CISIS/MyoRing long-term results

More than 95% of the eyes treated with MyoRing keratoplasty show permanent improvement of visual acuity.

Usually, CISIS (MyoRing keratoplasty) leads to sustainable long-term improvements of visual acuity. This means, that MyoRing keratoplasty can be used, on the one hand, for visual rehabilitation and, on the other hand, for stopping the progression of the disease. Long-term results covering a period of follow-up observations of up to 8 years even indicate, that besides stopping the progression of the disease, frequently, there is a measurable additional improvement in terms of antiprogression (Daxer A., Ettl A., Hörantner R. Long-term results of MyoRing treatment of keratoconus. Journal of Optometry 2017;10:123-129).

Thus, MyoRing keratoplasty can be considered as the only therapy with results resembling something like a "cure" of the disease.


Visual acuity

The two images depict the visual acuity of treated eyes approximately one year (postop 1, white dots) and five years after surgery (postop 2, black dots) in relation to the severity of the disease. The severity of the disease is shown on the horizontal axis in terms of visual acuity before treatment measured in logMAR. On the actual logMAR scale, 0 means full visual acuity of 20/20 (6/6), 1.0 in logMAR means low visual acuity of 20/200 and 2.0 represents a very low preoperative visual acuity of 20/2000, permitting as little as counting fingers. The abbreviation UDVA stands for uncorrected visual acuity (without optical aids) and CDVA refers to visual acuity with the best possible correction via glasses (b in the image below). The dotted line shows the theoretical result if - in every single case - full visual acuity had been restored. The interrupted line displays the results one year and the full line five years after surgery. The vertical scale demonstrates the achieved improvement of visual acuity.

It is rather obvious that there is an impressive improvement of visual acuity, which keeps improving year after year. This can be observed by looking at the improvement line, which, after a period of five years, has moved significantly closer to the theoretically maximally possible improvement of visual acuity as compared to one year after surgery. The reason for this result is the strengthening of the cornea as described above as well as the continuous "smoothing" of the central cornea mounted on the MyoRing by the intra-corneal pressure. One can therefore not only observe a stop of the progression of the disease, but even, in many cases, a slight continuous improvement of visual acuity over the years in terms of antiprogression or a "cure", accordingly.

Borderline cases

As a matter of fact, there are individual cases in which a satisfying correction cannot be performed. This especially applies if the cone is extremely steep and even by using the strongest MyoRing only insufficient corrections could be made. Even so, frequently, the cornea can be regularised to a degree which allows for a satisfying degree of visual acuity in combination with RGP lenses.

Complications and side effects

CISIS is an extremely safe therapy and complications are very rare. Possible complications are perforations, extrusions or infections. During the past 10 years where more than 1.500 MyoRing treatments have been performed in our centre, only 1 infection, 2 perforations and 7 extrusions have been observed. Each of these rare complications could be handled without any fatal results. Even so, there are two relevant side effects. First of all, in up to 15% of all cases there is over- or under correction. In these cases the initially used MyoRing has to be replaced after 3 months by a weaker or a stronger one. Usually, this exchange is completely harmless and takes only a minute. Second, at night, when the pupil enlarges, there can be disturbing light reflexes around light sources (halos) in up to 30% of all cases during the first couple of months after surgery. Halos hardly ever occur during day-time. Along the improvement of visual acuity within the first three months, these halos become weaker and occur less frequently. In some cases, they never completely disappear. However, after a period of 6 months, they are usually not as strong as to be perceived as disturbing anymore. By improving visual acuity during night-time by wearing glasses for example, this phenomenon can be further reduced or corrected if it should still be an issue 3-6 months after surgery. Only less than 5% of all treated patients perceive these halos as disturbing during night-time, given that they still occur, after a period of six months. In the long run, there are hardly any patients who perceive them as disturbing enough as to desire the removal of the MyoRing.


Long-term stability

In yet another illustration of the long-term results, which depicts individual improvements of visual acuity, one can recognize long-term stability even better. The image shows rather clearly, that there is a stop of the progression of the disease combined with an additional continuous improvement after surgery. This can be considered as "antiprogression" which allows for referring to this therapy as a "cure of the disease". The white dots show the improvement of visual acuity between the first and the fifth year after surgery. The improvement of uncorrected visual acuity is represented on the horizontal axis, while the vertical axis displays improvements of corrected visual acuity. Not a single eye shows a significant deterioration in this study and almost all of them display improvements of visual acuity within this period (Prangl-Grötzl A., Ettl A., Hörantner R., Daxer A. Individual Long-term stability after MyoRing Treatment of Keratoconus. International Journal of Keratoconus and Ectactic Corneal Diseases 2016; 5:53-56).


Three months after surgery, visual acuity can be considered as rather stable and, usually, as considerably improved (Daxer A., Mahmoud H., Venkateswaran SR. Intracorneal continuous ring implantation for keratoconus: One-year follow-up. J Cataract Refract Surg 2010; 36:1296-1302). As the MyoRing is a full ring with a high degree of stiffness, the intraocular pressure naturally and constantly pushes the cornea against this regular and closed circular structure which results in an additional evening out of the minor irregularities still remaining after surgery. Thus, continuous improvement while visual acuity is still high can be achieved. Open structures such as ring segments, on the other hand, do not work accordingly.

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