Procedure
- Allow the patient to position themselves at the distance indicated on the chart (usually 5m).
- Depending on the indication for the examination, the patient is either allowed to keep their glasses on (monitoring if the correction is still satisfactory) or to take them off.
- Provide the patient with a cover patch or cover spoon.
- It is sensible to always start with the same eye to avoid confusion when making notes about the patient’s vision [Figures 8, 9].
Figure 8
Figure 9
- Using the pointer, indicate the first line from the side and ask the patient if they can see the depicted symbols sharply.
- Clearly define in what direction the E symbols are pointed, or on which side the opening of the C is positioned. If the patient can see everything clearly and sharply, proceed to the next line.
- Repeat this procedure until the patient hesitates when answering or indicates that they cannot see the symbols sharply anymore.
- Point at various symbols one by one on a particular line.
- Hold the pointer underneath the middle of the individual symbol.
- Particularly with the Landolt visual acuity chart, it is important not to cover the opening with the pointer.
- The patient should quickly name the symbol, indicate the position of the E, or say where the opening in the C is.
- This should be done correctly for two-thirds of the indicated symbols. If this happens without delay or hesitation, one can assume that the patient is still capable of reading this line. If this is not the case, repeat this procedure for the line above, even if the patient indicated seeing this line without problems.
- If the patient is capable of correctly naming two-thirds of the indicated symbols, continue once again with the next smaller line on the visual acuity chart.
- Stop when the patient is no longer capable of naming the required number of symbols [Figure 10].
Figure 10
- The vision of the patient equals the number corresponding to the line of which 2/3 of the symbols were named correctly.
If a patient cannot see the symbols of the first line properly, vision is determined by means of counting fingers. Someone with vision 1 is capable of counting fingers against a white background from a distance of 60m (= D) [Figure 11].
- Stand 5m from the patient and allow them to count the number of fingers that you hold up in front of a white background.
- If the patient does not succeed, stand 1m closer to them.
- Hold your fingers both horizontally and vertically.
- In this case, vision is equal to the distance (d) between the physician and the patient, at which the patient was capable of counting the number of fingers held up, divided by D.
- In this example, it is d/60.
Figure 11
If the patient is not capable of correctly counting your fingers at a distance of 1m, the distance at which the patient can observe hand movements is investigated. A person with vision 1 is capable of registering hand movements at a distance (D) of 300 m.
- Start at a distance of 5m from the patient and repeat the steps 1m closer up, until the distance (d) is reached, at which the patient observes your hand movements.
- The patient’s vision is again d/D, and in this case, it is d/300.
The patient’s vision is noted as follows:
- Vision oculus dexter (right eye) VOD = …
- Vision of the left eye is recorded in an identical manner, where D for dexter is substituted by S for sinister (i.e. VOS = …).
- If the examination was carried out without the patient wearing any corrective glasses or lenses, then sc is added (sine correctione).
The notation is therefore: VODsc = … / VOSsc = … - If the examination was conducted with correction, the sc is substituted by cc (cum correctione).
- In an ophthalmologic clinic, it is standard practice to add to the note on vision the number of correctly named symbols on the line following the last completed line on the chart. For example VODsc = 0.8 ++.