Optometric Management Of Nearpoint Vision Disorder, 2e [VERIFIED]
The term vision therapy is, for practical purposes, synonymous with the term orthoptics, and the terms will be used interchangeably. Both vision therapy and orthoptics refer to eye movement and eye focusing exercises. Vision therapy is performed by optometrists, whereas orthoptics is typically conducted by certified orthoptists who practice under the supervision of ophthalmologists. A primary difference between optometric vision therapy and ophthalmologic orthoptics is that optometrists conduct vision therapy mostly in the office, whereas orthoptists usually prescribe exercises to be performed at home.
Optometric Management of Nearpoint Vision Disorder, 2e
Many vision therapy regimens have incorporated non-optometric interventions, such as general body movements, exercise, diet, and importantly, standard remedial educational techniques. Studies reporting the results of such vision therapy regimens are difficult to interpret because the effectiveness of these regimens may be due to the non-optometric interventions, such as standard remedial educational techniques, that are employed, rather than due to the vision therapy itself. Moreover, these other elements may be better provided by professionals who are not optometrists, such as remedial educational specialists. Beauchamp notes that "[o]ne may legitimately question the ability of an optometrist to function in such complex substantive areas" outside of optometry (Beauchamp, 1986).
Symptoms common to all types of accommodative dysfunctions are reduced nearpoint acuity, a general inability to sustain nearpoint visual acuity, asthenopia, excessive rubbing of the eyes, headaches, periodic blurring of distance vision after prolonged near visual activities, periodic double near vision, and excessive fatigue at the end of a day (Suchoff, 1986).
Third, vision therapy is used to restore normal accommodative dysfunction. According to Scheiman and Wick (1994), vision therapy is generally necessary in the management of accommodative excess and accommodative infacility, and is also important in many cases of accommodative insufficiency and ill-sustained accommodation.
A third line of studies have sought to prove that the improvements in accommodation brought about by vision therapy translate into improvements in performance on various tasks. Weisz (1979) examined the results of vision therapy on nearpoint performance in children with deficiencies in accommodation. A total of 28 children who were diagnosed with some type of accommodative dysfunction were divided into 2 groups that were matched for age and school grade. One group received accommodative vision therapy and the other received perceptual-motor training without accommodative therapy. Both groups were given two 30-min sessions per week, and were treated for an equal length of time. A pen and paper task requiring fine nearpoint discrimination was given to all patients before and after training to assess transfer effects of accommodative therapy on this task. The group provided with accommodative therapy reached normal levels of accommodation within an average of 4.5 sessions, and showed a significant decrease in the number errors on the pen and paper task after therapy compared to the group that received perceptual-motor training.
By contrast, the AOA has concluded that vision therapy has a place in the treatment of amblyopia patients. The AOA Optometric Clinical Practice Guideline Care of the Patient with Amblyopia (1994) states:"[a]ctive monocular and binocular amblyopia therapies, as opposed to passive management (e.g., occlusion), reduce the total treatment time needed to achieve the best visual acuity," and that it "is designed to remediate deficiencies in four specific areas: eye movements and fixation, spatial perception, accommodative efficiency, and binocular dysfunction." An AOA position statement on vision therapy for amblyopia states that "[t]he most commonly encountered amblyopia usually requires 28 to 40 hours of office therapy."
The AOA states that 28 to 36 hours of vision therapy are usually required, but that longer durations of treatment may be required for convergence excess complicated by esotropia, oculomotor dysfunction, an accommodative disorder, other visual anomalies, or associated conditions such as stroke, head trauma, or systemic diseases (AOA, 1995).
Few clinical reports have been published on the effectiveness of vision therapy for convergence excess. In one of the few reports, Shorter (1993) described an uncontrolled retrospective study of the optometric records of 12 non-presbyopic patients with convergence excess (Shorter, 1993). Subjects received different types and durations of vision therapy treatment, and were treated by different clinicians. Subjects received vision therapy office visits at a frequency ranging from once per week to once per month, with home exercises prescribed for 4 to 6 days per week in addition to office therapy. Three of the subjects were also treated with bifocals. Median duration of vision therapy was 4 months. Of 11 subjects for whom post-treatment symptom status was recorded, 8 (73 %) reported improvements in symptoms of headache, blurred vision, eye strain, intermittent diplopia and/or trouble reading (Shorter, 1993). However, there was no statistically significant improvements in vergence ranges after vision therapy.
