OD News Articles

1st October 2005

When LASIK Won’t Cut It—Options for High Myopes

by Francis Barnhart, OD Boise, ID

Counseling, expectations and surgical options for high myopes can pose challenges for ODs and surgeons. While LASIK is usually our preferred treatment, other options may be more appropriate for high myopes-especially when they have:

  • thin corneas
  • flat corneas 
  • large pupils
Other refractive surgery options include:
  • Photorefractive keratectomy (PRK)
    Range: +3.00 to -16.00 

    Astigmatism: can treat up to -6.00
  • Implantable contact lens (ICL)

    Range: from -5.00 to -20.00 

    Astigmatism: must have no more than -2.00 but can be treated with LASIK or PRK
  • Refractive lens exchange (RLE)
    Range: almost no limit
    Astigmatism: must have no more than -2.00 but can be treated with LASIK or PRK
    
Presbyopia: multifocal and accommodating lenses are available
Counseling High Myopes

Pre-op counseling is important for all refractive surgery patients, but high myopes require additional discussion concerning:

  • increased risk of regression with laser vision correction
  • increased risk of full treatment not being achieved with the first surgery
  • enhancement options limited by corneal thickness
  • the potential for reduced BCVA

Fortunately, good education and a conservative approach to surgery results in the vast majority of patients achieving their expectations.

Options to Consider

RLE is often the best option for presbyopic patients. But PRK and ICLs should be considered for younger eyes when corneas are too thin or flat, or pupils are too large for LASIK.

When corneas are thin:
To avoid weakening corneas, LASIK is not advisable when pachymetry measurements are less than 500 microns. But PRK and ICLs are alternatives. Since there is no flap with PRK, less corneal thickness is required for the same amount of treatment. ICLs are a safe option as they do not affect corneal tissue.

When corneas are flat:
Patients with flat corneas may be good candidates for ICLs. Normal corneas are prolate in shape—being steeper centrally and flatter peripherally. LASIK and PRK performed on high myopes will significantly flatten the central cornea and may result in glare or foggy vision that gets worse in reduced light. In extreme cases the prolate shape may become oblate with the central cornea flatter than the peripheral. Wavefront analysis has helped us understand the importance of maintaining prolate corneas. While laser vision correction advances allow us to do a better job of preserving prolate corneas, treatments for high myopia can require such extreme changes in corneal curvature that the risk of unwanted aberrations is high. ICLs may be a better option.

When pupils are large:
PRK may be the best option for patients with large pupils. With laser vision correction, these folks are at risk of annoying glare and night vision problems and will generally benefit from the larger treatment zones of PRK. Because the amount of tissue removed is directly related to treatment zone size, larger treatment areas result in deeper ablations. When high myopia is combined with large pupils, there may not be enough corneal thickness for LASIK-even when the cornea is thicker than 500 microns. Because no flap is required with PRK, less corneal depth is required and larger treatment zones are possible. ICLs are not a good option for patients with large pupils. Current lenses are only 6mm and will cause disturbing glare and halos.

More About ICLs
  • A high range of myopic powers is available.
  • Hyperopic powers should be available within a year or so.
  • Insertion is familiar to experienced cataract surgeons.
  • Lenses may be removed or repositioned if needed.
  • Astigmatism correcting ICLs are expected in the future.
  • Corneal curvature remains unchanged so if cataract surgery is ever required, calculations to select implant powers should be easy and accurate.
  • An iridotomy is generally performed before insertion to insure adequate fluid flow.
  • There is a risk of endothelial loss. If it becomes excessive, the ICL must be removed.
Conclusion

Successful refractive surgery requires careful patient selection, counseling, appropriate procedure, and follow-up care. While most patients are well served with LASIK, consider other options for high myopes. Click here to request or download patient education materials we have produced on PRK, ICLs and RLE.