Crossed and uncrossed stereoacuity at distance and the effect from heterophoria

Kwok Cheung Andrew Lam, Patrick Tse, Emily Choy, Magic Chung

Research output: Journal article publicationJournal articleAcademic researchpeer-review

12 Citations (Scopus)


Background: Previous studies have found that crossed disparities give better stereoacuity than uncrossed. When near phoria is considered, exophores had a better crossed stereoacuity and esophores had a better uncrossed stereoacuity. The current study investigated the effect of heterophoria on distant crossed and uncrossed stereoacuity. Methods: Seventy-two subjects were recruited and their distant heterophoria measured. Heterophoria within two prism dioptres was considered as orthophoric. Esophoric group had esophoria greater than two prism dioptres. Exophoric group had exophoria greater than two prism dioptres. There were 40 orthophores, 23 exophores and nine esophores. Their stereoacuity was measured with a three-rod apparatus at 6 m. Results: The mean crossed stereoacuity was 4.8″ and uncrossed stereoacuity was 7.2″ (t = -3.03, p < 0.01). The mean stereoacuity for orthophoric subjects was 5.31″, 6.02″ for exophores and 8.91″ for esophores. The distant crossed stereoacuity is better than uncrossed stereoacuity in all three groups but the difference is only significant for the exophores. Exophoric subjects demonstrated a significant difference between crossed (4.10″) and uncrossed (7.95″) stereoacuity. Conclusions: Orthophores have the best stereoacuity, followed by exophores and esophores. Exophoric subjects have a better crossed than uncrossed stereoacuity. More esophoric subjects should be recruited to confirm the difference between crossed and uncrossed stereoacuity.
Original languageEnglish
Pages (from-to)189-193
Number of pages5
JournalOphthalmic and Physiological Optics
Issue number3
Publication statusPublished - 1 May 2002


  • Crossed stereoacuity
  • Heterophoria
  • Three-rod test
  • Uncrossed stereoacuity

ASJC Scopus subject areas

  • Ophthalmology
  • Optometry
  • Sensory Systems


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