Accommodative insufficiency

Accommodative insufficiency is a condition that affects the ability to maintain near vision focus for a prolonged time ¹. This is shown clinically by an insufficient amplitude of accommodation based on age-expected norms ². The American Optometric Association defines accommodative insufficiency as occurring when the amplitude of accommodation is lower than expected for the patient’s age and is not due to sclerosis of the crystalline lens ³. Accommodative insufficiency has been reported to be a common cause of eye strain (asthenopia) and other symptoms, in school children, associated with near vision ⁴. Review studies carried out with school samples, have reported accommodative insufficiency rates ranging from 0.2 to 32.5% ⁵. Children with accommodative insufficiency report many of the same near activity related symptoms as children with convergence insufficiency ⁶.

Accommodative insufficiency can also be associated with other binocular vision problems ⁷. As noted later, accommodative insufficiency and convergence insufficiency can be coincident in many cases. Children diagnosed with both are much more symptomatic than children with just convergence insufficiency or with normal binocular vision ⁸. Both conditions can exist separately as well. Patients with accommodative insufficiency alone can have normal fusional capacities. When a 4.00D base-in prism is placed before the eyes when reading, a convergence insufficient will report the print as more clear, whereas those with accommodative insufficiency noted blur ⁹. Eye tracking should be evaluated in patients that are suspected of having accommodative insufficiency, convergence insufficiency, or both ².

Accommodative insufficiency incorporates ill-sustained accommodation, paralysis of accommodation, and unequal accommodation. Ill-sustained accommodation is described as an early stage of accommodative insufficiency, where the amplitude can start out as normal, but deteriorates over time. Paralysis of accommodation is very rare and is described as permanent or temporary loss of accommodation resulting from infections, glaucoma, trauma, lead poisoning, or diabetes ⁷.

An understanding of the close association between accommodative function and convergence is also important. When patients accommodate, convergence occurs, and when they converge they also accommodate. This relationship can be quantified by the AC/A (Accommodative Convergence/Accommodation) and CA/C (Convergence Accommodative/Convergence) ratios, respectively. Accommodative and convergence insufficiency typically present at the same time, a likely result of a neurological link. The rate of co-morbidity has been shown to increase with the severity of
the convergence insufficiency ¹⁰.

There are several management options are available for accommodative insufficiency that includes plus lenses for near vision, optometric vision therapy, and monitoring ¹¹. Treatment for accommodative insufficiency is best addressed by use of therapuetic spectacle lenses. These are generally prescribed in a multifocal form to allow improved near vision accuracy whilst not disturbing distance vision, this being especially important in school children so they may shift focus with ease and clarity between board and page in class.

Accommodative insufficiency causes

Determining the cause of an accommodative dysfunction is important prior to deciding on a treatment approach. This can generally be done during the comprehensive case history. Accommodative insufficiency can also be the result of various systemic conditions or many of the medications taken for those conditions ⁷. Caution should be taken in all children that have been diagnosed with ADD/ADHD regardless of whether they are also taking medication. Granet et al. ¹² found a three times greater incidence of ADHD among patients with convergence insufficiency when compared to the general population. A three-fold greater incidence of convergence insufficiency in the ADHD population was also noted. Accommodation can be altered significantly by medications such as Adderall, Ritalin, Concerta and Dexedrine ².

Accommodative insufficiency signs and symptoms

Accommodative insufficiency symptoms begin almost simultaneously with an increase in near work demand ¹³. The inability to focus on near targets or to sustain clear vision for a period of time, double vision (diplopia), asthenopia (eye strain) and difficulty reading with
headache are the most frequent patient complaints ¹⁴.

In a recent study of patients diagnosed with accommodative insufficiency (n=96), the incidence of blur was 56%, headache (56%), asthenopia (45%), and diplopia (45%) ². Sterner et al. ¹⁴ found a prevalence of 42.4% of 59 patients had at least one subjective complaint including headache (28.8%), asthenopia (23.7%), floating text (18.6%), and facility problems
(5.1%), indicating a significant relationship between different accommodative parameters and subjective symptoms. However, there were no symptoms reported in children younger than 7.5 years ¹⁴. Even
when a diagnosis of accommodative insufficiency is present some patients do not report any symptoms ⁷.

Accommodative insufficiency symptoms

These symptoms are generally related to reading or other near tasks:

• Blurred vision
• Headaches
• Eyestrain
• Reading problems
• Fatigue and sleepiness
• Loss of comprehension over time
• A pulling sensation around the eyes
• Movement of the print
• Avoidance of reading and other close work

Accommodative insufficiency signs

Direct measures of accommodative stimulation:

• Reduced amplitude of accommodation
• Difficulty clearing -2.00 with monocular accommodative facility
• High monocular estimation method finding
• High fused crossed-cylinder finding

Indirect measures of accommodative stimulation:

• Reduced positive relative accommodation
• Difficulty clearing -2.00 with binocular accommodative facility
• Low base-out to blur finding at near

Accommodative insufficiency diagnosis

Accommodative insufficiency is frequently encountered in young school children and is related to subjective symptoms noted by the child. Any decrease in accommodative function among school children can contribute to near-work related problems and therefore have a negative effect on a child’s learning experience ¹⁴. Even though there are various accommodative problems reported in the literature,
accommodative insufficiency is the most common ¹⁵.

