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Ferrara Ring: Nomogram

The Ferrara Ring nomogram is based on corneal asphericity. In this presentation we discuss how it works and how to choose the best segment for each case.
by

Paulo Ferrara

on 27 November 2012

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Transcript of Ferrara Ring: Nomogram

photo credit Nasa / Goddard Space Flight Center / Reto Stöckli NOMOGRAM Ferrara Ring Paulo Ferrara, MD, PhD Postop C-Quant: yellow ring 1 2 3 Jose Alfonso, MD Oviedo, Espana OD THANK YOU! pferrara@ferrararing.com.br Q (asphericity) and K (keratometry)
variation according to ring thickness

Asphericity


Addition in the cornea periphery = asphericity change – frequently without
concomitant significant corneal flattening;

Ring diameter = how much the cornea will be flattened, the astigmatism and
asphericity will be changed

Ring arc length = how much the asphericity, keratometry and astigmatism will be
changed. The shorter the segment, the greater the astigmatic correction, the lesser the
asphericity change. HOW THE FERRARA RING WORKS AVOID POSTOPERATIVE OBLATE CORNEAS !
Q (asphericity) = Quality of vision Segment thickness (160 – arc) Q Q (asphericity) variation according to ring thickness
ASPHERICITY (Q) Keratometry: 52.00 x 57.00 D NO !
same topographic astigmatism - different changes after ring implantation Are these the same ? Keratometry: 42.00 x 47.00 D Eye 2 Eye 1 Third generation (2006 - 2009): topographic astigmatism FERRARA RING NOMOGRAM 160 arc = 90% of keratoconus (“standard” ring)
- Q negative (prolate to hyperprolate cornea)
- Average to high K values
- Average to high astigmatism 210 arc = Nipple
- Q negative (hyperprolate cornea)
- High K values
- Low astigmatism 140 arc = PMD
- Q 0 or positive
- Low K values
- High astigmatism -0,23 0,5 -2 -1 0 Prolate Hyperprolate Oblate CORNEAL ASPHERICITY NO !
Cornea overcorrection in axial myopia Are these the same? Refraction: -10.00 D Eye 2 Second generation (2002 - 2006): spherical equivalent FERRARA RING NOMOGRAM The evolution of the nomogram ASPHERICITY 2002 2006 2009 1997 General Guidelines General Guidelines
Nomogram IMPORTANT Nipple Oval cones PMD Pachymetry IMPORTANT SUMMARY
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