2. Nizar S Abdelfattah, M.D.1, Marina Israel2, Nermin Osman, M.D.3,
Visual and Topographic Outcomes of Intracorneal Rings After Primary Keratoconus and Post-LASIK Ectasia
Nizar S Abdelfattah, M.D.1, Marina Israel2, Nermin Osman, M.D.3,
Amira Zayed, M.D.4, Mohamed Yousif, M.D., F.R.C.S.2
1Doheny Eye Institute and the Department of Ophthalmology, David Geffen School of Medicine at UCLA 2Faculty of Medicine, Ain Shams University, Cairo, Egypt
3Medical Research Institute, Alexandria University, Egypt
4General Surgery Dept., Mayo Clinic College of Medicine, Rochester, MN

3. Purpose
To evaluate the optical value of implanting KERATACx intra-stromal corneal rings in patients with keratoconus and to quantify subsequent changes in corneal topography and asphericity.

4. KERATACx Differences from Intacs (FDA approved): KERATACx Intacs
Myopic Correction
-0.5: -7.0 Diopters
-0.5: -4.0 Diopters
Pupil Zone
4.8 mm
6.00 mm
Shape
Triangular
Flat
Edges
Rounded
Sharp
Arc
3200
3000

5. Patients & Methods
Twenty-nine eyes (24 patients; 16 male & 8 female), aging 30.1 ± 10.6 years diagnosed with primary and post-LASIK keratoconus non-contact lens wearers were included.
Surgeries were performed using intra-corneal rings (KERATACx) implanted using the femtosecond laser (Wavelight-FS 200) in 22 eyes, and the manual micro-keratome in 7 eyes.
All eyes had clear visual axis and corneal thickness > 450 µm at the proposed incision site.

6. Femto tunnel creation
Tunnel before ring application
KERATACx before insertion
KERATACx after insertion

7. Patients & Methods
Pre and post-operative Pentacam (Oculus Inc.) images were acquired at average 7 months follow-up were analyzed using matched pair t-test, Chi-square, Pearson, and Kolomogorov-Smirnov tests.
All statistical tests of significance were two tailed (SPSS-22).

8. Results
Regarding visual outcomes, there was a statistically significant improvement in uncorrected and best corrected visual acuity after rings implantation (z = 4.7, p < 0.001).
Median sphere also showed statistically significant reduction from -4 to -0.5 (p < 0.001), with median cylinder reduction from -4.4 to -2.5 (p < 0.001).
Topographically, we found a statistically significant reduction in all topographic parameters postoperatively including: K-max (49.4 vs. 45.1, p < 0.001), K-min (49.4 vs. 45.1, p < 0.001), mean keratometric value (51.4 vs. 48.4, p < 0.001), astigmatism (-2 vs. -0.5, p < 0.001), and asphericity (eccentricity of 0.49 vs. 0.23, p < 0.001).

9. Summary of Visual, Refractive and Keratometric Outcomes
Results
Summary of Visual, Refractive and Keratometric Outcomes
Preoperative (n = 29)
Postoperative (n = 29)
Sig. p
UDVA
0.05 ( )
0.16 ( )
Z = 4.707
0.000***
BDVA
0.17 ( )
0.5 ( )
Z = 4.706
Sphere (D)
- 4 (-24 -1)
- 0.5 ( )
Z = 4.720
Cylinder (D)
-4.41 ± 2.10
-2.5 ± 1.88
T = 5.041
K-value (D)
51.71 ± 5.83
46.88 ± 5.35
T = 7.669
UDVA: uncorrected distance visual acuity, BDVA: best corrected distance visual acuity, D: diapoters, K-value: Average keratometry value;
T: Paired t-test. Z: Z for Wilicoxon test ***: Statistically significant at p ≤ 0.001

10. Conclusions
Inserting intra-corneal rings (KERATACx) using the femtosecond or manual method showed topographic and visual efficacy in management of keratoconus.
The potential difference in outcome between the two surgical incisions and the effect of different ring sizes requires further investigations especially applied in longitudinal studies.