Suber S. Huang

Anti–Vascular Endothelial Growth Factor Pharmacotherapy for Age-Related Macular Degeneration: A Report by the American Academy of Ophthalmology

OBJECTIVE To examine the evidence about the safety and efficacy of anti-vascular endothelial growth factor (VEGF) pharmacotherapies for the treatment of neovascular age-related macular degeneration (AMD). DESIGN Literature searches were conducted in May and October 2007 in PubMed with no date restrictions, limited to articles published in English, and in the Cochrane Central Register of Controlled Trials without a language limitation and yielded 310 citations. The first author reviewed the abstracts of these articles and selected 73 articles of possible clinical relevance for review by the panel. The panel deemed 64 of these articles sufficiently clinically relevant to review in full text and assigned ratings of level of evidence to each of the selected articles with the guidance of the panel methodologists. RESULTS Eleven studies provided level I evidence for intravitreal pegaptanib and ranibizumab for neovascular AMD; there were no studies rated level I for bevacizumab for neovascular AMD. Five studies were rated as level II, which included studies of ranibizumab and bevacizumab, and the remaining 38 articles retrieved were rated as level III. The studies do not provide information about long-term results or the value (comparative effectiveness) and cost-effectiveness of combined therapies. CONCLUSIONS Review of the available literature to date suggests that anti-VEGF pharmacotherapy, delivered by intravitreal injection, is a safe and effective treatment for neovascular AMD for up to 2 years. There is level I evidence to support this conclusion for pegaptanib and ranibizumab, but none for bevacizumab at this time.

Optical Coherence Tomography Measurements and Analysis Methods in Optical Coherence Tomography Studies of Diabetic Macular Edema

OBJECTIVE To evaluate optical coherence tomography (OCT) measurements and methods of analysis of OCT data in studies of diabetic macular edema (DME). DESIGN Associations of pairs of OCT variables and results of 3 analysis methods using data from 2 studies of DME. PARTICIPANTS Two hundred sixty-three subjects from a study of modified Early Treatment of Diabetic Retinopathy Study (mETDRS) versus modified macular grid (MMG) photocoagulation for DME and 96 subjects from a study of diurnal variation of DME. METHODS Correlations were calculated for pairs of OCT variables at baseline and for changes in the variables over time. Distribution of OCT measurement changes, predictive factors for OCT measurement changes, and treatment group outcomes were compared when 3 measures of change in macular thickness were analyzed: absolute change in retinal thickness, relative change in retinal thickness, and relative change in retinal thickening. MAIN OUTCOME MEASURES Concordance of results using different OCT variables and analysis methods. RESULTS Center point thickness correlated highly with central subfield mean thickness (CSMT) at baseline (0.98-0.99). The distributions of changes in CSMT were approximately normally distributed for absolute change in retinal thickness and relative change in retinal thickness, but not for relative change in retinal thickening. Macular thinning in the mETDRS group was significantly greater than in the MMG group when absolute change in retinal thickness was used, but not when relative change in thickness and relative change in thickening were used. Relative change in macular thickening provides unstable data in eyes with mild degrees of baseline thickening, unlike the situation with absolute or relative change in retinal thickness. CONCLUSIONS Central subfield mean thickness is the preferred OCT measurement for the central macula because of its higher reproducibility and correlation with other measurements of the central macula. Total macular volume may be preferred when the central macula is less important. Absolute change in retinal thickness is the preferred analysis method in studies involving eyes with mild macular thickening. Relative change in thickening may be preferable when retinal thickening is more severe.

