Auto Refraction

BAT (Brightness Acuity Test)

• Also know as the "Glare Test"

• This test is required for all cataract evaluations and done to determine the degree a patient's cataract is affecting their vision with glare from lights (especially nighttime driving)

• It is done at the auto refractor here at HEA, but you can achieve the same result and do it in an exam room by simply shining a penlight into a patient's eye while they are reading the Snellen chart in a dark room 

• Essentially, what we are doing is shining a bright light into a patient's eyes and then seeing how well they can read a Snellen chart. When the light hits the dense areas of a cataract, it scatters the light all over, and consequently, decreases a patient's vision

• This is similar to driving though fog! If  you are driving in fog, forward visibility will become much worse if you use your regular headlights, or even worse, your high beams.  The light hits the water molecules and it then scatters everywhere and decreases visibility. This is the reason that fog lights are very low- intensity yellow lights that minimize the glare caused by regular high- powered headlights. 

Auto refraction gives us 3 key components for exams

1. It gives a baseline glasses Rx that we use as a starting point for a refraction and can fine- tune into a final glasses Rx

2. It gives Keratometry values that are needed for contact lens evaluations and determining surgical calculations

3. We can do BAT/Glare testing