Marc J. Gannon, OD, FAAO, FIALVS with Richard J. Shuldiner, OD, FAAO, FIALVS, Chief Clinical Editor
Miguel is a 14-year-old, “illegal alien” young man who is living at the Refugee Resettlement Facility in Homestead, Florida. Because of apparent vision issues, approval was given for two case workers to take him to a local physician to evaluate his vision status. The local physician recommended a referral to Dr. Rashid Taher and Dr. Diana Shechtman, of Retina Macula Specialists of Miami.
Approval was given for two case workers to transport him to their offices for evaluation. The resulting evaluation confirmed his diagnosis of Retinitis Pigmentosa (RP). The retina specialists recommended a referral to a Low Vision Optometrist.
Approval was given for two case workers to transport him to my office, Dr. Gannon, in Ft. Lauderdale for a low vision evaluation and treatment.
This case describes a 14-year-old RP patient who is having increased difficulty reading, writing, working with his hands, seeing faces, sighting signs when he is walking, and identifying obstacles in his path when he is ambulating. His goals include improving his function in all of these areas.
This article will address a potential avenue of management and treatment to enable him to meet these goals and have the best possible visually functional outcome.
This case also describes the humane way the United States government treated this “illegal alien” who came to this country for a better life.
Retinitis Pigmentosa is a progressive condition resulting in a loss of vision. It may be associated with a number of systemic conditions or syndromes or may be primary in nature. The rod-cone presentation is the more classic with a loss of peripheral vision to a resultant ring scotoma or tunnel vision, and a decrease in night vision (nyctalopia). The central vision is frequently spared and many of these patients present with excellent central acuity, but with a compromised field of vision.
Retinitis Pigmentosa (RP) should be regarded as the description for many different dystrophies and degenerations of the photoreceptors and the retinal pigment epithelium (RPE). Most of these conditions are genetic in nature and almost all are progressive. Progressive deterioration of the RPE and/or the photoreceptors defines a myriad of conditions which include several named dystrophies. The photoreceptors that are affected may be rods or cones, and they may be affected centrally or peripherally, although the classical presentation is peripheral rods.
It hasn’t been established if the loss of the photoreceptors is primary or secondary to the loss of the RPE, but it is known that changes occur in the RPE and that the photoreceptor loss is responsible for the loss of vision. The genetic history, as well as accompanying ocular, systemic, and physical findings, need to be considered in the diagnosis. Additionally, it is necessary to consider toxicity by various medications that may also alter the RPE in some fashion and result in loss of the photoreceptors. Electro-diagnostic testing also proves very useful in the confirmation of the diagnosis of RP, and in the determination of the classification of the RP. Some of the accompanying ocular signs of the disease that may need to be addressed include posterior subcapsular cataracts, vitreous haze, bull’s eye maculopathy, peripheral and central field loss, reduced visual acuity, and reduced night vision.
RP may present in two very different manners from a visual point of view.
The first, and more traditional, is the total loss of peripheral vision resulting in a central tunnel of 1°-20° with a steep margin. In this presentation, there is no vision in the area surrounding the central tunnel. Magnification is of little benefit here, as the central tunnel is generally the most sensitive area of residual vision and is typically small and narrow. These patients frequently have difficulty ambulating as their peripheral fields are absent and their ability to identify objects in their pathway is very limited. Their ambulation is generally met with insecurity, lack of confidence, and reduced safety. Their ability to read, work on a computer and work with their hands is similarly compromised by their limited field of view.
The low vision solution here would be to increase the size of the central tunnel and concurrently increase their ability to ambulate, read, and work with their hands, thus improving all of the aforementioned areas of compromised function. This can best be accomplished with reverse telescopic systems, or reverse amorphic telescopic systems, such as those created by Designs for Vision. These systems increase the field of view by 170 to 300%. While they increase the field of view, they decrease the acuity by a level that is typically inverse to the field expansion.
