W7: Accommodation and Cycloplegic Refraction

WATCH LECTURE

Discuss the tests used to assess accommodation in paediatric patients and their normative values.

Discuss conditions that affect accommodation

Discuss the indications for cycloplegia of paediatric patients

Name the tests used to assess accommodation in paediatric patients

• Amplitude of Accommodation (AoA)

• Accommodative Facility

• Relative Accommodation

  • Fusional Reserves version of Accommodation

What is Amplitude of Accommodation?

• Measure of the max amount of accom that can be exerted

• Diff in D btwn the far and near point of accom relative to a reference point

• AoA dec’s as we get older

  • Bc’s symptomatic at approx 45 years-presbyopia

What factors affect the measurement of amplitude of accommodation?

• Technique used can affect AoA

• Subjective tech’s don’t allow for ocular depth of focus

  • Effect of pupil

How is amplitude of accommodation clinically determined?

• Measure the dist of the near point of accom to the spectacle plane while RE= fully corrected.

• If refractive correction is not worn the measured AoA would have to be adjusted

How is the near point of accommodation measured and converted to amplitude?

• NPA can be measured by push-up or push- down method (mono + binoc.

• The dioptric equiv of the NPA (punctum proximum) is the AoA

What are Hofstetter’s formulas for estimating expected amplitude of accommodation?

• Used to derive expected AoA for Caucasian subjects up to 60 years

• Max amplitude: 25 – 0.4 × age (years).

• Avg amplitude: 18.5 – 0.3 × age (years).

• Min amplitude: 15 – 0.25 × age (years).

What are the Hofstetter-calculated amplitudes for a 10-year-old emmetrope?

• Max amplitude: 25 – 0.4(10) = 21 D.

• Avg amplitude: 18.5 – 0.3(10) = 15.5 D.

• Min amplitude: 15 – 0.25(10) = 12.5 D.

Normative values

Age 6-12 years (Hashemi et al 2018)

• Average AoA

• Measured AoA

• Min AoA

How would you measure Amplitude of Accommodation using a RAF rule?

What is accommodative facility?

Ability of patient to rapidly change accommodation.

How is accommodative facility measured?

• Usually measured at 40cm.

• Target is N5 or N6 letter or words.

• RE=fully corrected

• ±2.00D lenses are flipped before the eye.

• Test is started w/ the pt trying to clear the letters through the +2.00D lens (accommodative stimulus = 0.5D).

• Then through the -2.00D lens (accommodative stimulus = 4.50D

What should clinicians consider regarding normative data for accommodation facility?

• Diffic as evidence base isn’t great.

  • Range of ages

  • Poor exclusion criteria

• Adv to form own impression of what is normal.

• Clinical pass rates

  • 7 cpm Monocular

  • 5 cpm Binocular

Give examples of accommodative disorders?

• Accommodative Insufficiency

• Accommodative Fatigue

• Accommodative Spasm

• Accommodative Inertia

What is accommodative insufficiency and what symptoms does it cause?

When accom is less than expected for their age

Symptoms:

• Blurred NV

• Frontal HA’s

What diagnostic criteria help identify accommodative insufficiency?

• AoA less than min AoA as det by Hofstetter’s formula (Borsting et al., 2003, Abdi et al., 2005)

• Accommodative Fatigue

  • Similar symptoms but more transient

What clinical signs are associated with accommodative insufficiency?

• Reduced AoA

• Reduced Accommodative Facility

• Reduced NV/ VA

• XOP @ Near, bc’s relatively esophoric if Pt tries to exert more accom

What treatment options exist for accommodative insufficiency?

• Hyperopic Rx

• Low add may be needed

  • If too high may prevent accommodative response acting as it should

• Pen to nose exercises

  • Can be related to Convergence Insufficiency

What is accommodative inertia and who is most affected?

• More prevalent in adults over 30 years.

• Accommodative system has diffic switching from dist to near vision and back again

What are the causes and signs of accommodative inertia?

Causes:

• Prolonged near work

• Poor GH

• Anisometropia

• Early presbyopia

• Holmes-Adie syndrome (unilateral cases)

Signs:

• Reduced AoA

• Reduced accommodative facility

How is accommodative inertia treated?

• Any underlying conditions should be treated

• RE corrected.

• Push up exercises/flipper exercises can help with accommodative facility

What is accommodative spasm?

• AKA Accommodative Excess

• Constant contraction of the ciliary muscle leads to exertion of accommodation

What are the causes of accommodative spasm?

• Uncorrected hyperopia

• Prolonged near work

• Underlying emotional cause

• Lesions of the brain

• Multiple sclerosis

• Meningitis

• Head trauma

What symptoms occur in accommodative spasm?

• Pseudomyopia

  • Cycloplegic Refraction should det myopia not present.

• HA’s

• Ocular Discomfort

• Esotropia + pupil miosis in more defined cases

How is accommodative spasm treated?

• Hyperopia should be gradually corrected.

• In more pronounced cases cycloplegics can be used. 

• Orthoptic exercises needed to prevent a reoccurrence

When is cycloplegia indicated in children?

• Young children:

  • <7 years

    • 1st ST

  • <4 years

    • First ST+ repeat eye exams in children

• When subjective refraction is limited.

• When dry ret = diffic

When is the need for cycloplegia indicated?

• Latent Hyperopia 

  • Dry subjective signif less +ve than ret

  • E.g., Ret R + L +4.00 D, Subj +1.50 D R and L

• Case History

  • problems focusing

• Suspected accommodative disorders

  • Reduced AoA

  • Reduced accommodative facility

  • Dynamic Ret

    • Lead of accom

    • Lag of accommodation >1.00 D

When should you consider the use of a cycloplegic agent according to the College Guidelines?

To give:

a) an accurate assessment of the RE (major factor in amblyopia or squint)

b) the best poss view of the fundus, w/in the limits of the co-operation of the child.

What is cyclopentolate?

• Muscarinic antagonist

• Prevents the eye from accommodating.

• Dilates the eye

What are the recommended cyclopentolate doses for children?

3 months – 11 years

• Apply 1 drop, 30–60 minutes before examination, using 1% eye drops.

12 – 17 years

• Apply 1 drop, 30–60 minutes before examination, using 0.5% eye drops

What are the side effects of cyclopentolate?

• Blurred vision

• Photophobia

• Psychosis, Hallucinations, Ataxia and incoherent speech

  • 2% conc.

  • Multiple drops of 1% (not advised)

What should be explained to the patient before instilling cyclopentolate?

• Obtain informed consent.

• Explain why you want to use cycloplegia.

• Explain visual effects

  • NV blur

  • Pupil dilation

  • Inc’d light sensitivity

What precautions should be taken before instilling cyclopentolate?

• Explain that drops will sting a little!

  • Important to maintain trust.

• Sometime better for another optom to put the drops in.

  • Good optom / Bad optom!

• Check for allergies

  • Consider near ret for prev reactions to drops

What should be checked after instilling cyclopentolate?

• Drops take about 30 mins to work.

• Check accom has relaxed.

  • AoA

• Check for Anisocoria

  • May indicate unequal cycloplegia

What information must be recorded when using cycloplegic drugs?

• Drug

• Dose

• Batch number

• Expiry date

• Example: Cyclopentolate, 1.0%, BN 1234, Exp 02/2022

What should be considered during retinoscopy under cycloplegia?

• Concentrate on centre 3-4 mm.

• Pupil periphery may be affected by aberrations + have a diff reflex.