Near Add Determination

What is the difference between testing near VA after refraction, compared to entrance near VAs?

Entrance near VAs are binocular

Refraction near VAs are monocular

When do you test refraction near VAs binocularly?

If one or both eyes were not 20/20

If your patient is not presbyopic, how would you expect their refraction near acuities to compare to their distance acuities?

Should be the same (ie. 20/20 at distance should also have 20/20 at near)

What are the potential causes of manifest refraction near acuity being worse than manifest refraction distance acuities?

Presbyopia

Accommodative insufficiency

Vergence issues

What is presbyopia?

when the amplitude of accommodation is insufficient to permit sustained, clear, and comfortable vision at customary near working distances

When will a patient theoretically get presbyopia?

When their amplitude of accommodation is less than that required for their working distance

Who gets presbyopia?

EVERYBODY

When do people typically get presbyopia?

Typically in their 40s

Why do people get presbyopia?

Still not definitively known, but lens thickness and flexibility play a big role 

What additional factors are involved in when a patient will get presbyopia?

Depth of focus

Pupil diameter

Print size

What is a rule of thumb for subjective amplitudes?

Patients want ½ of their amplitude ‘in reserve’…meaning that 5D of subjective amplitude is necessary to function comfortably at 40cm (2.50 D demand).

Why does the rule of thumb for subjective amplitudes generally work?

A comparison of objective and subjective amplitudes for the pre-presbyopic and presbyopic age range show that the subjective amplitude is almost twice that of the objective.

Based on the ‘half in reserve’ theory, what age would the average patient need an Add for 40cm?

1. Have to use Hofstetter’s formula: 18.5 - 0.3 x age

2. For a 40cm demand (2.50 D) the patient would need at least 5D of subjective amplitude

3. 18.5 - 0.3 x age = 5D and solving for age: (18.5 - 5)/0.3 = 45 years old

4. Based on subjective push-up, patients are expected to need an Add, on average, at

   >45 years of age

What are the symptoms of presbyopia?

Blurry vision at near (difficulty with small print, worsening complaints at end of day, fluctuation clarity of near vision)

Eyestrain

Tired eyes or feelings sleepy doing near work

Difficulty seeing at near in low light conditions

What ways do patients try to adapt to their presbyopia?

Hold their reading material far away

Increase their font size

Increase their illumination for reading

Avoid near work

What are ways to determine tentative add?

Age determination

Plus build up

Binocular fused crossed cylinder at near (BCC)

What are ways to refine the tentative add?

NRA/PRA

Near range of clear vision

trial frame + test drive

Age determination is always a blank.

TENTATIVE add power

Why is age determination always a tentative add power?

There are great inter-individual variations among the different age groups and onset of presbyopia because of things like: arm length/near demands, climate/solar radiaiton, systemic health, refractive error, ocular aberrations, and pupil size/depth of focus

What is the tentative add using age determination for a 40 year old?

0 D

What is the tentative add using age determination for a 45 year old?

+1.00D

What is the tentative add using age determination for a 48 year old?

+1.25D

What is the tentative add using age determination for a 50 year old?

+1.50D

What is the tentative add using age determination for a 52 year old?

+1.75D

What is the tentative add using age determination for a 55 year old?

+2.00D

What is the tentative add using age determination for a 60 year old?

+2.25D

What is the tentative add using age determination for a 63 year old?

+2.50D

What is the tentative add using age determination for a 65 year old?

+2.50D

Do we go beyond a +2.50 add power? 

Not typically because of the typical working distance being 40cm (so if pt has a closer working distance, will have to change the add)

What are the testing conditions when doing age determination tentative add?

Phoropter with near PDs pushed in, near card at 40cm, stand lamp illuminating target

If you put in add using age determination and patient isn't reading 20/20, what do you do?

Try additional plus

What is plus build up?

add plus binocularly in +0.25D steps starting from the manifest distance refraction while patient looks at 20/20 (or larger if reduced VA) row of letters on 40cm near card

What are the testing conditions when doing plus build up?

