This column will take a different road to helping presbyopes who do not want to wear glasses: I will talk about orthokeratology (ortho-k) and its role in presbyopia correction. Ortho-k has been around for roughly 30 years, and lately it has enjoyed renewed interest. While I prefer for patients to wear their lenses while they are awake, some practitioners employ ortho-k to give patients freedom from contact lenses during the day. This technique can be very helpful for patients who have dry eye issues related to contact lens wear.
In ortho-k, a reverse geometry GP contact lens is worn during sleep. The idea is to change the corneal curvature and therefore correct patients’ refractive error overnight. When the lenses are removed in the morning, vision is generally improved. The effect usually lasts for the entire day.
Ortho-k initially targeted patients who have low degrees of myopia. Over time, the design of these lenses has evolved to the point at which larger degrees of myopia, as well as astigmatism, can be treated.
Correcting for Presbyopia
While an off-label use, there are a number of ways to achieve a presbyopic correction using ortho-k. For myopic patients, the first thought is often monovision. Here, the dominant eye would be fully corrected for distance, and the nondominant eye would be corrected for near. For lower degrees of myopia, it may be possible to correct only the dominant eye. The nondominant eye would naturally be set for the average reading or computer distance. Conversely, for higher powers, the nondominant eye would be corrected for a targeted distance.
According to Cary Herzberg, OD (personal communication), ortho-k is being used successfully in a multifocal fashion. “In fact, it is one of the fastest growing areas in corneal reshaping,” he states. Further, “anything you can do with a soft multifocal contact lens can also be done with ortho-k.” Apparently, because of the nature of molding the cornea in the first place, an aspheric zone develops at the edge of the optic zone. In progressive molding, the pupil zone is reduced, and the aspheric zone is enhanced. Thus, the multifocal effect is achieved.
What about emmetropic presbyopes? These individuals, who have enjoyed good vision at all distances until this point, are frequently distressed to be reliant on reading glasses. There is an ortho-k option for them as well. Gifford and Swarbrick (2013) showed that it was possible to create a monovision correction in such patients. They used a hyperopic ortho-k lens on the nondominant eye to induce a myopic shift; this was accomplished by inducing central steepening and paracentral flattening with the overnight lens. According to their study, patients had functional near vision throughout the day, with no loss in binocular distance vision.
An Option to Consider
Certification is required with ortho-k. There is a learning curve, and the presbyopia technique would likely be more involved. But, it is worth discussing this option with patients if you feel comfortable with ortho-k. As always, realistic expectations, for both patient and practitioner, are a requirement. And, as with other presbyopic correction options, patience is needed to reach the successful end point. CLS
For references, please visit www.clspectrum.com/references and click on document #261.