Gauri S. Shrestha, M.Optom, FIACLECo-Ordinator

B.Optom ProgramInstitute of Medicine

Dipak Sah, B.optom final Year

Accommodation Age normal amplitude of accommodation Range of Accommodation Near vision

Gradual decrease in amplitude of accommodation as expected with age

The onset is usually anticipated by age 40 years or amplitude of accommodation tends to drop below 5.00D.

Old aged eye ( आँ�खा� बु�ढो� भयो�)

Age Functional effect

Hyperopia Additional accommodative demand

Occupation Near vision demands

Gender Earlier onset in females (short stature, menopause)

Systemic disease Diabetes mellitus, multiple sclerosis, cardiovascular accident

Drugs alcohol, chlorpromazine, hydrochlorothiazide, antianxiety agents, antidepressants

Geographic factors

Proximity to the equator (higher average annual temperatures, greater exposure to ultraviolet radiation)

Iatrogenic factors laser photocoagulation; intraocular surgery

Incipient presbyopia Premature presbyopia Manifest presbyopia Absolute presbyopia

Incipient presbyopia◦Beginning stage of presbyopia when symptoms or difficulty are first encountered in near vision.

◦Patient will have more difficulty in dim illumination while can do well in bright illumination.

Premature presbyopia◦Presbyopia occuring at an earlier age than expected for normal population.

◦Usually associated with ocular diseases, nutritional deficiencies or ingestion of certain drugs.

Manifest presbyopia◦Presbyopia with some amplitude of accommodation present.

Absolute presbyopia◦Presbyopia with amplitude of accommodation completely absent.

“My arms are not long enough to see up close anymore”

Blurring of near vision Drowsiness after a short period of near work. Headache

Biomechanical Biochemical Physiological

Decrease in elasticity of lens material (44%)

Decreased elasticity of capsule Increase in size of lens Anterior shifting of the equatorial fibers

Increased disulphide bondings between the lens material and the capsule.

Increase in size Alteration of the lens material (Not any sclerosis)

HYPEROPES

EMMETROPES

MYOPES

Half in reserve for distance greater than 40 cm

One third in reserve for working distance less than 40 cm

Addition based on amplitude of accommodation.

Tentative addition based on age. Plus build-up method. Bichrome method. Cross-cylinder method. Relative accommodation method. Dynamic Retinoscopy method.

Amplitude of accommodation decreases with age..◦Presbyopia is reported when NPA exceeds 8 inches

(22cm) ie AA = 4.50D (Donders)

Presbyopia exists when amplitude of accommodation is less than 5D (Morgan).

Working distance (WD)= 40cmRAF (Amp accommodation) = 2.00D

What should be the near addition ???Accommodation required for WD = 2.50 DAccommodation in Reserve = 1.00DAmount of accommodation left = 1.00DAmount of Near addition = (2.50 –1.00)

= 1.50D

Example 2

Working distance (WD) = 25 cmRAF (Amp accommodation) = 1.50D

What should be the near addition ??? Accommodation needed at WD = 4.00DAmplitude held in reserve = 0.50DAmplitude of accommodation left =

1.00DAmount of near addition = (4.00-1.00)

= 3.00D

Amplitude of accommodation to age (Hofstetter)◦Maximum = 25.0 – 0.4 (age)◦Probable = 18.5 – 0.3 (age)◦Minimum = 15.0 – 0.25 (age)

◦Amount of near add calculated by holding certain amount of accommodation in reserve

Rule of 4s ( ४ को� नि�योम)= 4*4-age/4

Age of Range (Years)

Minimum Expected Amplitude (Diopter)

Range of Near Add in Diopter for 40 cm.

40 to 44 5.00 to 4.00 +0.75 to +1.00

45 to 49 3.75 to 2.75 +1.00 to +1.50

50 to 54 2.50 to 1.50 +1.50 to +2.00

55 to 59 1.25 to 0.25 +2.00 to +2.25

60 and over 0 +2.25 to +2.50

Can be done binocularly or monocularly Plus lenses are increased in steps of 0.25D to the

amount necessary to read the desired letters at a customary working distance.

Monocular build-up usually lands in more amount of near addition.

Chromatic aberration In presbyopic patients red

& green are focused behind the retina with red farther away.

Green appears clear. Plus lenses are added until

both red & green appear equally clear

Can be combined this technique with tentative add method/amplitude method etc

Bichromatic method:◦Patient with Rx for DV, ◦Bichrome test at habitual distance in

NV◦Ask patient which background

letters are more clear Green-add plus, Red-remove plus until he/she sees letters equally

clear in both

A near point grid is presented to the patient at their customary working distance.

Illumination on the target should be diffuse.

Plus lenses are added until patient sees the lines clearly

Crossed cylinder (±0.50D) with their minus axes vertical are placed before the patient’s eyes.

Patient is asked to report which sets of lines running across or up & down appear clearer, sharper, blacker

Cross cylinder creates artificial astigmatism with an interval of sturm of 1D

If patient accommodates exactly for the target, both sets of lines should be equally clear.

If patient under-accommodates, the horizontal lines will appear clear.

Add positive lenses until verticle and horizontal lines are seen equally clearly◦Can be done monocularly or binocularly

Measure of lenses to blur letters of N6. Patient is provided with plus lenses determined by

bichrome method/add based on age/Amplitude method

Determine◦Minus lens to blur (PRA)◦Plus lens to blur (NRA)

Near add = NRA+PRA/2

The addition is 1.00 (say) We add minus lenses until blur and the value be (1-

0.5)= +0.50 D We add plus lenses and the value be +2.00 D= (1+1) Then the final add is (+0.50+2.0)/2=

1.25D

Determine lag of accommodation (dynamic retinoscopy)

Reduce amount of lag by +0.50 to +0.75D

Prescribe remaining as addition for near

Method Procedure Advantage

40 cm fused (binocular) cross-cylinder.

Compare manifest refraction to plus value on 40 cm fused cross-cylinder, add is the plus over the manifest refraction.

In older patient with limited accommodative amplitude and accommodative flexibility.

One-half accommodative amplitude

Accommodative amplitude determined from PRA, add based on allowing the patient to use only one-half of available amplitude at the desired reading distance.

Good for early presbyopia with slightly reduced amplitude of accommodation account for the patient’s desired reading distance.

PRA/NRA Plus add is the value that puts the total near power in the middle of the PRA/NRA blur points.

Add is the middle of the Accommodative range from PRA to NRA

Plus lens(Convex

lens)

Thank YOU