this ppt contains information about theories, types anomalies of accommodation with treatment, signs and symptoms.

1. ACCOMMODATION
PRESENTED BY:
REEMA DANDAVATE
T.Y.B.OPTOMETRY

2. WHAT IS ACCOMMODATION ?
• KNOWN FACT : in an emmetropic eye, parallel rays of
light coming from infinity are brought to focus on retina,
with accommodation at rest.
• WHAT ABOUT THE DIVERGING RAYS COMING FROM
NEAR OBJECT ?
• Our eyes has been provided with a unique mechanism by
which we can even focus the diverging rays coming from
near object on retina in bid to see clearly. 
ACCOMMODATION.
• IN IT THERE IS INCREASE IN LENS POWER.

4. SOME TERMINOLOGIES...
• NEAR POINT OF ACCOMMODATION :
• The nearest point at which small objects can
be seen clearly is called near point of
accommodation or punctum proximum.
• the distant point is called far point off
accommodation or punctum remotum.

5. • RANGE OF ACCOMMODATION:
• The distance between near point and far point
is called range of accommodation.
• AMPLITUDE OF ACCOMMODATION:
• The difference between DIOPTRIC power,
needed to focus at near point (P) and to focus
at far point (R), is called amplitude of
accommodation (A). Thus, A=P-R

7. POINTS TO BE KNOWN...
• In HYPROPIC eye, far point is virtual and lies
behind the eye.
• In MYOPIC eye, far point is real and lies in
front of the eye.
• In an EMMETROPIC eye, far point is at infinity
and near point varies with age...

8. Near point in centimeters Age in years
7 10
25 40
33 45

9. DEPTH OF FIELD...
• The range of distance from the eye in which
an object appears clear without change in
accommodation is termed depth of field.
• It reduces the necessity for precise
accommodation.

11. DEPTH OF FOCUS...
• The range at the retina in which an optical
image may move without impairment of
clarity is termed as depth of focus.

12. THEORIES OF ACCOMMODATION…
• Numerous theories have been proposed on
accommodation.
• Few of these are as follows.

13. PROOF OF EXISTENCE OF
ACCOMMODATION
• Till 17th
century  unknown that it is necessry
for eye to change its power in order to focus
• 1619  Christopher Scheiner gave proof of
existence of accommodation.
• 1801 Thomas Young demonstrated lens is
responsible for accommodation

14. 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.

15. 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.

17. GULLSTRAND mechanical model of
accommodation
• It is based on HELMHOLTZ hypothesis
• GULLSTRAND devised a mechanical model to
explain accommodation.
• It shows in unaccommodated state elasticity
of choroid is stronger than lens. When
accommodation comes into play weight i.e
ciliary muscles contract to overcome elasticity
of choroid.
• It helps lens to take accommodated shape.

19. MECHANISM OF
ACCOMMODATION

20. Changes in eye due to
accommodation...

Slackening of the zonules

Change in the curvature of lens surface

Anterior pole

Axial thickness

Changes in the tension of lens capsule

The lens sinks down

21. Change within the lens substance
Pupillary constriction and convergence of eyes
The choroid
The ora serrata

22. AC/A ratio
• The AC/A ratio is the relationship between
accommodative convergence (AC) expressed
in prism diopetrs, and accommodation (A)
expressed in lens diopters.
• This relationship is linear one and is thought
to be relatively stable throughout life.
• Normal AC/A ratio- 3-5 prism D for 1D of
accommodation.

23. NEGATIVE RELATIVE
ACCOMMODATION (NRA)
• NRA is a measure of its maximum ability to
relax accommodation while maintaining clear,
single binocular vision.

24. POSITIVE RELATIVE
ACCOMMODATION (PRA)
• PRA is ameasure of maximum ability to
stimulate accommodation while maintaining
clear, single binocular vision.

25. REACTION TIME
It refers to a time lapse between the
presentation of an accommodative stimulus and
occurrence of accommodative response.
•Average reaction time for far-to-near
accommodation is 0.64 sec and for near-to-far is
0.56 sec

26. 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.
• Proximal accommodation
– Is induced by the awareness of the nearness of a target.
This is independent of the actual dioptric stimulus.

27. • Reflex accommodation
– Is an automatic adjustment response to blur which is
made to maintain a clear and sharp retinal image.
• 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.

28. ASSESSMENT FOR ACCOMMODATION.

32. ANNOMALIES OF
ACCOMMODATON…

33. ANOMALIES OF
ACCOMMODATION
• DIMINISHED ACCOMMODATION
• PRESBYOPIA

34. Presbyopia
Presbyopia is a condition of physiological
insufficiency of accommodation leading to a
progressive fall in near vision.

35. Pathophysiology
• In emmetropic eye far point is infinity and near
point varies with age (being about 7 cm at 10
years, 25 cm at 40 years and 33 cm at 45 years).
• We read from 25 cm. After 40 years, the near
point recedes beyond normal reading or working
range.
• Failing near vision due to age-related decrease in
amplitude of accommodation is called
presbyopia.

