Accommodation + cycloplegia

What is accommodation?

• process by which eye changes its optical power to maintain a clear image/focus on an object as its distance varies

What is the near Triad?

when viewing near object , to make sure image is clear our eyes:

1) accommodate (change focus)

2) converge (to keep single stereoscopic image)

3) pupillary constriction

→ occurs automatically and equally in both eyes

how are the three elements of the near triad linked?

• neurologically linked 

• under control of parasympathetic nervous system 

why is accommodation and convergence important and what can problems with them cause?

• to maintain clear, single binocular vision at near

• problems cause blurry vision, double vision, headaches + eyestrain → makes reading difficult 

• in children this can have knock on effect on their learning + education

what are the 4 components of accommodation?

• Tonic accommodation

• Reflex accommodation

• Convergent accommodation

• Proximal accommodation

What is tonic accommodation?

• normal resting state where there is no stimulus

• usually between 0.00D-2.00D

What is reflex accommodation?

• an automatic response to maintain a clear retinal image (stimulus is blur)

What is convergent accommodation?

• amount of accommodation induced by convergence 

• given by CA:C ratio

What is proximal accommodation?

• accommodation arising from knowledge of object being close to you

what 3 different aspects of accommodation do we want to assess?

1) Amplitude → max amount of accommodation that can be exerted

(RAF rule)

2) Response → whether required amount of accommodation matches what is produced (is it accurate?)

3) Facility → how rapidly accommodation can change/react to different working distance

how does amplitude of accommodation change as we get older?

• amplitude of accommodation reduces with age → presbyopia  

what is the rough accommodation of 10-55 yr olds ?

10 → 14.00D

20 → 10.00D

30—> 7.00D

40→ 4.50D

50→ 2.50D

55→ 1.75D

> reduces by 2/3 D every 10 yrs

what are the normal values of amplitude of accommodation for children?

Average:

6 yr old → 16.7D reduces by 0.3 every 1 yr

7 yr old →16.4D

8yr old →16.1D

9yr old → 15.8D

10 → 15.5D

11→ 15.2D

12→ 14.9D

if children have lower than average values may cause issues

what are the clinical tests of measuring amplitude of accommodation?

RAF rule

• push up method measures near point of accommodation, where target moved towards patient until they report text first becomes blurred

• pull down method starts with target very close to patient (blurred) and moved away from patient until they report its clear

• Done with distance prescription in place and room lights on

can perform both methods + take average

• record monocular + binocular results:

e.g Amp of accomm = RE 8D, LE 8D, BE 10D

what target do we use for amplitude of accommodation?

> target that is one line bigger than their best near acuity

> subjective tests don’t account for ‘depth of focus’ → effect of pupil

how do we measure accommodative facility?

• use flippers → often +2.00 and -2.00, with patient viewing near target <40cm (budgie stick etc)

• looking through flippers patients report when text becomes clear→ then examiner switches flipper over + patient reports again when text clear

• one complete cycle would be +2.00 to -2.00 and back to +2.00(full stimulation and then full relaxation of accommodation)

• number of cycles that patient can achieve in minute recorded 

• quick way is to count how many different sets of lenses patient looks through divided by 2

what are the normal adult values for accommodative facility monocular and binocular?

monocularly→ 11 cycles/min

binocularly →8 cycles/min

Zellers et al 1984 → values vary between studies

what is the purpose of the flipper test for accommodative facility?

• useful for testing whether accommodation system becomes fatigued easily

what do the positive and negative flippers do in relation to accommodation?

Positive flippers first → relax accommodation

Then negative flippers → stimulate accommodation

can get patients to practice at home

what are the advantages of dynamic retinoscopy (response)?

• objective (useful for children)

• can be quick to perform → measure on eye as accommodation equal in both

• no working distance lens required → patients accommodation provides this

• tells us about accuracy of accommodation (accommodative response lag/lead)

• can leave room lights on (also good for children)

how is lag or lead tolerated in a patient?

• depth of focus of the eye

how to perform dynamic retinoscopy - Nott method?

• patient views target binocularly with their distance correction

• start with retinoscope alongside target

• if with movement → move ret backwards until neutral

• if against movement → move ret forwards until neutral

• record position of retinoscope in cm → using RAF rule

• calculate dioptric lag/lead of accommodation

D=100 / F

example of calculating lag/lead of accommodation using Nott method

• if target at 33cm but neutral reflex at 45cm then:

stimulus = 100/33= 3D

retinoscope = 100/44 =2.22D

Lag = 3-2.22

→ 0.78D

Describe the monocular estimation method MEM - dynamic retinoscopy

• patient views target binocularly with distance correction 

• retinoscope alongside target throughout 

• add plus lenses in front of patient if ‘with’ reflex → lag 

• add minus lenses in front of patient if ‘against’ reflex → lead 

→ lenses could act as a stimulus to accommodation (proximal)

what value is usual for a lag or lead of accommodation?

< or equal to 0.75D

what is the screening technique?

• children’s attention spans are short

• place detailed target about 25cm (Childs W.D) and place retinoscope 0.75D (4cm) behind the target 

• if reflex is against or neutral, accommodation is adequate 

• if reflex is WITH → there is UNDER accommodation

what are the 4 accommodative disorders?

1) Presbyopia

2) Accommodative insufficiency

3) Accommodative infacility

4) Accommodative excess

what is presbyopia?

• normal ageing changes of crystalline lens requiring a near addition

what is accommodation insufficiency?

• failure to obtain the expected amount of accommodation

• based on patients age and refractive status

what is accommodative infacility?

• difficulty changing accommodative response although amplitude is normal

• accommodation is sufficient but patient tires easily

what is accommodative excess ?

