Changes in Corneal Asphericity after MyoRing Implantation in Moderate and Severe Keratoconus


Purpose: To evaluate the effect of MyoRing implantation on corneal asphericity in moderate and severe keratoconus (KCN).

Methods: This cross-sectional observational study comprised 32 eyes of 28 patients with KCN, who had femtosecond-assisted MyoRing corneal implantation. The primary outcome measures were preoperative and six-month postoperative corneal asphericity in 6-, 7-, 8-, 9-, and 10-mm optical zones in the superior, inferior, nasal, temporal, and central areas. The secondary outcome measures included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction, thinnest location value, and keratometry readings.

Results: A significant improvement in the UDVA and CDVA was observed six months after the surgery (P < 0.001) with a significant reduction in the spherical (4.67 diopters (D)) and cylindrical (2.19 D) refractive errors. A significant reduction in the corneal asphericity in all the optical zones and in the superior, inferior, nasal, temporal, and central areas was noted (P < 0.001). The mean thickness at the thinnest location of the cornea decreased from 437.15 ± 30.69 to 422.81 ± 36.91 μm. A significant corneal flattening was seen. The K1, K2, and Km changes were 5.32 D, 7 D, and 6.17 D, respectively (P < 0.001).

Conclusion: MyoRing implantation is effective for improving corneal asphericity in patients with KCN. It allows successful corneal remodeling and provides a significant improvement in UDVA, CDVA, and refractive errors.


Cornea, Corneal Topography, Keratoconus

1. Sugar J, Macsai MS. What causes keratoconus? Cornea 2012;31:716–719.

2. Auffarth GU, Wang L, Völcker HE. Keratoconus evaluation using the Orbscan topography system. J Cataract Refr Surg 2000;26:222–228.

3. Prisant O, Legeais J-M, Renard G. Superior keratoconus. Cornea 1997;16:693–694.

4. Weed K, McGhee C, MacEwen C. Atypical unilateral superior keratoconus in young males. Contact Lens Anterio 2005;28:177–179.

5. Wheeler J, Hauser MA, Afshari NA, Allingham RR, Liu Y. The genetics of keratoconus: a review. Microscopy 2012;6;(Suppl 6). pii: 001.

6. Piñero DP, Alió JL, Alesón A, Vergara ME, Miranda M. Corneal volume, pachymetry, and correlation of anterior and posterior corneal shape in subclinical and different stages of clinical keratoconus. J Cataract Refr Surg 2010;36:814–825.

7. Alió JL, Piñero DP, Alesón A, Teus MA, Barraquer RI, Murta J, et al. Keratoconus-integrated characterization considering anterior corneal aberrations, internal astigmatism, and corneal biomechanics. J Cataract Refr Surg 2011;37:552– 568.

8. Miháltz K, Kovács I, Takács Á, Nagy ZZ. Evaluation of keratometric, pachymetric, and elevation parameters of keratoconic corneas with pentacam. Cornea 2009;28:976– 980.

9. Aslani F, Khorrami-Nejad M, Amiri MA, Hashemian H, Askarizadeh F, Khosravi B. Characteristics of posterior corneal astigmatism in different stages of keratoconus. J Ophthalmic Vision Res 2018;13:3.

10. Savini G, Barboni P, Carbonelli M, Hoffer KJ. Repeatability of automatic measurements by a new Scheimpflug camera combined with Placido topography. J Cataract Refr Surg 2011;37:1809–1816.

11. Khosravi B, Khorrrami-Nejad M, Rajabi S, Amiri M, Hashemian H, Khodaparast M. Characteristics of astigmatism after myoring implantation. Med Hypothesis Dis Innov Ophthalmol J 2017;6:130-135.

12. Swartz T, Marten L, Wang M. Measuring the cornea: the latest developments in corneal topography. Curr Opin Ophthalmol 2007;18:325–333.

13. Auffarth GU, Borkensein AFM, Ehmer A, Mannsfeld A, Rabsilber TM, Holzer MP. Scheimpflug and topography systems in ophthalmologic diagnostics. Der Ophthalmologe 2008;105:810–817.

14. Mathur A, Atchison DA. Effect of orthokeratology on peripheral aberrations of the eye. Optometry Vision Sci 2009;86:E476–E484.

15. Calossi A. Corneal asphericity and spherical aberration. J Refract Surg 2007;23:505.

16. Torquetti L, Ferrara P. Corneal asphericity changes after implantation of intrastromal corneal ring segments in keratoconus. J Emmetropia 2010;1:178–181.

17. Daxer A, Ettl A, Hörantner R. Long-term results of MyoRing treatment of keratoconus. J Optometry 2017;10:123–129.

18. Daxer A. MyoRing treatment of myopia. J Optometry 2017;10:194–198.

19. Alio JL, Piñero DP, Daxer A. Clinical outcomes after complete ring implantation in corneal ectasia using the femtosecond technology: a pilot study. Ophthalmology 2011;118:1282–1290.

20. 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;39:1081–1087.

21. Weed K, MacEwen C, Cox A, McGhee C. Quantitative analysis of corneal microstructure in keratoconus utilising in vivo confocal microscopy. Eye 2007;21:614–623.

22. Daxer A, Mahmoud H, Venkateswaran RS. Intracorneal continuous ring implantation for keratoconus: one-year follow-up. J Cataract Refract Surg 2010;36:1296–1302.

23. Jabbarvand M, SalamatRad A, Hashemian H, Khodaparast M. Continuous corneal intrastromal ring implantation for treatment of keratoconus in an Iranian population. Am J Ophthalmol 2013;155:837–842.e2.

24. Shabayek MH, Alió JL. Intrastromal corneal ring segment implantation by femtosecond laser for keratoconus correction. Ophthalmology 2007;114:1643–1652.

25. Piñero DP, Alio JL, Kady BE, Coskunseven E, Morbelli H, Uceda-Montanes A, et al. Refractive and aberrometric outcomes of intracorneal ring segments for keratoconus: mechanical versus femtosecond-assisted procedures. Ophthalmology 2009;116:1675–1687.

26. Mahmood H, Venkateswaran R, Daxer A. Implantation of a complete corneal ring in an intrastromal pocket for keratoconus. J Refract Surg 2011;27:63–68.

27. Saeed A. Corneal intrastromal MyoRing implantation in keratoconus treatment. J Egypt Ophthalmol Soc 2014;107:106.

28. Lackner B, Schmidinger G, Pieh S, Funovics MA, Skorpik C. Repeatability and reproducibility of central corneal thickness measurement with Pentacam, Orbscan, and ultrasound. Optometry Vision Sci 2005;82:892–899.

29. Hosny M, El–Mayah E, Sidky MK, Anis M. Femtosecond laser-assisted implantation of complete versus incomplete rings for keratoconus treatment. Clin Ophthalmol 2015;9:121.