Glaucoma

Here is a small tip!

The tonometer is a machine used in the measurement of intraocular pressure (IOP). It determines the resistance of the eyeball to indentation by an applied force. The air-puff tonometer is one of several types of tonometers and can commonly be found in many eye doctors’ offices. It does not touch the eye but ejects a small puff of pressurized air in order to detect any abnormal levels of IOP.

IOP reflects the balance between the production and elimination of aqueous humor in the eye. In the general population, the normal range for IOP is 10-20 mmHg.

Your eye doctor may want to examine the interior of your eye, specifically, your optic nerve. An instrument called an ophthalmoscope studies the back of your eye (the fundus) through the pupil, enabling the eye doctor to assess for the presence of damage, such as cupping, around the optic nerve. In the normal eye, the optic cups are symmetric, and the rim of the optic nerve is pink. With glaucoma, either a generalized enlargement with or without notching of the optic cup can be seen. The rim remains pink until late stages of the disease but is thinner.

Your eye doctor may want to check for the presence of any loss of visual field, which is often an indication of a damaged optic nerve. In addition, glaucoma often produces characteristic changes in your visual field, such as a generalized shrinking of your range of vision. A two-dimensional tool with intersecting vertical and horizontal lines is commonly used to discover such a visual field defect. A kinetic visual field test, for example, consists of an object that moves around the grid. The patient is asked to specify where he/she can see the object, and where he/she cannot, thus enabling the doctor to establish the boundaries of the patient’s field of vision.