Ask The Doctor
IMPLANTABLE TELESCOPES, MICROSCOPES, AND AMD

Here, we offer industry experts' answers to low vision-related questions posed to the editors of Eyecare Business.

IMPLANTABLE TELESCOPES
Q There has been a lot of publicity surrounding the development of an implantable telescope for patients with AMD and cataract. What are the clinical results to date and what initiatives are underway?

A There is a lot of work being done in this arena which is exciting and promising. At least one trial has gone into its second phase, with the hope that mini-telescopes with wide-angle ability will offer improvements over phase one. One such study is a multi-center phase II/III that implants a 3.0X or 2.0X miniature telescope in one eye. This eye provides central vision, while the other non-implanted eye provides peripheral vision.

What's important to remember about this procedure is that the post-op training is crucial. For patients, learning how to rehabilitate and acclimate to using this technology is key. A highly motivated patient is a must.

I always present all the options to each patient--bioptics, microscopes, telescopes, and implantable telescopes--and liken the implantable telescope option to hip surgery. After hip replacement surgery, patients need to use the new hip properly with physical therapy and other training methods. The same is true with implantable telescope surgery.

This surgery is not for everyone, nor is it for every low vision condition. Implantable telescopes will only work with dry, not wet, macular degeneration or Stargardt's disease.

There is a lot of work to be done which may comprise at least a year or more of continuing studies, but a lot of the initial work has been very promising.

-- Ana Perez, OD, associate professor, University of Houston, and director of low vision, Baylor College of Medicine, Houston, Texas

BINOCULAR CORRECTIONS
Q When should I prescribe binocular corrections for patients needing a microscope or near reading glasses?

A A binocular near correction can be prescribed as a bifocal, half-eye, or full-diameter lens system up to a +12.00D add power (over the distance Rx), but practically, a +10.00D add power seems to be the functional limit for most patients.

The primary reason to consider a binocular Rx in this power range is that the task may warrant binocularity, or the patient might request it, thinking that this will give better sight.

There may be some benefit to binocularity; however, there may be physiological reasons why it may be contraindicated.

Considerations for this type of near Rx should be the similarity or difference of both central and peripheral sight between the two eyes--including distortion, contrast, binocular stability, and eye dominance.

Because these systems will have a close working distance, the near point of convergence should be considered.

The appropriate distance between lenses should be calculated, although standard systems with pre-calculated base in prism can be used.

Finally, the patient should have the opportunity to work with the lenses, either in a trial frame or as a loaner system, to confirm that the binocular Rx is comfortable and provides the desired result.

-- Paul Freeman, OD, Allegheny General Hospital, Pittsburgh

HIGH-INDEX LENSES
Q Is using a high-index lens for microscopes of any value for the low vision patient?

AHigh-index reduces lens weight and thickness in high-plus power microscopes, and reduces the appearance of "big eyes," or magnification, just as it does in spectacle lenses. The advantages are purely from a cosmetic and weight standpoint, not from a visual acuity standpoint, as visual clarity is the same through a standard index as a high-index microscope.

Less weight may mean enhanced wearing comfort for some patients. Other patients may not experience a significant difference in wearing comfort to justify the cost differential. High-index may reduce lens thickness and enhance eye appearance, but it also increases the cost.

Each patient and each situation must be evaluated to determine the best solution considering visual acuity, wearing comfort, and cosmetic value.

If possible, devices should be tested or loaned so patients can experience the difference in high-index as compared to standard index firsthand.

-- James Nedrow, OD, Oculi Vision Rehabilitation, Lincoln, Neb.