The impact of the severity of vision loss on vision-specific functioning in a German outpatient population - an observational study.

BACKGROUND: To validate the German-translated VF-14, a vision-specific scale, and determine the relationship between the severity of vision impairment, ocular conditions, and visual functioning.
METHODS: This was a clinic-based, cross-sectional study with 184 patients with low vision and 90 normal-sighted controls recruited from a German eye hospital. Participants underwent a clinical examination and completed the German VF-14 scale. The validity of the VF-14 scale was assessed using Rasch analysis. The main outcome measure was the visual functioning overall score.
RESULTS: The participants' mean ± SD [standard deviation] age was 59.4 ± 21.8 years ,and there were more female (58.4%) than male participants. The main cause of vision loss was age-related macular degeneration [AMD] (n = 54, 19.7%). Rasch analysis substantiated the German VF-14 to be a valid scale to assess visual functioning in the sample. Visual functioning consistently declined with worsening vision. In adjusted-multivariate analysis models, compared to control participants, those with mild, or moderate/severe vision impairment recorded significantly poorer visual functioning scores (p < 0.05). The independent association was clinically significant for those with moderate/severe vision impairment. The main ocular conditions were also found to be independently associated with worse visual functioning, with clinical significance found for AMD, diabetic retinopathy, and other retinal diseases.
CONCLUSIONS: Using a psychometrically valid German-translated VF-14, even mild vision impairment was independently associated with poor visual functioning. These findings reinforce the importance of early preventative and rehabilitative efforts to prevent longitudinal deterioration in vision loss.