Spectacle Frames
1) Introduction
The spectacle frame is not merely a support for lenses; it plays a crucial role in the optical performance, cosmetic appearance, comfort, and durability of spectacles. The frame determines how lenses are mounted, aligned, and worn. A well-designed frame enhances patient satisfaction, while poor choice may lead to discomfort, reduced vision, or lens damage.
2) Parts of a Spectacle Frame
- Front: Holds the lenses; consists of the eyewires (rims), bridge, and end pieces.
- Bridge: Connects the two eyewires; can be keyhole, saddle, or adjustable pad bridge.
- Nose Pads: Support on the nose; can be fixed or adjustable, plastic or silicone.
- End Pieces: Connect the frame front to the temples via hinges.
- Temples (or sides): Arms extending back to the ears; include temple shaft, bend, and temple tips.
- Hinges: Join end piece to temple; may be barrel, spring-loaded, or hidden.
3) Classification of Frames
Frames can be classified in several ways:
(a) Based on Material
- Metal Frames: Stainless steel, titanium, aluminum, nickel alloys. Durable, sleek, corrosion-resistant (esp. titanium).
- Plastic Frames: Cellulose acetate, Optyl, nylon, TR-90. Lightweight, available in various colors/styles.
- Combination Frames: Plastic front with metal temples or vice versa.
- Special Materials: Memory metals (flexible alloys), wood, carbon fiber for luxury frames.
(b) Based on Weight
- Heavy frames: Thick plastic or metal, less comfortable but durable.
- Lightweight frames: Titanium, rimless, or TR-90 plastic frames preferred for comfort.
(c) Based on Temple Position
- Skull temples: Most common; curve around the ear.
- Cable temples: Coil around ear for secure fit (common in children, sports).
- Straight-back temples: Run straight back without bend, easy to put on/off with helmets.
(d) Based on Lens Mounting
- Full-rim frames: Encircle entire lens with eyewire.
- Semi-rimless frames: Nylon cord or partial frame holds lens.
- Rimless frames: Lenses drilled and mounted with screws; lightweight, but require strong materials (polycarbonate/Trivex).
(e) Based on Coloration/Style
- Solid, patterned, translucent, or layered coloration.
- Fashion-oriented styles: aviator, cat-eye, round, geometric, etc.
4) Frame Construction
- Monoblock construction: Entire front made from one piece of material.
- Combination construction: Metal and plastic integrated for style and function.
- Spring hinges: Allow flexible temple movement, increasing durability and comfort.
- Adjustability: Nose pads and temple tips allow customization to fit facial anatomy.
5) Frame Selection Principles
- Face Shape: Oval faces suit most frames; round faces suit angular frames; square faces suit round/oval frames.
- Prescription:
- High minus lenses: Choose small frames to minimize edge thickness.
- High plus lenses: Round frames reduce center thickness and weight.
- Comfort: Lightweight, balanced, with good nose pad and temple fit.
- Occupation: Cable temples for sports, metal frames for professional look, safety frames for industrial use.
- Cosmetic Appeal: Style, color, and fashion preferences matter in acceptance.
6) Frame Measurements (Boxing & Datum Systems)
Standardized systems define frame size for proper lens fitting:
- Boxing System: Each eyewire lens opening is enclosed in a rectangle (“box”). Key parameters:
- A measurement: Horizontal lens size (width).
- B measurement: Vertical lens size (height).
- DBL (Distance Between Lenses): Bridge size.
- ED (Effective Diameter): Largest diagonal across the lens, used to calculate blank size.
- Datum System: Uses a horizontal line (datum line) through the geometric center of the lens; less common today.
7) Size, Shape & Mounting of Frames
- Size: Influences lens thickness and cosmetic appearance. Smaller frames reduce edge thickness in minus lenses.
- Shape: Round, rectangular, aviator, cat-eye, etc. Shape selection depends on face type and prescription needs.
- Mounting: Full-rim, semi-rimless, or rimless. Choice depends on durability, aesthetics, and lens material strength.
8) Effect of Frame on Field of View
- Large frames may increase field of view but lead to thicker, heavier lenses.
- Small frames reduce thickness but may limit peripheral vision.
- Rimless and semi-rimless designs provide a more open field of view.
- Frame shape influences prismatic effects in peripheral gaze.
9) Clinical & Dispensing Relevance
- Frame choice must balance prescription requirements, patient comfort, durability, and fashion.
