Accommodation

1. Theories of Accommodation
and it’s Anomalies
Presenter: Dr. Rujuta Gore
Moderator: Dr. Atul Seth

2.  A dioptric change in the power of the eye to see clearly

3. Relaxation Theory of Helmholtz
 Proposed by Thomas Young
 Elaborated by Hermann von Helmholtz
 Most widely accepted

4. Relaxation Theory of Helmholtz
eye is at rest and focused for distance
ciliary muscle is relaxed
eye makes an effort to focus on a near object
ciliary muscle contracts
bulk of the anterior ciliary body moves
forward
release in tension on the zonular fibres
elastic capsule moulds the lens into a
spherical form

5. Relaxation Theory of Helmholtz
 Increase in surface curvatures causes an increase in optical
power of the lens and therefore an increase in power of
the eye

6. Helmholtz’s Theory: Disaccommodation
ciliary muscle contraction ceases
posterior zonular fibres pull the ciliary muscle
backward
increases tension on the zonular fibres
increase in lens diameter, decrease in lens thickness
and a flattening of the anterior and posterior lens
surface curvatures
decrease in optical power

7. Shortcomings of Helmholtz’s Theory
 Since the equatorial diameter increases with age, zonules
should relax, and power of the crystalline lens should
increase.
 Lens should become unstable

8. Schachar’s Theory
 Proposed by Ronald Schachar
 Alternative theory
 Contradicts the classical Helmholtz’s mechanism

9. Schachar’s Theory
ciliary muscle contracts
equatorial zonular tension is increased
anterior and posterior zonules are
simultaneously relaxed
central surfaces of the lens steepen
peripheral surfaces of the lens flatten

10. Helmholtz’s and Schachar’s Theory

11. Shortcomings of Schachar’s Theory
 Based on his theory, Schachar introduced a new surgery in
1992 i.e. the use of scleral expansion bands to increase the
distance between the lens equator and ciliary muscle.
 Poor results of this surgery challenged the validity of his
theory

12. Catenary (hydraulic suspension) Theory
 Proposed by Coleman DJ in 1970
 Demonstrated in 2001
 Explains the precise anatomical reproducible shape of the
lens in accommodated state
 Assumption : the lens, zonule and anterior vitreous
comprise a diaphragm between the anterior and vitreous
chambers of the eye

13. Catenary (hydraulic suspension) Theory
 What is “catenary”?

14. Catenary (hydraulic suspension) Theory
ciliary muscle contracts
initiates a pressure gradient between
the vitreous and aqueous
compartments
anterior capsule and the zonule form
a trampoline shape or hammock
shaped surface
steep radius of curvature in the center
of the lens with slight flattening of
the peripheral anterior lens

15. Clinical Assessment
 Reading progressively smaller letters at near
 NPA using RAF rule
 Relative positive accommodation using minus lenses
 Accommodative flipper test using paired +/– lenses
 Dynamic Retinoscopy
 Dynamic Distant Direct Ophthalmoscopy

16.  TERMS TO REMEMBER:
 Range of Accommodation
 Amplitude of Accommodation
 Relative Amplitude of Accommodation
 Lead
 Lag
 Facility of Accommodation

17.  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)

18.  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)

19.  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

20. Clinical Assessment
 Measurement of NPA:
 It is the closest point at which an object can be seen clearly
 Also called “near point” or “punctum proximum”
 Measured with the RAF rule

21. DDDO
 An emmetropic eye has “with” movement on retinoscopy
and “superior” crescent on DDDO while 1D myopia (due
to accommodation) shows “no movement” on retinoscopy
and disappearance of superior crescent on DDDO
 DDDO is an easier test than DR
 Location of bright crescent moving from top to the
bottom of the pupil is probably easier to recognize[Fig. 5]
than change in the movement of the retinoscopy reflex
(“with” movement to the “against” movement), more so
when the pupils are dilated

