Scheimpflug ocular imaging is an eye test where a special camera is used to take 3D images of the anterior part of the eye. The images produced provide anterior and posterior surface topography, including the tangential, curvature, and axial maps.
The special camera used during the test rotates as it takes images of corneal cross-sections at differently titled angles illuminated by slit-beams. This creates an optic section of the cornea and lens.
Scheimpflug photography differs from traditional film. In traditional photography techniques, the film and lens plane, and the plane of sharp focus are all parallel. In Scheimpflug, the lens and planes aren’t parallel. Instead, the plane of the lens is at an angle and it intersects both the film plane and focal plane. This means that the depth of field (DOF) is extended, aiding in imaging from the anterior corneal surface to the posterior lens surface.
Scheimpflug imaging devices are developed to operate on a system created in 1904 by an Army Captain called Theodor Scheimpflug. At the moment of its inception, the system was used to correct any distortions in aerial photographs. It was later adapted for ocular imaging. The Scheimpflug technique is also used by landscape and architectural photographers to extend DOF without using a small aperture.
Also Known As
- Scheimpflug photography
- Scheimpflug analysis
- Scheimpflug corneal tomography
Scheimpflug ocular imaging is a simple, non-invasive test that doesn’t need a specialist to conduct. However, for proper results interpretation, it is recommended that it is done at the eye doctor’s office by:
- A technician
- An ophthalmologist
- An optometrist
Because the cornea is curved in shape, it is often difficult to capture clear images of it. This is why Scheimpflug’s analysis is essential. Scheimpflug accurately measures central corneal thickness, intraocular pressure (IOP), and anterior chamber depth. Scheimpflug is considered more accurate when compared to other tests such as ultrasonography and MRI.
There are various reasons why Scheimpflug ocular imaging may be conducted by an eye doctor such as:
- To diagnose glaucoma
- To map corneal topography
- Planning for refractive eye surgery (e.g. LASIK) - This helps the eye doctor decrease or eliminate the patient’s dependency on glasses or contact lenses.
- Early keratoconus detection - This is an eye disorder that results in progressive thinning of the cornea, which causes a cone-like shape on the surface of the eye. It usually results in blurry/double vision, myopia, and light sensitivity.
- Keratitis detection - This is the inflammation of the cornea, usually symptomized by redness of the eye.
- Check for cataracts - This the clouding of the lens of the eyes symptomized by clouded, blurred, or dim vision.
- Check on the severity of Fuchs endothelial dystrophy - This is an eye disease that affects the cornea. The first symptom is blurry vision in the morning that clears up as the day goes on. People with Fuchs endothelial dystrophy are usually also sensitive to bright lights.
One of the limitations of Scheimpflug is that its measurement can be affected by corneal parameters like central corneal thickness (CCT). Another limitation is that it relies on the fixation of the eye.
Preparation and expectation
The test does not require the patient to do anything special before it. Because the procedure is non-contact, it is comfortable for patients who undergo the procedure. It also takes a short time, 2 seconds for each eye.
Types of examination
There are two types of Scheimpflug imaging systems that can conduct Scheimpflug ocular imaging:
- Single rotating Scheimpflug imaging system
This examination uses a Scheimpflug camera, which rotates to provide a 3D image of the anterior eye. The rotational Scheimpflug camera takes between 25-50 cross-sectional images in 2 seconds at angles between 0 to 180°. Installed software is then used to construct the three‐dimensional image. An example of a camera that uses this is the Pentacam.
- Dual rotating Scheimpflug imaging system
This type of imaging system uses two Scheimpflug cameras at the same time as well as a Placido disk. This combination helps to improve the accuracy of the curvature information on the central cornea. An example of a camera that uses this is the Galilei.
The patient will be asked to sit in front of the Scheimpflug camera. The patient will then lean forward and rest their chin on the chin rest and push their forehead all the way forward to ensure maximum support. They will then be instructed to look straight ahead at a black point in the dome-shaped camera.
The eye specialist controls the camera using a joystick. Once the optimal position is reached, the camera automatically takes the pictures. At this point, the patient is asked not to blink or move their gaze. This only takes two seconds. Once the readings are recorded, the eye specialist will repeat on the other eye.
Results are considered normal when no peculiarities are observed in the 3D image.
If the results are abnormal, they may indicate one of the following eye disorders:
- Intraocular lens tilt (IOL)
- Fuchs endothelial dystrophy
There are no known complications associated with this procedure.