ESCRS - FPS02.08 - Best Fit Sphere Back And Adjusted Maximum Elevation Of Corneal Back Surface As Novel Predictors Of Keratoconus Progression

Best Fit Sphere Back And Adjusted Maximum Elevation Of Corneal Back Surface As Novel Predictors Of Keratoconus Progression

Published 2022 - 40th Congress of the ESCRS

Reference: FPS02.08 | Type: Free paper | DOI: 10.82333/fx2c-9k13

Authors: Margarida Ribeiro* 1 , Cláudia Barbosa 2 , Luís Torrão 3 , Pedro Neves Cardoso 3 , Raúl Moreira 3 , Fernando Falcão-Reis 1 , João Pinheiro-Costa 1

1Ophthalmology,Centro Hospitalar Universitário de São João,Porto,Portugal;Faculty of Medicine of Porto University,Porto,Portugal, 2Faculty of Medicine of Porto University,Porto,Portugal, 3Ophthalmology,Centro Hospitalar Universitário de São João,Porto,Portugal

Purpose

The current management of Keratoconus (KTC) aims two goals: to improve visual function and to stop ectatic progression. Efforts should be endorsed to detect subclinical progression and to avoid unnecessary treatments. Several studies aimed at defining and detecting progression, but there is still no standardized method for it. The main purpose of this study was to evaluate the Maximum Elevation of Corneal Back Surface adjusted to the same Best Fit Sphere Back between timeline measurements (AdjEleBmax) and the Best Fit Sphere Back (BFSB) radius itself as new tomographic parameters for documentation of ectasia progression and to compare them with the most recent and reliable parameters used on keratoconus progression. 

Setting

Retrospective cohort study that took place in the Department of Ophthalmology of Centro Hospitalar Universitário de São João, a tertiary and universitary centre.

Methods

113 eyes of 76 consecutive patients aged 14 to 30 years old with keratoconus were examined in our Department between October and December 2018 and included in this retrospective cohort study. For progression detection, at least two tomographic measurements were performed per eye, separated by 12±3 months. We collected several tomographic variables already commonly accepted as progression markers with described cut-offs in the literature (although not validated). This study added two new variables: best fit sphere back (BFSB) radius (cut-off value of -0.05 mm); and adjusted EleBmax (AdjEleBmax) (cut-off of 6.5μm). AdjEleBmax was obtained after adjusting EleBmax of the first measurement to the BSFB of the second measurement in the same eye

Results

We evaluated the performance of Kmax, D-index, EleBmax, BFSB and AdjEleBmax as isolated parameters to document keratoconus progression (defined as a significant change in two or more variables), we found a sensitivity of 49%, 82%, 51%, 65% and 63%, and a specificity of 100%, 98%, 73%, 80% and 84% to detect keratoconus progression (p < 0.001 for all). The area under the curve (AUC) for each variable was 0.82, 0.93, 0.69, 0.69, 0.75, respectively.

Conclusions

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, these back surface parameters still presented a good performance with a reasonable AUC. Considering the current knowledge that the posterior corneal surface may be the first interface to suffer changes in KTC, we suggest the inclusion of these two parameters in the evaluation of keratoconus progression in conjunction with other variables to increase the reliability of our clinical evaluation and early detection of progression.