In glare testing, how many controlled degrees of light does the bat test deliver when viewing a Snellen target?

In glare testing, the bat test is employed to assess the effects of light glare on visual acuity when viewing a Snellen target. This specific test is designed to measure how different levels of glare can impact a person's ability to perceive and differentiate visual information.

The correct answer indicates that the bat test delivers three controlled degrees of light during this assessment. This number is significant because it allows for a comprehensive evaluation of how increasing levels of glare can affect visual performance. Each degree of light represents a different level of intensity or brightness that the subject must navigate during the test, thereby providing a structured way to quantify the effects of glare on vision.

The presence of three degrees of controlled light allows examiners to determine the threshold at which glare begins to significantly interfere with vision, which can be critical in various fields, including appraisals where accurate visual assessment can be impacted by environmental lighting conditions.