Abstract
Purpose To investigate structural and functional correlations in glaucoma patients using optic nerve head hemoglobin (ONH Hb) measurements as determined by automated colorimetric analysis of conventional retinography. Methods We prospectively enrolled healthy participants and glaucomatous patients with a wide range of disease stages. All participants underwent visual field (VF) testing (standard automated perimetry, SAP), color fundus imaging (mydriatic retinography), and peripapillary retinal nerve fiber layer (pRNFL) assessment through spectral-domain optical coherence tomography (SD-OCT). Software Laguna ONhE was used to estimate the amount of ONH Hb and to determine the glaucoma discriminant function (GDF) index. Scatter plots were constructed, and regression analysis was used to investigate the correlations between GDF, average pRNFL thickness, and VF mean deviation (VFMD) index values. A secondary analysis was performed to compare each parameter between three different glaucoma groups divided according to VFMD values (mild, >−6 dB; moderate, −6 to −12 dB; and advanced, <−12 dB). Results One hundred ninety-six eyes from 123 participants (69 with glaucoma and 54 controls) were enrolled. Overall, all parameters evaluated differed significantly between glaucomatous and control eyes (p ≤ 0.001). The comparison of each parameter according to groups of disease stages revealed significant differences between controls and each of the glaucomatous groups (p < 0.001). More pronounced changes in GDF values were observed in early disease stages. We found significant nonlinear correlations between GDF and VFMD values (R2 = 0.295, p < 0.001) and between pRNFL thickness and VFMD (R2 = 0.598, p < 0.001). A linear correlation was found between GDF and pRNFL thickness values (R2 = 0.195, p < 0.001). Conclusion Our results showed significant associations between ONH Hb values and both structural and functional damage in glaucoma obtained by SD-OCT and SAP, respectively. The nonlinear correlation we found and the GDF behavior along different disease stages suggest that ONH Hb levels' reduction may precede visual function changes in early glaucoma stages.
Highlights
Glaucoma consists in the main cause of irreversible blindness worldwide [1]. e disease is considered as a progressive and chronic optic neuropathy, characterized by specific changes on the optic nerve head (ONH), peripapillary retinal nerve fiber layer, and visual field (VF) [2, 3]
Complete ophthalmological examination was performed in all participants. is evaluation included clinical history, best-corrected visual acuity, slit-lamp biomicroscopy, intraocular pressure (IOP) measurement with Goldmann applanation tonometry, gonioscopy, ultrasound pachymetry, dilated fundus examination, VF testing (Humphrey SITA—Standard 24-2, Carl Zeiss Meditec, Dublin, CA), color fundus imaging, and peripapillary retinal nerve fiber layer (pRNFL) and topographic ONH measurements based on spectral-domain optical coherence tomography (SD-optical coherence tomography (OCT)) (RTVue100 OCT; Optovue Inc., Fremont, CA)
Regarding the structure-function correlations we investigated in the glaucoma group, we found significant nonlinear correlations between glaucoma discriminant function (GDF) and VF mean deviation (VFMD) values (R2 0.295, p < 0.001; Figure 2) and between OCT’s pRNFL thickness and VFMD values (R2 0.598, p < 0.001; Figure 3)
Summary
Glaucoma consists in the main cause of irreversible blindness worldwide [1]. e disease is considered as a progressive and chronic optic neuropathy, characterized by specific changes on the optic nerve head (ONH), peripapillary retinal nerve fiber layer (pRNFL), and visual field (VF) [2, 3]. Glaucoma consists in the main cause of irreversible blindness worldwide [1]. E disease is considered as a progressive and chronic optic neuropathy, characterized by specific changes on the optic nerve head (ONH), peripapillary retinal nerve fiber layer (pRNFL), and visual field (VF) [2, 3]. Disease control and blindness prevention are strictly related to early diagnosis [2, 3]. The diagnosis of glaucoma can be challenging in the early stages of the disease, especially for general ophthalmologists [4, 5]. Taking this into account, it is essential to perform the correlation between structural and functional changes. The high cost can represent a limitation to the access of the referred diagnostic tools
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