Presbyopia

• presbyopia- gradual loss of pxs ability to accomodate

• near add- additional sph power needed in addition to distance refraction for near tasks

• multifocal lenses- lens with 2 or more powers to correct vision at diff distances

• AoA- max accom that is produced by individual

Accomodation- increase in power of the eye to allow foccusing at near distances

Normal ppl: IIIrd cranial nerve innervate cil mcs action= zonule fibres relax= lens become thicker

Presbyopics: changes in visco elasticity of lens capsule + hardening of lens nucleus. Zonules fatigue and cil msc atrophy

Near triad: accom, miosis, convergence. All innervated by IIIrd nerve

• cil msc= accom

• medial recti= convergence

• iris sphincter= miosis

In presbyopics stil show convergence and miosis but not accom

Myopics: far point = nearest point a myopic can see unaccomodated and uncorrected. FP = inverse of myopia ( 3D= 0.33m)

uncorrected myopia cancels out accomodative need so presbyopic myopics can remove correction for near tasks

Hyperopes: FP is behind eye so viewing near target pushes FP further away.

Available accom is reduced. Hyperopes wear “distance” correction for near tasks.

• print looks too small or blurry

• having to hold near tasks further away

• tiredness, headaches

• having to take distance specs off for near tasks esp myopics

• struggles to see low contrast tasks

• struggles to focus at distance after near tasks

Impact

• inconvience of removing/putting specs on

• looking/feeling old

• cost of eyecare

• residual accom

• myopes cope better than hyperopes

• task demands: - small tasks size, clower WD, sustained tasks, contrast

• lighting

• height- shorter pl = shorter arms=hold things closer

• pupil size- bigger = increased ret illuminance but reduced depth of focus

• gender- females dev presbyopia earlier than males

percentage of AoA unused beacuse we wont be comfortable working at threshold for prolonged periods

• can use 2/3, 1/3 in reserve

• eg if task at 33cm…

• single vision near specs

• bifocal specs

• trifocal specs

• PPLs ( verifocals)

• degessive powered lenses

• monovision CLs - one eye for distance, one eye for near

• multifocal CLs- optics different to PPLS

• monovision refractive surgery- make eye myopic

• multifocaal IOLs

• near VA- logMAR layout, letters or symbols. add0.30 if distance halved

  • asses unaidied + specs to estimate Rx

  • assesed after distance refraction for near add.

  • if using reading chart, ask if text can be seen, dont make px read out loud ( uncomfortable)

• reading acuity = smallest target size that can be resolved-

  • requires cognitive ability + understanding of language BUT not good test bz word shape is recognised

  • MNRead Chart

• reading speed- gets worse when VA worsens. measured in words per minute

• CPS (critical print size ) is the smallest size print that can be read fluently

use RAF rule

• a subjective assessment of the near point

• use N reading block

• read off D and ask when N5 becomes blurry

• must have full distance Rx when testing

for pre-pres, compare to age norms. low values indicates uncorrected hyperopia

use Hofstetter rule, but tends to over-estimate

1. use age based assumptions at set WD. (dont prescribe, just use as starting point)

2. use available accom vs required WD. get px to sit at desk and hold chart at normal distance.

3. Estimate 0.50 for first time presbyopes or previous add as starting point.

   • listen to px: if print looks smaller/hold things further away, their add needs to go up

   • if px hold things too close, their add needs to go down

0.25 binocular flippers

Give least plus so if plus makes NV same don't give it

Duochrome should be balanced

Near Mallett unit- aim to leave px on green

When near add is 1.50D or higher

Incipient

Explain change in NV is normal and will stabilise

Discuss options for next time

Advise on lighting

Don't talk about age

Early

May need lower add

No need for intermediate

Later

Likely to have an add

No need to measure AoA

Add unlikely to change after 55