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1. ACCOMMODATION
MOPB 021
N SHABALALA/ M MAKOMBELA

2. CONTENT
01 Introduction & Background
02 Mechanism of Accommodation
03 Accommodation Pathway
04 Types of accommodation
05 Amplitude of Accommodation
06 Accommodation Response
07 Accommodative Facility
08 Anomalies of Accommodation
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3. 01
INTRODUCTION
& BACKGROUND
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Accommodation: Is the mechanism by
which the eye changes refractive power
by altering the shape of lens in order to
focus objects at variable distances
Far point: Position of an object when its
image clearly falls on retina with no
accommodation.
Near point: Nearest point clearly seen
with maximum accommodation.
Range of accommodation: Distance
between far point and near point.

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THEORIES OF
ACCOMMODATION 01 Relaxation theory of
HELMHOLTZ
02 SCHACHAR’S theory
03 TSHERNING’S theory
04 CATENARY theory

5. Relaxation theory of
HELMHOLTZ
• Also known as the “Capsular Theory”.
• He considered that lens was elastic and in normal state it is
stretched and flattened by tension of the suspensory ligaments.
• During accommodation, contraction of ciliary muscle shortens
ciliary ring and moves towards the equator of the lens.
• Relax the suspensory ligaments, relieving strain.
• Lens assumes more spherical form, increasing thickness and
decreasing diameter.
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6. Relaxation theory of
HELMHOLTZ
• Imaging technique showed that ciliary muscle
move anteriorly & the equatorial edge of lens move
away from sclera during accommodation.
• Zonular fibers extending from ciliary processes to
lens equator, are relaxed during accommodation
• It is not clear how lens alters its shape when
tension in suspensory ligaments is relaxed
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7. SCHACHAR’S theory
• Presbyopia is due to growth in equatorial
diameter, leads to decrease in perilenticular
space
• Contraction of ciliary muscle cannot tense
zonules and expand lens coronally.
• SCHACHAR introduced use of scleral
expansion bands (SEB)
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8. TSHERNING’S theory
• This theory attributed increased curvature of
capsule to increasing tension of the zonules.
• It states that contraction of ciliary muscle pulls
zonules directly and increases tension of
capsule at equator of lens, which leads to
bulging of poles.
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9. COTENARY theory
• Proposed by COLEMAN
• The COTENARY (hydraulic suspension) theory proposes that
lens, zonules & anterior vitreous comprise a diaphragm between
aqueous and vitreous
• As ciliary muscle contracts it forms a pressure gradient, causing
anterior movement of lens zonules diaphragm and increasing
anterior central curvature.
• Presbyopia is due to increase in lens volume, results in reduced
response to pressure gradient created by ciliary body contraction.
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10. 02
MECHANISM OF
ACCOMMODATION
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When the eyes are fixed on a distant
object:
• Lens is flat due to the traction of suspensory
ligaments
When vision is shifted from the
distant object to a near object:
• Ciliary muscle contracts
• Stimulation of the parasympathetic nerves
contracts both sets of ciliary muscle fibers
• The contraction of the ciliary muscle relaxes
the suspensory ligaments, and the lens
assumes a more spherical shape

11. 03
ACCOMMODATION
PATHWAY
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The association fibers carry the impulses to frontal lobe.
The center for accommodation lies in: frontal eye field
(area 8) that is situated in the frontal lobe of cerebral
cortex
Receptors: RODS & CONES -> Visual impulses from
retina pass through the optic nerve ->optic chiasma ->
optic tract-> lateral geniculate body -> optic radiation to
visual cortex (area 17) of occipital lobe -> frontal eye
field (area 8)
AFFERENT PATHWAY

