visuoscope
A visuoscope is an ophthalmoscope modified to measure eccentric fixation. The instrument projects a small fixation target, classically a star, onto the retina, and the target's position on the fundus shows the retinal area the patient uses to fixate.1,2
The eye not being tested is occluded, because eccentric fixation is a monocular condition.3 The patient looks at the center of the target, and the examiner views the fundus.1,3 Central fixation places the foveal reflex at the center of the grid, and eccentric fixation places the reflex outside the center.3 Each mark on most targets represents 1 prism diopter of eccentric fixation. The examiner records the direction and magnitude of eccentric fixation and also judges its steadiness.3 Visuoscopy is the most common clinical tool for assessing eccentric fixation in an amblyopic patient.3
More detail
The position of the target on the retina does not by itself establish true eccentric fixation, so the examiner also asks whether the target appears straight ahead.1 A straight-ahead report means that straight-ahead localization has shifted from the fovea to the eccentric area, which denotes true eccentric fixation.1 A report that the target lies to the side means the fovea has kept its straight-ahead localization, and the finding is called eccentric viewing.1
Sources (22)
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 14
- Pickwell's Binocular Vision Anomalies, appendix (glossary)
- Duckman, Visual Development, Diagnosis, and Treatment of the Pediatric Patient, ch. 22
- Cooper, J., Gelfond, I., Carlson, P.E., Campolattaro, B. and Wang, F. (2004). Comparison of Eccentric Fixation Measurements Using the Streak Target of an Ophthalmoscope and a Traditional Visuoscopy Target. Journal of Pediatric Ophthalmology & Strabismus, 41(2), pp.89-93.
- Kalnica-Dorosenko, K., Kalnupa, M., Svede, A. and Valeina, S. (2021). Eccentric fixation measurements using visuoscopy and Macula Integrity Tester (MIT) in children with amblyopia. Proceedings of SPIE, 11815, p.118150Y.
- Steinman, S.B., Steinman, B.A. and Garzia, R.P. (2000). Foundations of Binocular Vision: A Clinical Perspective. New York: McGraw-Hill.
- spiedigitallibrary.org: 12.2597226.short
- PubMed Central: PMC2330257
- PubMed Central: PMC5858252
- sa1s3.patientpop.com: 58074.pdf
- PubMed: 36007287
- PubMed: 15825745
- IOVS: article.aspx?articleid=2778609
- JAMA Network: 624642
- JAMA Network: 267839
- EyeWiki: Visual_Acuity_Assessment_in_Children
- American Academy of Ophthalmology: vision-screening-amblyopia
- American Academy of Ophthalmology: bcscsnippetdetail.aspx?id=86627e6b-2ff0-403d-b5d6-dce4eeed9e
- PubMed Central: PMC2000981
- IOVS: article.aspx?articleid=2203038
- Review of Optometry: visuoscopy-review
- ui.adsabs.harvard.edu: abstract secondary
Reviewed October 2026