Ehsan Rahimy

Bio: Ehsan Rahimy is an academic researcher from Palo Alto Medical Foundation. The author has contributed to research in topics: Fluorescein angiography & Macular degeneration. The author has an hindex of 30, co-authored 103 publications receiving 2968 citations. Previous affiliations of Ehsan Rahimy include Thomas Jefferson University & Wills Eye Institute.

Paracentral acute middle maculopathy: a new variant of acute macular neuroretinopathy associated with retinal capillary ischemia.

Abstract: Importance With the advent of more sophisticated imaging systems, such as spectral domain optical coherence tomography (SD-OCT), disruption of the inner segment/outer segment (IS/OS) band, and thinning of the outer nuclear layer (ONL) have been identified in association with acute macular neuroretinopathy (AMN). Objectives To characterize a new SD-OCT presentation of AMN as a paracentral acute middle maculopathy and to describe multimodal imaging findings that implicate an underlying pathogenesis related to retinal capillary ischemia. Design, Setting, and Participants Retrospective observational case series (January 1, 2012, to January 1, 2013) reviewing clinical and imaging data from 9 patients (11 eyes) with AMN at 6 tertiary referral centers. Lesions were classified as type 1 or 2 in relation to the SD-OCT location of the lesion above (type 1) or below (type 2) the outer plexiform layer (OPL) at 6 tertiary referral centers. Results Of the 9 patients, 5 were female and 4 were male (mean age, 47.6 years; range, 21-65 years). All patients presented with an acute paracentral scotoma and demonstrated a classic dark gray paracentral lesion with near-infrared imaging. Visual acuity ranged from 20/15 to 20/30. Six eyes (5 patients) had type 1 SD-OCT lesions, also referred to as paracentral acute middle maculopathy, and 5 eyes (4 patients) had type 2 SD-OCT lesions. Although type 1 lesions lead to inner nuclear layer (INL) thinning, type 2 lesions resulted in ONL thinning. Type 2 lesions were always associated with significant outer macular defects, including disruption of the inner segment/outer segment and outer segment/retinal pigment epithelium bands, whereas type 1 lesions spared the outer macula. Conclusions and Relevance Paracentral acute middle maculopathy may represent a novel variant of AMN that affects the middle layers of the macula above the OPL as diagnosed with SD-OCT imaging. Two types of AMN lesions may be seen with SD-OCT occurring above and below the OPL. Type 1 refers to hyperreflective bands in the OPL/INL region with subsequent INL thinning. Type 2 is hyperreflective bands in the OPL/ONL region with subsequent ONL thinning. Type 2 lesions may be associated with concomitant defects of the inner segment/outer segment layer. We propose that each of these lesions may be explained by occlusion of either the superficial capillary plexus (type 1) or deep capillary plexus (type 2) located in the innermost and outermost portion of the INL, respectively, immediately adjacent to each corresponding lesion type.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Retinal Vascular Layers Imaged by Fluorescein Angiography and Optical Coherence Tomography Angiography

Abstract: Importance The retinal vasculature is involved in many ocular diseases that cause visual loss. Although fluorescein angiography is the criterion standard for evaluating the retina vasculature, it has risks of adverse effects and known defects in imaging all the layers of the retinal vasculature. Optical coherence tomography (OCT) angiography can image vessels based on flow characteristics and may provide improved information. Objective To investigate the ability of OCT angiography to image the vascular layers within the retina compared with conventional fluorescein angiography. Design, Setting, and Participants In this study, performed from March 14, 2014, through June 24, 2014, a total of 5 consecutive, overlapping B-scan OCT angiography images composed of 216 A-scans were obtained at 216 discrete positions within a region of interest, typically a 2 × 2-mm area of the retina. The flow imaging was based on split-spectrum amplitude decorrelation angiography (SSADA), which can dissect layers of vessels in the retina. These distinct layers were compared with the fluorescein angiograms in 12 healthy eyes from patients at a private practice retina clinic to evaluate the ability to visualize the radial peripapillary capillary network. The proportion of the inner vs outer retinal vascular layers was estimated by 3 masked readers and compared with conventional fluorescein angiograms of the same eyes. Main Outcomes and Measures Outcome measures were visualization of the radial peripapillary capillary network in the fluorescein and SSADA scans and the proportion of the inner retinal vascular plexus vs the outer retinal capillary plexus as seen in SSADA scans that would match the fluorescein angiogram. Results In none of the 12 eyes could the radial peripapillary capillary network be visualized completely around the nerve head by fluorescein angiography, whereas the network was readily visualized in the SSADA scans. The fluorescein angiograms were matched, with a mean proportion of the inner vascular plexus being 95.3% (95% CI, 92.2%-97.8%) vs 4.7% (95% CI, 2.6%-5.7%) for the outer capillary plexus from the SSADA scans. Conclusions and Relevance Fluorescein angiography does not image the radial peripapillary or the deep capillary networks well. However, OCT angiography can image all layers of the retinal vasculature without dye injection. Therefore, OCT angiography, and the findings generated, have the potential to affect clinical evaluation of the retina in healthy patients and patients with disease.

Artificial Intelligence in Healthcare

Abstract: Artificial intelligence (AI) is gradually changing medical practice. With recent progress in digitized data acquisition, machine learning and computing infrastructure, AI applications are expanding into areas that were previously thought to be only the province of human experts. In this Review Article, we outline recent breakthroughs in AI technologies and their biomedical applications, identify the challenges for further progress in medical AI systems, and summarize the economic, legal and social implications of AI in healthcare.

TFOS DEWS II pathophysiology report

Abstract: The TFOS DEWS II Pathophysiology Subcommittee reviewed the mechanisms involved in the initiation and perpetuation of dry eye disease. Its central mechanism is evaporative water loss leading to hyperosmolar tissue damage. Research in human disease and in animal models has shown that this, either directly or by inducing inflammation, causes a loss of both epithelial and goblet cells. The consequent decrease in surface wettability leads to early tear film breakup and amplifies hyperosmolarity via a Vicious Circle. Pain in dry eye is caused by tear hyperosmolarity, loss of lubrication, inflammatory mediators and neurosensory factors, while visual symptoms arise from tear and ocular surface irregularity. Increased friction targets damage to the lids and ocular surface, resulting in characteristic punctate epithelial keratitis, superior limbic keratoconjunctivitis, filamentary keratitis, lid parallel conjunctival folds, and lid wiper epitheliopathy. Hybrid dry eye disease, with features of both aqueous deficiency and increased evaporation, is common and efforts should be made to determine the relative contribution of each form to the total picture. To this end, practical methods are needed to measure tear evaporation in the clinic, and similarly, methods are needed to measure osmolarity at the tissue level across the ocular surface, to better determine the severity of dry eye. Areas for future research include the role of genetic mechanisms in non-Sjogren syndrome dry eye, the targeting of the terminal duct in meibomian gland disease and the influence of gaze dynamics and the closed eye state on tear stability and ocular surface inflammation.