Repeatability of essential tomographic and aberrometric parameters of the Pentacam

Abstract

Purpose : To establish the degree of repeatability for numerous tomographic and aberrometric parameters for the Pentacam AXL and AXL Wave.

Methods : Retrospective study with three consecutive measurements per eye, all with good quality scores of the respective parameters. Tomography was measured by the Pentacam AXL and AXL Wave, aberrometry data originated exclusively from the AXL Wave (hence, was a subgroup of the entire measurements).
The following tomographic parameters were analysed: Chord µ, Chord α, HWTW, B/F Ratio; Pachymetry (apex, thinnest and their difference), anterior chamber depth (ext and int), corneal optical densitometry and pupil dia. (photopic).
The following aberrometric parameters (total eye) were analysed: RMS HOA, Spherical Aberration, Coma and pupil dia. (mesopic). Repeatability was assessed with the standard deviation and the coefficient of variation (CV [%])

Results : The study includes 97 patients (96 OD and 92 OS) with a mean age of 37 ±13,8 years (the subgroup comprises 59 OD and 56 OS). The examined eyes were all phakic and without any known ocular pathologies.
Tomographic parameters. Chord µ: mean=0,22µm, SD=0,02, CV=11,2; Chord α: mean=0,45µm, SD=0,04, CV=8,2; HWTW: mean=12,1mm, SD=0,05, CV=0,4; B/F Ratio: mean=82%, SD=0,31, CV=0,4; Pachy_apex: mean=540µm, SD=1,8, CV=0,3; Pachy_thinnest: mean=535µm, SD=2,1, CV=0,4; Pachy_Diff: mean=4,9µm, SD=1,2, CV=24,4; ACD_ext: mean=3,50mm, SD=0,02, CV=0,6; ACD_int: mean=2,97mm, SD=0,02, CV=0,7; COD: mean=13,2%, SD=0,65, CV=4,9; pupil dia_photopic: mean=2,7mm, SD=0,13, CV=4,9.
Aberrometric parameters. RMS HOA mean=0,126µm, SD=0,023, CV=18,3; spherical aberration: mean=0,046µm, SD=0,014, CV=30,1; coma: mean=0,066µm, SD=0,023, CV=34,2; pupil dia_mesopic: mean=5,1mm, SD=0,4, CV=7,0.

Conclusions : The analysis showed very good repeatability for all tomographic parameters. Standard deviations confirmed values clearly below clinical relevant deviations. CVs were excellent for six parameters and still good for further four. The standard deviations of the aberrometric parameters also revealed good repeatability. The slightly higher values for the coefficient of variations can be explained with the low mean value of the aberrations. The comparison of the repeatability for the mesopic and photopic pupil diameters showed a better repeatability under photopic conditions.

This is a 2021 ARVO Annual Meeting abstract.