|Year : 2022 | Volume
| Issue : 2 | Page : 49-53
Evaluation of long-term outcomes of simultaneous corneal collagen cross-linking and femtosecond laser-assisted intracorneal ring segment implantation for keratoconus
Khaled A.M Elbassiouny1, Tarek A Hafez2, Ihab A Osman2, Ahmed A Elmassry2
1 Department of Ophthalmology, Alexandria General Ophthalmology Hospital, Alexandria, Egypt
2 Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt
|Date of Submission||24-Sep-2021|
|Date of Acceptance||17-Oct-2021|
|Date of Web Publication||08-Jul-2022|
MD, PHD, MRCS Ed Khaled A.M Elbassiouny
Department of Ophthalmology, 202 Elmoaameron B Tower, Hilton Street, Somouha, Alexandria, 21684
Source of Support: None, Conflict of Interest: None
Background Intracorneal ring segment (ICRS) implantation in combination with corneal collagen cross-linking (CXL) has shown promising results in improving the visual acuity and reducing refractive errors, but long-term results are lacking.
Aim To evaluate the long-term outcomes (>5 years) of simultaneous CXL and femtosecond laser-assisted intracorneal stromal ring segment implantation for management of keratoconus.
Design This was a noncomparative, noncontrolled retrospective single-center study.
Patients and methods The study included 50 eyes of 37 patients with keratoconus who underwent simultaneous CXL and ICRS implantation and were followed up for at least 5 years regarding visual acuity, refraction, and corneal imaging.
Results Best-corrected visual acuity showed statistically significant improvement, with mean changed from 1.07±0.41 to 0.40±0.30 LogMAR. The results showed significant improvement also after 5 years. The spherical equivalent also was significantly improved from a mean of −4.61±4.37 D to a mean of −1.41±−1.49 D. Keratometric readings also showed improvement of both K1 and K2. The mean K1 improved from a mean of 49.6±6.76–47.78±6.17 D, and the mean K2 improved from 55.04±7.34 to 52.67±7.38. The results were stable, with no statistically significant change after 5 years.
Conclusions Simultaneous CXL and femtosecond laser-assisted ICRS is effective and stable for both visual outcome and refraction in patients with keratoconus.
Keywords: cornea, cross-linking, ectasia, intrastromal corneal ring segment, keratoconus
|How to cite this article:|
Elbassiouny KA, Hafez TA, Osman IA, Elmassry AA. Evaluation of long-term outcomes of simultaneous corneal collagen cross-linking and femtosecond laser-assisted intracorneal ring segment implantation for keratoconus. J Egypt Ophthalmol Soc 2022;115:49-53
|How to cite this URL:|
Elbassiouny KA, Hafez TA, Osman IA, Elmassry AA. Evaluation of long-term outcomes of simultaneous corneal collagen cross-linking and femtosecond laser-assisted intracorneal ring segment implantation for keratoconus. J Egypt Ophthalmol Soc [serial online] 2022 [cited 2022 Sep 28];115:49-53. Available from: http://www.jeos.eg.net/text.asp?2022/115/2/49/350259
| Introduction|| |
Intrastromal corneal ring segments (ICRSs) are small pieces of synthetic material implanted in the deep corneal stroma . It was first introduced for the treatment of myopia . Its use in inducing topographic regularity and improving both visual acuity and refraction is considered to be a substantial evolution in the management of keratoconus .
The stability of keratoconus following ICRS alone remains a debate among keratoconus experts . The stability of results of ICRS in treatment in keratoconus on long-term follow-up is still not established. It needs more studies with longer follow-up to prove .
| Patients and methods|| |
The study is a noncomparative noncontrolled retrospective, single-center study aiming to evaluate long-term outcomes (>5 years) of simultaneous collagen cross-linking (CXL) and ICRS in management of keratoconus. It was approved by the Faculty of Medicine Ethics Review board and followed the Declaration of Helsinki tenets. We revised the data records of 50 eyes of 37 patients with keratoconus who had simultaneous CXL and ICRS implantation between January 2015 and June 2016 by a single experienced surgeon and followed them up for at least 5 years. Patients aged between 18 and 40 years with clear central cornea having best-corrected visual acuity (BCVA) better than 6/60 were included. Patients with severe keratoconus, corneal thickness at the site of insertion less than 400, corneal haze or opacity, previous ocular disease trauma or intraocular surgery, systemic collagen disorders, acute hydrops, ocular infection, and severe atopy were excluded. Informed consent was signed before the procedure.
Data were collected from preoperative records of the patients; detailed ocular and medical history, complete ophthalmic examination, including uncorrected visual acuity (UCVA), and BCVA, both measured by a decimal fraction and transformed into LogMAR for statistical analysis, also slit lamp and fundus examination.
