What is a drill-mount frame?

A drill-mount frame is another name for a rimless frame. Instead of having frame material surrounding the lenses, the bridge and temples attach directly to the lenses through small holes drilled near the edges. This creates the lightest and most minimalist frame style, though it requires impact-resistant lens materials like polycarbonate or Trivex.

What are spring hinges and why are they important?

Spring hinges contain an internal spring mechanism that allows eyeglass temples to flex outward beyond their normal open position. They are important because they absorb stress when glasses are removed with one hand, accommodate slightly different head widths, reduce the need for frequent adjustments, and extend the overall life of the frame.

What type of frame is best for high prescriptions?

Full-rim frames are best for high prescriptions because the frame material surrounds and conceals the lens edges. High-minus prescriptions produce thick lens edges, and high-plus prescriptions create thick lens centers. Full-rim frames hide these thick areas, improving the cosmetic appearance. Rimless frames should be avoided for high prescriptions because the thick edges are fully visible.

What is the difference between skull temples and cable temples?

Skull (library) temples curve gently along the side of the head and rest against the skull behind the ear without hooking around it. Cable temples wrap around the ear in a hook shape, providing a more secure grip. Cable temples are recommended for children, active patients, and anyone whose glasses tend to slide down.

Frame Types & Construction: Full-Rim, Semi-Rimless, and Rimless Eyewear

Three Main Frame Types

Eyeglass frames are categorized by how they hold the lenses. Each type offers distinct advantages in weight, aesthetics, durability, and lens compatibility. Understanding these categories is fundamental to both the ABO exam and daily dispensing.

Full-Rim Frames

Full-rim frames completely encircle each lens with frame material (the eyewire). This is the most traditional and most common frame type. Full-rim frames offer several advantages:

Maximum lens security: The lens is fully enclosed, reducing the risk of chipping or popping out
Hides lens edges: Thick lenses (high prescriptions) are partially concealed by the frame material
Compatible with all lens types: Any lens material or design works in a full-rim frame
Most durable: The complete eyewire protects the lens edges from impact

Full-rim frames are available in every material (metal, plastic, combination) and every style. They are the safest recommendation for high prescriptions, active patients, and children.

Semi-Rimless (Half-Rim) Frames

Semi-rimless frames use frame material along only part of the lens edge, typically the top. The exposed edge is held by a thin nylon monofilament cord that fits into a groove cut along the lens edge (called a grooved or grooveset mounting).

Characteristics of semi-rimless frames:

Lighter than full-rim frames
More open, minimalist appearance
The lens must have a groove cut along its exposed edge to hold the cord
Not suitable for all lens materials (very thin or brittle lenses may crack during grooving)

When dispensing semi-rimless frames, verify that the nylon cord is intact and properly seated during every adjustment visit. A worn or improperly seated cord is the most common reason for lenses popping out of semi-rimless frames. Keep replacement cord in your dispensary.

Rimless (Drill-Mount) Frames

Rimless frames, also called drill-mount or three-piece frames, have no frame material surrounding the lenses at all. The bridge and temples attach directly to the lenses through holes drilled near the edges.

Rimless frame advantages and considerations:

Lightest weight: No frame material around the lenses means minimal weight
Most discreet appearance: The lenses appear to float on the face
Lens material matters: Polycarbonate and Trivex are preferred because they resist cracking at the drill holes; glass and standard CR-39 are more prone to fracture
Edges are fully exposed: Thick lenses are visible from the side, making rimless a poor choice for high prescriptions

Mounting glass lenses in a rimless frame. Glass is brittle and prone to cracking at the drill points, especially with temperature changes or minor impacts. Always recommend polycarbonate or Trivex for rimless mountings.

Feature	Full-Rim	Semi-Rimless	Rimless
Lens security	Highest	Moderate	Lower
Weight	Heaviest	Moderate	Lightest
Hides lens thickness	Yes	Partially	No
Durability	Highest	Moderate	Lower
Lens compatibility	All types	Groovable materials	Drillable materials
Aesthetic	Bold/visible	Moderate	Minimalist

Temple Types

Temples (sometimes called earpieces or side bars) extend from the frame front to rest along or behind the ears. Different temple designs serve different needs:

Skull (library) temples: The most common type. They follow the contour of the skull and curve gently behind the ear. Named because they rest against the skull without hooking.
Cable (comfort cable) temples: These curl around the ear like a hook, providing a more secure grip. Preferred for children, active patients, and anyone whose glasses tend to slide.
Spring-loaded (convertible) temples: Feature a built-in spring mechanism near the endpiece that allows the temple to flex outward beyond its normal open position. This absorbs stress from one-handed removal and improves comfort for different head widths.
Riding bow temples: Similar to cable temples but with a more elongated curve. Common in athletic and military eyewear.

Hinge Mechanisms

The hinge connects the temple to the frame front at the endpiece. Standard hinges use a simple barrel-and-pin mechanism. Spring hinges add an internal spring or flex mechanism that allows outward flex.

Spring hinges are advantageous because they:

Accommodate slightly wider or narrower heads without adjustment
Absorb stress when glasses are removed with one hand
Reduce the frequency of needed realignment
Are harder to stretch out of shape

Spring hinges add slight bulk at the temple-to-frame junction and can be more expensive to repair. However, they significantly extend frame life and reduce adjustment visits, making them a smart recommendation for most patients.

Frame Construction Details

Beyond the main type, frame construction includes several important details:

Endpieces: The extensions from the eyewire that connect to the temples. Endpieces can be integral (part of the frame front) or separate components joined by screws.
Pad arms and nose pads: In metal frames, adjustable pad arms allow fine-tuning of the frame's position on the nose. Plastic frames typically have an integrated saddle bridge.
Eyewire closure: Full-rim frames typically have a screw at the eyewire closure point. This must be checked regularly to prevent loosening.

Clinical Relevance

Frame type selection directly impacts patient satisfaction and lens performance. A high-minus patient in rimless frames will have visibly thick edges and a less attractive appearance. A child in a rimless frame risks breakage. Matching the frame type to the prescription, lifestyle, and cosmetic preferences ensures the best outcome.

Key Takeaways

Full-rim frames offer maximum lens security and hide thick edges, suitable for all prescriptions
Semi-rimless frames use a nylon cord in a grooved lens edge for a lighter, more open look
Rimless (drill-mount) frames are the lightest but require impact-resistant lens materials
Cable temples provide more secure fit than skull temples for active patients and children
Spring hinges improve comfort, durability, and reduce realignment needs
Match frame type to the patient's prescription, lifestyle, and aesthetic preferences