Vision Therapy Treatment Devices and Methods
The Brock String is a simple tool which gives the patient a great deal of visual feedback. It teaches the patient how to aim his eyes together correctly for varying distances in space and allows him to experience the difference between convergent and divergent eye aims. It also allows the patient to determine if he is shutting off an eye, or suppressing, and tells him where his eyes are aimed and how far off his eye aim may be. This is usually one of the first techniques a patient is taught and is often assigned as home vision therapy.
Computers are an important part of vision therapy. Orthoptic vision therapy software can create a wide range of visual stimuli and affords the variability to individualize techniques to meet each patient’s specific needs. The patient can work on programs which train eye movements, eye coordination, stereo vision, and anti suppression techniques. Therapy always begins at a level where the patient can succeed and gradually increases the visual demands to stretch his range and skill.
The cheiroscope is a diagnostic and training machine used to assess binocular stability and alignment and to detect the presence and extent of suppression. Suppression occurs when the patient’s brain shuts off an eye by blocking its visual input when the patient loses the ability to control his eye aim or alignment. Suppression is an adaptive neurological response to protect oneself from double vision. Training on the cheiroscope gives the patient important feedback that he is suppressing and allows him an opportunity to gain the binocular control necessary to correct his eye aim and eliminate suppression.
An aperture rule is a fusional technique. The patient is asked to look through a window in a slide at a series of targets placed at the end of the instrument. Each eye sees a different part of the target, and the patient learns to fuse the two images coming in from his left and right eyes into a single picture. The eye therapist’s role is to coach the patient on ways to adjust his visual system to achieve the goal of clear, single vision.
The amblyoscope is a machine which trains a patient to use his/her eyes together. The goal of the instrument is to help the patient achieve binocular fusion, or normal two-eyed single vision with depth perception. As the patient progresses in skill, the doctor or vision therapist increases the fusional demands to stretch and normalize the patient’s ability to efficiently use his/her two eyes together. This machine also allows a patient to know when he/she is suppressing an eye. Visual awareness is the first step in successful training.
Patients with unstable visual systems often learn a neurological adaptation called suppression, in which their brains block the visual input coming in from one eye. People unconsciously learn to suppress at very young ages to keep from seeing double. Suppression is never normal and is always a sign of an unstable visual system.
Vision therapy trains the eyes to work together but to do so both eyes have to be “on.” Therapists work with patients using special red-green lenses and a target with red-green letters. One eye can only see the red letters, and the other the green. If the visual system shuts off an eye, the patient won’t be able to see all of the letters. Anti suppression activities such as these make the patient aware of when she is suppressing and allow her to gain control and learn to leave both eyes on simultaneously. This is especially important for patients with wandering eyes, crossed eyes, and lazy eyes.
Lenses and Prisms
Lenses and prisms are always important in visual training. They modify the patient’s world and allow him to the opportunity to create an appropriate visual response.
With the focusing technique called accommodative rock, the “flippers” hold two different sets of lenses. One is a pair of plus lenses; the other are minus. By rapidly alternating between the two sets of lenses, the patient is forced to relax or increase focusing accommodation in order to clearly see the print, thus gaining greater facility and control over his focusing system. Patients always begin with lower powered lenses and gradually increase the strength at which they can successfully complete the task.
Mental Minus Technique & Vectograms
Another focusing technique is “mental minus“. This technique teaches patients to control how much they are focusing. Focusing problems cause people to see blurry print, especially when they read small print for long periods or have to make a lot of focusing shifts between the board and their desks.
Patients often work with special polarized slides called Vectograms. These slides allow a patient to work with a variety of targets to train central or peripheral vision, flat fusion or stereo fusion, and convergent or divergent eye positions.
The targets also help to control suppression, or the patient’s tendency to shut off an eye when his visual system is stressed. Vectograms allow the doctor or therapist to control a wide variety of visual stimuli presented to the patient while he is still operating in the natural seeing environment of free space.
The saccadic fixator is an instrument which trains eye movements, tracking, visual memory, peripheral awareness, and visual motor integration. It allows patients to set goals for themselves as they continually strive to improve their last performance. Besides patients with oculomotor dysfunctions, this machine is particularly good for young athletes; it improves their eye-hand-body coordination and response time. Overall, it’s an excellent trainer for visual stamina and efficiency.
The rotator is a tracking instrument used to increase a patient’s ability to control where she’s moving her eyes. The patient is asked to place golf tees in a rotating pegboard. As the patient’s skill improves, the speed at which the pegboard is rotating is gradually increased. This procedure is usually done while the patient is wearing a patch over one eye. Strong monocular (“one-eyed”) skills must be gained before a patient can achieve good binocular, two-eyed skills.