Binocular vision problems are treatable in adults
Adult patients receiving vision therapy usually fall into one of three groups: those with asthenopia, those with strabismus with or without diplopia and those with amblyopia. Patients with binocular problems find us on the Web, are referred to us for vision therapy or are identified in our practice.
Being in the heart of Manhattan, most of our vision therapy patients are adults. Those referred to us usually come from pediatric ophthalmologists, other ophthalmologists and, occasionally, optometrists. Interestingly, our largest source of referred patients is ophthalmologists.
Higher demands on accommodation/vergence
The world has changed — it has become a two-dimensional near vision task world dependent on reading, desk work and computer viewing. The visual system was not designed to perform activities that lack the stereoscopic cues. Today’s visual demands require an accommodative and vergence system that can make accurate and sustained responses without fatigue.
Patients who perform a lot of close work or reading or who use computers extensively are more prone to develop signs and symptoms from accommodative or vergence dysfunction. Symptoms associated with accommodative and vergence anomalies include blurred vision, headache, ocular discomfort, ocular or systemic fatigue, diplopia, motion sickness and loss of concentration when performing a task.
In-office therapy: The patient is wearing liquid crystal glasses to separate the right and left views while viewing a stereoscopic picture with four numbers. One number appears in greater depth, like the Titmus circle test. The patient responds to the position of the stereo number (up, down, left or right). Correct responses result in positive reinforcement with a concurrent increase in fusional demand; incorrect responses result in negative reinforcement and a reduction in fusional demand. Thus, the patient controls the level of therapy.
Image: Cooper J
A high percentage of symptomatic computer workers have subtle binocular vision problems whereby ocular discomfort increases with computer usage. Similar findings have been reported for other populations who perform sustained near work, such as students, accountants and lawyers. In fact, asthenopia (after blur) is the second leading reason why patients 15 to 45 years old make appointments to see an eye doctor.
Computer vision syndrome has been described to be caused by dry eye problems and uncorrected small refractive errors. There is almost no scientific data to support this conclusion. In my experience, the leading cause of asthenopia (blur, headache, double vision, tiredness, etc.) is secondary to accommodative/vergence anomalies.
Convergence insufficiency occurs in about 5% of the population. In an excellent study, Sheedy demonstrated that dry eye symptoms and asthenopia had different symptomatology and can be easily differentiated. Thus, symptoms associated with a computer in which the patient complains of dryness, grittiness, or burning are usually due to dry eye, while complaints of headaches, discomfort and blur are usually due to accommodative/vergence problems.
The diagnosis can be easily be made with the Convergence Insufficiency Clinical Trial (CITT) symptoms survey, cover test at near, near point of convergence (NPC), positive relative accommodation/negative relative accommodation and a measurement of fusional amplitudes.
The CITT symptoms survey is an excellent questionnaire for practice management and identifying and quantifying asthenopia. Often when measuring NPC or fusional amplitudes, repeating the tests will result in asthenopia, grimacing or head retraction. These behavioral responses are almost diagnostic of symptomatic accommodative/vergence anomalies.
Once identified, the optometrist should advise the patient that these are muscle problems, not vision problems, and that glasses are prescribed for vision problems and eye exercises solve muscle problems.
Recent evidence from a pediatric CITT study supports the concept that prism glasses are no more effective than placebo glasses in eliminating asthenopia. In addition, numerous studies including the CITT pilot clinical trial have demonstrated that the most effective method of eliminating convergence insufficiency symptoms is office-based vision therapy. Prism and pushup therapy were no more effective than placebo therapy. Thus, we advocate the only clinically proven treatment for asthenopia.
As a primary care practitioner, my treatment of pediatric and adult patients with symptomatic accommodative and vergence anomalies is the same: office-based vision therapy supplemented with home-based computer exercises. One must improve accommodative amplitude and facility, vergence amplitude and facility and then integrate them.
However, not all of our patients elect to participate in in-office therapy supplemented with home therapy. For those patients who cannot participate in office therapy, we prescribe the Home Therapy System (HTS) computer program and pushup therapy. The HTS program allows our staff to monitor the progress of our patients via the Internet. In addition, we have the patients return to the office with performance printouts monthly. Success rates are about 95% in motivated patients.
Treating adult amblyopes
We often see patients who have amblyopia that was never properly treated when they were a child. These patients are concerned about their vision because they only have one eye and would like to improve their “lazy eye.” Most of these amblyopic patients have been told that there is no treatment after the age of 6. This is not true and was supported by the recent Amblyopia Treatment Studies supported by the National Eye Institute.
Generally, we treat these patients by fully correcting all anisometropic and astigmatic errors, patching for 2 hours for milder amblyopia (up to 20/60) and 6 hours for more severe amblyopia (worse than 20/60) (atropine or Cyclogyl [cyclopentolate HCl, Alcon] can be substituted for patching in some cases) and home hand-eye tasks at an acuity level that can just be seen. We usually prescribe the HTS amblyopia program. We see the patients every 3 months until their vision plateaus. Success is much higher than one would expect, with most patients achieving significant improvement. We stop treating when a plateau is reached after 3-month blocks of treatment.
When patients ask what the oldest age of neurological plasticity (oldest age of treatment) is, we tell them it is at death. If the patient has anisometropic amblyopia we then eliminate suppression by either in-office or home-based vision therapy.
Prism, vision therapy for strabismus
Strabismus may be divided into newly acquired vs. infantile, paretic vs. non-paretic and intermittent vs. constant. Newly acquired paretic strabismus patients need an appropriate workup.
We usually prescribe Fresnel prisms to either eliminate or decrease the diplopia symptoms. Older paretic strabismus patients may benefit from ground-in prism and supplemental vision therapy to enhance binocularity.
We have treated several vertical deviations secondary to decompensation of a vertical deviation with excellent success. Longstanding intermittent deviations usually respond well to vision therapy to enhance their binocularity.
We have treated intermittent hypertropes as large as 25 pd with about 6 to 9 months of therapy. The emphasis of treatment is contraintuitive. You need to increase horizontal fusional ranges and then systematically reduce the vertical prism in the glasses. If the deviation is too large, surgery will improve the treatment results.
Exodeviations respond much better than esodeviations. Large esodeviations are initially treated with surgery followed by vision therapy to initiate binocular fusion. Fusion prevents future deviations.
Adult patients who have binocular problems are often symptomatic and require treatment. They are usually highly motivated and easier to work with than children. Contrary to conventional wisdom, these patients are not too old to improve amblyopia, restore binocular vision in strabismus or eliminate their asthenopia with vision therapy.
Both in-office and home therapy have their place in the treatment regimen. These patients become enthusiastic and are important referrers to your practice.
For more information:
- Jeffrey Cooper, OD, MS, is a clinical professor at the State University of New York, College of Optometry. He can be reached at 539 Park Avenue, New York, NY 10065; (212) 758-0772; fax: (212) 758-3532; e-mail: firstname.lastname@example.org. Dr. Cooper has a financial interest in the HTS system. He is the original designer of the system, which is being used in National Eye Institute studies.
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