The Arclight Ophthalmoscope: A Reliable Low-Cost Alternative to the Standard Direct Ophthalmoscope

Figure 2

Bland-Altman plots showing the difference between the examiner’s estimate of vertical cup : disc ratio (VCDR) and the reference standard, split by instrument. Plot (a) represents the Arclight direct ophthalmoscope and plot (b) represents the Heine K180 direct ophthalmoscope. Where there is exact agreement between the examiner and the reference standard the difference in VCDR is noted as 0. Any deviation from 0 represents underestimation (if negative) or overestimation (if positive) of the VCDR compared with the reference standard. The horizontal dotted line represents the mean of all observations (i.e., their mean deviation from the reference standard), and the grey area represents the proportion of all observations lying within 95% of the normal distribution for each of the two ophthalmoscopes. The size of each black dot is proportional to the number of observations it represents.

(a)

(b)