What is perimetry

A computer records the spot of each flash and if you pressed the button when the light flashed in that spot.

At the end of the test, a printout shows if there are areas of your vision where you did not see the flashes of light. These are areas of vision loss. Loss of peripheral vision is often an early sign of glaucoma. A perimetry test can help find certain patterns of vision loss.

This may mean a certain type of eye disease is present. It is very useful in finding early changes in vision caused by nerve damage from glaucoma. Regular perimetry tests can be used to see if treatment for glaucoma is preventing further vision loss. The amount of peripheral vision loss is linked to the amount of optic nerve damage. A perimetry test makes a detailed record of your visual fields. In addition, these images may be moving or flickering.

The goal of visual testing is to quantitate of these functions. Traditionally we have tested visual function as visual acuity - the capacity to discriminate the fine details of objects and visual field - the portion of space in which objects are visible at the same moment during steady fixation of gaze in one direction. Color vision testing, flicker sensitivity, contrast sensitivity, pupillary responses and motion testing are some of the other methods of quantitating vision.

Perimetry is the systematic measurement of visual field function. The two most commonly used types of perimetry are Goldmann kinetic perimetry and threshold static automated perimetry. With Goldmann or "kinetic" perimetry, a trained perimetrist moves the stimulus; stimulus brightness is held constant. However, patients may find it inconvenient due to the prolonged test time and the plausible fatigue.

The lack of flexibility in the procedure, such as examining only certain variables is also a major disadvantage of Automated Perimetry. To successfully avoid these setbacks, Manual Perimetry using the Goldmann meter can be carried out. Since there is a trained professional subjects can be given breaks when experiencing fatigue. Subjects would also feel encouraged to respond to the stimuli in the presence of an examiner.

Certain aspects of the visual field can be specifically explored for more accurate mapping. On the other hand, this technique is less efficient, includes the possibility of human error and lacks the sensitivity of an electronic device. Furthermore, results are extremely subjective and may not be easily reproduced.

Finally, examiners may not be sufficiently qualified or trained. Automated perimetry has evolves exponentially over recent years due in part to modern computer technology that enables more complex visual stimuli and test procedures to be realised as opposed to the traditional methods of testing McKendrick, Advancements in Perimetry could characterize and monitor a range of optical diseases such as glaucomas, this could aid treatment and improve management of these diseases.

The development and validation of these new visual field procedures can be accomplished but must adhere to multicentre trials that yield clinical significance. Perimetry and visual field testing could be enhanced as diagnostic tools in clinical practice Johnson et al, WikiLectures WikiLectures.

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