Discussion
This analysis of NvAMD treatment outcomes, within the publicly funded NHS, identified trajectories of visual acuity that are broadly in line with other large, real-world data sets. Visual acuity outcomes were associated with both baseline characteristics and key clinical care processes. Even with adjustment for other variables, there was evidence of variation in outcomes between sites.
For both visual acuity outcomes and state at month 12, the strongest association was with baseline visual acuity. With each 0.1 LogMAR (five ETDRS letter) worsening of baseline acuity, visual acuity at 12 months increased by 0.074 LogMAR, equivalent to 3.5 ETDRS letters. Likewise, for the same worsening of baseline acuity, the odds of having a ‘poor’ visual acuity state at month 12 was 1.66 times higher, reinforcing the need for prompt referral, diagnosis and initiation of treatment. This trend for bigger gains but worse outcomes for eyes with lower baseline acuity has been well documented.5 6 Relative to eyes with baseline acuity of 50–59 ETDRS letters, Talks et al reported ORs of 0.24 and 10.52 for achieving a ‘good’ acuity state for eyes with baseline acuities of <45 or ≥75 letters.12 Tufail et al found a linear relationship between baseline acuity and achieving a ‘good’ acuity state, with every extra letter of acuity at baseline increasing the OR of a ‘good’ acuity outcome by 10%.14 These findings are likely to explain the better visual acuity state typically reported for second eyes. The lower and statistically significant OR of achieving a ‘poor’ acuity state for first eyes reported here was unexpected after including baseline visual acuity in the model. However, the effect size for first versus second-treated eyes is small and the finding may be due to chance. Alternatively, there may be a small effect of first or second-treated eye status on visual acuity outcomes above and beyond the effect of baseline visual acuity.
Other baseline characteristics associated with visual acuity outcomes and state were age, independent living and socioeconomic deprivation. For every extra 10 years of age, visual acuity at 12 months reduced by LogMAR 0.044, approximately two ETDRS letters, and the odds of having a ‘poor’ acuity state increased by almost 50%. Compared with the eyes of people living in the most deprived areas, eyes of people in the least deprived areas had greater acuity gains and were more likely to avoid a ‘poor’ visual acuity outcome, even after adjustment for baseline acuity and age. A non-significant trend existed, suggesting similar outcomes for eyes in the third and fourth quintiles. These findings have not been reported before but are consistent with the broader literature on socioeconomic deprivation and health outcomes. More et al reported a greater risk of presenting with lower acuity levels in people living in areas of high deprivation, after adjustment for age, gender and distance to the treatment centre.15 However, Acharya et al found that deprivation was not associated with baseline visual acuity.16
Key care processes were also found to be associated with acuity outcomes and state. In this data set, more than 75% of eyes complete the loading phase of three initial injections within 10 weeks. For those eyes with an incomplete loading phase, visual acuity was worse by almost 0.08 LogMAR, or four ETDRS letters, when compared with eyes with fast completion of the loading phase and a non-significant trend also suggested worse outcomes in eyes with medium or slow completion. Similarly, the likelihood of a ‘poor’ acuity outcome increased in eyes without fast completion of the loading phase, but statistical significance was reached only for the eyes with slow completion. For these eyes, the odds ratio of a ‘poor’ acuity outcome was 1.26 times that of eyes with fast completion. Mean visual acuity change was greater in eyes with loading phase completion under 90 days in the Rainbow study, regardless of whether subsequent treatment was given regularly.3 17 Similarly, acuity outcomes at both 3 and 12 months were greater in the eyes receiving three or more loading phase injections within 3 months (defined as 104 days) of starting treatment.18 In contrast, both visual acuity outcomes and state were better in eyes with regular treatment both during and after the loading phase in the Perseus study.4 Both studies reported better outcomes with more injections.4 17 Talks et al reported that each additional injection increased the likelihood of a ‘good’ acuity state and Ciulla et al also reported a linear improvement in visual outcomes with more injections, before a plateau was reached at 10 injections.5 12 In this study, each additional injection resulted in an 0.13 LogMAR acuity improvement, less than one ETDRS letter, but similar to the effect reported by Chandra et al.19
Despite case-mix adjustment for baseline characteristics and care processes, these data provide evidence of ongoing variation in acuity outcomes between sites. Compared with those treated at the reference site A, eyes with the same characteristics and care but treated at sites B and I had better acuity gains of 0.075 and 0.057 LogMAR, respectively, equivalent to 3.5 and 2.5 ETDRS letters. Conversely, acuity outcomes for eyes treated at sites K and L were worse by 0.085 and 0.063 LogMAR or four and three ETDRS letters. The likelihood of a ‘poor’ acuity state was reduced at sites B, C and E when compared with ‘identical’ eyes treated at site A. The ORs were 0.44 and 0.74 at sites B and E. The data analysed in this study cannot explain this variation. It may result from either baseline characteristics or care processes not studied here, such as tolerance of persistent intraretinal or subretinal fluid.20 In an earlier study involving 12 sites, Talks et al found significant variation in baseline and month 12 acuities. After adjustment, the odds of achieving a ‘good’ acuity state at the ‘best’ site was 1.53 (95% CI 1.15 to 2.05).12
The use of pooled data from multiple sites with wide geographical coverage adds validity to the findings of this study and improves the generalisability of study findings to the wider NHS NvAMD population. Real-world evidence can help shape and improve clinical practice.21 Many of the key findings are supported by other publications, but the associations with independent living status and socioeconomic status are novel. Loss to follow-up before the month 12 visit is a potential weakness. However, almost 85% of patients did reach this milestone and this figure compares favourably to other real-world data sets.11 12 17 As the data extracted for this study was collected as part of routine clinical practice in the publicly funded NHS, the findings may not be applicable to other healthcare systems. Different, licensed therapies were used, but there is little data to suggest meaningful differences in visual outcomes.22 23 In addition, other factors that may be associated with visual acuity outcomes, such as smoking history, time to diagnosis and adherence to treatment, were not included in the analysis given concerns about the quality of data entry. Data entry for smoking history in this study suggested a prevalence much lower than the estimated prevalence of 14.9% among UK adults in 2017 and 2018.24 Lesion type and the preferred treatment regimen were also not recorded, although the stated regimen at all sites was ‘treat and extend’, according to the clinical leads for medical retina. Similarly, the times from the onset of symptoms to initial presentation, referral from primary care, diagnosis and the start of treatment are not recordable within the current version of the Medisoft EMR and the contribution of these variables to acuity outcomes is not known. Finally, the use of median values for acuity at baseline and month 12 may have underestimated the population level visual acuity change when compared with the use of mean letter score change.
Although baseline visual acuity was the strongest predictor of both visual acuity outcome and state, several other baseline characteristics and care processes were also associated with visual acuity outcomes. Benchmarking of acuity outcomes should adjust for baseline acuity, age and socioeconomic deprivation. These characteristics appear more important than the care processes. Despite case-mix adjustment, there was evidence of variation in visual acuity outcomes between sites. Additional investigation is required to identify other baseline characteristics or care processes that explain this variation. Sharing of best practice may help to address the causes of this health inequality.