The blood-ocular barrier system is formed by 2 main barriers: the blood-aqueous barrier and the blood-retinal barrier (BRB). The BRB is particularly tight and restrictive and is a physiologic barrier that regulates ion, protein, and water flux into and out of the retina. The BRB consists of inner and outer components, the inner BRB being formed of tight junctions between retinal capillary endothelial cells and the outer BRB of tight junctions between retinal pigment epithelial cells. The BRB is essential to maintaining the eye as a privileged site and is essential for normal visual function. Methods of clinical evaluation of the BRB are reviewed and new directions using optical coherence tomography are presented. Alterations of the BRB play a crucial role in the development of retinal diseases. The 2 most frequent and relevant retinal diseases, diabetic retinopathy and age-related macular degeneration (AMD), are directly associated with alterations of the BRB. Diabetic retinopathy is initiated by an alteration of the inner BRB and neovascular AMD is a result of an alteration of the outer BRB. Macular edema is a direct result of alterations of the BRB.

Ocular fundus imaging plays a key role in monitoring the health status of the human eye. Currently, a large number of imaging modalities allow the assessment and/or quantification of ocular changes from a healthy status. This review focuses on the main digital fundus imaging modality, color fundus photography, with a brief overview of complementary techniques, such as fluorescein angiography. While focusing on two-dimensional color fundus photography, the authors address the evolution from nondigital to digital imaging and its impact on diagnosis. They also compare several studies performed along the transitional path of this technology. Retinal image processing and analysis, automated disease detection and identification of the stage of diabetic retinopathy (DR) are addressed as well. The authors emphasize the problems of image segmentation, focusing on the major landmark structures of the ocular fundus: the vascular network, optic disk and the fovea. Several proposed approaches for the automatic detection of signs of disease onset and progression, such as microaneurysms, are surveyed. A thorough comparison is conducted among different studies with regard to the number of eyes/subjects, imaging modality, fundus camera used, field of view and image resolution to identify the large variation in characteristics from one study to another. Similarly, the main features of the proposed classifications and algorithms for the automatic detection of DR are compared, thereby addressing computer-aided diagnosis and computer-aided detection for use in screening programs.

To characterize macular edema that occurs after uneventful cataract surgery. Centre of Ophthalmology, University Hospital, Institute of Biomedical Research on Light and Image, Faculty of Medicine, University of Coimbra, Coimbra, Portugal. Thirty-two eyes of 32 patients had uneventful phacoemulsification with implantation of a foldable intraocular lens. Postoperatively, patients were examined at 3, 6, 12, and 30 weeks. The examinations included retinal leakage analysis (Zeiss CSLO), optical coherence tomography (Humphrey Instruments), and retinal thickness analysis (Talia Technology, Ltd.). Results were compared with those in a control group comprising healthy subjects. Increases in retinal thickness (ie, over the mean +/- 2 SD in the control group) reached a maximum at 6 weeks in 13 of 32 eyes (41%), after which recovery was progressive. At 30 weeks, all eyes had good visual acuity, but 7 eyes (22%) still had macular edema. The edema was located primarily in the central macular region. Leaking sites involving the vascular areas of the macula, which indicated areas of abnormal blood-retinal barrier permeability, were a frequent finding. The number of sites remained relatively stable during the first 12 weeks (88%) and decreased to 68% at 30 weeks, indicating a trend toward recovery. Macular edema after cataract surgery occurred primarily in the central region of the macula and was associated with the presence of leaking sites, which were located predominantly in the vascular regions of the central macula.

The primary objective of this study was to assess whether the topical administration of two neuroprotective drugs (brimonidine and somatostatin) could prevent or arrest retinal neurodysfunction in patients with type 2 diabetes. For this purpose, adults aged between 45 and 75 years with a diabetes duration ≥5 years and an Early Treatment of Diabetic Retinopathy Study (ETDRS) level of ≤35 were randomly assigned to one of three arms: placebo, somatostatin, or brimonidine. The primary outcome was the change in implicit time (IT) assessed by multifocal electroretinography between baseline and at the end of follow-up (96 weeks). There were 449 eligible patients allocated to brimonidine (n = 152), somatostatin (n = 145), or placebo (n = 152). When the primary end point was evaluated in the whole population, we did not find any neuroprotective effect of brimonidine or somatostatin. However, in the subset of patients (34.7%) with preexisting retinal neurodysfunction, IT worsened in the placebo group (P < 0.001) but remained unchanged in the brimonidine and somatostatin groups. In conclusion, the topical administration of the selected neuroprotective agents appears useful in preventing the worsening of preexisting retinal neurodysfunction. This finding points to screening retinal neurodysfunction as a critical issue to identify a subset of patients in whom neuroprotective treatment might be of benefit.