8 - astigmatism and presbyopia

When is correcting astigmatism in glasses a problem?

1. if there is significant meridian by meridian anisometropia

2. if the axes are oblique

What are the issues with uncorrected astigmatism?

1. blur

2. headache

3. strain

What are the issues with spec corrected astigmatism?

nothing

OR:

prismatic effects when looking away from optical center and anisekonia

What is the best optical correction for astigmatism?

contact lenses

What must you do when trial framing a prescription with astigmatism?

have the patient walk with the glasses

What can you do if full astigmatism correction is not accepted?

1. eikonic lens design (bitoric)

2. decrease the cyl in the higher cyl lens → maintain SE

3. rotate the axis toward 90 or 180

4. increasing rx over time if needed

what are the signs and symptoms of presbyopia?

1. reduced VA at near

2. blur at near, worse under reduced illumination

3. worse when fatigued or ill

What is the way to determine an add for presbyopia?

age expected add

What is the worse test for presbyopia (but still good)?

1. dynamic retinoscopy

2. amplitudes of accommodation

what is the formula for add based on age (tentative add)?

+0.75 + (0.1 for every year over age of 40)

What is the best way to gauge acceptance of a near add?

demo-ing add → especially good if you demo overcurrent glasses

What is the effective add?

the actual add the patient is receiving after factoring in RE

What is the effective add formula?

EA = current Rx - RE + current add