Accommodation by faslu muhammed

1. ACCOMMODATION
OPTOM FASLU MUHAMMED

2. ACCOMMODATION
Process by which the eye increases
optical power to maintain a clear image
(focus) on an object as it draws near the
eye.

3. Changes
in zonular
tension
induced by
ciliary
muscle
contraction.

4. Measured in diopters (D), which is the
reciprocal of the fixation distance.
If the fixation distance is 1 m, the
accommodation is said to be 1 D.
F=1/D

5. OCULAR STRUCTURAL CHANGES:
contraction of the ciliary muscle
tension releases on the zonular fibers
the elastic lens capsule to increase its curvature,
especially that of the front surface
lens thickness increases, a decrease in its
equatorial diameter
reduction in pupil size.

7. THEORIES OF MECHANISM OF
ACCOMMODATION:
At distance
 circular ciliary muscle
fibers relax
 increases the equatorial
circumlenticular space
 increase in zonular tension
 surfaces of the lens to
flatten and the optical
power of the lens to
decrease.
At near
• the circular muscle fibers
of the ciliary muscle
contract
•decreasing the equatorial
circumlenticular space
•reduces zonular tension
•lens round up and increase
in optical power of the lens.
Helmholtz Theory:

8. The furthest distance at which an object
can be seen clearly is called the far point
(punctum remotum).
When maximum accommodation is in
force, the nearest point which the eye can
see clearly is called the near point
(punctum proximum).
AR POINT & NEAR POINT:

10. RANGE & AMPLITUDE OF
ACCOMMODATION:
The distance between the far point and
the near point is called range of
accommodation.
The difference between the dioptric power
needed to focus at near point (P) and to
focus at far point (R) is called amplitude of
accommodation.

11. Showing the
relation between
age (x-axis) and
accommodative
amplitude in
diopters (y-axis).

12. YEARS AMPLITUDE OF
ACCOMMODATION
10 14 D
15 12 D
20 10 D
30 7 D
40 4.5 D
50 2.5 D
60 1 D
75 0

13. STIMULUS FOR ACCOMMATION:
Blurring of image
Change in target size
Proximity of the target
Chromatic aberrations
Convergence of the eyes

14. ANOMALIES OF
ACCOMODATION
Presbyopia
Cycloplegia
Insufficiency of accommodation
Ill-sustained accommodation
Inertia of accommodation
Paresis of accommodation
Excessive accommodation
Spasm of accommodation

15. I.PRESBYOPIA
Presbyopia is not an error of
refraction but, condition of physiological
insufficiency of accommodation.
Failing of near vision due to age-
related decrease in the amplitude of
accommodation or increase in punctum
proximum

16. PATHOPHYSIOLOGY OF PRESBYOPIA:
Decrease in the elasticity and
plasticity of the lens which results from;
 Age related sclerosis.
 Age related decrease in the power of
ciliary muscles.

17. AGE OF ONSET
Depends on individuals, age, occupation,
and habits.
SYMPTOMS
"I have to hold my book further away“
"my arms are not long enough“
"newspaper print is not what it used to be“
Patients complain of reading difficulty in
poor light, tired eyes after reading and
BLURRED VISION for reading.

18. MANAGEMENT:
Determination of reading addition
Objective - dynamic retinoscopy
Subjective -
(a) complete distance refraction
(b) measure amplitudes of accommodation
(c) use amplitudes as a STARTING point to
calculate an approximate reading addition

19. Add should be adjusted according to
the working distance required by the patient.

20. Rule of thumb - leave 1/3rd
accommodation in reserve
Check clarity and range. Double check with
+&- additions
PRESCRIBING MODE:
Reading glasses
Bi-focals
Tri-focals
Multi-focals- Progressive Addition Lenses

21. II.CYCLOPLEGIA
 Paralysis of the ciliary muscle, resulting in a loss
of accommodation.
 Cycloplegic drugs, including atropine,
cyclopentolate, succinylcholine, homatropine,
scopolamine and tropicamide, are indicated for
use in cycloplegic refractions and the treatment
of uveitis.
 Unlike mydriatics, which also dilate the pupil,
cycloplegic drugs inhibit focusing.

23. III. INSUFFICIENCY OF
ACCOMMODATION
The accommodative power
is significantly less than the normal
physiological limits for the patient’s age.
Differential diagnosis with presbyopia:
physiological accommodation is
normal for the patient’s age.

24. AETIOLOGY OF INSUFFICIENCY:
Premature sclerosis of lens
Malnutrition
Anaemia
P.O.A.Glaucoma (?)
SYMPTOMS OF INSUFFICIENCY
Asthenopia
Blurred vision for near work (? distance)
Over- or under-convergence

25. INVESTIGATION
Local cause
 the glaucomas (IOP, fields, AC,
fundoscopy)
 anterior uveitis (slit lamp)
Central cause
 e.g., neurological lesion (fields, motility,
pupils)
General cause
 e.g. illness

26. TREATMENT:
Treat the systemic cause
Near vision spectacle
(weakest plus lens)
Accommodation test-card exercises

27. IV. ILL-SUSTAINED
ACCOMMODATION
(Accommodation fatigue)
 Inability of the ciliary muscle to maintain
contraction while viewing a near target
with a resulting shift in accommodation
toward the far point.
 Range of accommodation is normal but
cannot be sustained for a sufficient time.

