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ORIGINAL ARTICLE
Adv Biomed Res 2016,  5:194

Short-term result of collagen crosslinking in pellucid marginal degeneration


Department of Ophthalmology, Isfahan University of Medical Sciences, Isfahan, Iran

Date of Submission05-Apr-2014
Date of Acceptance27-Aug-2014
Date of Web Publication27-Dec-2016

Correspondence Address:
Dr. Alireza Peyman
Department of Ophthalmology, Feiz Hospital, Isfahan University of Medical Sciences, Isfahan
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/2277-9175.192732

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  Abstract 

Background: To evaluate effectiveness of collagen crosslinking in pellucid marginal degeneration patients.
Materials and Methods: Twenty-one eyes of 15 patients treated by collagen crosslinking were enrolled in our non-controlled clinical trial study. After evaluation of patients about inclusion and exclusion criteria, preoperative examination was done and then patients underwent CXL procedure and seen 6 months after surgery for postoperative examinations.
Results: Mean preoperative LogMar uncorrected visual acuity (UCVA) was 0.63 (SE = 0.08), and mean preoperative LogMar BCVA was 0.26 (SE = 0.04). At 6 months postoperative, mean LogMar UCVA was 0.59 (SE = 0.06) and mean LogMar BCVA was 0.19 (SE = 0.02). The non-parametric test (Wilcoxon) showed reduction of LogMar BCVA was significant (P value = 0.02), but reduction of LogMar UCVA was not significant (P value = 0.5). Mean preoperative K1 was 42.23 ± 2.85 and mean postoperative K1 significantly decreased to 41.68 ± 2.44 (P value = 0.008). Also, mean preoperative K2 was 48.39 ± 2.37 and mean postoperative K2 significantly reduced to 47.64 ± 2.16 (P value = 0.002).
Conclusion: Most remarkable findings of our study were improvement of visual acuity and reduction K1 and K2 parameters. Stability of other values and absence of detectable change after study period implies halting of the progression of the disease. We suggest CXL can be useful for management of PMD, but we need more studies with larger sample size and longer follow up.

Keywords: Collagen crosslinking, cornea ectasia, pellucid marginal degeneration


How to cite this article:
Mamoosa B, Razmjoo H, Peyman A, Ashtari A, Ghafouri I, Moghaddam AG. Short-term result of collagen crosslinking in pellucid marginal degeneration. Adv Biomed Res 2016;5:194

How to cite this URL:
Mamoosa B, Razmjoo H, Peyman A, Ashtari A, Ghafouri I, Moghaddam AG. Short-term result of collagen crosslinking in pellucid marginal degeneration. Adv Biomed Res [serial online] 2016 [cited 2022 Nov 29];5:194. Available from: https://www.advbiores.net/text.asp?2016/5/1/194/192732


  Introduction Top


Pellucid marginal degeneration (PMD) is a progressive, non-inflammatory ectatic corneal disease. It is characterized by thinning in the periphery of the cornea. The inferior cornea exhibits a peripheral band of thinning. There is usually high against-rule astigmatism. Computerized topography will show a classic butterfly appearance. Proposed treatments are spectacle correction, rigid gas-permeable contact lenses, and intra stromal corneal ring segments. In advanced cases, lamellar or penetrating keratoplasty is the latest treatment option.[1],[2],[3]

Corneal collagen crosslinking (CXL) is a new therapeutic technique that stabilizes the corneal mechanical properties and prevents progression of ectatic corneal condition, penetrating keratoplasty and its complications. In this technique the photosensitizer riboflavin (vitamin B2) and ultraviolet A is used to induce specific chemical reactions in the corneal stroma. This option has been suggested as useful for management of pellucid marginal degeneration.[4],[5],[6],[7]

Spadea [8] reported the results of collagen crosslinking in a patient affected by PMD. He concluded CXL is a safe tool in management of PMD and improves some parameters in advanced stages of the disease.

Accordingly, we initiated a CXL study in patients with PMD and evaluated refractive, topographic and tomographic parameters after CXL.


  Materials and Methods Top


Twenty-one eyes of 15 patients treated by collagen crosslinking were enrolled in our non-controlled clinical trial study. The inclusion criteria were diagnosis of mild to moderate stage PMD and having a minimum thickness of 400 µm at the thinnest part of cornea. The exclusion criteria were history of herpetic keratitis; use of rigid contact lenses; history of autoimmune disease and history of eye surgery. Preoperative examination consisted of slit lamp microscopy, corneal topography/tomography and visual acuity/manifest refraction. After primary evaluation, patients underwent collagen crosslinking operation. The stroma was saturated by 0.1% riboflavin-5-phosphate and 20% dextran solution as one drop every 3 minutes. After stroma saturation, ultraviolet A light irradiated to the surface of cornea (6-8 mm) for 30 minutes. Patients were seen 6 months after surgery for postoperative examinations.