Imaging was done using Scheimpflug imaging with Pentacam (Allegro Oculyzer, WaveLight AG, Germany) and anterior segment OCT (Visante Carl Zeiss Meditec Inc., Dublin, California, USA).
All cases were subjected to Femto-assisted ICR implantation followed by CXL done in the same session. The SI-5 design Keraring was used in our study with optical zone 5.0 mm and triangular cross-section, manufactured from polymethyl methacrylate. The number of Keraring segments depended upon the Keraring nomogram based mainly on the type and the position of the keratoconus cone, mean K readings, central corneal thickness, and refractive status of the eye.
Careful placement and inspection of cone were carried out to ensure proper centration. Ultrafast 12 seconds. Femtosecond laser (VisuMax, Carl Zeiss Meditec Inc.) was used to create the tunnels, 80% of the depth, and incision was done using wavelength of about 1040 nm, spot size 1 µm, and laser frequency of 500 kHz.
Incisions were made on the steepest axis at corneal topography or on the comatic axis. Each tunnel had an inner diameter of about 4.95 mm and an outer diameter of 6.4 mm. Energy used was less than 1 mJ with procedure time of 12 s for femto laser to create all tunnels and incisions.
The KeraRing (Mediphacos, Belo Horizonte, Brazil) was inserted under strict aseptic technique. Centration of the ring segments in the middle of each tunnel was done. In case of single-segment use, it was inserted inferiorly, though the use of two segments necessitated that the largest one to be inferior.
After the implantation process, accelerated Epi-off CXL was started. Riboflavin solution 0.1% (Peschke M, Switzerland) was applied for 30 min. The device used for irradiation was CCL-Vario cross-linking device to apply UVA with wavelength 370 nm and irradiance of 18 mW/cm2 for 5 min (total energy of 5400 mJ) at a distance of 5±0.5 cm.
Postoperative treatment and follow-up
Topical antibiotics, moxifloxacin (Vigamox), were given every 1 h during the first 24 h and then five times per day for 10 days only. Steroids in the form of prednisolone (Predforte) were given every 1 h during the first 24 h and then decreased to five times per day for 1 week and then gradually tapered over 1 month. Artificial tears eye drops were given every 1 h during the first day and then every 4 h for at least 1 month. Analgesics were prescribed to alleviate pain after CXL. Patients were instructed to avoid eye rubbing. Contact lenses were removed between 3 and 5 days, once epithelial healing was complete.
Every patient was followed up, and data were recorded in the patient’s file at the first postoperative day, 1 week, 1 month, 3 months, then every year after the procedure for at least 5 years. During each follow-up, complete ophthalmic examination, UCVA, BCVA, autorefraction, manifest refraction, and Pentacam were performed. Anterior segment OCT was done only once at 1 week postoperatively to detect the demarcation line of CXL and ICR segment depth and position.
| Results|| |
A total of 50 eyes of 37 patients were included. There were 16 (43.2%) males and 21 (56.8%) females, with age ranged from 18.94 to 37.71 years, with a mean age of 28.04±5.38 years. In 41 eyes, two ring segments were inserted, whereas in nine eyes, a single ring segment was inserted based upon the Keraring nomograms.
Mean preoperative UCVA was 1.07±0.41 LogMAR, whereas 3 months after the procedure, it was 0.41±0.29 LogMAR. UCVA showed statistically significant improvement (P<0.001). After 5 years, the mean UCVA was 0.40±0.30 LogMAR. There was no statistically significant difference between UCVA at 3 months and 5 years (P3=0.317), but there appeared to be a statistically significant difference between results after 5 years and preoperative UCVA (P2<0.001).
Mean preoperative BCVA was 1.07±0.41 LogMAR. After 3 months, it showed statistically significant improvement to 0.18±0.17 LogMAR. The mean BCVA also showed statistically significant improvement after 5 years to 0.40±0.30 LogMAR (P<0.001) [Table 1].
|Table 1 Comparison between the different studied periods according to uncorrected visual acuity and best-corrected visual acuity in LogMAR (N=50)|
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Mean preoperative cylindrical error was −6.36±1.90 D. A statistically significant improvement after 3 months and 5 years was noted, with a mean of −2.11±1.26 and −2.16±−1.33 D, respectively. The results were stable between 3 months and 5 years, with no significant change.
The mean preoperative spherical equivalent (SE) was −4.61±4.37 D. It showed statistically significant improvement after 3 months to be −1.47±1.69 D. Mean SE at 5-year follow-up was −1.41±−1.49 D. There was a statistically significant change between 5 years and preoperative SE but no statistically significant difference between 3 months postoperative results and 5-year follow-up [Figure 1].
|Figure 1 Comparison between the different studied periods according to refraction manifest sphere, cylinder, and spherical equivalent (N=50).|
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The mean preoperative keratometric readings in flat meridian (K1) was 49.6±6.76 D, and 3-month postoperative K1 was 47.74±6.39 D. The mean 5-year postoperative K1 was 47.78±6.17 D. Results indicated a statistically significant decrease of K1 after 3 months and 5 years in comparison with preoperative data, whereas the change of K1 values between 3 months and 5 years was not statistically significant.
