Concomitant strabismus should be treated immediately after its detection, independent of the child’s age. It is usually long-lasting process which requires a lot of patience and close cooperation of physician with the treated child and parents.
The treatment aims at achieving binocular vision at the full visual acuity with normal eyes alignment and motility. Full binocular vision comprises simultaneous perception, fusion with good amplitude, and stereoscopy with normal retinal correspondence. Naturally, the achievement of the ultimate goals of strabismus treatment is not always possible due to many reasons. Effective treatment requires the use of many procedures performed in the appropriate sequel: both nonsurgical and surgical.
Main principles of the strabismus treatment are the following:
Strabismus treatment should be started immediately after its detection.
The treatment aims at improving the vision in the deviating eye, producing central fixation and normal visual localization with the aid of various therapeutical techniques.
Obtaining eye alignment with the use of prisms, botulinum toxin injections or surgery.
Ocular-motor exercises and binocular vision training in the adequate phase of treatment. These exercises aim to restore the normal retinal correspondence and binocular visual localization in the free space. An ultimate goal is achievement of the simultaneous perception and fusion with wide range and possibly stereoscopy.
NONSURGICAL STRABISMUS MANAGEMENT
Correction of refraction errors
Treatment of strabismus begins with the evaluation of refraction error and prescription of the appropriate spectacles or contact lenses. Refraction errors are the most common causes of the concomitant strabismus. Refraction is assessed with the automatic kerato-refractometer (in the younger children with Retinomax; (see Fig. 20) following an application of 0.25% to 1% atropine eye drops for 3 days. This is necessary to paralyze accommodation.
Following refraction examination, fixation should be evaluated for each eye separately with the use of visuscope. Then, the anterior segment of each eye and eye fundus are evaluated.
Hypermetropia, myopia, and astigmatism are completely or nearly completely corrected to achieve good visual acuity and break pathological accommodative-convergence ratio. If anisometropia is present, especially more than 3 Dsph and 1.0 Dcyl, contact lenses are needed to allow the development of the binocular vision. As the rule, both contact lenses or spectacles should be worn permanently.
In some forms of the concomitant strabismus only wearing glasses is sufficient treatment. The best example is the accommodative esotropia. The treatment of this form of strabismus is described in the chapter “ Esotropia.”
Amblyopia develops in children with anisometropia, unilateral concomitant strabismus or in case of the anatomical changes: congenital or acquired in the early childhood (congenital early-onset cataract, persistent hyperplastic primary vitreous, corneal opacity from glaucoma or dystrophy, lid masses, retinal dystrophy or inflammation). After treating anatomical changes, amblyopia ex anopsia is being treated.
Basic amblyopia therapy is the obturation of the sound eye that aims to force the fixation with deviating eye and improvement in the visual acuity in this eye. Obturation means not only total cover but also artificially weakened retinal image in one eye with the use of the visual acuity reductors (Bangerter’s lenses) or penalizing method.
The best is total cover of the sound eye with special obturator, glued to the skin or, especially in the older children, use of appropriately color with black pupil soft contact lens (see Fig. 44 and45).
Fig.44.Amblyopia management by sound eye patching.
Fig.45 Treatment of amblyopia with soft occlusion-color contact lens of left eye.
The time of sound eye obturation is gradually shortened until the visual acuity has been the same in both eyes. In this stage of the treatment, visual acuity reductors from totally opaque to more and more transparent, changed with the improvement in the visual acuity in the amblyopic eye may be used or atropine solution may be applied.
Penalization is a therapeutical method in which the sound eye has to be “punished” by the decrease in the visual acuity, which treats the amblyopia in the deviating eye, improves retinal correspondence and the angle of deviation. Classic penalizing method means that the fixing eye adapts to the distant vision only with the use of atropine and prescription of the corrective spectacles adjusted to the distant vision, dependent on the refraction error. Amblyopic eye is adapted to the near vision with the use of the stronger lens, adding +1 to +3.0 Dsph over complete refraction correction. With this therapy the child acquires proper binocular spatial orientation. Penalization decreases also accommodative factor that may lead to a decrease in or reduction of the angle of strabismus.
Some clinicians use different variations of the penalization method: penalization at near, at distance, complete, alternative, selective, reduced or maintaining.
Additional treatments of amblyopia besides occlusion are pleoptic exercises. Their aim is to restore normal function of the deviating eye macula and domination over the peripheral retina so that macular suppression is removed, visual acuity improved and retinal correspondens,with good spatial localization is changed. Pleoptic techniques have been elaborated by Bangerter and Cuppers. In the treatment euthyscope is used.(see Fig.46).
It is a device with which orthoptist, observing eye fundus, dazzles peripheral retina with the place of anomalous fixation with simultaneous cover of the macula. Afterimage is produced with preserved macular vision, forcing the deviating eye to nearly central fixation. Localizing exercises of the deviating eye supplement the treatment. Haidinger phenomenon and Campbell apparatus are also used in the amblyopia treatment.(see Fig.47).
Fig.47.Phenomenon of Haidinger using to pleoptic exercises improve visual acuity and fixation of the amblyopic eye.