Raymond Iezzi

Dendrimer-based targeted intravitreal therapy for sustained attenuation of neuroinflammation in retinal degeneration.

Retinal neuroinflammation, mediated by activated microglia, plays a key role in the pathogenesis of photoreceptor and retinal pigment epithelial cell loss in age-related macular degeneration and retinitis pigmentosa. Targeted drug therapy for attenuation of neuroinflammation in the retina was explored using hydroxyl-terminated polyamidoamine (PAMAM) dendrimer-drug conjugate nanodevices. We show that, upon intravitreal administration, PAMAM dendrimers selectively localize within activated outer retinal microglia in two rat models of retinal degeneration, but not in the retina of healthy controls. This pathology-dependent biodistribution was exploited for drug delivery, by covalently conjugating fluocinolone acetonide to the dendrimer. The conjugate released the drug in a sustained manner over 90 days. In vivo efficacy was assessed using the Royal College of Surgeons (RCS) rat retinal degeneration model over a four-week period when peak retinal degeneration occurs. One intravitreal injection of 1 μg of FA conjugated to 7 μg of the dendrimer was able to arrest retinal degeneration, preserve photoreceptor outer nuclear cell counts, and attenuate activated microglia, for an entire month. These studies suggest that PAMAM dendrimers (with no targeting ligands) have an intrinsic ability to selectively localize in activated microglia, and can deliver drugs inside these cells for a sustained period for the treatment of retinal neuroinflammation.

Sustained Delivery Fluocinolone Acetonide Vitreous Implants: Long-Term Benefit in Patients with Chronic Diabetic Macular Edema

PURPOSEnTo present the safety and efficacy of intravitreal implants releasing 0.2 μg/day fluocinolone acetonide (FAc) in patients with chronic versus nonchronic diabetic macular edema (DME). To assess ocular characteristics, anatomic changes, and re-treatment and ancillary therapies that may explain the differential treatment effect seen with intravitreal implants releasing FAc 0.2 μg/day in patients with chronic and nonchronic DME. An overall benefit-to-risk assessment for the FAc 0.2-μg/day and FAc 0.5-μg/day doses has been reported previously.nnnDESIGNnPreplanned subgroup analysis of chronic (duration of diagnosis, ≥3 years) and nonchronic (duration of diagnosis, <3 years) DME in patients from 2 randomized, sham injection-controlled, double-masked, multicenter clinical trials.nnnPARTICIPANTSnPatients with persistent DME despite 1 or more macular laser treatment were randomized 1:2:2 to sham injection (n = 185), FAc 0.2 μg/day (n = 375), or FAc 0.5 μg/day (n = 393).nnnMETHODSnPatients received study drug or sham injection and after 6 weeks were eligible for rescue laser. Based on re-treatment criteria, additional masked study drug could be given after 1 year.nnnMAIN OUTCOME MEASURESnPercentage of patients with improvement of 15 letters or more from baseline. Secondary outcomes included other parameters of visual function and foveal thickness.nnnRESULTSnAt month 36, the difference between FAc 0.2 μg/day and sham control in the percentage of patients who gained 15 letters or more was significantly greater in chronic DME patients (FAc 0.2 μg/day, 34.0% vs. sham, 13.4%; P<0.001), compared with patients with nonchronic DME (FAc 0.2 μg/day, 22.3% vs. sham, 27.8%; P = 0.275). The greater response in patients with chronic DME was not associated with baseline ocular characteristics, changes in anatomic features, or differences in re-treatment or ancillary therapies. The ocular adverse event profile for FAc 0.2 μg/day was similar regardless of DME duration.nnnCONCLUSIONSnThis is the first published analysis correlating duration of diagnosis of DME with treatment effect. In patients with chronic DME, FAc 0.2 μg/day provides substantial visual benefit for up to 3 years and would provide an option for patients who do not respond to other therapy.

