The horizontal vergence (BI and BO vergence) used by patients to maintain binocular vision is measured through the use of prisms. Gradually increasing the prism causes the horizontal retina to shift, forcing the patient to use the vergence system to compensate for this shift.
To measure BI and BO clutching and dissipating capabilities, three aspects of data need to be obtained:
(1) Fuzzy point: Indicates that the patient can no longer use the vergence to compensate for the retinal shift caused by the prism, but can still maintain stable accommodation.
(2) Rupture point: Indicates that the patient has exhausted all vergence potential and can no longer maintain binocular single vision.
(3) Recovery point: Indicates that the induced retinal removal gradually decreases, allowing the ability to reapply vergence to obtain binocular single vision
(2) Instruct the patient to watch the visual mark and try to keep it clear, and ask the patient to report when the following situations occur:
① The visual mark is blurred (fuzzy point);
② The visual target becomes two (break point);
③ Optotype moves to the left or right, which means that one eye is suppressed.
Once this phenomenon occurs, the inspection should be stopped, recorded (suppressed) and pointed out which eye. Which eye is inhibited can be determined by asking in which direction the optotype is moving. The optotype will move in the direction of the top of the prism in front of the non-suppressed eye.
Post time: Feb-18-2023