Simultaneous Topography-Guided Photorefractive Keratectomy and Accelerated Corneal Collagen Cross-Linking for Keratoconus

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.

Refractive surgical approaches to keratoconus: A systematic review and network meta-analysis

Advancements in diagnostic methods and surgical techniques for keratoconus (KC) have increased non-invasive treatment options. Successful surgical planning for KC involves a combination of clinical science, empirical evidence, and surgical expertise. Assessment of disease progression is crucial, and halting the progression should be the focus if it is progressive. While surgeons used to rely on experience alone to decide the surgical method, comparing the network of primary factors, such as visual acuity, across studies can help them choose the most appropriate treatments for each patient and achieve optimal outcomes. Meticulous tabulation methods facilitate interpretation, highlighting the importance of selecting the correct surgical and rehabilitation approach based on each patient's condition and stage of the disease. We detail the outcomes of a comprehensive network meta-analysis comparing the effectiveness of various combined therapeutic refractive treatments for KC at identical stages of the disease, spanning 4 distinct follow-up intervals. Additionally, the comprehensive analysis suggests that for corneas with optimal best corrected visual acuity (BCVA) preoperatively (classified as regular), combining phakic intraocular lenses with intracorneal ring segments (ICRS) and corneal cross-linking (CXL) could offer the best therapeutic approach provided the disease stage does not exceed stage 3. For irregular corneas, although initial follow-ups show a significant difference in BCVA with surface ablation, longer-term follow-ups recommend combining surface ablation with ICRS and CXL, especially at higher stages.

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.

Expanding indications for corneal cross-linking

PURPOSE OF REVIEW

The aim of this study was to summarize the recent developments in corneal cross-linking (CXL) and its indications, including corneal ectasias, refractive surgery and infectious keratitis.

RECENT FINDINGS

Advances in CXL technology, such as the use of higher-intensity LED ultraviolet (UV) light sources and a better understanding of the UV-riboflavin photochemical reaction, have enabled safer and more effective methods of cross-linking thin and ultra-thin corneas, and more effective accelerated transepithelial/'epi-on' CXL procedures that are beginning to supplant the Dresden protocol as the 'gold standard' CXL method. CXL is also being used in combination with laser surgery, not only to expand the patient base who can receive refractive surgery, but also to help rehabilitate vision in patients with ectasia. CXL, and CXL combined with photorefractive keratectomy (PRK), can result in corneal flattening of 1-2 D, and corneal regularization of 4-5 D, respectively. Finally, photoactivated chromophore for keratitis-corneal cross-linking (PACK-CXL) has been shown to be an effective therapy for infectious keratitis, both alone, and in combination with antimicrobial drugs.

SUMMARY

CXL has evolved from a single technique to treat a single corneal ectasia, keratoconus, to several techniques with several indications, spanning a spectrum of corneal ectasias, as well as visual rehabilitation, refractive procedures and infectious keratitis treatment.

Visual and Refractive Outcomes of Toric Implantable Collamer Lens Implantation in Stable Keratoconus After Combined Topography-Guided PRK and CXL

PURPOSE

To evaluate the safety and efficacy of toric implantable Collamer lens (ICL) (STAAR Surgical) implanted at least 6 months after combined topography-guided photorefractive keratotomy (TG-PRK) and corneal cross-linking (CXL) in keratoconus.

METHODS

This retrospective study included 46 eyes with keratoconus of 31 patients who underwent toric ICL implantation after previous TG-PRK+CXL. Patients were examined for uncorrected (UDVA) and corrected (CDVA) distance visual acuity, flat and steep keratometry, and manifest refraction spherical equivalent preoperatively and 12 months postoperatively.

RESULTS

At 12 months postoperatively, there was a statistically significant improvement in visual and refractive outcomes (all P < .001). Mean UDVA improved to 0.17 ± 0.14 logMAR (vs 1.00 ± 0.38 logMAR preoperatively) and mean manifest refraction spherical equivalent improved to -0.32 ± 1.42 diopters (D) (vs -7.35 ± 5.20 D preoperatively). At 12 months, 63% of eyes achieved UDVA of 20/32 or better and 60.9% of eyes were within ±0.50 D of manifest refraction spherical equivalent. Mean refractive astigmatism improved from -2.90 ± 2.21 D preoperatively to -1.47 ± 1.46 D at postoperative 12 months (P < .001), with 30.4% and 45.7% of eyes having a postoperative astigmatic error within ±0.50 and ±1.00 D, respectively. No complications were observed.

CONCLUSIONS

Toric ICL implantation was found to be safe and effective for the correction of myopia and myopic astigmatism in patients with stable keratoconus who had undergone TG-PRK+CXL, as revealed by the statistically significant improvement in visual and refractive outcomes at 12 months after toric ICL implantation. [J Refract Surg. 2021;37(12):824-829.].

