Ophthalmic Imaging Glossary
Anterior Segment - cornea, iris, lens and associated structures of the eye
Cataract - An opacity of the lens of the eye.
Choroid - The layer underneath the retina.
Cornea - The transparent dome on the front of the eyeball.
Dilation - Expansion of the pupil using eye drops to allow observation of the lens and retina.
Fixation - Ability of the eye to maintain a fixed orientation.
Fluorescein Angiography (FFA) - Angiography is the definition of a vessel or structure using
a contrast medium. Contrast medium (sodium fluorescein dye) is injected into a vein in the
patients arm and timed photographs are taken using a fundus camera or SLO system.
Fluorescein angiography is an important ophthalmic diagnostic test used to examine the blood
vessels and associated structures of the retina. It is used to diagnose sight threatening
ophthalmic conditions and to locate areas that require treatment.
Fundus Camera System - A modern fundus camera system is a semi-mobile floor mounted
ophthalmic instrument costing £50,000. This complex system is used to produce highresolution photographs of the patient’s retina.
Fundus Photography - Photography involves the patient’s pupils being dilated, the patient’s
head is immobilized and the camera positioned close to the eye. The photographer observes
the retina by adjusting illumination and carefully positioning the eye using external & internal
fixation points.
Gonio Photography – Photography that involves the use of a contact lens that is in direct
ocular contact.
Heidelberg Retina Angiograph (HRA) – The HRA is a floor mounted imaging system that
comprises a laser imaging unit, patient head support and computer workstation with an image
database. Diagnostic capabilities include auto fluorescence, stereo and wide field imaging, and
high-speed angiography.
Heidelberg Retinal Tomography (HRT) - The HRT is a floor mounted imaging system that
comprises a laser imaging unit, patient head support and computer workstation with an image
database. It produces three-dimensional images of the optic nerve and structural data that are
used to monitor the subtle changes caused by raised internal pressure within the eye of a
patient with glaucoma.
Department of Medical Photography
October 2004
Indocyanine Green Angiography (ICG) - Angiography is the definition of a vessel or
structure using a contrast medium. Contrast medium (Indocyanine Green) is injected into a
vein in the patients arm and timed photographs are taken using a fundus camera or SLO
system. ICG Angiography is an important ophthalmic diagnostic test used to examine the
blood vessels and associated structures of the choroid. It is used to diagnose sight threatening
ophthalmic conditions and to locate areas that require treatment.
Iris - The coloured part of the eye that expands and contacts to regulate the amount of light
entering the eye through the pupil.
Lens - The transparent structure behind the iris and pupil of the eye that focuses light onto the
retina.
Optical Coherence Tomography (OCT) - OCT is a non-destructive imaging technique that
uses the optical backscattering of light to rapidly scan the eye and describe a pixel
representation of the anatomic layers within the retina. Each of these ten important layers can
be differentiated and their thickness can be measured.
Ophthalmic Angiography - Refers to both Fluorescein and ICG Angiography.
Pupil - The circular opening in the centre of the iris through which light passes into the eye.
Retina - The retina is the internal back surface of the eye containing the light sensitive nerve
layer.
Scanning Laser Ophthalmoscope (SLO) – An instrument that uses low powered lasers to
image the retina or choroid.
Slit-Lamp Photography - A slit -lamp camera is static floor mounted ophthalmic instrument
costing £18,000. It is used to produce high magnification photographs of the patient’s cornea,
iris, lens and eyelids. Photography involves delicate adjustment of illumination and careful
positioning of the patients eye.
Specular Microscopy - The specular microscope camera is a static floor mounted ophthalmic
instrument costing £10,000. It is used to produce very high magnification photographs of the
cell layer (endothelium) on internal back surface of the patient’s cornea. The photographer
applies anaesthetic drops to the patient’s cornea (training necessary) and places the camera
lens cone in direct contact with the eye. The photographer uses the photographs to produce a
cell density count, which allows the doctors to assess corneal health and decide if the patient
requires a corneal graft.
Department of Medical Photography
October 2004
Department of Medical Photography
October 2004