Many examination findings can be used to assist in the diagnosis of accommodative insufficiency. Scheiman and Wick ¹⁵ separate these in to two categories: direct and indirect measures of accommodative stimulation. Direct measures include reduced amplitude of accommodation, difficulty clearing -2.00 with monocular accommodative facility, high monocular estimation method finding, and high fused crossed cylinder finding. Indirect measures of accommodative stimulation include reduced positive relative accommodation, difficulty clearing -2.00 with binocular accommodative facility, and low base-out to blur finding at near ¹⁵.

Having a patient that fails all or most of the tests as described above does not happen often. There is rarely a textbook case of accommodative insufficiency that contains all of the signs. The patient may fail two direct measures and two indirect measures but pass the others. Convergence often plays an important role in the accommodative process.

While the gold standard for measuring accommodative problems is accommodative amplitude, the facility and response must also be addressed to properly diagnose these patients. When assessing accommodative facility, it is not only vital to focus on the end result of how many cycles per minute they complete, but also the quality of the patient response.

• Are they having difficulty with the plus, minus and/or both sides of the flipper?
• Does the duration of time it takes for clarity become longer during testing?
• Do the two eyes react in the same manner or measure the same cycles per minute?

This type of information can assist the practitioner in determining the best course of action.

Hofstetter’s formula, which states that the lower limit of normal is equal to 15-1/3 X (age of patient) has been studied and has been found to be a valid measure of accommodation. The average value of accommodation can be determined by using a slightly different formula, 18-1/4 (age of patient). If the value measured is 2.00 D below the calculated lower limit of normal, it is considered abnormal ¹⁵.

Accommodative lag is the difference between the accommodative stimulus and the patient’s response to that stimulus. Lag can be measured several different ways including binocular cross-cylinders and near point retinoscopy, such as the Monocular Estimated Method (MEM). A measurement of lag equal to or greater than +1.00 can be expected in patients with accommodative insufficiency or infacility ³. This also suggests that the patient could benefit from plus lenses.

Accommodative insufficiency treatment

The sequential management recommended begins with correction of ametropia, added near lenses and then optometric vision therapy. Uncorrected refractive error can lead to accommodative fatigue, which can be easily remedied in many patients ¹⁵. Once the ametropia has been fully corrected, retesting of the binocular and accommodative status should be considered.

Determination of an appropriate add power is made by analyzing data collected from facility testing, amplitude of accommodation, MEM retinoscopy, and balancing the PRA/NRA ¹⁵. When prescribing some doctors prefer single-vision lenses for near work while some use flat top bifocals. Daum in 1983 ¹³ and more recently Abdi in 2005 ¹⁶ reported success rates of 90% and 98% respectively in the reduction of symptoms in patients with accommodative insufficiency.

Progressive addition lenses are another option, though many pediatric optometrists appear to shy away from their use in children. One fitting change that is often made involves fitting the bifocal or progressive addition lenses segment height higher to increase the amount of time the patient is benefiting from the near prescription.

The Correction of Myopia Evaluation Trial (COMET) evaluated the adaptability of children to progressive addition lenses with a modified fitting protocol of setting the distance fitting cross 4 mm
above the pupil center. COMET was a multicenter, randomized clinical trial to evaluate whether progressive addition lenses vs. single-vision lenses slowed the rate of progression in children with juvenile-onset myopia over 3 years. Of the 469 children enrolled, 234 were assigned to single vision lenses and 235 were assigned to progressive addition lenses (+2.00 D near addition). By 1 month, all differences in adaptability disappeared and the frequency of all visual symptoms remained low and similar for both treatment groups. Most (98%) of the 235 children assigned to progressive addition lenses maintained the modified fitting protocol without any problems ¹⁷.

As suggested by the American Optometric Association, optometric vision therapy to remediate accommodative amplitude and facility, is the most effective treatment for accommodative dysfunction ¹⁵. While the exact procedures and the manner in which they are performed are at the doctors discretion, a three phase approach to vision therapy is recommended.

• Phase one encourages the clinician to develop a working relationship with the patient. Teach the patient awareness of feedback mechanisms that will be used during therapy to help them stimulate accommodation and reach normal age-expected levels of amplitude. During this phase, magnitude of accommodation will be emphasized over speed and will be accomplished with minus lenses and balancing with plus and minus towards the end of therapy. Some therapy methods utilized in this phase include lens sorting, the Hart Chart, and loose lens rock. It is also beneficial to concurrently train vergence due to the close relationship between accommodation and vergence ¹⁵.
• During phase two of treatment, it is important to emphasize the speed of your patient’s accommodative response. The therapy is balanced by using both plus and minus lenses during therapy, as used in phase one. At this point, biocular/binocular accommodative facility is also introduced, with activities such as red rock, and targets such as vectograms. Divergence and convergence therapy is again incorporated into this phase of therapy ¹⁵.
• Finally, the third phase emphasizes the integration of binocular, as well as accommodative therapy ¹⁵. The use of homework is crucial to the management of these patients. Many of the techniques used during training can be sent home and performed in the same manner as in office or modified in some way. The willingness of both the patient and the parent to participate in this process cannot be understated. With appropriate compliance from both the patient and parent, the outcomes and benefits of accommodative therapy are usually long-lasting.

References

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