Clinical outcomes of transepithelial PRK using SCHWIND AMARIS laser platform with actual versus default epithelial thickness values

PURPOSE

to investigate the clinical outcomes of transepithelial photorefractive keratectomy (tPRK) with actual epithelial thickness versus default software values.

METHODS

eighty-three patients with refractive spherical error of -1.50 to -7.00 diopters (D), and refractive astigmatism up to 4.00 D were consecutively enrolled and divided into two groups: group 1 undergone tPRK with actual central and peripheral epithelial thickness input in right eyes, group 2 undergone tPRK with actual central and 10 μm higher peripheral epithelial thickness in right eyes, left eyes underwent tPRK with default protocol in both groups. Outcome measures were induced refractive error, achieved optical zone (OZ), and wasted stromal tissue.

SETTING

Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, IranDesign: prospective controlled study.

RESULTS

Mean ± SD of induced spherical equivalent (SE) was +0.15 ± 0.39 D and +0.01 ± 0.35 D in right and left eyes of group 1 (p=0.01), and +0.04 ± 0.22 D and +0.03 ± 0.23 D in right and left eyes of group 2 (p=0.75), respectively. There was no statistically significant difference between wasted tissue between right and left eyes in group 1 and group 2 (p=0.77 and p=0.49, respectively). OZ contraction was significantly higher in right compared to left eyes in group 1 (p=0.05), but not in group 2 (p=0.95).

CONCLUSION

In tPRK, refractive outcomes, wasted tissue, and OZ contraction depend little on pre-existing corneal epithelial thickness in corneas with normal range epithelial thickness. However, OZ contraction may be a concern in lower amount of ablations.

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.

Epithelial photorefractive keratectomy vs mechanical epithelial removal followed by corneal crosslinking for keratoconus: the Tel-Aviv Protocol

PURPOSE

To compare the Tel-Aviv Protocol, epithelial photorefractive keratectomy (ePRK) combined with corneal crosslinking (CXL), to CXL with alcohol-assisted epithelial removal (Alc-CXL) for progressive keratoconus.

SETTING

Care-Vision Laser Centers, Tel Aviv, Israel.

DESIGN

Retrospective study.

METHODS

All patients underwent Alc-CXL or ePRK, a 50 μm laser ablation of the epithelium with a myopic spherical component and an astigmatic component, followed by CXL. All patients completed at least 1 year of follow-up.

RESULTS

A total of 131 eyes of 131 patients were included in the study. Fifty patients (38%) were included in the Tel-Aviv Protocol group, and 81 patients (62%) were included in the Alc-CXL group. There was a significant improvement in uncorrected distance visual acuity (UDVA) (from 1.22 ± 0.75 logarithm of the minimum angle of resolution [logMAR] to 0.49 ± 0.44 logMAR, P < .001), corrected distance visual acuity (CDVA) (from 0.29 ± 0.17 logMAR to 0.16 ± 0.12 logMAR, P < .001), Kmax (from 48.50 ± 3.00 diopters [D] to 46.50 ± 3.00 D, P < .001), and cylinder (from -3.31 ± 1.70 D to -2.32 ± 1.66 D, P < .001) in the Tel-Aviv Protocol group in comparison with nonsignificant changes in the Alc-CXL group in UDVA (from 0.89 ± 0.62 logMAR to 0.81 ± 0.65 logMAR, P = .23), CDVA (from 0.25 ± 0.21 logMAR to 0.21 ± 0.17 logMAR, P = .10), Kmax (from 46.50 ± 4.50 D to 46.00 ± 4.40 D, P = .08), and cylinder (from -2.99 ± 2.05 D to -2.80 ± 1.75 D, P = .39) at the end of the follow-up period.

CONCLUSIONS

The Tel-Aviv Protocol for progressive keratoconus patients provided good improvement in visual acuity and astigmatism while halting the progression of keratoconus.

Epithelial Photorefractive Keratectomy and Corneal Cross-linking for Keratoconus: The Tel-Aviv Protocol

PURPOSE

To present the Tel-Aviv Protocol for patients with progressive keratoconus, which consists of epithelial photorefractive keratectomy (ePRK), and corneal cross-linking (CXL).

METHODS

This was a retrospective case series of 20 consecutive patients diagnosed as having progressive keratoconus at Care-Vision Laser Centers, Tel Aviv, Israel. The Tel-Aviv Protocol included laser epithelial ablation using the EX500 excimer laser (Alcon Laboratories, Inc., Fort Worth, TX) with 50% of the manifest refractive astigmatism (on the same axis) while the spherical ablation is added so as not to exceed a total of 50-µm ablation of the epithelium and anterior stroma. Afterward, all patients underwent CXL. Data collected included thinnest corneal thickness (TCT), subjective astigmatism, mean keratometric power, maximum keratometric power (K_max), uncorrected distance visual acuity (UDVA), and corrected distance visual acuity (CDVA).

