1. Accommodation and Presbyopia Prof. Roger S. Anderson
University of Ulster, Coleraine
UCL Institute of Ophthalmology, London

2. Makes up remaining 1/3 refractive power of eye Accommodation
Role of the lens:
Makes up remaining 1/3 refractive power of eye
Accommodation
Compensation for aberrations of cornea
Accommodated o
Unaccommodated
Ciliary
muscle

3. Control of Accommodation of utmost importance in refraction.
A hypermetrope can bring the focal point
of the eye forward by accommodation.
Unaccommodated
Accommodated f
Therefore, young hyperope
may still read 6/5!
Myope can not put focal
point backwards since
ciliary muscle already relaxed.
Type of optical defect
(e.g. myopia, hyperopia, etc)
refers to position of focal
point of eye in
unaccommodated state.

4. AMPLITUDE OF ACCOMMODATION. Accommodation occurs at ~1 mth old.
More regular by 2-3 mths.
Almost adult-like by 6 mths.
Falls from maximum of 18D at 10yrs
to zero by 70 yrs.
=> PRESBYOPIA (“old eye”)
Binocular Amplitude of
Accommodation is usually
slightly greater than
monocular.
Also dependent
on pupil size. 24 22 20 18 16 14 12 10 8 6 4 2
Age (yrs)
After Donders

5. Anatomy of Accommodation: the ciliary muscle
Oblique fibres
Circular fibres
Longitudinal fibres

6. Accommodation: according to Helmholtz
Contraction of circular and longitudinal muscle fibres
results in decreased zonular tension.
Lens takes up more relaxed, less elongated state.
Increased central thickness and reduced radius of
curvature

7. Accommodation: according to Schachar
Central thinning
Decreased curvature
Aspect ratio > 0.6
Peripheral thinning
but central thickening.
Increased central
curvature.
Decreased spherical
aberration.
Aspect ratio ≤ 0.6
(“long oval”)

8. Presbyopia: the common view
Increased sclerosis of lens leads to loss of flexibility
and inability to change shape
Young
Old

9. But…. embryologically the lens is derived from surface ectoderm…..
…and keeps growing
throughout life!

11. Presbyopia: according to Schachar
As lens grows, tension on zonules slackens and ciliary muscle must
contract more to take up slack before accommodation can occur.
Young
Old

12. MEASUREMENT OF ACCOMMODATION ‘Push-up’ method (Donders 1864)
Requires the use of a small target so that
small errors of focus are detectable.
e.g. Using RAF rule:
1. Place on face with one eye occluded
2. Type moved closer until print “just goes blurred”
3. Move closer still to ensure that print goes even
more blurred
4. Move back until print “just becomes clear”
(take average)
5. Repeat for other eye and binocularly
Amp. of Accommodation = _______
Near pt. of Acc.

13. ‘Minus Lens Method’ (Sheard 1917)
1. Near point card placed at 40cm
2. Minus lenses added in -1.00D steps until blur
first noticed, which can not be cleared by straining.
A-of-A = Negative power added D
NB. In many presbyopes, A-of-A often less than 2.50D.
Must add positive lenses first to clear target. Then add negative.
Push-up method usually gives higher A-of-A than minus lens method.
Effects of:
1. Pupil size
2. Object distance (accommodative lag)
3. Fatigue
4. Accommodative Convergence (binocular)

14. Accommodation should be measured
on every patient because it may be reduced
by…..
Latent hypermetropia or accommodative spasm
Poor general health
Ocular disease
Side effect of medical treatment

15. Spectacle and Ocular Accommodationls d
d = 14mm, object at 350mm from PP
Ocular Acc. = = 2.86D
ls + d
Spectacle Acc. = = 2.98D ls
So, for an emmetrope, Spectacle Acc. > Ocular Acc.

16. Myope. e.g. -4.00DS (spec ref), d = 14mm
object at 350mm from PP
Distance Vergence
D mm
0 <-- ¥
Fsp > f’sp
-d -14
(ocular ref)
Near Vergence
D mm
Ls < ls
+Fsp
> f’sp
(Verg. at PP <
for near)
Ocular Accommodation = (-6.36) = 2.57D
Therefore, myope accommodates less wearing spectacles.

17. For Hyperope: +4.00DS (spec ref), d = 14mm
object at 350mm from PP
Distance Vergence
D mm
0 <-- ¥
Fsp > f’sp
-d -14
(ocular ref)
Near Vergence
D mm
Ls < ls
+Fsp
> f’sp
(Verg. at PP <
for near)
Ocular accommodation = = 3.21D
Therefore hyperope accommodates more wearing spectacles.

18. Calculating the Near Addition
The power of the Add depends on:
Myope or hyperope
Habitual working distance
Amplitude of Accommodation
Nature of the task
Pupil size
Not possible to employ full accommodative power for long periods,
But about 1/2 - 2/3 can be sustained.
Thus Add = (-Ls) - Amp/2
where Ls = dioptric working distance

19. Thus, if working distance = -400mm from spectacle plane
and amplitude of accommodation = 3 dioptres
Add = (2.50) = D
Need to check reading range as well.
Patients with poorer VA can obtain greater magnification
by prescribing higher Adds and making them read closer.

20. Correction Methods
Single Vision Readers
Bifocals
Varifocals
Bifocal IOL

21. Thank You