- Improper selection may result in lens decentration, increased thickness, and patient dissatisfaction.
- Knowledge of frame materials and construction helps in repairs and adjustments.
- Frame measurements ensure efficient lens ordering and edging.
Types and Parts of Spectacle Frames
1) Introduction
Spectacle frames provide the mechanical support for ophthalmic lenses, positioning them correctly in front of the patient’s eyes. Frames affect not only comfort and durability but also cosmetic appearance, weight distribution, and field of view. An optometrist must be familiar with all parts of a frame and the variety of frame types available to recommend the most suitable one for each patient.
2) Anatomy: Parts of a Spectacle Frame
- Front: The main portion that holds the lenses.
- Rims (Eyewires): Encircle or partially surround the lenses.
- Bridge: Connects the two rims; rests on the nose.
- Nose Pads: Provide support and distribute weight comfortably on the nose; may be fixed or adjustable.
- End Pieces: Outer extensions that connect the front to the temples via hinges.
- Temples (Sides): Extend backward to hold the frame in place.
- Temple Shaft: Long straight portion.
- Bend: Curved part near the ear.
- Temple Tips: End portion, rests behind the ear for stability.
- Hinges: Joints connecting the front (end piece) to the temples, allowing folding. Variants include barrel hinge, spring hinge, and concealed hinge.
Note: In rimless and semi-rimless frames, the front is minimal, and the temples are directly attached to the lenses or supported with nylon cord.
3) Types of Frames Based on Structure
- Full-Rim Frames: Eyewire fully surrounds the lens. Strong, secure, and suitable for all prescriptions.
- Semi-Rimless (Supra) Frames: Frame covers only part of the lens (usually upper half); bottom edge supported by nylon cord. Light and cosmetically appealing.
- Rimless Frames: No eyewire around lenses. Lenses are drilled and mounted with screws or bushings. Very lightweight and fashionable but require strong materials (Trivex, polycarbonate).
- Three-Piece Mounts: Separate bridge and temples directly attached to the lenses with screws.
4) Types of Frames Based on Material
- Plastic Frames:
- Cellulose acetate: Common, available in many colors, easily adjustable but less durable.
- Optyl: Epoxy resin plastic, lightweight, hypoallergenic, heat adjustable.
- TR-90/nylon blends: Flexible, strong, ideal for sports eyewear.
- Metal Frames:
- Stainless steel: Strong, corrosion resistant, lightweight.
- Titanium: Hypoallergenic, durable, extremely light, corrosion resistant.
- Aluminum: Lightweight but less flexible.
- Nickel-silver alloys: Economical but may cause allergies.
- Combination Frames: Plastic and metal combined for durability and style.
- Luxury Materials: Carbon fiber, wood, buffalo horn, precious metals for high-end frames.
5) Types of Frames Based on Temple Design
- Skull Temples: Curve gently around the ears; most common.
- Cable Temples: Coil tightly around ear; secure fit for children or sports eyewear.
- Straight-Back Temples: Extend straight without bend; convenient for helmets or headgear.
- Convertible Temples: Adjustable to both straight-back and cable form.
6) Types of Frames Based on Style & Fashion
- Aviator Frames: Tear-drop shape, originally for pilots; now popular fashion frames.
- Cat-Eye Frames: Upswept outer edges, often used in women’s fashion eyewear.
- Round/John Lennon Frames: Circular lenses, retro look.
- Wayfarer Style: Thick plastic full-rim with trapezoidal shape.
- Geometric Frames: Hexagonal or polygonal designs, trendy and unique.
7) Importance in Optical Dispensing
- Correct identification of parts helps in adjustments and repairs during dispensing.
- Knowledge of frame types guides appropriate selection for prescriptions (e.g., rimless not suitable for very high minus powers).
- Material knowledge ensures comfort and safety (hypoallergenic titanium for sensitive skin, TR-90 for sports).
- Fashion styles improve patient acceptance and compliance with spectacles.
Classification of Spectacle Frames
1) Introduction
Spectacle frames come in a wide variety of designs and constructions. To ensure optimum vision, comfort, durability, and cosmetic acceptance, it is important to classify them systematically. The major basis of classification includes material, weight, temple position, and coloration. Each category has unique advantages and limitations that influence dispensing decisions.
2) Classification by Material
Frame material directly affects durability, weight, flexibility, adjustability, and cost.
