Title : Assessing preventable blindness: A comparison of preoperative visual acuity in Tanzania and the UK
Abstract:
Introduction: Cataract is the leading cause of reversible blindness worldwide, responsible for approximately 45% of global blindness and affecting over 65 million people. The burden is greatest in low and middle-income countries, where access to timely surgery is often limited. Pre-operative visual acuity (VA) offers an objective measure of cataract severity and enables comparison of disease stage at presentation. This study compares pre-operative VA in patients undergoing cataract surgery in Tanzania and the United Kingdom, aiming to quantify the severity of reversible blindness prior to intervention at presentation in two contrasting healthcare systems.
Methods: This retrospective study analysed anonymized data from two institutions. Pre-operative VA and patient age from Mt Meru Referral Hospital in Arusha, Tanzania, was collected for surgeries between September 2022 and April 2024 (n=72). Pre-operative VA for this group, originally measured in Snellen, was converted to logMAR using a conversion scale from a published study (Moussa et al., https://doi.org/10.1111/aos.14659). Pre-operative VA and patient age from Princess Alexandra Hospital in Harlow, UK, was collected for surgeries between October and November 2023 (n=74). All data were uploaded to Excel for organization, and an independent samples t-test was performed to compare the means of the two groups.
Results: The study included 74 eyes from Harlow and 72 from Tanzania. The mean preoperative visual acuity (VA) in logMAR was significantly better in the Harlow group (mean = 0.41, SD = 0.22) compared to the Tanzanian group (mean = 2.39, SD = 0.41). This difference was statistically significant (p<0.0001). The mean age of patients from Harlow, UK, was 78.79 years, while the mean age of patients in Arusha, Tanzania, was 69.87 years, a difference which was also statistically significant (p<0.0001).
Discussion/Conclusion: Pre-operative visual acuity was significantly poorer in the Tanzanian cohort, indicating a more advanced stage of cataract and later presentation compared to the UK group. This disparity highlights the potential impact of differing healthcare systems on the burden of reversible blindness. The UK's abundant primary healthcare system and clear referral pathways likely facilitate earlier detection and intervention. In contrast, the private healthcare system in Tanzania, where patients pay at the point of access, may serve as a significant barrier, leading to delayed presentation. While a significant age difference was observed between the two cohorts (p<0.0001), suggesting that patients in the UK are presenting for surgery later in life, the profound difference in VA suggests that other systemic factors are more influential. A limitation of this study is that there may be confounding variables that were not controlled across the groups. Medical co-morbidities like diabetes can influence rates of cataracts, and these were not measured during this study. Nonetheless, these findings suggest that targeted public health interventions to improve access to care and reduce barriers to surgery in low-resource settings may be crucial for reducing the burden of reversible blindness and improving visual outcomes for patients.
