A non-invasive imaging technique that combines the refractive principle of the slit-lamp with the magnification power of the microscope and allows monitoring and/or early detection of corneal cell damage through accurate endothelial cell density (ECD) measurements, as well as quantitative and/or qualitative analysis of other morphological parameters, such as cell shape variation from the ideal hexagonal shape (pleomorphism), cell size variation (polymegethism), and early detection of guttae (endothelial mounds caused by an accumulation of secretions, which can be an age-related change but can also be induced by trauma or inflammation or can be a precursor to corneal pathologies like Fuchs’ endothelial dystrophy). For specular microscopy analysis conducted at our center, DIRC will provide quantitative or qualitative values for all parameters listed above (including presence and extent of guttae), as well as an image quality rating (IQR) based on a standardized IQR-scale, and the relative standard deviation between ECD values.
Fluorescein Angiography (FA)
A diagnostic technique for examining the circulation of the retina using the dye tracing method. Sodium fluorescein is injected into the systemic circulation, and an angiogram is then obtained via digital photography. The angiogram captures the fluorescence emitted after illumination of the retina. Common capture system models accepted at the DIRC include those manufactured by Zeiss (FF3, FF4, FF45) and Topcon (50VT, 50IA, 50EX). Heidelberg cSLO systems are also accepted.
Color Fundus Photgraphy
A diagnostic technique using a fundus camera or retinal camera — basically, a low-power microscope with an attached digital camera specifically designed for fundus photography. The camera creates a photograph of the interior surface of the eye, including the retina, optic disc, macula, and posterior pole; in other words, what we know as the fundus. Common capture system models accepted at the DIRC include those manufactured by Zeiss (FF3, FF4, FF45) and Topcon (50VT, 50IA, 50EX). Heidelberg cSLO systems are also accepted.
Optical Coherence Tomography (OCT):
Fundus Autofluorescence (FAF)
A diagnostic technique for documenting the presence of fluorophores in the human eye. Fluorophores are chemical structures that exhibit fluorescence when exposed to light at an appropriate wavelength. The term autofluorescence is used to distinguish this type of fluorescence from that which occurs with the administration of fluorescent dyes, as in fluorescein angiography. Common capture systems accepted at the DIRC are those manufactured by Topcon and Zeiss (Flash) and Heidelberg Blue-light for cSLO.
An image analysis method with the ability to see, in real time, the retina under examination (using infrared light) and to project a defined light stimulus over an individual, selected location. The characterisitcs of fixation (stability) are easily and exactly quantified with microperimetry. MP1, which is being used for several studies at the DIRC, automatically compensates for eye movement during the examination with a software module that tracks the movement with respect to an initial frame. This quantifies the retinal threshold over the exact retinal points tested during the baseline examination. MP1 microperimetry allows quantification of retinal sensitivity in the macula using a numeric scale. The microperimetry capture system accepted at the DIRC is Nidek (MP1).
A scotoma is an area of vision loss at one fixed point, consisting of partially diminished vision surrounded by a field of normal, or relatively well-preserved vision. The color fundus photography scotoma montage depicts the different stages of visual function loss with progression of Diabetic Retinopathy.
A: Normal retina. B: Diabetes, but no retinopathy. C: Mild non-proliferative diabetic retinopathy. D: Moderate non-proliferative diabetic retinopathy. E: Severe non-proliferative diabetic retinopathy. ,F: Proliferative diabetic retinopathy.
At the DIRC we are able to identify and grade morphology of various structures in the anterior chamber angle (ACA). Key structures that are clearly delineated are the scleral spur, Schwalbe’s line, trabecular meshwork, and corneal endothelium. The DIRC is also able to perform various angle measurements, such as the angle opening distance, angle recess area, and trabecular iris space area and to quantify the angle recess. Furthermore, the DIRC actively participates in development of novel strategies including customization of imaging protocols to suit individual study requirements.
The anterior chamber OCT image identifies the scleral spur (yellow), trabecular meshwork (blue) and Schwalbe’s line (red). The green line indicates the corneal endothelium.
The DIRC, through the efforts of its research team, is in the process of assessing the ACA with different high-resolution, high-speed spectral-domain OCT instruments and comparing the ACA measurements obtained to identify the best OCT instruments for collection of anterior segment OCT data of interest.
The green polygon-shaped region is the angle space area. The calculations detailed in the white box in the lower right corner are derived from a custom-designed software program developed by DIRC personnel for a particular study to assist in performing critical measurements.
An OCT image taken by a different capture system than Image 1, allowing precise calculation of the positions of Schwalbe’s line, trabecular meshwork, Descemet’s membrane, and corneal endothelium and of their point of convergence.