page_title: Worth 4 dot test
section_title: Method of assessment
hierarchical_section_title: Worth 4 dot test / Method of assessment
caption_attribution_description: English: Red green goggles used in the Worth's Four Light Test
context_page_description: The Worth Four Light Test, also known as the Worth's Four Dot test or W4LT, is a clinical test mainly used for assessing a patient's degree of binocular vision and binocular single vision. Binocular vision involves an image being projected by each eye simultaneously into an area in space and being fused into a single image. The Worth Four Light Test is also used in detection of suppression of either the right or left eye. Suppression occurs during binocular vision when the brain does not process the information received from either of the eyes. This is a common adaptation to strabismus, amblyopia and aniseikonia.
  The W4LT can be performed by the examiner at two distances, at near and at far. At both testing distances the patient is required to wear red-green goggles When performing the test at far the W4LT instrument is composed of a silver box, which has 4 lights inside it. The 4 lights are arranged in a diamond formation, with a red light at the top, two green lights at either side and a white light at the bottom.
context_section_description: The Worth Four Light Test is relatively simple to undertake. First you must place the red/green goggles over the patients eyes, with the red goggle traditionally placed over the right eye.
  Next you must dim the room lighting. This allows the patient to see the lights better.
  For a distance measurement, you should have the patient set up six metres away from the light source. For a near measurement, the test should be performed at approximately one third of a metre, or thirty three centimetres, with a handheld Worth’s Four Lights torch.
  Then, ask the patient what they see. They should respond with “I see … number of lights” provided they have understood what you have asked them.
  Ask them to describe the lights to you. You must ask about the colour of the lights. If they see five lights, ask whether the green dots are higher or lower than the red dots. Ask about the positioning of the dots, for example are the red dots to the left or the right of the green dots. Also ask if the dots are flashing on and off or switching between red and green.
  This series of questions is essential in order to ensure you correctly record exactly what the patient is seeing, so that the clinician can interpret the patient’s results and then make an accurate diagnosis.
caption: Red Green Goggles used in the Worth Four Light Test
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