Continuing Education Activity

Accommodative excess is commonly found in children and adults. Accommodative excess is an abnormality of the accommodation resulting in blurred vision for near and distance. This is frequently found in patients with extended near-work demand. The symptoms of accommodative excess include eye strain, fatigue, and concentration loss. The management options for accommodative excess include glasses, vision therapy, and pharmacological agent (cycloplegic drugs). This activity reviews the evaluation and management of accommodative excess and highlights the role of the interprofessional team in improving care for patients with this condition.

Objectives:

• Describe the etiology, epidemiology, and pathophysiology of accommodative excess.
• Summarize the clinical features and evaluation of accommodative excess.
• Review the differential diagnoses and complications of accommodative excess.
• Explain the management of accommodative excess.

Introduction

The human eye can see any object placed at a variable distance from it by altering its structure (by altering the anterior lens surface). This phenomenon is called accommodation.[1] Accommodative dysfunction is a common vision disorder among the pediatric population with or without visual disturbance and binocular dysfunction. Accommodative dysfunction is either accommodative insufficiency or accommodative excess.[2]

Accommodative excess (AE) or excessive accommodation can be defined as a condition when the subject uses more accommodation effort or power than required for the stimulus at a particular distance or cannot relax the accommodation. Spasm of accommodation or accommodative spasm (AS) is defined as 'prolonged contraction of the ciliary muscle, most commonly causing pseudomyopia to varying degrees in both eyes by keeping the lens in a state of short-sightedness.'[3] 

AS falls in the spectrum of AE. AE is characterized by blurred vision at a distance, especially after prolonged near work, and difficulty refocusing from near to far. In the case of AS (also known as pseudomyopia), it always manifests. Headache, eye ache, and asthenopic symptoms are common in most cases.[4]

Etiology

Excessive Accommodation

The long duration of near work is an essential factor in the etiology of the accommodative excess.[3] Other factors include: 

• Young individuals with hyperopia often use excess accommodation to get clear vision without refractive correction.[5]
• Young myopes performing near activities for long duration use excess accommodative effort associated with excessive convergence.[6]
• Astigmatic errors at a young age may also be associated with excessive accommodation.[7]
• Presbyopes may use excessive accommodation to attain clearer vision for near work.[8]

Spasm of Accommodation

This is a spontaneous spasm of accommodation in children with a refractive anomaly that impairs their vision (hypermetropia, astigmatism, and sometimes even myopia).[9] It may be bilateral or unilateral. These children often do excessive near work in an unfavorable environment, such as insufficient illumination, mental stress, depression, and anxiety.[4]

Overstimulation of the parasympathetic nervous system (PNS) is also associated with muscle fatigue and part of excessive accommodation, excessive convergence, and mitotic pupils. This condition is known as the spasm of near reflex (SNR).[10] [11]

This may result from various factors, including:

• Topical medications (parasympathomimetics, cholinergic drugs including pilocarpine)[12][13]
• Myasthenia gravis
• Psychological factors (including anxiety)[14][15]
• After the refractive procedures, including laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK)[16][17]
• Head trauma[18]
• Opioid use disorder (OUD)[19]
• The toxic reaction of drugs (sulphonamides) and antipsychotic drug administration (haloperidol and biperiden).[20][21]

Epidemiology

Various studies have reported the prevalence of accommodative dysfunction in non-strabismic and non-presbyopic populations, but there are few studies on the prevalence of accommodative excess. In a study among South African students prevalence of AE was 2.8% between 13 to 19 years of age.[22] 

In a survey of university students, 10.8% of cases had accommodative excess though 32.3% of the subjects had binocular dysfunction.[23] Another survey on binocular vision anomalies in non-strabismic populations (7-17 years of age) in south India showed that 0.8% of the 'non-strabismic anomalies of binocular vision' was accommodative excess in rural schools.[24] A study on opioid use disorder (OUD) among 80 males in 2019 in Iran showed that the prevalence of AE was 3.75%.[19]

History and Physical

The history of accommodative excess must be recognized. Most often, clinicians consider all visual and asthenopia symptoms only as a refractive problem.[25]

Asthenopia is a terminology or word to describe eye strain, or fatigue of the eyes, such as that caused by reading, near work, or looking at a computer screen for too long.[4]

Symptoms of the accommodative excess are common, including blurring the vision for distance and near. Initially, it is associated with excessive near work, headache, eyestrain, brow ache, ocular deviation (esotropia), and sometimes diplopia.[4][26] 

In the case of spasm of accommodation, asthenopic symptoms are more marked than visual symptoms. Accommodative spasm subjects may be associated with macropsia due to optical illusion. Far and near points become nearer to the eye (in accommodative spasm condition, near point is abnormally close). Pupillary diameter becomes smaller (miosis).[27][28]

Evaluation

The evaluation of cases with AE includes:

A) Visual acuity: Visual acuity should be measured monocularly and binocularly at a distance and near both uncorrected and best-corrected, respectively. Some patients with accommodative excess may report that their visual acuity fluctuates.

B) Refraction: Refractive status of the patients should be evaluated objectively and subjectively. Cycloplegic refraction is the best option for evaluating true refractive status.[29] Patients with accommodative excess, hyperopes, and astigmatism often used ciliary tone (about 1D), the excess accommodative effort to correct some degree of refractive errors.

C) Ocular mobility: The ocular movements should be assessed in gaze. And the difficulty in movement in any gaze should be noted. This test was performed to rule out the overaction and underaction of a muscle. 

D) Cover test: A cover test should be carried out based on the corneal reflection and performed with a small target. IT should be neutralized during the cover test with prisms if any deviation is noted. 

E) Near point of convergence (NPC): This test is essential for assessing the binocular function. This test was conducted by a small target. The NPC is the point at which one eye begins to deviate outwards, or the subject report at the point when a small accommodative target becomes double.

