|Year : 2018 | Volume
| Issue : 3 | Page : 174-177
Corneal collagen cross-linking as an additional step in laser in-situ keratomileusis surgery for preventing post-laser in-situ keratomileusis regression
Ahmed A Alhagaa, Nermeen M Badawi
Ophthalmology Department, Menofia University, Shebin Elkom, Menofia, Egypt
|Date of Submission||12-Jan-2018|
|Date of Acceptance||03-May-2018|
|Date of Web Publication||24-Sep-2018|
Nermeen M Badawi
FRCS Ophth. (Glasgow), Compound Lake View, 90th Street, Villa 3/1, New Cairo, Cairo 11835
Source of Support: None, Conflict of Interest: None
Aim The aim of this study was to evaluate the safety, stability, and efficacy of corneal collagen cross-linking as an additional step in laser in-situ keratomileusis (LASIK) surgery for prevention of post-LASIK regression.
Patients and methods Eyes included in this study were classified into two groups: group A consisted of 30 myopic eyes (spherical equivalent between −6.00 and −10.00 D) that underwent LASIK surgery with riboflavin application and ultraviolet light irradiation in the same sitting and group B as the control group which consisted of 30 myopic eyes (spherical equivalent between −6.00 and −10.00 D) that underwent LASIK surgery only without riboflavin application or ultraviolet light irradiation. Postoperative follow-up was at 1 day, 1 week, 1, 3, 6 months, 1, 2, and 3 years postoperatively.
Results The mean spherical equivalent at 3 years postoperatively was −0.75 D in group A in comparison with −2.75 D in group B in which the regression started significantly after 1 year postoperatively (from −0.50 to −2.75 D) with less regression (from −0.50 to −0.75 D) in group A by the end of follow-up period (P=0.002). No significant changes in topography or pachymetry were reported in the present study. In addition, no complications related to corneal collagen cross-linking were reported in comparison with the second group.
Conclusion Adjuvant use of corneal collagen cross-linking as an additional step in LASIK procedure is safe and effective in decreasing post-LASIK regression.
Keywords: cross-linking, laser in-situ keratomileusis, regression, riboflavin
|How to cite this article:|
Alhagaa AA, Badawi NM. Corneal collagen cross-linking as an additional step in laser in-situ keratomileusis surgery for preventing post-laser in-situ keratomileusis regression. Delta J Ophthalmol 2018;19:174-7
|How to cite this URL:|
Alhagaa AA, Badawi NM. Corneal collagen cross-linking as an additional step in laser in-situ keratomileusis surgery for preventing post-laser in-situ keratomileusis regression. Delta J Ophthalmol [serial online] 2018 [cited 2018 Oct 17];19:174-7. Available from: http://www.djo.eg.net/text.asp?2018/19/3/174/242146
| Introduction|| |
Post-laser in-situ keratomileusis (LASIK) regression has a bad effect on visual outcome and patient satisfaction . Corneal collagen cross-linking became a widely used technique in the treatment of keratoconus and post-LASIK ectasia . The use of corneal collagen cross-linking as an additional step in LASIK procedure can theoretically decrease the post-LASIK regression by improving corneal biomechanics which is a cornerstone in the pathophysiology of post-LASIK regression and post-LASIK ectasia .
This study aimed at evaluating the safety, stability, and efficacy of corneal collagen cross-linking as an additional step in LASIK surgery for prevention of post-LASIK regression.
| Patients and methods|| |
A written informed consent was obtained from every patient before participating in the study.
This study is a prospective study that was performed on 60 eyes of 30 patients, in the period from May 2014 to April 2017 in the Eye Sub-specialty Center, Cairo, Egypt.
The procedures followed the ethical standards of the Helsinki declaration and were approved by the Ethical Committee of Menofia University. Before any procedure, the patient signed an informed consent.
Patients with age older than 18 years with a stable refraction for at least 1 year before the procedure and a within normal preoperative pachymetry and corneal topography were included.
Any ocular pathology other than myopia and myopic astigmatism were the exclusion criteria.
Patients were classified into two groups:
Group A consisted of 30 myopic eyes (spherical equivalent between −6.00 and −10.00 D). LASIK surgery with riboflavin application and ultraviolet light irradiation in the same sitting of the LASIK surgery was performed in this group.
Group B was the control group, which consisted of 30 myopic eyes (spherical equivalent between −6.00 and −10.00 D). LASIK surgery only without riboflavin application or ultraviolet light irradiation was done in these patients.
All eyes included in this study were subjected to detailed preoperative assessment which included uncorrected visual acuity (UCVA), best-corrected visual acuity, manifest and cycloplegic refraction, pachymetry, and corneal topography evaluation by Pentacam (Allegro Oculyzer; Wavelight Laser Technology AG, Wetzlar, Germany), meticulous slit-lamp examination and dilated fundus examination.
All patients underwent standard optimized LASIK treatment using Allgretto Ex-500 LASIK machine (Wavelight Laser Technology AG).
