Usually, CISIS leads to sustainable long-term improvements of visual acuity. This means that CISIS 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 2016 (in print). Thus, CISIS can be considered the only therapy with results resembling a “cure” of the disease.
Visual acuity: The opposite 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 the CISIS therapy. On the actual logMAR scale 0 means full visual acuity of 1.0 on the adapted scale, 1.0 in logMAR means low visual acuity of 0 on the decimal scale and 2.0 represents a very low preoperative visual acuity, permitting as little as the counting of fingers before surgery. The abbreviation UDVA stands for uncorrected visual acuity (without visual aids, a in the illustration above) and CDVA refers to visual acuity with the best possible correction via glasses (b in the image below). The punctuated line shows the theoretical result that in every single case full visual acuity could be restored. The other two lines depict the linear regression of the results. The dotted line displays the results one year and the uninterrupted line five years after surgery. The vertical scale demonstrates the achieved improvement of visual acuity in lines.
It is rather straight forward that there is an impressive improvement of visual acuity which additionally keeps getting better year after year. This can be observed by looking at the line of regression 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. One cannot only observe a stop of the progression of the disease, but also, in many cases, a continuous improvement of visual acuity in terms of antiprogression or a cure, accordingly. One necessity for achieving these results is the strict fulfilment of the treatment scheme (J Optometry, 2016).
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 thickest MyoRing of them all, while the corneal thickness would suffice in theory, only insufficient corrections could be made; this is, if basically, the only available therapy was a cornea transplant. Even under these conditions the question arises if CISIS could at least be tried to avoid a cornea transplant. However, in cases as extreme as these only an unsatisfying improvement of visual acuity with or without glasses can be achieved in many cases. Even so, frequently, the cornea can be regularised to a degree which allows for a satisfying degree of visual acuity in combination with a hard contact lens. In contrast to the rather difficult keratoconus lens before surgery, hard contact lenses are tolerated once again. Occasionally, if the cornea of one such case is soft and can be shaped rather easily, it is even possible to reach a satisfying result with or even without glasses.
Complications and side effects: CISIS is a highly safe therapy and complications occur very infrequently. Possible complications, such as perforations, extrusions or infections are hardly ever observed. 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 only takes a few minutes. Second, there can be intruding light reflexes around light sources (halos) in up to 30% of all cases during the first couple of weeks after surgery during night-time, when the pupil widens. Halos hardly ever occur during day-time. Along the improvement of visual acuity within the first three months, these halos become clearer and occur less frequently. In individual cases they never completely disappear, however, after a period of 6 months they are not as strong as to be perceived as intruding anymore. By improving visual acuity during night-time, by wearing glasses, for example, this phenomenon can be further reduced or corrected should it still be an issue 3-6 months after surgery. Only 2% of all treated patients perceive these halos as intruding, given that they still occur, after a period of six months. In the long run there are hardly any patients who perceive them as intruding 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. One can see rather clearly in the opposite image that there is a stop of the progression of the disease combined with an additional continuous improvement year after year after surgery. This can be considered “antiprogression” which allows for referring to this therapy as “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 one single eye shows a significant deterioration and most of them display improvements of visual acuity within this period. Even one year after surgery there is a statistically significant improvement up to five years after treatment (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)
The explanation is as follows: Three months after surgery visual acuity can be considered rather stable and, usually, 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 implanted during CISIS is a full-ring with a high degree of stiffness, the intraocular pressure naturally and constantly pushes the cornea against this regular and closed structure which results in an additional evening out of the minor irregularities still remaining after surgery. Thus, a continuous improvement while visual acuity is still high can be achieved. Open structures, on the other hand, do not work accordingly (segments, incomplete rings) given their physical properties.