The red glass test is an eye examination used to detect and analyze diplopia, commonly known as double vision. This test helps identify the presence, type, and characteristics of diplopia.
How the Red Glass Test Works
The red glass test employs a simple yet effective technique. Here’s a breakdown of the process:
- Red Filter: A red filter, typically a red lens, is placed in front of one eye of the patient.
- Light Source: The patient then looks at a light source or target.
- Observation: The patient reports the number of light sources they see and their position relative to each other.
What the Red Glass Test Detects
The red glass test is primarily designed to assess various aspects of binocular vision problems:
1. Diplopia Detection and Type
The test can:
- Detect the presence of diplopia: If the patient reports seeing two images instead of one, it confirms double vision.
- Identify the type of diplopia: The red glass helps distinguish between:
- Crossed Diplopia: The image seen by the right eye appears on the left, and vice-versa.
- Uncrossed Diplopia: The image seen by the right eye appears on the right and vice-versa.
2. Suppression
- The test can help identify suppression. If the patient only reports seeing one image even with the red filter on, it suggests that one eye is suppressing visual information.
3. Retinal Correspondence
- The test can also be used to determine the retinal correspondence between the two eyes. It is a measure of how the visual fields of the two eyes align.
4. Confirming Diplopia Characteristics
- It helps confirm the type of diplopia (crossed or uncrossed) by making one image distinctly red allowing the examiner to correlate with its position in relation to the other uncolored image.
Key Characteristics of the Test
- Moderately Disassociating: This test is considered moderately disassociating because it separates the visual input of the two eyes, making it easier to evaluate individual eye contributions.
- Simple to Perform: The test is easy to conduct, requires basic equipment, and can provide significant diagnostic information.
- Versatile: The test can be used with a variety of light sources and targets.
Summary
The red glass test is an effective method for assessing diplopia and related binocular vision issues. It helps ophthalmologists and optometrists diagnose and treat conditions related to double vision. The test helps differentiate the underlying mechanisms of the diplopia, the type of diplopia and the presence of suppression in each eye.
