By Lesley Hooson DO, Specsavers Lower Hutt, NZ
Background
Px: 73-year-old retired female who lives with her partner and who has been coming to the store for 4 years. Patient is active and enjoys walking, music and reading.
Habitual Rx:
RE: +0.75/-1.50 x 115 ADD +2.75 VA 6/6 and N4
LE: +0.50/-1.50 x 45 ADD +2.75 VA 6/6 and N4
Patient is very small and regularly wears teen frames, with distance ocular centres of 31mm and 30mm. Got on well with D-segment flat-top bifocals.
Two years prior to presentation, the patient’s VA decreased to R 6/10 and L 6/24 with N5 in both eyes. She was referred to a specialist for age-related macular degeneration (AMD).
One year prior to presentation, the patient’s VA decreased to R 6/12 and L 6/60 N10, and she was diagnosed with wet AMD. At the time of presentation, she had been receiving anti-VEGF (vascular endothelial growth factor) injections on a 6-weekly basis and had also recently undergone AMD laser therapy.
New prescribed Rx:
RE: 0.00/-2.00 x120 ADD +4.00 VA 6/24 N10
LE: +0.75/1.50 x45 ADD +4.00 VA 6/48 N10
Concern: Patient was having increasing difficulty reading. While she was happy with her flat-top D-segment bifocal lenses, her partner was keen for her to try progressives.
Discussion
Explained to the patient that with the +4.00 ADD, she would find reading easier, but that she would have to hold her books at a closer distance than normal, with a new working distance of 25-33cm. Discussed the benefits of having good lighting from behind and the possibility of using electronic books where the text size can easily be increased.
Explained to the patient’s partner that as the patient was using her peripheral vision more, progressives would not be suitable. Also noted that with a high ADD, there would be less base down prism in her bifocals; as the optical centre is close to the top of the segment, the image jump would be negligible. The patient’s bifocals gave her a good reading field without intruding into the distance field.
Although the +4.00 ADD meant that the ledge at the top of the segment was quite defined, cosmetically, the lenses were good as the size of the segment did not make the lens any thicker than the distance lens. However, reflections off the top of the segment can occasionally intrude into the wearer’s peripheral vision, so an anti-reflection coating was recommended to prevent this.
Solution
Selected a small-sized frame, Shrimp 50:16, with D-seg bifocals and an UltraClear SuperClean coating. Although the patient was initially concerned by the look of the lenses, she was more concerned with their function. She wanted to achieve the best vision possible whilst still feeling comfortable and fashionable in her new glasses, which was achieved with the new dispense.
Learning Outcomes
Learning more about eye diseases, such as AMD (Appendix 1), and the related problems that can occur can improve a dispenser’s understanding of a patient’s needs. It is useful to keep in mind that for some patients, function is far more important than fashion and feel. This case also highlights the benefits of using an AR coating to prevent the visual impact of reflections from the segment ledge of bifocal lenses.
Appendix 1. Definition of AMD
AMD is a leading cause of severe vision loss and affects 1 in 7 people over the age of 50, increasing to 1 in 3 over the age of 80. At the onset there are often no symptoms and it may affect either one or both eyes. AMD causes progressive macular damage resulting in loss of central vision, although the peripheral vision is not affected. If left untreated, vision loss can be rapid and irreversible. A major risk factor is smoking, and other risk factors include raised blood pressure and high cholesterol.
AMD occurs in two major subgroups – identified as ‘wet’ and ‘dry’ AMD. Dry AMD progresses slowly, a gradual degeneration often with no acute symptoms. However, wet AMD has an acute onset of symptoms due to abnormal growth of fragile new blood vessels in the retina, stimulated by VEGF, leading to leakage of blood and protein causing irreversible damage to the photoreceptors.
