Glaucoma

Published on 10/03/2015 by admin

Filed under Opthalmology

Last modified 10/03/2015

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9 Glaucoma

Anatomy/physiology

Ciliary body (CB)

6-mm-wide structure located between the scleral spur anteriorly and the ora serrata posteriorly; composed of the pars plicata (anterior 2 mm with ciliary processes) and the pars plana (posterior 4 mm, flat)

Pars plicata consists of

Functions

Angle Structures

Visible only by gonioscopy because of total internal reflection at the air/cornea interface (Figure 9-1)

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Figure 9-1 Composite drawing of the microscopic and gonioscopic anatomy.

(From Becker B, Shaffer RN: Diagnosis and Therapy of the Glaucomas, St Louis, Mosby, 1965.)

Angle Abnormalities

Testing

Tonometry

IOP measurement can be performed with a variety of devices (tonometers)

Gonioscopy

Visual Fields

Perimetry measures the ‘island of vision’ or topographic representation of differential light sensitivity. Peak = fovea; depression = blind spot; extent = 60° nasally, 60° superiorly, 70–75° inferiorly, and 100–110° temporally

Central field tests points only within a 30° radius of fixation

Humphrey (static)

Optic Nerve Head (ONH) Analyzers

Various digital and video cameras that capture ONH image; computer then calculates cup area in an attempt to objectively quantify ONH appearance (Table 9-1)

Confocal scanning laser ophthalmoscopy (CSLO; Heidelberg retinal tomograph [HRT]; TopSS)

low-power laser produces digital 3D picture of ON head by integrating coronal scans of increasing tissue depth; indirectly measures nerve fiber layer (NFL) thickness (Figures 9-6, 9-7)

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Figure 9-6 Confocal scanning laser ophthalmoscopy.

(Adapted from Schuman JS, Noeker RJ: Imaging of the optic nerve head and nerve fiber layer in glaucoma. Ophthalmol Clin North Am 8:259–279, 1995.)

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Figure 9-7 Confocal scanning laser ophthalmoscopy printed report.

(From Zangwill L, de Souza K, Weinrob RN: Confocal scanning laser ophthalmoscopy to detect glaucomatous optic neuropathy. In Shuman JS [ed]: Imaging in Glaucoma. Thorofare, NJ, Slack, 1997.)

Optic nerve blood flow measurement

color Doppler imaging and laser Doppler flowmetry (Figure 9-10)

image

Figure 9-10 Color Doppler imaging of the ophthalmic artery.

(From O’Brien C, Harris A: Optic nerve blood flow measurement. In Yanoff M, Duker JS [eds]: Ophthalmology, London, Mosby, 1999.)