Testing distance is one of the parameters that make RAM the best potential vision tester. Testing too near errors on overestimation while testing too far errors on underestimation of retinal acuity.
The RAM Prime has the option of a Lanyard momentary switch, which connects, to a lanyard.  When the lanyard is taunt, the switch turns on and the chart-viewing window illuminates.  The lanyard is easily adjustable to match the measuring cord length and this length is maintained throughout the exam.  If the patient holds the RAM too closely, the window is not illuminated.  The length of the adjusted Lanyard prevents holding the RAM too far away.  Includes installation of Lanyard Switch and one Adjustable Lanyard.  Lanyard switch sold separately for $125.00 at time of RAM Prime XL purchase.