Investigations: FFA, OCT, Ultrasound, Perimetry
Waht is Investigations ?
It is a fundal photography, performed in rapid sequence following intravenous injection of fluorescein dye. It provides three main information:
- the flow characteristics in the blood vessels as the dye reaches and circulates through the retina and choroid
- it records fine details of the pigment epithelium and retinal circulation that may not otherwise be visible
- give a clear picture of the retinal vessels and assessment of their functional integrity.
Optical Coherence Tomography(OCT)
Optical coherence tomography (OCT) is an optical signal acquisition and processing method. It captures micrometer-resolution, three-dimensional images from within optical scattering media (e.g., biological tissue). Optical coherence tomography is an interferometric technique, typically employing near-infrared light. The use of relatively long wavelength light allows it to penetrate into the scattering medium. Confocal microscopy, another similar technique, typically penetrates less deeply into the sample.
An eye and orbit ultrasound is a test that uses high-frequency sound waves to get measurements and produce detailed images of your eye and eye orbit. The orbit is the socket in your skull in which your eye sits.
Sometimes called eye studies, the procedure is usually performed by an ophthalmologist (a doctor specializing in diagnosing and treating eye disorders and diseases). Eye studies can also be performed by a technician in an office, outpatient centre, or hospital.
Our visual world is composed of images of colors, textures, edges and contrasts. In addition, these images may be moving or flickering. The goal of visual testing is to quantitate of these functions.
Traditionally we have tested visual function as visual acuity – the capacity to discriminate the fine details of objects and visual field – the portion of space in which objects are visible at the same moment during steady fixation of gaze in one direction. Color vision testing, flicker sensitivity, contrast sensitivity, pupillary responses and motion testing are some of the other methods of quantitating vision.
Perimetry is the systematic measurement of visual field function. The two most commonly used types of perimetry are Goldmann kinetic perimetry and threshold static automated perimetry. With Goldmann or “kinetic” perimetry, a trained perimetrist moves the stimulus; stimulus brightness is held constant. The limits of the visual field are mapped to lights of different sizes and brightness.