Spatial Distribution of the Pathways of Cholesterol Homeostasis in Human Retina

Background The retina is a light-sensitive tissue lining the inner surface of the eye and one of the few human organs whose cholesterol maintenance is still poorly understood. Challenges in studies of the retina include its complex multicellular and multilayered structure; unique cell types and functions; and specific physico-chemical environment. Methodology/Principal Findings We isolated specimens of the neural retina (NR) and underlying retinal pigment epithelium (RPE)/choroid from six deceased human donors and evaluated them for expression of genes and proteins representing the major pathways of cholesterol input, output and regulation. Eighty-four genes were studied by PCR array, 16 genes were assessed by quantitative real time PCR, and 13 proteins were characterized by immunohistochemistry. Cholesterol distribution among different retinal layers was analyzed as well by histochemical staining with filipin. Our major findings pertain to two adjacent retinal layers: the photoreceptor outer segments of NR and the RPE. We demonstrate that in the photoreceptor outer segments, cholesterol biosynthesis, catabolism and regulation via LXR and SREBP are weak or absent and cholesterol content is the lowest of all retinal layers. Cholesterol maintenance in the RPE is different, yet the gene expression also does not appear to be regulated by the SREBPs and varies significantly among different individuals. Conclusions/Significance This comprehensive investigation provides important insights into the relationship and spatial distribution of different pathways of cholesterol input, output and regulation in the NR-RPE region. The data obtained are important for deciphering the putative link between cholesterol and age-related macular degeneration, a major cause of irreversible vision loss in the elderly.

Cholestenoic Acid Is an Important Elimination Product of Cholesterol in the Retina: Comparison of Retinal Cholesterol Metabolism with That in the Brain

PURPOSE Accumulating evidence indicates a link between cholesterol and age-related macular degeneration. Yet, little is known about cholesterol elimination from the retina and retinal pigment epithelium (RPE), the two layers that are damaged in this blinding disease. Several different pathways of enzymatic cholesterol removal exist in extraocular tissues. The authors tested whether metabolites from these pathways could also be quantified in the bovine and human retina and RPE. For comparison, they measured cholesterol oxidation products in two regions of the bovine and human brain and in the bovine liver and adrenal glands. METHODS Sterol quantification was carried out by isotope dilution gas chromatography-mass spectrometry. Bovine tissues were used first to optimize analytical procedures and to investigate postmortem changes in oxysterol concentrations. Then human specimens were analyzed for oxysterol concentrations. RESULTS Qualitatively, oxysterol profiles were similar in the bovine and human tissues. In the human retina and RPE, the authors could not detect 27-hydroxycholesterol but unexpectedly found that its oxidation product, 5-cholestenoic acid, is the most abundant oxysterol, varying up to threefold in different persons. 24S-Hydroxysterol and pregnenolone were also present in the retina, but at much lower quantities and without significant interindividual variability. In the brain, the predominant oxysterol was 24S-hydroxycholesterol. CONCLUSIONS The oxysterol profile of the retina suggests that all known pathways of cholesterol elimination in extraocular organs are operative in the retina and that they likely vary depending on specific cell type. However, overall oxidation to 5-cholestenoic acid appears to be the predominant mechanism for cholesterol elimination from this organ.

The Eye at Altitude

High altitude retinopathy (HAR) was first described in 1969 as engorgement of retinal veins with occasional papilloedema and vitreous hemorrhage. Since then various studies have attempted to define the incidence, etiology and significance of this phenomenon, usually with small numbers of subjects. Recently studies on relatively large groups of subjects in Nepal, Bolivia and Tibet have confirmed that the retinal vasculature becomes engorged and tortuous in all lowlanders ascending above 2500m. Sometimes this leads to hemorrhages, cotton wool spots and papilloedema, which is the pathological state better known as high altitude retinopathy. These studies have also shown a significant change in both corneal thickness and intraocular pressure at altitude. The retinal blood vessels are the only directly observable vascular system in the human body and also supply some of the most oxygen-demanding tissue, the photoreceptors of the retina. New techniques are being applied in both hypobaric chamber and field expeditions to observe changes in retinal function during conditions of hypobaric hypoxia. This work allows better advice to be given to lowlanders traveling to altitude either if they have pre-existing ocular conditions or if they suffer from visual problems whilst at altitude. This especially applies to the effect of altitude on refractive eye surgery and results of recent studies will be discussed so that physicians can advise their patients using the latest evidence. Retinal hypoxia at sea level accounts for the developed worlds largest cause of blindness, diabetic retinopathy. The investigation of retinal response to hypobaric hypoxia in healthy subjects may open new avenues for treatment of this debilitating disease.