Phoropter with near PDs pushed in, near card at 40cm, stand lamp illuminating target

How do you perform the plus build up?

1. Direct patients attention to 20/20 row and tell them to let you know when it becomes clear and easy to read

2. Add plus equally over both eyes and pause for a few seconds after each +0.25 D step to give the patient time to evaluate 

3. If the patient tells you they can just begin to read the 20/20, add another click

   of plus to see if it makes it even more clear (i.e. push the plus).

What is important to keep in mind when performing the plus build-up method?

If the patient’s best corrected distance acuity was not 20/20, you will need to direct their attention to a larger size on the near acuity card that matches their distance threshold 

What tentative add test can be used for presbyopes and non-prebyopes?

Binocular fused cross cylinder (BCC)

What does the binocular fused crossed cylinder test for in non-presbyopes?

Accuracy of accommodation

What does the binocular fused crossed cylinder test for in presbyopes?

Tentative add power

What lens power is used for binocular fused crossed cylinder (BCC)?

+0.50-1.00x090 (using the +0.5/-0.5 option on the auxiliary wheel in the phoropter)

What is the target for binocular fused crossed cylinder (BCC)?

Set of vertical and horizontal lines

What does the target look like for binocular fused crossed cylinder (BCC) with the cross cyl lens in place (without +2.00D add)

Horizontal lines are sharper and darker

Where are the horizontal lines focused for binocular fused crossed cylinder (BCC) with cross cyl lens in place?

Horizontal lines are focused in front of the vertical lines

What is the Goal of binocular fused crossed cylinder (BCC)?

Add plus until both horizontal and vertical lines look equally clear

What are the testing conditions for binocular fused crossed cylinder (BCC)?

Dim room illumination, stand lamp directed away from target

BCC target set at 40cm

Phoropter near PDs in

Distance refraction with an added +2.00 D and +/-0.50 cross cyl over each eye 

Why do we add +2.00D when doing binocular fused crossed cylinder (BCC)??

To bring both line foci in front of the retina

What does the target look like for binocular fused crossed cylinder (BCC) with cross cyl lens and +2.00D add in?

Vertical lines will be sharper/darker

Why is binocular fused crossed cylinder (BCC) done in dim illumination?

To keep the pupil big, because a small pupil increases depth of focus

What do you do if the patient responds that the vertical lines look better during binocular fused crossed cylinder (BCC)??

Decrease the plus (add minus)

What do you do if the patient responds that the horizontal lines look better during binocular fused crossed cylinder (BCC)??

Add more plus

What do you do if the patient reports that there is never a time where both the lines look equal during binocular fused crossed cylinder (BCC)??

Leave it at the first horizontal response (first lens that makes the horizontal lines look better)

What does the amount of plus needed to equalize the lines during binocular fused crossed cylinder (BCC) give us?

Tentative add power (ex. if started with +2.00 D and patient chose vertical lines twice and then said both horizontal and vertical lines looked equal, then +1.50 is the tentative add power because that is what is left)

What do you want the end result to be when doing near range of clear vision?

total range:

1/3 in front of 40cm

2/3 behind 40cm

Why do patients typically prefer to have 1/3 of their total range of clear vision in front

and 2/3 in back?

This is because intermediate distance viewing is more common than shortened working distance viewing.

What does the near range of clear vision test involve for refining the add? 

Quantifying the near range of clear vision and then evaluating the balance in front and behind the working distance (40cm) to determine if the tentative Add should be increased or decreased.

What is the near range of clear vision?

The range closer than 40cm and a range further than 40cm for which the target remains clear

What are the testing conditions for near range of clear vision?

Tentative add + near PD in phoropter

Near acuity card @40cm with stand lamp on it

What are the steps for the near range of clear vision test?

