination of transepithelial PTK with accelerated corneal collagen crosslinking seems to be an effective treatment in patients with pellucid marginal degeneration in the long-term.

Corneal Safety and Stability in Cases of Small Incision Lenticule Extraction with Collagen Cross-Linking (SMILE Xtra)

Purpose

To assess the safety and stability in cases of small incision lenticule extraction with collagen cross-linking (SMILE Xtra).

Methods

This study was a retrospective interventional comparative study that included 60 eyes of 30 patients divided equally into two groups: SMILE Xtra and SMILE alone. The inclusion criteria were patients >18 years of age, myopic error >6 D, thinner cornea <520 microns, and abnormal corneal topography. Outcome data were recorded including uncorrected distance visual acuity and corrected distance visual acuity (UDVA and CDVA), manifest refraction spherical equivalent (MRSE), central corneal thickness, average keratometry, endothelial cell density, corneal resistance factor (CRF), and corneal densitometry. The follow-up period was 24 months.

Results

There was a significant difference between the 2 groups regarding UDVA, CDVA, and MRSE at 1 month. In the SMILE Xtra group, 90% of eyes had postoperative UDVA of 20/20 and 97% had UDVA of 20/30 at 24 months. At 24 months, 26 eyes (87%) vs. 25 eyes (84%) were within ±0.50 D of attempted correction in SMILE Xtra and SMILE groups, respectively. Regarding stability, both groups showed improvement of MRSE at 1^st month postoperatively and remained stable along the 24 months of follow-up. CRF and corneal densitometry were higher in the SMILE Xtra group along the whole follow-up period (p=0.001).

Conclusion

Combining corneal cross-linking with SMILE procedure (SMILE Xtra) is a promising tool to prevent ectasia in high-risk patients. It is a safe and simple procedure that can be offered to patients undergoing SMILE with risk for ectasia. Trial registration no: PACTR201810577524718.

Management of progressive keratoconus with partial topography-guided PRK combined with refractive, customized CXL - a novel technique: the enhanced Athens protocol

Purpose

To report a novel application of partial topography-guided photorefractive keratectomy combined with topographically customized, higher fluence, and variable pattern corneal cross-linking applied on the same day of the treatment of keratoconus.

Methods

A topography-guided partial photorefractive keratectomy treatment of maximum 30 µm over the thinnest cone area was applied initially followed by a 7 mm, 50 µm phototherapeutic keratectomy treatment to address epithelial removal. 0.02% Mitomycin C was applied for 20 seconds and then the exposed stroma was soaked with 0.1% riboflavin solution for 5 minutes. The cornea was then treated with a customized, variable-pattern and 20 mW/cm² fluence for a total of 5-10 J, and up to 15 J of energy was delivered with the KXL-II device employing an active tracker. The center of the pattern that received the 15 J was topography-matched with the thinnest area of the cone. Visual acuity, refractive error, cornea clarity, keratometry, topography, pachymetry with a multitude of modalities and endothelial cell density were evaluated over 36 months.

Results

Keratoconus was stabilized in all cases. The severity of keratoconus stage by Amsler- Krumeich criteria improved from an average of 3.2 (1-4) to 1.8 (0-3). Uncorrected distance visual acuity changed from preoperative 20/80 to 20/25 at 6 months. A maximum astigmatic reduction of 7.8 D (5.3-15.6), and a significant cornea surface normalization (an index of height decentration improvement from 0.155 [±0.065] to 0.045 [±0.042]) were achieved by 1 month and remained relatively stable for 36 months postoperatively. Two cases delayed full reepithelialization for up to 9 days.

Conclusion

This paper introduces a novel technique in order to maximize the refractive normalization effect along with ectasia stabilization in young keratoconus patients. This may facilitate the use of less tissue ablation, in comparison to utilizing a homogeneous UV light beam for corneal cross-linking in Athens Protocol cases. It broadens the number of potential candidate cases that would have been limited to employ this technique due to tissue thickness limitations.

Haze and Visual Acuity Loss After Sequential Photorefractive Keratectomy and Corneal Cross-linking for Keratoconus

PURPOSE

To investigate the results after photorefractive keratectomy (PRK) followed immediately by standard 30-minute corneal cross-linking (CXL) for keratoconus.

METHODS

This retrospective study included 26 eyes of 16 patients with keratoconus. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (SE) and cylinder, apical keratometry, corneal higher order aberrations (HOAs), and corneal haze were evaluated.

