Twenty-eight of the overall 30 study participants took part in the DCE-style exercise. Baseline demographics of participants are presented in Supplementary file 1. The quantitative results, in terms of choices made, are shown in Table 1. Participants were classified as a clear proponent of one option if they consistently selected that option each time it was presented. Participants were classified as “No clear preference” if their choices showed no consistent preference (e.g. if they rated Option 4 as preferable to Option 1, Option 1 as preferable to Option 3, but then Option 3 as preferable to Option 4).
There was no correlation between option preferences and demographic factors including age, visual acuity and intravitreal injection exposure.
Table 2 displays participants’ reasoning about specific attributes of the different treatment scenarios. As shown, there was significant heterogeneity in participants’ views, with opposing logics influencing their decision-making; this highlights the highly personal and idiosyncratic nature of treatment preferences and is a noteworthy result. For example, quotations (q) 1 and 2 in Table 2 demonstrate concerns around the short time by which treatment would extend participants’ visual function, particularly in light of already advanced age. In contrast, participants in q3-4 justify their choice on the basis that any benefit for visual function, however limited, would still be helpful. While participants generally expressed the view that more frequent injections were burdensome (q6-7), one participant was in favour of more frequent injections because it would allow for more regular monitoring (q5). Time spent in clinic was rarely discussed (q8), because this was consistently set at two hours in clinic across all treatment options (apart from Option 1, no treatment). Risk of wet AMD was a factor that encouraged several participants to opt for lower risk (but also less efficacious) options (q9-11), although other participants (q12-13) were less concerned given the existence of effective intravitreal injection treatments for wet AMD. Notably, this limited concern applied for participants naïve to intravitreal injections (as in q12-13), as well as for certain participants already being treated successfully for wet AMD, e.g. “His eyesight has improved with those injections… I say it's improved, it's steadied it. So the injections are working… That influences the decision.” (P16 – daughter speaking on behalf of father – O3)
Table 2
Participants’ reasoning on their treatment preferences, with example quotations
Attribute and levels
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Reasoning guiding participant’s preference
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Example quotation (q)
Parentheses following the quotation refer to the participant number, and their overall preferred option(s)
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Preserved vision for…
O1: 5 years (no treatment, baseline)
O2: 6 years (20% slowing)
O3: 6.5 years (30% slowing)
O4: 5.5 years (10% slowing)
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Relatively small magnitude of efficacy
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1. “[There’s] not much difference between 5 years, 5 and a half, or 6 and a half. So I would choose no treatment or less injections.” (P5 – O1 = O2)
2. “If my fellow eye was affected, I would be more interested. I am 85 years old, if I have 2 more years I will be satisfied. So 1.5 years is not long enough. If you said 10 years it would be different.” (P10 – O4)
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Any preservation of visual function is beneficial
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3. “No injection option is out of question… Even if six months [more vision] is not long, it is still better. I know there’s a risk of wet [AMD], but longer vision is better.” (P29 – O3)
4. “I know six months is precious. But it’s not very long. I’d still go for Option 3… Yes, I’d try to get the maximum benefit.” (P26 – O3)
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Frequency of hospital visit and injection:
O1: None (no treatment, baseline)
O2: 6 times per year (once every two months)
O3: 12 times per year (monthly)
O4: 4 times per year (every three months)
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Frequent injections are preferable
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5. “I would like to have more frequent injections, ideally four weekly [ie once a month, Option 3], because I feel safer under close monitoring.” (P8 – O3)
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Frequent injections are burdensome
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6. “Twelve injections that’s a lot. But it depends. Less injections is better. Twelve is a lot - I might even forget.” (P23 – O4)
7. “If I was to sell this to my mother… and the amount of effort she would have to make to come to hospital. And given her life expectancy. She would go for minimum injections. Because of my mum’s age and health.” (P25 – son speaking on behalf of mother – O1)
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Time spent at clinic:
O1: None
O2: Up to two hours
O3: Up to two hours
O4: Up to two hours
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Time at the eye clinic is burdensome
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8. “Two hours is a long time. Not many people will be happy.” (P23 – O4)
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Risk of developing neovascular AMD within a year of starting treatment
O1: 1 in 50 (no treatment, baseline)
O2: 1 in 20
O3: 1 in 10
O4: 1 in 50
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Risk of wet AMD as drawback to more frequent, effective treatment
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9. “It [concern about wet AMD] is my biggest thing. Because I’ve been told that’s worse than the dry one. They’re trying to stop the dry one developing into the wet one… the one in 50 chance of not getting it [in Option 4], that’s what sways me.” (P13 – O4)
10. [Discussing Option 3] “One in 10 chances of AMD, then I will have to have injection for wet. I think it’s not an option. I still don’t know.” (P28 – O2)
11. [Discussing Option 2] “The risk of wet AMD is off-putting as well. If you are going to get it anyway, like 1 in 20.” (P25 – O1)
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Risk of wet AMD not affecting decision-making
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12. “I’m not concerned about the risk of wet AMD in particular.” (P7 – O2 = O3)
13. [Discussing Option 3] “He has a one in 10 chance of developing wet AMD. That's interesting, isn’t it? That's quite high, one in 10. So I have to make the same assumption that that isn’t a disaster. Because it’s quite likely”. (P26 – O3)
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While Table 2 parses participants’ comments by attribute, more commonly participants discussed the different attributes holistically, in relation to each other rather than in isolation. For example, participants frequently contrasted increased preservation of visual function against the increased risk of wet AMD, e.g.:
“It’s too small an increment. I would take less risk. The maximum gain is 6 months and the risk doubles. The gain isn’t worth the disadvantage.” (P28 – O2 – explaining choice of O2 over O3)
A similar process was evident in discussing preservation of visual function versus the frequency of injections:
“Only half a year [more vision] if I go twelve times against six times. I’d rather go six times, cos half a year’s not gonna make much difference… in that respect. If it was two years difference, then I would think about it.” (P9 – O4 – explaining choice of O2 over O3)
“It depends on the position of the eye, the situation of the eye, I can’t say. Because one year is certainly very useful, but I’m already 87… Option 3 is pathetic, it’s only half a year more than Option 2.” (P30 – O2)
Despite the task involving a choice for the imaginary patient “Mr Smith”, most participants clearly related the decision-making process back to the particularities of their own situation; this is notable. For example, one participant stated:
“If injections could guarantee it will improve my vision, I would go for injections. I chose no injection options because I am old enough. If I carry on for another four years, I don’t care what happens after that. For younger people it’s different. They are the ones to get old and blind. If they are young, for them it’s better than me. I am old enough. If I lose my eye it’s too bad.” (P22 – O1)
This quote demonstrates that the participant understood the five years of preserved vision for Mr Smith in Option 1 as directly relevant to her situation, stating that she would be happy with even four years of preserved vision. However, she was able to put herself in the shoes of a younger person with GA who may see the treatments as more worthwhile.
Relatedly, several other participants who were overall ambivalent or negative about treatment struggled to make a choice. For example, P3 stated,
“None of the options with treatment is acceptable for me and I am just answering, not that I would go for it. I really don’t see any benefits.” (P3)