Myopia correction takes a new shape: here are some of the latest designs and fitting pearls for corneal reshaping, plus a look at who the best candidates are for this modality

Corneal reshaping is a rapidly progressing and increasingly popular modality worldwide and has demonstrated success in myopia reduction with patients as young as age 7. (1-3)

There have been some reports of adverse reactions in patients during corneal reshaping (see "Corneal Reshaping and Microbial Keratitis," page 60). (4-11) But, with careful patient education and compliance, these complications are avoidable.

Here, we'll look at some of the latest designs and fitting pearls for corneal reshaping and who the best candidates are for this modality.

Who's a Candidate?

Most patients with -4.50D or less myopia are suitable candidates for corneal reshaping. Patients often experience a myopic reduction of 1.00D to 2.00D the first night. (12)

Many O.D.s limit eligible patients to the non-presbyopia age group, although monovision corneal reshaping (i.e., under-correcting one eye) is occasionally prescribed. Presbyopic corneal reshaping designs show promise, according to recent research. (13)

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If you've just introduced corneal reshaping into your practice, you might want to start with the -1.00D to -2.00D myopic patient to gain confidence with this process. Also, start with young adults who are either non-contact lens or soft contact lens wearers and have no more than -1.50D of corneal cylinder (preferably not limbus-to-limbus). Corneal reshaping may result in a 50% reduction of central corneal toricity. (14) Patients with against-the-rule or irregular astigmatism are not good candidates. (15)

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You can prescreen potential patients by phone. When patients schedule an appointment, you (or your staff) can ask them about any known refractive error and current lens wear. Make sure that patients who are good candidates for corneal reshaping understand that this is a temporary process that requires retainer lens wear at night and compliance with the wearing schedule and care regimen.

Spherical gas permeable (GP) lens wearers must discontinue lens wear for at least four weeks before being fit with ortho-K lenses. Expect more lens exchanges and variable topography maps with these patients, even if they discontinue GP lens wear as recommended. (16)

Fitting and Follow-up

The lens designs we commonly use for ortho-K have at least four zones: the base curve; the secondary, or reverse, curve, which is often 3.00D to 5.00D steeper than the base curve; an intermediate alignment or fitting curve, which parallels the mid-peripheral cornea; and a peripheral curve radius, which is often slightly steeper than conventional designs, resulting in less peripheral clearance. (17) The optical zone is often 6mm (it will be less in certain designs for higher refractive errors). Regardless of which design you select, fitting and follow-up care must be consistent.

Some designs use the "Jessen factor," which is based simply upon lacrimal lens power changes. For example, if the patient's spherical refractive error is -3.00D, you would select a base curve radius approximately 3.50D to 3.75D flatter than "K" to result in a refractive error of +0.50D to +0.75D. This is an ideal power to allow for regression of refractive error during the day.