RESULTS

Mean follow-up was 32 ± 8 months (range: 19 to 50 months) and mean patient age was 31 ± 5 years (range: 24 to 40 years). Mean UDVA improved significantly from 0.80 ± 0.39 to 0.32 ± 0.36 logMAR after surgery (P < .001), but the mean CDVA worsened significantly from 0.07 ± 0.09 to 0.15 ± 0.14 logMAR after surgery (P = .006). Thirteen eyes (50%) lost at least one line of CDVA, 3 eyes (12%) lost two lines, and 4 eyes (15%) lost three lines. SE, cylinder, and apical keratometry decreased significantly. Corneal haze grade 1 was found in 15 eyes (57.7%), grade 2 in 6 eyes (23.1%), and grade 3 in 1 eye (3.8%). A significant correlation was seen between postoperative CDVA loss and corneal haze (P = .001) and history of atopy (P < .01), but not with corneal HOA change.

CONCLUSIONS

Despite an improvement in UDVA and topographic values, the loss of CDVA, explained by postoperative haze, demonstrates that this procedure should be approached with caution, may not be as safe as initially thought, especially in patients with atopy and can cause severe visual acuity loss. [J Refract Surg. 2019;35(2):109-114.].

Outcomes of Simultaneous and Sequential Cross-linking With Excimer Laser Surface Ablation in Keratoconus

PURPOSE

To evaluate the outcomes of simultaneous and sequential corneal crosslinking (CXL) and excimer laser surface ablation protocols in keratoconus.

METHODS

A literature review was conducted using MEDLINE. The studies were divided into three groups: the sequential group included studies with CXL followed by excimer laser surface ablation later, the simultaneous group included simultaneous excimer laser surface ablation and CXL, and the no CXL group included excimer laser surface ablation only with no CXL. The data on change in logMAR uncorrected distance visual acuity (UDVA), spectacle corrected distance visual acuity (CDVA), change in spherical equivalent (SE) and refractive astigmatism, change in maximum keratometry (Kmax), complications, and safety and efficacy indices were presented for the latest follow-up visits in all groups.

RESULTS

Twenty-one studies (3 = sequential; 11 = simultaneous, 7 = no CXL) were included. UDVA improved in all groups. CDVA improved more in the sequential group. SE change was greatest in the no CXL group and the refractive astigmatism reduced comparably in the sequential and no CXL groups but less in the simultaneous group. Kmax reduced in all groups. Only the sequential group showed no progression. Corneal haze was reported in 100%, 54.5%, and 57.1% studies, respectively. Safety and efficacy indices were 1.96 and 1.58, 1.41 ± 0.32 and 0.91 ± 0.41, and 1 and 0.82, respectively.

CONCLUSIONS

The sequential group showed greater improvement in CDVA, SE, and refractive astigmatism. Corneal haze was frequently reported in all protocols. Safety and efficacy indices were highest when CXL was performed before excimer laser and least when excimer laser was performed alone without CXL. [J Refract Surg. 2018;34(10):690-696.].

Two-stage procedure in the management of selected cases of keratoconus: clear lens extraction with aspherical IOL implantation followed by WFG-PRK

AIM

To assess the objective and subjective results of a two-stage procedure for management of keratoconus: clear lensectomy with aspherical intraocular lens (IOL) implantation followed by wave front-guided photorefractive keratotomy (WFG-PRK).

METHODS

This prospective interventional non-randomized study included patients aged 35 years old or more with grade I and II stable keratoconus, a clear visual axis, minimal corneal thickness (MCT) 420 µm or more and average keratometric reading (K) less than 54 diopter (D). Refraction of all selected eyes should be -8.00 D sphere or more with less than -6.00 D cylinder and could be corrected two lines or more with spectacles or contact lenses. All studied eyes underwent a two-stage approach treatment: first refractive lens exchange and aspherical IOL implantation followed, after at least 3mo, by WFG-PRK. Pre and postoperative complete ophthalmological examination were performed. Topographical, visual and aberrometric results were recorded and evaluated during 6mo follow up period. Moreover, patient satisfaction and other subjective outcomes were also analyzed.