There is consensus in the optometric and ophthalmologic professions that vision therapy/orthoptics is an effective treatment for convergence insufficiency. Early uncontrolled studies had shown that convergence insufficiency rapidly and reliably responds to simple exercises, such as "push-ups," in almost all cases (Mann, 1940; Cushman, 1941; Lyle, 1941; Hirsch, 1943; Duthie, 1944; Mayou, 1945; Mellick, 1950; Passmore, 1957; Norn, 1966; Hoffman, 1973; Wick, 1977; Dalziel, 1981; Kertesz, 1982; North, 1982; Patano, 1982; Cohen, 1984; Daum, 1984; Deshpande, 1991a; Deshpande, 1991b). The rapidity and consistency of this response made it less likely that the outcomes of these uncontrolled studies could be due to bias, such as regression toward the mean, the natural history of the disease, or placebo effects, although these sources of bias as well as bias due to test-retest phenomena can not be ruled out. More recently, controlled clinical studies have demonstrated the effectiveness of vision therapy for convergence insufficiency.
The published clinical studies of orthoptics/vision therapy for convergence insufficiency show that a limited number of office visits are required for resolution of convergence insufficiency. Published clinical studies of vision therapy/orthoptics for convergence insufficiency show that the average number of office visits for convergence insufficiency is usually less than a dozen. Only Hoffman (1973) reported a much higher average number of office visits (24); all vision therapy exercises were conducted in the office. The orthoptic (ophthalmology) literature reports successful treatment of convergence insufficiency with fewer office visits than are reported in the optometric vision therapy literature. Orthoptists/ophthalmologists rely more on home exercises, whereas optometric vision therapists tend to perform more in-office therapy.
There is a lack of evidence of the effectiveness of vision therapy for esotropia. In the clinical practice guideline on the management of esotropia, the AAO (1992) concluded that active vision therapy/orthoptics "is no longer considered effective" in the treatment of esotropia and "its use should be discouraged."
Several authors of reviews of the optometric literature on the effectiveness of vision therapy in esotropia have drawn conclusions about the overall effectiveness by adding together the success rates" from observational studies of vision therapy in esotropia, grouping together studies of various designs, strengths, and weaknesses (Flax, 1978). No attempt is made to critically evaluate the inherent limitations of these studies, or the difficulties of drawing conclusions about the effectiveness of vision therapy from them. The authors make reference to "controlled" studies, implying that these studies are controlled clinical trials, whereas in actual fact, these studies were observational studies with noncontemporaneous comparison groups.
Studies should be grouped by design, with the greatest weight given to the strongest studies (i.e., those studies that, by design, have the least potential for bias) (Anderson, 1990). The only prospective randomized controlled clinical trial of optometric vision therapy in esotropia published to date has found no benefit from active vision therapy (Fletcher, 1969). This study has been ignored in reviews of the effectiveness of optometric vision therapy for esotropia.
Published case series on vision therapy for esotropia report widely varying durations of treatment and frequencies of office visits, without any consistent relationship between increased duration of treatment and frequency of office visits with improved outcomes. Cooper and Medow (1993) noted that "[o]rthoptist orthoptic therapy is primarily given to the patient to do at home while optometric orthoptic therapy utilizes both office and home therapy."
There is no evidence that optometric orthoptic therapy, performed largely in the office, is superior to orthoptist orthoptic therapy, which is primarily given to the patient to do at home. Outcomes of long-term office-based treatment of constant or intermittent esotropia have not been demonstrated to be superior to home therapy with periodic followup. Therefore, prolonged vision therapy/orthoptic treatment for esotropia is not only investigational, but is also not medically necessary. Patients with esotropia may be transferred to a home vision therapy program with periodic follow-up.
The number of office visits necessary and duration of treatment for a given indication is also significantly different between orthoptists and vision therapists. As Cooper and Medow (1993) noted in a review of intermittent exotropia, "[o]rthoptist orthoptic therapy is primarily given to the patient to do at home while optometric therapy utilizes both office and home therapy." Despite the differences in approach, there are no consistent differences in the effectiveness of orthoptic exercises reported in the orthoptist literature and the optometric literature. The AOA, in their Clinical Practice Guideline on Strabismus (1995) stated that optometric vision therapy generally requires 25 to 75 hours of office visits. However, treatment durations reported in the literature vary widely, with no consistent relation of number of office visits, duration of treatment, or transfer to home exercise programs, to results of treatment.