A scleral contact lens, extended onto the white of the eye

When contact lens fitting was in its infant years, the only material available was polymethyl methacrylate (PMMA), a type of thermoplastic which, although it had good optical properties and could be machined easily, did not allow any oxygen to pass through the lens material. A scleral contact lens is a large contact lens which vaults the cornea and rests on the sclera (white of the eye). The space between the lens and the cornea would be filled with tear fluid. This design always held promise to optically correct irregular corneas. The problem with scleral lenses was the lack of oxygen reaching the cornea. The cornea has no blood vessels to carry oxygen, instead, it gets its supply from the atmosphere.
Smaller corneal hard lenses, which floated on the tear layer, was the order of the day, but had serious shortcomings when it came to highly irregular corneas.

For many years there existed a large pool of patients suffering from irregular corneas (common cause being keratoconus), for whom there was no remedy. This frustrated optometrists and patients alike. For some with advanced keratoconus, the only solution was a corneal transplant, but this excluded many because of a shortage of donor corneas, cost and corneas that were too thin.

Comparison between a corneal and a scleral contact lens

During the last decade or so, the scleral lens has made a dramatic comeback. This is mainly so because of the advent of more sophisticated gas permeable materials, which allow adequate quantities of oxygen to pass through the lens to reach the cornea. Modern-day scleral lenses can provide spectacular outcomes for people who simply had no answer to their visual issues in the past. Because the lens vaults the cornea and the irregular corneal surface is neutralised by the tears, which acts like an optical lens, vision can be restored dramatically if not to normal. This has been a heaven-sent remedy for many.

Indications for Scleral Lenses

  • Keratoconus.
  • Trauma and irregular astigmatism.
  • Post-surgical.
  • Post-refractive surgery.
  • Corneal degenerations and dystrophies.
  • Dry eye management.
  • High Refractive Errors.
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