A third arrow located to the right and below the horizontal white scale is used to measure torsion The Maddox Wing measures the size of heterophorias (latent deviations) and small heterotropias (manifest deviations) at near when normal retinal correspondence (NRC) is present.
It is a quick and convenient method of measuring the size of a deviation and is generally used in association with a number of other tests before a full diagnosis is determined.
The Scale Card: Used to measure the deviation of heterophorias, small heterotropias (with NRC) and also torsion.
The Maddox Wing test is performed at near with the instrument held in reading position, slightly inferior (approximately 15° depression and 33 cm away).
The room or location of the test should be brightly illuminated and the patient's optical correction (e.g. glasses, bifocals, multifocals, contact lens) is required to be worn.