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  2. Prism fusion range - Wikipedia

    en.wikipedia.org/wiki/Prism_fusion_range

    When measuring horizontal fusion ranges, base in prisms assess fusional divergence while base out prisms assess fusional convergence. [3] The vertical fusional vergence amplitude can also be measured with base up and base down prisms although the horizontal PFR is typically the main focus when testing.

  3. Prism cover test - Wikipedia

    en.wikipedia.org/wiki/Prism_Cover_Test

    The prism cover test ( PCT) is an objective measurement and the gold standard in measuring strabismus, i.e. ocular misalignment, or a deviation of the eye. [1] It is used by ophthalmologists and orthoptists in order to measure the vertical and horizontal deviation and includes both manifest and latent components. [1]

  4. Prism (geometry) - Wikipedia

    en.wikipedia.org/wiki/Prism_(geometry)

    In geometry, a prism is a polyhedron comprising an n-sided polygon base, a second base which is a translated copy (rigidly moved without rotation) of the first, and n other faces, necessarily all parallelograms, joining corresponding sides of the two bases.

  5. Maddox rod - Wikipedia

    en.wikipedia.org/wiki/Maddox_rod

    The test is based on the principle of diplopic projection. [1] Dissociation of the deviation is brought about by presenting a red line image to one eye and a white light to the other, while prisms are used to superimpose these and effectively measure the angle of deviation (horizontal and vertical).

  6. Fresnel lens - Wikipedia

    en.wikipedia.org/wiki/Fresnel_lens

    A Fresnel lens ( / ˈfreɪnɛl, - nəl / FRAY-nel, -⁠nəl; / ˈfrɛnɛl, - əl / FREN-el, -⁠əl; or / freɪˈnɛl / fray-NEL [1]) is a type of composite compact lens which reduces the amount of material required compared to a conventional lens by dividing the lens into a set of concentric annular sections.

  7. Eyeglass prescription - Wikipedia

    en.wikipedia.org/wiki/Eyeglass_prescription

    A prescription of −1.00 +0.25 × 180 describes a lens that has a horizontal power of −1.00 D and a vertical power of −0.75 D. Only ophthalmologists write prescriptions in + cylinder.

  8. Cylinder - Wikipedia

    en.wikipedia.org/wiki/Cylinder

    A cylinder (from Ancient Greek κύλινδρος (kúlindros) 'roller, tumbler') [1] has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base.

  9. Fixation disparity - Wikipedia

    en.wikipedia.org/wiki/Fixation_disparity

    While the heterophoria refers to a fusion-free vergence state, the fixation disparity refers to a small misalignment of the visual axes when both eyes are open in an observer with normal fusion and binocular vision. [1] The misalignment may be vertical, horizontal or both.

  10. Dihedral symmetry in three dimensions - Wikipedia

    en.wikipedia.org/wiki/Dihedral_symmetry_in_three...

    With reflection symmetry in a plane perpendicular to the n -fold rotation axis, we have Dnh, [n], (*22 n ). Dnd (or Dnv ), [2 n ,2 + ], (2* n) has vertical mirror planes between the horizontal rotation axes, not through them. As a result, the vertical axis is a 2 n -fold rotoreflection axis.

  11. Level (optical instrument) - Wikipedia

    en.wikipedia.org/wiki/Level_(optical_instrument)

    A level is an optical instrument used to establish or verify points in the same horizontal plane in a process known as levelling. It is used in conjunction with a levelling staff to establish the relative height or levels (the vertical separation) of objects or marks. It is widely used in surveying and construction to measure height differences ...