AT20 Specifications

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Letter Sizes

• LogMAR steps 6/3.0 - 6/120

Visual Acuity Selection

• Snellen Letters
• Illiterate "E"
• Landolt "C"
• AHOTX
• Numbers
• "LEA" Children's charts

Acuity Chart Display Options

• Multiple Line Decreasing
• Multiple Line Equal
• Single Letter
• Single Letter with interaction bars
• Single Column Decreasing
• Single Column Equal
• Single Line
• "Staircasing" measurement of visual acuity

Cross Cylinder Targets

• Dual rings
• Hexagonal pattern

Duochrome Screen

• Dual Rings
• UH Letters

Astigmatism measurement 

• Fan: 180°; 15° steps
• "V": 2.5° or 5° steps
• "L": located at "V" angle

Binocular Vision Tests

• Worth 4 dot
• Horizontal fixation disparity
• Vertical fixation disparity

Fixation Targets

• White dot
• Changing coloured dot
• Animated children's targets

Gratings Display

• Square wave gratings
• 1.5 cycles/degree to 60 cycles/degree
• 3 orientations

Other Facilities

• Various images and diagrams of the eye and ocular conditions
• Contrast sensitivity measurement using "staircasing" technique to determine contrast threshold
• Normal/reverse image for direct mirror viewing
• Random display option for acuity charts
• Scaling for actual viewing distance