The effect of thickness, degree and types of segmental Intrastromal corneal rings on visual and refractive outcomes in keratoconus patients.
Hesam Hashemian1 , Mehdi Khodaparast1 , Shiva Sabour1 , Fatemeh Alipour1 , Kianoush Shahraki1 , Sogol Olamazadeh1 , Zahra Moravej1 *
- Farabi Eye Hospital, Tehran University of Medical Sciences
Abstract: Keratoconus (KCN) is a non-inflammatory, bilateral, but asymmetric corneal ectatic disease that clinically manifests as corneal thinning and protrusion. KCN typically is accompanied by progressive myopic and irregular astigmatism as well as higher-order aberrations. Intracorneal rings are one of the main treatment modalities of keratoconus. Different types of rings are available, but differences between them and their results are inadequately studied.
Methods: This prospective cohort study was performed on 68 eyes of 68 patients with KeraRing (Mediphacos, Belo Horizonte, Brazil) implantation in Farabi Eye Hospital. Keraring is a ring segment with different arc lengths and thickness ranging from 150 to 350 μm. The inner and outer KeraRing diameters are 5 and 5.8-6.0 mm, respectively. All patients underwent comprehensive ophthalmic evaluation including dry manifest refraction, UDVA and CDVA, slit-lamp examination, preop and 3 months postop. The eyes were divided into three groups based on ICR thickness: 200 μm (20 patients), 250 μm (18 patients), and 300 μm (30 patients) and then different parameters visual and refractive parameters were assessed. The patients were also divided based on Ring arc degree: 160° (52 patients) and 210° (14 patients)
Results: Visual acuity and refraction improved in all cases 3 months postop. In 160-degree group UDVA and CDVA improved from 0.81 ± 0.41 and 0.35 ± 0.14 to 0.70 ± 0.39 and 0.28 ± 0.17 respectively. Similar results were seen in 210-degree group, and 200, 250 and 300 μm groups. Results of different ring thicknesses and arc lengths were compared, and no statistical significance was observed. The amount of correction of UDVA (UDVApre – UDVApost) was significantly better in 250 μm group. But this result was not correlated to better vision in this group of patients.
Conclusion: Despite progress in corneal ring treatments for keratoconus and different designs available, it is not clear what rings arc lengths and thicknesses are the better choice for keratoconus patients and more investigation is warranted to elucidate the optimum design of corneal rings for keratoconus patients.