Autosomal Recessive Vitelliform Macular Dystrophy In a Large Cohort Of Vitelliform Macular Dystrophy Patients

Purpose: To report 11 cases of autosomal recessive vitelliform macular dystrophy and to compare their molecular findings and phenotypic characteristics with those of patients with the more common and well-described dominant form of the disease. Methods: Blood samples were obtained from 435 unrelated individuals with a clinical diagnosis of vitelliform macular dystrophy and screened for mutations in the coding sequences of BEST1. Medical records and retinal photographs of selected patients were reviewed. Results: Nine of the 435 probands were found to have 2 plausible disease-causing variations in BEST1, while 198 individuals were found to have heterozygous variations compatible with autosomal dominant inheritance. Inheritance phase was determined in three of the recessive families. Six novel disease-causing mutations were identified among these recessive patients: Arg47Cys, IVS7−2A>G, IVS7+4G>A, Ile205del12ATCCTGCTCCAGAG, Pro274Arg, and Ile366delCAGGTGTGGC. Forty-four novel disease-causing mutations were identified among the patients with presumed autosomal dominant disease. The phenotype of patients with recessive alleles for BEST1 ranged from typical vitelliform lesions to extensive extramacular deposits. Conclusion: The authors provide evidence that two abnormal BEST1 alleles, neither of which causes macular disease alone, can act in concert to cause early-onset vitelliform macular dystrophy.

No Face-Down Positioning and Broad Internal Limiting Membrane Peeling in the Surgical Repair of Idiopathic Macular Holes

OBJECTIVEnTo demonstrate the efficacy of broad internal limiting membrane (ILM) peeling and 20% sulfur hexafluoride (SF6) endotamponade with no face-down positioning in the surgical repair of idiopathic macular holes (MHs).nnnDESIGNnRetrospective study.nnnPARTICIPANTSnSixty-eight idiopathic MH cases in 68 eyes of 65 patients.nnnMETHODSnAll idiopathic MH surgeries by 1 surgeon between March 2009 and December 2012, performed using broad ILM peeling, 20% SF6, and no face-down positioning, were reviewed. No cases were excluded. Surgeon method included 23-gauge or 25-gauge pars plana vitrectomy with induction of posterior vitreous detachment (if necessary). Indocyanine green dye (0.08 mg/ml in D5W) was injected slowly, allowed to stain for 60 seconds, and then removed. The ILM was broadly peeled to the vascular arcades (approximately 8000 μm in diameter), followed by 2 fluid-air exchanges, separated by 5 minutes, and an air-20% SF6 exchange. Patients maintained reading position for 3 to 5 days and were followed up at least for 1 month. Exact binomial distributions were used to establish 95% confidence intervals, and the 1-way analysis of variance was used to compare preoperative and postoperative intraocular pressures (IOPs).nnnMAIN OUTCOME MEASURESnSingle-procedure MH closure rate, mean postoperative best-corrected visual acuity (BCVA), incidence of cataract, and IOP.nnnRESULTSnThree patients (4.6%) had bilateral MH and 9 patients (13.8%) had recurrent MH (mean duration from previous surgery, 8.3 ± 5.5 years; range, 1-16 years). Twenty-one MH (30.9%) were stage 2, 27 (39.7%) were stage 3, and 20 (29.4%) were stage 4. Five MH had a basal diameter of more than 1000 μm. Mean MH basal diameter was 609.6 ± 226.2 μm. Mean preoperative BCVA was 0.68 ± 0.29 logarithm of the minimum angle of resolution (logMAR) units (Snellen equivalent, 20/95), and mean most recent postoperative BCVA was 0.28 ± 0.18 logMAR units (Snellen equivalent, 20/38). The single-procedure MH closure rate was 100% (95% confidence interval, 95%-100%), and no complications were observed.nnnCONCLUSIONSnMacular hole surgery with broad ILM peeling, 20% SF6 gas, and no face-down positioning is highly effective in the surgical treatment of idiopathic MH with efficacy comparable with methods that use longer-acting gas endotamponade, face-down positioning, or both. In our series, this method eliminated the morbidity associated with postoperative face-down positioning.nnnFINANCIAL DISCLOSURE(S)nThe author(s) have no proprietary or commercial interest in any materials discussed in this article.

Intravitreous delivery of the corticosteroid fluocinolone acetonide attenuates retinal degeneration in S334ter-4 rats.

