Fresnel press-on prisms
Fresnel press-on prisms are thin, flexible plastic prisms applied to the back surface of a spectacle lens.1,2 The membranes give an inexpensive but relatively temporary prismatic correction, and they can be changed readily if the prism power must be modified often.2,3
A conventional prism grows thicker from apex to base, and the larger the prism, the thicker the base.1 A Fresnel prism avoids that thickness by stacking a tower of small prisms of equal power on a thin piece of plastic, and the finished prism is only 1 mm thick.1 The membranes come in powers up to 30 prism diopters, are light in weight and cause minimal distortion.2
The facets reduce visual acuity slightly, particularly at high power, and the prisms are noticeable to others and harder to clean than conventional lenses.1,2 The plastic can be cut with scissors, and a Fresnel prism can therefore cover one sector of the lens.1 A sectorial prism suits a partially paralyzed muscle that needs different prism in different directions of gaze.1
More detail
Fresnel prism also lets the clinician try a vertical imbalance correction on existing lenses before ordering it, as a temporary alternative to a slab-off.1,3 A near-only horizontal prism can go on the lower portion of the lenses.1 In homonymous hemianopia, a sectorial prism goes on the side of the field defect with its base toward the defect, so the wearer sees into that field without turning the eyes as far.1
Sources (6)
- Brooks and Borish, System for Ophthalmic Dispensing, ch. 17
- von Noorden and Campos, Binocular Vision and Ocular Motility, ch. 24
- Meister and Sheedy, Introduction to Ophthalmic Optics, ch. 12
- Rutstein, R., Daum, K. (1997). Anomalies of Binocular Vision: Diagnosis & Management, Mosby.
- Fresnel Prism Therapy for Diplopia. (2022). American Academy of Ophthalmology. https://www.aao.org/disease-review/fresnel-prism-therapy-diplopia
- Fresnel Prisms: An Important Tool for Optometrists. (2019). Review of Optometry. https://www.reviewofoptometry.com/article/fresnel-prisms-an-important-tool-for-optometrists
Reviewed October 2026