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The hole represents the cup and the surrounding area the disc. If the cup fills 1/10 of the disc, the ratio will be 0.1. If it fills 7/10 of the disc, the ratio is 0.7. The normal cup-to-disc ratio is less than 0.5. A large cup-to-disc ratio may imply glaucoma or other pathology. [3] However, cupping by itself is not indicative of glaucoma.
The interpretation of fundus photographs that are glaucomatous must contain a description of the vertical and horizontal cup to disc ratio, vessel pattern, diffuse or focal pallor, asymmetry and development of the above factors. The retinal nerve fibre layer should also be studied and commented on. [23]
In megalopapilla the optic disc diameter exceeds 2.1 mm (or surface area more than 2.5 mm 2 [1]) with an increased cup-to-disc ratio. [2] Although the optic disc is looks abnormal, the disc colour, sharpness of disc margin, rim volume, configuration of blood vessels and intraocular pressure will be normal. [3] [1] Visual field is normal except ...
The optic disc is located 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.
Changes on ophthalmologic exam include deepening and enlargement of the optic cup (leading to a high cup/disc ratio), a more vertical oval optic cup shape, pallor of the disc, and an increase in the blood vessels within the optic nerve on the nasal side of the disc.
Common aspect ratios used in film and display images. The common film aspect ratios used in cinemas are 1.85:1 and 2.40:1. [1] Two common videographic aspect ratios are 4:3 (1. 3:1), [a] the universal video format of the 20th century, and 16:9 (1. 7:1), universal for high-definition television and European digital television.
Outside the United States, the standard chart distance is 6 metres (20 ft), and normal acuity is designated "6/6". Other acuities are expressed as ratios with a numerator of 6. Some clinics do not have 6-metre eye lanes available, and either a half-size chart subtending the same angles at 3 metres (9.8 ft), or a reversed chart projected and ...
The ratio between worm and table is generally 40:1, 72:1 or 90:1 but may be any ratio that can be easily divided exactly into 360°. This is for ease of use when indexing plates are available. A graduated dial and, often, a vernier scale enable the operator to position the table, and thus the work affixed to it with great accuracy.