No recent survey data are available about the magnitude and causes of avoidable blindness in Zanzibar. This study aimed to address this by conducting a rapid assessment of avoidable blindness (RAAB) survey. The RAAB survey is a relatively quick and cheap method, as it only includes people aged 50 and over (the prevalence of avoidable blindness is highest in this group). This minimises the sample size required.
The RAAB survey was conducted on Pemba and Unguja islands during July 2007. Visual acuity (VA) was measured and lens status was assessed. All eyes with VA <6/18 were examined to diagnose the cause of visual impairment. All participants with VA <6/18 who had also previously had a cataract operation were interviewed.
A total of 3,160 persons aged >50 were examined (a response rate of 98.8%). The prevalence of blindness was 3.7% (defined as VA <3/60, with available correction, in the better eye). Avoidable causes accounted for 75% of blindness.
Cataract was the leading cause of blindness (67%), followed by posterior segment diseases (25%). Cataract (47%) and refractive error (39%) were the leading causes of visual impairment in both eyes.
A total of 30% of the eyes that had been operated on for cataract had a poor outcome (visual acuity <6/18). The most common reported barrier to receiving cataract operations was ‘unaware of treatment’ (36%).
Of the 95 patients affected by poor outcome, 15 did not attend for postoperative care. The greatest barrier to receiving post-operative care was ‘not advised’ (80%). Most of the patients who mentioned this as a factor were from the private sector. The other barriers were ‘distance to travel too far’ (6.7%), and ‘fear of returning after surgery’ (6.7%).
In conclusion, there is a need for:
routine monitoring of cataract operations to improve outcome
more optical services to address refractive errors
better public awareness about the available eye health services
better coordination between the government and private sector; this will allow patients operated on in the private sector to be followed up in the government sector
guidelines for the routine management of cataract patients, including counselling techniques to lessen the anxiety of patients before and after operations.