Retinal Imaging for Systemic Inflammation in Endometriosis

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.

• Change from Baseline in Choroidal Thickness [Time frame: Baseline; and post-intervention at 3-6 months after surgery or new hormonal treatment; or 4-8 weeks after completion of an endometriosis-related clinical trial; assessments occur within up to 3 years of baseline.]
• Change from Baseline in Retinal Thickness [Time frame: Baseline; and post-intervention at 3-6 months after surgery or new hormonal treatment; or 4-8 weeks after completion of an endometriosis-related clinical trial; assessments occur within up to 3 years of baseline.]
• Change from Baseline in RNFL Thickness [Time frame: Baseline; and post-intervention at 3-6 months after surgery or new hormonal treatment; or 4-8 weeks after completion of an endometriosis-related clinical trial; assessments occur within up to 3 years of baseline.]
• Change from Baseline in Macular Volume [Time frame: Baseline; and post-intervention at 3-6 months after surgery or new hormonal treatment; or 4-8 weeks after completion of an endometriosis-related clinical trial; assessments occur within up to 3 years of baseline.]
• Change from Baseline in Retinal Vessel Density [Time frame: Baseline; and post-intervention at 3-6 months after surgery or new hormonal treatment; or 4-8 weeks after completion of an endometriosis-related clinical trial; assessments occur within up to 3 years of baseline.]
• Correlation Between Serum C-reactive Protein and Choroidal Thickness (OCT) [Time frame: Baseline and post intervention (3-6 months after surgery or new hormonal treatment; or 4-8 weeks after completion of an endometriosis-related clinical trial; assessments occur within up to 3 years of baseline)]
• Correlation Between Serum C-reactive Protein and Retinal Thickness (OCT) [Time frame: Baseline; and post-intervention at 3-6 months after surgery or new hormonal treatment; or 4-8 weeks after completion of an endometriosis-related clinical trial; assessments occur within up to 3 years of baseline.]
• Correlation Between Serum C-reactive Protein and RNFL Thickness (OCT) [Time frame: Baseline; and post-intervention at 3-6 months after surgery or new hormonal treatment; or 4-8 weeks after completion of an endometriosis-related clinical trial; assessments occur within up to 3 years of baseline.]
• Correlation Between Serum C-reactive Protein and Macular Volume (OCT) [Time frame: Baseline; and post-intervention at 3-6 months after surgery or new hormonal treatment; or 4-8 weeks after completion of an endometriosis-related clinical trial; assessments occur within up to 3 years of baseline.]
• Correlation Between Serum C-reactive Protein and Retinal Vessel Density (OCT Angiography) [Time frame: Baseline; and post-intervention at 3-6 months after surgery or new hormonal treatment; or 4-8 weeks after completion of an endometriosis-related clinical trial; assessments occur within up to 3 years of baseline.]