F) Amplitude of accommodation (AA): the amount of dioptric power needed to focus an object from infinity to the nearest point; this is known as amplitude of accommodation.

Using a formula based on Diane's data, Hoffstetter proposes an equation to calculate the AA for a different age.[30]

• Mean AA = 18.5 – 0.3 × age
• Minimum AA= 15 – 0.25 × age
• Maximum AA= 25 – 0.4 × age

In clinical practice, we can measure the amplitude of accommodation by the push-up method  (Donder's push-up method) and the minus lens methods.[31][32]

Donder's push-up method uses the Royal Air Force (RAF) ruler; the near point of accommodation is calculated, thus the accommodation's amplitude.

Minus lens method: In this method, concave lenses are added at 6 feet distance-target monocularly and binocularly until the subject reports blur at a distance. The power of the lens used is the amplitude of accommodation.

G) Relative accommodation: The amount of accommodation required to increase or relax to focus an object binocularly at a specific distance, with a fixed convergence. This can be positive (positive relative accommodation, PRA) or negative (negative relative accommodation, NRA).[33]

NRA refers to the least amount of accommodation or an individual maximum relaxation of accommodation while focusing on an object at a fixed distance. PRA refers to the maximum accommodation used for focusing an object at a fixed distance. A low NRA indicates accommodative excess, and a low PRA indicates accommodative insufficiency.

H) Accommodative facility: This test checks the ability to change the accommodative power rapidly. This test can be done monocularly or binocularly. Clinically this can be measured by an accommodative flipper (+/- 2D or any other combination of plus-minus lenses).[34]

A flipper combines two plus and two minus lenses with the same amount. The subject focuses through one pair of lenses on an object at a fixed distance (generally 40 cm); when the object is well-focused, a flip movement of the flipper is performed, and the asked subject focuses again through them. Then this is reported again; this is one cycle. And record the number of cycles completed per minute. Also, note with which lens the subject faces more difficulty. If the patient has difficulty with plus lens monocularly, then they may have accommodative excess.

I) Monocular estimated method (MEM): This test is done to objectively determine a subject accommodative response that is lead or lag of accommodation.[35] MEM retinoscopy was performed at a 40-cm distance with a near-paragraph text card. The examiner observed and neutral horizontal retinoscopy reflex in each eye separately. The normal range of MEM values was +0.25D to +0.75D. Less of the MEM value indicates accommodative excess.

J) Ocular health and systemic health assessment: External ocular examination to rule out exophthalmos (associated with Graves) and ptosis. Slit-lamp biomicroscopy should be performed to rule out media abnormalities. A refractive procedure is previously done. Dilated fundus examination to rule out retinal abnormalities. Systemic examination to rule out some systemic conditions, i.e., multiple sclerosis, diabetes mellitus, Graves disease, myasthenia gravis, and mental health assessment.

K) Magnetic resonance imaging (MRI) and or computed tomography (CT) Scan: in case of close head trauma, it is essential to rule out any organic cause using an advanced imaging procedure.

Treatment / Management

The managing strategy for managing accommodative excess goals on eliminating the underlying cause ( functional or organic) and improving visual hygiene is important in the case of functional etiologies. 

Treatment options for the accommodative excess can be an optical correction, vision therapy, pharmacological, and a combination of them.

• Optical correction: refractive error correction with appropriate spectacle is the first consideration for managing accommodation excess because uncorrected refractive errors can cause accommodative fatigue. The correction should be given after cycloplegic refraction. In addition, near work should be restricted for a period.[3][36] Accommodative excess patients could not benefit from adding plus lens alone because of low NRA and low MEM. With cycloplegic therapy added plus lens benefit for near vision.[37] A maximum plus lens without visual disturbance should be given. 

• Vision therapy (VT): The objective of vision therapy in accommodative excess aims to improve accommodative amplitude and improvement of the accommodative facilities.[38] The common VT techniques used to manage accommodative excess include accommodative flipper, Hart chart, Rock chart, computer application, and home exercises.[39]

The target of vision therapy is to normalize the accommodative amplitude. This is followed by increasing the speed of response on accommodative stimulation. Finally, normalize accommodative and vergence reflexes and maintain them.

• Pharmacological: The most effective option is to use cycloplegic drugs to relax the ciliary muscle spasm. Atropine 1% show a better result than other cycloplegic drugs like homatropine 2%, cyclopentolate 1%, and tropicamide 1%; they are associated with ocular discomfort and near vision problem.[40] Cycloplegic eye drops required tapering of dose after four weeks of starting or switching to weaker cycloplegic.

Differential Diagnosis

Accommodative excess can be misdiagnosed as myopia without cycloplegic refraction or bilateral sixth nerve palsy.[28]

Prognosis

The most effective treatment is cycloplegia of the ciliary muscle, vision therapy in-office, and home therapy. Patients with accommodative excess after successful treatment should be followed-up every six months. Those with spectacles should be followed up every three to six months.

Complications

If accommodation excess isn't treated, it may lead to developing accommodative esotropia.[37]

Deterrence and Patient Education

Accommodative excess is not only a refractive problem but also a neuromuscular problem. A spectacle is not the only treatment option; vision therapy, visual hygiene, and mental health care are also part of the treatment. Subjects with AE, particularly pseudomyopes, may become discouraged from wearing the corrected spectacle. Parents can be dissatisfied with the recommendation of spectacles for their children.[41]

Enhancing Healthcare Team Outcomes

The main goal is to provide good vergence and accommodative facility to patients. Appropriate refractive error correction should be prescribed, and patient counseling on visual hygiene is critical. Coordination with a psychiatrist as part of an interprofessional approach to care may be required where anxiety is a cause of accommodative excess.