Relationship Between Optic Nerve Head Hemoglobin Levelsand Structural-Functional Damage In Glaucoma: A Cross-Sectional Observational Study

Abstract

Purpose : It has been previously shown that patients with established glaucoma have lower levels of optic nerve head hemoglobin (ONH Hb). We sought to investigate structural and functional correlations in glaucoma patients using ONH Hb measurement-derived parameters as assessed by non-invasive automated colorimetric analysis (RetinaLyze^®; RetinaLyze System A/S).

Methods : A prospective, observational, cross-sectional study was carried-out, in which glaucomatous patients (defined as glaucomatous optic neuropathy and reproducible visual field defects) were consecutively enrolled. After inclusion, non mydriatic color fundus photographs and peripapillary retinal nerve fiber layer (pRNFL) thickness measurements (through spectral-domain optical coherence tomography [OCT]) were obtained from all participants. The software initially delineated the ONH border and identified the central retinal vessels. On the basis of colorimetric analysis, ONH Hb levels and the glaucoma discriminant function (GDF) index were determined. Scatter plots were constructed to investigate the correlation between GDF values and structural-functional parameters.

Results : A total of 30 eyes were included. Mean age of study patients was 57.3 ±11.3 years. Median values for visual field mean deviation index (VFMD), retinal nerve fiber layer thickness and GDF index were -3.2dB, 95.8 ± 14.1µm and -33.7, respectively. There was a significant non-linear correlation between GDF and VFMD values (R²=0.462; p=0.007). This correlation was similar to that found between OCTs RNFL thickness and VFMD (R²=0.538; p=0.006). Finally, a strong linear correlation was found between GDF and OCTs RNFL thickness values (R²=0.616; p〈0.001).

Conclusions : Our results showed significant associations between ONH Hb values and both structural and functional damage in glaucoma. The non-linear correlation we found between GDF values and visual field loss (which is similar to what is usually reported for RNFL thickness measurements) suggest that ONH Hb levels reduction precedes visual function changes in glaucoma. Further analyses are warranted in order to confirm our initial findings and to investigate its applicability in a clinical setting.

This is a 2020 ARVO Annual Meeting abstract.