12. ACCOMMODATION
PATHWAY
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Efferent fibers to medial rectus: Some of the fibers from frontal
eye field terminate in the somatic motor nucleus of oculomotor
nerve. The fibers from motor nucleus supply medial rectus.
Efferent fibers to ciliary muscle and sphincter pupillae: From
area 8, the corticonuclear fibers pass via internal capsule to
the Edinger-Westphal nucleus of third cranial nerve. The
preganglionic fibers pass through the third cranial nerve to
ciliary ganglion. Postganglionic fibers from ciliary ganglion
pass via the short ciliary nerves and supply the ciliary muscle
and the constrictor pupillae.
EFFERENT PATHWAY
From Area 8-> EWN of CN3-> Ciliary Ganglion -> Short Ciliary
Nerve -> Ciliary muscle-> Increase in anterior curvature of
lens

13. ACCOMMODA
TION
PATHWAY
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14. 04
TYPES OF
ACCOMMODATION
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01 Tonic Accommodation
02 Proximal Accommodation
03 Reflex Accommodation
04 Convergence-accommodation

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TYPES OF ACCOMMODATION
Tonic accommodation
It is due to tonus of ciliary muscle and
is active in absence of a stimulus
The resting state of accommodation is
not at infinity but rather at an
intermediate distance

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TYPES OF ACCOMMODATION
Proximal accommodation
Is induced by the awareness
of the nearness of a target.
This is independent of the
actual dioptric stimulus

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TYPES OF ACCOMMODATION
Reflex accommodation
Is an automatic adjustment
response to blur.
It is made to maintain a clear
and sharp retinal image

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TYPES OF ACCOMMODATION
Convergence-accommodation
Amount of accommodation stimulated or
relaxed associated with convergence
The link between accommodation and
convergence is known as accommodative
convergence and is expressed clinically as
AC/A ratio.

19. 05
AMPLITUDE OF
ACCOMMODATION
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01 Push up to blur test
02 Minus lens to blur
03 Pull away to clear test
04 Monocular Estimate Method
DEFINITION
Amplitude of accommodation
(AoA) is the maximum increase in
optical power that an eye can
achieve in adjusting its focus from
far to near

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Purpose To determine maximum amount of accommodation that eyes are capable of producing
individually or together
Procedure: Near visual acuity chart placed on near point rod/RAF Ruler
Direct patient’s attention to 20/20 line of letters on near point card . Patient left eye occluded
Near point card brought closer to patient (2-3 inches per second)
Patient instructed to keep the letters as clear as possible and report when it blurs. Prompt the patient
to clear the target
Stop when patient can no longer clear the print within 2 to 3 seconds of viewing. Record the dioptric
points on the near point rod that corresponds with the blur. Procedure repeated for left eye
Amp (D) = 100/distance (cm)
PUSH-UP TO BLUR TEST

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SETUP
Patient is seated comfortably behind the phoropter viewing through his or her distance prescription.
A well-illuminated near target (one line of letters larger than the patient’s near visual acuity) is set at 40 cm.
Testing is done monocularly only.
PROCEDURE
Instructions to patient: “I will be changing the lenses in front of your eyes. Try to clear the print after each lens change. Tell me when
you notice that the letters [examiner indicates appropriate print] are slightly blurred, still readable, but cannot be cleared by further
effort.”
Minus lenses are added in 0.25 D increments. When the patient reports first sustained blur, the lens power is noted.
To obtain the amplitude in diopters, add 2.50 D for working distance to the amount of minus added.
• e. g Minus added until first sustained blur −6.00 D. Working distance (40 cm) −2.50 D. Accommodative amplitude −8.50 D
MINUS LENS METHOD

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SETUP
Ambient and overhead lighting should provide good illumination.
The line above best VA on a near card is used as the target.
The examiner should hold the target very close to the eye to begin the test.
If the patient wears glasses, these should be used.
Occlude the patient’s left eye.
PROCEDURE
To begin the test, slowly move the target away from the patient’s eye at approximately 1 to 2 cm/sec.
The target will be moved away from the patient until they can just report the letters. This will be considered the endpoint.
Measure the distance from the eye to the stick.
The accommodative amplitude will be measured to the nearest centimeter.
Amp (D) = 100/distance (cm)
PULL AWAY TO CLEAR TEST

