This document summarizes research on accommodation presented to the Ophthalmology Department at Al-Azhar University. It defines accommodation as the eye's ability to change refractive power and focus on objects at different distances by altering the shape of the lens. The document discusses the mechanism of accommodation, theories around how it functions including Helmholtz's relaxation theory, and types of accommodation like tonic, proximal, and reflex accommodation. It also examines anomalies of accommodation such as presbyopia, insufficiency of accommodation, and their treatment.

1. AL-AZHAR UNIVERSTY
FACULTY OF MEDICINE
OPHTHALMOLOGY DEPARTMENT
Accommodation
Under supervision
of
Prof.dr. Ahmed shafik

2. Points dicussed in this research:
1) Definition of accommodation.
2) Mechanism of accommodation.
3) Theories of accommodation.
4) Types of accommodation.
5) Anomalies of accommodation.

3. Made by all of:
1) Ebtehal Abdelnaser Ahmed.
2) Arwa Essam Hussein.
3) Esraa Ahmed fathy.
4) Esraa Elsaied Mahmoud.
5) Esraa Elashry Elashry.
6) Esraa Abu bakr Mohamed.
7) Esraa Ahmed Mohamed.
8) Esraa Gamal Eldeen Yosef.
9) Esraa Arafat Ahmed.
10) Esraa Abdelsamee Saied.
11) Esraa Ragab Abdelkhalek.
12) Esraa Salah Abdelsalam.
13) Esraa Mohamed Mohamed.

4. Accommodation
 Definition : 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.
 The mechanism of eye accommodation is not the same for all
animals.
 For example fish accommodates through the change of
position of the lens, some types of birds accommodate
through the increase of curvature of the cornea and
protraction of the human eye. As far as humans are
concerned accommodation is caused by the increased
curvature of anterior area of the eye lens while at the same
time its thickness also changes.
 Accommodation is usually the same on both eyes.

5. Accommodation in
human
it Is caused by the increased
curvature of anterior area of
the eye lens

6. Theories of mechanism of accommodation
 The exact mechanism of accommodation is not known but the
Principal fact is that ACCOMMODATION is a feature of increase
in the curvature of the lens which affects anterior surface
mainly.
 Relaxation theory of HELMHOLTZ “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.

7. Relaxation theory of HELMHOLTZ

8.  SCHACHAR’S theory
 Presbyopia is due to growth in equatorial diameter, leads to
decrease in peri lenticular space.
 Contraction of ciliary muscle cannot tense zonules and
expand lens coronally.
 SCHACHAR introduced use of scleral expansion bands (SEB).

9.  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.
 COTENARY theory
 COTENARY theory of accommodation was 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.

10. Types of Accommodation
1) 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.
2) Proximal accommodation :Is induced by the
awareness of the nearness of a target. This is independent of the
actual dioptric stimulus.
3) Reflex accommodation :Is an automatic adjustment
response to blur which is made to maintain a clear and sharp
retinal image.
4) 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.

11. Assessment of accommodation
1. Dynamic retinoscopy.
2. Subjective measurement of accommodation amplitudes with
e.g., RAF rule.
3. Facility of accommodation with "lens flippers“.
retinoscopy lens flippers

12. Anomalies of Accommodation
1) Presbyopia.
2) Insufficiency of accommodation.
3) Ill-Sustained accommodation .
4) Inertia of accommodation.
5) Paralysis of accommodation .
6) Excessive accommodation .
7) Spasm of accommodation .
8) Accommodative esotropia

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

14. 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 tion is called presbyopia

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

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

18. 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.

19. 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.

20. 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

21. Surgical Treatment
1)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

22. 2)Intraocular refractive procedure
-Refractive lens exchange
-Phakic refractive lens
-Monovision with IOLs
3)Scleral based procedures
-Anterior sclerotomy with tissue barriers
-Scleral spacing procedure
-Scleral ablation with erbium : yag laser

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

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

25. Treatment
1) Identification & treatment of any systemic cause.
2) 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.
3) If associated with convergence excess then full spherical
correction.
4) Convergence insufficiency is there, then base in prisms
can be added.
5) Prismatic correction added should bring near point of
convergence to same distance as near point of
accommodation.

