The Effects of Acute Intracranial Pressure Changes on the Episcleral Venous Pressure, Retinal Vein Diameter and Intraocular Pressure in a Pig Model

ABSTRACT

Purpose

Orbital veins such as the retinal veins and episcleral veins drain into the cavernous sinus, an intracranial venous structure. We studied the effects of acute intracranial pressure (ICP) elevation on episcleral venous pressure, intraocular pressure and retinal vein diameter in an established non-survival pig model.

Methods

In six adult female domestic pigs, we increased ICP in 5 mm Hg increments using saline infusion through a lumbar drain. We measured ICP (using parenchymal pressure monitor), intraocular pressure (using pneumatonometer), episcleral venous pressure (using venomanometer), retinal vein diameter (using OCT images) and arterial blood pressure at each stable ICP increment. The average baseline ICP was 5.4 mm Hg (range 1.5–9 mm Hg) and the maximum stable ICP ranged from 18 to 40 mm Hg. Linear mixed models with random intercepts were used to evaluate the effect of acute ICP increase on outcome variables.

Results

With acute ICP elevation, we found loss of retinal venous pulsation and increased episcleral venous pressure, intraocular pressure and retinal vein pressure in all animals. Specifically, acute ICP increase was significantly associated with episcleral venous pressure (β = 0.31; 95% CI 0.14–0.48, p < .001), intraocular pressure (β = 0.37, 95%CI 0.24–0.50; p < .001) and retinal vein diameter (β = 11.29, 95%CI 1.57–21.00; p = .03) after controlling for the effects of arterial blood pressure.

Conclusion

We believe that the ophthalmic effects of acute ICP elevation are mediated by increased intracranial venous pressure producing upstream pressure changes within the orbital and retinal veins. These results offer exciting possibilities for the development of non-invasive ophthalmic biomarkers to estimate acute ICP elevations following significant neuro-trauma.

KEYWORDS:

• Episcleral venous pressure
• intracranial pressure
• intraocular pressure
• retinal vein diameter
• biomarker

Acknowledgments

Study support: Lisa Reid and Toni Goeser (Department of Ophthalmology UNMC), Marsha Morien, Nathan Bills and Crystal Krause (Center for Advanced Surgical Techniques, UNMC).

Commercial relationships

Deepta Ghate MBBS, MD: Licensed technology with EON Reality Inc.

Sachin Kedar MBBS, MD: Licensed technology with EON Reality Inc.

Shane Havens MD: None

Shan Fan MD: None

William Thorell MD: None

Carl Nelson PhD: None

Linxia Gu PhD: None

Junfei Tong PhD: None

Vikas Gulati MD: None

Additional information

Funding

This study was supported by grant funding through Nebraska University Collaboration grant (Nebraska Research Initiative), Department of Neurological Sciences, Fremont Area Alzheimer’s Committee grant, Nebraska Tobacco Settlement Biomedical Research Development Fund [307 (NTSBRDF)], the National Eye Institute, [K23EY023266] and the National Institute of General Medical Sciences, [1 U54 GM115458], which funds the Great Plains IDeA-CTR Network. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.