Section 14.1: Nosepad & Bridge Adjustments

Section 14.1: Nosepad & Bridge Adjustments

Quick Summary: Proper nosepad and bridge adjustments are critical for determining the vertical alignment of the frame, the vertex distance, and how comfortably the spectacle weight is distributed across the nasal bridge. Opticians must master the alignment of three primary pad angles—frontal, splay, and flare—and understand how narrowing or widening the pads directly affects frame height and distance from the eyes.

Clinical Overview of Bridge Fitting

Spectacle frames are held on the face at three primary points of contact: the nasal bridge and the two ears. Among these, the bridge is responsible for bearing the majority of the spectacle weight and determining the vertical positioning of the lenses. A poorly fitted bridge causes physical discomfort, skin irritation, and optical misalignment, which can lead to visual fatigue.

When performing a frame fitting, the optician must evaluate the patient's nasal structure. Noses vary significantly in width, slope, and height of the nasal bridge. The primary goal of bridge adjustment is to distribute the weight of the frame over a large surface area of the nose, avoiding concentrated pressure points. A fundamental rule of opticianry is to always adjust and fit the frame to the patient's face before taking any optical measurements, such as pupillary distance (PD) or segment height (seg height). If a frame is measured before fitting, subsequent adjustments to the bridge or nosepads will change the resting position of the lenses, invalidating the measurements.

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The Three Nosepad Angles

To achieve a comfortable, slip-free, and pain-free fit, the flat surface of each nosepad must rest completely flat against the nose. This requires the optician to analyze and adjust the nosepads along three separate axes of rotation, corresponding to three primary angles: the frontal angle, the splay angle, and the flare angle.

                   FRONT VIEW                     TOP VIEW
                 Frontal Angle                  Splay Angle
                    \\  |  /
                     \\ | /
                     [ ]  [ ]                      [ ]
                      Nose                          Nose

1. Frontal Angle

The frontal angle is the vertical tilt of the nosepads when viewed from the front of the frame. The human nose is narrower at the top and flares outward toward the cheeks, typically creating a slope of approximately 20 degrees from the vertical plane. The nosepads must be rotated so that their vertical inclination matches this slope. If the frontal angle is too vertical (less than 20 degrees) or too flared (greater than 20 degrees), the pad will not rest flat. Instead, either the upper or lower edge of the pad will dig into the nasal tissue, causing redness, indentations, and discomfort.

2. Splay Angle

The splay angle is the horizontal angle of the nosepads when viewed from above, looking down onto the frame. The nose splays outward as it moves from the bridge toward the face. The standard splay angle is between 25 and 30 degrees. Properly adjusting the splay angle ensures that the entire face of the nosepad, from front to back, makes contact with the nose. If the splay angle is too narrow, the back edge of the pad will dig into the nose; if it is too wide, the front edge will dig in. Misalignment here reduces the friction holding the frame, causing the glasses to slide down.

3. Flare Angle

The flare angle (sometimes referred to as the transverse or lateral angle) is the tilt of the nosepad when viewed from the side. It represents the slope of the nose as it projects outward from the forehead to the tip, which typically ranges from 10 to 15 degrees. If the nosepads do not match the flare angle, the top or bottom of the pad will tilt away from the nose, leaving a single sharp edge to support the frame's weight.

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Mechanics of Nosepad and Pad Arm Adjustments

Adjustable nosepads are mounted on malleable wire arms called pad arms. These arms are manipulated using specialized pad adjusting pliers, which allow the optician to adjust the position and angle of the pads without scratching the frame or tearing the soft silicone pads.

Narrowing vs. Widening Nosepads

The distance between the two nosepads is the primary adjustment used to alter the frame's vertical height and distance from the eyes (vertex distance):

• Widening the Nosepads (Spreading): Spreading the nosepads farther apart increases the bridge opening. This allows the frame to slide lower on the patient's nose. Consequently, widening the nosepads lowers the frame vertically on the face and decreases the vertex distance (moving the lenses closer to the eyes).
• Narrowing the Nosepads: Squeezing the nosepads closer together reduces the bridge opening. This prevents the frame from sliding down, causing it to ride higher on the nose. Narrowing the nosepads raises the frame vertically and increases the vertex distance (moving the lenses farther from the eyes).

Vertical Pad Arm Shifts

Sometimes, an optician needs to change the vertical height of a frame without altering the vertex distance. This is done by bending both pad arms vertically relative to the frame front:

• Bending both pad arms downward pushes the frame front upward, raising the glasses on the patient's face.
• Bending both pad arms upward allows the frame front to drop downward, lowering the glasses on the face.

Lateral Shifting and Vertex Distance Adjustments

If a frame is off-center (e.g., sitting too far to the patient's left), both pad arms must be adjusted in the same direction to shift the frame:

• To shift the frame to the patient's right, the optician bends both pad arms toward the patient's right.
• To adjust vertex distance independently of height, the optician can bend both pad arms closer to the frame front (decreasing vertex distance) or push them farther back from the frame front (increasing vertex distance).

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Bridge Types and Material Considerations

Frame materials and bridge designs dictate how adjustments are executed:

• Metal Frames: Usually feature adjustable nosepads mounted on pad arms. Nosepads are available in various materials, such as silicone (high friction, prevents slipping, soft on skin) and acetate (hard plastic, durable, slides on/off easily). Mountings are typically screw-on, snap-on, or slide-on.
• Plastic (Cellulose Acetate) Frames: Standard plastic frames have fixed, molded bridges. The fit of a zyl frame relies on selecting a frame during dispensing that matches the patient's nose. Zyl bridges include the saddle bridge, which spreads weight uniformly across the top and sides of the nose, and the keyhole bridge, which flares outward at the top, touching only the sides of the nose. If a plastic frame sits too low, opticians can insert adhesive silicone nosepads or retrofit the frame by drilling and installing metal pad arms.

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Nosepad Adjustment Effect Matrix

The following matrix summarizes how specific pad and pad arm adjustments alter the vertical position of the frame and the vertex distance: