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Independent Effects of Blood Pressure on Intraocular Pressure and Retinal Ganglion Cell Degeneration: A Mendelian randomization study

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Peer-reviewed

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Authors

Rajasundaram, Skanda 
Segrè, Ayellet V 
Gill, Dipender 
Woolf, Benjamin 
Zekavat, Seyedeh M 

Abstract

Purpose: To investigate the causal effect of elevated blood pressure on primary open-angle glaucoma (POAG) and POAG endophenotypes. Methods: Two-sample Mendelian randomization (MR) was performed to investigate the causal effect of elevated systolic blood pressure (SBP) (N=757,601) and diastolic blood pressure (DBP) (N=757,601) on intraocular pressure (IOP) (N=139,555), macular retinal nerve fiber layer (mRNFL) thickness (N=33,129), ganglion cell complex (GCC) thickness (N=33,129), vertical cup-to-disc ratio (VCDR) (N=111,724), and POAG liability (Ncases=16,677, Ncontrols=199,580). The primary analysis was conducted using the inverse-variance weighted approach. Sensitivity analyses were performed to investigate robustness to horizontal pleiotropy, winner’s curse, and collider bias. Multivariable MR was performed to investigate whether any effect of blood pressure on retinal ganglion cell degeneration was mediated through increased IOP. Results: Increased genetically predicted SBP and DBP associated with an increase in IOP (0.17mmHg [95% CI=0.11 to 0.24] per 10mmHg higher SBP, P=5.18x10-7, and 0.17mmHg [95% CI=0.05 to 0.28mmHg] per 10mmHg higher DBP, P=0.004). Increased genetically predicted SBP associated with a thinner GCC (0.04µm [95% CI=-0.07 to -0.01µm], P=0.018) and a thinner mRNFL (0.04µm [95% CI=-0.07 to -0.01µm], P=0.004), an effect that arises independently of IOP according to our mediation analysis. Neither SBP nor DBP associated with VCDR or POAG liability. Conclusions: These findings support a causal effect of elevated blood pressure on retinal ganglion cell degeneration that does not require intermediary changes in IOP. Targeted blood pressure control may help preserve vision by lowering IOP and, independently, by preventing retinal ganglion cell degeneration, including in individuals with a normal IOP.

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Journal Title

Investigative Ophthalmology and Visual Science

Conference Name

Journal ISSN

0146-0404
1552-5783

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Publisher

The Association for Research in Vision and Ophthalmology

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Sponsorship
Wellcome Trust (225790/Z/22/Z)