Contrast is the differential luminance between one object and another. Contrast sensitivity (CS) quantifies the ability to detect this difference: estimating contrast threshold provides information about the quality of vision and helps diagnose and monitor eye diseases. High contrast visual acuity assessment is traditionally performed in the eye care practice, whereas the estimate of the discrimination of low contrast targets, an important complementary task for the perception of details, is far less employed. An example is driving when the contrast between vehicles, obstacles, pedestrians, and the background is reduced by fog. Many conditions can selectively degrade CS, while visual acuity remains intact. In addition to spatial CS, “temporal” CS is defined as the ability to discriminate luminance differences in the temporal domain, i.e., to discriminate information that reaches the visual cortex as a function of time. Likewise, temporal sensitivity of the visual system can be investigated in terms of critical fusion frequency (CFF), an indicator of the integrity of the magnocellular system that is responsible for the perception of transient stimulations. As a matter of fact, temporal resolution can be abnormal in neuro-ophthalmological clinical conditions. This paper aims at considering CS and its application to the clinical practice.

Perception is the ability to see, hear, or become aware of external stimuli through the senses. Visual stimuli are electromagnetic waves that interact with the eye and elicit a sensation. Sensations, indeed, imply the detection, resolution, and recognition of objects and images, and their accuracy depends on the integrity of the visual system. In clinical practice, evaluating the integrity of the visual system relies greatly on the assessment of visual acuity, that is to say on the capacity to identify a signal. Visual acuity, indeed, is of utmost importance for diagnosing and monitoring ophthalmological diseases. Visual acuity is a function that detects the presence of a stimulation (a signal) and resolves its detail(s). This is the case of a symbol like “E”: the stimulus is detected, then it is resolved as three horizontal bars and a vertical bar. In fact, within the clinical setting visual acuity is usually measured with alphanumeric symbols and is a three-step process that involves not only detection and resolution, but, due to the semantic content of letters and numbers, their recognition. Along with subjective (psychophysical) procedures, objective methods that do not require the active participation of the observer have been proposed to estimate visual acuity in non-collaborating subjects, malingerers, or toddlers. This paper aims to explain the psychophysical rationale underlying the measurement of visual acuity and revise the most common procedures used for its assessment.

Abstract: The disease burden of diabetic retinopathy (DR) is tremendous around the world. While DR is correlated with hemoglobin A1c (HbA1c) and duration of diabetes, genetic differences likely account for variation in susceptibility to DR. DR is a polygenic disorder with demonstrated heritability. However, linkage and admixture analyses, candidate gene association studies, and genome-wide association studies (GWAS) have not identified many loci for DR that can be consistently replicated. Larger, collaborative, multi-ethnic GWAS are needed to identify common variants with small effects. Rigorous defining of controls groups as patients with a long duration of diabetes without DR, and case groups as patients with severe DR will also aid in finding genes associated with DR. Replication in independent cohorts will be key to establishing associated loci for DR. Investigations of mitochondrial DNA and epigenetics in DR are ongoing. Whole exome sequencing presents new opportunities to identify rare variants that might be implicated in DR development. Continued research in the genetic epidemiology of DR is needed, with the potential to elucidate pathogenesis and treatment of an important disease.

Abstract: Despite appropriate management of the systemic disease, patients with diabetes may develop severe forms of diabetic retinopathy that require surgery. Non-clearing vitreous haemorrhage (VH), traction retinal detachment involving the macula, combined traction and rhegmatogenous retinal detachment, progressive fibrovascular proliferation (PFP) and rubeosis with acute VH represent the main indications for surgery. Vitrectomy techniques and surgical tools have developed dramatically in the last decade in order to help the surgeon succeed in these challenging cases.

Abstract: There are many advantages to understanding the genetics of human disease. Genetic markers can be used to calculate the risk of developing a disease, and elucidation of genetic risk factors can pinpoint the molecular aetiology of disease, which can facilitate the development of targeted therapies. Diabetic retinopathy (DR) is a common complication of diabetes that has a significant impact on quality of life. It has a clear genetic component, but determination of the genetic risk factors has proven difficult. To date, genome-wide studies for DR have been conducted on relatively small patient cohorts compared to other complex eye diseases and replication of genetic findings has been limited. The disease is highly heterogeneous, confounding attempts to classify patients into appropriate groups for genetic analysis and making direct comparisons between studies challenging. Future studies to determine the genetic causes of DR will need to focus on larger sample sizes, detailed phenotyping and appropriate classification of patients. Global co-operation and meta-analyses combining data from multiple studies will be critical to the discovery of genetic risk loci for DR.

Abstract: Diabetic retinopathy (DR) is a leading cause of visual loss worldwide. Disease severity is graded from mild non-proliferative DR to proliferative DR. Optical coherence tomography angiography (OCTA) has become widely accepted as a useful noninvasive technique that provides detailed imaging of the ocular vessels. It is also becoming an increasingly essential tool for both qualitative and quantitative assessment of DR, especially with the advent of wider imaging capabilities. Various angiographic features of DR, such as microaneurysms, intraretinal microvascular abnormalities, neovascularization, and nonperfusion have been comprehensively studied and described using OCTA. Different quantitative OCTA metrics have been introduced, such as vessel density, foveal avascular zone (FAZ) area, and area of nonperfusion. Current research has been focusing on the application of quantitative OCTA for the diagnosis of DR and treatment monitoring. The primary purpose of this article is to review the use of OCTA, including its challenges, in the diagnosis and management of DR.

Abstract: Diabetic retinopathy (DR) is the most common microvascular complication in patients with diabetes mellitus (DM), and remains the single greatest cause of blindness in working age adults around the world. In this article, we review the evolution of pharmacotherapies for both diabetic macular edema (DME) and DR such as anti-vascular endothelial growth factor inhibitors and various steroid formulations, as well as other emerging pharmacotherapies currently in late stage clinical testing for this disease.

Keywords: Diabetic macular edema (DME); diabetic macular oedema (DMO); anti-vascular endothelial growth factor (anti-VEGF); laser photocoagulation; randomised clinical trials (RCTs); retina; diabetic retinopathy

Abstract: Contrast is the differential luminance between one object and another. Contrast sensitivity (CS) quantifies the ability to detect this difference: estimating contrast threshold provides information about the quality of vision and helps diagnose and monitor eye diseases. High contrast visual acuity assessment is traditionally performed in the eye care practice, whereas the estimate of the discrimination of low contrast targets, an important complementary task for the perception of details, is far less employed. An example is driving when the contrast between vehicles, obstacles, pedestrians, and the background is reduced by fog. Many conditions can selectively degrade CS, while visual acuity remains intact. In addition to spatial CS, “temporal” CS is defined as the ability to discriminate luminance differences in the temporal domain, i.e., to discriminate information that reaches the visual cortex as a function of time. Likewise, temporal sensitivity of the visual system can be investigated in terms of critical fusion frequency (CFF), an indicator of the integrity of the magnocellular system that is responsible for the perception of transient stimulations. As a matter of fact, temporal resolution can be abnormal in neuro-ophthalmological clinical conditions. This paper aims at considering CS and its application to the clinical practice.