All patients had topical anesthesia with benoxinate hydrochloride 0.4% (Benox, Eipico, Cairo, Egypt) eye drops. All flaps were created with MORIA M2 microkeratome (Moria Inc., Paris, France) with the 90 μm head. The MORIA microkeratome was adjusted on speed 1 for all eyes. The flap creation was done successfully in all eyes and the stromal bed was dried before excimer laser photoablation.
In group A, once excimer laser photoablation was completed, the flap was repositioned. Then riboflavin drops (0.1% solution, 10 mg riboflavin-5-phosphate in 10 ml dextran −500, 20% solution) (Ricrolin; Sooft Italia, Montegiorgio, Italy) were instilled on the flap every 2 min alternating with a drop of balanced salt solution for 30 min. Then ultraviolet light was applied with a power of 9 mW/cm2 for 10 min (Avedro Salient Med., Toronto, Ontario, Canada). At the end of the procedure, the corneal flap was checked for proper positioning.
In Group B, once excimer laser photoablation was completed, and the flap was correctly repositioned without riboflavin application or ultraviolet light irradiation.
Postoperative follow-up was performed for both groups at 1 day, 1 week, 1, 3, 6 months, 1, 2, and 3 years. Evaluation was done using the same machines used in the preoperative evaluation.
Data were collected, tabulated, and analyzed using the paired t test.
| Results|| |
The patients in group A were 10 females and five males, and their age ranged from 20 to 32 years, with a mean of 25±4.2 years, whereas that of group B were 12 females and three males, and their age ranged from 20 to 31 years, with a mean of 24±4.4 years.
The mean ablation depth in group A was 76.00±12.40 μm, whereas that of group B was 75.82±11.70 μm, with a statistically insignificant difference (P=1.2).
There were no intraoperative or postoperative complications related to LASIK technique in both groups. In addition, no complications related to cross-linking were reported in group A.
The mean UCVA (in logarithm minimum angle of resolution units), by the end of 3 months, was 0.2±0.2 in group A and 0.2±0.3 in group B, with no statistically significant difference between the two groups (P>0.05). By the end of the first year, there were no changes in the mean UCVA in group A whereas that of group B became 0.4±0.2. These values changed to 0.3±0.2 in group A and 0.6±0.3 in group B by the end of the follow-up period (P<0.05), with a statistically significant change in group B in comparison with group A ([Table 1]).
|Table 1 Comparison between the mean preoperative and postoperative visual acuity (in logarithm minimum angle of resolution) in both groups|
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By the end of the third month, the spherical equivalent was −0.50±0.50 D in group A and −0.50±0.75 D in group B, with no statistically significant difference between the two groups (P>0.05). By the end of the first year, no changes in the mean spherical equivalent were noted in group A whereas that of group B became −2.00±0.75 D. These values changed to −0.75±0.50 D in group A and −2.75±1.00 D in group B by the end of the follow-up period (P=0.002), which means that myopic regression was statistically significantly lower in group A in comparison with group B ([Table 1]).
There was no statistically significant difference between group A and group B regarding all topographic indices at preoperative and each postoperative follow-up visit ([Table 2] and [Table 3]; P>0.05).
Stability of refraction, visual acuity, and topographic indices supports the safety, stability, and predictability of cross-linking.
There were no dropouts throughout the study duration of 3 years.
| Discussion|| |
The main finding of the current study was to prove that adjuvant use of corneal collagen cross-linking with LASIK was a safe technique even with a relatively long-term follow-up period. No complications were reported intraoperatively related to LASIK or cross-linking, with similar conclusions by Kanellopoulos  and Celik et al. , who reported early stromal haze after the cross-linking technique but stated that its effect on visual outcome was insignificant. Similar safety findings were reported by Hafezi et al.  while using corneal collagen cross-linking in post-LASIK ectasia.
Regarding the effect on the accuracy of myopic correction, it was noted that the mean myopic spherical equivalent for both groups was −0.50 D at 3 months postoperatively which indicates that the adjuvant use of corneal collagen cross-linking with LASIK has no effect on the accuracy of myopic correction. Kanellopoulos  and Celik et al.  reached similar findings.
Mi et al.  conducted their study on an organ culture model and reached the conclusion that apart from its effect on corneal biomechanical properties, adjuvant corneal collagen cross-linking doubles the adhesion of the LASIK flap itself, which may have additional benefits to regression, which supports the results of the current study in which the mean myopic spherical equivalent in group A was −0.50 D at 3 months and −0.75 D at 3 years with a change of −0.25 D over 3 years, whereas that of group B was −0.50 D at 3 months and −2.75 D at 3 years, with a change of −2.25 D, which was a statistically significant regression in comparison with group A.Kampik et al.  reported that there were no significant topographic changes after corneal collagen cross-linking, and similar findings were demonstrated in the present study.
| Conclusion|| |
No adverse effects were encountered during this study. We advise to do further research to study the role of corneal collagen cross-linking as an additional step in LASIK surgery to decrease postoperative regression in myopic LASIK and to decrease the risk of post-LASIK ectasia.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3]