Worth Four Dot
Purpose: Worth four dot test assesses the client´s flat fusion ability at distance and near. The hand-held test in front of you is also used to detect a small unilateral central scotoma. The test is indicated when stereopsis is below 40 seconds of arc. It is also used in the differential diagnosis of unilateral decreased visual acuity. The traditional test is performed on a paper form. The client reports what colour the circle is. In the application, client simply taps on a coloured circle at the top of the screen and their dominant eye is displayed on the screen. Equipment and set-up: Put a red glass filter in front of the client´s right eye and the green filter in front of the left eye over the correction for the distance. The test is held at 40 cm. Show the client this test and ask them how many light spots they see. Interpreting the results:
- If the client recognises four dots, they have normal flat fusion
- If the client reports that they see two red dots, they are using only the right eye, therefore they are suppressing their left eye.
- If the client reports that they see three green dots, they are using only their left eye, therefore they are suppressing their right eye.
- If the client sees 5 dots, ask where the green ones are located. Based on the response, we can determine the relationship of the visual axes of the two eyes:
- If the red dots are to the right of the green ones, the client has an ESO deviation.
- If the red dots are to the left of the green dots, the client has an EXO deviation
- If the red dots are above the green dots, the client has a RIGHT HYPODEVIATION (or left hyperdeviation)
- If the red dots are below the green dots, the client has a right RIGHT HYPERDEVIATION (or left hypodeviation).
- 1 Interpretation of Worth Four Light test
- 2 There are a number of possible results demonstrated by a W4LT
- 3 Additional Resources
- 4 References
Interpretation of Worth Four Light testBefore the doctor starts to perform interpretation of worth four light test, it is very important not to forget to ask the patient, usually child a series of questions. These questions are essential and very important to every clinician:
- How many lights are you seeing?
- What color are they?
- Where are they located?
- Are all the lights in line? Or are some higher than the others?
- Do all the lights show up at one time, or are they flashing on and off?
There are a number of possible results demonstrated by a W4LTThe patient sees all four dots :
- Normal binocular response with no manifest deviation (NRC with no heterotropia)
- Harmonious ARC with manifest squint.
- uncrossed diplopia with esotropia, red dots appear to the right
- crossed diplopia with exotropia, red dots appear to the left of the green dots.
- American Academy of Ophthalmology. Pediatric Ophthalmology/Strabismus: Worth four dot test Practicing Ophthalmologists Learning System, 2017 – 2019 San Francisco: American Academy of Ophthalmology, 2017.
- Worth C. Squint: Its causes, pathology and treatment. Philadelphia: Blakiston, 1908
- Noorden GK von. Binocular vision and ocular motility: theory and managment of strabismus, 5th Ed. St Louis: Mosby, 1996.
- Duane’s Clinical Ophthalmology. New York: Lippincott Williams & Wilkins, 2005.