This short article describes the case of an 82-year-old male patient who was referred to my clinic by a retinal surgeon. The patient had untreatable age-related macular degeneration and the surgeon asked whether he might have some help with his near vision. A major concern was that the patient had been forced to close down his small department store as he was no longer able to identify the denomination of any bank notes.
Initial assessment showed the patient to have the following vision:
Focusing on the left, one might predict that around 6x magnification might be required to attempt N6 (because 36/6 = 6). A range of optical aids of varying simplicity were tried and rejected. Surprisingly, the aid that was best accepted by the patient for the desired task was not the one that might have been predicted.
Low Vision Aids Tried
First off, the patient tried to use a hand magnifier (figure 1). A range of increasingly powered aids were tried but all were rejected by the patient.
A high add was first tried in a trial frame (figure 2) and then a pair of ready made +24.00DS spectacles offered (figure 3). This power should, in theory, offer the required 6x magnification (24/4 = 6), but the magnification and the short working distance (roughly 4cm) could not be coped with. Note how the ready-mades have base-in prism incorporated to assist with convergence for such a near target, though with our patient this was of no use as they were effectively monocular.
Figure 2: Trialling a high add in a trial frame
Figure 3: +24DS readymade spectacle magnifiers
Next, the patient tried a spectacle mounted telescopic system (figure 4). However, the restricted field of view and the magnification of head movement meant these too were rejected.
Figure 4: Spectacle mounted telescopic device
In an attempt to improve field of view, focus on simplicity and encourage light gathering at the expense of magnification, a dome magnifier was tried – and promptly rejected (figure 5).
Figure 5: Dome magnifier
Finally, and much to our surprise, the patient tried a simple hand-held Fresnel magnification sheet (figure 6). These tend to be low magnification only and, due to the nature of the prism, suffer somewhat from light transmission loss. However, as a reminder that it is always worth trying as wide a range of options as possible, the patient immediately took to the device and, even though it was nowhere near what would be required to read smaller text, found that he was able to use the sheet to identify bank notes. He also then went on to show how he could hold the sheet in such a way as to allow him to write simple notes to colleagues at work (figure 7).
Figure 6: Identifying a bank note with a Fresnel prism sheet
Figure 7: A note written to colleagues
This simple case serves as reminder that sometimes the least expected aid is the one a patient may choose, and in this case, the one most likely to help him restart his business.
- Dr Narendra Kumar, BAMS, DROpt, PGCR is Editor, Optometry Today and a clinician at Ophthacare Eye Centre, Janakpuri, New Delhi
