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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, Egypt3Medical Research Institute, Alexandria University, Egypt

4General Surgery Dept., Mayo Clinic College of Medicine, Rochester, MN

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.

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KERATACx

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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

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.

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Femto tunnel creation Tunnel before ring application KERATACx before insertion

KERATACx after insertion

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).

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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).

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Results

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Summary of Visual, Refractive and Keratometric Outcomes

  Preoperative (n = 29)Postoperative (n =

29)Sig. p

UDVA 0.05 (0.005 - 0.170) 0.16 (0.05 - 0.63) Z = 4.707 0.000***

BDVA 0.17 (0.030 - 0.330) 0.5 (0.16 - 1) Z = 4.706 0.000***

Sphere (D) - 4 (-24 -1) - 0.5 (- 10 -3) Z = 4.720 0.000***

Cylinder (D) -4.41 ± 2.10 -2.5 ± 1.88 T = 5.041 0.000***

K-value (D) 51.71 ± 5.83 46.88 ± 5.35 T = 7.669 0.000***

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

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.

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