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Special Testing

The UEC’s Imaging Center offers a variety of diagnostic testing. Your patient can be seen for testing only or for testing with interpretation by one of our clinicians who specializes in a specific diagnostic area. The diagnostic tests available through our Imaging Center include:

Structural Testing:

Spectral Domain OCT (Cirrus/Optovue)
Optical Coherence Tomography makes use of interferometry and optical reflectivity to assess and quantify the thickness and relative position of retinal tissue. The clinician is provided with a topographical map of the retinal tissue imaged. Commonly, macular edema and retinal nerve fiber layer thinning are quantified using this device. Spectral Domain OCT takes many more readings per second than earlier technologies (Stratus) and provides the clinician with a 3-dimensional topographical view of the retinal tissue of concern at a much higher resolution.

HRT 3
The Heidelberg Retinal Tomographer 3 uses confocal laser scanning technology to measure retinal contour, especially of the retinal nerve fiber layer (RNFL) as it converges at the optic nerve head. Changes in the optic nerve head and nerve fiber layer contour over time can be monitored.

GDx VCC
The GDx (Glaucoma Diagnosis) VCC (Variable Corneal Compensation) uses scanning laser polarimetry and the birefringent properties of the RFNL to assess RNFL thickness and check for changes (thinning or thickening) over time.

Optical Biometry IOL Master
Using the principle of laser interferometry, this device records a patient’s axial length, anterior chamber depth, and corneal surface curvature. These measurements are then incorporated as variables into a program which calculates the correct intraocular lens power to be inserted after cataract extraction.

Corneal Topography (Orbscan)
This device optically maps a patient’s entire corneal surface with respect to thickness, surface power, and contour. The contour and eccentricity of a patient’s anterior and posterior corneal surfaces can be assessed with this device. Common indications include determining a patient’s eligibility for refractive surgery and aiding in the diagnosis and management of corneal diseases, such as keratoconus.

Pachymetry
A Pachymeter uses the principle of ultrasound to determine a patient’s corneal thickness. A common indication for this procedure is determining a patient’s central corneal thickness as part of a glaucoma evaluation.

Ultrasound Biomicroscopy
The Ultrasound Biomicroscope (UBM) uses the principle of ultrasound to acoustically assess the characteristics and relative positions of the various structures of the anterior segment. In particular, the angle can be assessed as open, closed, or occludable.

A and B scan Ultrasonography
A Scan Ultrasonography uses the variable speed of sound through the different media of the eye to allow the clinician to assess the axial length. B Scan Ultrasonography uses the same principles to allow the clinician to assess the various structures of the globe and posterior segment. Commonly, retinal detachments and lesions suspected to be elevated are assessed with this technique.

Fluorescein Angiography
This procedure involves injecting a small bolus of fluorescein (a vegetable dye derivative) into a patient’s arm and photodocumenting, over time, the flow of the fluorescein through the choroidal and retinal vasculature. An exciter filter and a barrier filter are used to allow for the fluorescein to fluoresce and to block out all other wavelengths. Macular edema and vascular abnormalities, such as neovascularization, are commonly assessed by fluorescein angiography.

Digital Anterior and Posterior Photography
Photodocumentation has become part of the standard of care for several ocular conditions. Diseases and abnormalities of the cornea, angle, lens, and retina are documented by means of photography throughout our clinics. Optos panoramic viewing allows for 200° wide field color imaging through a pupil as small as 2mm diameter. With the Optos, we have the ability to perform fundus autofluorescence imaging.

Functional Testing:
Standard Automated Perimetry
Automated perimetry involves systematically quantifying a patient’s visual field by showing to an illuminated target against a defined background and recording the patient’s response. The target is shown at different intensities and positions in order to plot the extent of the patient’s visual field, as well as to define the patient’s threshold at each test position. Ocular and neurological conditions which can affect the visual field are commonly assessed in this way.

Manual Kinetic Perimetry                                
Manual Kinetic Perimetry involves a trained perimetrist who moves an illuminated target against a defined background. The extent of the visual field is mapped to targets of different sizes and brightness.  The results of this method are plotted in the form of isopters, which are lines of equal light sensitivity that, when plotted for each light brightness and size, resembles a topographic map with the peak at the most sensitive points. Ocular and neurological conditions which can affect the visual field are assessed in this way.

Automated Kinetic Perimetry                                  
Automated Kinetic Perimetry applies the same principles as manual kinetic perimetry however, instead of a trained perimetrist manually moving, choosing and displaying the targets, these functions are programmed into a computer. 

Frequency Doubling Technology Perimetry (FDT)
This technique for assessing a patient’s visual field involves the use of a target best described as a sine wave grating of a low spatial frequency which flickers at a high temporal frequency. This perimetric technique tests the magnocellular pathway because the target has a defined temporal frequency. This pathway may be damaged first in certain ocular and neurological conditions which affect the visual field.

VEP
Visually Evoked Potentials are cortical responses to visual stimuli, usually flickering lights, which are measured by means of electroencephalography focused on the occipital cortex. Conditions having the capacity to affect these potentials, such as stroke and demyelinating disease, can be assessed in this way. Cortical function in non-communicating patients can also be assessed with this technique.

ERG
Electroretinography is a technique used to assess the function of the neural cells of the retina, especially the photoreceptors, be means of quantifying their electric responses to visual stimuli. The procedure is done under photopic and scotopic conditions and is commonly used to aid in the diagnosis of and monitor for progression in many retinal degenerations and dystrophies, such as retinitis pigmentosa and cone dystrophies.

EOG
Electrooculography is an electrodiagnositc test that assesses the function of the retinal pigment epithelium.  The clinical application of this test is to help rule out one of the hereditary retinal diseases that often affects macular function, called Best Vitelliform Macular Dystrophy.  The test takes about 45 minutes and tests saccadic eye movements under scotopic and photopic conditions. It is usually performed in the Hereditary Eye Disease Clinic.