Optical & Dispensing Glossary: Clinical & Retail Terms

Latin abbreviation for the Right Eye. In standard clinical optical record-keeping, OD data is consistently documented in the top row of the refraction matrix.

Latin abbreviation for the Left Eye. Documented in the second row of optometric refraction charts directly below OD.

Latin abbreviation meaning 'Both Eyes'. Used when describing binocular visual acuity, systemic treatments, or identical bilateral prescription findings.

The spherical dioptric power required to correct myopia (nearsightedness, indicated by a minus '-' sign) or hyperopia (farsightedness, indicated by a plus '+' sign), measured in 0.25 diopter increments.

The lens power prescribed to correct astigmatism, indicating the differential curvature between principal ocular meridians. Always accompanied by an Axis degree.

The orientation of the astigmatic cylinder correction, specified as an integer angle between 1° and 180°. 90° represents the vertical meridian and 180° represents the horizontal meridian.

Additional plus power added to the distance spherical correction to facilitate comfortable near vision for presbyopic individuals, typically ranging from +0.75D to +3.50D.

The horizontal distance between the centers of the pupils, measured in millimeters. Accurate monocular PD measurement (from bridge center to each pupil) is essential to eliminate unwanted prismatic displacement in spectacles.

The sharpness or clarity of central vision measured at standard distance (usually 6 meters or 20 feet using a Snellen or LogMAR chart), where 6/6 denotes normal standard vision.

Multifocal ophthalmic lenses providing a seamless, line-free progression of optical powers from distance vision at the top, through intermediate distances, down to full near reading correction at the bottom.

Lenses containing two distinct focal segments separated by a visible line (e.g., flat-top D-segment or round seg), providing dedicated correction for distance and reading.

Ophthalmic lens materials with higher refractive indices (1.56, 1.61, 1.67, 1.74) that bend light more efficiently than standard plastic (1.50 CR-39), allowing significantly thinner, lighter lenses for strong prescriptions.

Specialized lens materials or surface coatings that selectively filter high-energy visible (HEV) blue light emitted by digital monitors and LED illumination, reducing digital eye strain.

A microscopic multi-layer dielectric interference coating applied to lens surfaces to eliminate internal and surface reflections, increasing light transmission to over 99% and improving nighttime driving clarity.

Optical lenses that darken automatically when exposed to ultraviolet (UV) sunlight and return to clear indoor transparency when shielded from UV rays.

An optical power element prescribed to displace image position for patients with strabismus (eye turn), phorias, or binocular diplopia (double vision), denoted in prism diopters (Δ) with a specified base orientation (Base In, Base Out, Base Up, Base Down).