Aylin Kilic Ertan explores which keratoconus patients are most suitable for treatment with Intacs intracorneal rings.
Options for early KC treatment
Another option for early treatment is penetrating keratoplasty, which has been associated with only limited success in younger patients. This limited success can be attributed principally to pre-, intra- and postoperative problems, because low scleral rigidity, increased intraoperative fibrin formation, and positive vitreous pressure complicate the surgical procedure.
Although some studies report Intacs improves visual acuity as well as refractive and topographical findings in keratoconic patients, the effectiveness and safety of the implant in different age groups remain unknown. To investigate further, I conducted a study comparing the response to Intacs treatment in KC patients of different ages, assessing whether an age-related increase in corneal "stiffness" could impact the outcome of Intacs treatment. At the one year follow-up point, the study did not find any statistically significant differences between young, middle and older age groups in visual acuity, manifest sphere, cylinder, mean refractive spherical equivalent (MRSE) or mean-K readings (Figure 2, Tables 1 and 2) (ANOVA, p > 0.05).5 We therefore concluded that Intacs is as safe and effective in adolescent KC patients as in other age groups.
Intacs outcomes in severe keratoconus
Postoperatively, the stage IV group demonstrated less change in uncorrected visual acuity and more improvement in mean K values (p < 0.05, ANOVA). Six months after implantation, segment extrusions occurred in three eyes in the stage IV group: the patients were 18, 20 and 23 years old.
Improvements in visual acuity and astigmatism after implantation, in corneas with and without scarring due to keratoconic hydrops, have previously been reported.7 In that study, the BCVA improved to a greater degree in the scarring group than in the no-scarring group, and at the final follow-up visit (12 months postoperatively) Intacs had prevented the need for corneal transplantation. To our knowledge, this is the only study that suggests that patients with paracentral scarring or with corneas steeper than 57.0 D would benefit from Intacs. As our study found that Intacs implantation was effective in eyes with severe KC, however, our results support these earlier findings.
The first clinical results of the use of the femtosecond laser (which has demonstrated potential for high-precision micro machining and other applications) in Intacs treatment were reported in 2003.8 There were no intraoperative complications with the femtosecond laser in our study, and although segment extrusions occurred in three eyes during follow-up, this is less than the complication rate reported by Kanellopoulos,9 which was as high as 35%. Complications in that study included segment movement, exposure and corneal melting with mechanical tunnel dissection. The difference in complication rates may be attributed to use of the femtosecond laser method for channel creation and wide channel parameters.
Intacs recommended in all ages and stages
In both studies I conducted, in early and severe KC eyes, Intacs was a safe and effective treatment option. The efficacy of the implant was not compromised by implantation in young eyes, and although segment extrusions occurred in three stage IV eyes, the rate of complications remained low. Overall, I would recommend Intacs as a treatment whatever the age of the patient and whatever the stage of the disease. Although early treatment is recommended, Intacs implants remain effective even in eyes with severe KC.
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3. A. Ertan & O. Muftuoglu. Cornea 2008:27(10):1109–1113.
4. C.A. McCarty. Clin. Exp. Optom. 2002;85:91–96.
5. A. Ertan & E. Ozkilic. J. Refract. Surg. 2008;24:690–695.
6. A. Ertan & G. Kamburoglu. J. Cataract Refract. Surg. 2008;34:1521–1526.
7. T. Hellstedt, et al. J. Refract. Surg. 2005;21:236–246.
8. A. Ertan, et al. J. Cataract Refract. Surg. 2007;33:648–653.
9. K.G. Carrasquillo, et al. Cornea 2007;26(8):956–962.