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Ophthalmology

Fresnel Prisms

A prism is a wedge-shaped glass piece made up of transparent material. They have the property of a light ray's deflection towards the base. Prisms are routinely used in orthoptic practice to assess the degree of squint and manage deviations so that the eye becomes orthotropic. Prisms have been used in ophthalmology to treat binocular pathologies for over 100 years. However, only after the 1950s did instrumental orthoptics not provide the desired results; pediatric ophthalmologists started using

v1 · Reviewed Nov 8, 2026 by Automated Clinical Reviewer (Strict Verbatim v1)
  • Any patient presenting with a squint or double vision needs to be thoroughly evaluated.
  • Some of these patients might have underlying uncontrolled diabetes or hypertension, which needs urgent intervention and be life-threatening to the patient.
  • The Fresnel prism trial sets are an indispensable tool for evaluating ocular motility.
  • These prisms allow for the accurate evaluation of large angle deviations.
  • The ophthalmic instruments required would include a loose Fresnel prism, binocular single vision charts, diplopia charting, Hess charting, and Goldman perimetry for testing the binocular field.
  • A prism adaptation test should be done before prescribing Fresnel prism.
  • Clear history regarding onset, duration, progression, diurnal variation, and prior episode of trauma/ fever/ association with underlying systemic disease needs to be explored.
  • Prisms are routinely used in orthoptic practice to assess the degree of squint and manage deviations so that the eye becomes orthotropic.
  • The most common use is to temporarily relieve the diplopia in cases like nerve palsies secondary to trauma, blowout fractures, decompensated phoria, divergence insufficiency, or convergence insufficiency.
  • Fresnel prisms are most commonly used as stuck-on prisms.
  • Fresnel prisms have been used widely to treat squints, amblyopia, nerve palsies, and nystagmus.
  • Nerve palsies – Fresnel prisms can be advised as a temporary measure in patients with isolated nerve pathologies to avoid diplopia or to increase the field of gaze.
  • Bedridden patients – Base-down prisms can be advised for patients to read or watch television.
  • The nursing, allied health staff, and interprofessional team help in recruitment, evaluation, prism prescription, regular counseling, and follow-up of patients requiring Fresnel prisms.
  • There are no clear contraindications in prescribing Fresnel prisms.
  • Incomitant strabismus – In incomitant strabismus, the deviation varies in different gazes; thus, prescribing Fresnel prisms helps correct deviation only in one gaze.
  • Dragged fovea – In this, the fovea of the patient is displaced secondary to an epiretinal membrane or an underlying maculopathy.
  • The Fresnel prisms are available as rigid and loose stick-on prisms.
  • The flexible prism membrane is made from optical-grade polyvinyl chloride (PVC).
  • The Fresnel prisms can be prescribed permanently or temporarily based on the underlying indications.
  • Cosmetic blemish
  • Harder to clean
  • Difficult to reapply
  • Discolours with age
  • Chromatic aberrations
  • Deterioration of visual acuity due to reflections is common with prisms greater than ten prism dioptres.
  • The vision deterioration with Fresnel prisms is more than with conventional prisms.
  • The nursing, allied health staff, and interprofessional team help monitor these patients to determine whether they are improving with Fresnel prisms.
  • review
    Fresnel Prisms. StatPearls [Internet] — Kirandeep Kaur, Bharat Gurnani — StatPearls Publishing, 2023

Decision support only. Verify against local protocols and current labeling. Source: www.ncbi.nlm.nih.gov