Reader and Industry Forum
Stargardt’s Disease and Contact Lenses
BY KARA PASNER, OD, MS
Stargardt’s Disease is an inherited retinal disorder first described by German ophthalmologist Dr. Karl Stargardt in 1909. It is usually autosomal recessive, but autosomal dominant and mitochondrial pedigrees have been described. Vision loss occurs bilaterally and tends to initially progress rapidly, but then levels off at about 20/200. Often, this vision loss occurs in childhood or young adulthood. Visual complaints include poor visual acuity (VA), dyschromatopsia, central scotomas, and photophobia.
Clinically, Stargardt’s Disease is characterized by the numerous yellowish pisciform (fish-tail) shaped “flecks” at the retinal pigment epithelium (RPE) level. They may be widespread or concentrated at the macula, tending to fade over time. Usually, they are replaced by RPE atrophy. In some patients, the macula has a “beaten bronze metal” or “bull’s eye” appearance. Fluorescein angiography reveals a “silent choroid” in which the choroid does not fluoresce. Hyperfluorescence in the macula is variable, depending on the degree of RPE atrophy (Quillen and Blondi, 2002).
Managing Stargardt’s Disease
There is currently no known treatment for Stargardt’s Disease. The visual prognosis depends on the degree of macular involvement. In rare cases of choroidal neovascularization, laser therapy may be helpful.
Stargardt’s Disease mostly affects central vision, with clinically significant blind spots at or near the macula. Combined with reduced VA, this makes common activities of daily living—such as reading and recognizing faces— very difficult. However, most of the Stargardt’s Disease patients whom I have seen have adapted to their circumstances and lead active professional and personal lives. My patients have included a jewelery designer, college students, and a landscaper.
Helping these patients remain so active despite their visual impairment can sometimes be a challenge. Magnification at near is a must and fairly easily accomplished with a hand magnifier and/or electronic magnification system. Correcting any refractive error for distance is beneficial. Usually this provides subjective improvement in the clarity of their vision, although the impact of measurable VA can be minimal. However, patients still complain of photophobia and glare of varied severity, from mild to debilitating.
Studies have shown that the use of red-tinted spectacles can provide measurable improvements in visual acuity, decreased size of central scotomas, and enlargement of peripheral visual field and enhanced visibility of long-wavelength stimuli in normal illumination (Young et al, 1983; Young et al, 1982). In addition, red-tinted contact lenses have been shown to successfully alleviate photophobia in patients who have certain cone disorders. (Park and Sunness, 2004).
Although red-tinted spectacles provide much symptomatic relief, fitting these patients with tinted contact lenses can be preferable to both patient and practitioner. This is something that I have observed even when the tint color is the same in both modalities. One reason for this is that Stargardt’s Disease patients (and other patients who have a central scotoma) often look off to the side of the object that they wish to view so that it is out of their blind spot. Their line of sight, then, falls off the optical centers of the glasses into what may be areas of distortion, further obscuring their vision. This doesn’t happen with contact lenses. In addition, contact lenses provide complete pupillary coverage, which eliminates such problems inherent in glasses as the glare caused by the reflection of light off the back and front surfaces of the glasses. Finally, given that these lenses are worn full time—both indoors and outdoors—wearing tinted contact lenses is much more cosmetically appealing and less obvious compared to tinted glasses.
Fitting Contact Lenses on Stargardt’s Disease Patients
In the evaluation of a Stargardt’s Disease patient, I first perform a regular low vision exam including a tint acceptance evaluation whereby I trial several tinted spectacle lenses. If there is a positive response to the tint, I also let the patient try a standard redtinted contact lens that I use as a trial lens. The patient then returns for a second visit for a contact lens fitting. I choose the grade of the lens tint individually in a trial-and-error fashion. I use methafilcon A (55 percent water) contact lenses because this type of lens accepts tint better compared to lenses with low water content (Schornack et al, 2007).
After the fit has been established, I send the lens out for tinting with a 9mm central tint diameter. On a dark iris, the tint is hardly visible. Though the lens will alter the apparent color of a lighter iris, most patients feel that the benefits ultimately outweigh this negative.
A Research Opportunity
Currently, there is no scientifically based prescribing protocol for tinted lens prescribing decisions. A review of past studies of tinted lenses and low vision showed that little objective evidence has been provided to support anecdotal reports of improvements in visual performance. This was primarily due to experimental shortcomings (Eperjesi et al, 2002). Hopefully, future research will provide the evidence needed to make this a more commonly tried modality. CLS
For references, please visit www.clspectrum.com/references.asp and click on document #205.
Dr. Pasner is an assistant professor of vision care technology at the City University of New York, New York College of Technology. She also maintains a private practice limited to low vision rehabilitation at four locations in New York and New Jersey. You can reach her at firstname.lastname@example.org