Mastering Dispensing Competencies: A Guide for Pre-Reg Optometrists

The Role of the Dispensing Optician

If you’re ever unsure, your in-store dispensing optician is your best resource. Dispensing is their speciality, and they’re a valuable source of support as you navigate your visits. Remember, once qualified, you’ll do very little dispensing day-to-day, but a solid understanding now is essential for assessments.

High Prescriptions: Frame and Lens Advice

For patients with high prescriptions, frame choice is critical. Smaller, rounder, symmetrical frames help reduce edge thickness and improve appearance. Other key considerations:

• PD should match the BCD to reduce decentration
• Aspheric lenses can help with high plus prescriptions
• High-index materials reduce thickness and weight
• For extremely high prescriptions (e.g. -22D), lenticular lenses may be the only option

Anisometropia and Related Issues

Anisometropia occurs when there is a significant difference in refractive error between the two eyes (typically >1.5–2D). This can cause:

• Aniseikonia (different image sizes on the retina) leading to nausea, headaches, or poor stereopsis
• Unwanted prism from unequal lens powers or decentration

Solutions include: contact lenses (no prismatic effect), splitting the difference, slab-off techniques, or specialised lens designs.

Prism and Calculations

One of the most common dispensing calculations you’ll be asked about involves Prentice’s Rule:
P = C × F

• P = prism (Δ)
• C = decentration in cm
• F = lens power

For example: if PD is off by 5mm vertically and Rx is -5.00D, the induced prism is 2.5Δ base down. Practising these examples is essential.

Safety Spectacles

Safety specs are a key competency:

• Must be replaced every 2 years
• Cannot be adjusted once made — frame fit must be correct from the start
• Any damage or scratches render them unsafe
• Learn lens and frame markings, strengths (A, B, F, S), and how they are tested

Always assess occupational hazards — whether mechanical, chemical or radiation — and recommend appropriate protection.

Varifocals and Lens Designs

Know the different types of varifocals available in your practice. Freeform designs offer:

• Wider fields of view
• Reduced distortion
• Better adaptation for patients

Be prepared to explain the pros and cons of the different options available in your store.

High Refractive Errors and Lens Choices

For high prescriptions:

• Small lens sizes reduce weight and thickness
• Plastic frames disguise edge thickness better
• Crown glass (1.9) is an option but expensive
• Power rings (reflections at lens edges) can be reduced with coatings or smaller sizes

Anti-reflection coatings and photochromic lenses are also important to understand for patient recommendations.

Paediatric Dispensing

Dispensing for children under four requires:

• Small, round frames to ensure correct visual axis alignment
• Adjustable metal frames for better fit
• Frame PD close to patient PD to minimise decentration
• Side styles such as curl sides, silicone sides, or straps for stability

Low Vision Aids

Key considerations include:

• Working distance is crucial
• Know how to explain and demonstrate different aids (handheld, stand magnifiers, telescopes, electronic options)
• Understand which glasses should be worn with each type

Final Thoughts on your pre-reg competencies for dispensing

Dispensing doesn’t have to be intimidating. Focus on building a solid understanding of the basics — high prescriptions, prism calculations, frame and lens selection, and safety specs. For trickier topics, lean on your dispensing optician colleagues. With practice and familiarity, you’ll feel much more confident heading into assessments.