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Light will be bent towards the base and the image will be shifted towards the apex. In an eyeglass prescription, the base is typically specified as up, down, in, or out, but left and right are also used sometimes. Whether a patient needs this type of correction can be determined by a variety of methods.
Certain abbreviations are current within the profession of optometry. They are used to denote clinical conditions, examination techniques and findings, and various forms of treatment.
Prism and Base Prism refers to a displacement of the image through the lens, often used to treat strabismus and other binocular vision disorders. The prism value is measured in prism diopters, and Base refers to the direction of displacement.
The prism cover test ( PCT) is an objective measurement and the gold standard in measuring strabismus, i.e. ocular misalignment, or a deviation of the eye. [1] It is used by ophthalmologists and orthoptists in order to measure the vertical and horizontal deviation and includes both manifest and latent components. [1]
Scintillating scotoma is a common visual aura that was first described by 19th-century physician Hubert Airy (1838–1903). Originating from the brain, it may precede a migraine headache, but can also occur acephalgically (without headache), also known as visual migraine or migraine aura. [4]
Most stereoscopic methods present a pair of two-dimensional images to the viewer. The left image is presented to the left eye and the right image is presented to the right eye. When viewed, the human brain perceives the images as a single 3D view, giving the viewer the perception of 3D depth.
Ophthalmology. Hypertropia is a condition of misalignment of the eyes ( strabismus ), whereby the visual axis of one eye is higher than the fellow fixating eye. Hypotropia is the similar condition, focus being on the eye with the visual axis lower than the fellow fixating eye.
Fixation disparity is a tendency of the eyes to drift in the direction of the heterophoria. While the heterophoria refers to a fusion-free vergence state, the fixation disparity refers to a small misalignment of the visual axes when both eyes are open in an observer with normal fusion and binocular vision. [1]
There are numerous higher-order aberrations, of which only spherical aberration, coma and trefoil are of clinical interest. Spherical aberration is the cause of night myopia and is commonly increased after myopic LASIK and surface ablation. It results in halos around point images.
In ophthalmology, gonioscopy is a routine procedure that measures the angle between the iris and the cornea (the iridocorneal angle), using a goniolens (also known as a gonioscope) together with a slit lamp or operating microscope. [1] [2] Its use is important in diagnosing and monitoring various eye conditions associated with glaucoma .