1. Purpose To subjectively measure the amplitude of accommodation under monocular conditions.

(a) Avoid relative magnification that affects results of push-up amplitude A concern about push-up amplitude is that it might overestimate accommodative amplitude—because of relative magnification of the target—as the chart is moved toward the patient’s eye. In the minus lens method, the testing distance remains stable as minus lenses are added in 0.25 D increments.

(b) Concern about minification Whereas the push-up method might overestimate the amplitude due to magnification of the target, the minus lens method may underestimate the amplitude because of minification of the target. Minification occurs when the patient views the target through increasingly greater amounts of minus lenses. To compensate for this concern, the test distance is 33 cm, but the working distance adjustment used is still 2.50 D.

3. Expected values The expected value for minus lens amplitude is about 2 D less than that for the push-up method (44).

1. Purpose To evaluate the stamina and dynamics of the accommodative response. The objectives of this test are similar to those discussed relative to fusional facility testing.

(a) Age The norms for these tests were initially developed using young adult subjects. Questions have been raised about the validity of applying these norms to other populations, such as schoolchildren and older adults between the ages of 30 to 40. Because the test is subjective, the results with young children may not always be reliable. A study by Scheiman et al. (51) indicated that accommodative facility testing has questionable value with children younger than 8 years. This same study demonstrated that the expected values for accommodative facility testing are different for schoolchildren.

More recently, Siderov and DiGuglielmo (68) investigated accommodative facility testing in adults from 30 to 42 years of age. They found a significant reduction in the expected values for this age group from the values expected for young adults. Yothers et al. (69) felt that the difference between the responses of schoolchildren and adults is related to the decrease in accommodative amplitude with age. They point out that standard accommodative facility testing is much different for a 10-year-old patient with a binocular accommodative amplitude of 12 D (where the test distance of 40 cm is 16% [2.5/12] of the binocular amplitude and the ±2.00 D lenses represent 33% [4/12] of amplitude) and a 30-year-old patient with a binocular amplitude of 5 D (where the test distance of 40 cm is 50% [2.5/5] of the binocular amplitude and the +2.00 D lenses represent 80% [4/5] of amplitude). As a result of these issues, they suggest altering BAF testing in response to measurement of the push-up accommodative amplitude—that is, amplitude scaled facility (Table 1.7). In their investigation, Yothers et al. (69) found that amplitude scaled testing differentiates symptomatic from nonsymptomatic children and adults better than the traditional test using ±2.00 lenses at 40 cm.

(b) Instructional set When testing adults, the clinician can simply ask the patient to report when the target is clear. With elementary schoolchildren, this may not be a reliable method (51). Rather, with young children, a target such as the Accommodative Rock Cards should be used (Fig. 1.5). Using this target, the clinician can ask the child to call out the number, picture, or letter after each flip of the lenses. If the child can accurately call out the number, this suggests accurate accommodation. When using this instructional set, different expected values must be used.

Test distance = 45% of amplitude^a

Lens power range = 30% of amplitude^b

Scoring criteria: Patients scoring less than 10 cpm are likely to be symptomatic.

^aRounded to nearest 0.5 cm.

^bRounded to nearest 0.25 D.

^cRange divided by 2.