Previous studies have described conflicting results regarding the correlation between retinal central subfield thickness (CSFT) and visual acuity in wet AMD. In a recent cohort study, researchers aimed to analyze the relationship between CSFT variation and change in BCVA in a group of patients (141 eyes) over 12 months receiving anti-VEGF treatment to identify factors of prognostic significance. In all, 1300 OCT scans were recorded in the study.
At the end of 12 months, there was a statistically significant reduction in CSFT in all eyes. The mean BCVA of the high CSFT variation group (50.6 letters) was significantly lower than that of the low and moderate CSFT variation groups (57.5 and 59.8 letters, respectively). The adjusted mean BCVA gains were +1.7, +7.2 and +7.8 letters in the high, moderate and low CSFT variation groups respectively.
Along with observing a reduction in retinal thickness, there was a corresponding gain in vision. However, the authors noted there was a highly significant difference in visual outcomes after stratifying by thickness variation across the entire period of follow-up.
“Despite differences in baseline characteristics with the high CSFT variation group having a thicker baseline CSFT, this association remained significant after adjustment for baseline differences in demographic and clinical characteristics, including gender, age, baseline CSFT, lesion type and index greatest linear diameter, baseline BCVA, proportion of active visits and number of VEGF inhibitor injections,” the authors noted in their study. “In our data set, the high CFST variation group had lower baseline BCVA.”
It's already been shown that a lower baseline BCVA is a predictor of poorer final BCVA, but this status is also associated with greater letter gains from therapy. The authors of the present study explained this was not noted in their research, which suggests that retinal thickness fluctuation was the driving factor for poor vision gains in the high CSFT variation group.
“The poor outcomes in the high CSFT variation group may be due to the negative effect on the integrity of retinal structures and viability of photoreceptors in eyes with retinal thickness fluctuations,” the authors noted. “We hypothesize that the presence of retinal fluid results in a decreased photoreceptor directional sensitivity due to alterations in cone alignment and structure, and recurrent photoreceptor stretching and shrinking, which in turn may cause loss of photoreceptor viability and cellular loss.”
Cheong KX, Teo AW, Cheung CM, et al. Association between retinal thickness variation and visual acuity change in neovascular age-related macular degeneration. Clinical Science. April 15, 2021. [Epub ahead of print].