PURPOSEnTo study the neuroprotective properties of low-dose, sustained-release intravitreous fluocinolone acetonide (FA) in transgenic S334ter-4 rats.nnnMETHODSnS334ter-4 rats aged 4 weeks were divided into four groups: 0.5 microg/d FA-loaded intravitreous drug delivery implant (IDDI); 0.2 microg/d FA-loaded IDDI; inactive IDDI; and unoperated controls. Electroretinography (ERG) was performed before surgery and every 2 weeks after surgery for 8 weeks. When the rats were 12 weeks of age, outer nuclear layer (ONL) and inner nuclear layer (INL) thicknesses were measured. Microglial cell counts were obtained from retinal wholemounts labeled for Iba-1.nnnRESULTSnAt the end of the study, unoperated and inactive IDDI-implanted rats demonstrated 50% to 60% reductions in ERG amplitudes compared with those recorded at 4 weeks (P < 0.001 for both groups). FA 0.2-microg/d animals demonstrated 15% amplitude attenuation, while FA 0.5-microg/d animals showed 30% reduction. ONL thickness in FA 0.2-microg/d-treated eyes was 25.8% +/- 2.3% higher than in control group eyes (P < 0.001) and 30.0% +/- 2.1% higher than in inactive IDDI-implanted eyes (P < 0.001). In FA 0.5-microg/d-treated eyes, ONL thickness was 22.4% +/- 2.8% higher than in control group eyes (P < 0.001) and 22.3% +/- 3.7% higher than in inactive IDDI-implanted eyes (P < 0.01). No statistically significant difference was observed between the two control groups. No statistically significant difference between the two FA-treated groups was found. FA-treated groups demonstrated significantly fewer activated microglial cells than control groups.nnnCONCLUSIONSnChronic intravitreous infusion of FA preserves ONL cell morphology and ERG a- and b-wave amplitudes and reduces retinal neuroinflammation in S334ter rats. Based on these findings, the synthetic corticosteroid FA may promise a therapeutic role in patients with retinal degeneration.

Glutamate stimulation of retinal ganglion cells in normal and s334ter-4 rat retinas: a candidate for a neurotransmitter-based retinal prosthesis.

PURPOSE. To investigate the suitability of glutamate as a potential agent for a neurotransmitter-based retinal prosthesis. METHODS. Retinal ganglion cells (RGCs) from P35-70 albino Sprague-Dawley (normal) and P60-254 S334ter-4 (photoreceptor degeneration) rats were recorded extracellularly in flattened eye cup preparations, to assess their responses to glutamate, applied locally via micropipettes. RESULTS. Brief local application of glutamate effectively excited RGCs in both normal and degenerated retinas. Epiretinal surface application of glutamate was less likely to excite RGCs than was subsurface application (20 microm below the epiretinal surface). Glutamate evoked RGC firing rates, and the response patterns were similar for epiretinal surface and subsurface applications. Subsurface application of 2 mM glutamate effectively excited cells within 130 microm of the ejection sites. Response latencies averaged 281 ms and were significantly longer for OFF RGCs than for ON RGCs in normal retinas (P = 0.025). Suppression of activity was observed at shorter latencies ( approximately 100 ms) after glutamate application in most of the spontaneously active RGCs. Responses to each glutamate application were similar, and the duration of activity was directly dependent on the duration of application. RGC responses varied from recurrent high-frequency bursts to sustained firing at rates above 40 spikes/s, in normal and degenerated retinas. Paired, sequential applications of glutamate evoked two distinguishable responses, with interstimulus intervals as low as 200 ms. Overall, RGC response sensitivity to glutamate was similar in normal and degenerated retinas. CONCLUSIONS. Glutamate is an excellent candidate for a neurotransmitter-based retinal prosthesis, as its local application effectively stimulates RGCs with high spatial and temporal resolution.

NONINVASIVE GRADING OF RADIATION RETINOPATHY: The Use of Optical Coherence Tomography Angiography.

