What is accommodation (focusing) and why is it important?

Our eyes accommodation (focusing) system enables us to see up close. This is important when reading, using smart devices, applying make-up, sewing and using the computer. The natural lens in our eye, called the crystalline lens, has the ability to change shape in order to do this. Accommodation also includes the ability to quickly shift focus when looking from near to far, such as when looking from the book to the board, or reading the newspaper and then looking at the cricket score on the television. For young children with accommodation problems, reading material will become progressively blurry as they read for longer periods of time and their eyes get tired easily from the strain of trying to keep the written words clear. Sometimes, headaches may be an accompanying symptom. The optometrist will prescribe spectacles and/or commence vision therapy based on the findings to improve the child’s speed and efficiency of the accommodation system. Adults with accommodation problems will find simple tasks such as reading, sewing, doing manicure and looking at price tags becoming increasingly difficult. Reading glasses, bifocals or multifocals are prescribed by the optometrist to make these daily visual tasks easier.

Figure 1. Simplified schematic of the mechanism of accommodation. (R Nave HyperPhysics – Georgia State University)

What are the accommodation tests performed by the optometrist


Amplitude of Accommodation is an important test to measure the strength of the accommodation system. This procedure measures a patient’s ability to change focus of the eyes crystalline lens in response to viewing something of interest at near. The patient’s attention is directed to a row of letters and instructed to keep the letters clear on a device called a RAF rule that is held by the optometrist. The row of letters is slowly moved closer to the patient and the patient is asked to report when the letters become and remain blurry. This distance is measured and converted to a unit of measure called dioptres which represents the Amplitude of Accommodation. The closer the patient is able to bring the row of letters, the better the patient’s accommodation ability. The patient’s amplitude of accommodation is compared to age-matched normals to decide whether the value obtained is expected or not. Amplitude of accommodation decreases with age. In addition, patients tend to be symptomatic if their amplitude of accommodation is less than twice the dioptric working distance. For example, a person who works at 40 cm requires more than 5D of amplitude of accommodation (that is, 2×2.5D) to cope at near as a general clinical yardstick.

Figure 2. Amplitude of Accommodation testing. P.Ramkissoon, 2017.


Accommodative facility is the second test performed by the optometrist. The purpose of the test is to measure the patient’s ability to make rapid and accurate accommodative (focusing) changes. Here, the patient wears a pair of polarising glasses over the spectacles that are worn for viewing distant objects. The patient holds reading material that has a polarising sheet called a bar reader placed over it. The optometrist holds +/- 2.00D flippers over the polarising glasses while the patient looks at the reading material.

The optometrist places first the +2.00D lens in front of the patient’s eyes and the patient has to report when the print clears. As soon as the print clears, the optometrist flips the lenses to the -2.00D position and asks the patient to report when the print clears. The number of full cycles of +2.00D and -2.00D lenses that clears in 1 minute is a measure of the patient’s accommodative facility. The patient’s accommodative facility is compared to age-matched normals to ascertain if there is a problem with accommodative facility.

Next, the patient reads the text out aloud for the optometrist to establish if both eyes can read the print. If the patient misses certain words (called suppression), the optometrist can identify which eye this is, since each eye sees a different set of letters with the polarising filter/bar reader system. If an eye is suppressed, then certain words will not be seen and will appear black. Vision therapy is used to train accommodative facility and suppression in order for the patient to function more effectively.

Figure 3. Accommodative facility testing. P.Ramkissoon, 2017.


To corroborate the patient’s accommodation system problems that were found in the previous subjective tests, the optometrist performs near retinoscopy techniques. MEM retinoscopy is an objective technique to identify patients with accommodative problems without the need for the patient’s response. With this technique, the optometrist introduces lenses in front of the patient’s eyes while the patient reads words attached to the retinoscope held by the optometrist. Meanwhile, the optometrist observes
and evaluates the nature of the movement of the light that is seen at the pupil of the eye called the retinoscopic reflex. The characteristics of the retinoscopic reflex enables the optometrist to evaluate and diagnose the accommodative status of the patient. This test is very effective, firstly, it permits us to measure the person’s near focusing system, and secondly, it gives the optometrist a real- life insight of the patient’s accommodation.

Figure 4. Optometrist performing MEM retinoscopy. MEM retinoscopy is a quick near retinoscopy technique that reveals the nature of the patient’s focusing system strength and ability. P.Ramkissoon, 2017.
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