EyeWorld Weekly Update, September 15, 2017

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September 15, 2017
Volume 23 , Number 32

First human stem cell model for macular degeneration created

Researchers at the University of Rochester Medical Center, Rochester, New York, have developed a new human stem cell model that exhibits similar molecular and phenotypic properties of macular dystrophies. This model, Chad Galloway, PhD, Sonal Dalvi, PhD, and co-authors wrote in the study published in the Proceedings of the National Academy of Sciences, provides new opportunities for macular degeneration research and has already yielded possible drug targets. "Age-related macular degeneration (AMD) and related macular dystrophies (MDs) are a major cause of vision loss. However, pharmacological treatments in these diseases are limited due to the lack of knowledge of underlying disease mechanisms, partly because appropriate human models to study AMD and related MDs are lacking. Furthermore, in the living human eye, the entire retina acts as a functional unit, making it difficult to investigate the specific contribution of a particular retinal cell type in the disease," according to Galloway et al. Prior to this research, Ruchira Singh, PhD, one of the study authors, said in a blog post by the medical center, "it was not known if you can take cells from the human eye and make a cell model that displays the hallmarks of the disease."

Genetic test for conditions that lead to vision loss announced

Phosphorus (New York), a computational genomics company, announced an advanced genetic test that will identify inherited conditions that can lead to vision loss and blindness. "For inherited retinal disorders, genetic testing can be used to prevent vision loss and blindness,"Oscar Puig, chief scientific officer, Phosphorus, said in a press release. The ophthalmology genetic test includes 146 genes for inherited retinal disorders (Leber congenital amaurosis, retinitis pigmentosa, macular dystrophy, and more), 38 genes for cataracts, 18 genes for glaucoma, and eight genes for corneal dystrophy.

Study: Intracameral mydriatics vs. topical for pupil dilation in cataract surgery

Researchers in Malaysia compared intracameral mydriatics to topical mydriatics in pupil dilation for phacoemulsification cataract surgery in a new study published in the Journal of Cataract and Refractive Surgery. Routine cataract patients (n: 112) were randomized to receive either intracameral lidocaine 1% and phenylephrine 1.5% or topical phenylephrine 2.5% and tropicamide 1%. While there was no difference in mean pupil dilation between the two groups, the intracameral group was slower to dilate and continued to dilate throughout the surgery while the topical group constricted. Pupil size before the capsulorhexis was, on average, larger in the topical group compared to the intracameral group. Three patients who received intracameral mydriatics required additional measures for pupil dilation, compared to six in the topical group. There was one complication in each of the two groups. "Intracameral mydriatic agents dilated heavily pigmented pupils for phacoemulsification cataract surgery. However, in the early stages of surgery, pupil dilation was slower than with topical agents," Amelia Lim Lay Suan, MD, and co-authors wrote.

RESEARCH BRIEFS

  • Possible lipid biomarkers for age-related macular degeneration were identified in a human plasma metabolics study published in the journal Ophthalmology. The research by Inês Laíns, MD, and co-investigators, used mass spectrometry to analyze the plasma metabolic profile of patients with age-related macular degeneration and compared the results to a control group without vitreoretinal disease. Eighty-seven metabolites differed significantly between the AMD and control group, and most of them (82.2%) were part of lipid pathways. Most significant was the glycerophospholipid pathway. Analysis of variance showed 55% of these metabolites were different at different stages of AMD. "With metabolomics, we can identify blood profiles associated with AMD and its severity through laboratory testing," co-senior author Joan Miller, MD, said in a press release. "Because the signs and symptoms of early stage AMD are very subtle, with visual symptoms only becoming apparent at more advanced stages of the disease, identification of biomarkers in human blood plasma may allow us to better understand the early to intermediate stages of AMD so we may intervene sooner, and ultimately provide better care."
  • Researchers at the John A. Moran Center, Salt Lake City, tested the uveal and capsular biocompatibility of refractive index shaping of commercially available IOLs using a femtosecond laser system developed by Perfect Lens (Irvine, California). As Liliana Werner, MD, and co-authors of the study published in the Journal of Cataract and Refractive Surgery, explained it, "Intraocular lens power changes are obtained through a laser-induced chemical reaction in a targeted area of the IOL optic substance, with a localized increase in hydrophilicity and decrease in the refractive index. Simultaneous with these changes, the laser builds a refractive index shaping lens within the targeted area." The IOL used in this study was the CT Lucia 601PY (Carl Zeiss Meditec, Jena, Germany), a single-piece hydrophobic acrylic yellow IOL. The investigators saw consistent and precise power changes using the femtosecond laser system and found the treatment of the IOL to be biocompatible in rabbit eyes.
  • The U.K. Diabetic Retinopathy Electronic Medical Record Users Group, Report 2, based on a multicenter national diabetic retinopathy database study that included 4,850 eyes, describes the impact of cataract surgery on diabetic macular edema (DME). The findings published in the British Journal of Ophthalmology reveal that the rate of DME requiring treatment increases after cataract surgery among all grades of preoperative retinopathy. DME rate peaked at 3 to 6 months after cataract surgery (6.8%). The overall rate of DME that required medical intervention in these patients was 5.3% in the year after cataract surgery, compared to 2.9% in the year before cataract surgery.
  • A retrospective study published in the British Journal of Ophthalmology sought to provide more understanding about the pathogenesis of post-LASIK ectasia, analyzing tear cytokine profiles and using in-vivo confocal microscopy in eyes with ectasia after LASIK. These factors were analyzed in seven post-LASIK controls without ectasia and six with ectasia. The research identified a significant difference in the tear film cytokine profile between the two groups and an increase in corneal dendritic cells in the group with ectasia. This, Natasha Kishore Pahuja, MD, and co-authors wrote, "suggests an ongoing inflammatory response" in post-LASIK ectasia.

  • Product news
  • Lampalizumab (Roche, Basel, Switzerland), a drug for geographic atrophy related to AMD, failed to meet its primary endpoint in the first of two Phase III clinical trials. Namely, lampalizumab did not reduce the geographic atrophy lesion area compared to control in the Spectri study. "Geographic atrophy is a progressive and irreversible disease that impairs vision, and there are currently no available treatments," Sandra Horning, MD, chief medical officer and global head of product development, Roche, said in a press release. "While this result is disappointing, we will continue to evaluate results from Spectri to get a clearer understanding of the data as we await the results of our second Phase III study, Chroma, anticipated in November." The safety profile of lampalizumab in the Spectri study was similar to other lampalizumab trials and other intravitreal therapies.

This issue of EyeWorld Weekly Update was edited by Amy Goldenberg and Vanessa Caceres.

EyeWorld Weekly Update (ISSN 1089-0319), a digital publication of the American Society of Cataract and Refractive Surgery and the American Society of Ophthalmic Administrators, is published every Friday, distributed by email, and posted live on Friday.

Medical Editors: Eric Donnenfeld, MD, chief medical editor; Rosa Braga-Mele, MD, cataract editor; Clara Chan, MD, cornea editor; Reay Brown, MD, glaucoma editor; and Vance Thompson, MD, refractive editor.

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