The relationship between pseudodrusen and choroidal thickness
PURPOSE: To determine the relationship between pseudodrusen as evidenced by the presence of subretinal drusenoid deposits and choroidal thickness using a multimodal imaging approach. METHODS: Two sets of data were analyzed. The first set was composed of consecutive patients older than 60 years with either high myopia or pseudodrusen. Correlations were calculated between the subfoveal choroidal thickness and the presence of pseudodrusen. The second set of data was obtained from a previously published data examining 90 consecutive eyes with nonexudative age-related macular degeneration so that the relationship between pseudodrusen and subfoveal choroidal thickness could be analyzed. RESULTS: There were 96 eyes of 53 patients in the first data set, 36 (67.9%) were female and 17 (32.1%) were male. There were 34 patients (61 eyes) in the High Myopia group and 19 patients (35 eyes) in the Primary Pseudodrusen group. The mean age of the Primary Pseudodrusen group was 83.7 years and that of the High Myopia group was 74.9 years, a difference that was significant (P < 0.001). Of the 61 eyes in the High Myopia group, only 3 (4.9%) had pseudodrusen and 0 had conventional drusen. In the Primary Pseudodrusen group, all had pseudodrusen by definition, but 28 (80%) also had conventional drusen. The mean subfoveal choroidal thickness was 181.7 mum (median, 147; interquartile range, 65-225 mum) in the Primary Pseudodrusen group and 59 mum (median, 36; interquartile range, 21-90 mum) in the myopic group. Generalized estimating equation analysis showed that eyes with pseudodrusen had thicker subfoveal choroidal thickness than eyes without, a result driven by the High Myopia group. In the second set of data, while the absolute number of eyes with pseudodrusen had a choroidal thickness between 201 mum and 250 mum, the proportion with pseudodrusen was higher in eyes with thinner choroids, with a broad peak between 50 mum and 100 mum. CONCLUSION: Our results are not consistent with a simple cause or consequence relationship between pseudodrusen and choroidal thinning, but rather with a third yet unknown factor impacting both the pseudodrusen appearance and the choroidal thinning in susceptible populations. The reasons for the relative lack of drusen and pseudodrusen formation in high myopes need to be ascertained.