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1. The distance prescription in on.
2. The patient is asked to fixate on an appropriate target on the MEM card attached to the
retinoscope head.
3. The examiner then moves closer to the patient observing the reflex.
4. If the initial reflex at the patient's Harmon's distance was a with movement, then the
amplitude is reached when a change to a more "with" movement is observed. This distance is
then converted to a dioptric value from the spectacle plane which is indicated of the patient's
amplitude.
5. If the initial reflex was against, the amplitude is reached when there is a change to a with
movement, the distance of which is then converted to a dioptric value.
Amp (D) = 100/distance (cm)
MONOCULAR ESTIMATE METHOD

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• Hofstetter formulae for expected amplitude as a function of age
(using the data of Donders, Duane and Kaufman)
• Maximum amplitude = 25 - 0.4(age)
• Probable (average pt should have) amplitude = 18.5 – 1/3 (age)
• Minimum amplitude = 15 - 0.25(age)
NORMAL VALUES

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• Example :
• For 20 years old patient Minimum AA is given by : 15 – 0.25
*age
• = 15 – 0.25 *20
• = 10 D
HOFSTETTER FORMULAE

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• The change in accommodative convergence that occurs when the patient
accommodates or relaxes accommodation by a given amount.
• Determination of the AC/A ratio is important in analysis of optometric data.
• The AC/A finding is a key characteristic in the final determination of the
diagnosis.
• It is also one of the most important findings used to determine the
appropriate management sequencefor any given condition.
• Norms 4 to 6 : 1
AC/A RATIO

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• There are two methods for determining a patient’s AC/A ratio.
• The first, referred to as the calculated AC/A ratio, is determined using the following formula:
• AC/A = IPD (cm) + NFD (m) (Hn − Hf ) where
• IPD = interpupillary distance in centimeters
• NFD = near fixation distance in meters
• Hn = near phoria (eso is plus and exo is minus)
• Hf = far phoria (eso is plus and exo is minus)
• Example: IPD = 60 mm, the patient is 2 exophoric at distance and 10 exophoric at near (40 cm).
• AC/A = 6 + 0.4(−10 + 2)
• = 6 + 0.4(−8) = 6 + (−3.2)
• = 2.8 When using this formula, one should remember to use the correct signs for esophoria and exophoria.
AC/A RATIO

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• The second method, called the gradient AC/A, is determined by measuring the phoria a second time
using −1.00 or −2.00 lenses.
• The change in the phoria, with the additional minus, is the AC/A ratio.
• (Phoria 1 – phoria 2) / lens
• For example, if the near phoria is 2 esophoria through the subjective finding and, with −1.00, it is 7
esophoria, the AC/A ratio is 5:1.
(2-7)/-1
=-5/-1
=5
Therefore AC/A ratio 5:1
AC/A RATIO

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• The effect of proximal convergence and the lag of accommodation result in calculated AC/A ratio and gradient
AC/A ratio being different.
• The calculated AC/A ratio is usually larger than the gradient because of the effect of proximal vergence, which
affects the near phoria measurement.
• Because the gradient ratio is measured by testing the near phoria twice at a fixed distance, proximal vergence is
held constant and theoretically does not alter the final result.
• The lag of accommodation also accounts for differences between the calculated and gradient AC/A ratio
measurements. Although the stimulus to accommodation is 2.50 D at near, the accommodative response is
typically less than the stimulus.
• This difference between the stimulus and response of the accommodative system is called the lag of
accommodation. The lag of accommodation is generally +0.25 to +0.75 D. Because the patient will tend to
underaccommodate for any given stimulus, the gradient AC/A tends to be lower than the calculated AC/A ratio.
AC/A RATIO

