There are two good reasons to check near vision:
Reason #1: Useful information regarding the patient’s refractive state can be gathered from the near vision measurement.
Reason #2: Useful information regarding glasses difficulties can be gathered from the near vision measurement. For many patients, the refraction/glasses evaluation is the most important part of the examination, particularly if the patient has no ongoing disease process (e.g. dense cataracts, glaucoma, AMD).
Most patients rightly expect a good pair of glasses that function well at distance and near. How do you know about how the patient functions at near unless you observe them trying to read?
How to measure near vision and see how the above reasons come into play:
1. If glasses are needed for near, you will want to check the near vision with correction. Checking near vision without correction generally does qualify as a waste of time, unless that is the normal mode for the patient.
2. Provide good lighting. The ceiling light is usually not good enough. It is best to position the position the reading light of the instrument stand so that light is coming over the patients shoulder.
3. Hand a reading card to the patient and point out on the card which line that you want him/her to read. Don’t use the occluder at this point. Start with the small numbers and work up, so initially point to the Jaeger 1 (20/25) line. Allow the patient to hold the card at whatever distance is comfortable and tell the patient to hold the card at whatever distance seems to work for them. The patient who can immediately read the numbers with little effort is probably already in good shape in this department. The patient who has to push progressive lenses up to see better, either needs a frame adjustment or needs more plus power for reading.
4. Now check each eye individually using the occluder. Hold the occluder, otherwise this task may take forever. Have the patient hold the card at his/her “normal” distance. Many times, an eye will see a little better at near than in the distance. For example, 20/40 distance, 20/30 or 20/25 at near, particularly if the near add is stronger than +2.50, due to proximal magnification. If there is a big discrepancy distance/near, this tells you that the glasses prescription is off and that you will likely find a refractive change when measured.
In summary, measuring near vision gives you useful clues as the refractive state and the patient’s visual performance at near. This information can save you time by pointing you in the right direction regarding the needs of the patient.