Oct. 15, 2016
Convergence insufficiency (CI) is a common disorder of ocular alignment among both children and adults. It is characterized by an exophoria at near fixation and reports of horizontal diplopia and eye strain with prolonged reading. CI is diagnosed on the findings of a remote near point of convergence and decreased fusional convergence at near fixation.
"There is considerable variability in the reported prevalence of CI, with most estimates ranging from 2.25 to 8.3 percent among pediatric and young adult populations," says Brian G. Mohney, M.D., Ophthalmology, at Mayo Clinic's campus in Rochester, Minnesota. "The purpose of this study was to describe the clinical characteristics of CI in a population-based cohort of adults 19 years of age and older, diagnosed over a 20-year period, using a medical record retrieval system."
Dr. Mohney and a team of researchers studied the onset of CI in patients 19 years and older at the time of diagnosis drawn from a 20-year period in the Rochester Epidemiology Project. Results of the study were published by Rafif Ghadban, M.D., and others, in Ophthalmology in 2015.
Diagnosis of CI was based on either of the following criteria:
- Symptoms of double vision while reading with an exophoria or exotropia at near fixation test and an absence of double vision at distance
- An exophoria or exotropia of 10 prism diopters or more at near on prism alternate cover test with orthophoria or small (less than 10 prism diopters) phoria at distance
Each patient's entire medical record was reviewed for other ocular or medical conditions. Of 118 patients, 32 percent had hyperopia and 38 percent had myopia. Other ocular disorders included age-related macular degeneration in 17 percent and glaucoma in 8 percent of patients. The most prevalent associated systemic conditions included hypertension in 23 percent and coronary artery disease, hyperlipidemia and cancer in approximately 10 percent each. Four patients (3.4 percent) were diagnosed with Parkinson's disease.
A total of 118 adults (age- and gender-adjusted annual incidence, 8.44 per 100,000 patients) were diagnosed with CI between Jan. 1, 1985, and Dec. 31, 2004, constituting 15.7 percent of all forms of adult-onset strabismus observed in this population. The median age at diagnosis was 68.5 years, and 68 (57.6 percent) patients were female. Women in their 60s were the most prevalent.
The mean initial exodeviation at near was 14.1 prism diopters and 1.7 prism diopters at distance. The Kaplan-Meier survival curve rate of exotropia increasing over time by 7 prism diopters or more at near was 4.2 percent at five years, 13.5 percent at 10 years and 24.4 percent at 20 years.
Conservative management
Patients were followed up for a mean of 9.3 years. Although there was a significant increase in incidence with increasing age and nearly 25 percent of patients had an increase of their near exodeviation of at least 7 prism diopters by 20 years after diagnosis, most patients were managed conservatively:
- 13 (11 percent) of 118 patients' records did not supply management data
- 92 (88 percent) of the 105 patients were treated with prism spectacles
- 9 (9 percent) were treated with convergence exercises
- 4 (4 percent) underwent eye muscle surgery
- 3 (3 percent) elected to occlude one eye
"Convergence insufficiency is one of few forms of ocular misalignment that is relatively common in both children and adults. However, progression and surgical intervention is more likely in adults compared with children," says Dr. Mohney. "The results of multiple studies provide conflicting recommendations for managing CI in adults. Although home-based convergence exercises are the most commonly prescribed treatment, three of four patients in this study were managed with prism correction and only 9 percent with convergence exercises. This low rate of exercises in part may be the result of the difficulties elderly adults encountered with exercises and personal preference of treatment by the ophthalmologists."
For more information
Ghadban R, et al. The incidence and clinical characteristics of adult-onset convergence insufficiency. Ophthalmology. 2015;122:1056.