Optical coherence tomography (OCT) is the most recent imaging innovation in ophthalmology used to study the structure of the eye. Even more recent applications of this type of scan have been to study the anterior portion of the eye, but the primary usage has been for the evaluation of the retina, and more specifically the back of the eye. This portion of the eye is called the posterior pole and includes the macula and the optic nerve.
There is a great similarity between ultra-sonography and optical coherence tomography, in that they both image by reflecting an impulse of energy onto the subject matter being studied and analyzing the energy reflected back. The difference is that sonography uses sound waves, which can penetrate opaque matter, and OCT uses light waves, which only penetrate translucent matter. Because light waves have a much shorter wave length than sound waves, there is much greater/better resolution in image presentation.
The slit lamp is an instrument consisting of a high-intensity light source that can be focused to shine a thin sheet of light into the eye. It is used in conjunction with a biomicroscope. The lamp facilitates an examination of the anterior segment, or frontal structures and posterior segment, of the human eye, which includes the eyelid, sclera, conjunctiva, iris, natural crystalline lens, and cornea. The binocular slit-lamp examination provides a stereoscopic magnified view of the eye structures in detail, enabling anatomical diagnoses to be made for a variety of eye conditions. A second, hand-held lens is used to examine the retina.
In the most common sense, a Pupilometer is a tool for measuring pupillary distance (PD). It is used for fitting eyeglasses so that the lenses are centered in the visual axis. This is the most common nomenclature. It may also be used to verify a PD measurement taken from a millimeter ruler placed across the bridge of a patient's nose for distance and near focus.
Alternatively, a pupilometer is a type of pupil response monitor—a monocular device measuring the amount of dilation of the pupil in response to a visual stimulus. In ophthalmology, a pupillary response to light is differentiated from a pupillary response to focus (i.e. pupils may constrict on near focus, as with the Argyll Robertson pupil) in the diagnosis of tertiary syphilis. Although a pupillometer can be used, the diagnosis is often made with a penlight & near-point card.
Optos is a leading medical technology company for the design, development, manufacturing and marketing of ultra-widefield retinal imaging devices. The device produces a high resolution image, optomap, of up to 200 degrees of the retina in a single capture.
An autorefractor or automated refractor is a computer-controlled machine used during an eye examination to provide an objective measurement of a person's refractive error and prescription for glasses or contact lenses. This is achieved by measuring how light is changed as it enters a person's eye. The automated refraction technique is quick, simple and painless. After application of a cycloplegic agent to keep the ciliary muscle in relaxed position and avoid the erroneous diagnosis of a pseudomyopia, the patient takes a seat and places their chin on a rest. One eye at a time, they look into the machine at a picture inside. The picture moves in and out of focus as the machine takes readings to determine when the image is on the retina. Several readings are taken which the machine averages to form a prescription. No feedback is required from the patient during this process. Within seconds an approximate measurement of a person's prescription can be made by the machine and printed out or shared electronically with an Automated Refraction System.
A lensmeter or lensometer, also known as a focimeter, is an ophthalmic instrument. It is mainly used to properly orient and mark uncut lenses, and to confirm the correct mounting of lenses in spectacle frames. Lensmeters can also verify the power of contact lenses, if a special lens support is used.
The parameters appraised by a lensmeter are the values specified by an ophthalmologist or optometrist on the patient's prescription: sphere, cylinder, axis, add, and in some cases, prism. The lensmeter is also used to check the accuracy of progressive lenses, and is often capable of marking the lens center and various other measurements critical to proper performance of the lens. It may also be used prior to an eye examination to obtain the last prescription the patient was given, in order to expedite the subsequent examination.
Visual Field Machine
A visual field test is an eye examination that can detect dysfunction in central and peripheral vision which may be caused by various medical conditions such as glaucoma, stroke, brain tumours or other neurological deficits. The exam may be performed by a technician in one of several ways. The test may be performed by a technician directly, with the assistance of a machine, or completely by an automated machine. Machine based tests aid diagnostics by allowing a detailed printout of the patient's visual field.