22. Anomalies of Accommodation
 General symptoms:
 Problems are longstanding
 Intermittently blurred vision
 Eyestrain and/or headache with visual tasks
 Fatigue/sleepiness with visual tasks
 Inattentiveness over time

23. Anomalies of Accommodation
Classification
Decreased
Accommodation
Insufficiency
Ill-Sustained
Accommodation
Inertia Paralysis
Increased
Accommodation
Excess Spasm

24. Accommodation Insufficiency
 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,
convalescence from debilitating illnesses and chronic
alcoholism

25. Accommodation Insufficiency
 Specific symptoms:
 Blurred vision/eyestrain with NEAR visual tasks
 Intermittent diplopia due to associated disturbances of
convergence
 Examination findings
 Reduced amplitude of accommodation
 Higher than normal lag of accommodation
 Difficulty clearing -2.00 D lenses on monocular and
binocular accommodative facility testing
 PRA (positive relative accommodation) lower than -1.50

26.  Causes of Unilateral Accommodation Failure:
 Congenital unilateral third nerve palsy
 Transient, post traumatic, accommodation failure associated with
traumatic mydriasis
 Causes of Bilateral Accommodation Failure:
 Cortical vision impairment
 Foveal hypoplasia (albinism, aniridia)
 Down syndrome
 Iso-ametropic amblyopia
 Ectopia lentis
 Macular degeneration
 Nanophthalmos
 Near vision palsy
Rule out…

27. Treatment: Accommodation Insufficiency
 Spectacle correction
 For near- weakest convex lenses should be prescribed
 If there is associated convergence insufficiency base out
prism may be added to patient comfort
 In cases with convergence excess full spherical correction
should be prescribed
 ACCOMMODATION TEST-CARD EXERCISE

28.  Vision Therapy: To stimulate accommodation mono-
ocularly
 Small print targets that are slowly moved CLOSER to the eye
 Reading print through MINUS lenses (gradually increasing
the power) using “Monocular minus lens rock”
 Monocular lens flippers
 Monocular minus lens clear/blur/clear (for fine voluntary
control)
 Binocular lens flippers
Treatment: Accommodation Insufficiency

29. Ill-sustained Accommodation
 Initial stage of true insufficiency
 Range is normal
 During prolonged near work, accommodative power
weakens, the near point gradually recedes and vision
becomes blurred

30. Inertia of Accommodation
 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

31. Paralysis of Accommodation
 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]

32. Treatment: Paralysis of Accommodation
 Self recovery occurs in drug induced paralysis
 Dark glasses are effective in reducing the glare
 Convex lenses for near vision may be prescribed

33. Accommodative Excess

34. Treatment: Accommodative Excess
 Prescribing lenses
 Distance lens prescription
 Added plus lenses are not usually accepted for near work
 Vision Therapy: To relax accommodation monocularly
 Small print targets slowly moved AWAY from the eye
 Reading print through PLUS lenses (gradually increasing the
power)

35. Spasm of Accommodation
 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

36. Spasm of Accommodation
 Specific symptoms:
 Blurred vision at DISTANCE after performing near visual
tasks
 Examination findings:
 Lead of accommodation
 Difficulty clearing +2.00 D. lenses on monocular and
binocular accommodative facility testing
 NRA lower than +1.50

37. Treatment: Spasm of Accommodation
 Relaxation of ciliary muscle: the most effective method of
treatment is complete ciliary paralysis with atropine

38. Accommodative Infacility
 Specific symptoms:
 Blurred vision when CHANGING focus far → near and near
→ far
 Examination findings:
 Difficulty clearing both +2.00 and -2.00 D. lenses on
monocular and binocular accommodative facility testing
 PRA lower than -1.50 and NRA lower than +1.50

39. Treatment: Accommodative Infacility
 Vision Therapy: to stimulate/relax accommodation
monocularly
 Alternately focusing on small print targets at near and far
(with the near target slowly moved closer to the eye).
 Reading near print through alternating PLUS and MINUS
lenses (gradually increasing the power)