disc(redirected from optical disks)
Also found in: Dictionary, Thesaurus, Financial, Encyclopedia.
discFibrocartilaginous material between spinal vertebrae which provides a cushion-like support against shock
diskthat part of the receptacle surrounding the plant ovary which is fleshy and sometimes nectar-secreting.
Airy's disc Owing to the wave nature of light, the image of a point source consists of a diffraction pattern. If light passes through a circular aperture, the diffraction pattern will appear as a bright central disc, called Airy's disc, surrounded by concentric light and dark rings. Airy's disc receives about 87% of the luminous flux, the next concentric ring about 8%, and the next 3%. The radius of Airy's disc equals
choked d . See papilloedema.
cupped disc An enlarged and deepened excavation of the physiological cup. It may be physiological, or due to glaucoma (glaucomatous cup), or following atrophy of the optic nerve (as in papilloedema).
diffraction disc See Airy's disc.
Maxwell disc A rotating disc onto which differently coloured discs which are radially slit can be fitted together to overlap and divide the surface into sectors of different colours. It may be used to investigate colour mixture.
morning glory disc A congenital, usually unilateral, anomaly of the optic disc. It may be due to a failure of the embryonic fissure such that the optic disc and some peripapillary tissue prolapse posteriorly. The optic disc is abnormally large and a white-grey tuft of glial tissue covers its centre. The annular zone surrounding the disc has irregular areas of pigmentation and depigmentation. The optic disc thus resembles a morning glory flower. Patients present with reduced visual acuity and strabismus and, in about one-third of patients, retinal detachment.
optic disc Region of the fundus of the eye corresponding to the optic nerve head. It can be seen with the ophthalmoscope as a pinkish-yellow area with usually a whitish depression called the physiological cup. The optic disc has an area of about 2.7 mm2, a horizontal width of about 1.75 mm and a vertical height of about 1.9 mm. The optic disc is the anatomical correlate of the physiological blind spot. It is greatly affected in glaucoma, papillitis, Leber's hereditary optic atrophy. Syn. optic nerve head; optic papilla (this is not strictly correct because the disc is not elevated above the surrounding retina). See glaucomatous cup; optic disc drusen; neuroretinal rim; papilloedema; Swann's syndrome.
pinhole disc (ph) A blank disc with a small aperture (2 mm diameter or less) mounted in a trial lens rim. It is used to reduce the size of the blur circle in an ametropic eye. In this condition vision will improve giving an indication of the final visual acuity that will be obtained with corrective lenses. If no improvement occurs, the eye is amblyopic. This procedure is called the pinhole test.
Scheiner's disc An opaque disc in which there are two pinholes separated by a distance less than the pupil diameter. It is used to measure the dioptric changes during accommodation or to detect the type of ametropia (Fig. D6). See Scheiner's experiment.
situs inversus of the disc A congenital, usually bilateral condition in which the retinal vessels course nasally from the disc instead of temporally. It is often associated with congenital scleral crescent and myopic astigmatism.
stenopaeic disc 1. A pinhole disc. 2. A blank disc with a slit used in detecting and measuring the astigmatism of the eye (Fig. D7). Syn. stenopaeic slit. Note: also spelt stenopeic or stenopaic. See kinescope; stenopaeic spectacles.
tilted disc A congenital, bilateral condition in which the optic nerves insert obliquely into the globe. It is often associated with congenital scleral crescent and myopic astigmatism. The only sign is a bitemporal visual field defect (often upper temporal).
disc, disk (disk)
Patient discussion about disc
Q. Is degenerative disc disease and arthritis the same thing? My husband was recently in a auto accident at work. They did a CT Scan of his head and neck. The doctor said that the CT Scan found that he has arthritis in his neck. After receiving the report ourselves to take to another doctor it reads: "There is minimal early degenerative disc disease with osteophyte formation predominately at C5-6. " My husband never had a problem with his neck before the accident
Q. What alternatives are there for DDD.De generative Disc Disease? I can't sit upright for long periods of time, at times the symptoms are worse and then days and weeks where I feel fine. When I lean into my right legit alleviates it a little but it is excruciating when I shift weight. I also have to sleep with a pillow between my legs and have to shift frequently.I have a lot of strength in my legs and back. But if I stuck in my stomach more and curve my like doing a crunch. the pain is fine.
The option of surgery may be recommended if the conservative treatment options do not provide relief within 2 to 3 months. If leg or back pain limits normal activity, if there is weakness or numbness in the legs, if it is difficult to walk or stand, or if medication or physical therapy are ineffective, surgery may be necessary. You should dicucss this with an orthopedic surgeon.
Q. what does c4-5 mild central disk bulging impinging upon cervical cord without spinal stenosis or distortion of the cord . mild righ neural foraminal narrowing from uncovertebral joint hypertropy mean