Applanation Tonometry
Applanation tonometry measures intraocular pressure. The method is based on the physical definition of pressure: $$ P=\frac{F}{S} $$
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Applanation Tonometry
Contents 10.1 10.2 10.2.1 10.2.2 10.2.3 10.2.4 10.3
Applanation Tonometers for Use with the Slit Lamp...................................... 125 Technique for Measuring Ocular Pressure with Applanation ........................ Anesthesia and Fluorescein Solution ........... Preparation of the Slit Lamp and the Tonometer........................................ Patient Instructions ...................................... Checking the Satisfactory Operation of the Tonometer ..........................................
125 125 126 127
Goldmann and Schmidt Handheld Applanation Tonometer for Supine Patients ..................................... 131 Draeger Handheld Applanation Tonometer for Supine and Seated Patients ........................................................ 132
10.5
Perkins Handheld Applanation Tonometer ................................................... 133
10.6
Applanation Tonometer of Mackay and Marg .................................................... 134 Self-Tonometers ........................................... 136
10.7 10.7.1
Zeimer Self-Tonometer to Home Tonometry ................................................... 137 Description of the Home Tonometer............ 137
10.8 10.8.1
Draeger Self-Tonometer ............................ 139 Instruction for the Patients ........................... 139
10.9
Goldmann-Sampaolesi J-Setton Applanation Tonometer ............................. Intended Use ................................................ Indications for Use ....................................... Device Description....................................... System Components .................................... Miscellaneous ..............................................
10.9.1 10.9.2 10.9.3 10.9.4 10.9.5
References ................................................................. 146
Applanation tonometry measures intraocular pressure. The method is based on the physical definition of pressure: P=
130
10.4
10.6.1
10.10 Tonometer Control..................................... 145 10.10.1 Disinfection for Applanation Tonometer ..... 146
141 141 141 142 142 142
F S
If part of a flexible sphere such as the eye (cornea) is flattened with a flat surface (that of the tonometer), an equilibrium can be achieved in which the force applied is equal to that of the pressure of the sphere on the surface (Fig. 10.1), that is, P · S = F. But the cornea has an elastic force that opposes the applanation (N), and the meniscus of the lacrimal fluid between the applanation surface and the cornea adheres the applanation surface to the cornea. This force must be added to the former in the direction in which it is exerted (M): P .S+ N = F+ M F+M-N P= S Goldmann established that when a human cornea is flattened with an applanation surface with a 3.06 mm diameter and when the
R. Sampaolesi et al., The Glaucomas, DOI 10.1007/978-3-642-35500-4_10, © Springer-Verlag Berlin Heidelberg 2014
123
10
124 Fig. 10.1 Applanation tonometry. F, the force given to the applanation cone = P, o
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