As an example, a patient who has a 5° central tunnel with acuity of 20/20 may have their field expanded 3 times to 15° with a reverse 3x telescope. In this instance, the acuity is thus decreased by a factor of three from 20/20 to 20/60. This still results in a great increase in the patients’ ability to move about with a much greater level of safety and confidence, and still have acuity adequate enough to identify most objects and read signs. If a tele-microscopic cap is added to the system, the patient will be able to function at various other ranges with a wider field of view. For example, a +2.00 tele-microscopic cap focusing at 20” would permit the patient to expand the field of view for such tasks as working on the computer.
The patient may be able to see 15 characters at a time instead of 5 at a 1.25M to 1.6M font size. Their reading speed and efficiency on the computer would be greatly enhanced, and their ability to see the cursor of the mouse is much easier to locate and track. A stronger cap, such as a +8.00, would give them a reading range of 6-7”, and the added magnification would permit them to see 15 characters at a 1.0M or 9-point font size. This system would greatly improve their efficiency at many different ranges for a wide variety of tasks.
The second is a gradual loss of sensitivity from the peripheral to the center. These patients have a sloping margin. In these cases, the central acuity may be similar to the steep margin patients, but the surrounding vision is greatly decreased and typically results in the patient reporting blurry vision. They probably won’t have the same issues with ambulation as the patients with steep tunnel margins, but they will complain of blurry vision inhibiting their ability to perform near point and intermediate tasks and identify faces and read signs when they are out and about. Patients in this second group will usually respond beautifully to magnification at all ranges of function.
An assessment of all forms of magnification should be done once the zones of sensitivity extending out from the macula are assessed relative to their size and sensitivity. As an example, a patient with a 5° central zone of 20/20 may still see only 5 characters at a time clearly but, for distance sighting, their periphery may actually “compete” with their central zone and decrease the acuity and functional size. There may be a large zone surrounding the central zone that is 5x larger, but has acuity reduced to 20/60. Magnifying this by 3x may increase the functional field at the 20/20 level to 25 degrees adding integration across this entire field, thus greatly enhancing patient comfort and performance.
This young man presented with no glasses of any kind. His unaided acuities in both eyes were 20/640, central fixation. With a refraction OD of +1.50-3.50×180 and OS +2.00-2.00×180 his acuities centrally were OD 20/280 and OS 20/200. His margins in both eyes were sloping. Testing revealed that the left eye had a central area of vision with a higher level of acuity then the corresponding zone in the right eye. The addition of a 1.7x Full Diameter Telescope (FDTS) optically corrected to integrate his refraction resulted in distant acuities of 20/160 OD and 20/120 OS. He was much more comfortable viewing intermediate targets (6-15 feet) under binocular conditions as this resulted in an expanded field of view over a monocular solution at these ranges. When a +12.00 tele-microscopic cap was introduced over the 1.7x FDTS OS, he was able to read 1.6M continuous print with this eye. His right eye was occluded, as there is no binocularity at a 3-4” focal range, and he was much more comfortable eliminating the interference and competition that was introduced from his right eye. For distance and mobility, various Bioptic Telescopic systems were evaluated. These included 1.7x, 2.2x, and 3.0x Bioptic (BIO-1) telescopes by Designs for Vision and the Ocutech 4x Sportscope. While Miguel liked the extra magnification of the 4x system, he preferred the binocular telescopes and greater field of view they offered. He was most comfortable with the 2.2x BIO-1 telescopes.
We recommended the 1.7x Telescopic system set up as a binocular Politzer system. The Politzer system yields a system that weighs less than half as much as the Full Diameter Telescope, still providing a favorable field of view, having a very large ocular lens and exit pupil. For mobility and distant viewing we recommended the 2.2x BIO-1 system.
We had been following the reports of the Immigration Detention Camps in the media. Our experience here was very different then what we had read and heard about. The personnel at the facility in Homestead, Florida, seemed to go the distance to assist this child. They brought him to 3 doctor visits, each time accompanied by two adult case workers. The case workers were very interested in their charge and wanted to seek whatever assistance that might result in a better visual outcome and improvement in the quality of life for this young man. The facility did what they needed to do to obtain funding for these special devices and they were dispended to Miguel. All personnel we had the pleasure of working with were focused on his well being, and we were proud to share in his care.