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• The extent to which a patient is able to stimulate (PRA) or relax (NRA) their accommodation
• The primary objective of these tests is to determine whether the patient requires an add for near work.
• The test is also used with the presbyopic population to determine if an add is necessary and to finalize the magnitude of the required add.
• The NRA can also be used to determine whether a patient has been overminused during the subjective examination.
• The NRA is performed through the subjective prescription, which should eliminate all accommodation at distance.
• Because the test distance is 40 cm, the patient will accommodate approximately 2.5 D to see the target clearly. Therefore, the maximum amount of
accommodation that can be relaxed is 2.50 D.
• Thus, an NRA finding greater than +2.50 suggests that the patient was overminused.
• It is important to ask the patient to keep the target clear and single during these tests. Traditionally, the instructional set is, “As I add lenses in front of
your eyes, keep these letters clear for as long as you can. Tell me when the letters are blurry.”
• It is important to also ask the patient to report diplopia, because these tests also indirectly probe the ability to maintain fusion using positive and
negative fusional vergence.
• The endpoint for the PRA will vary depending on the patient’s amplitude of accommodation, AC/A ratio, and the negative fusional vergence.
• The expected values for NRA are +2.00, ±0.50; for PRA, the expected values are −2.37, ±1.00.
NRA/PRA

31. 06
ACCOMMODATION
RESPONSE
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DEFINITION
Measure of actual accommodation
that is present
Accommodative stimulus -
Measure of accommodation
exerted by target or stimuli
Lag of accommodation =
Accommodative stimulus –
Accommodative response

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• When evaluating the accommodative or binocular systems, we usually present the stimulus at 40
cm. This creates an accommodative demand of 2.50 D. This is referred to as the stimulus to
accommodation.’
• Although the stimulus to accommodation is 2.50 D, the accommodative response will generally be
about 10% less than the stimulus (25).
• The expected finding for MEM retinoscopy, for example, which assesses the accommodative
response, is a lag of accommodation of about +0.25 to +0.50 D.
• It is important to be aware of the difference between the response and stimulus to accommodation,
realizing that most patients will underaccommodate by about 10%. An instance where this becomes
important is when comparing the calculated AC/A ratio to the gradient AC/A ratio.
ACCOMMODATION RESPONSE

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• The working distance should be at 40 cm for adults or at the Harmon distance (the distance from the
patient’s elbow to the middle knuckle) for children.
• Select an MEM card that is appropriate for the age and grade level of the patient.
• While the patient reads the words on the card, perform retinoscopy along the horizontal axis and estimate
the amount of plus or minus necessary to neutralize the motion of the retinoscopic reflex observed.
• A lens can be quickly placed before the eye being evaluated to confirm the estimate.
• It is important, however, not to leave the lens in place too long because it can alter the accommodative
response.
• Interpretation of the results of MEM testing is based on the assumption that the accommodative stimulus
at distance has been reduced to zero. If the patient is not wearing the subjective or has been
overcorrected or undercorrected, interpretation of the MEM result will be affected.
MONOCULAR ESTIMATED METHOD

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• When performing MEM retinoscopy, it is important to use normal room illumination.
• Accommodation is affected by illumination (e.g., dark focus), and dim illumination will alter
the accommodative response. Accommodation should therefore be tested under
illumination that the patient habitually uses.
• The expected value for MEM retinoscopy is +0.25 D to +0.50 D
MONOCULAR ESTIMATED METHOD

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• Any testing performed under binocular conditions is affected by both accommodative and binocular
function.
• Thus, although MEM is considered a test of accommodative function, binocular vision is also being
assessed. For example, a finding of less plus than expected may reflect overaccommodation
secondary to accommodative excess or high exophoria and decreased positive fusional vergence.
• A patient with high exophoria and inadequate positive fusional vergence may use accommodative
convergence to supplement the inadequate fusional vergence. This would enable the individual to
maintain binocularity, although it may lead to blurred vision secondary to the overaccommodation.
• The same reasoning applies to a finding of more plus than expected on MEM retinoscopy. This
could suggest either underaccommodation secondary to accommodative insufficiency or high
esophoria and reduced negative fusional vergence.
ACCOMMODATION RESPONSE

