2. PRESBYOPIA
Presbyopia is an age-related progressive loss of the
focusing power of the lens. This results in difficulty
in reading and seeing near objects.
3.
4. Causes, incidents, and risk factors
1. The focusing power of the eye, which
depends upon the inherent elasticity of the
lens, gradually decreases in old age.
2. This causes the inability to read at normal
reading distance (33 cm to 40cm).
3. People usually notice the condition around
age 40; after they realise that they need to
hold reading materials further away in order
to focus.
8. Treatment
• Presbyopia can be corrected with appropriate lenses,
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
• - Supplement this by the lens
• - allowing him a sufficient reserve of accommodation
9.
10. Key points to remember
• Presbyopic spectacle should never be prescribed mechanically
based on age
• - Lenses must be comfortable - Vision for the particular work for
which their spectacle is intended must be kept in mind.
• - Start with addition of +0.75D - Better to under correct than over
correct
• - Lenses that bring the near point closer than 28cm are rarely
tolerated.
• - Demand for higher correction than convergence should be added
with base in prism
• - Patient with early cataract can read with +3.50 D or + 4.0D
addition
• - Usual discomfort for presbyopic optical correction is due to over-
correction
11. Types of corrective spectacle for
presbyopia
1. Single vision reading glasses
2. Bifocals - where glasses are given for near and
distance
3. Trifocals - where glasses are given for
distance, intermediate and near vision
4. Varifocals - progressive addition lens
5. Monovision correction- one eye is corrected
for distance and the other eye for near
