Friday, 29 May 2009 12:48

Dana Dean Optometry Vision Therapy Pilot Study Report

March 1, 2009

Summary
This document describes a vision therapy pilot study conducted at a private practice, The Dana Dean Optometry, Center for Vision Development, in San Diego, California. The retrospective study examines the effects of vision therapy of binocular deficient patients over the past five years 2003 to 2008. The participants of focus are children from ages 4 to 14 with a principle diagnosis of convergence and accommodation insufficiency. The analysis revealed significant improvement in convergence, accommodation, and specific visual fusion measures after vision therapy. This pilot study provided a better understanding of data issues, process efficiency improvements, and measurement control for an expanded study in the future.

Treatment
Standard visual convergence and accommodation treatment at The Dana Dean Optometry, Center for Vision Development consists of 45 minutes sessions conducted weekly over approximately a nine month period for a total of 28 hours of vision therapy. Patients at Dana Dean Optometry, Center for Vision Development are often from referrals from other optometrists in the greater San Diego County area, although some patients come from outside of the county and state.

Dana Dean Optometry, Center for Vision Development is located in the Old Town district of San Diego, California.
Design
The design is a pre-post treatment retrospective study in a field setting. There is no control group for this investigation.

Results
Near Point Convergence
We used two measures of near point convergence: Break and Recovery.
Break
Break in convergence is a measure of when an individual can no longer point focus on an object at near range (less than 16 inches from the distance to the nose). This broken convergence results in double vision /suppression of the object. The doctor begins by asking the individual to focus on a point at approximately 16 inches from the distance to the nose. As the doctor moves the point closer to the nose, the individual is asked to maintain focus on the point and report when they see two points.
A paired t-test was conducted to determine statistical significant differences. There was a significant improvement (alpha = 0.05) in the break distance after visual therapy as compared with prior treatment (See Table 1). Break is a measure of a convergence limitation, thus as the measure decreases, there is a corresponding increase in convergence range and more visual efficiency.

Table 1. Pre and post convergence measures: Break (distance at which focus is broken).
Figure 1 graphically displays the reduction of the measure of lack of convergence.  Figure 1 illustrates that prior to therapy individuals, on average; lose the ability to focus on a single point at about 5 inches from the nose. On average, after vision therapy, individuals are able to maintain focus to nearly an inch from the nose. This represents an improvement of nearly 75 percent.

Figure 1. Pre and post convergence measures: Break (distance at which focus is broken).

Recovery
Recovery is another way to measure convergence. In the previous measure, break, we measured the distance at which focus has been has lost resulting in double vision/suppression. Recovery refers to the point when, after focus has been broken, the individual is able to refocus, eliminating double vision. Similar, and a follow up to the procedure for measuring brake in convergence, the doctor retreats the point from the nose back out to 16 inches away from the nose. As the doctor moves the point away from the nose of the individual is asked to regain focus on the point and report when they no longer see two points (double vision) see a single point.
A paired t-test was conducted to determine statistical significant differences. There was a significant improvement (alpha = 0.05) in Recovery distance after visual therapy as compared with prior treatment (See Table 2). Recovery is a measure of a convergence limitation, thus as the measure decreases, there is a corresponding increase in convergence range and more efficient vision.

Table 2. Pre and post convergence means: Recovery (distance at which focus is regained).
Figure 2 graphically displays the reduction of the measure of recovery of convergence.  Figure 2 illustrates that prior to therapy individuals, on average; are unable to refocus on a single point until about 8 inches from the nose. On average, after vision therapy, individuals are able to regain focus at about 2 inches from the nose. This represents an improvement of nearly 75 percent.

Figure 2. Pre and post convergence insufficiency measures: Recovery (distance at which focus is regained).
Accommodation
We used two measures of accommodation: Negative relative accommodation (NRA) and Positive relative accommodation (PRA).
NRA
PRA and NRA are measures used to determine functional or flexibility in an individual’s visual system. These two measures test an individual’s ability to increase and decrease accommodation under binocular conditions when the total convergence demand is constant. The procedure involves the doctor using a phoropter. The individual's distance correction is established and is instructed to view small letters on a card 16 inches from the eyes. The Developmental Optometrist adds lenses in +0.25 increments until the patient first reports they are unclear. NRA value is the total value of the lenses added to reach the point the individual reports blurred vision. The examiner adds lenses in negative 0.25 increments until the patient first reports that they become blurry. The total value of the lenses added to reach this point is the PRA value.
PRA
A paired t-test was conducted to determine statistical significant differences. There was a significant improvement (alpha = 0.05) in accommodation as measured by PRA between pre treatment and post treatment scores (See Table 3).

