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ORIGINAL ARTICLE
Year : 2015  |  Volume : 7  |  Issue : 2  |  Page : 45-47

Visual and refractive outcome of MyoRing implantation in Sudanese keratoconus patients


1 Department of Contact Lenses, Faculty of Optometry and Visual Science, Al-Neelain University, Khartoum, Sudan
2 Department of Ophthalmology, Faculty of Medicine, Al-Neelain University, Khartoum, Sudan

Date of Web Publication12-Nov-2015

Correspondence Address:
Mustafa Abdu
Department of Contact Lenses, Faculty of Optometry and Visual Science, Al-Neelain University, Khartoum
Sudan
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DOI: 10.4103/1858-540X.169435

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  Abstract 

Aim: This study aimed to evaluate the visual and refractive outcome of MyoRing implantation in patients with keratoconus. Materials and Methods: A total of 8 eyes from 8 patients who consecutively underwent MyoRing implantation were studied. The main parameters evaluated included keratometry readings, refractive status, and visual acuity. Clinical data were evaluated preoperatively and 3 months postoperation. Results: A statistically significant flattening of corneal contours and significant improvement of the spherical equivalent of refraction were noted 3 months after surgery with P values of <0.001 and 0.006, respectively. Significant improvement was also detected in unaided postoperative visual acuity compared with preoperative unaided (P < 0.001) and corrected visual acuity (P = 0.002). Conclusion: MyoRing implantation allows a significant reduction of myopia and astigmatic refractive errors resulting from keratoconus because of the corneal flattening induced, which significantly contributes to the improved visual outcomes.

Keywords: Flattening, keratoconus, MyoRing, visual outcome


How to cite this article:
Abdu M, Binnawi KH, Ahmed G. Visual and refractive outcome of MyoRing implantation in Sudanese keratoconus patients. Sudanese J Ophthalmol 2015;7:45-7

How to cite this URL:
Abdu M, Binnawi KH, Ahmed G. Visual and refractive outcome of MyoRing implantation in Sudanese keratoconus patients. Sudanese J Ophthalmol [serial online] 2015 [cited 2021 Jun 19];7:45-7. Available from: https://www.sjopthal.net/text.asp?2015/7/2/45/169435


  Introduction Top


Keratoconus is one of the most common corneal ectasia in which progressive corneal thinning and protrusion occurs. [1] In keratoconus and with the progression of the disease, cornea assumes an irregular conical shape. [2] However, corneal remodeling is the concept on which incomplete intrastromal corneal ring segment and complete intracorneal ring implantations were proposed. [3],[4],[5]

The complete intrastromal ring, MyoRing (Dioptex, GmbH, Linz, Austria), is a new effective technique in the management of keratoconus as reported by recent studies. [5],[6],[7],[8],[9] Few studies were carried on the outcome of this new operation. Alio et al. implanted 12 eyes of corneal ectasia with MyoRing. Their study concluded that the new technology allows a significant reduction of the high myopic errors because of the induced significant central flattening of the cornea. [5] Another study by Jabbarvand et al. also reported significant improvement in the visual and refractive status of their subject postoperation. The same study also found stability on corneal contours and refraction after 3 months postoperation. [8]

The full ring procedure is not yet widely used and evaluated. This study aimed to highlight the visual and refractive outcomes of the first patients who underwent this operation consecutively.


  Materials and methods Top


This study involving clinical data of all patients underwent continuous intracorneal ring implantation (MyoRing) at Sudan Eye Centre, Khartoum, Sudan, from December 2014 to June 2015.

The parameters reviewed were patients' demographics (age and gender), general and ocular health, keratometric readings (steepest, flattest, and mean), refractive status, visual acuity and central corneal thickness (CCT). Clinical data were reviewed preoperatively and 3 months postoperation. For statistical analysis decimal, visual acuity values were converted to logMAR. Classification of keratoconus was done following Amsler-Krumeich scale. [10]

Results were evaluated using statistical analysis software (IBM SPSS 20, IBM Corp., Armonk, NY). Descriptive statistics were carried out for all study parameters. Paired sample t-test was used to evaluate the refractive outcome of the surgery comparing pre- to post-operative data. Statistical significant was taken as the P < 0.05.


  Results Top


0 Demographic profile of study subjects

A total of 8 patients (8 eyes) were included in this study. Males/females ratio was 1:3. Mean age of patients was 24.00 ± 7.45 years (range: 15-37 years).

All patients were diagnosed as bilateral keratoconus. According to Amsler-Krumeich classification scale, [10] 1 patient (12.5%) was categorized as mild keratoconus, whereas 6 (75%) patients were classified as moderate and only one (12.5%) was classified as severe keratoconus. [Table 1] shows the clinical data of study subjects.
Table 1: Clinical data of the study patients

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Refractive and visual outcome

Paired sample t-test was used to compare between preoperative and postoperative corneal topography. The test showed significant flattening of corneal contours after 3 months from the surgery, t (7) = 7.26, P < 0.001. However, the test also showed significant flattening changes on the steepest and flattest keratometric readings with P values of <0.001 and 0.007, respectively. [Figure 1] illustrates mean keratometric readings before and after the surgery.
Figure 1: Means (±standard deviation) of keratometric readings before and after MyoRing implantation

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Paired sample t-test was used to compare the refractive status before and after the surgery. The test showed significant improvement of spherical equivalent (SE) of refraction postoperatively, t (7) = 3.84, P = 0.006. The test also showed significant improvement in spherical and cylindrical elements of refraction postsurgery with P values of 0.03 and 0.02, respectively.