- Plastic Frames:
- Cellulose acetate: Common, colorful, easy to adjust, but less durable.
- Optyl: Lightweight, hypoallergenic, retains shape memory when heated.
- Nylon/TR-90: Strong, flexible, resistant to breakage; used in sports eyewear.
- Metal Frames:
- Stainless steel: Corrosion resistant, durable, lightweight.
- Titanium: Hypoallergenic, extremely light, strong, expensive.
- Nickel silver: Economical but may cause skin allergy.
- Aluminum: Very light but not flexible; limited adjustments possible.
- Combination Frames: Mix of plastic and metal for durability and cosmetic effect.
- Luxury Materials: Gold, platinum, carbon fiber, wood, or horn; mostly cosmetic and fashion-driven.
3) Classification by Weight
Weight plays a major role in comfort and tolerance. Heavier frames may cause nasal indentation or discomfort during prolonged wear.
- Heavy Frames:
- Thick acetate or heavy metal frames.
- Durable but less comfortable for long use.
- Lightweight Frames:
- Titanium, TR-90, rimless designs.
- Provide better comfort, especially for high prescriptions where lens weight is already significant.
4) Classification by Temple Position
The position and design of temples affect frame stability and fit.
- Skull Temples: Curve gently behind the ears; most commonly used design.
- Cable Temples: Coil tightly around the ear for maximum security; used in children, sports, and safety spectacles.
- Straight-Back Temples: Extend straight back without bend; convenient for wear with helmets or headgear.
- Low-Set Temples: Positioned lower on the eyewire; useful for balancing weight in certain frame styles.
- High-Set Temples: Attached high on the frame; can provide a different aesthetic balance.
5) Classification by Coloration
Frame coloration influences cosmetic acceptance and fashion appeal. Patients often choose frames based on color as much as material or design.
- Solid Colors: Uniform coloration across the frame, e.g., black, brown, blue.
- Patterned Colors: Tortoiseshell, marble, or camo effects for cosmetic variety.
- Translucent Frames: Transparent or semi-transparent plastics (crystal, clear styles).
- Layered/Gradient Colors: Frames with two or more tones, gradient from top to bottom, or inside–outside contrasts.
- Metallic Finishes: Polished gold, silver, gunmetal, rose gold—popular in metal frames.
6) Dispensing & Clinical Relevance
- Frame material determines durability, adjustability, and allergy risk (e.g., titanium for sensitive patients).
- Weight classification is critical for comfort in long-term wear, especially in children and high-power prescriptions.
- Temple design affects stability (cable temples ideal for sports; skull temples for routine use).
- Coloration plays a strong role in cosmetic acceptance, influencing patient compliance.
- Knowledge of classifications allows the dispenser to balance optical, mechanical, and cosmetic needs of each patient.
Frame Construction
1) Introduction
The construction of a spectacle frame determines its strength, adjustability, weight distribution, and aesthetics. Properly constructed frames not only hold the lenses securely but also ensure comfort for prolonged wear. Construction techniques vary depending on whether the frame is plastic, metal, or a combination.
2) Methods of Frame Construction
- Monoblock Construction: The front (rims and bridge) is made as a single molded or machined unit. Common in plastic frames.
- Combination Construction: Different materials (metal + plastic) are used together—for example, plastic rims with metal temples.
- Laminated Construction: Layers of acetate or composite materials bonded together for strength and aesthetic effects.
- Drill-Mount Construction: Lenses are drilled and directly attached to bridge and temples with screws or bushings (rimless design).
- Grooved Mount Construction: Semi-rimless design where nylon cord fits into a groove around the lens edge.
3) Components of Frame Construction
- Eyewires (Rims): The part holding the lenses. Can be closed metal loops, plastic rims, or partial cords.
- Bridge: Joins the two eyewires; type depends on comfort and stability.
- Nose Pads: Attached to bridge or pad arms; made of silicone, PVC, or titanium.
- End Pieces: Connect the front to the temples via hinges.
- Temples: Provide stability; may be skull, cable, or straight-back designs.
- Hinges: Provide flexibility and folding action; can be standard or spring-loaded.
4) Bridge Designs
- Saddle Bridge: Spreads weight evenly across the nose, common in plastic frames.
- Keyhole Bridge: Shaped like an old-fashioned keyhole; rests more on the sides of the nose than the top, reducing pressure.
