Testing distance stereoacuity with the Frisby-Davis 2 (FD2) test

doi:10.1016/j.ajo.2004.07.008

American Journal of Ophthalmology

Volume 139, Issue 1, January 2005, Pages 193-195

Presented at the ARVO annual meeting, Fort Lauderdale, Florida, April 28, 2004.

https://doi.org/10.1016/j.ajo.2004.07.008 Get rights and content

Purpose

To develop a presentation protocol for the new Frisby-Davis 2 (FD2) distance stereoacuity test.

Design

Prospective data collection.

Methods

Stereoacuity was tested monocularly and binocularly in 95 patients with a variety of strabismic and nonstrabismic conditions, using the FD2, employing a modified staircase procedure. The Preschool Randot Stereoacuity test and the near Frisby test were used to determine whether a patient was stereoblind.

Results

Under monocular conditions, 35 (37%) of 95 patients passed at least the largest disparity of the FD2 indicating a problem with monocular cues. The binocular protocol was then modified to include a monocular test phase. Using the new protocol, if a patient could achieve the same stereoacuity under monocular and binocular conditions, they were deemed to have no stereopsis. Testing 28 additional stereoblind patients using the new modified protocol revealed no false positives.

Conclusion

The FD2 stereotest is a useful measure of distance stereoacuity, provided the presentation protocol accounts for monocular cues.

References (5)

J.P. Frisby et al.
Clinical tests of distance stereopsisstate of the art
H. Davis et al.
Stereoacuity norms for the Frisby Davis distance stereotest at different distances

There are more references available in the full text version of this article.

Cited by (37)

