Refractive error types, lens power calculations, and clinical optics concepts tested on the NBEO.
39 cards · basic cards · AI-written, checked twice. Edit anything.
- What is emmetropia?
- The refractive state in which parallel light rays focus exactly on the retina with accommodation relaxed.
- What is myopia?
- A refractive error in which parallel light rays focus in front of the retina.
- What is hyperopia?
- A refractive error in which parallel light rays focus behind the retina.
- What is astigmatism?
- A refractive error in which unequal curvature between meridians causes light to focus at two separate points instead of one.
- What is presbyopia?
- The age-related loss of accommodative amplitude caused by progressive hardening and reduced elasticity of the crystalline lens.
- What is a diopter?
- A unit of lens (or vergence) power equal to the reciprocal of the focal length measured in meters.
- Lens power in diopters equals ____.
- 1 divided by the focal length in meters
- The thin lens vergence formula is ____, where U is object vergence, D is lens power, and V is image vergence.
- U + D = V
- How does increasing vertex distance affect the effective power of a plus (convex) lens?
- It increases the effective plus power at the eye.
- How does increasing vertex distance affect the effective power of a minus (concave) lens?
- It decreases the effective minus power at the eye.
- Prentice's rule states that induced prism in prism diopters equals ____.
- the decentration in centimeters multiplied by the lens power in diopters
- What is the base curve of a spectacle or contact lens?
- The curvature of a reference surface of the lens, commonly the front surface for spectacles, used to define the lens form.
- Spherical equivalent equals ____.
- the sphere power plus half the cylinder power
- What is with-the-rule astigmatism?
- Astigmatism in which the steepest corneal meridian is near 90 degrees (vertical).
- What is against-the-rule astigmatism?
- Astigmatism in which the steepest corneal meridian is near 180 degrees (horizontal).