Imaging the choroidal microvasculature in intensive and high dependency care unit patients: a pilot study

OBJECTIVES: Microcirculatory dysfunction drives the end-organ pathophysiology of circulatory shock but is not reflected within existing clinical indices of perfusion, such as blood pressure. The choroidal vasculature of the retina can be measured non-invasively and we hypothesised that this may reflect dysfunction in other organs. We tested the feasibility of measuring the choroid in intensive care and explored associations between choroidal measurements and clinical parameters. DESIGN: A pilot study of optical coherence tomography conducted in a sample of general intensive care unit (ICU) patients. SETTING: A tertiary mixed ICU within the UK. PARTICIPANTS: 15 patients were recruited. One patient was excluded following withdrawal of active treatment. 12/14 (86%) of the remaining patients had successful baseline imaging and 6 (40%) of these had follow-up imaging within intensive care. These patients had a mean age of 56.3 years, were 71% (10/14) male and mean Acute Physiology and Chronic Health Evaluation 2 (APACHE2) score on ICU admission was 20.4. OUTCOME MEASURES: Choroidal anatomy, including choroidal and suprachoroidal thickness, as well as volumetric analysis of intrachoroidal blood vessels, was assessed using automated image segmentation along with clinical, physiological and biochemical data at ICU admission and after an interval of 12-72 hours. Feasibility and safety data were assessed throughout ICU admission. RESULTS: Baseline choroidal vascular index and choroidal thickness were positively associated with fluid balance, and negatively with APACHE2 score, haematocrit and albumin content. A measurable suprachoroidal space was seen in nine (75%) patients (range 25.0-110.0 microns) and was inversely associated with heart rate. There was substantial intraindividual variation in choroidal measurements over time. There were no safety concerns. CONCLUSIONS: Measuring the choroid is feasible in patients with Intensive Care Society Level 2 or Level 3 requirements. The suprachoroidal space may be markedly enlarged in these patients. Exploratory associations with systemic variables suggest that the choroid may provide information about the microvascular function of other major organs. Size and change of choroidal measurements may reflect perfusion pressure and vascular leakage.