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Intrastromal ring segment implantation in keratoconic eyes with non-coincident topographical and coma axes

Poster Details

First Author: C.Lisa SPAIN

Co Author(s):    L. Fernandez-Vega Cueto   J. Merallo-Lloves   J. Alfonso        

Abstract Details


To evaluate the feasibility and visual outcome of Ferrara-type intrastromal ring segments (ICRS) implantation in keratoconic eyes with non-coincident topographic and comatic axes.


Instituto Oftalmológico Fernández-Vega, Oviedo, Spain.


Retrospective case-series review. 41 eyes with paracentral keratoconus and flattest topographic and coma axes separated 30-70ẃ (“duck” pattern) were implanted with a single inferior 150ẃ ICRS. Snellen uncorrected distance visual acuity (UDVA), corrected distance visual acuity and (CDVA), coma-like Root Mean Square (RMS), and refractive errors, analyzed using vector analysis, were recorded before and 6 months after surgery.


Mean UDVA was 0.25 ±0.22 before and 0.45 ±0.33 after surgery (P< 0.001). CDVA changed from 0.78 ±0.22 before to 0.87 ±0.17 after surgery (P < 0.0001). 2 eyes lost ? 2 lines of CDVA, 3 eyes lost 1 line of CDVA, 16 eyes had their CDVA unchanged, 9 eyes gained 1 line and 11 eyes gained ? 2 lines of CDVA. Safety index was 1.11. Spherical equivalent and astigmatism components were highly reduced after ICRS implantation (P< 0.01). Coma-like RMS changed from 0.80?m before surgery to 0.64?m after surgery (P= 0.03) for 5mm of pupil size.


Ferrara-type ICRS implantation improves corneal topography in “duck” pattern keratoconus by compensating astigmatism and partially reducing coma, thereby improving both uncorrected and corrected visual acuity.

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