vertex

vertex /ver·tex/ (ver´teks) pl. ver´tices   [L.] the summit or top, especially the top of the head (v. cra´nii) .ver´tical

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ver·tex (vûrtks)

n. pl. ver·tex·es or ver·ti·ces (-t-sz)

1. The highest point; the apex.

2. The topmost point of the vault of the skull; the crown of the head.

3. The portion of the fetal head bounded by the planes of the trachelobregmatic and biparietal diameters, with the posterior fontanel at the apex.

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vertex

[vur′teks]

Etymology: L, summit

1 the top of the head; crown.

2 the apex or highest point of any structure.

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vertex

the summit or top, especially the top of the head.

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vertex corneae

central part of the cornea.

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vertex

The point where the optical axis intersects a reflecting or refracting surface. In a spectacle lens the back vertex is the point of intersection of the optical axis with the surface nearest to the eye, the other being the front vertex. Plural: vertices.
vertex depth Distance between the posterior pole of a spectacle lens and the plane containing the posterior edge of the lens. The vertex depth s is given by the following formula

s = r − Î(r² − y²)

where r is the radius of curvature of the surface of the spectacle lens and y is the semi-diameter at the edge of the surface (Fig. V3). Syn. sag. See apical clearance; lens measure.
vertex distance Distance along the line of sight between the apex of the cornea and the posterior surface of a spectacle lens. This distance normally varies between 11 mm and 15 mm. See apical clearance; spectacle plane.
vertex focal length The linear distance separating the principal focal point (focus) of an optical system or lens from the front or back vertices. They are called the front vertex focal length (f_v) and the back vertex focal length (f′_v), respectively. In the case of a biconcave or biconvex lens the front and back vertex focal lengths are equal. In the case of a positive meniscus lens, the back vertex focal length is shorter than the front vertex focal length and vice versa in the case of a negative meniscus lens. See back vertex power; front vertex power.
vertex power See back vertex power; front vertex power.

Fig. V3 Vertex depth (or sagittal depth) s of a spherical surface (r, radius of curvature; 2y, diameter of the surface)

Table V1 Vertex depths of various spherical surfaces. They also represent the centre thickness of a planoconvex lens with a front surface of radius of curvature r and diameter 2y, with an edge thickness of zero. Index of refraction of the lens 1.49
				lens diameter 2y (mm)
surface power (D)		radius r (mm)		40		50		60		70
1		490		0.41		0.64		0.92		1.25
2		245		0.82		1.28		1.84		2.51
3		163.3		1.23		1.92		2.78		3.79
4		122.5		1.64		2.58		3.73		5.11
5		98		2.06		3.24		4.70		6.46
6		81.7		2.49		3.92		5.71		7.88
7		70		2.92		4.62		6.75		9.38
8		61.3		3.38		5.33		7.85		10.99
9		54.4		3.81		6.08		9.01		12.74
10		49		4.27		6.86		10.26		14.71
12		40.8		5.23		8.55		13.13		19.80
14		35		6.28		10.51		16.97		35.00
16		30.6		7.43		12.94		24.47
18		27.2		8.75		16.45
20		24.5		10.35

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Patient discussion about vertex.

Q. What could make the top of your head hurt to the touch. I don't have a headache. It just hurts when I touch It only hurts on the left side.

A. if it's a deep pain- it might be caused by a trauma to the bode. have you been hurt by something..? if you don't remember - it might be a memory loss from the hit to the head :)
if it's a sort of superficial pain- it might be caused of a wound there. ask someone to have a look and see if there's anything over there. it could even be a tic sitting there...