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CASE REPORT: Significant benefits outweigh potential risks

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Lee Baumwol

 

Scleral and mini-scleral contact lenses have grown in popularity in recent years with the advent of newer lens designs and high Dk materials. Mini-scleral lenses (15-18 mm diameter) vault the cornea and rest on the anterior sclera, allowing for easier apical clearance in keratoconus compared to smaller diameter RGPs. They can provide a more stable fit in cases where it is difficult to get a smaller diameter lens to stay on the eye. Comfort can also be improved with the reduced lid interaction and clearance of the cornea.

Ms A, a 42-year-old with keratoconus, had had intracorneal rings (Kera rings) implanted in her left eye, and corneal collagen cross-linking to both eyes. With 6.50 D of astigmatism in her right eye and 8.00 D in the left, spectacle acuities were R 6/30, L 6/9. Her post-operative topography is shown in Figures 1 and 2.

CLF 11 Lee Baumwol - Pentacam _1 - Web

Figure 1. Corneal topography right eye

CLF 11 Lee Baumwol - Pentacam _2 - Web

Figure 2. Corneal topography left eye

She was initially fitted with small diameter keratoconic RGPs but an adequate fit to enable the lenses to stay on the eye was not achieved. Ms A was refitted with Capricornia Eycon mini-sclerals (16 mm diameter in Boston XO2 material), achieving visual acuities of R 6/6, L 6/7.5 and relatively good comfort. Dislodging of these larger diameter lenses was not a concern.

Scleral and mini-scleral lenses are not without complications. These lenses are about four times thicker than regular RGPs, to prevent warpage. Even with the newer high Dk materials, hypoxia can be an issue. The closed tear reservoir that results with mini-scleral is also a contributing factor here. Ms A has developed some corneal neovascularisation in her left eye towards her lower intracorneal ring that requires monitoring. She has also broken one lens, a considerable feat given the thickness of the mini-sclerals.

A great resource readily available on the internet for practitioners looking to fit scleral or mini-scleral lenses is Eef Van Der Worp’s ‘A Guide to Scleral Lens Fitting’. At the time of fitting Ms A, Capricornia was happy to lend trial sets of the Eycon mini-sclerals to optometrists for trial fitting.

Aside from irregular corneas, these lenses are also used for severe ocular surface disease although the potential risks associated with tear film stagnation, hypoxia and contact lens wear in general on a compromised cornea need to be balanced against the potential benefits of improved visual acuity and comfort.

 

References

  1. Van Der Worp E. A Guide to Scleral Lens Fitting. Scleral Lens Education Society 2010. Available from: http://commons.pacificu.edu/mono/4/.
  2. Van Der Worp E, Bornman D, Ferreira DL, Faria-Riberio M, Garcia-Porta N, Gonzalez-Meijome JM. Modern scleral lenses: A review. Contact Lens Anterior Eye 2014. Available from: http://dx.dio.org/10.1016/j.clae/2014.02.002.


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