37. Causes
• Decrease in accommodative power of lens with
increasing age, leads to presbyopia, occurs due to:
– Age-related changes in lens:
oDecrease in elasticity of lens capsule, and
oProgressive, increase in size and hardness (sclerosis) of lens
substance which is not easily moulded.
– Age related decline in ciliary muscle power.

38. Premature presbyopia:
• Uncorrected hypermetropia.
• Premature sclerosis of the crystalline lens.
• General debility causing pre-senile weakness of
ciliary muscle.
• Chronic simple glaucoma.

39. Symptoms
• Difficulty in near vision.
• Patients complaint of difficulty in reading small prints
• Asthenopic symptoms due to fatigue of the ciliary
muscle are also complained after reading or doing
any near work.

40. Optical treatment
• Prescription of appropriate convex glasses for near
work.
• A rough guide for providing presbyopic glasses in an
emmetrope can be made from patient’s age.
– About +1 DS is required at the age of 40-45 years,
– +1.5 DS at 45-50 years,
– + 2 DS at 50-55 years,
– +2.5 DS at 55-60 years.

41. Basic principles of presbyopic
correction
• Refractive error for distance is corrected first.
• Correction needed in each eye should be tested
separately and add it to distant correction.
• Near point should be fixed according to the profession of
patient.
• Weakest convex lens with which one can see clearly at
near point should be prescribed, overcorrection will also
result in asthenopic symptoms.
• Presbyopic spectacles may be unifocal, bifocal or
varifocal.

42. Surgical Treatment
• Corneal procedures
– Non ablative corneal procedure
• Monovision CK
– Laser based corneal procedure
• Laser thermal keratoplasty (LTK)
• Monovision LASIK.
• Presbyopic bifocal LASIK
• Presbyopic multifocal LASIK C
Near
Vision
Distant
Vision

43. • Intraocular refractive procedure
– Refractive lens exchange
– Phakic refractive lens
– Monovision with IOLs
• Scleral based procedures
– Anterior sclerotomy with tissue barriers
– Scleral spacing procedure
– Scleral ablation with erbium : yag laser

44. Insufficiency of accommodation
• Condition in which accommodative power is
constantly less than lower limit of normal range
according to patient’s age.

45. Etiology
• Premature sclerosis of lens
• Weakness of ciliary muscle due to systemic causes:
Debilitating illness, anemia, toxemia, malnutrition,
diabetes mellitus, pregnancy, stress etc.
• Weakness of ciliary muscle due to local causes:
PAOG, mild cyclitis as during onset of sympathetic
ophthalmia.

46. 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.

47. 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.

48. • 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.

49. • Accommodative exercises.
– While do 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.
– Useless in generalized debility and sclerosis of
lens.

50. Ill-Sustained accommodation
• 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
– When the patient is relaxed in the bed

51. 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.

52. 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.

53. Inertia of accommodation
• 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.

54. 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.

55. Paralysis of accommodation
• Cycloplegia, refers to complete absence of
accommodation.
• Causes
– Atropine, homatropine or other parasympatholytic
drugs.
– Internal ophthalmoplegia (paralysis of ciliary
muscle and sphincter pupillae)due to neuritis
associated with diphtheria, syphilis, diabetes,
alcoholism, cerebral or meningeal diseases.

56. – Complete third nerve paralysis due to intracranial
or orbital causes.
– Systemic medications such as anti-hypertensive,
antidepressants.

57. Clinical features
• Blurred vision at near
• Photophobia or a 'dazzling' effect
• Diplopia
• Micropsia: objects may appear smaller than they
are due to a false sense of distance
• Enlarged pupil.

58. Treatment
• An effort should be made to find out the cause and
try to eliminate it.
• Self-recovery occurs in drug-induced paralysis and in
diphtheric cases (once systemic disease is treated).
• Dark-glasses effective in reducing glare.
• Convex lenses for near vision, if the paralysis is
permanent.

59. Excessive accommodation
• Accommodative response is greater than the
accommodative stimulus.
• There is functional increase in tonus of ciliary muscle,
results in a constant accommodative effect.

60. 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

61. Precipitating factors
• Excessive near work done, especially in dim or
excessive illumination.
• General debility, physical or mental ill health

62. Symptoms
• Blurred vision at near is uncommon
• Blurred vision at distance
• Headaches
• Eyestrain
• Photophobia
• Difficulty changing focus from distance to near
• Diplopia

63. 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.

64. Spasm of accommodation
• Spasm of accommodation refers to exertion of
abnormally excessive accommodation.

65. 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.

66. 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.

67. 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.

68. Reference…
• BOOKS…
• Primary care optometry
• A.K.Khurana (optics and refraction)
• A.K.Khurana (squint and orthoptics)
• REFERENCE PPT…
• www.slideshare.net/RohitRao2/accommodation-of-eye
• www.slideshare.net/laxmieyeinstitute/accommodation-
35905316
• IMAGES…
• Google