Clinical Ophthalmology (Dec 2022)

Best Fit Sphere Back and Adjusted Maximum Elevation of Corneal Back Surface as Novel Predictors of Keratoconus Progression

  • Ribeiro M,
  • Barbosa C,
  • Correia P,
  • Torrão L,
  • Neves Cardoso P,
  • Moreira R,
  • Falcão-Reis F,
  • Falcão M,
  • Pinheiro-Costa J

Journal volume & issue
Vol. Volume 16
pp. 4239 – 4248

Abstract

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Margarida Ribeiro,1,2,* Cláudia Barbosa,3,* Paulo Correia,3 Luís Torrão,1 Pedro Neves Cardoso,1 Raúl Moreira,1 Fernando Falcão-Reis,1,4 Manuel Falcão,1,4 João Pinheiro-Costa1,2 1Department of Ophthalmology, Centro Hospitalar e Universitário São João, Porto, Portugal; 2Department of Biomedicine – Faculty of Medicine of Porto University, Porto, Portugal; 3Faculty of Medicine of Porto University, Porto, Portugal; 4Department of Surgery and Physiology, Faculty of Medicine of Porto University, Porto, Portugal*These authors contributed equally to this workCorrespondence: Margarida Ribeiro, Department of Ophthalmology, Centro Hospitalar e Universitário São João, Alameda Prof. Hernâni Monteiro Porto, 4200-319, Portugal, Email [email protected]: We evaluated the Maximum Elevation of Corneal Back Surface adjusted to the same Best Fit Sphere Back (BFSB) between timeline measurements (AdjEleBmax) and the BFSB radius (BFSBR) itself as new tomographic parameters for documentation of ectasia progression and compare them with the most recent and reliable parameters used on keratoconus (KC) progression.Results: We evaluated the performance and the ideal cutoff point of Kmax, D-index, posterior radius of curvature from the 3.0 mm centered on the thinnest point (PRC), EleBmax, BFSBR, and AdjEleBmax as isolated parameters to document KC progression (defined as a significant change in two or more variables), we found a sensitivity of 70%, 82%, 79%, 65%, 51%, and 63% and a specificity of 91%, 98%, 80%, 73%, 80%, and 84% to detect KC progression. The area under the curve (AUC) for each variable was 0.822, 0.927, 0.844, 0.690, 0.695, 0.754, respectively.Conclusion: AdjEleBmax presented a greater specificity, larger AUC, and better performance compared to EleBmax without any adjustment, with similar sensitivity. Although AdjEleBmax and BFSB demonstrated smaller AUC and specificities comparing with Kmax and D-Index, AdjEleBmax still presented a good performance with a reasonable AUC. Since the shape of the posterior surface, more aspheric and curved than the anterior, may facilitate detection of change, we suggest the inclusion of AdjEleBmax in the evaluation of KC progression in conjunction with other variables to increase the reliability of our clinical evaluation and early detection of progression.Keywords: keratoconus, cornea, progression, best fit sphere back, maximum elevation of corneal back surface

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