Improvement in specific function-related quality-of-life concerns after strabismus surgery in nondiplopic adults
2014, Journal of AAPOS
We have previously reported improvement in psychosocial scores after strabismus surgery on the patient-derived health-related quality of life (HRQOL) Adult Strabismus 20 (AS-20) questionnaire in adults with nondiplopic strabismus. Unexpectedly, we also found improvement in the function domain. The aim of the present study was to identify which specific aspects of function-related quality of life improved postoperatively.
We retrospectively identified non diplopic adult patients with a history of childhood onset strabismus who underwent surgery and who had preoperative and 1-year postoperative AS-20 questionnaires (scored from 0 [worst] to 100 [best]). Change in scores for each item was evaluated using signed-rank tests.
A total of 20 patients were included. Of the 10 function-related AS-20 items, 9 showed significant mean improvement postoperatively (improvement ranged from 12.5 to 32.5 points, all P < 0.05). Rasch-derived mean scores improved in both reading function and general function domains (71.0 to 86.5 and 66.4 to 87.5, respectively; both P < 0.0001). Specific areas of function-related benefit were concentration, depth perception, hobbies, strain, reading, stress, and worry.
We found specific function-related quality of life benefits after strabismus surgery in nondiplopic adult patients, particularly those with childhood onset strabismus.
The use of distance stereoacuity assessment in determining the effectiveness of minus lenses in intermittent exotropia
2010, Journal of AAPOS
Minus lens treatment has been advocated for intermittent exotropia to prevent progression and has been found to be effective in improving the control of the deviation in the distance. However, the effectiveness of this treatment is difficult to ascertain because of the lack of standardized outcome measures. Distance stereoacuity has been reported to be a reliable assessment of control of intermittent exotropia. In this study, its role as an outcome measure in the efficacy of minus lens treatment was examined by the use of the Frisby-Davis Distance stereotest.
Patients (n = 24) with intermittent exotropia participated. Their distance stereoacuity was tested with the Frisby-Davis Distance stereotest at baseline and with varying minus lens powers (of −1, −2 and −3 D) that were tested randomly, as were the distance binocular visual acuity and angle of deviation.
Varying minus lens powers had a significant effect on the angle of deviation and binocular visual acuity but not distance stereoacuity. However, both measures of binocularity, distance stereoacuity, and binocular visual acuity tended to diminish with the stronger minus lens power of −3 D. Participants actually demonstrated difficulty in accommodating through the stronger lenses.
Distance stereoacuity (and binocular visual acuity) cannot reliably be used to determine the optimum minus lens strength that could be used in these patients to reduce the angle of deviation and regain binocularity in the distance. An additional observation was made that stronger lenses should perhaps be avoided to prevent binocular and visual discomfort.
Final Version of the Distance Randot Stereotest: Normative data, reliability, and validity
2010, Journal of AAPOS
Measurement of distance stereoacuity may be useful in assessing strabismic patients, especially those with intermittent exotropia. We developed the Distance Randot Stereotest as an easily administered quantitative test for distance stereoacuity in children. By using a prototype, we reported testability, validity, and normative data. Here we report normative and validity data for the final, commercially available version of the test.
We administered both the Prototype and the Final Version Distance Randot Stereotest to 156 normal volunteers (2-40 years of age) and 77 strabismic patients (4-62 years of age). Test-retest data were collected for the Final Version.
Normative Final Version scores were similar to those obtained with the Prototype; 96% were ≤100 arcsec. Test–retests were identical in 82% and within one disparity level in 100%. Final Version scores were correlated with Prototype scores (r_s = 0.64, p < 0.001). Among strabismic patients, 62.3% had abnormal stereoacuity; those with normal scores had incomitant or intermittent deviations. Nil stereoacuity was found in 27 patients, confirmed in 90.9% of retests; 17 had measurable stereoacuity, confirmed in 96.3% of retests. Patients with constant strabismus were more likely to have nil stereoacuity than patients who had intermittent strabismus (95% vs 12.2%).
Distance Randot scores from normal subjects have low variability within each age group and high test–retest reliability. There is little overlap between Distance Randot scores from normal control and strabismic patients. The Distance Randot Stereotest is a sensitive measurement of binocular sensory status that may be useful in monitoring progression of strabismus and/or recovery after strabismus surgery.
The effect of induced monocular blur on measures of stereoacuity
2009, Journal of AAPOS
To determine the effect of induced monocular blur on stereoacuity measured with real depth and random dot tests.
Monocular visual acuity deficits (range, 20/15 to 20/1600) were induced with 7 different Bangerter filters (<0.1, 0.1, 0.2, 0.3, 0.4, 0.8, and 1.0) in 15 visually normal adults. Stereoacuity was measured with Frisby and Frisby Davis Distance (FD2) real depth tests and Preschool Randot (PSR) and Distance Randot (DR) random dot tests. Stereoacuity results were grouped as either “fine” (≤60 arcsec), “moderate” (>60 and ≤200 arcsec), or “coarse/nil” (>200 arcsec to nil) stereo.
