Examination Methods

These include:

❖ Ophthalmoscopy (see Chapter 1).

❖ Visual acuity testing (see Chapter 1).

❖ Pupillary light reflex (see Chapter 9).

❖ Testing color vision (for example with the panel D 15 test).

❖ Visual evoked potential (VEP).

Panel D15 test of color vision: This is a color marker sorting test. The patient is presented with 15 small color markers that he or she must select and sort according to a fixed blue color marker. Patients with color vision defects will typically confuse certain markers within the color series. The specific color vision defect can be diagnosed from these mistakes.

13.3 DisordersthatObscuretheMarginoftheOpticDisk 363

Visual Evoked Potential (VEP): The VEP may be regarded as an isolated occipital EEG. The electrical responses in the brain to optical stimuli are transmitted by electrodes placed over the occipital lobe. Measurements include the speed of conduction (i.e., latency; normal values range between 90 and 110 ms) and the voltage differential between the occipital lobe and skin electrodes (i.e., amplitude; normal values depend on the laboratory setting). The most important indication for VEP testing is retrobulbar optic neuritis to demonstrate an extended latency period in demyelinization, such as in diffuse encephalitis.

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