Glaucoma and Cataract
Is the loss of visual function due to cataract or to glaucoma?
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Contents 48.1 48.1.1
General........................................................ 917 Principle of Operation.................................. 918
48.2
Associations of Cataract and Glaucoma .... 921
References ................................................................. 924
48.1
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General
Is the loss of visual function due to cataract or to glaucoma? The progressive lens changes in cataract can mimic progressive visual field loss. When both conditions are associated, it is necessary to analyze the loss of central vision (visual acuity and contrast vision) and the loss of differential light sensitivity (computed visual field). It has to be determined how much is due to glaucoma and how much is due to the cataract. By analyzing both conditions and above all the ocular tension, it will be possible to say (1) whether the glaucoma is what is essential and has to be operated before the cataract, (2) if it is indicated to operate the cataract and the glaucoma in the same surgery with a combined operation, or (3) whether only the cataract must be operated because the pressure in the glaucoma is regulated with medication. These are the three basic decisions that must be taken when faced with the coexistence of both conditions. The first problem presented is to know to what extent the alteration of the visual field is due to the glaucoma and how much is due to the cataract. To solve this, a computed perimetry is performed with the G1 program, which includes visual indexes and is analyzed with the Octosmart program Electronic supplementary material The online version of this chapter (doi:10.1007/978-3642-35500-4_48) contains supplementary material, which is available to authorized users.
R. Sampaolesi et al., The Glaucomas, DOI 10.1007/978-3-642-35500-4_48, © Springer-Verlag Berlin Heidelberg 2014
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Fig. 48.2 Opacity Lensmeter 701, principle of operation Fig. 48.1 Opacity Lensmeter 701
48.1.1 Principle of Operation (Bebie curve), and a measure of the density of the cataract with the Opacity Lensmeter 701. The Opacity Lensmeter 701 was designed by Flammer and Bebie in 1987 [1, 2] and manufactured by Interzeag, to measure the density of the lens. This instrument emits a modulated dark-red beam, 1.5 mm in diameter with a wavelength of 700 nm. The subject looks at a green fixation target in the instrument, enabling the examiner to position the red beam in the center of the lens in order to make a measurement of any opacity which is located along the optic axis only (Fig. 48.1). Depending on the density of the opacity of the lens, a smaller or larger part of the light is scattered back toward the lensmeter. This scattered light is received by a sensor which converts the light signal into an electrical impulse (Fig. 48.2). The examination takes just a few minutes; five consecutive measurements are taken for each eye and the results are displayed digitally. There is also a printout facility. The printed paper strip gives the value of each measurement, th
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