- Adjustable Pad Bridge: Metal pad arms with silicone or plastic pads that can be adjusted for individual fit.
- Comfort Bridge: Soft, cushioned pads integrated for sensitive skin or heavy lenses.
5) Hinge Types
- Standard Barrel Hinge: Series of barrels from frame front and temple interlocked with a screw.
- Spring Hinge: Allows temples to flex outward, providing better fit and durability.
- Hidden Hinge: Concealed within frame material for aesthetic appeal.
- Three-Barrel vs. Five-Barrel Hinges: More barrels generally mean greater strength.
6) Temple Construction
- Plastic Temples: Molded from acetate or TR-90; can be heat adjusted.
- Metal Temples: Made of stainless steel, titanium, or alloys; thin and lightweight.
- Combination Temples: Metal core with plastic covering for strength and comfort.
- Temple Tips: Often coated with silicone or acetate for comfort behind the ear.
7) Special Construction Techniques
- Memory Metal Construction: Uses nickel-titanium alloys that return to original shape after bending.
- Laser Welding: Used in titanium and stainless steel frames for strong, precise joints.
- Injection Molding: Used in plastic frames; molten plastic injected into molds to create precise shapes.
- Lamination & Layering: Decorative technique in acetate frames to combine multiple colors and textures.
8) Impact of Construction on Quality
- Monoblock plastic frames are strong but less adjustable.
- Spring hinges extend frame life and improve comfort.
- Adjustable bridges provide superior fit across varied nose shapes.
- Rimless and semi-rimless frames require strong construction to prevent loosening.
- Choice of construction affects repairability—soldering possible in metal frames, but plastics often require replacement.
9) Dispensing Relevance
- Optometrists must choose construction that suits prescription power, patient activity, and lifestyle.
- Children and sports users benefit from flexible, durable constructions (TR-90, spring hinges, cable temples).
- High-power lenses require sturdy full-rim constructions for safe mounting.
- Patients seeking aesthetics may prefer rimless or laminated designs, though with reduced durability.
Frame Selection
1) Introduction
The correct selection of a spectacle frame is as important as prescribing the right lenses. An appropriate frame ensures accurate optical performance, comfort, durability, and patient satisfaction. Frame selection must be tailored to the patient’s prescription, facial structure, lifestyle, and cosmetic preferences.
2) Frame Selection According to Prescription
- High Minus Lenses:
- Best with small, round or oval frames to reduce edge thickness.
- Full-rim frames mask edge thickness and improve aesthetics.
- High Plus Lenses:
- Small round frames minimize center thickness.
- Sturdy frames required to support heavy lenses.
- Adjustable nose pads improve weight distribution.
- Progressive/Multifocal Lenses:
- Frame must have adequate vertical depth (≥28 mm) for progressive corridor.
- Avoid very small frames that cut off reading zones.
- Prism Correction:
- Frame must allow accurate centration and adjustment.
- Large frames may cause unwanted prism if not centered correctly.
3) Frame Selection According to Face Shape
- Round Face: Angular, rectangular, or square frames to add definition.
- Square Face: Round or oval frames soften angular features.
- Oval Face: Most frame shapes suit; best to maintain natural balance.
- Heart-Shaped Face: Bottom-heavy or rimless frames balance wider forehead and narrow chin.
- Diamond Face: Cat-eye or oval frames soften sharp cheekbones.
4) Anatomical and Comfort Considerations
- Nose Fit: Adjustable nose pads for varied nasal bridges; saddle bridge for even weight distribution.
- Temple Length: Must be appropriate to avoid slipping or pressure behind ears.
- Weight Distribution: Heavy frames should spread weight across nose and ears.
- Material Selection: Hypoallergenic materials (titanium, Optyl) for sensitive skin.
- Flexibility: Memory metal or spring hinges improve durability and comfort.
5) Occupational and Lifestyle Considerations
- Industrial/Safety Users: Metal or plastic safety frames with side shields; polycarbonate lenses.
- Sports Users: Wraparound TR-90 or nylon frames with cable temples for stability.
- Office/Computer Users: Lightweight frames with adequate depth for multifocals or computer lenses.
- Children: Cable temples or flexible TR-90 frames to withstand rough use.
- Elderly: Lightweight, large enough frames for multifocal adaptation.
