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Courtney Lynne Ondeck, Alessandro Adad Jammal, Nara Ogata, Felipe Medeiros; Why do Some Glaucomatous Eyes Lose a Lot More Nerve Tissue than Others by the Time of First Appearance of a Visual Field Defect?. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4062.
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© ARVO (1962-2015); The Authors (2016-present)
It has been well-described that some eyes with glaucoma may lose a large proportion of retinal ganglion cells (RGCs) by the time a visual field defect becomes detectable on standard automated perimetry (SAP). However, although this is true for some eyes, others may lose only a relatively small number of RGCs until a defect becomes detectable. The purpose of this study was to investigate characteristics explaining why some eyes lose more nerve tissue than others by the time a visual field defect becomes apparent on SAP.
This was an observational cohort study. 53 eyes of glaucoma suspect patients were followed over a median of 6.7 years until the development of the first repeatable (3 consecutive) visual field defect on SAP, as defined by a PSD<5% or GHT outside normal limits. All eyes had retinal nerve fiber layer (RNFL) thickness measurements obtained by spectral-domain optical coherence tomography (OCT). Estimates of RGC counts at the time of first development of a visual field defect were obtained by a previously published method combining structure and function, and compared to those obtained from 124 age-matched healthy eyes. The pattern of glaucomatous damage to the optic nerve at the time of appearance of the first visual field defect was classified into diffuse versus localized, based on masked review of optic disc stereophotographs. Eyes classified into the localized group had rim notching or localized RNFL defects.
At the time of first development of a visual field defect, the average RGC count was 652,057 ± 115,829 compared to 910,584 ± 142,412 for healthy eyes, for an average loss of 28.4%. 17 of the 53 (32%) eyes had localized neural loss, whereas 36 (68%) had diffuse rim loss on stereophotos. Eyes with diffuse loss had significantly greater average loss of estimated RGC counts compared to those with localized defects (32.6% vs. 19.4%; P<0.001) at the time a first visual field defect was detected.
Eyes that show a pattern of diffuse neuroretinal rim loss tend to show greater loss of neural tissue by the time a visual field loss becomes first apparent on SAP compared to those showing localized neural damage.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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