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• PURPOSE: To evaluate the accommodative response of a patient while viewing a near target under binocular
conditions.
• Because the fused cross-cylinder test is a subjective method, it is difficult to use with children younger than 8 to
9 years. It is generally easier and faster to perform MEM retinoscopy. This test is also not as repeatable as MEM
retinoscopy
• The expected value for the binocular fused cross-cylinder test is +0.50 D with a standard deviation of ±0.50 D
• High lag >+0.75D Lead of Accommodation < +0.25D
• This test finds the amount of plus that makes the accommodative stimulus and accommodative response equal
• Generally higher plus is found in high lag of accommodation and minus is found in lead of accommodation cases
• Presbyopes: this test provides the examiner with a tentative bifocal add
FUSED CROSS-CYLINDER TEST

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• SET-UP:
• Phoropter at near PD setting
• crossed cylinder grid placed @ 40 cm
• Turn auxiliary to +0.50 crossed cylinder
• Room light off, stand light illumination on
• Ask patient “Are ‘up and down’ or ‘across’ lines clearer, blacker, or sharper ?”
• If ‘across’ (horizontal) lines clearer - Under accommodation - So, add plus power binocularly until patient reports
equality or vertical lines become clearer
• If ‘up and down’ (vertical) lines clearer - Over accommodation - So, add minus power binocularly until patient
reports equality
FUSED CROSS-CYLINDER TEST

38. 07
ACCOMMODATIVE
FACILITY
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DEFINITION
Aka inertia of accommodation
Tests the ease of accommodative
response to the change in stimulus. To
determine flexibility of accommodative
system
Testing accommodative facility provides
an index of how quickly accommodation
can change

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Measured in cycles per minute
Flipper Lens Test Flipper lens - Two plus and two minus lenses
mounted in same holder - Available in powers of : +/- 0.50, 1.00, 1.50,
2.00, 2.50, 3.00
Purpose To determine the ability of accommodative system to respond
to lens created blur with a monocular stimulus presentation Note : In
the binocular presentation, the ability of both accommodative and
vergence systems to interact is tested Flipper Lens Test
ACCOMMODATIVE FACILITY

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Patient holds near-point VA chart with 20/25 letters at 40 cm
Direct light from overhead lamp
Distance correction worn
Left eye occluded
Flipper lens placed in front of right eye(usually minus side first)
Procedure
As soon as letters on acuity chart becomes clear, it is flipped to other side i.e. plus side
As letters become clear with plus side flip back lens to minus
Continue the procedure for 30 seconds
The process repeated for left eye for 30 seconds
ACCOMMODATIVE FACILITY

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• Record and interpretation
• Record no. of cycles in a minute 1 cycle = plus to minus and back to
plus again
• Expected Monocularly minimum = 12 cycles per min average = 17
cycles per min
• Binocularly minimum = 10 cycles per min average = 13 cycles per
min
• Near-Far test- Read up (SS)
ACCOMMODATIVE FACILITY

42. ANOMALIES OF
ACCOMMODATIO
N
08
4/12/2023 42

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Classification (by Duane)
• Insufficiency of accommodation
• Ill-Sustained accommodation
• ACCOMMODATION INFACILITY
• Excessive accommodation
• Spasm of accommodation
• Presbyopia
ANOMALIES OF ACCOMMODATION

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• Condition in which accommodative power is constantly less than lower
limit of normal range according to patient’s age
Etiology
• Premature sclerosis of lens
• Weakness of ciliary muscle due to systemic causes: Debilitating illness,
anemia, toxemia, malnutrition, dia betes mellitus, pregnancy, stress etc.
• Weakness of ciliary muscle due to local causes: PAOG, mild cyclitis as
during onset of sympathetic ophthalmia.
INSUFFICIENCY OF
ACCOMMODATION

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• Clinical features
• Features of eye strain and asthenopia.
• Head ach, fatigue & irritability of the eyes, while attempting near work.
• Near work is blurred & becomes difficult or impossible.
• Disturbance of convergence : intermittent diplopia.
• It is stable condition, if due to sclerosis of lens.
• But is not stable in association with ciliary muscle weakness
INSUFFICIENCY OF
ACCOMMODATION

