International Journal of Keratoconus and Ectatic Corneal Diseases

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VOLUME 2 , ISSUE 1 ( January-April, 2013 ) > List of Articles

RESEARCH ARTICLE

The Influence of Corneal Volume in Surgical Planning: Insights for a New Parameter for the Ferrara Ring Nomogram

Leonardo Torquetti, Wagner Gomes Dias

Citation Information : Torquetti L, Dias WG. The Influence of Corneal Volume in Surgical Planning: Insights for a New Parameter for the Ferrara Ring Nomogram. Int J Kerat Ect Cor Dis 2013; 2 (1):12-15.

DOI: 10.5005/jp-journals-10025-1041

Published Online: 01-04-2013

Copyright Statement:  Copyright © 2013; Jaypee Brothers Medical Publishers (P) Ltd.


Abstract

Purpose

To evaluate the corneal volume (CV) before and after Ferrara intrastromal corneal ring segments (ICRS) implantation and its influence in clinical outcomes in keratoconus patients.

Materials and methods

A total of 77 eyes of 42 keratoconus patients consecutively implanted with the Ferrara ICRS were evaluated with a Pentacam (Oculus Optikgerate GmbH). The following parameters were obtained: Anterior corneal asphericity (Q), CV and thinnest corneal thickness (TCT). The inter-relation between Q and CV was evaluated.

Results

In patients with CV inside two standard deviation (SD: 53.51-60.65) of the mean CV, the postoperative asphericity values roughly agreed with expected asphericity values. In patients with CV outside two SD intervals (<53.51 and >60.65) of the mean CV, the postoperative asphericity values did not agreed with expected asphericity values. Corneas with high volumes (>60.65) had less change of asphericity than corneas with low volumes.

Conclusion

The CV is a new parameter, to be better studied, as it seems to be important in ICRS selection. Corneas with high volumes may require more tissue to get flattened and properly reshaped.

How to cite this article

Torquetti L, Ferrara G, Dias WG, Ferrara P. The Influence of Corneal Volume in Surgical Planning: Insights for a New Parameter for the Ferrara Ring Nomogram. Int J Kerat Ect Cor Dis 2013;2(1):12-15.


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  1. System of ophthalmology. Diseases of the outer eye. London: Henry Kimpton 1965;964-76.
  2. Immunoglobulin patterns in keratoconus with particular reference to total and specific IgE levels. Br J Ophthalmol 1982;66(11):717-20.
  3. Aetiology of keratoconus. Br J Ophthalmol 1976;60(7):522-25.
  4. Changes in anterior and posterior corneal curvatures in keratoconus. Ophthalmology 2000;107(7):1328-32.
  5. Changes in corneal asphericity after laser in situ keratomileusis. J Cataract Refract Surg 2003;29:762-68.
  6. Corneal asphericity after refractive surgery when the Munnerlyn formula is applied. J Opt Soc Am A Opt Image Sci Vis 2004;21:98-103.
  7. Equation for corneal asphericity after corneal refractive surgery. J Refract Surg 2003;19:65-69.
  8. Impact of interocular differences in corneal asphericity on binocular summation. Am J Ophthalmol 2003;135:279-84.
  9. The new Ferrara ring nomogram: The importance of corneal asphericity in ring selection. Vision Panamerica, September 2010. Available from: http://www.paao.org/pdf/vpa/9.3_vpa.pdf.
  10. Corneal asphericity changes after implantation of intrastromal corneal ring segments in keratoconus. J Emmetropia 2010;1:178-81.
  11. Asfericidad corneal en una poblácion de adultos jóvenes. Implicaciones clínicas. Arch Soc Esp Oftalmol 2004;79:385-92.
  12. Corneal- thickness spatial profile and corneal-volume distribution: tomographic indices to detect keratoconus. J Cataract Refract Surg 2006;32:1851-59.
  13. Corneal volume, pachymetry, and correlation of anterior and posterior corneal shape in subclinical and different stages of clinical keratoconus. J Cataract Refract Surg 2010;36:814-25.
  14. Evaluation of anterior segment parameters in keratoconic eyes measured with Pentacam system. J Cataract Refract Surg 2007;33:1708-12.
  15. The measurement principle. Available from: http://www.pentacam.com/sites/messprinzip.php. Assessed: 2-Jan 2013.
  16. Determination of corneal volume from anterior topography and topographic pachymetry: application to healthy and keratoconic eyes. Ophthalmic Physiol Opt 2009;29(6):652-60.
  17. Correlation of anterior segment parameters in keratoconus. Int J Kerat Ect Cor Dis. 2012;1(2)87- 91.
  18. Reduction in corneal volume with severity of keratoconus. Curr Eye Res 2011;36(6):522-27.
  19. Quantification of the surgically induced refractive effect of intrastromal corneal ring segments in keratoconus with standardized incision site and segment size. J Cataract Refract Surg 2011 Oct;37(10):1865-70.
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