RESULTS

The 13 eyes of 11 patients diagnosed with stable keratoconus and aged from 39 to 49y (42.4±6.2y) were enrolled in the study. At baseline, 8 eyes had grade I and 5 eyes had grade II keratoconus. The manifest sphere was -10.3±4.2 D (ranged from -8.0 to -14.0 D) and the manifest cylinder was -4.2±1.2 D (ranged from -1.75 to -5.50 D). After the two-stage procedure, sphere and cylinder reduced significantly to -0.43±0.22 D and -1.3±0.72 D respectively (P<0.001). There was also a highly significant improvement in the mean uncorrected distance visual acuity (UDVA) from logMAR 1.41±0.49 preoperatively to 0.51±0.16 postoperatively (P<0.001) and the mean corrected distance visual acuity (CDVA) from 0.76±0.24 preoperatively to 0.49±0.13 after the operation (P<0.001). All aberrometric and mesopic vision parameters and most of the topographical indices demonstrated highly significant improvement that remains stable until the end of follow up. All recorded subjective data revealed a high degree of patient satisfaction.

CONCLUSION

Two-stage approach (clear lens exchange with monofocal IOL followed by WFG-PRK) in selected cases of keratoconus is a safe, effective and highly predictable procedure with satisfactory visual and refractive results.

Simultaneous Transepithelial Topography-Guided Photorefractive Keratectomy and Accelerated Cross-Linking in Keratoconus: 2-Year Follow-Up

Purpose

To evaluate the visual, refractive, and topographic outcomes after simultaneous topography-guided transepithelial photorefractive keratectomy (transepithelial TG-PRK) using the Amaris Excimer laser platform and accelerated corneal cross-linking (CXL) in eyes with keratoconus.

Materials and Methods

Patients with 2 years of follow-up were included in this retrospective case series. Manifest refraction (MR), uncorrected (UDVA) and corrected (CDVA) distance visual acuity, corneal topography, and pachymetry were evaluated at 1, 3, 6, 12, and 24 months after surgery. The root-mean-square of total higher-order aberrations (total HOA-RMS), coma (Coma-RMS), and spherical aberration (SA-RMS) were calculated for 4- and 6-mm diameters.

Results

Forty-six eyes of 46 patients were included in the study. Stromal ablation was ≤50 μ in all patients. MR was −3.78±3.26 preoperatively and −1.39±1.82 postoperatively. Significant improvements were seen in the UDVA and Coma-RMS values at 1 month, CDVA and total HOA-RMS values at 3 months, and SA-RMS values at 1 year compared to preoperative levels. UDVA values further improved after 2 years, compared to the 1-year values. No patient lost two or more lines and keratoconus progression was not observed in any patient.

Conclusion

Simultaneous transepithelial TG-PRK and accelerated CXL resulted in significant gains in CDVA without compromising CXL efficacy.

Evaluation of the Effectiveness of Cross-Linking Combined With Photorefractive Keratectomy for Treatment of Keratoconus

PURPOSE

To evaluate the effectiveness and safety of combined epithelium-off cross-linking (CXL) with photorefractive keratectomy (CXL Plus) for correction of the myopic and astigmatic components of keratoconus.

METHODS

Seventy-nine eyes of 46 patients who underwent CXL Plus were enrolled in this retrospective, multicenter, noncomparative clinical study. Uncorrected distance visual acuity, corrected distance visual acuity, refraction, keratometry, and pachymetry measurements were recorded preoperatively and at 3, 6, 12, and 18 months during follow-up.

RESULTS

The mean (±SD) preoperative uncorrected distance visual acuity and corrected distance visual acuity were 1.00 ± 0.22 logarithm of the minimum angle of resolution (logMAR) and 0.62 ± 0.38 logMAR, respectively, and improved to 0.71 ± 0.36 logMAR and 0.32 ± 0.18 logMAR postoperatively. The mean k value, mean corneal thickness at the thinnest location, and mean myopic and astigmatic components decreased from 46.58 ± 0.97 D, 473 ± 29 μm, 3.65 ± 1.72 D, and 1.83 ± 0.69 D preoperatively to 43.79 ± 1.17 D, 431 ± 38 μm, 1.02 ± 0.78 D, and 1.15 ± 0.26 D, respectively, during follow-up. Eleven eyes had delayed epithelial healing, 2 had stromal opacities, 1 had primary herpes simplex keratitis, and 5 showed progression of keratoconus.

CONCLUSIONS

CXL Plus improved the refractive status of keratoconus during 18 months of follow-up, despite its potential early postoperative complications of delayed epithelial healing and corneal haze. CXL Plus reduced the myopic component more than the astigmatic component of keratoconus. However, the safety and stability of the procedure were offset by longer-term postoperative complications and a high rate of postoperative progression of keratoconus.