SPSS 16 software was used to analysis of our data. We used non-parametric test (Wilcoxon) because of low sample size (lower than 30).


  Results Top


Twenty-two eyes of 16 patients were enrolled in our study. One of patients excluded from our study because of severity and progression of PMD and underwent corneal transplantation. Mean age of patients was 31.38 ± 6.63 years. Nine of the patients were males and six of them were females.

Mean preoperative LogMar uncorrected visual acuity (UCVA) was 0.63 (SE = 0.08), and mean preoperative LogMar BCVA was 0.26 (SE = 0.04). At 6 months postoperative, mean LogMar UCVA was 0.59 (SE = 0.06) and mean LogMar BCVA was 0.19 (SE = 0.02). The non-parametric test (Wilcoxon) showed reduction of LogMar BCVA was significant (P value = 0.02), but reduction of LogMar UCVA was not significant (P value = 0.5).

Mean preoperative spherical equivalent refraction was –3.09 ± 0.59, with a mean sphere of 0.11 ± 0.48 and mean of cylinder was –6.42 ± 0.51. Postoperative spherical equivalent refraction was –3.29 ± 0.51, with a mean sphere of –0.34 ± 0.51 and mean cylinder of –5.9 ± 0.35. We found no significant differences between pre and postoperative spherical equivalent refraction (P value = 0.32), although there was a significant difference between pre and postoperative sphere (P value = 0.01). Also, our finding showed that defocus equivalent refractory errors were 6.4 ± 3.15 and 6.31 ± 2.52 before and after surgery. Defocus equivalent was not significantly changed after surgery (P value = 0.76)

Pre and post-op corneal plane refractive cylinder was 5.94 ± 2.03 and 5.46±0.49 (P value = 0.07). Pre and post-op keratometric astigmatism was 6.15 ± 3.1 and 5.95 ± 2.85 (P value = 0.38).

Our results about simulated keratometry values (K1 for minimum and K2 for maximum) demonstrated that, mean preoperative K1 was 42.23 ± 2.85 and mean postoperative K1 significantly decreased to 41.68 ± 2.44 (P value = 0.008). Also, mean preoperative K2 was 48.39 ± 2.37 and mean postoperative K2 significantly reduced to 47.64 ± 2.16 (P value = 0.002).

Mean preoperative thickness of thinnest point of cornea was 471.19 ± 33.73 µm and mean postoperative thickness of thinnest point of cornea was 453.61 ± 45.32. Our finding demonstrated thickness of thinnest point of cornea was significantly decreased (P = 0.001).

Mean surgically induced astigmatism of refractive error as calculated by analyzing of vectors was 1.34 ± 0.94 diopters. Astigmatic correction indices calculated by Alpins method;[9] mean flattening effect was 0.57 ± 1.14 diopter. Mean surgically induced astigmatism of keratometric values was 1.05 ± 0.74 diopter and 0.24 ± 1.02 diopter of flattening effect at the steep axis.

[Table 1] provides a summary of the comparison of the pre and postoperative variables.
Table 1: Comparison of the pre and postoperative variables

Click here to view



  Discussion Top


PMD is an ectatic disorder of the cornea that affects patient's life because of poor quality of vision produced by associated against the rule astigmatism.[10] CXL as a new and less invasive therapeutic method was adopted to arrest the progression of ectatic characteristic of PMD.[6],[8],[11] We evaluated visual acuity, refractive errors and topographic outcomes 6 months after CXL in PMD patients. Our findings demonstrated at 6 months after CXL, the procedure lead to cornea flattening by significant reduction of K1 and K2 (P < 0.05). Also, best corrected visual acuity (BCVA) has significantly improved. Results showed no significantly change in astigmatic refractive data (P > 0.05) but mean refraction showed a significant decrease in sphere (P < 0.05).

Usefulness of CXL in ectatic disorders especially like keratoconus has been proved in many studies and we know CXL make cornea rigid and it can be useful in management of PMD either. There is just some case report that suggested CXL can be considered as a new therapeutic option for PMD.

Tuffaha, et al.[12] presented a case of progressive PMD treated with CXL after a previous unsuccessful implantation of intra corneal segments. After 1 year, an increase in corneal biomechanical properties accompanied by improvement in corrected visual acuity was observed. This case report showed potential applicability of CXL in a cornea with a progressive PMD, allowing a visual improvement in visual acuity and biomechanical properties of the cornea.