RESULTS

A total of 20 eyes of 20 patients with a mean age of 28.0 ± 6.5 years (range: 13 to 40 years) and a mean follow-up of 823 ± 337 days (range: 266 to 1,749 days) were included. There was a significant improvement in both UDVA (from 0.95 ± 0.73 to 0.22 ± 0.15 logMAR, P < .001) and CDVA (from 0.24 ± 0.13 to 0.13 ± 0.12 logMAR, P < .001) at the end of the follow-up period. There was a significant improvement in mean keratometry (from 46.86 ± 2.48 to 45.00 ± 2.27 diopters [D], P < .001), K_max (from 48.18 ± 2.74 to 45.97 ± 2.55 D, P < .001), and K_min (from 45.54 ± 2.35 to 44.03 ± 2.12 D, P < .001). TCT was significantly lower following the procedure (from 450.90 ± 35.99 to 404.90 ± 43.96 µm, P < .001). No complications and no progression in keratoconus severity were noticed during the follow-up period.

CONCLUSIONS

The Tel-Aviv Protocol for patients with progressive keratoconus provides good improvement in visual acuity and astigmatism while halting the progression of keratoconus. [J Refract Surg. 2019;35(6):377-382.].

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.

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.

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

Aims

To evaluate the safety and efficacy of corneal cross-linking (CXL) followed by photorefractive keratectomy (PRK) for refractive correction in patients with bilateral asymmetric topography.

Methods

Forty-four patients (88 eyes) were enrolled in this prospective randomised clinical trial. CXL with subsequent PRK after 6 months was performed in one eye (study group), and PRK alone was performed in contralateral eyes (control group). Patients were followed for 24 months after PRK. Outcome measures investigated included visual acuity (VA), refraction, aberrometry, topography, pachymetry and endothelial cell count. Groups were compared with linear mixed regression and repeated measures logistic regression. Multiple comparison adjustment with the Holm procedure was performed.

Results

At baseline, the logMAR VA (best spectacle corrected) in study and control groups was 0.12±0.13 (mean±SD) and 0.08D±0.14, respectively, and axial inferior–superior index (IS) (topographic IS) in study and control groups were 0.59D±0.31D and 0.58D±0.32D, respectively. After 24 months, a mean under correction of −0.50D was observed in both groups. Change from baseline in logMAR VA in study and control groups was 0.00D±0.08D and −0.02D±0.10D, respectively. Frequency of haze at 30 months in study and control group eyes was, respectively, 18.2% and 4.6% (p=0.05). There was no statistical difference between groups in spherical aberration and coma after adjustment for multiple comparisons.

Conclusions

Non-simultaneous CXL followed by PRK may be performed safely, and refractive results over a 2-year follow-up are highly similar in virgin and previously cross-linked corneas. Despite using mitomycin C, corneal haze can be significantly higher in the first year after PRK in eyes pretreated with CXL.

Outcomes of photorefractive keratectomy in patients with atypical topography

Background

Photorefractive keratectomy (PRK) is at risk of serious complications such as corneal ectasia, which can reduce corrected distance visual acuity. The rate of complications of PRK is higher in patients with atypical topography.

Objective

To determine the outcomes of photorefractive keratectomy in patients with atypical topography.

Methods

This cross-sectional study was done in 2015 in Shiraz in Iran. We included 85 eyes in this study. The samples were selected using a simple random sampling method. All patients were under evaluation for uncorrected distance visual acuity, corrected distance visual acuity, manifest refraction, corneal topography, central corneal thickness using pentacam, slit-lamp microscopy, and detailed fondus evaluation. The postoperative examination was done 1–7 years after surgery. Data were analyzed using IBM SPSS 21.0 version. To analyze the data, descriptive statistics (frequency, percentage, mean, and standard deviation), chi-square, and independent samples t-test were used.

Results

We studied 85 eyes. Among the patients, 23 (27.1%) were male and 62 (72.9%) were female. Mean age of the participants was 28.25±5.55 years. Mean postoperative refraction was – 0.37±0.55 diopters. Keratoconus or corneal ectasia was not reported in any patient in this study. There was no statistically significant difference between SI index before and after operation (p=0.736). Mean preoperative refraction was −3.84 ± 1.46 diopters in males and −4.20±1.96 diopters in females; thus there was not statistically significant difference (p = 0.435).

Conclusion

PRK is a safe and efficient photorefractive surgery and is associated with low complication rate in patients with atypical topography.

