Understanding convergence insufficiency

Take-Home

Recent randomized clinical trials have been advancing the understanding of current treatments for convergence insufficiency, but more prospective studies are needed to investigate convergence types and their roles in convergence insufficiency.

Dr. LambertBy Lynda Charters; Reviewed by Jennifer Lambert, CO

Boston-Convergence insufficiency is a common clinical entity with wide prevalence rates reported from less than 1% to 8.3%, said Jennifer Lambert, CO, who examined the most current research findings regarding various treatments for the disorder.

“Convergence insufficiency is defined as a near exodeviation of at least 10 to 15 prism D greater than the distance deviation,” said Lambert, who is an orthoptist at Boston Medical Center and clinical instructor at the Boston University School of Medicine. “Patients have remote near points and poor convergence amplitudes.”

Symptoms include:

·      Asthenopia

·      Diplopia

·      Blurring of letters at near

·      Headache

·      Closing of an eye

Treatments range from pencil push-ups, to computer-based programs and surgery.

Four types of involuntary convergence are recognized: tonic, proximal, accommodative, and fusional. Vergence is stimulated by retinal blur and retinal disparity, according to Lambert.

Initial knowledge about the vergence pathway indicated that the occipital cortex signals vergence premotor neurons in the midbrain reticular formation.

More recent research shows that this is a biphasic response: a vergence “pulse” initiates the movement, i.e., proximal convergence, and the vergence “step” is longer and finishes the convergence action, i.e., fusional and accommodative convergence.

“Most current orthoptic treatments are designed to increase fusional convergence amplitudes,” Lambert said. “However, research indicates that the pulse phase responds more to training. The improvement is temporary with no improvement in the step phase.”

Treatment analysis

Regarding the current treatments, the Cochrane Collaboration reviewed six trials that included 475 patients who underwent non-surgical treatment of convergence insufficiency, which was defined as an exophoria at near greater than distance. All patients had decreased near points or decreased convergence amplitudes at near. The primary outcomes were the near point of convergence and convergence amplitudes at 12 weeks, she explained.

The six trials that were included were:

·      Birnbaum et al. (J Am Optom Assoc 1999; 70:225-32) evaluated home-based versus office-based therapy and included 60 men over age 40.

·      Convergence Insufficiency Treatment Trial [CITT] (Br J Ophthalmol 2005; 89:1318-23) evaluated base-in prism versus placebo reading glasses and included 72 patients aged 9 to 18 years.

·      The second CITT study (Arch Ophthalmol 2005; 123:14-24) evaluated home versus office therapy with an office-based therapy placebo group and included 47 patients aged 9 to 18 years.

·      The third CITT study (Optom Vis Sci 2005; 82:583-95) evaluated the same treatment as the second study and included 46 patients aged 19 to 30.

·      The fourth CITT study (Arch Ophthalmol 2008; 126:1336-1349) evaluated home-based pencil push-ups, home-based computer orthoptics and pencil push-ups, office-based computer orthoptics with home-based reinforcement, and office-based placebo with home-based reinforcement. There were 221 patients aged 9 to 17 who participated.

·      Teitelbaum et al. (Optom Vis Sci 2009; 86:153-6) evaluated base-in prism with progressive lenses versus progressive lenses only and included 29 patients older than age 45 years.

The results of the analysis indicated that in children there was no statistical significance of the base-in prism reading glasses for near point convergence, convergence amplitudes or the score of the Convergence Insufficiency Symptom Survey questionnaire. In adults, the base-in prism with a progressive lens was more effective for symptom relief.

Evaluation of the orthoptics/vision therapy showed that office-based orthoptics was more effective than the home-based orthoptics and the office-based placebo.

There was no significant difference between home-based computer orthoptics and home-based pencil push-ups. The investigators found mixed results when they compared the home-based pencil push-ups with office-based placebo. The home-based computer orthoptics were found to be more effective than office-based placebo, Lambert said.

The analysis also evaluated compliance with therapy in the CITT study performed in 2008. Patients receiving office-based therapies had a higher compliance rate than the home-based therapy cohort.

The future

“Studies have shown that proximal and tonic vergence may be amenable to therapy,” Lambert said. “Exercises such as jump vergence with base-out prism or sustained near work with base-out prism may be possible areas of study.”

One study currently underway, conducted by the Pediatric Eye Disease Investigator Group, is evaluating home-based computer orthoptics versus home-based pencil push-ups.

“Recent randomized clinical trials have been advancing the understanding of the current treatment,” she said. “More prospective studies are needed to investigate other convergence types and their roles in convergence insufficiency.”

Jennifer Lambert, CO

E: Jennifer.lambert@bmc.org

Lambert has no financial interest in any aspect of this report.

Subscribe to Ophthalmology Times to receive the latest clinical news and updates for ophthalmologists.