There is increasing evidence that examining our eyes can tell us a lot of information about our health, and systemic diseases. Our plan is to compare the images taken of the back of eyes of women who have endometriosis with those of women who don't. We want to study what eyes can reveal about endometriosis by analyzing the retinal images from a simple noninvasive eye scan, that is already being routinely used to provide immediate clinical information in other groups of patients (eg. diabetic eye screening).

What this study is about Endometriosis is now understood to affect the whole body, not just the pelvis. Many individuals with endometriosis show signs of low-grade systemic inflammation. The eye offers clinicians a clear, painless window on tiny blood vessels. Modern retinal scans can measure structure and blood flow at the back of the eye within minutes. This study will test whether retinal scans can serve as a non-invasive read-out of systemic inflammation in endometriosis. If successful, this approach could support assessment and longitudinal monitoring.

What will happen in the study

This is an exploratory case-control study. Women with endometriosis and age-matched women without endometriosis will be invited for a research visit at the Queen's Medical Research Institute (QMRI), Edinburgh. All participants will undergo the following retinal imaging:

Optical Coherence Tomography (OCT): a quick scan showing retinal and choroidal layers.

OCT Angiography (OCT-A): a map of tiny retinal vessels without dye injections. Ultra-widefield (UWF) imaging (Optos): a large-field retinal image. Scans are painless, non-invasive, and similar to routine eye assessments. The eye-imaging component takes about 30-40 minutes; the entire visit lasts about 1 hour.

Participants with endometriosis will also complete a brief endometriosis-specific quality-of-life questionnaire (EHP-30) before imaging. A small blood sample (up to 40 mL) may be taken to measure C-reactive protein (CRP) and other inflammation markers immediately or in the future (with consent). Any surplus samples may be stored securely for related research. Healthy volunteers attend a single visit only. Participants with endometriosis may be invited for repeat assessments after treatment - for example, 3 - 6 months after surgery or initiation of new hormonal therapy, or 4 - 8 weeks after completing an endometriosis-related clinical trial - to repeat the same assessments.

Burden, risks, and discomforts Retinal imaging does not use ionising radiation and is considered low risk. Possible short-lived effects include eye strain or mild headache from fixation on a target light. Venepuncture may cause brief discomfort or mild bruising. Breaks will be scheduled if needed, and expected effects will be recorded in the study file.

Measurements and analyses Scan-derived measurements will include retinal thickness, retinal nerve fibre layer thickness, macular volume, choroidal thickness, and retinal micro-vessel features. Between-group differences (endometriosis vs controls) will be analysed. Associations with blood inflammation markers will be assessed, and changes after treatment will be evaluated.

Data handling and confidentiality Study data are recorded in a case report form and entered into a secure REDCap database hosted by the University of Edinburgh. Personal details (e.g., contact information) are stored separately on secure systems with restricted access. Research data are pseudonymised using study ID codes. Data are retained and archived according to University/NHS Sponsor policies and UK data-protection law. Selected anonymised data and samples may be shared with academic or industry partners as described in the consent documents. Participation is voluntary, and participants may withdraw at any time; data collected up to withdrawal are retained for scientific and regulatory integrity.

Oversight and approvals The study is co-sponsored by the University of Edinburgh and NHS Lothian (ACCORD) and conducted in line with Good Clinical Practice (GCP) and all required approvals. Monitoring or audit may occur according to Sponsor procedures. The study ends after the last participant's last visit; a summary will be provided to the Research Ethics Committee.

Inclusion Criteria:

1. Participants with a previous surgical or imaging diagnosis of endometriosis

   • Pre-menopausal women and those assigned female at birth
   • Aged 18 years and over
   • A past surgical or imaging diagnosis of endometriosis within the last 5 years from date of consent
   • Ability to understand and willingness to sign the informed consent form

2. Healthy volunteers

   • Women and those assigned female at birth
   • Aged 18 years and over
   • No history of endometriosis or chronic pelvic pain
   • Ability to understand and willingness to sign the informed consent form

Exclusion Criteria:

1. Participants with a previous surgical or imaging diagnosis of endometriosis

   • The subject has donated blood (450 ml) within the last 4 weeks

   • Known reproductive tract malignancy

   • Ocular Diseases:

     • Subjects with clinically diagnosed glaucoma, optic neuropathy, optic neuritis, cataracts, or other conditions that affect the ocular structures.
     • Subjects with age-related macular degeneration, retinal vascular diseases, or other retinal disorders.
     • Subjects with any other ocular conditions that may influence the retinal or optic nerve structure.

   • Refractive Errors:

     • Subjects with high myopia (>6 diopters) or high hyperopia (>3 diopters).
     • Subjects with significant astigmatism (>2 dioptres) or other refractive errors.

   • Ocular Surgery History: Subjects with a history of ocular surgery, particularly involving the lens, cornea, retina, or optic nerve (e.g., laser vision correction, retinal surgeries, etc.).

   • Subjects with significant ocular trauma, corneal abnormalities, or active ocular infections that may interfere with OCT imaging.

   • Subjects with diabetes mellitus

2. Healthy volunteers

   • The subject has donated blood (450 ml) within the last 4 weeks

   • Known reproductive tract malignancy

   • A history of symptoms suggestive of endometriosis or chronic pelvic pain

   • Ocular Diseases:

     • Subjects with clinically diagnosed glaucoma, optic neuropathy, optic neuritis, cataracts, or other conditions that affect the ocular structures.
     • Subjects with age-related macular degeneration, retinal vascular diseases, or other retinal disorders.
     • Subjects with any other ocular conditions that may influence the retinal or optic nerve structure.

   • Refractive Errors:

     • Subjects with high myopia (>-6 dioptres) or high hyperopia (>+6 dioptres).
     • Subjects with significant astigmatism (>2 dioptres) or other refractive errors.

   • Ocular Surgery History: Subjects with a history of ocular surgery, particularly involving the lens, cornea, retina, or optic nerve (e.g., laser vision correction, retinal surgeries, etc.).

   • Subjects with significant ocular trauma, corneal abnormalities, or active ocular infections that may interfere with OCT imaging.

   • Subjects with diabetes mellitus

Women and those assigned female at birth

This is a matched case-control study. We will recruit 50 women with endometriosis (case) and 50 women matched for age without endometriosis (controls).

What IPD: De-identified participant-level datasets and surplus biological samples as applicable.

With Whom/Conditions: Academic or industry partners, as described in the PIS/consent; no release of identifiable data; publications contain no personal data.

How/Where: Secure transfer under data-sharing agreements; data stored in validated REDCap with controlled access.

Selected anonymised data and samples collected or generated by the study may be shared with academic or industry partners within the UK from the start of the study (expected start date: 01/10/2025). Research data will be archived and stored on secure servers hosted by The University of Edinburgh (in Data Store) for 10 years.

Who can access: Authorized study team and Co-Sponsor (University of Edinburgh/NHS Lothian) for conduct/monitoring/audit/archiving; Research Ethics Committee and regulators may inspect records. External academic/industry collaborators may receive selected anonymised participant-level data and anonymised surplus samples per PIS/consent; identifiable data are not released.

What: De-identified eCRF data (demographics, clinical characteristics, retinal imaging metrics, questionnaire scores, lab reports) and, where applicable, anonymised surplus biosamples.

How: Internal data stored in validated REDCap on secure University servers with user authentication; personal identifiers held separately; participants assigned unique study IDs (pseudonymised). External sharing only in anonymised form, under Sponsor approval and data-sharing agreements, with secure transfer. Data controller: Co-Sponsor; retention: ≥5 years for personal data, 10 years for research data.