Ask about the positioning of the dots, for example are the red dots to the left or the right of the green dots. If they see five lights, ask whether the green dots are higher or lower than the red dots. You must ask about the colour of the lights. They should respond with "I see … number of lights" provided they have understood what you have asked them.Īsk them to describe the lights to you. The Worth Four Light Test in dimmed lighting conditions First you must place the red/green goggles over the patients eyes, with the red goggle traditionally placed over the right eye. The Worth Four Light Test is relatively simple to undertake. Also in individuals who have abnormal retinal correspondence (ARC) they may provide an unexpected response, and those who have misaligned visual axis whom in natural conditions suppress may actually provide a diplopic response upon testing. Whilst there are no contraindications of the W4LT there needs to be caution in interpreting the results of individuals with BSV in natural conditions as they may show a diplopic response under the dissociation of the test. Other indications for the test include establishing an individual's dominant eye dominant eye compared to the other and when evaluating reduced monocular visual acuity which shows no improve on pinhole testing. Though it can be used in these patients to prove the presence of peripheral fusion and that they have bi-foveal fixation. Therefore, is indicated in cases of a suspected central suppression scotoma as it can be used to detect where the lights may not be appreciated from the eye with the scotoma though in some cases of minimal deviation in the eye as demonstrated in a microtropic deviation a normal response of 4 lights may be reported.
In cases of manifest strabismus the test can help in determining the nature and type of the diplopia or which eye is suppressing. If the images are unable to be fused the W4LT is still indicated to help to determine if an individual appreciates diplopia (double vision) or are suppressing an image from one eye. The W4LT can also be indicated when aiding a person to develop and strengthen their fusional capacities. The test is indicated with the use of a presence of a prism in individuals with a strabismus and fusion is considered present if 4 lights are maintained, with or without the use of a prism. It can be used to establish whether a patient has the ability for the eyes to fuse the light that is received from each eye into 4 lights. It can be used when wanting to assess whether the individual has a normal or abnormal binocular single vision response (BSV). It can be used to develop a diagnosis or to support or confirm an initial diagnosis. The Worth Four Light Test is indicated for use when assessing the binocular functions, the ability of eyes to work in coordination, of an individual. The Worth Four Light Test at a distance of 6 meters If the patient does not fuse the images of the two eyes, they will see five lights ( diplopia).
If the patient either closes or suppresses an eye they will see either two or three lights. With both eyes open, a patient with normal binocular vision will appreciate four lights. When performing the test at near (at 33 cm ) the lights are arranged in exactly the same manner (diamond formation), with the difference being that at near, the lights are located in a hand-held instrument which is similar to a light torch.īecause the red filter blocks the green light and the green filter blocks the red light, it is possible to determine if the patient is using both eyes simultaneously and in a coordinated manner. The lights are arranged in a diamond formation, with a red light at the top, two green lights at either side (left and right) and a white light at the bottom. At both testing distances the patient is required to wear red-green goggles (with one red lens over one eye, usually the right, and one green lens over the left) When performing the test at far (distance) the W4LT instrument is composed of a silver box (mounted on the wall in front of the patient), which has four lights inside it. The W4LT can be performed by the examiner at two distances, at near (at 33 cm from the patient) and at far (at 6 m from the patient). This is a common adaptation to strabismus, amblyopia and aniseikonia. Suppression occurs during binocular vision when the brain does not process the information received from either of the eyes. The Worth Four Light Test is also used in detection of suppression of either the right or left eye. 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, 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.
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