# Study of Diagnostic Accuracy: Fundus Photography vs. Optical Coherence Tomography
## 1 Introduction  
According to the World Health Organization, globally, at least 2.2 billion people have a vision impairment or blindness, of whom at least 1 billion have a vision impairment that could have been prevented or has yet to be addressed [1]. \"Eye conditions and vision impairment are widespread, and far too often they still go untreated\", stated Dr [PERSON], the WHO's Director General. Furthermore, the fact that 80% of cases of visual impairment are preventable shows that there is a great deal of room for improvement. The number of newly registered people with maculopathies in the Spanish National Organization of the Blind increased by 14% in 2022 and 5.9% for those with glaucoma [2, 3, 4, 5]. Optical coherence tomography (OCT) has revolutionized the way in which vitreo-retinal diseases are assessed and studied. The usefulness of OCT in clinical practice isbecoming increasingly relevant [6; 7; 8; 9]. Frequently, the general population undergoes eye examinations to procure eyeglasses. Eye exams with fundus photography that are conducted by optometrists are limited, because FP does not show all of the possible posterior pole alterations. In Spain, the optometrist cannot use mydriatic drops, meaning that using FP as part of an optometrist's practice encounters some problems, such as miosis. Furthermore, non-mydriatic FP is associated with some limitations, such as corneal opacity or the opacity of the ocular media [10]. So far, various articles have compared OCT to FP in relation to different characteristics, such as their ability to improve glaucoma screening [11], or in the screening of age-related macular degeneration [12]. The findings demonstrated substantial differences in the diagnostic accuracy between screenings using FP with OTC and FP alone. In a glaucoma screening, FP's sensitivity was 55.4% while the sensitivity of FP + OCT was 80%; however, their levels of specificity were similar (92%). In the screening of age-related macular degeneration, 97.7% of the images were gradable using OCT while only 52.4% were gradable using FP. This study would allow us to determine the clinical relevance of OCT in identifying posterior pole abnormalities [13; 14; 15; 16]. It focused on two main areas: determining the value that OCT adds to FP in optometric practice and assessing what proportion of alterations are visible in OCT and not in FP. We further sought to identify differences in the judgment accuracy between ophthalmologists (gold standard) and optometrists. To achieve the early detection of pathologies or retinal alterations such as diabetic retinopathy, glaucoma, or macular holes, is important that the optometrist, who is visited by patients more frequently, has the optimal criteria and instruments to carry out high-quality population screenings. Regarding the assessment of FP, in an article by [PERSON] et al. published in the Journal of Clinical Nursing [17], one shortcoming is that FP of various patients could not be assessed by the nursing professionals in charge in a study of the prevalence of diabetic retinopathy; therefore, patients were not referred to the ophthalmologist. The National Health System faces specific problems such as the lack of development of primary care. The following are two problematic situations in Spain: over referral, due to distrust of FP that sometimes collapses the emergency service; and sick cases not being diagnosed in time which generates a higher cost in the long term. We followed the Standards for Reporting of Diagnostic Accuracy (STARD) guidelines to conduct this comparative study. Designing a study to evaluate the performance of these tests presents several challenges, not least the need to have a reference standard, as the tests are subject to human interpretation [18; 19; 20]. For these reasons, we consider this article of interest, since the intention is to quantify the diagnostic precision involved in evaluations based on FP alone, as are currently performed in Spain, for those patients with posterior pole abnormalities whose alterations are not visible in FP.