Constant Esotropia with Normal 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.
Effective for suppression and amblyopia.
Use constant occlusion until fusion is attained and gradually reduce as fusion develops.
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.
Treat most types of unsteady and/or eccentric fixation in conjunction with acuity improvement program.
Stimulate fovea initially under monocular and subsequently under binocular conditions (anti-suppression) to improve resolution and simultaneous perception.
Gradually decrease monocular target size and element separation.
Large (greater than 2 to 4 p.d.) and steady E.F. should ordinarily be treated first as oculomotor problem; stimulate foveal fixation (e.g., entoptic imagery and auditory feedback) combined with pursuit and saccadic training.
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 and pathological diplopia training.
For constant esotropia with normal correspondence the ultimate goal is awareness of pathological diplopia when eye deviates.
Stimulus parameters are brightness, contrast, color, size, on-period, position, and movement of targets.
Reinforce therapy with kinesthetic, auditory, and visual feedback.
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.
For distance esotropias greater than 15 p.d., RX plus add of distance angle divided by PD to get ortho at some near distance (i.e., centration point at reciprocal of plus add.
This reduces the deviation according to size of the AC/A and power of the added lens.
Large amounts of base-out prism are very useful for constant esotropias with NRC.
Vertical prisms should be prescribed for the vertical deviation present with eyes in "ortho" position.
Use near plus to achieve "ortho" and a cover test.
Rx greater prism power before eye with paretic muscle.
This is the final portion of therapy.
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 angles (i.e., more than 20 p.d. eso).