# Study of Diagnostic Accuracy: Fundus Photography vs. Optical Coherence Tomography
## 3 Results  
### Sample  
After a period of 14 months of analyses and evaluations of the eye fundus, conducted independently by the two research teams, a total of 1334 eyes from assessments of 667 Spanish patients were obtained in this study, 68.5% of which were for female patients. The mean age of the participants was 60 \(\pm\) 18 years (interquartile range of 40-90 years). The CDVA was 0.89 and the median was 1, meaning that 50% of the records had a CDVA of 1. Two people were excluded because they did not want to participate in the study for personal reasons.  
The sample was made up of 1334 eyes from 667 people. Although the sample is representative of the Spanish population, as seen in Figure 5, the participant group aged between 40 and 51 was smaller than this group is in the overall Spanish population; there were slightly more people aged between 58 and 84 years old.  
To simulate the daily practice of the optometrist who has the FP and the one who has the OCT, the following assessments were conducted. In the first stage, each research group reviewed and classified the posterior pole of each eye, based on the information given and on the conventional eye examination together with the FP images. During this stage, of the 1334 eyes, 974 could be evaluated. In the second stage, the research groups classified the status of the posterior pole based on the information used in the previous stage together with the reports provided by the 3D macula OCT and 3D optic nerve OCT. During this stage, of the 1334 eyes, 1278 could be evaluated (Figure 6). The results of first stage (FP), according to the ophthalmologist, were as follows: there were 354 non-valuable eyes and 980 valuable eyes, of which 817 were healthy eyes and 163 were altered eyes, and 133 were referable eyes and 30 were preferential referable eyes. According to the optometrist, there were 141 non-valuable eyes and 1193 valuable eyes, of which 694 were healthy and 499 were altered, and 484 were referable and 15 were preferential referable. According to the ophthalmologist, the results of the second stage (FP + OCT) were as follows: there were 33 non-valuable eyes and 1301 valuable eyes, of which 963 were healthy eyes and 338 were altered eyes, and 268 were referable eyes and 70 were preferential referable eyes. According to the optometrist, there were 24 non-valuable and 1310 valuable eyes, of which 719 were healthy eyes and 594 were altered eyes; these were divided into 548 referable eyes and 43 preferential referable eyes.  
Figure 5: The black line represents the population between 40 and 90 years old residing in Spain in July 2022 (data collected by the INE). The orange bar represents the distribution of the sample based on their age.  
The results obtained by the ophthalmologists are summarized in Table 1. They show that 24% of the sample could be evaluated by adding OCT to the FP examination. The OCT provided evaluable images in almost all of the examined eyes (97.5%), compared to the FP value of 73.5%. Figure 7 shows an example of a posterior pole alteration that was not visible when using FP.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline Assessment & & FP & FP + OCT \\ \hline \multirow{3}{*}{Evalable} & Healthy & 817 (61.2\%) & 963 (72.2\%) \\  & Referable & 133 (10.0\%) & 268 (20.1\%) \\ \cline{1-1}  & Preferential & 30 (2.3\%) & 70 (5.2\%) \\ \cline{1-1}  & Referable & & 354 (26.5\%) & 33 (2.5\%) \\ \hline \hline \end{tabular}
\end{table}
Table 1: Distribution of disease severity according to the ophthalmologist’s assessment.  
Figure 6: Flow diagram of the distribution of the disease severity of the samples.  
When analyzing the results using a gold standard assessment, 13% of the sample, which was not assessable when using FP, exhibited alterations, and an additional 2.9% of cases exhibited abnormalities requiring an urgent referral. The results shown in Table 1 display 40 eyes with severe retinal alterations that were not referred as quickly as they needed to be due to OCT not being used for their assessment.