Oxymap - Analysing oxygenation in treated and untreated vitreoretinopathies and oxygen related diseases in adults.

The oxygen metabolism of the retina plays a key role in many ocular diseases in
children and adults. Imbalance between the retinal demand and the supply of
oxygen to the retina may lead to ischemia. This will stimulate the production
of vasoactive factors such as Vascular Endothelial Growth Factor (VEGF)
resulting in neovascularisation. These newly formed vessels are of bad quality
not only leading to subretinal leakage of fluid and protein but also to
insufficient oxygen distribution to the retina. Ocular diseases in which the
oxygen metabolism plays an important role in their aetiology have a major
contribution to visual impairment or blindness. Some of these ocular diseases
develop shortly after birth or in early childhood, for example Coats disease
and retinopathy of prematurity (ROP). Even after successful treatment at an
early stage, these diseases can re-activate in adulthood. Although it is known
that oxygen plays a major role in the development of these diseases, the exact
aetiology is not fully understood.
Furthermore, a recent pilot study has shown that oxygen saturation levels in
the retinal vessels are decreased in amblyopic eyes, in contrast to their
healthy, non-amblyopic eyes. This indicates that the oxygen metabolism might
also play a role in the development of amblyopia. Therefore, a better
understanding of the oxygen-metabolism of the eye in these specific diseases
will lead to an increased insight, thereby improving their management and
making early detection of re-emerging disease possible. Since recent years,
non-invasive retinal oximetry has become available to measure the relative
saturation levels in the retinal blood vessels.

The retinal oximetry
These non-invasive retinal oximeters measure the relative oxygen saturation
levels in the blood vessels of the retina by means of different wavelength
imaging. The Oxymap T1 is developed by the University of Reykjavik; this
instrument uses two different wavelengths of light (570nm and 600nm) to capture
images. The difference in the light reflection of the oxyhaemoglobin in the
arteries (highly oxygenated) and the deoxyhaemoglobin in the venules
(less-oxygenated) allows for measurements of the oxygen saturation of the
retinal vessels by means of a (Oxymap) software algorithm. This algorithm
calculates the optical density (OD) derived from both fundus images, resulting
in a pseudocolor map of the oxygen saturation levels of the blood vessels in a
fundus image

The objective of this study is to analyse the retinal oxygenation in adults
with the Oxymap T1 in patients with amblyopia and untreated or treated
(vitreo-) retinopathies and compare them to a reference group of healthy eyes
of amblyopic and Coats patients.

This study is a prospective observational case series of adult patients with
oxygen-related ocular diseases. Eligible patients will be invited by the
treating ophthalmologist or (sub) investigator to participate in the study.
When possible, all images will be obtained during regular consultation of the
patients at the outpatient clinic of the department of ophthalmology of the
LUMC. However, adult patients with (un)treated ROP and Coats disease are scarce
in number and frequency of regular consultations is low. Patients will be
invited in writing if there is no consultation scheduled at the department of
Ophthalmology of the LUMC within a reasonable timeframe. In case of a writing
invitation for participation of the study, the additional visit will replace
their regular upcoming visit. The imaging protocol requires four additional
Oxymap images apart from the standard fundus images taken at regular
consultations. The Oxymap imaging will be combined with the regular
ophthalmological consultations. Therefore, the patients will be followed during
the research period with multiple imaging sessions.

There are no additional risks. Dilation of the pupils is part of the routine
ophthalmological examination. Patients with Coats disease and (treated) ROP
need regular consultations, mostly on a yearly basis. If patients consent with
an additional ophthalmologic consultation with fundus images and additional
Oxymap images, they will receive a full routine ophthalmologic consultation.
During a routine ophthalmologic consultation pupils are dilated with
mydriatica. The risk of side effects of these mydriatica is extremely low
Patients with the studied diseases can benefit greatly from the obtained
insight in their disease, due to the implications this might have for early
detection of recurrences and possible treatment.