6.2 Frame Styles & Anatomy

6.2 Frame Styles & Anatomy

Classification of Frame Styles

Ophthalmic frames are designed in several structural formats that dictate how the lenses are secured. The three primary styles are full-rim, semi-rimless, and rimless.

Full-Rim Frames

Full-rim frames completely surround the periphery of the lenses. They are typically made of plastic or metal and offer the highest level of structural stability.

• Advantages: Full-rim frames are excellent for hiding thick lens edges (especially high-minus lenses) and protecting the lens from chipping. They are also the easiest to glaze (insert lenses into) because the lenses are held in place by a bevel matching a groove in the frame eyewire.
• Disadvantages: They are heavier than semi-rimless or rimless designs and present a more noticeable visual boundary for the wearer.

Semi-Rimless (Grooved) Frames

Semi-rimless frames (often called grooved frames or nylon-suspension frames) feature a solid metal or plastic upper chassis, while the bottom of the lens is suspended by a thin nylon monofilament wire.

• Mechanism: The edge of the lens must be cut with a specialized groove (using a lens groover) during the finishing process. The nylon wire fits securely inside this groove, holding the lens against the top rim.
• Advantages: They are lighter than full-rim frames and offer a less obstructed downward field of view.
• Disadvantages: The exposed lens edges are prone to chipping if the wearer drops the glasses or bumps them. Hard lens materials like standard plastic (CR-39) are more susceptible to chipping; thus, impact-resistant materials are highly recommended.

Rimless (Drill-Mount) Frames

Rimless frames, or drill-mount frames, consist of three separate metal components: a bridge and two temple assemblies (endpieces). These components are mounted directly to the lenses.

• Mechanism: Holes are drilled directly through the lenses. Screws, nuts, washers, or plastic compression sleeves (bushings) are used to secure the metal parts to the lens.
• Material Constraints: Because the structural integrity of the eyewear relies entirely on the lenses, impact-resistant lens materials such as polycarbonate or Trivex are mandatory. Standard CR-39 plastic and high-index glass are too brittle and will crack at the drill holes under stress.
• Advantages: They are extremely lightweight, virtually invisible on the face, and offer an unobstructed field of view.

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Anatomy of a Spectacle Frame

To properly fit, adjust, and troubleshoot eyewear, an optician must master the terminology of frame parts.

graph TD
    A[Frame Front] --> B[Eyewire/Rim]
    A --> C[Bridge]
    A --> D[Endpieces]
    A --> E[Nosepad Assembly]
    F[Temples] --> G[Butt Portion]
    F --> H[Shaft]
    F --> I[Bend/Ear Portion]
    J[Hinges] --> K[Standard/Screw]
    J --> L[Spring Hinges]
    E --> M[Nosepad Arms]
    E --> N[Nosepads]

Component Breakdown

• Eyewire (Rim): The part of the frame front that surrounds and holds the lens in place.
• Bridge: The central portion of the frame front that rests on the nose and connects the two eyewires.
• Endpieces: The outer temporal corners of the frame front where the temples attach.
• Shield: A decorative metal plate found on the front or side of some plastic frames that hides the rivets securing the hinge to the frame.
• Hinges: The joints that connect the temples to the endpieces, allowing the temples to fold inward.
  • Standard Hinges: Use interlocking barrels (usually 3, 5, or 7 barrels) secured by a screw.
  • Spring Hinges: Contain an internal spring mechanism that allows the temples to flex outward beyond 90 degrees. This reduces frame warpage and increases comfort for patients with wider heads.
• Temples: The side shafts of the frame that extend over the ears to hold the glasses in position.
• Nosepad Assembly: On metal frames, this includes the nosepad arms (adjustable metal wires) and the nosepads (plastic, silicone, or glass pads that rest on the nose).

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Bridge Styles

The shape of the bridge determines how the weight of the frame is distributed across the nasal crest and slopes.

• Saddle Bridge: By spreading the frame's weight over a larger surface area, a saddle bridge minimizes pressure points.
• Keyhole Bridge: The bridge arches over the top of the nose, touching only the sides. This is an excellent style for lengthening the visual appearance of the nose or for patients with a sensitive nasal crest.
• Modified Saddle Bridge: This hybrid design features molded plastic pads that sit further down on the nose, helping to prevent the frame from sliding down.

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Temple Styles

Temples are selected based on the patient's lifestyle, occupational needs, and head shape.

• Skull Temples: The most common temple type. The shaft runs straight back, then bends downward behind the ear, hugging the contour of the skull. They are comfortable for daily wear and easy to adjust.
• Library Temples: Straight temples that do not bend down behind the ear. Instead, they run straight back and grip the sides of the head using light temporal pressure. They are ideal for reading glasses or for patients who frequently put their glasses on and take them off.
• Comfort Cable Temples: Made of flexible, wound metal cable. They wrap completely around the ear, extending down to the earlobe. They provide a very secure fit, making them perfect for children, active sports players, and patients with heavy prescriptions.
• Convertible Temples: Feature a straight temple shaft that can be custom-bent by the optician to act as a skull temple. They offer versatility in inventory for optical shops.