6) Cosmetic and Fashion Considerations
- Color Selection: Should match or complement skin tone and personality.
- Frame Shape: Enhances facial aesthetics; cat-eye for fashion, aviator for professional look.
- Thickness Management: Choice of full-rim frame conceals thick lens edges.
- Minimalist Styles: Rimless and semi-rimless frames preferred by patients seeking subtle appearance.
7) Special Considerations for Children
- Frames must be lightweight, durable, flexible.
- Cable temples ensure spectacles stay in place during activity.
- Impact-resistant lenses (polycarbonate/Trivex) are mandatory.
- Bright colors may increase acceptance and compliance.
8) Dispensing Importance
- Proper frame selection ensures optimal optical performance and reduces adaptation problems.
- Comfortable frames encourage long-term wear compliance.
- Matching frame size with prescription reduces cosmetic issues like lens thickness.
- Correct occupational frame selection improves visual efficiency and safety.
Frame Measurements (Boxing and Datum Systems)
1) Introduction
Accurate frame measurements are essential to ensure that spectacle lenses are cut, edged, and mounted correctly. Over time, several systems of frame measurement were used, but the Datum system and the Boxing system are the most recognized. Today, the Boxing system is the international standard recommended by the ISO and ANSI.
2) Need for Standardized Frame Measurements
- Ensures lenses are cut to the correct size and shape.
- Prevents decentration errors that lead to prism imbalance.
- Helps manufacturers, laboratories, and optometrists communicate using a common standard.
- Improves cosmetic appearance and patient comfort by optimizing lens thickness.
3) Datum System of Frame Measurement
The Datum system was an older method, where a horizontal line called the Datum line passes through the midpoint of the lens aperture. Measurements are taken relative to this line.
- Datum Line: A horizontal line drawn through the midpoint of the vertical dimension of the lens aperture.
- Horizontal Midline Measurement: Lens width is measured along the datum line, passing through the geometric center of the lens aperture.
- Vertical Measurement: Lens height measured at the midpoint perpendicular to the datum line.
- Datum Center: The intersection of the horizontal datum line and vertical bisector; represents the geometric center of the lens.
- Bridge Size: Distance between the two datum centers of right and left lenses.
Example: In the datum system, a frame might be measured as “50/18”, meaning horizontal lens width = 50 mm, bridge width = 18 mm.
3.1) Limitations of the Datum System
- Assumes that all lens shapes are symmetrical and rectangular in orientation.
- Inaccurate for modern frame shapes such as oval, aviator, or geometric designs.
- Does not provide effective diameter (ED), which is critical for calculating minimum blank size.
- Gradually phased out in favor of the Boxing system, which is more accurate and standardized.
4) Boxing System of Frame Measurement
The Boxing system is now the universally accepted method. In this system, a rectangle (“box”) is drawn around the lens shape, just touching the furthest edges.
The Boxing system is the current international standard (ANSI/ISO) for frame measurement. In this method, the lens aperture is enclosed within the smallest possible rectangle (“box”) that just touches the furthest edges of the shape.
- A Measurement (Lens Width): Horizontal distance of the box around one lens.
- B Measurement (Lens Height): Vertical distance of the box.
- DBL (Distance Between Lenses): The horizontal distance between the two closest edges of the lenses (bridge size).
- Geometric Center: Intersection of the box diagonals.
- Frame PD: Distance between geometric centers of right and left lenses.
- ED (Effective Diameter): Twice the distance from the geometric center to the furthest edge of the lens; used to calculate minimum blank size.
Example: A frame labeled 52 □ 18 means: A = 52 mm, DBL = 18 mm.
5) Key Terminology in the Boxing System
- Frame Size: Written as A □ DBL (e.g., 52 □ 18).
- Lens Size (A): Horizontal box dimension of a single lens.
- Lens Height (B): Vertical box dimension; important for bifocal/progressive lenses.
- Effective Diameter (ED): The minimum blank size needed for proper lens edging.
- Frame PD: The distance between the centers of the right and left lens boxes.
6) Advantages of the Boxing System
- Adopted as the global standard (ANSI Z80, ISO 8624).
- Works for all frame shapes including round, oval, and irregular forms.
- Allows accurate calculation of blank size using ED.
- Reduces errors in centration and decentration calculations.
- Compatible with modern computerized lens edging equipment.
7) Relevance in Optical Dispensing
- Accurate frame measurements prevent lens wastage during edging.
