Home Products.htm      Purchase  

 

 

 

 

 

 

 

ETDRS RAM, 2 lighting levels

◘  Standard acuity testing

◘  Retinal Acuity testing

 

l

 

Text Box: ETDRS Equivalent Chart    A. 20/16 TO 20/200: 12 lines of letters are presented from -0.1 logMAR (20/16) to 1.0 logMAR (20/200) letter size in 0.1 logMAR increments.  Each line has 5 letters with one letter-width separating the letters and each line has the same readability index as described by F. L. Ferris III, et al.: New Vision Acuity Charts for Clinical Research. AJO 94,1, 1982. Comes with Attenuation Filter, rechargeable batteries, charger, Panoramic Pinhole Lens Clip, Pinhole Lens Clip, and Lanyard. B. 20/16 TO 20/800: Available in Classic Chart 1 and Chart 2. Each line has 5 letters with one letter-width separating the letters and each line has the same readability index as described by F. L. Ferris III, et al.: New Vision Acuity Charts for Clinical Research. AJO 94,1, 1982. Chart 1 or Chart 2 can be purchased separately or as a pair. Comes with Attenuation Filter, rechargeable batteries, charger, Low Vision Attachment, Panoramic Pinhole Lens Clip, Pinhole Lens Clip, and Lanyard.        Both Standard Acuity (current corrected visual acuity) and Retinal Acuity (retinal function) can be measured with this instrument.  For Standard Acuity, the window brightness is reduced to standard luminance with the attenuation filter and is viewed through a near add.  For Retinal Acuity, the window is viewed at full brightness through a near add and a pinhole.        The scale is in logMAR as per the EDTRS chart.  Snellen conversion is listed in parenthesis on the back label.  Twelve letter sizes are achieved from 9 lines of letters by utilizing 3 lines of letters for testing at 2 distances, 8 and 16 inches.  By halving the distance the visual angle is doubled.  For focusing, an add of +2.5 diopters is used at the16 inches and an add of +5 diopters is used at the 8 inches testing distance.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Hit Counter