Reproducibility of the measurement of Optic Nerve Head Hemoglobin levels

Abstract

Purpose: To evaluate the intraobserver, interobserver, within and between-session reproducibility of the measurement of Optic Nerve Head (ONH) Hemoglobin levels using colour analysis by Laguna ONhE (Optic Nerve Hemoglobine) program.

Methods: Observational prospective study of 29 eyes (11 hypertensive and glaucomatous; 18 healthy eyes). Two investigators obtained two retinographies (Canon non-mydriatic retinal camera CD-DGi, Canon Inc.,Tokyo, Japan) in two testing sessions three weeks apart and analyzed the images using the Laguna ONhE (Optic Nerve Hemoglobine). The following parameters were quantified: ONH Hemoglobin concentration in its whole extent and in vertical disk diameter, disc-cup ratio and GDF (Glaucoma Discriminant Function). Agreement was illustrated using Bland-Altman plots and reproducibility was assessed comparing the intraclass correlation coefficients (ICC).

Results: In session 1, investigator 1 found mean levels of ONH Hemoglobin of 67.94 +/- 8.70% in healthy eyes and of 57.90+/-5.36% in hypertensive and glaucomatous eyes. Correspondent values for investigator 2 were 68.27 +/- 8.52% and 57.83 +/-4.88%, respectively. ONH Hemoglobin concentration measurements, in its whole as well as in the vertical diameter, showed the highest ICCs (All above 0.9). Variability was greater for GFD (ICC>0.8) and cup-disc ratio (ICC>0.71).

Conclusions: The measurement of ONH Hemoglobin concentration using the Laguna ONhE program shows high reproducibility both in glaucomatous and non-glaucomatous ONHs.

Keywords: 549 image processing • 610 nerve fiber layer • 628 optic flow