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Ceren Durmaz Engin, Rukiye Aydin, Lama A Al-Aswad, James D Auran, Dana Blumberg, George A Cioffi, Jeffrey M Liebmann, Tongalp H Tezel, Gulgun Tezel; Retinal inner plexiform layer (IPL) alterations in patients with glaucoma. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2115.
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© ARVO (1962-2015); The Authors (2016-present)
Experimental evidence suggests that optic nerve axon injury triggers early alterations of RGC synapses prior to manifest RGC death and axon loss in glaucoma. For testing the relevance of experimental observations to human glaucoma, this retrospective cohort study aimed to determine glaucoma-related changes in IPL where RGC dendrites are arborized to establish synaptic connections with bipolar and amacrine cells.
After exclusion of patients with systemic diseases, myopia, or retinal pathologies, 15 eyes of 11 patients with primary open-angle glaucoma, who were examined one year apart, were included in this pilot study. RNFL, RGCL, and IPL thicknesses were measured in the macular area by SD-OCT. In addition to automated thickness measurements, SD-OCT images were analyzed by linear densitometry, and IPL thickness, density, reflectance volume, and pattern were assessed for segmented layers on nasal and temporal sides at a distance of 1, 1.5, and 2 mm from the center of the macula. For functional evaluation, visual field parameters obtained by standard automated perimetry on the same day as SD-OCT imaging were analyzed.
No significant alteration was detectable in visual field function, or RNFL, GCL, or IPL thickness of the studied glaucoma patients (age: 68±6.3 years; female/male: 6/5) who were on topical IOP-lowering treatment through the one-year follow-up period (p>0.05). However, linear densitometry-based analysis detected a trend toward increased IPL density (p<0.04) and altered double-peak pattern of IPL reflectance at multiple locations, at some of which regression analysis found an association with visual field sensitivity (R=0.44, p=0.02).
Findings of this study support IPL alterations in the absence of detectable alterations in RGCL and RNFL in human glaucoma. The glaucoma-related increase in IPL density, along with the altered reflectance pattern, may suggest dendritic remodeling (and accompanying mitochondrial redistribution for synapse maintenance and/or glial response for tissue cleaning), rather than dendrite atrophy. Unlike animal models, detected alterations may reflect a longer process prior to synaptic pruning and function loss in human glaucoma treated to lower IOP. These findings encourage further analysis to determine whether IPL alterations may serve as a biomarker to improve clinical diagnosis and follow-up of glaucoma.
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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