Section 14.2: Temple & Ear Adjustments
Key Takeaways
- Pantoscopic tilt is the downward inclination of the frame front (typically 8-12 degrees) and aligns the optical axis with the visual axis.
- For every 2 degrees of pantoscopic tilt, the lens optical center (OC) must be positioned 1 mm below the pupil center.
- The temple bend must start exactly at the ear crotch; bending too early pushes the frame forward, while bending too late causes slipping.
- The temple tip must follow the mastoid bend to distribute pressure along the skull rather than pointing directly into the sensitive mastoid process.
- To correct a crooked frame, raise the temple on the side that sits high or lower the temple on the side that sits low.
Section 14.2: Temple & Ear Adjustments
Quick Summary: Properly adjusting the temples and ear fittings ensures the spectacles remain securely in place without causing pain or pressure points. Key adjustments include establishing the correct pantoscopic tilt (8-12 degrees) for optical alignment, managing temple spread to prevent lateral pressure, and contouring the mastoid bend behind the ear to distribute the frame's weight evenly off the sensitive mastoid process.
Introduction to Temple Alignment
The temples of a spectacle frame must hold the glasses securely on the patient's head by applying gentle, uniform pressure along the sides of the skull and behind the ears. Misaligned temples can lead to glasses sliding down the nose, severe discomfort, headaches, or painful pressure sores behind the ears. Temple adjustments are divided into three primary categories: angle adjustments at the hinge (pantoscopic/retroscopic tilt), lateral spread adjustments, and anatomical contouring behind the ear.
Pantoscopic and Retroscopic Tilt Mechanics
The vertical tilt of the frame front relative to the face is controlled by adjusting the angle of the temples at the hinge.
PANTOSCOPIC TILT RETROSCOPIC TILT
(Standard) (Avoided)
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| / <-- 8-12° \\ | <-- Bottom tilts out
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Pantoscopic Tilt
Pantoscopic tilt is the inclination of the frame front downward toward the cheeks, relative to the vertical plane. The industry standard for proper pantoscopic tilt is 8 to 12 degrees. This tilt serves both cosmetic and optical purposes. Visually, a slight tilt conforms to the natural slope of the face. Optically, it is required to align the lens's optical axis with the eye's visual axis. When a patient looks straight ahead, their eyes are in the primary gaze. However, when they look downward to read or walk, their eyes rotate. Tilting the lenses ensures that their visual axis remains perpendicular to the lens surface during downward gaze, preventing the introduction of unwanted oblique astigmatism.
The Rule of Optical Center Placement
Because the frame front is tilted, the optical center (OC) of the lens must be positioned to align with the visual axis. The standard rule of thumb is:
- For every 2 degrees of pantoscopic tilt applied to the frame, the optical center of the lens must be lowered 1 mm below the patient's pupil center.
- If a frame is adjusted to have 10 degrees of pantoscopic tilt, the optical centers of the lenses must be positioned 5 mm below the patient's pupil centers. Failure to apply this rule results in unwanted prismatic effects and visual distortion.
Retroscopic Tilt
Retroscopic tilt (also known as retrograde tilt) occurs when the frame front tilts upward, moving the bottom rim of the frame away from the cheeks and the top rim closer to the forehead. Retroscopic tilt is optically undesirable because it misaligns the visual axis during near tasks. It typically occurs when the patient's ears sit lower than their eyes. Opticians adjust temple tilt by holding the frame endpiece with nylon-jaw pliers and using hinge angling pliers to bend the temple hinge up or down.
Temple Spread and Lateral Pressure
Temple spread refers to the lateral angle of the temples when they are fully opened.
- Under-spread (Too Narrow): If the temples open to an angle less than 90 degrees (or are too narrow for the patient's head), they will press tightly against the side of the head, specifically at the temples or the zygomatic arch. This pressure causes discomfort, headaches, and acts as a wedge, pushing the frame forward and off the patient's nose.
- Over-spread (Too Wide): If the temples open too wide (greater than 95 degrees), the frame will sit loosely on the head. Lacking lateral friction, the spectacles will slide down the nose constantly.
- Adjustment: On metal frames, temple spread is adjusted by bending the endpiece or hinge box inward or outward. On plastic frames, the optician must heat the endpieces using a hot air blower or glass bead pan before bending them to avoid cracking the acetate.
Anatomical Ear Contouring and the Mastoid Bend
The portion of the temple that bends down behind the ear is critical for securing the frame. The human ear has a natural curve where it meets the skull, and the bone directly behind the lower ear is the mastoid process.
The Ear Crotch and Bend Location
The bend of the temple must begin exactly at the top of the ear—the point where the ear attaches to the skull, known as the ear crotch.
- Bend starts too early: If the bend is made before the ear crotch, the temple will push the frame forward, lifting the nosepads off the nose and reducing vertex distance.
- Bend starts too late: If the bend is made past the ear crotch, the temple will not hook onto the ear, allowing the spectacles to slip down the nose.
Mastoid Process Pressure Relief
The mastoid process is a sensitive bony protrusion of the skull. If the temple tip is straight or bent sharply into this area, it causes severe pain and localized swelling. The optician must create a mastoid bend by contouring the plastic temple tip to bend down behind the ear, then curve slightly inward to follow the skull's shape, and finally flare slightly outward at the very tip to avoid digging in. The temple should hold the frame by distributing flat friction against the side of the skull, not by pinching the ear or pressing the mastoid bone.
Common Temple Types
- Skull Temples: The standard style, which bends downward behind the ear and conforms closely to the skull.
- Comfort Cable Temples: Feature flexible, plastic-coated metal cables that wrap completely around the ear, holding the frame firmly in place. They are ideal for children, active sports, or heavy safety glasses.
- Library Temples: Straight temples that do not bend down behind the ears, holding the frame entirely through lateral pressure against the side of the head. They are common in reading spectacles for easy on-and-off use.
Temple Adjustment Troubleshooting Checklist
Spectacle frames frequently require troubleshooting for alignment errors. The following checklist details the symptoms, causes, and corrective actions:
| Symptom / Alignment Issue | Likely Hinge or Temple Cause | Corrective Action |
|---|---|---|
| Frame sits crookedly (Right side sits higher than left side) | Right ear is higher than left, or right temple is angled downward | Bend the right temple upward at the hinge, or bend the left temple downward |
| Frame sits too close to cheeks (Lashes or bottom rim touch face) | Excessive pantoscopic tilt | Decrease pantoscopic tilt by bending both temples upward at the hinge |
| Spectacles constantly slip down nose | Temple spread is too wide, or the bend begins too far back | Decrease temple spread, and move the bend forward to start exactly at the ear crotch |
| Pain and redness behind the ear | Temple is pressing directly on the mastoid process | Contour the temple tip to distribute pressure off the mastoid bone |
| Bottom rim of frame touches face when smiling | Frame sits too low, or has too much pantoscopic tilt | Decrease pantoscopic tilt to lift the bottom rim away from the cheeks |
To correct a frame that sits higher on the patient's right side than on the left side, what adjustment should be made?
What is the optical rule of thumb relating pantoscopic tilt to the placement of the lens optical center?
A patient complains of pain and pressure on the sensitive bone directly behind the ear lobe. Which part of the frame is misaligned, and what is the corrective action?