Mean preoperative keratometric readings in steep meridian (K2) were 55.04±7.34 D. Mean 3-month postoperative K2 was 53.74±8.30 D, with no statistically significant change, whereas mean 5-year postoperative K2 was 52.67±7.38 D. The results indicated a statistically significant decrease of K1 between 5 years and both preoperative results and 3 months postoperatively. No operative or postoperative complications were reported in patients’ records [Table 2].
|Table 2 Comparison between the different studied periods according to K1 and K2 (N=50)|
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| Discussion|| |
Management of keratoconus in terms of stabilization of the condition, prevention of progression, and correction of current refractive error is a common challenge. CXL has proved efficacy in the prevention of progression of KC, with long-term results (>10 years) being published and long-term stability of the condition being stated . Correction of refractive error in cases of keratoconus is still debatable. Many studies have investigated the use of ICRS implantation to flatten the central cornea and improve UCVA, but long-term stability and efficacy are still issues that need to be proven .
The current study demonstrated statistically significant improvement in both UCVA and BCVA after 3 months. Long-term follow-up (>5 years) showed also statistically significant improvement than preoperative results. The postoperative BCVA continued to show significant improvement after 5 years, whereas UCVA was stable, with no statistically significant change.
Improvement in both UCVA and BCVA had been proven by many authors. Utine et al.  studied the effect of ICRS implantation into 42 eyes and found significant improvement of both UCVA and BCVA after 3-month follow-up. Ibrahim et al.  also reported statistically significant improvement of both UCVA and BCVA in a cohort of 160 eyes after 6 months. Saleem et al.  demonstrated the results of 36-month follow-up after CXL combined with ICRS (described as CXL plus) and found improvement of all patients with two or more lines gained postoperatively .
Both cylindrical error and SE showed statistically significant improvement after 3 months and 5 years. The results were stable between 3 months and 5 years, with no statistically significant change. Several studies reported significant improvement in both preoperative astigmatism and SE. Utine et al.  studied the effect of Keraring ICRS in combination with CXL and found that postoperative changes in both UCVA and BCVA were correlated with the postoperative changes in SE and cylinder. A retrospective study by Rocha et al.  was performed on 55 eyes of 46 patients who received ICRS implantation, followed by CXL and photorefractive keratectomy combination treatment, and found statistically significant improvements of sphere and cylinder at 6 months compared with baseline . Another study by Rocha et al.  compared the results of two different designs of ICRS, namely, Kerarings and Ferrara rings, and concluded that both manufacturers’ nomograms resulted in statistically significant improvement in most of the parameters analyzed including SE and cylindrical error. A literature review was performed by Giacomin et al.,  including an overview of ICRS implantation to improve visual outcome in terms of safety, predictability, and efficacy and its combination with other techniques including CXL. He found that ICRS implantation is effective and safe in most cases, including combined procedures. If eyes were selected properly, it helps improving vision and refraction for those with keratoconus. The improvement in both visual outcome and refractive error observed in our study could be explained by the flattening effect of implanted Keraring, and thus reduction of myopia, astigmatism, and SE in patients with keratoconus .
In our study, keratometric readings in flat meridian (K1) and steep meridian (K2) showed statistically significant improvement after 3 months and 5 years. Results were stable with no statistically significant change between postoperative periods. Saleem et al.  showed similar results with statistically significant improvement in postoperative K readings in both flat and steep meridian (K1 and K2) after 3 years of follow-up. One of the interesting studies was carried out by El Awady et al. , who evaluated the effect of CXL in 21 keratoconus eyes of 13 patients with Keraring implantation. He found statistically significant improvement in both visual outcome (UCVA and BCVA) and refractive outcome (cylindrical error and SE) after Keraring implantation with a slight improvement in both parameters after CXL was done later on, whereas keratometric readings showed statistically significant improvement after Keraring implantation and also after CXL, and thus, CXL added to flattening effect resulted from ICRS implantation. A comprehensive meta-analysis of 120 published articles was done by Hashemi et al.  to compare surgical sequences of combined ICRS implantation and CXL in keratoconus and corneal ectasia and concluded that simultaneous ICRS implantation and CXL may provide better outcomes than staged techniques for improving the corneal shape.
| Conclusion|| |
The simultaneous use of corneal CXL and femtosecond laser-assisted ICRS seems to be effective and stable for both visual outcome and refraction in patients with keratoconus.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interset.
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[Table 1], [Table 2]