Surgical Options for the Refractive Correction of Keratoconus: Myth or Reality

Keratoconus provides a decrease of quality of life to the patients who suffer from it. The treatment used as well as the method to correct the refractive error of these patients may influence on the impact of the disease on their quality of life. The purpose of this review is to describe the evidence about the conservative surgical treatment for keratoconus aiming to therapeutic and refractive effect. The visual rehabilitation for keratoconic corneas requires addressing three concerns: halting the ectatic process, improving corneal shape, and minimizing the residual refractive error. Cross-linking can halt the disease progression, intrastromal corneal ring segments can improve the corneal shape and hence the visual quality and reduce the refractive error, PRK can correct mild-moderate refractive error, and intraocular lenses can correct from low to high refractive error associated with keratoconus. Any of these surgical options can be performed alone or combined with the other techniques depending on what the case requires. Although it could be considered that the surgical option for the refracto-therapeutic treatment of the keratoconus is a reality, controlled, randomized studies with larger cohorts and longer follow-up periods are needed to determine which refractive procedure and/or sequence are most suitable for each case.

Accelerated versus conventional corneal crosslinking for refractive instability: an update

PURPOSE OF REVIEW

Corneal crosslinking (CXL) is a relatively new treatment modality offering refractive stability in patients with ectatic disorders. The procedure as initially described (Dresden protocol) is time consuming; accelerated protocols have been lately developed. The purpose of this review is to present the recent findings regarding the comparison of accelerated CXL with the conventional Dresden protocol.

RECENT FINDINGS

A variety of accelerated protocols are described in the literature. Safety and efficacy of the procedures with regard to stability seem to be equivalent in initial studies but indirect measures of efficacy, such as demarcation line depth and laboratory measurements, do not always confirm equivalence of accelerated protocols in comparison to conventional one. Modified accelerated protocols must be developed in order to overcome this.

SUMMARY

Accelerated CXL protocols seem to be a valid alternative to the conventional protocol; however, more comparative long term studies are needed to confirm the validity and to elucidate which accelerated protocol is ideal in each case.

Corneal collagen cross-linking. A review of its clinical applications

OBJECTIVE

To perform a literature review of the current clinical applications of corneal collagen cross-linking.

METHODS

An exhaustive literature search was made, including the main biomedical databases, and encompassing all years since the introduction of cross-linking in ophthalmology practice.

RESULTS

Corneal collagen cross-linking using UVA irradiation and riboflavin is a surgical technique that is currently being optimised, and is supported by a good amount of pre-clinical and clinical studies. These papers found show the beneficial effect of the surgery on preventing the progression of corneal ectasia, especially keratoconus, but also on pellucid marginal degeneration and keratectasia after refractive surgery. The effect of cross-linking on avoiding the occurrence of iatrogenic keratectasia when combined with a photo-ablative procedure is less clear to date. Additionally, it appears that cross-linking may have a considerable beneficial effect on controlling corneal infection caused by fungi, bacteria and amoebae. However, its effect on viral keratitis can be detrimental. The benefit on bullous keratopathy seems to be rather transient.

CONCLUSIONS

Corneal collagen cross-linking may be used with relative safety and efficacy in patients with progressive keratoconus. Its use could also be considered in patients with other corneal ectasias or with corneal infections of non-viral origin. Currently, there is still a need for more studies as regards its effect on preventing iatrogenic keratectasia.

Simultaneous versus Sequential Accelerated Corneal Collagen Cross-Linking and Wave Front Guided PRK for Treatment of Keratoconus: Objective and Subjective Evaluation

Aim. To compare objective and subjective outcome after simultaneous wave front guided (WFG) PRK and accelerated corneal cross-linking (CXL) in patients with progressive keratoconus versus sequential WFG PRK 6 months after CXL. Methods. 62 eyes with progressive keratoconus were divided into two groups; the first including 30 eyes underwent simultaneous WFG PRK with accelerated CXL. The second including 32 eyes underwent subsequent WFG PRK performed 6 months later after accelerated CXL. Visual, refractive, topographic, and aberrometric data were determined preoperatively and during 1-year follow-up period and the results compared in between the 2 studied groups. Results. All evaluated visual, refractive, and aberrometric parameters demonstrated highly significant improvement in both studied groups (all P < 0.001). A significant improvement was observed in keratometric and Q values. The improvement in all parameters was stable till the end of follow-up. Likewise, no significant difference was determined in between the 2 groups in any of recorded parameters. Subjective data revealed similarly significant improvement in both groups. Conclusions. WFG PRK and accelerated CXL is an effective and safe option to improve the vision in mild to moderate keratoconus. In one-year follow-up, there is no statistically significant difference between the simultaneous and sequential procedure.