Predicting Unaided Distance Vision and Refractive Error

Flashcards designed to review key concepts related to predicting unaided distance vision and refractive errors.

Uncorrected myopia

Always reduces distance vision regardless of accommodation.

Accommodative impact on myopia

Accommodation does not help uncorrected myopes to see clearly at a distance and may worsen distant vision.

Uncorrected hyperopia

May or may not reduce distance vision depending on the patient's age and accommodation.

Astigmatism and vision

Always reduces distance vision, but generally less than myopia or hyperopia that cannot be overcome by accommodation.

Refractive error prediction

The process of estimating refractive error based on unaided vision or vice versa.

Sphere-Equivalent Refractive Error

A single number representing refractive error when there is a cylindrical component.

Vector Length

A calculation used in refraction that combines spherical and cylindrical values for predicting vision.

Raasch's model

A predictive model utilizing empirical data to relate refractive errors to visual acuity.

Smith's model

A predictive model that includes pupil diameter in the assessment of refractive error and vision.

Rule of thumb for myopia

Estimates that 1 line of vision is lost per -0.25D of myopic defocus.

Rule of thumb for astigmatism

Estimates that 1 line of vision is lost per 0.50D of uncorrected astigmatism.

Visual Acuity (VA)

A measure of the clarity or sharpness of vision, often assessed through acuity charts.

Sph/Cyl Rx

Refers to the spherical and cylindrical components of a prescription for corrective lenses.

Accommodation

The ability of the eye to change its focus from distant to near objects.

Pupil diameter's effect

Influences predicting unaided vision notably in Smith's model.

Empirical data

Data collected from direct observation or experimentation, used for predicting visual outcomes.

Spherical myopia

A form of myopia where the distance vision is impaired due to the shape of the eye.