Across visual acuity deficits, stereoacuity was more severely degraded with random dot (PSR, DR) than with real depth (Frisby, FD2) tests. Degradation to worse-than-fine stereoacuity consistently occurred at 0.7 logMAR (20/100) or worse for Frisby, 0.1 logMAR (20/25) or worse for PSR, and 0.1 logMAR (20/25) or worse for FD2. There was no meaningful threshold for the DR because worse-than-fine stereoacuity was associated with −0.1 logMAR (20/15). Course/nil stereoacuity was consistently associated with 1.2 logMAR (20/320) or worse for Frisby, 0.8 logMAR (20/125) or worse for PSR, 1.1 logMAR (20/250) or worse for FD2, and 0.5 logMAR (20/63) or worse for DR.
Stereoacuity thresholds are more easily degraded by reduced monocular visual acuity with the use of random dot tests (PSR and DR) than real depth tests (Frisby and FD2). We have defined levels of monocular visual acuity degradation associated with fine and nil stereoacuity. These findings have important implications for testing stereoacuity in clinical populations.
Defining Real Change in Measures of Stereoacuity
2009, Ophthalmology
To establish the thresholds for “real change” in stereoacuity by defining long-term test–retest variability as 95% limits of agreement for 4 stereoacuity tests.
Retrospective cohort study.
We identified 36 patients (median, 17 years; range, 7–76) with any type of stable strabismus who had stereoacuity measured on 2 consecutive visits. Stable strabismus was defined as angle of deviation within 5 prism diopters by simultaneous prism and cover test and prism and alternating cover test.
Stereoacuity was measured at near using the preschool Randot and the near Frisby stereotests and at distance using the Frisby–Davis distance (FD2) and the distance Randot stereotests. Stereoacuity was transformed to log units for analysis. The 95% limits of agreement were calculated based on a 1.96 multiple of the standard deviation of differences between test and retest.
The 95% limits of agreement for change in stereoacuity thresholds at 2 consecutive visits.
The 95% limits of agreement were 0.59 log arcsec for the preschool Randot, 0.24 for the near Frisby, 0.68 for the FD2, and 0.46 for the distance Randot. These values correspond with the following octave steps (doublings of threshold; e.g., 200–400 arcsec): preschool Randot, 1.95; near Frisby, 0.78; FD2, 2.27; and distance Randot, 1.52.
A change of approximately 2 octaves of stereoacuity threshold are needed to exceed test–retest variability for most stereoacuity tests. Changes <2 octaves cannot be distinguished from test–retest variability. When used to guide patient management, caution should be taken in interpreting changes in stereoacuity of <2 octaves.
The authors have no proprietary or commercial interest in any materials discussed in this article.
Distance stereoacuity in prism-induced convergence stress
2008, Journal of AAPOS
Citation Excerpt :
These levels were chosen because the DR is manufactured to test these levels, and the FD2 is adjustable and could be set to match the manufactured DR levels. FD2 testing followed the procedure of Holmes and Fawcett,10 with the exception of the levels tested (described above) and the monocular phase, which was performed once prior to the induction of exodeviation and the results of which were applied to all subsequent FD2 tests. For example, if a subject scored nil when tested monocularly, it was assumed that he or she would not achieve factitious stereoacuity scores by using monocular cues for the remainder of the study.
In an initial study of prism-induced exodeviation, degraded stereoacuity was not associated with decreased binocular visual acuity, suggesting that accommodative convergence was not recruited. Distance stereoacuity degraded earlier when measured with the Frisby-Davis Distance (FD2) than when measured with the Distance Randot (DR). We now describe a follow-up study in which we reversed the prism order and also addressed potential biases of testing order and different measurable levels of stereoacuity to clarify the relationship between exodeviation, distance stereoacuity, and binocular visual acuity.
Convergence stress was induced with base-out prism in 20 adults and increased stepwise. Stereoacuity and binocular visual acuity were measured at each step. Disparities tested were 200, 100, and 60 arcsec, and testing was repeated at each prism step.
Most subjects showed degraded stereoacuity with the FD2 in contrast to the DR (80% vs 45%, p = 0.02). Reduction of stereoacuity occurred earlier on the FD2 than on the DR (median, 18^Δ vs 40^Δ, p = 0.001). Degradation of stereoacuity was associated with minimal change in binocular visual acuity from baseline to maximal convergence stress (median, 20/15 to 20/20).
Convergence stress is associated with decreased distance stereoacuity that does not appear to be due to accommodative convergence. Performance on real depth stereotests (FD2) is affected more than random dot tests (DR), in contrast to previous findings in intermittent exotropia. There appear to be different mechanisms for decreased stereoacuity in intermittent exotropia and under conditions of convergence stress in nonstrabismic subjects.

View all citing articles on Scopus

: Supported by grant EY11751 from the National Institutes of Health and Research to Prevent Blindness Inc., New York, New York (an unrestricted grant to the Mayo Clinic College of Medicine, Department of Ophthalmology).

View full text

Brief reportsTesting distance stereoacuity with the Frisby-Davis 2 (FD2) test

Purpose

Design

Methods

Results

Conclusion

Clinical tests of distance stereopsisstate of the art

Stereoacuity norms for the Frisby Davis distance stereotest at different distances

Brief reports
Testing distance stereoacuity with the Frisby-Davis 2 (FD2) test