Orthokeratology in low myopia. Part 2: corneal topographic changes and safety over 100 days.
OBJECTIVE
Modern orthokeratology (ortho-k), using reverse geometry lens designs, is being widely used for myopia reduction world-wide but there has been no well-controlled clinical trial of this procedure. This study reports on the associated corneal changes and short-term safety of an orthokeratology procedure using the OK-74 lens design (known as OK704 in the UK).


METHODS
We carried out a 100-day, controlled, randomised clinical trial in which 14 subjects underwent ortho-k and a further 14 were fitted with alignment fit contact lenses.


RESULTS
Central corneal flattening and peripheral corneal steepening occurred and myopia reduction was explained by the flattening of the central 2 mm of the cornea. The overall ocular health effects were similar in conventional and OK-74 lens wear.


CONCLUSIONS
Corneal sphericalisation occurred. Daily wear of OK-74 lens and the conventionally-designed lens were equally safe over the 100-day period investigated. Further work is needed to evaluate the long term safety of ortho-k.
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Edwards
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