For the photographs the patient places his or her chin in a chinrest while pressing their forehead to the forehead rest for several minutes each eye. Blinking is allowed but the patient must remain as still as possible for the best and quickest images to be captured. There will be some bright lights when photographs are taken which is necessary for the light to reach the back of the eye. The number of photographs needed for each eye is dependent on what each patient’s doctor is looking for.
Fundus cameras are used by optometrists, ophthalmologists, and trained medical professionals to monitor the progression of an ocular disease as well as to diagnose certain diseases. Images are often taken to create a baseline to document the current state of the retina and optic nerve in case of future changes. Photographs can be used to measure the ratio of the optic cup, documenting a choroidal nevus or tracking dry ARMD are some of the more common uses of fundus photography.
A fundus camera, or retinal camera, is a specialized low power microscope with an attached camera designed to photograph the interior surface of the eye, including:
- Optic disc
- Posterior pole (i.e. the fundus).
Slit Lamp Camera
The slit lamp camera is an instrument that consists of a high-intensity light source that can be focused to shine a thin sheet of light into the eye. This camera photographs the frontal structures of the human eye, which includes:
The binocular slit-lamp examination provides a stereoscopic magnified view of the eye structures in detail, enabling anatomical diagnosis to be made for a variety of eye conditions.
The slit beam serves as a great tool for documentation and can be manipulated to obtain a multitude of visual effects, which can illuminate the area of interest. This can help to dictate the severity of a disease, like how many layers a mass may be penetrating through, how narrow the anterior chamber angle is, or how dense a cataract is.
Some parts of the eye cannot be seen using a slit lamp camera, which only provides a straight forward view of the eye. If other views are needed, a gonio lens, which uses a special multi-mirror view, may be used. Tiny tilted mirrors are able to capture additional parts of the eye such as the iris, ciliary body and even the vitreous. Depending on what will be focused on in the eye, the patient may be undilated or dilated.
During this test the eye is numbed and the gonio lens is placed directly onto the cornea. A thick gel, which is used for dry eye, may be used. The photographer will tilt the gonio as needed, while taking the necessary images. The patient will sit in a chair with his or her chin on a rest which holds the head still during the process. The patient will feel some pressure during the test but no pain. The test typically lasts only a few minutes per eye.
Fundus Autofluoresence (FAF)
Fundus Autofluoresence (FAF) is a non-invasive test that is performed with a short bright light, while the patient is dilated, to allow the most light into the eye. FAF is a type of photography that uses a special light to evaluate highly fluorescent ocular structures. This test checks the presence of fluorophores in the eye. Fluorophones are chemical structures that possess fluorescent properties when exposed to light of an appropriate wavelength.
Fundus Autofuloresence may be used to evaluate the presence of:
- Optic Nerve Drusen
- Plaquenil Toxicity
- Macular Dystrophies
- Retinitis Pigmentosa
- White Dot Syndromes
MultiColor uses three types of light, which are not harmful to the eye, that combine to create a beam which evaluates different depths of the retina. MultiColor images can highlight structures and pathologies that may not be visible with infrared imaging or fundus photography. MultiColor imaging is performed on the Spectralis OCT machine and is often added to compliment the regular scans which evaluate the thickness of the optic nerve and retina.