28. AETIOLOGY:
Stage of convalescence from debilitating
illness.
Stage of general tiredness.
When patient is relaxed in the bed.
SYMPTOMS:
Tiredness in near work.
Blurred near vision.

29. TREATMENT:
Occasional prescribing of temporary
appliance e.g., in case of debilitating
illness.
Improve visual hygiene (illumination and
posture).

30. V. INERTIA OF
ACCOMMODATION
Difficulty in changing focus from
distance to near and vice versa
AETIOLOGY
Prolonged close work
Ocular motor imbalance
TREATMENT
Discuss visual hygiene
Correct any ocular motor anomaly

31. VI. PARALYSIS OF
ACCOMMODATION
May be partial or total, unilateral or
bilateral.
AETIOLOGY
Congenital defects e.g., no ciliary muscle
Cycloplegics & Systemic drugs
Degenerative conditions e.g. Parkinson’s
Exogenous poisons e.g., snake bites, bee stings
III N lesion (tumour, aneurysm, haemorrhage)
Ocular disease (anterior uveitis, glaucoma)
Trauma (temporary or permanent paralysis)

32. SYMPTOMS:
Blurred of near vision
Photophobia
Micropsia
MANAGEMENT:
Self recovery in drug induced.
Dark sun glasses.
NV glass if its permanent.

33. VII. EXCESSIVE
ACCOMMODATION
Patients exerts more than normal
accommodation for performing certain near
work.
Intermittent process (not continuous).
AETIOLOGY:
Young myope/ hyperope/ astigmatism
Beginning of presbyopia
Decentered spectacle.

34. SYMPTOMS:
 Varying visual acuity
 Asthenopia
 Both near and far point are same.
TREATMENT:
 Spectacle correction after cycloplegic
refraction.
 Near work should be stopped for a
particular period of time.

35. VIII. SPASM OF
ACCOMMODATION
Tone of ciliary muscle is increased
and a constant accommodative effort is
expended by the parasympathetic nervous
system.
Pseudomyopia produced.

36. AETIOLOGY:
Spasm can be further categorised into:
Functional spasm
A response to over fatigue and "eye
strain".
Bad visual hygiene e.g., poor lighting,
glare unaccustomed work
Optical or ocular motor difficulties e.g.,
anisometropia, early presbyopia,
convergence anomalies.

37. Organic spasm
Ciliary spasm
 drug induced e.g., physostigmine,
pilocarpine, morphine, digitalis
 lesions of brain stem and OM trunk
Inflammation e.g., anterior uveitis
Trigeminal neuralgia
Others e.g., diphtheria, tooth extraction

38. TREATMENT:
Relaxation of ciliary muscle with cycloplegics.
Consider occupation, general health, mental
state
Correct refractive error and/or ocular motor
anomaly
Manage the cause.

40. ACCOMMODATIVE
ESOTROPIA
Esodeviatons due to excessive
convergence associated with accommodation
are called accommodative esotropia.
TYPES:
Refractive
(normal and hyper accommodation)
Non refractive
(hyper and hypo accommodation)

41. SIMULATED DIVERGENCE
EXCESS EXOTROPIA
 False divergence
 Distance tropia (D) is greater than near tropia
(N).
 Increased AC/A ratio.
 After accommodation relaxed D is equal to N.

42. The Accommodation of Hypermctropes
A hypermetrope requires some of his
accommodation for distant objects. Convex
lens which enables him to see distant objects
without his accommodation and his focal length
equals the distance of the near point, and we
express it by the formula
a = p + r
Patient's near point is 25 cm and 4D
accommodation for distant object.
(100/25 = 4 D.) Amplitude of accommodation :
4 D + 4 D = 8 D.

43. The Accommodation of Myopes
In a myope we have to subtract the glass
which enables him to see clearly distant
objects, from that whose focal length equals
the distance of the near point. The formula will
then be
a = p - r
Amplitude of accommodation in a myope
of 2 D., the near point being at 10 cm,
(100/10=10) 10 D,
(10D - 2D) = 8D amplitude of
accommodation.

44. ASSESSMENT OF ACCOMMODATION:
Amplitude of accommodation
(A):
(A)= P- R
P- Near point
R- Far point
Near point of accommodation is
measured with the help of RAF ruler.

45. Prince Rule:
With +3.00D sphere over the
distance correction. A standard reading
card is used and moved slowly towards
and away from the individual to locate
both the near and far points as in the push
up method.

46. ±2.00 D flip lens test The subject focuses
through one pair of lenses at an object at near
distance (40 cm). When the object is clearly
focused, a flip is quickly performed to the
other lens pair and the subject focuses through
them. This is then repeated and the number of
cycles completed in 1 minute (cpm) is
recorded as the accommodative facility.

47. Minus Lenses Test:
With full refractive correction, ask the
patient to fixate 6/60 letter. Progressively
increase the minus lens till letter becomes
more clear. This minus lens power is
equivalent to A.

48. KADAMBI RANGER (K-RANGER)
Instrument is designed to measure
Subjective Accommodation Amplitude. The
readings are directly recorded in Diopters of
Accommodation. Objective readings are
possible in combination with Dynamic
Retinoscopy.

49. Dynamic retinoscopy:
Infrared optometers, e.g., a power
refractor:
Binocular cross cylinder at near distance:
Comparing cycloplegic and manifest
refraction:

50. THANK
““ ””U