Eyewear and Glasses Case Glossary: 75+ Terms Explained

Eyewear has a vocabulary that can be confusing, especially when you are comparing cases, choosing lenses or describing a repair. This glossary covers the terms you are most likely to meet. Terms are grouped by topic, then listed alphabetically within each group.

Frame parts

Bridge. The part of the frame that connects the two lenses and rests on or above the nose.

Brow bar. A bar across the top of some frames, above the lenses, often a design feature on aviators and browline frames.

End piece. The outer corner of the frame front where the temple attaches.

Eyewire (rim). The part of the frame that surrounds and holds the lens.

Frame front. The front section of the glasses, holding the lenses, excluding the temples.

Hinge. The joint connecting the frame front to each temple.

Hinge barrel. The interlocking cylinders that make up a hinge, held together by a screw.

Keyhole bridge. A bridge shaped like an old keyhole, resting on the sides of the nose.

Nose pads. Small pads, often clear or silicone, that rest on the nose on many metal frames and some plastic frames.

Pad arms. Small metal arms that hold adjustable nose pads.

Spring hinge. A hinge with a built-in spring that lets the temple flex outward and return. Also called a flex hinge.

Temple. The arm of the glasses that extends from the hinge over the ear.

Temple tip. The end of the temple that rests behind the ear, often covered with plastic or rubber.

Frame styles and materials

Acetate. A plant-based plastic used for many frames. It can be adjusted with gentle heat by an optician.

Aviator. A teardrop-shaped frame style, often metal, popular for sunglasses.

Browline. A frame style with a bold upper rim and thinner or rimless lower edges.

Cat-eye. A frame style with upswept outer corners.

Full-rim. Frames with a rim surrounding the entire lens.

Memory metal. Flexible titanium alloys that return to shape after bending.

Rimless. Glasses with no rim; lenses are mounted directly to the bridge and temples with screws or fittings.

Semi-rimless. Frames with a rim along only part of the lens, usually the top.

Stainless steel. A strong, corrosion-resistant metal used for frames.

Titanium. A lightweight, strong and corrosion-resistant metal used for frames.

TR-90. A flexible thermoplastic material used for lightweight, durable frames.

Wraparound. A frame that curves around the face, common in sport sunglasses.

Measurements

A measurement. The horizontal width of a lens.

B measurement. The vertical height of a lens.

Base curve. The curvature of the front surface of a lens. Wraparound frames have a higher base curve.

Boxing system. A standard method of measuring lenses using a box drawn around the lens shape.

Bridge width (DBL). The distance between lenses. DBL stands for distance between lenses.

Frame width. The total width of the frame front.

Pupillary distance (PD). The distance between the centers of your pupils, used to position lenses correctly.

Segment height. For bifocal and progressive lenses, the vertical position of the reading area or fitting point.

Temple length. The length of the temple arm.

Our guide to frame size numbers explains these measurements in practice.

Lens materials and types

Bifocal. A lens with two distinct powers, usually for distance and reading, separated by a visible line.

CR-39. A standard plastic lens material.

Glass lenses. Lenses made of glass; scratch resistant but heavier and more likely to shatter than plastic.

High-index. Lens materials that bend light more efficiently, allowing thinner lenses for stronger prescriptions.

Photochromic. Lenses that darken in ultraviolet light and lighten indoors.

Polarized. Lenses with a filter that reduces glare from reflective surfaces.

Polycarbonate. An impact-resistant, lightweight lens material often used for children's and safety eyewear.

Progressive. Lenses with a gradual change in power from distance to near, with no visible line.

Single vision. Lenses with one prescription power throughout.

Trivex. An impact-resistant, lightweight lens material with good optical clarity.

Lens coatings and treatments

Anti-fog. A coating or treatment that reduces fogging.

Anti-reflective (AR). A coating that reduces reflections on lens surfaces.

Blue light filter. A coating or material that reduces some blue light transmission.

Crazing. A network of fine cracks in a lens coating, often caused by heat.

Hard coat. A scratch-resistant coating on lens surfaces.

Hydrophobic. A coating that repels water.

Mirror coating. A reflective coating on the outside of a lens.

Oleophobic. A coating that repels oils and smudges.

Tint. Color added to a lens, as in sunglasses.

UV protection. Blocking of ultraviolet light. Important for sunglasses; many lenses provide UV protection.

See caring for coated lenses for care guidance.

Glasses case terms

Clamshell. A hard case with two halves joined by a hinge.

Double case. A case with two compartments for two pairs.

EVA. Ethylene-vinyl acetate, a shock-absorbing foam used for semi-rigid cases.

Flocking. A velvet-like lining made of short fibers attached to the case interior.

Folding case. A flat case that folds into a triangular or rectangular shape around the glasses.

Hard case. A rigid case designed to resist crushing.

Lining. The interior surface of a case that touches the glasses.

Magnetic closure. A closure held shut by magnets.

Microfiber. A fine synthetic fabric used for cloths, pouches and linings.

Semi-rigid case. A case with a molded foam or padded shell, usually zippered.

Sleeve. A soft slip-in case without a closure.

Soft case. A pouch or sleeve without a rigid structure.

Spring hinge case. A clamshell case with a spring-loaded hinge that snaps open and closed.

Visor clip. A clip that attaches to a car sun visor to hold glasses.

Our materials comparison and closures comparison go into more detail.

Care and repair terms

Adjustment. Bending or reshaping a frame to improve fit, usually done by an optician.

Lens cloth. A cleaning cloth, usually microfiber.

Lens spray. A cleaning solution made for eyeglasses.

Repair kit. A kit with precision screwdrivers, screws and sometimes nose pads.

Thread-lock. A liquid applied to screw threads to reduce loosening. Removable formulas are preferred for glasses.

Ultrasonic cleaner. A device that uses high-frequency sound waves in liquid to clean.

Professional terms

Optician. A professional who fits and dispenses glasses and makes adjustments.

Optometrist. An eye care professional who examines eyes and prescribes glasses and contact lenses.

Ophthalmologist. A medical doctor specializing in eye care and surgery.

Prescription (Rx). The written specification of lens powers and measurements.

Terms you may see on receipts

Receipts and order forms often abbreviate terms. OD and OS refer to the right and left eye, SPH and CYL describe prescription powers, and AR or ARC indicates an anti-reflective coating.

Frequently asked questions

What is the difference between an optician and an optometrist?

An optometrist examines eyes and writes prescriptions. An optician fits and dispenses glasses and makes adjustments based on a prescription.

What does DBL mean on glasses?

Distance between lenses, the bridge width in millimeters.

What is acetate in glasses?

Acetate is a plant-based plastic used for many frames, valued for its color options and adjustability.

What is a clamshell glasses case?

A hard case made of two halves joined by a hinge, usually with a spring or magnetic closure.

Bottom line

Understanding eyewear terms makes it easier to choose frames, lenses and cases, and to describe what you need when a repair is required. Bookmark this glossary for the next time a product page or receipt uses a term you do not recognize.