To compare the two questionnaires, Dr van de Graaf and colleagues invited 173 adults who had been treated by one orthoptist for amblyopia and strabismus as children between 1969 and 1974 at the orthoptic outpatient clinic of the Waterland Hospital in Purmerend, the Netherlands, to complete the AS-20 between 2009 and 2010. The A&SQ had been presented to the patients in 2002.
The researchers received 110 questionnaires. The mean age of the respondents was 44 years. For 93 of them, data about eye examinations and vision testing was available. Fifty-three had strabismus and amblyopia; 17 had anisohypermetropia and amblyopia; 20 had strabismus, anisohypermetropia and amblyopia; and three had deprivation amblyopia. This means that of the 93 persons, 20 did not have strabismus and none had diplopia.
Dr van de Graaf and colleagues identified factors that were common in the questions and assigned them a strength based on the percentage of variance in the responses of all items that was explained by the factor.
They found that six factors together explained 79% of the total variance of the combined AS-20 and A&SQ, which was similar to the findings of previous studies.
They also found that visual acuity of the worse eye was correlated most with all factors of both questionnaires. Strabismus angle did not correlate significantly with the factors.
Most of the patients with strabismus in their cohort had been treated adequately by surgery, and binocular vision correlated with psychosocial and social contact items. Impaired stereopsis might make it difficult for these patients to locate faces and gazes of other people, and limit their ability to initiate eye contact in conversation, Dr van de Graff and colleagues speculated.
One reason the AS-20 includes functional problems that are missing in the A&SQ is that it was developed with patients with adult-onset strabismus and diplopia who were more likely to develop these problems than patients who had these conditions in childhood, Dr van de Graaf and colleagues wrote.
“Whether a quality-of-life instrument for strabismus patients should contain such items, which may not be specific for strabismus, is open for debate,” they wrote.
In their analysis, the A&SQ overrepresents depth perception complaints.
Some experts have argued that two separate questionnaires in patients with strabismus and amblyopia should be used. Dr Van de Graaf and colleagues believe that administering one questionnaire is preferable, however, because the two conditions often occur together.
In one birth cohort study of 4,624 people, 3.4% had amblyopia, of which a third was caused by strabismus alone and a third by strabismus in combination with anisohypermetropia, they pointed out.
Dr van de Graaf and colleagues noted that the gap between the administrations of the A&SQ in 2002 and the AS-20 in 2010 is a limitation of their study. During the interval, some patients may have developed presbyopia, which could have caused their complaints of avoidance of reading, difficulty in concentrating, eye stress, reading problems, inability to enjoy hobbies and the need for frequent breaks when reading, they wrote.
Other visual functions, such as contrast sensitivity, could also have deteriorated during this time due to the decline in the refractive function of the lens, they added. Still, these factors are more likely to be of importance in older patients than those in their cohorts, they wrote.
Based on their analysis of the most important factors in these two questionnaires, Dr van de Graaf and colleagues are “considering the possibility of combining the best items of both questionnaires into a new quality-of-life instrument.”