Near Add Determination

What can cause accommodative insufficiency?

• Long-standing problems

• an acute problem due to a recent increase in myopic correction

• could be pharmacologically induced (adhd meds or atropine for myopia management)

When do people get presbyopia?

Typically 40s

What is the rule of thumb for subjective amplitudes?

Pts want ½ of their amplitude in reserve to see comfortably.

What is Hofstetter’s formula for minimum amplitude of accommodation?

18.5 – (0.3 × age) in diopters.

Based on Hofstetter’s formulat, what is the expected age when Add is needed?

> 45 yrs of age. 

What factors contributes to the first age and power of giving a pt add?

• Arm length/near demands

• climate/ solar radiation (more UV ~ need add) 

• Systemic health

• refractive error

• ocular aberrations

• pupil size/ depth of focus 

What is the typical near Add power for a 40 cm working distance by age?

• 40 yrs: +1.00 D

• 45 yrs: +1.25 D

• 48 yrs: +1.50 D

• 50 yrs: +1.75 D

• 52 yrs: +2.00 D

• 55 yrs: +2.25 D

• 60+ yrs: +2.50 D

What is Binocular Fused cross cylinder (BCC)?

A test that is used for both presbyopes and non-presbyopes. In presbyopes, we are determining tentative add power. In non-presbyopes, we are measuring accuracy of accomodation. 

How is BCC set up?

• Dim the room lights 

• Add +2.00 DS OU 

• Aux wheel in phoropter has a cross cylinder lens for each eye labeled +0.50/-0.50 

• Set of vertical lines and horizontal lines 40 cm away

• If the vertical lines are better, decrease plus. If the horizontal lines are better, increase plus. 

What is the optimal balance for the near range of clear vision when refining the Add?

1/3 in front and 2/3 behind the working distance (40 cm).

What does it mean if the near range of clear vision is too heavy in front?

Tentative Add is too strong (e.g., ½ in front and ½ behind).

What does it mean if the near range of clear vision is too heavy behind?

Tentative Add is too weak.

What does NRA stand for and what does it measure?

Negative Relative Accommodation — measures the ability to relax accommodation from a specified viewing distance (40 cm) using plus lenses.

What does PRA stand for and what does it measure?

Positive Relative Accommodation — measures the ability to increase accommodation from a specified viewing distance (40 cm) using minus lenses.

Which lens power is used for NRA and PRA?

NRA: Plus power (relaxes accommodation)

PRA: Minus power (stimulates accommodation)

In NRA/PRA testing, what does NRA represent for a non-absolute presbyope?

How much accommodation the patient is exerting for the 40 cm demand.

In NRA/PRA testing, what does PRA represent for a non-absolute presbyope?

How much additional accommodation the patient can exert beyond the 40 cm demand.

How do you refine the tentative near Add using NRA and PRA findings?

• Perform NRA first (plus lenses to relax accommodation), then PRA (minus lenses to stimulate accommodation) at 40 cm.

• Record NET NRA and PRA values (first sustained blur).

• If NRA and PRA are unequal, adjust Add:

  • Method 1 (Diopter math):

    (NRA + PRA) ÷ 2\] → Add this to tentative Add. Example: NRA +1.00, PRA –0.50 → (+1.00 + –0.50) ÷ 2 = +0.25 → New Add = Tentative Add + 0.25.

  • Method 2 (Clicks): Balance plus/minus clicks; each click = 0.25 D.

• Demonstrate options (tentative Add vs adjusted Add) and let patient choose.

What should you do if you give a patient a trial frame with their near prescription?

Warn them that things will look horrible through it if they look far away.

What are common spectacle lens options for near Add power in presbyopia?

• Flat-top bifocals

• Round bifocals

• Executive bifocals

• Trifocals

• Progressive addition lenses (PALs)

• Single vision readers

What are common options for managing presbyopia besides spectacles?

Contact lens options:

• Aspheric lenses (early presbyopes)

• Multifocal (bifocal) contact lenses

• Translating bifocal RGPs

• Monovision

Surgical options:

• Cataract surgery or clear lens extraction

• Monovision

• Multifocal IOLs

• Accommodating IOLs

• LASIK for monovision (possible)