Occasional Esotropia with Anomalous Correspondence
Sharpens retinal image and/or alters vergence of eyes; may lead to lessened suppression, enhanced sensory fusion, and stronger stimulus to fusional vergence.
Equally sharp retinal images more important than equal image sizes in anisometropia.
Disregard possible aniseikonia initially but prescribe equal base curves and center thickness in significant anisometropia prophylactically.
Fully correct anisometropia and/or astigmatism.
Avoid "fogging" eso-deviations for distance; can Rx more plus later when latency is uncovered.
Cycloplegic examination helpful for eso-deviations with hyperopia.
What is the deviation at distance and near after neutralizing the refractive error?
Added plus power at near for eso-deviations and high AC/A's.
This reduces the deviation according to size of the AC/A and power of the added lens.
Use base-out prism with caution for occasional esotropias with ARC because of the possibility of prism adaptation and an increase in the angle.
Vertical prisms should be prescribed for the vertical deviation present with eyes in "ortho" position.
When the patient fuses, Rx vertical prism based on associated phoria; even as little 1/2 p.d. may be helpful for fusion.
In paresis, Rx greater prism power before eye with paretic muscle.
Effective for suppression and amblyopia.
Use a maximum of 2 to 4 hours per day to avoid increasing the frequency of the eye turn.
Complete occlusion better than graded.
Regimen should be specifically prescribed and monitored; for infants and young children, occlude preferred eye 1 day/week/year of age.
Six to 8 weeks is minimum period for initial occlusion and for continued occlusion beyond last measured improvement.
Two hrs/day is minimum time for effective occlusion.
These patients seldom have very deep amblyopia.
Treat most types of unsteady and/or eccentric fixation in conjunction with acuity improvement program.
Stimulate fovea under monocular but primarily under BINOCULAR conditions (anti- suppression) to improve resolution and simultaneous perception.
Gradually decrease monocular target size and element separation.
Reinforce therapy with kinesthetic, auditory, and visual feedback.
Active treatment involves binocular (dichoptic) stimulation of peripheral retinal areas followed by gradual encroachment upon central areas.
Use dissimilar (1st degree) targets initially, then similar (2nd degree) targets.
Next, physiological diplopia training.
DO NOT emphasize pathological diplopia training for occasional esotropes with ARC.
Stimulus parameters are brightness, contrast, color, size, on-period, position, and movement of targets.
Reinforce therapy with kinesthetic, auditory, and visual feedback.
For occasional esotropia with anomalous correspondence train with fusional vergence therapy.
Use divergence initiation therapy in the troposcope.
Vergence training requires fairly good acuity (20/60 or better) and not much suppression.
Surgery is likely to be needed as part of the total program for large angle deviations.
Sensory fusion should be highly developed before motor fusion training begins.
For both, however, qualitative aspects are more important than quantitative aspects (viz., facility more important than magnitude).
Improve grades of fusion in order of difficulty.
Train both lower and upper stereo-thresholds.
Facility and accuracy of accommodation is very important as binocularity develops.
Transference to free- space situations must be recognized.
When changing mechanical advantage of oculo-rotary muscles by surgery, post- surgical comitance is desired goal.
Smaller surgical changes on several muscles tend to give better comitance.
Second operation may be necessary to correct vertical deviations.
Early surgery may be advantageous for esotropia.
Pre- as well as post-surgical optical correction and orthoptics can be helpful.
Surgery may be required for large heterophorias (i.e., greater than 20 p.d. eso).