Ophthalmology: Optic Testing

Ophthalmology: Optic Testing

1. Number

   • Rational Number
     • Precise measurements in units such as millimetres
     • In the fraction 20/20 - the numerator is the distance in feet between the subject and the eye chart. The denominator is the distance frm which a normal person can read the 8th line - 1 arc minute
   • Whole Number
   • Eye measurements are usually in millimetres (mm)

2. Geometry

   • Circles & Domes
     • Pupil
     • Iris
   • Sphere
     • Shape of an eyeball

3. Measurement

   • Angles
     • Angles of light reflection in the eye
     • 1 minute of arc (1 minute is 1/60 of a degree)
   • Diameter
     • Measuring the cross distance of certain circular shapes in the eye such as the iris
   • Radius
   • Circumference
     • Determining dilation/constriction of the pupil
   • They use trigonometry to determine the height of letters in an eye testing chart

4. Placing an eye chart on a wall involves specific mathematic measurements such as angle of where a letter is in relation to a person's eye and distance of chart from the viewer

5. The minimum average separation of two lines (depicted in a letter) that a person can see is an angle of 1 minute arc