18.4 External Photography, Nine-Gaze Motility Documentation & Image Management

Standardised external photography

External photographs are only useful if they are comparable. The single most common failure is a follow-up image taken at a different distance, angle or lighting, making any apparent change uninterpretable.

The five constants to fix and record:

1. Distance — mark a fixed camera position or use a fixed focal length and a repeatable framing.
2. Lighting — consistent, even, ideally two-source to avoid hard shadows; avoid direct flash into the eyes for lid work, which flattens contour.
3. Background — plain, non-distracting, consistent colour.
4. Head position — the Frankfort horizontal plane (the line from the inferior orbital rim to the superior margin of the external auditory meatus held horizontal) is the standard reference.
5. Gaze — primary position unless a specific gaze is being documented; state which.

Standard views:

The nine-gaze motility series

Documenting motility photographically is a standard request in strabismus, cranial nerve palsy and thyroid eye disease.

Order and content: capture primary position first, then the eight surrounding directions — right, left, up, down, and the four oblique positions (up-right, up-left, down-right, down-left) — with the patient following a target while keeping the head still. Keep the camera and distance fixed for all nine frames so they can be tiled into a comparable montage.

Technique points:

• Hold the patient's head still — many patients turn the head instead of moving the eyes, which destroys the measurement.
• Ensure the corneal light reflex is visible in every frame; it is the reference for judging alignment.
• For a ptosis series, hold the brow to eliminate frontalis compensation when levator function is being assessed.
• For a suspected superior oblique palsy, add head tilt right and head tilt left frames.
• Note whether the patient is wearing their habitual correction, and whether any prism is in place.

Oculoplastic measurements captured photographically

MRD1 is the measurement that quantifies ptosis, and because it is referenced to the corneal light reflex rather than to the lower lid, it is unaffected by lower lid position — unlike palpebral fissure height. Photographing with a millimetre rule held in the plane of the lid, or with a known scale in frame, allows these to be measured from the image.

Image management and DICOM

DICOM (Digital Imaging and Communications in Medicine) is the standard that keeps an image bound to its patient and its acquisition parameters.

Metadata every ophthalmic image should carry:

The laterality problem. Automatic laterality tagging depends on the device knowing which eye was imaged, which in turn depends on the operator selecting correctly at the console. Verify laterality against the patient and against the anatomy in the image, not against the worklist. In a fundus image the disc lies nasal to the macula, so in a right eye the disc appears to the left of the macula in the standard orientation and in a left eye to the right — a five-second check that catches mislabelling.

Storage and workflow rules:

1. Transfer images to the permanent archive promptly; do not leave them on the device.
2. Never store patient images on personal devices or personal cloud accounts.
3. Use the PACS or EMR image module, not a shared network folder without access control.
4. Do not alter images other than by the accepted adjustments (brightness, contrast, cropping) — and where local policy requires, note that adjustments were made. Never clone, remove or add content.
5. Retain the original unmodified file.
6. Back up according to institutional policy and jurisdictional retention requirements.
7. Delete images captured in error promptly and deliberately, with a record of why, rather than leaving unlabelled files in the archive.

Quality assurance

A routine photographic quality assurance programme includes:

• Daily: check the objective lens for dust and fingerprints; confirm the eyepiece reticle focus; verify the date and time on the device.
• Per session: review each image immediately after capture and retake rather than discovering the problem when the clinician opens the file.
• Periodically: colour balance check against a known standard; flash output check; confirm calibration for any measurement overlay; verify DICOM transmission to the archive.
• Per manufacturer schedule: professional servicing and calibration, with the service record retained.

Consent, dignity and identifiability

External photographs include the face and are directly identifiable. Beyond routine clinical consent:

• Explain what will be photographed and why, before the camera is raised.
• Obtain explicit written consent for any use outside the clinical record — teaching, publication, conference presentation or marketing — and record it.
• Offer to photograph only the periocular region where a full-face image is not required.
• Manage the patient's dignity: remove headwear only with permission, explain before touching the face to hold a brow or lid, and offer a chaperone where appropriate.
• Remember that video is more identifiable than a still image, may capture speech, and warrants its own explicit consent.
• A patient may withdraw consent for non-clinical use at any time; the clinical record itself is retained under normal medical records rules.