disc (disk) disk.
disc.
disc
Patient discussion about optical disks.
embryonic disc , germinal disc a flat area in a blastocyst in which the first traces of the embryo are seen, visible early in the second week in human development.
disc (d sk)n. 1. Variant of disk. 2. A discus. |
disc.
See disk.
disc
see disk.
disc
1. A flat, circular, coin-shaped structure. 2. In anatomy, the intervertebral disc.
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).
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
1.22λ f/d
where d is the radius of the entrance pupil of the optical system of focal length f and λ the wavelength of the light used. In the eye, with a pupil of 4 mm diameter and λ = 507 nm, the diameter of Airy's disc is about 5 mm, which corresponds to a visual angle of about one minute of arc (Fig. D5). Syn. diffraction disc. See Rayleigh criterion; point-spread function; limit of resolution.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).
)
Fig. D5 Point spread function of the intensity of the diffraction pattern from a circular aperture. Airy's disc is represented by the central disc (AA), the radius of which is equal to 1.22 λf′/d, the radius of the next concentric light ring () is equal to 2.23 λf′/d. The light intensity is maximum in the middle of Airy's disc, it is equal to 1
)
Fig. D6 Images of a distant object formed on the retina of an unaccommodated emmetrope (clear, single image), a hyperope and a myope (blurred, double images) looking through a Scheiner's disc
)
Fig. D7 Stenopaeic slit
disc
Fibrocartilaginous material between spinal vertebrae which provides a cushion-like support against shock
Patient discussion about optical disks.
Q. I have a low back pain that radiates to my leg when i pick up stuff. Is it a disc herniation? I am a 43 years old bank teller. During the past 5 months I've suffered from a low back pain. The pain is not very strong, but it gets much worse while doing physical activity. When i walk or lift heavy things the pain is even stronger, and it radiates to my left leg. Can it be signs for disc herniation?
A. You can't tell for sure that your symptoms are due to a specific disc pathology.
When i had similar symptoms i went to the GP and he told me to lay down on your back. Then he slowly raised my left leg while the knee is kept in extension.
He said that If raising the leg over 60 degree exacerbates the pain its very likely to be disc herniation. But you should go to your GP and have him examine you.
When i had similar symptoms i went to the GP and he told me to lay down on your back. Then he slowly raised my left leg while the knee is kept in extension.
He said that If raising the leg over 60 degree exacerbates the pain its very likely to be disc herniation. But you should go to your GP and have him examine you.
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
A. I also have degenerative disc and osteoarthritis, it is different. I have fibromyalgia, so muscle pain along with the bone and joint pain. I have had two fusions in my c-spine. The osteophyte is a bone spur according to my doctor and he told me they usually start with the onset of arthritis. So good luck and if I can help in anyway with Questions please email me!
Q. I am interested in information on working with fibromyalgiaI am having problems just coping at home! I have had 2 c-spine surgeries in 2 years, have degenerative disc disease, maigrains with nuurological tendencies, fatigue, deppression and fibromyalgia. I can't stand for long , sit for long, just making it through my daily life is stressful enough how do people manage to work? I have been off since August of last year but wan to feel well enough so I can return to the working world, Any suggestions? Tried Lyrica, doctor took me off the side affects for me were terrible!
A. I had a cervical spinal fusion, C4-5,C5-6 and a SLAP repair of my left shoulder. Initially after the fusion the headaches and tinlging went away and then 4 months later, while in a PT work conditioning prorgam, the headaches returned, along with nausea, vomiting and vertigo. My doctor basically ignored the symptoms for the last 5 months and I was finally referred to a neurologist who is treating me with Lyrica and Imitrex. The side effects are brutal and it has come done to living with the headaches and other symptoms vs. living in a fog unable to function. I have come to realize that there is no magic "fix" and all the meds mask the stymptoms temporarily but it's a tradeoff when you consider the side effects and possible long term health issues from meds such as Lyrica that have no research as far as long term health conditions. I found a natural remedy called Headache Free and I'm giving it a try.....good luck because I know exactly how debilitative these symptoms are
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