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Treatment
• Identification & treatment of any systemic cause.
• Any refractive error should be corrected & if vision for near work is seriously blurred then additional
near correction has to be prescribed same as presbyopia.
• If associated with convergence excess then full spherical correction.
• Convergence insufficiency is there, then base in prisms can be added.
• Prismatic correction added should bring near point of convergence to same distance as near point
of accommodation.
• Weakest convex lenses should be prescribed, so as to exercise and stimulate accommodation.
• After recovery additional correction should be made weaker and weaker from time to time.
INSUFFICIENCY OF
ACCOMMODATION

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• Accommodative exercises:
• While doing exercises patient should wear correction for distance.
• Should be done simultaneously in both eyes, even if associated with
convergence insufficiency.
• But with convergence excess then the exercise should done with one
eye alternately.
• Accommodation test card exercise. (HART Charts)
• Useless in generalized debility and sclerosis of lens.
INSUFFICIENCY OF
ACCOMMODATION

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• Aka accommodation fatigue
• It is a situation in which though range of accommodation is in normal
range but it cannot sustain it for a sufficient period of time.
• Initial stage of insufficiency of accommodation
It occurs due to
• Stage of convalescence from debilitating illness
• Stage of generalized tiredness
ILL-SUSTAINED ACCOMMODATION

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Clinical features
• These symptoms are most commonly reported at the end of the day
• Blurred vision after prolonged near work.
• Headaches
• Eyestrain
• Fatigue, sleepiness and a loss of comprehension with continued reading
• A dull 'pulling' sensation around the eye.
ILL-SUSTAINED ACCOMMODATION

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Treatment
• Near work should be curtailed during debilitating illness.
• General tonic measures should be taken.
• The condition of illumination and posture while doing near work,
should be improved.
ILL-SUSTAINED ACCOMMODATION

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• It is a condition in which patient faces difficulty in altering the
range of accommodation.
• Amplitude of accommodation is normal.
• Ability to make use of this amplitude quickly and for long
periods of time is inadequate.
ACCOMMODATION INFACILITY

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Clinical features
• Difficulty changing focus from one distance to another
• Headaches
• Eyestrain
• Fatigue
• Difficulty sustaining near tasks
• Blurred vision Treatment: correcting any refractive error and
accommodative exercises.
ACCOMMODATION INFACILITY

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• Accommodative response is greater than the accommodative stimulus
• There is functional increase in tonus of ciliary muscle, results in a constant accommodative
effect
Causes
• Young hypermetropes frequently uses excessive accommodation as a physiological
adaptation
• Young myopes performing excessive near work, associated with excessive convergence.
• Astigmatic error in young patients
• Presbyopes in the beginning
• Use of improper and ill fitting spectacles
EXCESSIVE ACCOMMODATION

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Precipitating factors
• Excessive near work done, especially in dim or excessive illumination.
• General debility, physical or mental ill health
Symptoms
Blurred vision at near is uncommon
Blurred vision at distance
Headaches
Eyestrain
Photophobia
Difficulty changing focus from distance to near
Diplopia
EXCESSIVE ACCOMMODATION

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• Treatment
• It has a good prognosis.
• Refractive error should be corrected after carefully performed
cycloplegic refraction.
• Near work should be stopped for some time, after that it should
be done with proper illumination conditions.
EXCESSIVE ACCOMMODATION

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• Spasm of accommodation refers to exertion of abnormally excessive
accommodation.
Causes
• Drug induced spasm of accommodation is known to occur after use of
strong miotics.
• Spontaneous spasm of accommodation: attempt to compensate for a
refractive anomaly.
• Occurs when excessive near work is done with bad illumination, bad
reading position, state of neurosis, mental stress or anxiety.
SPASM OF ACCOMMODATION

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Clinical features
• Defective vision: due to induced myopia.
• Asthenopic symptoms
• Precipitating factors like marked degree of muscular imbalance,
trigeminal neuralgia, a dental lesion, general intoxication.
SPASM OF ACCOMMODATION

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Treatment
• Relaxation of ciliary muscle by atropine for 4 weeks or more and
• Prohibition of near work allow prompt recovery from spasm of
accommodation.
• Elimination of the associated causative factors to prevent the
recurrence.
SPASM OF ACCOMMODATION

59. END
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