The central question in the clinical management of binocular anomalies is whether or not to treat, and if so, what treatment procedures should be used and in what order. The philosophy behind development of this program is that strabismic and nonstrabismic anomalies of binocular vision can be considered to lie along a continuum and that a general plan of treating binocular anomalies can include both strabismics and nonstrabismics.
The basis for this approach is that strabismus can be viewed as a more severe form of heterophoria in that the angle of deviation (tonic innervation) is typically larger in strabismus and that the associated complications, such as suppression and amblyopia, are more common and more severe in strabismus than in heterophoria. Using this rationale, the sequence of procedures used in treating strabismus and heterophoria are similar. And, many of the treatment procedures are the same. Surely there are other approaches to the clinical management of binocular anomalies. What is proposed here is an approach that is very useful in clinical practice and readily accepted by students and practitioners who are looking for a logical, organized, and practical clinical model for treating patients with binocular anomalies.
In the model, four "kinds" of strabismus are identified on the basis of constant or occasional squint, and normal or anomalous correspondence. Additionally, three "kinds" of heterophoria are identified on the basis of a low, normal or high AC/A ratio. These four kinds of strabismus and three kinds of heterophoria require sufficiently different treatment sequences to preclude a single, standardized treatment approach. The model proposed here accounts for these differences, and directs treatment to the specific needs of a patient with a binocular anomaly. In short, the model is problem oriented.
In this model all of the available treatment options are utilized in treating patients with specific binocular anomalies. In the sequence of their usual order of implementation in practice, these options include:
optical correction of ametropia,
added lenses,
prisms,
occlusion,
vision training, and
surgery.
In the program the options listed above are presented in a suggested order of implementation of use for each patient. Of course, each patient is different and these treatment considerations are just that, CONSIDERATIONS. You may decide not to utilize a particular treatment for an individual patient based on many factors which clinically exist for your particular patient. However, consideration should be given to each treatment option before eliminating it from the treatment plan. The model proposed here lists a suggested order of consideration for each type of case. Clinical experience has shown that rejecting considerations for good reason is appropriate in many individual cases. However, not considering them or rejecting them without recognizing the consequences is poor clinical practice and will invariably lead to poor treatment results.
In developing the treatment model, strabismus is considered first. The basis for the model relies heavily on the schema designed by Flom that was developed to estimate the prognosis for functional correction of strabismus. In this prognosis schema, the main factors affecting prognosis for both esotropia and exotropia are constancy (constant or occasional strabismus) and retinal correspondence (anomalous or normal). Thus, the treatment model presented here is constructed around constancy and retinal correspondence because they are most the important factors in determining the sequence of the different treatment options. In the model for treating strabismics, there are four combinations of constancy and retinal correspondence: occasional strabismus and normal correspondence (best prognosis), constant strabismus and normal correspondence, occasional strabismus and anomalous correspondence, constant strabismus and anomalous correspondence (worst prognosis).
From this analysis, then, there are four different kinds of cases of strabismus, each requiring a somewhat different sequence of treatment considerations. Treatment Sequence Considerations for strabismics (Esotropes and Exotropes) are presented in the individual treatment sections of this program.
NRC NRC ARC ARC General
Occas Const Occas Const Considerations
1 1 1 1(a) 1. Optical Rx
2 5 2 8 2. Added Lenses
3* 6* 3* 2*(c) 3. Prisms
4 2 4 3(b) 4. Occlusion
3 4(b) 5. VT: Amblyopia
5 4 5 5 6. VT: Suppression
6 6 7. VT: ARC
6 7 7 7 8. VT: Sens/Motor
7 8 8 9(d) 9. Surgery
Letters in parentheses designate the treatment sequence if cosmesis is the main goal.
For nonsquinters, the prognosis for functional correction is typically high; the main determinant in the sequence of treatment is the magnitude of the AC/A ratio, which in conjunction with the tonic vergence (distance phoria) determines the near phoria. Thus, three basic "kinds" of nonsquint or phoria cases result: low, normal, and high AC/A ratios. And each of these basic cases includes persons with low, normal, and high tonic vergence (respectively, distance exophoria, orthophoria, and esophoria). The three basic cases consequently consist of the following:
The treatment of phoria cases in this model is sequentially different for these three case types. The table below shows that the differences in treatment sequence center about when one should consider use of added lenses and prisms.
Treatment Sequence Considerations for Phoria Patients
(Esophorias and Exophorias)
Low AC/A Normal AC/A High AC/A General
Tonic Tonic Tonic
Vergence Vergence Vergence
Low Norm Hi Low Norm Hi Low Norm Hi Considerations
1 1 1 1. Optical Rx
7 3 2 2. Added Lenses
2* 2* 3* 3. Prisms
3 4 4 4. Occlusion
4 5 5 5. VT: Amblyopia
5 6 6 6. VT: Suppression
--- --- --- 7. VT: ARC
6 7 7 8. VT: Sens/Motor
8 8 8 9. Surgery
* Vertical prisms are often useful for vertical deviations in fused position (associated phoria); base-out prisms are especially helpful for esophorias at distance; for exophorias, base-in prisms at near should be considered if VT is impractical or unsuccessful.