5.3.3 Understands the techniques used in the fitting of complex contact lenses and advises patients requiring complex correction

What is aphakia?

Absence of the crystalline lens, typically post-cataract surgery without IOL implantation or following trauma.

What are the advantages and fitting characteristics of RGP lenses for aphakia?

RGPs:

• Better optical quality

• Reduced aberrations

Fitting characteristics

• Larger diameters improve stability

• Aim for slight apical clearance

What are the advantages and fitting characteristics of scleral lenses for aphakic patients?

Scleral lenses:

• Improved comfort

• Stable optics

• Minimal lens movement

Fitting characteristics

• Vault entire cornea

• Assess central and limbal clearance using fluorescein or OCT

• Allow for lens settling

What patient advice should be given to aphakic contact lens wearers?

• Expect image magnification

• Adaptation period likely with RGPs

• Importance of regular aftercare due to hypoxia risk

• Emphasise careful handling (high lens cost)

• Discuss realistic visual expectations

What is high ametropia?

Refractive errors typically greater than ±6.00 D, including high myopia or hyperopia.

What are the advantages and disadvantages of soft lenses, RGPs and scleral lenses for high ametropia?

Soft lenses:

• Reduced oxygen transmissibility in high powers

• Edge thickness issues

RGPs:

• Better visual acuity

• Less minification/magnification

Scleral lenses:

• Excellent centration and stability

• High oxygen permeability materials needed

What should be considered when selecting contact lenses for patients with high ametropia?

• MUST SELECT LENSES WITH HIGH Dk/t

• Improved vision compared to spectacles

What is keratoconus?

A progressive, non-inflammatory ectasia causing corneal thinning and irregular astigmatism.

- Need to neutralise irregular astigmatism.

What are the contact lens options and fitting characteristics for keratoconus?

RGPs:

- Apical clearance or light touch

Scleral lenses:

• Vault irregular cornea completely

• Excellent comfort and stability

What patient advice should be given to patients with keratoconus?

• Explain progressive nature of condition

• Lenses improve vision but do not halt progression

• Importance of regular follow-up

• Discuss cross-linking if appropriate

What are the causes or types of post-surgical / post-refractive surgery corneal changes?

• Post-keratoplasty (PK, DALK)

• Post-cataract surgery

• Post-trauma

• LASIK

• PRK

• Radial keratotomy (RK)

What types of contact lenses are available for patients with post-surgical / post-refractive surgery corneas?

• RGP lenses

• Reverse-geometry RGPs

  • Larger base curve

  • Steeper secondary curves

• Hybrid lenses

• Scleral lenses

• Custom soft lenses

What are the fitting characteristics to consider for post-surgical / post-refractive surgery corneas?

• Oblate corneal shape (flat centre, steeper periphery)

• Decentration risk

• Reduced corneal sensitivity

What patient advice should be given following surgery or refractive surgery when wearing contact lenses?

• Visual fluctuations common

• Dry eye symptoms common post-surgery