METHODS OF

PRESBYOPIC

CORRECTION

Presented by: Muhammad Amin Athar

Definition:“The refractive condition that occur when the near point of accomodation has reached to the point that near work is difficult or impossible without the use of corrective lenses.”

METHODS OF CORRECTION1. Dynamic Retinoscopy.2. Determining the Tentative

Addition.3. Amplitude of accomodation.4. Age expected addition.5. Fused cross Cylinder.6. Near Duochrome.7. Negative and positive relative

accomodation.

Dynamic Retinoscopy.

In this procedure, the best distance correction was placed on the trial frame and the patient was instructed to try to keep clear a line of optotypes of N6 presented at 40 cm or head of retinoscope

Calculation: W.D- neutral point= near add

40cm-1.00, 2.50-1.00=+1.50

Determining the Tentative Addition

Subjectively the gradual increase of +0.25D lenses after distance correction for near point, keep increasing the power gradually untill the targetted (N6) is clear.

Age Expected correctionAGE ADDITION

40 years +1.00Ds43 years +1.25Ds45 years +1.50Ds48years +1.75Ds50 years +2.00Ds55 years +2.25Ds60 years +2.50Ds

Amplitude of Accomodation.

Determine the amount of accomodation required for the patient’s near-vision tasks For Exapmle:Reading at 40cm would require 2.50D of accomodation.

Calculation : Accomodation required 40cm is :

D=1/fD=100/40cm

D= 2.50D Keep Reserve the one-half:

2.50-1/2(2.50)2.50-1.25

Near addition is +1.25D

The reserve allows the movement of objects closer and far with patients comfort.

Attention…! Real Test…

Fused cross Cylinder. Adding plus lenses until the horizontal and

vertical lines on the cross cylinder grid subjectively appeared equally clear.

With the distance correction placed in the trial frame, align the JCC on trial frame at 45 (red line align at 90) the subject is instructed to identify which lines appeared most sharp.

Horizontal lines were considered to beclearer (under correct, add plus lenses binocularly in 0.25 D steps until equality was reached between the two

Near Duochrome For presbyopic patients, both red

and green will focus behind the retina

Plus lenses are added until the letters on the red background become as clear as on the green.

Simply:If GREEN is sharp(under correct

add plus lenses)If RED is sharp(over correct

decrease plus lenses)

Negative and Positive relative Accomodation

The tentative addition was determined as the lens that placed the accommodative demand in the middle of the range of relative accommodation (NRA-PRA/2). Total relative accommodation was determined by finding the range between the least plus (PRA) and most plus (NRA).

For example: +3.00-(+1.00)=+2.00 +2.00/2=+1D