Purpose: Previous studies have shown that spectral domain optical coherence tomography can diagnose radiation retinopathy (RR) before ophthalmoscopic findings. Recently, optical coherence tomography angiography (OCT-A) has been helpful in seeing vascular findings undetected by spectral domain optical coherence tomography. The authors wish to demonstrate the OCT-A grading at varying levels of RR. Methods: The OCT-A, spectral domain optical coherence tomography, and ophthalmoscopic findings on 7 patients from December 2014 to March 2015 with varying levels of RR are demonstrated. Results: Findings on OCT-A could be demonstrated before spectral domain optical coherence tomography findings. Patients can be graded on a scale of increasing severity from 0 to 5, based on positive or negative clinical findings of RR between OCT-A. Optical coherence tomography increased central macular thickness, optical coherence tomography evident cysts, and ophthalmoscopy (Grade 0: −,−,−,−; Grade 1: +,−,−,−; Grade 2: +,+,−,−; Grade 3: +,+,+,−; Grade 4: ++,+,+,+; Grade 5: unreadable,++,++,+). Conclusion: The use of OCT-A allows for earlier detection of RR; thus, existing grading systems should be modified to include OCT-A.

Real-Time Imaging of Electrical Signals with an Infrared FDA-Approved Dye

Clinical methods used to assess the electrical activity of excitable cells are often limited by their poor spatial resolution or their invasiveness. One promising solution to this problem is to optically measure membrane potential using a voltage-sensitive dye, but thus far, none of these dyes have been available for human use. Here we report that indocyanine green (ICG), an infrared fluorescent dye with FDA approval as an intravenously administered contrast agent, is voltage-sensitive. The fluorescence of ICG can follow action potentials in artificial neurons and cultured rat neurons and cardiomyocytes. ICG also visualized electrical activity induced in living explants of rat brain. In humans, ICG labels excitable cells and is routinely visualized transdermally with high spatial resolution. As an infrared voltage-sensitive dye with a low toxicity profile that can be readily imaged in deep tissues, ICG may have significant utility for clinical and basic research applications previously intractable for potentiometric dyes.

Intraocular pressure instability after 23-gauge vitrectomy.

Purpose: The purpose of this study was to describe outcomes, trends, risk factors, and protective factors for intraocular pressure (IOP) spikes in patients undergoing 23-gauge pars plana vitrectomy. Methods: A retrospective review in an academic institution was performed on all eyes undergoing 23-gauge vitrectomy with at least 1-month follow-up. The main outcome measures included IOP and operative complications. Results: Ninety-seven eyes of 93 patients were included. Intraocular pressure spikes >22 in the first month occurred in 73% of eyes with or suspect for glaucoma versus 46% of eyes without (P = 0.017); 76% of eyes with a gas fill versus 44% of eyes with a fluid fill (P = 0.0036); and 21% of eyes started on IOP-lowering drops on postoperative day 1 versus 49% of eyes who were not (P = 0.0033). Complications included retinal tears (3%), intraoperative retinal detachment (2%), and postoperative retinal detachment (2%). Fifteen percent of eyes required suturing of at least one sclerotomy. There were no cases of postoperative hypotony or endophthalmitis. Conclusion: Patients with or suspect for glaucoma or those with a gas fill may be at risk for high postoperative IOP during the first month. Aggressive early treatment of IOP may prevent IOP spikes in the early postoperative period.

Worldwide Argus II implantation: recommendations to optimize patient outcomes.

BackgroundA position paper based on the collective experiences of Argus II Retinal Prosthesis System investigators to review strategies to optimize outcomes in patients with retinitis pigmentosa undergoing retinal prosthesis implantation.MethodsRetinal surgeons, device programmers, and rehabilitation specialists from Europe, Canada, Middle East, and the United States were convened to the first international Argus II Investigator Meeting held in Ann Arbor, MI in March 2015. The recommendations from the collective experiences were collected. Factors associated with successful outcomes were determined.ResultsFactors leading to successful outcomes begin with appropriate patient selection, expectation counseling, and preoperative retinal assessment. Challenges to surgical implantation include presence of staphyloma and inadequate Tenon’s capsule or conjunctiva. Modified surgical technique may reduce risks of complications such as hypotony and conjunctival erosion. Rehabilitation efforts and correlation with validated outcome measures following implantation are critical.ConclusionsBringing together Argus II investigators allowed the identification of strategies to optimize patient outcomes. Establishing an on-line collaborative network will foster coordinated research efforts to advance outcome assessment and rehabilitation strategies.