Table 3. Pre and post accommodation measures in absolute values of PRA.
Figure 3 graphically displays the 53 percent improvement in pre and post scores for PRA. The significant improvement in PRA indicates better visual flexibility of individuals after vision therapy.

Figure 3. Pre and post accommodation values of PRA.
Accommodation Range
As noted earlier, NRA is not expected to be significantly affected by vision therapy. The gains from vision therapy are in the PRA measure. Taken together, that is the difference between NRA and PRA these two measures can indicate the flexibility range. Since we already determined NRA was fairly constant between pre and post measures and PRA was significantly different it was no surprise to discover a significant difference in the paired t-test of the accommodation range between pre and post measures (See Table 4).

Table 4. Pre and post accommodation range.
Figure 4 graphically displays the nearly doubling (93 percent) of the pre and post range scores and indicates greater flexibility in visual accommodation.

Figure 4. Pre and post accommodation range.
Visual Fusion Range
Visual fusion is the ability to coordinate binocular vision and produce a single clear image. Visual fusion is measured both near and far. Measurement is broken down by the point of breakage of the image as the recovery of a broken image. These combined measures give a complete description of a person’s ability to perceive a single clear image. Larger values indicate the improvement of binocular fusion.

Distant Visual Fusion

Table 5. Pre and post visual fusional range:  Distant Visual Fusion Base In: Break.

Figure 5. Pre and post visual fusional range:  Distant Visual Fusion Base In: Break.
The t-test of paired means was not statistically different.

Table 6. Pre and post visual fusional range:  Distant Visual Fusion Base Out: Break.

Figure 6. Pre and post visual fusional range:  Distant Visual Fusion Base Out: Break.
The t-test of paired means was not statistically different.

Table 7. Pre and post visual fusional range:  Distant Visual Fusion Base In: Recovery.

Table 7. Pre and post visual fusional range:  Distant Visual Fusion Base In: Recovery.
The t-test of paired means was not statistically different.

Table 8. Pre and post visual fusional range:  Distant Visual Fusion Base Out: Recovery.
The t-test of paired means revealed the means were statistically different.

Figure 8. Pre and post visual fusional range:  Pre and post fusional range:  Distant Visual Fusion Base Out: Recovery.
Near Visual Fusion

Table 9. Pre and post visual fusional range:  Distant Visual Fusion Base In: Break.
The t-test of paired means was not statistically different.

Figure9. Pre and post visual fusional range:  Distant Visual Fusion Base In: Break.

Table 10. Pre and post visual fusional range:  Distant Visual Fusion Base Out: Break.
The t-test of paired means was not statistically different.

Figure10. Pre and post visual fusional range:  Distant Visual Fusion Base Out: Break.

Table 11. Pre and post visual fusional range:  Distant Visual Fusion Base In: Recovery.
The t-test of paired means was not statistically different.

Figure11. Pre and post visual fusional range:  Distant Visual Fusion Base In: Recovery.

Table 12. Pre and post visual fusional range:  Distant Visual Fusion Base Out: Recovery.

Figure 12. Pre and post visual fusional range:  Distant Visual Fusion Base Out: Recovery.

Conclusion
The analysis revealed significant improvement in convergence, accommodation, and specific visual fusional measures after vision therapy. Statistically significant improvement was revealed in all convergence and accommodation measures. Inferential tests revealed that the statistically significant differences were in the base out recovery at for both near and distance measures. However, in all visual fusional measures there was a nominal increase after treatment as compared before treatment. Obtaining larger numbers of patients in future analysis may reveal statistically significant improvement in the other visual fusion metrics.
This pilot study provided a better understanding of data issues, process efficiency improvements, and measurement control at The Dana Dean Optometry, Center for Vision Development for an expanded study in the future.
References
Carlson, N.B., Kurtz, D., Heath, D.A., Hines C., (1996). Clinical Procedures for Ocular Examination. Second Edition. Appleton & Lange. Stamford, Connecticut.
Daum, K.M. (1984). Convergence Insufficiency. American Journal of Optometry and Physiological Optometry.  61, 16-22.
Rawstron JA, Burley CD, Elder MJ. A systematic review of the applicability and efficacy of eye exercises. J Pediatr Ophthalmol Strabismus. 2005;42(2):82-88.
Scheiman M, Mitchell GL, Cotter S, et al; the Convergence Insufficiency Treatment Trial (CITT) Study Group. A randomized clinical trial of treatments for convergence insufficiency in children. Archives of Ophthalmology. 2005;123:14-24