1. put in tentative add and make sure the patient can read 20/20 clearly at 40cm

2. Move the card closer until the patient reports blur + note the distance (in cm)

3. Move the card back until the line is clear again

4. Have the patient look at 20/30 at 40cm

5. Move the card farther away until patient reports blur + record the distance

What is important to be certain of for the near range of clear vision test? 

Be certain that the near lamp illuminates the target throughout this entire test. You do not want the card to move into a shadow. 

How do you document near range of clear vision?

Document the entire range over which the vision was clear.

Example: Near Range of Clear Vision with +2.00 ADD = 30 cm to 60 cm.

Does a Near Range of Clear Vision with +2.00 ADD = 30 cm to 60 cm follow the rule of thumb?

Yes, there is 10cm in front (10cm/30cm = 1/3) and 20cm in back (20/30 = 2/3)

What do you do if a patient has 1/2 front and 1/2 behind in near range of clear vision? What does that mean about the tentative add? 

The balance is too heavy in the front, decrease the add and do additional refinement test; Tentative add is likely too strong 

What do you do if a patient has 1/4 in front and 3/4 behind in near range of clear vision? What does that mean about the tentative add? 

The balance is too heavy, increase the add and do additional refinement test; Tentative add is likely too weak 

What do you do if a patient has 1/3 in front and 2/3 behind in near range of clear vision?

Report that as their add

What is negative relative accommodation (NRA)?

The plus power added to relax accommodation at a certain viewing distance (40cm)

What is positive relative accommodation (PRA)?

The minus power added to increase accommodation at a certain viewing distance (40cm)

What does NRA measure?

How much accommodation the patient is exerting at 40cm (with tentative add in place if presbyopic)

What does PRA measure?

How much extra the patient could accommodate on top of what they already exerted for 40cm (with tentative add in place if presbyopic)

What are the testing conditions for NRA/PRA?

Tentative add in phoropter with PD levers in

Stand lamp on 40cm near target (keep these words clear)

What do you always start with when doing NRA/PRA?

NRA

What is your net NRA finding?

The amount of clicks of plus it takes for patient to get sustained blur (+0.25 steps)

Wha is your net PRA finding?

Amount of clicks of minus to obtain first sustained blur (-0.25 steps)

What is an ideal end result with NRA/PRA?

equal/opposite powers for NRA/PRA (ex: +0.75/-0.75)

Why do you want the NRA/PRA to be equal?

So the patient has some accommodation to relax to see things further than 40cm, and still has some accommodation they can exert to see things closer than 40cm

What does it mean if there is more NRA than PRA?

Add is too weak

What does it mean if there is more PRA than NRA?

Add is too strong

What do you do if the NRA/PRA findings are unequal?

Take, (NRA + PRA)/2, and add (or subtract) that to your tentative add

What do you do if the NRA/PRA are separated by an odd number of clicks (can't divide by 2)?

Demonstrate the +0.25/-0.25 difference to the patient and let them select

When are good examples to use a trial frame evaluation?

If considering a change of refraction

If giving a first time add

If giving a rx for a specific task

What must you warn the patient of if doing a trial frame refraction for refining the add?

Distance vision will look horrible + blurry

What should you do if patient is giving immediate negative feedback about the comfortability of the add in the trial frame?

1. Show additional options by holding loose lenses over the trial frame (-0.25 OU

or +0.25 OU) to compare with the power in the trial frame.

2. Encourage the patient to explore the range they can move their material and

still see comfortably with each of the options.

What are the spec options for presbyopia?

Flat, round top, or executive bifocals

Trifocals

PALs

Single vision readers

What are the CL options for presbyopia?

Aspheric

Multifocal CL

Translation bifocal RGPs

Monovision

What are the surgical options for presbyopia?

Cataract surgery or clear lens extraction with:

Monovision, multicfocal or accommodating IOLs

Lasik for monovision

What presbyopic CL option should only be used for very early presbyopes?

Aspheric CLs