Detection of retinal and peripheral microvascular abnormalities in ankylosing spondylitis patients * a proof of concept study.

Ankylosing spondylitis (AS) is a rheumatic disease that causes chronic
inflammation of the spinal- and sacroiliac joints and is associated with an
increased risk of cardiovascular diseases. Accumulating evidence suggests a
pivotal role of systemic inflammation in endothelial dysfunction, microvascular
abnormalities and eventually the development of cardiovascular disease (CVD).
However, in daily practice the early recognition of developing cardiovascular
diseases remains a challenge. The retinal vasculature is very accessible for
non-invasive visualization and provides a unique opportunity to study early
structural changes of the microcirculation. The association between
abnormalities of the retinal arterioles and venules and current and future
cardiovascular diseases have been extensively reported. Few studies have
reported on abnormalities of the retinal vasculature in chronic inflammatory
diseases.

Primary objective: To investigate whether AS patients have increased signs of
microvascular abnormalities of the retina, compared with healthy controls.
Secondary objectives: to investigate:
1. the peripheral microvascular function in AS patients, measured with reactive
hyperemia peripheral arterial tonometry (EndoPAT).
2. whether there is a relation between the retinal and peripheral microvascular
abnormalities.
3. gender differences in microvascular abnormalities.
4. the correlation between AS disease activity and microvascular abnormalities.
5. the association between the cardiovascular risk score and retinal vascular
caliber for both patients and controls.
6. differences in retinal vascular measurements between two types of fundus
cameras

cross sectional case-control design in which AS patients are compared with
gender- and age-matched healthy controls. Fifty-five patients and 110 controls
will be included and a male-female ratio of 1:1 will be pursued. All AS
patients undergo rheumatologic (short interview, physical examination, daily
care questionnaires), laboratory (regular tests according to standard care),
ocular assessment (inspection of the anterior eye chamber, fundus photos and a
normal and angio ocular coherence tomography scan (no Röntgen radiation)) and
EndoPAT assessment (specifically for this study) only once, on the same day.
The ophthalmologic data of the control group was already collected for other
study purposes.

The study exists of only one study visit that will approximately take 3 hours
in total. No invasive diagnostics will be used. The risk and burden of the
study procedures (ocular examination and EndoPAT assessment) is considered to
be negligible. The aspects that may cause (some) discomfort to the subjects are
a blurred vision during 1-4 hours after ocular assessment due to mydriatic eye
drops (standard procedure) and transient (maximally 5 minutes) paraesthesia of
one of the hands during the EndoPAT procedure.