26. 6) Weakest convex lenses should be prescribed, so as
to exercise and stimulate accommodation.
7) After recovery additional correction should be
made weaker and weaker from time to time.
8) 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.

27. 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

28. Clinical features
These symptoms are most commonly reported at the
end of the day:
1) Blurred vision after prolonged near work.
2)Headaches.
3)Eyestrain.
4)Fatigue, sleepiness and a loss of comprehension
with continued reading .
5)A dull 'pulling' sensation around the eye.

29. 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.

30. 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

31. Clinical features
1) Difficulty changing focus from one distance to another.
2) Headaches.
3) Eyestrain.
4) Fatigue.
5) Difficulty sustaining near tasks.
6) Blurred vision.
Treatment: correcting any refractive error and
accommodative exercises.

32. Paralysis of accommodation
 Cycloplegia, refers to complete absence of accommodation.
Causes:
1) Atropine, homatropine or other parasympatholytic drugs.
2) Internal ophthalmoplegia (paralysis of ciliary muscle and
sphincter pupillae)due to neuritis associated with diphtheria,
syphilis, diabetes, alcoholism, cerebral or meningeal diseases.
3) Complete third nerve paralysis due to intracranial or
orbital causes.
4) Systemic medications such as antihypertensive,
antidepressants.

33. Clinical features
1) Blurred vision at near.
2) Photophobia or a 'dazzling' effect.
3) Diplopia.
4) Micropsia: objects may appear smaller than they are
due to a false sense of distance.
5) Enlarged pupil.

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

35. 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.

36. Causes
1) Young hypermetropes frequently uses excessive
accommodation as a physiological adaptation.
2) Young myopes performing excessive near work,
associated with excessive convergence.
3) Astigmatic error in young patients.
4) Presbyopes in the beginning.
5) Use of improper and ill fitting spectacles.

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

38. Symptoms
1) Blurred vision at near is uncommon.
2) Blurred vision at distance.
3) Headaches.
4) Eyestrain.
5) Photophobia.
6) Difficulty changing focus from distance to near.
7) Diplopia

39. 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

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

41. Clinical features
1) Defective vision: due to induced myopia.
2) Asthenopic symptoms.
3) Precipitating factors like marked degree of muscular
imbalance, trigeminal neuralgia, a dental lesion, general
intoxication

42. Treatment
 Relaxation of ciliary muscle by atropine for 4 weeks or
more
 Prohibition of near work allow prompt recovery from
spasm of accommodation.
 Elimination of the associated causative factors to prevent
the recurrence
Anomalies of accommodation are very
common and management of these
anomalies is an integral part of
optometric practice

43. Accommodative esotropia
 Accommodative esotropia is a condition where in excessive
effort of accommodation results in an inward deviation of the
eyes.
 Most often it is caused by uncorrected Hypermetropia.
 Acquired Esotropia in a visually immature child is a day time
emergency.
 The consequences are loss of Binocular vision & onset of
amblyopia.
 The interval between the time of onset & the treatment
determines the visual outcome.
 Classification:
1)Refractive Accommodative. 2) Non- Refractive
Accommodative.
3)Partially Accommodative (Mixed).

44. Terms to remember
 Range of Accommodation: The distance between the far point
and near point ie the distance over which accommodation is effective.
 Amplitude of Accommodation: The difference between
dioptric power needed to focus at far point (at rest) and at near point (fully
accommodated).
 Relative amplitude of accommodation: The total amount
of accommodation which the eye can exert while the convergence of the
eyes is fixed.It can be positive (using concave lenses until the image blurs).
This is called positive relative accommodation (PRA)..It can be negative
(using convex lenses until the image blurs). This is negative relative
accommodation (NRA)
 Lead of Accommodation: The amount by which the
accommodative response of the eye is greater than the dioptric stimulus to
accommodation.
 Lag of Accommodation: The amount by which the
accommodative response of the eye is less than the dioptric stimulus to
accommodation

45. References:
www.Wikipedia.com.
www.slideshare.com.
 Evans BJW (1997) Pickwell’s Binocular Vision Anomalies,
Butterworth-Heinemann, Oxford.
 Duke-Elder S (1973), System of Ophthalmology, Kimpton,
London .
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