Small ppt ,easy to understand.Has been used to teach students in the department of Ophthalmology.

1. Definition
Inability to read the books at the normal
reading distance of 33cm.
The near point recedes beyond the arm’s
length.

2. Causes
Decrease of accommodative power
Nuclear sclerosis- Lens become harder

3. Contd.

4. The lens in accommodation

5. Some important points
Average distance for near work is 28-30cm.
When the amplitude of accommodation is less
then 3.0Ds Presbyopia is said to start.
Comfort demands that about 1/3 of
accommodation to be kept in reserve
In emmetropic presbyopia occurs at 40 – 45 years
of age in foreign countries, 38 – 40 in India.
Accommodation must be supplemented by convex
lenses

6. Symptoms
Trouble is in the evening, when light is dim, and
pupils are dilated.
Likes to read in brilliant illumination when the
pupils will be forced to contract.
Visual failure
Eye strain
The ciliary muscle working near its limit becomes
fatigued and accommodation effect strained in
excess of the convergence-giving rise to distress.
Headache
Eyes feels tired & ache.

7. Treatment
Provide the patient with the appropriated convex lens
, so that his accommodation is reinforced and the near
point is brought within the useful working distance.
Know the working distance of the patient for proper
addition.
Refraction
Determine the amplitude of accommodation
1/3 of accommodation is kept in
reserve
Supplement this by lens

8. Scientific calculation of
presbyopic correction
Example
Emmetropic working distance :– 25cm
Required amplitude of accommodation :–
4D(100/25)
Near point receded at 50cm (WD)
His accommodation :– 100/50 = 2D
Keep 1/3 reserve for comfort
Available accommodation :– 2/3 of the amplitude
= 1.3D
Required lens power :– (4 –1.3D) = 2.7Ds

9. Points to remember
Presbyopic spectacle should never be prescribed
mechanically based on age
Lenses must be serviceable and comfortable, not
necessarily the clearest.
Vision for the particular work for which their
spectacle is intended must be kept in the mind.
Start with an addition of +0.75D.
Better to under correct than over correct
Lenses that bring the near point closer than 28cm
is rarely tolerated.

10. Contd.
Patient with early cataract can read with
+3.5D or +4.0D addition
Usual discomfort for presbyopic optical
correction is due to over correction