WordNet

optical properties; "the optics of a telescope"
the branch of physics that studies the physical properties of light

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/05/20 17:15:51」(JST)

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The optic disc or optic nerve head is the point of exit for ganglion cell axons leaving the eye. Because there are no rods or cones overlying the optic disc, it corresponds to a small physiological blind spot in each eye.

The ganglion cell axons form the optic nerve after they leave the eye. The optic disc represents the beginning of the optic nerve and is the point where the axons of retinal ganglion cells come together. The optic disc is also the entry point for the major blood vessels that supply the retina.^[1] The optic disc in a normal human eye carries from 1 to 1.2 million neurons from the eye towards the brain.

Anatomy

The optic disc is placed 3 to 4 mm to the nasal side of the fovea. It is a vertical oval, with average dimensions of 1.76mm horizontally by 1.92mm vertically.^[2] There is a central depression, of variable size, called the optic cup.

Clinical examination

The eye is unique because of the transparency of its optical media. Almost all eye structures can be examined with appropriate optical equipment and lenses. Using a modern direct ophthalmoscope gives a view of the optic disc using the principle of reversibility of light. A slit lamp biomicroscopic examination along with an appropriate aspheric focusing lens (+66D, +78D or +90D) is required for a detailed stereoscopic view of the optic disc and structures inside the eye.

A biomicroscopic exam can give an indication of the health of the optic nerve. In particular, the eye care physician notes the colour, cupping size (as a cup-to-disc ratio), sharpness of edge, swelling, hemorrhages, notching in the optic disc and any other unusual anomalies. It is useful for finding evidence corroborating the diagnosis of glaucoma and other optic neuropathies, optic neuritis, anterior ischemic optic neuropathy or papilledema (i.e. optic disc swelling produced by raised intracranial pressure), and optic disc drusen.

Women in advanced stage of pregnancy with pre-eclampsia should be screened by an ophthalmoscopic examination of the optic disc for early evidence of rise in intracranial pressure.

Schematic diagram of the human eye, with the optical disc, or blind spot, at the bottom.

Pale disc

A normal optic disc is orange to pink in colour. A pale disc is an optic disc which varies in colour from a pale pink or orange colour to white. A pale disc is an indication of a disease condition.

Imaging of the optic disc

Traditional colour-film camera images are the reference standard in imaging, requiring an expert ophthalmic photographer, ophthalmic technician, optometrist or an ophthalmologist for taking standardised pictures of the optic disc. Stereoscopic images offer an excellent investigative tool for serial follow-up of suspected changes in the hands of an expert optometrist or ophthalmologist.

Automated techniques have also been developed to allow for more efficient and less expensive imaging. Heidelberg Retinal Tomography (HRT-II), GDx-VCC and optical coherence tomography (Stratus-OCT 3) are the currently available computerised techniques for imaging various structures of the eyes, including the optic disc. They quantify the nerve fiber layer of disc and surrounding retina and statistically correlate the findings with a database of previously screened population of normals. They are useful for baseline and serial follow-up to monitor minute changes in optic disc morphology. Imaging will not provide conclusive evidence for clinical diagnosis however, and the evidence needs to be supplanted by serial physiological testing for functional changes. Such tests may include visual field charting and final clinical interpretation of the complete eye examination by an eye care physician. Ophthalmologists and optometrists are able to provide this service.

Retinography photograph showing the optic disc as a bright area on the right where blood vessels converge.

References

^ blind spot. (2011). In Encyclopædia Britannica. Retrieved from http://www.britannica.com/EBchecked/topic/69390/blind-spot
^ Duane's Ophthalmology (2006). Ch. 4 Anatomy of the Visual Sensory System

External links

Diagram at Moorfields Eye Hospital
Diagram at Ballard Optical

UpToDate Contents

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1. 乳頭浮腫の概要および鑑別診断 overview and differential diagnosis of papilledema
2. 視神経症 optic neuropathies
3. 視神経の先天性および後天性異常 congenital anomalies and acquired abnormalities of the optic nerve
4. 非動脈炎性前部虚血性視神経症：臨床的特徴および診断 nonarteritic anterior ischemic optic neuropathy clinical features and diagnosis
5. 非動脈炎性虚血性視神経症：予後および治療 nonarteritic ischemic optic neuropathy prognosis and treatment

English Journal

A comprehensive review of diagnostic imaging technologies to evaluate the retina and the optic disk.

Bajwa A1, Aman R, Reddy AK.
International ophthalmology.Int Ophthalmol.2015 Oct;35(5):733-55. doi: 10.1007/s10792-015-0087-1. Epub 2015 Jun 5.
Ophthalmic imaging has undergone a revolution over the past 20 years with increasingly efficient and high-definition modalities now available. The use of wide-field retinal angiography, fundus autofluorescence, state-of-the-art spectral domain, and enhanced depth imaging optical coherence tomography
PMID 26043677

Correlation between the ganglion cell complex and structural measures of the optic disc and retinal nerve fiber layer in glaucoma.

Bresciani-Battilana E1, Teixeira IC, Barbosa DT, Caixeta-Umbelino C, Paolera MD, Kasahara N.
International ophthalmology.Int Ophthalmol.2015 Oct;35(5):645-50. doi: 10.1007/s10792-014-9988-7. Epub 2014 Sep 3.
To correlate the ganglion cell complex (GCC) parameters with structural measures of the optic nerve head (ONH) and retinal nerve fiber layer (RNFL) as evaluated by Fourier-Domain optic coherence tomography (OCT). This retrospective study included patients with glaucoma, ocular hypertensive patients
PMID 25183459

Multimodal imaging of peripheral myelinated retinal nerve fiber layers without optic disk involvement.

Corvi F1, Querques G2.
Journal francais d'ophtalmologie.J Fr Ophtalmol.2015 Sep 2. pii: S0181-5512(15)00239-9. doi: 10.1016/j.jfo.2015.01.016. [Epub ahead of print]
PMID 26342655

Japanese Journal

視神経乳頭腫脹を契機として発見された肺腺癌の1例 (特集第68回日本臨床眼科学会講演集(7))

臨床眼科 69(9), 1395-1399, 2015-09
NAID 40020566624

日本人健常者における視神経乳頭サイズと乳頭回転角の検討 (第25回日本緑内障学会)

あたらしい眼科 32(8), 1183-1186, 2015-08
NAID 40020571078

鼻側視神経乳頭低形成(Nasal optic disc hypoplasia)の1例

山形県立病院医学雑誌 49(2), 108-110, 2015-07
NAID 40020681241

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「視神経円板」

Optic disc
	Interior of posterior half of bulb of left eye. The veins are darker in appearance than the arteries.
	The terminal portion of the optic nerve and its entrance into the eyeball, in horizontal section.
Details
Latin	Discus nervi optici
Identifiers
Gray's	p.1015
MeSH	A08.800.800.120.680.660
TA	A15.2.04.019
FMA	58634
	Anatomical terminology