- Correct ED ensures proper ordering of blanks, especially in high prescriptions.
- Important for progressive lenses that require minimum B measurement.
- Frame PD compared with patient’s PD helps calculate required decentration.
- Enhances cosmetic results by minimizing unnecessary lens thickness.
8) Comparison of Datum vs Boxing
| Aspect | Datum System | Boxing System |
|---|---|---|
| Reference Line | Horizontal datum line through lens midpoint | Rectangle enclosing entire lens shape |
| Geometric Center | Intersection of datum line & vertical bisector | Intersection of box diagonals |
| Measurements | Lens width & height along datum line | A (width), B (height), DBL, ED, frame PD |
| Accuracy | Less accurate for irregular lens shapes | Highly accurate for all frame shapes |
| Usage | Older system, now rarely used | International standard (ANSI/ISO) |
Size, Shape, Mounting, and Field of View of Ophthalmic Lenses
1) Introduction
The frame size, shape, and mounting directly influence the final appearance, weight, thickness, and functional field of vision of spectacles. These factors are especially critical in patients with high prescriptions, progressive lenses, or special occupational needs. An optometrist must balance these aspects to provide both optimal optics and cosmetic satisfaction.
2) Effect of Frame Size
- Large Frames:
- Provide a wider field of view, especially useful for progressive lenses.
- Increase lens thickness and weight, particularly in high prescriptions.
- Lead to more noticeable edge thickness in minus lenses and center thickness in plus lenses.
- Small Frames:
- Reduce lens thickness, making spectacles lighter and more cosmetically appealing.
- May restrict vertical space, limiting suitability for bifocals or progressives.
- Offer better centration for high prescriptions, reducing decentration and prism error.
- Rule of Thumb: Small, round frames are best for high prescriptions to minimize thickness and aberrations.
3) Effect of Frame Shape
- Round/Oval Frames: Symmetrical, reduce edge thickness in minus lenses and center thickness in plus lenses. Good for high powers.
- Rectangular/Square Frames: Increase lens width, often resulting in thicker edges in minus prescriptions.
- Aviator (teardrop) Frames: Large lower portion may cut into progressive reading areas; increase lens blank requirement.
- Cat-Eye Frames: Angled design may raise optical center in the periphery; chosen mainly for cosmetic appeal.
- Geometric/Irregular Frames: May increase effective diameter (ED), leading to thicker lenses and higher blank costs.
4) Mounting Types of Lenses
- Full-Rim Mounting: Lenses fully enclosed by metal or plastic rim.
- Provides strength and security.
- Conceals lens edge thickness (useful for high minus lenses).
- Semi-Rimless Mounting (Supra): Frame covers only part of lens (usually top); lower edge supported by nylon cord.
- Lighter and cosmetically attractive.
- Exposes edge thickness in high prescriptions.
- Rimless Mounting: Lenses drilled and mounted with screws or bushings.
- Very lightweight and minimalistic.
- Require impact-resistant materials (polycarbonate, Trivex).
- Not ideal for very high prescriptions due to edge fragility.
- Three-Piece Mounting: Bridge and two temples attached directly to lens with screws.
5) Field of View Considerations
- Large Frames: Provide wide field but may introduce peripheral aberrations if not well centered.
- Small Frames: Limit peripheral vision, especially problematic for progressive lens wearers.
- Mounting Influence:
- Full-rim frames may slightly reduce apparent field due to thick rims.
- Rimless frames maximize apparent field of view by eliminating visual obstruction from eyewires.
- Progressive/Bifocals: Require adequate vertical space for full reading and intermediate zones.
6) Cosmetic and Comfort Factors
- Small frames minimize lens thickness and magnification/minification effects, improving cosmetics.
- Frame shape influences overall facial appearance; matching frame shape to face contour improves acceptance.
- Lightweight rimless and semi-rimless frames are often preferred for cosmetic reasons.
- Mounting type affects overall weight and balance; rimless frames reduce weight but need sturdier lens material.
7) Clinical and Dispensing Relevance
- High prescriptions require small, round full-rim frames to reduce thickness and aberrations.
- Progressive and bifocal lenses need adequate vertical depth for proper corridor and segment placement.
- Occupational spectacles (e.g., for computer users) may need larger rectangular frames to enhance intermediate vision.
- Mounting choice must balance cosmetic preference with lens strength and durability.
