Why can't children wear standard CR-39 plastic lenses?

While CR-39 meets basic FDA impact resistance requirements, it does not provide the level of protection that active children need. Polycarbonate is 10-20 times more impact resistant than CR-39, and Trivex offers comparable protection. Given that children are physically active, prone to falls, and less careful with their eyewear, the stronger materials are strongly recommended for safety.

At what age can a child switch from cable temples to skull temples?

There is no strict age cutoff. The decision depends on the child's activity level, responsibility, and whether consistent wear is medically necessary. Many children transition to skull temples around age 4-6 when they can manage putting glasses on and off independently. Children being treated for amblyopia or other conditions requiring strict compliance may benefit from cable temples longer.

How do I measure PD on a young child who will not sit still?

Use creative fixation targets like stickers, small toys, or a phone screen with a video to hold the child's attention at the correct distance. Measure quickly during moments of attention. For very young children, some practitioners measure PD from photographs taken at a known distance. Digital measuring apps can also help. Monocular PDs are especially important for children since their facial asymmetry can be significant.

Children's Eyewear Dispensing: Materials, Frames, and Safety

Why Children's Dispensing Is Different

Dispensing eyewear for children requires a different approach than adult dispensing. Children are physically active, less careful with their belongings, and still growing. Their eyewear must withstand rough handling, provide maximum eye protection, and fit comfortably on smaller facial features that change as the child grows.

Beyond durability, correct fitting is essential for visual development. A child with poorly fitting glasses may avoid wearing them, which can have serious consequences for conditions like amblyopia (lazy eye) where consistent lens wear is part of the treatment.

Lens Material Requirements

For children, impact-resistant lens materials are not optional. The FDA requires that all spectacle lenses be impact-resistant, but for children, the strongest materials are strongly recommended:

Polycarbonate

Polycarbonate (index 1.586) is the most commonly recommended material for children's lenses. It offers:

Extremely high impact resistance (10-20 times more impact resistant than CR-39)
Built-in UV protection (blocks 100% of UVA and UVB)
Lightweight (specific gravity of 1.20, lighter than most other materials)
Thin profile for a given prescription

The main drawback is its relatively low Abbe value (30), which means more chromatic aberration. However, children rarely notice or complain about this.

Trivex

Trivex (index 1.53) is an excellent alternative that provides:

Impact resistance comparable to polycarbonate
Superior optical clarity with a higher Abbe value (45)
The lightest lens material available (specific gravity of 1.11)
Built-in UV protection

Trivex lenses are slightly thicker than polycarbonate for the same prescription because of the lower index, but the optical quality is noticeably better.

Standard plastic (CR-39) and glass should be avoided for children. While they may meet FDA impact resistance requirements, they do not provide the level of protection that active children need. Polycarbonate or Trivex should be the default recommendation.

Frame Selection for Children

Children's frames must be durable, comfortable, and properly sized:

Frame Sizing

The frame should position the child's eyes near the horizontal and vertical center of the lens opening. Key measurements:

Bridge width: Must match the child's nose width. Children typically have flatter, wider nasal bridges, especially younger children.
Eye size: Should be proportional to the child's face. Oversized frames look awkward and make lenses unnecessarily heavy.
Temple length: Must reach behind the ears with proper bend point placement.

Frame Materials

Flexible plastic (rubber-like materials): Best for infants and toddlers. These frames bend without breaking and snap back to shape.
Acetate/zyl: Good for older children. Durable, available in many colors and styles that appeal to kids.
Memory metal: Titanium-based frames that return to shape after bending. Excellent durability but more expensive.
Avoid rimless/semi-rimless: These expose the lens edges to damage and provide less structural protection.

Cable Temples

Cable temples wrap fully around the ear rather than simply curving behind it. They are strongly recommended for:

Infants and toddlers: Who cannot keep standard temples in place
Very active children: Who play sports or roughhouse frequently
Children with therapeutic prescriptions: Where consistent wear is medically necessary (amblyopia treatment, high hyperopia)

Cable temples provide significantly more security than skull temples but can be harder for very young children to put on and take off independently.

For children who resist wearing glasses, involve them in choosing the frame color and style. A child who picks their own "cool" glasses is far more likely to wear them consistently than a child who has frames chosen for them by a parent.

Fitting Considerations

Bridge Fitting

Young children often have flat, undeveloped nasal bridges. Standard adult nose pads and keyhole bridges may not work. Options include:

Saddle bridges that rest across the entire nose
Low-profile bridges designed for flat noses
Adjustable silicone nose pads on flexible pad arms

Proper PD Measurement

Children's PDs are significantly smaller than adult PDs (typically 42-54mm for children ages 3-12). Use monocular PDs whenever possible since children's faces can be quite asymmetric. Getting an accurate PD measurement from a young child requires patience and sometimes creative techniques like using stickers as fixation targets.

Growth Considerations

Children's faces grow rapidly. Plan for regular frame updates:

Infants: May need new frames every 3-6 months
Toddlers: Every 6-12 months
School-age children: Annually or as needed

Selecting oversized frames so the child can "grow into them." Oversized frames sit poorly, slide down the nose, and position the optical centers incorrectly. Always fit for the child's current size and plan to replace as they grow.

Special Considerations

Sports eyewear: Polycarbonate lenses in sports-rated frames (ASTM F803 for ball sports) provide the highest level of protection during athletic activity.
Strap options: Elastic straps attached to the temples help keep glasses on during active play for young children.
Scratch-resistant coating: Essential for children's lenses. Polycarbonate is inherently soft and scratches easily without a hard coat.

Key Takeaways

Polycarbonate or Trivex are the required materials for children's lenses due to impact resistance
Frame sizing should fit the child now, not be oversized to "grow into"
Cable temples provide the best retention for infants, toddlers, and active children
Flat nasal bridges in young children require saddle bridges or specially designed pads
Use monocular PDs for children since facial asymmetry is common
Plan for regular frame replacements as the child grows