Intracorneal Ring Segments in Refractive Treatment of Keratoconus: Nomogram-Based on Phenotypic Pattern of Ectasia
Narrative Responses:
Purpose
To evaluate the safety and efficacy of implanattion of intracornea ring segments (ICRS) based on a nomogram adapted for the phenotypic pattern of the ectasia. The ectasia pattern was classified based on the corneal thinnest point location and the relation between the topographic flat axis and the coma (Z31 and Z3-1) axis: bow-tie, nipple, croissant, duck and snowman.
Methods
Prospective, non-randomized study including 30 consecutive eyes submitted to intracorneal ring segments (ICRS) for the treatment of keratoconus, with a minimum follow-up of 6 months. Inclusion criteria: patients with keratoconus, contact lens intolerant, maximum keratometrix reading < 58,00 D and corneal pachymetry thinnest point > 400 µm. Evaluated parameters: UCVA and BCVA pre and postoperative, refractive sphere and cylinder, topography values (K1, K2 and Kmax) and 3rd order aberrometry values of Z31 and Z3-1 (Coma) for a 6,00 mm diameter pupil.
Results
All surgeries performed by the same surgeon under topical/peribulbar anesthesia with manual technique. At 6 months, we observed a statistically significant improvement in UCVA (snellen decimal scale) from 0.11 preop to 0.48 post (p<0.05) and in BCVA from 0.39 preop to 0.57 postoperative (p<0.05). 2 eyes (6.25%) lost up to 2 lines of BCVA, 59% gained 2 or more lines of vision, 15.6% gained 4 or more lines of vision. All topographic and aberrometric parameters improved after surgery, with statistically significance (p< 0.05).
Conclusion
Implantation of ICRS based on a nomogram adapted for the phonotipic pattern of the ectasia permits a significant gain in UCVA and BCVA. Therational for treatment of keratoconus with ICRS is changing from an orthopedic aproach to a personalized refractive procedure.