Welcome to question of the day #249

Eyetools question of the day #249

Recently several of my patients have returned complaining that their reading prescription is too strong or not strong enough for some of their near work tasks? How can I fix this?

It can be difficult to satisfy all of a patient’s near requirements with one reading add.

Some practitioners use the Hofstetter formula to decide what add to prescribe for each of their presbyopic patients. There are actually three Hofstetter formulas:

  1. The average amplitude of accommodation, in dioptres 18.5 – (0.30 * patient age in years) with the
  2. Minimum amplitude of accommodation as 15 – (0.25 * age in years)
  3. The maximum amplitude of accommodation as 25 – (0.40 * age in years).

Some practitioners calculate the remaining amplitude of accommodation and then the amount of near add required for the person to carry out their near work activities. Those practitioners that I know who use this method use the minimum amplitude of accommodation formula.

Other practitioners will use a table to decide on the required near add.

Age                              Required add

35-40                                       0.25

41-45                                       1.00

46-50                                       1.50

51-55                                       2.00

56-60                                       2.25

61-65                                       2.50

66-70                                       2.75

My preferred technique is to ask presbyopic patients to show me what distances they need to see things at near. This usually means a desktop computer screen, a book, and a hand-held electronic device.

I measure each distance with a tape measure and note the distances in the clinical records.

It is very difficult for one reading add to cover these three tasks so I often advise a pair of single vision or office progressives for the computer screen and then one add, in single or multifocal form, to cover the book and electronic device working distances. This patient-specific approach takes into account differing arm lengths and differing working habits. I can modify my one add to make sure it gives the range for a book (far range) and also for an electronic device (near range). Working with the patient this way makes add selection a team effort.

In my experience using this team method approach results in patients who are happy with their ability to perform near vision tasks with the spectacles I have prescribed.