Regarding visual outcomes, paired sample t-test showed significant improvement in unaided postoperative visual acuity compared with preoperative unaided and spectacle visual acuity with P values of P < 0.001 and P = 0.002.

Central corneal thickness

In term of CCT, the t-test showed no significant difference between mean preoperative measures (426.50 ± 54.53) and mean postoperative measures (422.33 ± 28.69), t (7) = 0.37, P = 0.72.

No intra-operative or postoperative complications were seen.


  Discussion Top


Several management procedures including optical and surgical options were proposed to control keratoconus. Continuous intracorneal ring implantation was recently proposed and also not yet widely evaluated.

Results from this study showed significant flattening of corneal curvature postsurgery. This reduction of corneal steepening was calculated to be around 9.12 D, 11.26 D and 9.44 D for mean keratometric readings, steepest K reading, and flattest K reading respectively. These findings were typically in agreement with that reported by previous studies conducted by Jabbarvand et al., Alio et al., and Mahmood et al. who found flattening with values between 8 and 9.78 D, [5],[7],[8] while the results of flattening was slightly higher than other findings by Jabbarvand et al. who found flattening of 5.43 and 4.69 D in their study groups using different implantation depths of MyoRing. These marked changes in mean K readings of our subjects could be attributed to the fact that patients with advanced keratoconus (mean K > 52 D) were included, and the MyoRing have been reported to induce the greatest corneal changes on patients with advanced keratoconus. [11]

Results also showed significant improvement in SE of refraction post-MyoRing implantation. The mean changes in SE of refraction was found to be equal to 7.10 D that was slightly higher compared to that reported by Alio et al. who found mean changes of 4.62 and 4.47 D in spherical and cylindrical component of refraction, respectively. [5]

In term of visual outcomes, this study showed significant improvement in unaided postoperative visual acuity compared with preoperative unaided and spectacle visual acuity. The improvement was calculated to be around 9 lines from the unaided and 4 lines from spectacle preoperative visual acuity. The visual outcomes from the current study were similar to that reported by Alio et al., Daxer et al., and Mahmood et al. [5],[6],[7] The results were in concordance with the significant improvement of refractive outcomes and the central flattening changes of the anterior surface of the cornea.

In regards to CCT, the findings showed no significant changes in mean central corneal pachymetry (P = 0.72). This result was contradicted to that reported by Alio et al. who found significant thickening of central cornea 1-year post-MyoRing implantation in their sample. [5] The authors attributed the changes to the molding effect induces by the MyoRing, which induces a redistribution of stromal tissue. Their study reported the changes after 1 year of MyoRing insertion. However, this study evaluated only the changes after 3 months postoperation.


  Conclusion Top


Findings from this study showed that MyoRing implantation allows a significant reduction of myopic and astigmatic refractive errors because of the central corneal flattening induced, which significantly contributes to the improved visual outcomes of this type of operation.

There are two limitations in this study. First, the small size of the study sample, and second, the short duration of follow-up as the MyoRing implantation started recently in this country.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Zadnik K, Barr JT, Gordon MO, Edrington TB. Biomicroscopic signs and disease severity in keratoconus. Collaborative Longitudinal Evaluation of Keratoconus (CLEK) Study Group. Cornea 1996;15:139-46.  Back to cited text no. 1
    
2.
Rabinowitz YS. Keratoconus. Surv Ophthalmol 1998;42:297-319.  Back to cited text no. 2
    
3.
Chan CC, Sharma M, Wachler BS. Effect of inferior-segment intacs with and without C3-R on keratoconus. J Cataract Refract Surg 2007;33:75-80.  Back to cited text no. 3
    
4.
Zare MA, Hashemi H, Salari MR. Intracorneal ring segment implantation for the management of keratoconus: Safety and efficacy. J Cataract Refract Surg 2007;33:1886-91.  Back to cited text no. 4
    
5.
Alio JL, Piñero DP, Daxer A. Clinical outcomes after complete ring implantation in corneal ectasia using the femtosecond technology: A pilot study. Ophthalmology 2011;118:1282-90.  Back to cited text no. 5
    
6.
Daxer A, Mahmoud H, Venkateswaran RS. Intracorneal continuous ring implantation for keratoconus: One-year follow-up. J Cataract Refract Surg 2010;36:1296-302.  Back to cited text no. 6
    
7.
Mahmood H, Venkateswaran RS, Daxer A. Implantation of a complete corneal ring in an intrastromal pocket for keratoconus. J Refract Surg 2011;27:63-8.  Back to cited text no. 7
    
8.
Jabbarvand M, Salamatrad A, Hashemian H, Mazloumi M, Khodaparast M. Continuous intracorneal ring implantation for keratoconus using a femtosecond laser. J Cataract Refract Surg 2013;39:1081-7.  Back to cited text no. 8
    
9.
Binnawi KH, Abdu M. Visual and refractive outcome of the first intracorneal continuous ring implantation in Sudan. Sudanese J Ophthalmol 2015;7:16-8.  Back to cited text no. 9
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10.
Krumeich JH, Daniel J. Live epikeratophakia and deep lamellar keratoplasty for I-III stage-specific surgical treatment of keratoconus. Klin Monbl Augenheilkd 1997;211:94-100.  Back to cited text no. 10
    
11.
Jabbarvand M, Hashemi H, Mohammadpour M, Khojasteh H, Khodaparast M, Hashemian H. Implantation of a complete intrastromal corneal ring at 2 different stromal depths in keratoconus. Cornea 2014;33:141-4.  Back to cited text no. 11
    


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