• over accommodating to a target

• difficulty relaxing accommodation

what are the features of accommodative insufficiency?

• poor near vision and asthenopic symptoms

• usually bilateral → if unilateral consider cause (glaucoma, trauma, inflammation)

• more common in myopes - bartuccio et al 2008 found 56% of cases had myopia

• reduced amplitude of accommodation for their age

• reduced accommodative facility (difficulty clearing -2.00D lens)

how is accommodative insufficiency treated?

• with a reading add (+1.00D)

• and/or exercise with flipper lenses

what is accommodative fatigue?

• considered intermittent version of accommodative insufficiency 

• symptoms increase as patient tires → can improve with rest 

what are the features of accommodative infacility?

• normal amplitude + accuracy of accommodation

• difficulty changing focus from distance to near or vice versa → most common symptom

• asthenopic symptoms - headaches, sore eyes etc

• poor accommodative facility with difficulty clearing both the plus and minus lenses

how can we manage accommodative infacility?

• correcting refractive error

• exercises

what are the features of accommodative excess?

• patient has difficulty with all tasks involving relaxation of accommodation

• Asthenopic symptoms, difficultyconcentrating on near work - variable but often worse at end of day

• difficulty clearing plus lenses on facility testing 

• lead of accommodation present 

how do we manage accommodative excess?

• correcting refracting error

• giving exercises

what is accommodative spasm?

• very rare, severe form of excess

• ciliary muscle CANNOT RELAX

• often caused by head trauma or psychosis

• can mimic myopia as distance vision becomes blurred

what are the prevalence of accommodative disorders?

• Sheiman et al 1996 → study of 1650 school children aged 6-18yrs , prevalence was 6%

• in Uni students may be high as 17%

• in children with learning disabilities much higher → 88%

accommodation in down syndrome

• all people with Down syndrome have reduced acuity + contrast sensitivity

• approx 75% of people with Down syndrome have abnormal accommodation

• average accommodative lag for 25cm target ~2D

how can we improve accommodative response for people with Down syndrome?

• prescribing D-seg bifocals - set them fairly high

• improves focusing + children are reported to have better concentration and writing skills

what is cycloplegia and what is it used for?

• most commonly a muscarinic antagonist called cyclopentolate (0.5% or 1%)

• prevents accommodation temporarily in order to get accurate refraction + dilates pupil 

• higher conc best for younger children 3months-11yrs and those with dark irides → may need second drop after 2-3mins

• required drops to be instilled about 30-60mins before examination

why should we (during ret) concentrate on the reflex within central 3-4mm of the pupil after cycloplegia?

• aberrations distort peripheral view

what are the college guidelines of when to use a cyloplegic agent?

a) accurate assessment of the refractive error , which is a major factor in amblyopia or squint

b) best possible view of fundus, within the limits of the co-operation of the child

when to use cycloplegia in optometric practice?

• in young children → if doubt about their vision, refractive stays, binocular status or first eye test

• any patient where subjective refraction and/or co-operation is limited 

• latent hypermetropia

• any problems with focusing or near work in case history 

• suspected accommodative disorders or lags of >1D

• cases of esotropia in children 

• malingerers? - patients you suspect are making up visual problem

How to instill cyclopentolate?

• obtain informed consent

• explain why it is necessary to use cycloplegia

• explain visual effects (blur, light sensitivity, big pupils)

• be honest and explain drops may sting

• check for allergies before instillation

• record drug, dose, batch number and expiry date

what are the side effects of cyloplegic drugs?

• blurred near vision (sometimes distance vision if uncorrected hypermetrope)

• photophobia (from enlarged pupils)

• rarely dizziness , tachycardia, psychosis, incoherent speech, hallucinations (generally stronger conc or multiple drops)

how long do effects of cyclopentolate last?

• 6-24 hours (possibly 48 hours in rare cases)

• if child going back to school make sure teacher aware that they’ve had drops and vision is blurry 

what to do for uncooperative patients when doing cycloplegia?

• get them to lie on their back with their eyes closed + place drop on inner canthus of each eye

• it will then fall into their eyes when they’re asked to open them

• full cycloplegia rarely achieved but generally acceptable to begin your refraction when accommodation reaches 1-2D

• once pupil dilated, ret reflex can become subject to additional spherical aberration making refraction more challenging

• so concentrate on reflex in central 4mm of pupil

What to prescribe to strabismic esotropes vs non-strabismic esotropes?

• strabismic esotropes → prescribe full amount of plus

• non-strabismics → ensure difference in prescription between 2 eyes corrected (anisometropia) but consider reducing plus to encourage emmetropisation

e.g if RE: +4.00DS and LE: +2.00DS, consider offering 1/3 less plus (based on worst eye) to aid compliance giving RE:+2.50DS and LE:+0.50DS

• have to maintain 2DS difference between both eyes

what should we prescribe to patients with exophoria?

• reducing plus as this will get worse if hypermetropia corrected 

what should you do if using atropine to final RX?

• remove +1.00DS from final Rx to allow for accommodative tonus

• unlikely to be necessary for cyclopentolate - generally what no tonus allowance needed +0.50DS at most

what are the alternatives to cycloplentolate?

• in hospital clinicians may use stronger anti-muscurinic called atropine (1%)

• however it can cause more severe side effects + reserved for children with very dark irides or where cyclopentolate has been ineffective

What is Mohindra near retinoscopy?

• near ret technique to determine refractive error without need for cyloplegic refraction 

• performed in complete darkness and assumes only tonic accommodation is present 

• Hence +1.25DS usually subtracted from end ret result