This document discusses accommodation and the accommodation reflex. It defines accommodation as the eye's ability to change focus on near or distant objects. It describes the near point and far point. It explains the light reflex and visual pathway for accommodation. It details the afferent and efferent pathways for the accommodation reflex when shifting gaze from distant to near objects. It classifies different anomalies of accommodation such as insufficiency, presbyopia, excess, and spasm. It provides examples and symptoms for each anomaly.

1. By
MANIKANDAN.M
Roll no : 68
2nd year MBBS

2. Accommodation
Terms related to accommodation
Mechanism of Accommodation
Light reflex and Visual pathway
Accommodation reflex
Pathway for Accommodation reflex
Anomalies of Accommodation

3. Accommodation refers to the ability of the eye
to alter it’s focus So that clear images of either
close or distant objects can be formed on the
retina.

5.  The far point or punctum remotum is the position of an object
such that its image falls on the retina in the relaxed eye i.e. in the
absence of Accommodation.
 In emmetropic eye , the far point is at infinity.

6.  The near point or punctum proximum is the nearest point at
which an object can be clearly seen when maximum
accommodation is used.
 For a young adult with normal vision, the near point is about 25
cm.
 It increases with age > 40 years.

7. Range of Accommodation
. It is the distance between far point and near
point.

8.  The difference between the dioptric power needed to focus
at near point (P) and far point (R) is called amplitude of
accommodation(A).
A = P-R
 For example,
In a normal eye, if the near point is 10 cm ,
. P = 1/10 cm = 100/10 m = 10 D.
. In a normal eye , since the far point is at infinite distance ,
R = 0.
Amplitude of accommodation (A) = 10D.

12.  1. When light is focused on one eye, the pupils of both eyes
constrict; this is called light reflex. The pupillary constriction
occurring in the stimulated eye is called direct light reflex
and in the other eye is called consensual light reflex.
 Afferent pathway: The first order neurons from the retinal
ganglion cells project to the pre-tectal nucleus; from here
the second order neurons start and proceed to the mid-brain
Edinger-Westphal nucleus.

13.  Efferent pathway: The parasympathetic fibers of the
oculomotor nerve form the first order neurons that originate
from mid-brain Edinger-Westphal nucleus and project to the
ciliary ganglion. The second order neurons start from here
and innervate the sphincter pupillae.

16.  When sudden shift of gaze from distant to near object,the
reflex changes observed in the eye is called Accommodation
reflex .
 3 components in the accommodation reflex are :
onvergence of the eyeballs – image forms in the corresponding
points of retina.
onstriction of the pupil – increase depth of focus.
urvature of the lens increased anteriorly - increases power of lens
of the eye .
C

17. Afferent pathway
 Visual impulses from retina pass through the optic
nerve,optic chiasma, optic tract, lateral geniculate body and
optic radiation to visual cortex (area 17) of occipital lobe.

18. Center
 From occipital lobe, the association fibres carry impulses to frontal
lobe.
 The center for accommodation lies in frontal eye field that is
situated in the frontal lobe of cerebral cortex.

19. Efferent pathway
Efferent fibres to ciliary muscle and sphincter pupilae
 From area 8, the corticonuclear fibres pass via internal
capsule to Edinger-Westphal nucleus.
 From here, the preganglionic fibres pass through the third
cranial nerve to ciliary ganglion.
 Postganglionic fibres from ciliary ganglion pass via the short
ciliary nerves and supply the ciliary muscle and the
constrictor pupilae.

21. Efferent pathway
Efferent fibres to medial rectus
 Some of the fibres from frontal eye field terminate in the
somatic motor nucleus of occulomotor nerve.
 The fibres from motor nucleus supply medial rectus.

25. Classification
Decreased
Accommodation
Insufficiency
Ill-Sustained
Accommodation
Inertia Paralysis
Increased
Accommodation
Excess Spasm

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

27. • Decrease in accommodative power of lens with increasing
age, leads to
presbyopia, occurs due to:
– Age-related changes in lens:
o Decrease in elasticity of lens capsule, and
o Progressive, increase in size and hardness (sclerosis) of lens
substance which isnot easily moulded.
– Age related decline in ciliary muscle power.

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

29. ⚫The accommodative amplitude is distinctly below the lower limit of the
expected amplitude in relation to the age of the individual
⚫Similar to presbyopia
⚫Can result from systemic conditions such as diabetes mellitus, multiple
sclerosis, anemia, general physical fatigue, myasthenia gravis, trauma,
malnutrition, chronic alcoholism,etc....

30. ⚫Specific symptoms:
⚫ Blurred vision/eyestrain with NEAR visual tasks
⚫ Intermittent diplopia due to associated disturbances of convergence

31. ⚫Initial stage of true insufficiency
⚫Range is normal
⚫During prolonged near work, accommodative power weakens, the near
point gradually recedes and vision becomes blurred

32. ⚫Rare condition
⚫Difficulty in altering the range of accommodation
⚫Requires time and effort to focus a near object after looking into
distance
⚫Treatment:
⚫ Correction of refractive error
⚫ Accommodative Exercises

33. ⚫Causes:
⚫ Drug induced cycloplegia –atropine ,homatropine
⚫ Internal opthalmoplegia [paralysis of cilliary muscle & sphincter pupillae]
⚫ Neuritis associated with chronic alcoholism, diabetes
⚫ CNS infections
⚫ Head Injury
⚫Specific Symptoms:
⚫ Blurring of near vision
⚫ Photophobia [glare]

34. ⚫Self recovery occurs in drug induced paralysis
⚫Dark glasses are effective in reducing the glare
⚫Convex lenses for near vision may be prescribed

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

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

37. • Blurred vision at near isuncommon
• Blurred vision at distance
• Headaches
• Eyestrain
• Photophobia
• Difficulty changing focus from distance to near
• Diplopia

38. • 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.

39. ⚫Abnormally excessive accommodation which is out of voluntary control
of the individual
⚫Causes:
⚫ Drug induced spasm after use of strong miotics
⚫ Spasm of near reflex
⚫Specific symptoms:
⚫ Blurred vision at DISTANCE after performing near visual tasks

40. ⚫Relaxation of ciliary muscle: the most effective method of treatment is
complete ciliary paralysis with atropine

41. THANK YOU