Professor Gerard Sutton, MBBS MD FRANZCO
Speaking from personal experience, I can say that presbyopia is a frustrating condition. For emmetropes especially, who have never required spectacles, the new found dependency can be very frustrating. Those patients looking at surgical options to reduce or eliminate the need for reading glasses, are faced with a myriad of choices. It is an old but true adage that in medicine, whenever there are numerous options for the treatment of a condition, you can be sure of one thing; none of them is perfect.
In my practice, based on the current evidence in the peer-reviewed literature, the only surgical options that I consider for the treatment of presbyopia are blended vision (monovision) or a Restor multifocal intraocular lens. The Kamra Inlay and Intracor femtosecond treatments are currently investigational techniques, with inadequate numbers in the peer-reviewed literature to date to warrant their general use. In my opinion their safety and efficacy have not yet been established and patients (and surgeons) should approach their use with caution.
Why risk these new unproven modalities when we have two proven and safe options? My preferred surgical option is blended vision. This is often poorly understood by patients who consider that having one eye which is better focused for distance and one for near will make the patient feel unsteady or create headache issues. Indeed a small percentage of patients (<10%) will not be suitable and that is why it is important to create the effect of the blended vision with a contact lens trial prior to any surgery. In my experience if the contact lens trial is successful the patient will be very happy with the surgical outcome. It is important not to try for too much near correction.
Finkelman et (JCRS 2009) showed that if the induced myopia was less than 1.5Dioptres there was no loss in stereoacuity or contrast senstitivity. Depending on a patient’s age this degree of anisometropia would allow good intermediate ( shopping prices, computer screens ) and adequate near vision ( newspapers, restaurant menus, mobile phones) for most activities. The compromise is that reading glasses may still be required for finer activities such as sewing and for reading in poor illumination.
In patients undergoing LASIK surgery, blended vision is the preferred presbyopic treatment option. In patients undergoing cataract or refractive lens exchange surgery, a good multifocal IOL (Restor; Alcon) is a reasonable option as well.
So how do we decide between a multifocal lens and a blended vision correction? In a recent study Zhang, Sugar and colleagues (JCRS May 2011) compared these two options. They found that for uncorrected distance and near visual acuity the two groups were identical. However for intermediate vision (computer) the blended vision group did statistically better. They also performed better in terms of their overall satisfaction score and had fewer complaints about night vision.
Other advantages of blended vision over multifocal intraocular lenses are that they are not sensitive to intraocular decentration and they do not have a negative impact in patients with macular disease. It is a fact often overlooked that in patients with a multifocal IOL, the modulation transfer function (MTF) which is an indication of how much light is getting to the retina, is reduced by up to 50%. In patients with any macular disease this can severely reduce visual function. Patients with multifocal IOLs are also very sensitive to any residual astigmatism or posterior capsular opacity. The incidence of refractive surgical touch ups and yag capsulotomies are therefore higher.
Despite these limitations, I believe that the Restor multifocal IOL is an excellent choice in patients without macular disease, who don’t spend a lot of time driving at night and who wish to achieve vision that will allow them to read comfortably without glasses.
Finally it is is essential to remember and to tell all patients, that these surgical procedures will reduce but not necessarily eliminate the need for spectacles.
Blended (mono) vision and multifocal IOLs are the safest and best options for the treatment of presbyopia. In LASIK I will use some form of blended vision in almost all presbyopes. In intraocular surgery, I give the patients an option of blended vision or a multifocal lens and customize the surgery to their visual needs and lifestyle.
So as a 48 year old Professor of Corneal & Refractive Surgery what surgery did I chose when the dreaded dependency on reading glasses became too great? Blended vision of course. I have typed this article without the need of any reading correction and next week I will go fishing and tie on my hooks without them as well.