Impact of classifying keratoconus location based on keratometry or pachymetry on progression parameters

Abstract

Background This study sought to assess the impact of classifying keratoconus location based on thinnest pachymetry or maximum keratometry (Kmax) on progression parameters after corneal crosslinking (CXL). Methods In this observational study, patients were followed up at one, three, six and 12 months after CXL. All patients underwent visual acuity, Scheimpflug tomography and slitlamp assessment at all follow‐ups. Keratoconus was classified as central, paracentral and peripheral based on X and Y co‐ordinates of either thinnest pachymetry (Group 1) or Kmax (Group 2). Progression parameters Kmax, ABCD grading, anterior, posterior and total wavefront (WF) aberrations were compared between the groups. Results Fifty‐two eyes (43 patients) were classified into Groups 1 and 2: there were 82.8 per cent, 13.4 per cent, 3.8 per cent and 42.3 per cent, 38.4 per cent, 19.2 per cent central, paracentral and peripheral cones respectively. Central cones: Group 1: ‘C’ decreased after three months, Kmax, ‘A’, anterior and total WF decreased after six months. Group 2: Kmax, anterior and total WF decreased after three months, ‘A’ decreased at 12 months, whereas ‘C’ increased from three months. Paracentral cones: Group 1: no significant changes. Group 2: Kmax and ‘A’ decreased after six months, ‘C’ increased after three months. Peripheral cones: Group 1: no significant changes. Group 2: ‘C’ increased only at one month. Conclusion Thinnest pachymetry and Kmax should not be used interchangeably when categorising keratoconus. Although keratoconus may have thin cornea centrally, the Kmax may not be central. For the majority of parameters considered for monitoring progression, changes were noticed earlier when the keratoconus was classified based on Kmax.

Assessment of the postoperative effect of corneal cross-linking on keratoconus using the ABCD grading system

“…Sağlık et al . [ 21 ] showed significant regression in parameter A 1 year after CXL, which coincides with the results of Bardan,[ 16 ] but differs from the results of the current study. Bardan et al .…”

“…Bardan et al . [ 16 ] did not report any significant changes in parameter B over time. The results of our study differ since this variable showed a significant increase 1 year postoperatively.…”

“…Parameter A and ARC showed no change from the baseline over time. According to Bardan et al ,[ 16 ] parameter A showed a significant reduction over the first post-CXL year, while C and D significantly increased (parameter C was increased at all visits compared to the baseline, while parameter D showed an increase only a month post-CXL).…”

“…The flattening of Kmax, which was shown in many previous studies, was not noticed in ours, although it should be emphasized that the values of Kmax remained stable over time. [ 16 21 23 ]…”

Characteristics and clinical outcomes of patients diagnosed with keratocone

“…(2) Em relação à classificação dos pacientes quanto à gravidade da doença, o Consenso Global de Ceratocone e Doenças Ectásicas de 2015 (2) colocou esta questão em pauta e concluiu que não haveria um sistema de classificação clínica adequado para a doença e, de fato, a sua classificação sofre bastante variabilidade entre os estudos. (9,28,29) Este trabalho optou por acessar a gravidade dos casos estudados a partir do critério proposto pelo estudo CLEK, (10) que utilizou um dado ceratométrico, especificamente o Ks (ceratometria mais curva -steep keratometry), para classificar os casos em leves, moderados e graves. Os resultados mostraram uma tendência considerável em direção ao encontro de casos considerados graves, 157 (58,80%), propensão esta também encontrada e já esperada pelo estudo CLEK (10) ao se optar pelo Ks como parâmetro.…”