By David L. Armstrong, OD, FIALVS with Richard J. Shuldiner, OD, FAAO, FIALVS, Chief Clinical Editor
Regina S., a 69-year-old lady, was referred for low vision services by her retinal specialist due to vision loss from Tamoxifen retinopathy. Tamoxifen is the oldest and most prescribed selective estrogen receptor modulator (SERM). It is used to treat breast cancer or to reduce breast cancer risk in women who have not been diagnosed but are at higher than average risk of breast cancer. Very few (0-6%) develop retinal lesions resulting in visual impairment. Other possible ocular side effects may include cataracts, macular edema, bird shot choroidopathy, optic neuritis and keratopathy. 20 mg per day for 5 years is the usual course of treatment. However, some patients require continuing treatment for longer periods. This patient had been treated with Tamoxifen for 9 ½ years. The diagnosis of Tamoxifen toxicity had been made by a different retinal specialist 2 years before Regina S. was referred for low vision care.
This patient’s history included cataract surgery OU. As per policy, this author spoke with Regina S. by phone before scheduling a low vision evaluation. By asking pointed questions, her level of impairment and her goals were elicited. It seemed like low vision care would make a huge difference in her life. Her main goal of reading her Bible and resuming sewing seemed to be within reach.
LOW VISION CARE
Regina S.’s entering corrected distance acuity was 20/400 OD and 20/800 OS using the Feinbloom chart. The Feinbloom number chart is a handheld chart featuring numbers of varying sizes. It allows the practitioner the ability to move to difference distances as well as test for the best retinal locus of each eye by moving the chart in any direction. We found that Regina S. had no significant refractive error.
It was decided that the best mode of treatment was to start with low power, binocular magnification and increase magnification as needed. Therefore, +8.00 D (2X) with sufficient base in prism (called prismatics) were tried. Regina S. was able to read .8 M letters with some hesitation. The prismatic glasses were then replaced with a monocular 2X Clear Image microscope lens. The Clear Image microscope lens is a doublet lens which eliminates the aberrations of thick plus lenses. Regina was able to read .5 M letters quickly and accurately. She had brought her Bible and was very happy to be able to read so well.
In addition, Regina had brought a needle and thread with her at my request. Holding the needle at 5″ from her face as I’d instructed her and with strong illumination, she threaded it on the first try.
Telephone follow up two weeks later revealed a very satisfied patient. Her actual words were that the glasses were “fantastic”. She was building up her time reading with them and was very pleased to be able to read her Bible again.
Even with the superior optics of the Clear Image Microscopic lens, it would seem that 2X magnification would be insufficient for reading, given the 20/400 distance acuity. However, experienced low vision practitioners have learned not to use distance visual acuity as a guide to determine near magnification. Often less magnification than expected works well.
As for the difference in performance between the +8 prismatics and the +8 (2X) Clear Image, there are two factors to take into account. One is the clarity of the Clear Image lens, a doublet system with two thin lenses piggybacked, makes a significant difference in reading ability. The second is the difference in acuities of the two eyes which may, at times, cause interference in attempting binocularity.
Lastly, in addition to the microscope glasses, sufficient and proper illumination was very important in her case. Proper illumination is critical to most people with impaired vision.
Regina S. was very fortunate to have a retinal specialist who understood how devastating vision loss can be to his patients. By referring her for low vision care, her quality of life was significantly improved.