Also Kymionis, et al.[3] present a case of progressive PMD treated by simultaneously photorefractive keratotomy and CXL. Twelve months postoperatively uncorrected and best corrected visual acuity improved. Also corneal topography revealed a significant improvement in the eye.

Findings of these case reports totally support our results. Our findings showed improvement of visual acuity especially BCVA and significant flattening of cornea.

Also, Stojanovic, et al.[13] evaluated a combination of topography-guided custom ablation and CXL in a single procedure for the treatment of keratectasia. Twelve eyes of 12 patients with keratectasia enrolled in their study and treated with topography-guided custom ablation and CXL. Results of 1 year after surgery revealed improvement of visual acuity and reduction of mean astigmatism and keratometry asymmetry. They concluded this method may postpone or eliminate the need for corneal transplantation in suitable cases with keratectasia. Unlike this study we just enrolled PMD patients in our study treated with CXL only, but results of this study can supports ours.

One limitation of our study was low sample size. Also longer follow-up is necessary to evaluate the outcomes of this procedure. Continued stability of the good visual outcome and lack of progression of corneal ectasia in PMD patients may make this procedure an effective alternative for other invasive procedure.


  Conclusion Top


Most remarkable findings of our study were improvement of visual acuity and reduction simK parameters. Stability of other values and absence of detectable change after study period imply halting of the progression of the disease.

We suggest CXL can be useful for management of PMD, but we need more studies with larger sample size and longer follow up.

 
  References Top

1.
Jinabhai A, Radhakrishnan H, O'Donnell C. Pellucid corneal marginal degeneration: A review. Contact Lens Anterior Eye 2011;34:56-63.  Back to cited text no. 1
    
2.
Kubaloglu A, Sari ES, Cinar Y, Koytak A, Kurnaz E, Piñero DP, et al. A single 210-degree arc length intrastromal corneal ring implantation for the management of pellucid marginal corneal degeneration. Am J Ophthalmol 2010;150:185-92. e1.  Back to cited text no. 2
    
3.
Kymionis GD, Karavitaki AE, Kounis GA, Portaliou DM, Yoo SH, Pallikaris IG. Management of pellucid marginal corneal degeneration with simultaneous customized photorefractive keratectomy and collagen crosslinking. J Cataract Refract Surg 2009;35:1298-301.  Back to cited text no. 3
    
4.
Gkika M, Labiris G, Kozobolis V. Corneal collagen cross-linking using riboflavin and ultraviolet-A irradiation: A review of clinical and experimental studies. Int Ophthalmol 2011;31:309-19.  Back to cited text no. 4
    
5.
Jankov Ii MR, Jovanovic V, Delevic S, Coskunseven E. Corneal collagen cross-linking outcomes: Review. Open Ophthalmol J 2011;5:19-20.  Back to cited text no. 5
    
6.
Koller T, Pajic B, Vinciguerra P, Seiler T. Flattening of the cornea after collagen crosslinking for keratoconus. J Cataract Refract Surg 2011;37:1488-92.  Back to cited text no. 6
    
7.
Snibson GR. Collagen cross-linking: A new treatment paradigm in corneal disease-a review. Clin Experiment Ophthalmol 2010;38:141-53.  Back to cited text no. 7
    
8.
Spadea L. Corneal collagen cross-linking with riboflavin and UVA irradiation in pellucid marginal degeneration. J Refract Surg 2010;26:375-7.  Back to cited text no. 8
    
9.
Alpins NA. A new method of analyzing vectors for changes in astigmatism. J Cataract Refract Surg 1993;19:524-33.  Back to cited text no. 9
    
10.
Stein R, Stein R, Honours B. Corneal collagen crosslinking: A major breakthrough in the management of keratoconus, pellucid marginal degeneration, and ectasia after LASIK. 2011;9:2.  Back to cited text no. 10
    
11.
Koller T, Schumacher S, Fankhauser F 2nd, Seiler T. Riboflavin/ultraviolet a crosslinking of the paracentral cornea. Cornea 2013;32:165-8.  Back to cited text no. 11
    
12.
Tuffaha BT, Alio JL, Piñero DP. Cross-linking for the management of pellucid marginal degeneration in a case of an unsuccessful implantation of intracorneal ring segments. IGKECD 2012;1:120-4.  Back to cited text no. 12
    
13.
Stojanovic A, Zhang J, Chen X, Nitter TA, Chen S, Wang Q. Topography-guided transepithelial surface ablation followed by corneal collagen cross-linking performed in a single combined procedure for the treatment of keratoconus and pellucid marginal degeneration. J Refract Surg 2010;26:145-52.  Back to cited text no. 13
    



 
 
    Tables

  [Table 1]


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