The Politzer Telescope design series is fast becoming an integral part of low vision practice as patients are using the telescopes and enjoying them.
NEW SPECTACLE TELESCOPIC DESIGN
HOLDS PROMISE
FOR LOW VISION PATIENTS
BY
MICHAEL R. POLITZER, O.D., F.A.A.O., F.C.O.V.D.
Many innovations in the field of low vision rehabilitation have provided patients with optical aids that meet their need for independence. These low vision aids fall into various categories that enhance patient’s activities of daily living requirements such as driving and mobility, reading, interacting with other people or caring for themselves.
The partially sighted are often confused, worried and frustrated. I am frequently asked, “Doctor; all I want is a pair of glasses that I can see through”. They realize that their eyes are changing; possibly getting worse and their desire is to “go back to the way it used to be”. In reality, we cannot make patients just a "pair of glasses" to meet all of their needs.
As I pondered this situation, I began to take an inventory of what low vision aids were available and which ones I prescribed the most. I studied which of the patient needs were or were not being met, how easily and quickly patients adapted to the aids and how regularly they were being used.
My conclusion was that patients with central vision pathology who required improved distant, intermediate or near vision clarity, were having great difficulty in adapting to their aids and ultimately not using them. It was more difficult for these patients to find the exit pupil and keep it aligned while using the telescope or telemicroscope.
Low vision patients are expressing their need for more independence. They are healthier and living longer. They are better educated and more savvy. They want to be able to drive, access the Internet, recognize objects and people’s faces in various social settings, read, play cards and pay their bills. In essence, they want to maintain an independent lifestyle and they want what they want and they want it now. Unfortunately, what they want is currently not available
Telescopes and telemicroscopes that are currently available characteristically have small exit pupils. With a large objective lens and small ocular lens the field of view is reduced. Patients report that those systems, which use a frosted housing unit, tend to increase internal light scatter and create glare. The systems that use a black housing unit reduce internal light scatter with glare and enhance image quality. However, this type of housing causes objects being viewed to appear darker. Also, it is cosmetically objectionable.
The entrance pupil of a telescope is the objective lens and the image of the objective lens formed by the eye piece lens is the exit pupil. The size of the eye piece lens (and therefore the exit pupil) traditionally has been limited by the size of the objective lens and the power of the telescope. The diameter of the exit pupil is therefore determined by dividing the diameter of the objective lens by the magnification power of the telescope.
Eg. A 2.0X telescope with a 40mm objective lens would then have an eye piece lens and exit pupil diameter of 20mm.
The field of view of a telescope is limited by its exit pupil and the image brightness of the telescope is determined by the size of the exit pupil relative to the size of the pupil of the eye. Tradition has established that enlarging the exit pupil beyond the size of the eyes entrance pupil will have no effect on increasing the telescopes field of view or its image brightness.
However, Marvin Hutt, Ph.D., Senior Adjunct Associate Professor of Optical Engineering at the Stevens Institute of Technology, New Jersey, states; "Design of low powered telescopes to maximize the ease of use regarding less long term strain on the eye requires that the eye swim in an enlarged device exit pupil. While the classical optical design calls for a static eye pupil with an iris diameter set by ambient lighting, the philosophical impact of the device exit pupil being close to the iris diameter of the eye is a tunnel appearance of the field. This leads to long term eyestrain and a physiological reduction in the apparent view through the system. In wearing these devices the patient will almost invariably prefer the system where the eye swims in an enlarged exit pupil even though from a non-moving eye model, the over sized device exit pupil is not necessary.
The challenge, therefore, was to find a telescope that would meet the following requirements and conditions so that patient use and acceptance would increase:
- Easy exit pupil accessibility
- Brighter image quality
- Larger field of view
- Less distortion for a more natural appearance of objects viewed
- Cosmetically appealing
I began to experiment with various optical designs. The one that met most of the above mentioned criterion became a modification of the Designs for Vision 1.7X full field telescope.
We were able to achieve a larger exit pupil, 31% INCREASE, by making the objective and eye piece lens the same diameter. Improved light gathering and glare reduction were achieved with a light beige housing.
The POLITZER TELESCOPE (PT) design series was manufactured by Designs for Vision and a study, utilizing clinical patient populations from ten (10) domestic and international sites began. The purpose of the study was to determine patient objective and subjective responses to the PT design series.
The results indicate that the (PT) design series meets the requirements established in this study. The new design series has created a new set of spectacle telescopes that are easier and more effective for the patient to use.
Despite traditional optical design concepts, enlarging the exit pupil does impact ease of use, field size and image brightness. With a larger exit pupil the fitting is easy and very little training is required to teach the patient how to view through the system.
Metal frames with a frame pd close to the patients pd is utilized. Adjustable pads allow for the lens system to be properly aligned vertically and horizontally and placed close to the patient’s eyes (8-10mm vertex distance) for enhanced ease of use. And, the PT design series has now been expanded to include 2.2, 3.3 and 4.0X bioptic micro-spiral models with plus lens, prism and split field caps available for all full field and bioptic model one designs.
The (PT) design series is fast becoming an integral part of low vision practice. Patients are using the (PT) and enjoying it. They continue to find new and innovative uses for this aid and do not object to the issues of size, weight or appearance. The major issue of cost has been resolved with the use of flexible funding sources that provide interest-free financing to qualified patients.
Should you have any questions or wish to schedule an evaluation to determine if you are a candidate for the new Politzer Telescope please contact Dr. Politzer at 615-604-2949 or www.drpolitzer.com