The 20-prism-dioptre base-out test: an indicator of peripheral binocularity.
OBJECTIVE
To assess the ability of the 20-prism-dioptre base-out test to detect the presence of peripheral fusion in children too young to undergo formal sensory testing.


METHODS
Case series.


METHODS
Pediatric ophthalmology service at the Children's Hospital of Western Ontario, London.


METHODS
Eighty orthophoric patients (mean age at presentation 19 months [range 4 to 50 months]) with a family history of strabismus or with a diagnosis of pseudostrabismus, blocked tear duct or chalazion, followed for an average of 36 (range 6 to 129) months, and 41 patients with surgically corrected infantile esotropia (mean age at testing with the 20-PD base-out test 21 months [range 9 to 50 months]), followed for an average of 53 (range 14 to 117) months.


METHODS
Twenty-PD base-out test and red-green Worth four-dot test at near (0.3 m).


METHODS
Presence of peripheral fusion.


RESULTS
The 20-PD base-out test had a positive predictive value of 100% in detecting peripheral fusion in the orthophoric patients and 93% (95% confidence interval [CI] 82% to 100%) in the patients with surgically corrected infantile esotropia.


CONCLUSIONS
Although the 20-PD base-out test had a negative predictive value of 21% (95% CI 0% to 43%), a positive response remains a useful indicator of peripheral binocular single vision in children too young to undergo more formal sensory testing.
Ivey Institute of Ophthalmology, Children's Hospital of Western Ontario, London.
T
T
Kaban
K
K
Smith
R
R
Beldavs
W
W
Cadera
R B
RB
Orton
D002675:Child, Preschool; D004948:Esotropia / Q000601:surgery; D006801:Humans; D007223:Infant; D011237:Predictive Value of Tests; D013285:Strabismus / Q000175:diagnosis*; D015357:Vision Disparity; D014787:Vision Tests; D015348:Vision, Binocular