Safety profile of ocriplasmin for symptomatic vitreomacular adhesion: A comprehensive analysis of premarketing and postmarketing experiences

Purpose: After the recent approval of ocriplasmin by the Food and Drug Administration, postmarketing safety concerns have been raised by the vitreoretinal community. The American Society of Retina Specialists Therapeutic Surveillance Committee was commissioned to monitor postmarketing drug-related and device-related adverse events. The purpose of this report is to analyze the postmarketing safety experience in the context of available premarketing safety data. Methods: Periodic aggregate safety reports consisting of premarketing, or clinical trial, data (n = 999 injections) and postmarketing reports through July 16, 2013 (n = 4,387 injections), were retrospectively analyzed by the TSC. The aggregate data were analyzed to classify adverse events, and the postmarketing safety data for each event type were compared with the premarketing data. Results: Eight categories of adverse events were identified. Acute reduction in visual acuity attributable to either worsening of macular pathology or development of subretinal fluid, electroretinogram changes, dyschromatopsia, retinal tears and detachments, lens subluxation or phacodonesis, impaired pupillary reflex, and retinal vessel findings were reported in both the premarketing and postmarketing experiences. Ellipsoid zone (inner segment/outer segment) findings were only reported in the postmarketing experience. Rates of postmarketing reports were lower than in the premarketing data. Adverse events were generally transient, and characteristics of these adverse events were generally similar between the premarketing and postmarketing experience. Conclusion: Postmarket analyses are limited by significant underreporting, and in the case of ocriplasmin as a first in-class drug, they may not have captured safety events that have only more recently been identified. Nonetheless, postmarket analyses can identify the scope of potential safety events based on real-world experiences. Ocriplasmin administration should be guided by an appropriate and informed risk-benefit discussion with the patient. Ongoing active postmarket surveillance by all practitioners will continue to be critical to better understand this safety profile.

Quantification of cholesterol-metabolizing p450s CYP27A1 and CYP46A1 in neural tissues reveals a lack of enzyme-product correlations in human retina but not human brain

Cytochrome P450 enzymes (CYP or P450) 46A1 and 27A1 play important roles in cholesterol elimination from the brain and retina, respectively, yet they have not been quantified in human organs because of their low abundance and association with membrane. On the basis of our previous development of a multiple reaction monitoring (MRM) workflow for measurements of low-abundance membrane proteins, we quantified CYP46A1 and CYP27A1 in human brain and retina samples from four donors. These enzymes were quantified in the total membrane pellet, a fraction of the whole tissue homogenate, using ¹⁵N-labled recombinant P450s as internal standards. The average P450 concentrations/mg of total tissue protein were 345 fmol of CYP46A1 and 110 fmol of CYP27A1 in the temporal lobe, and 60 fmol of CYP46A1 and 490 fmol of CYP27A1 in the retina. The corresponding P450 metabolites were then measured in the same tissue samples and compared to the P450 enzyme concentrations. Investigation of the enzyme-product relationships and analysis of the P450 measurements based on different signature peptides revealed a possibility of retina-specific post-translational modification of CYP27A1. The data obtained provide important insights into the mechanisms of cholesterol elimination from different neural tissues.

Abnormal vascularization in mouse retina with dysregulated retinal cholesterol homeostasis

Several lines of evidence suggest a link between age-related macular degeneration and retinal cholesterol maintenance. Cytochrome P450 27A1 (CYP27A1) is a ubiquitously expressed mitochondrial sterol 27-hydroxylase that plays an important role in the metabolism of cholesterol and cholesterol-related compounds. We conducted a comprehensive ophthalmic evaluation of mice lacking CYP27A1. We found that the loss of CYP27A1 led to dysregulation of retinal cholesterol homeostasis, including unexpected upregulation of retinal cholesterol biosynthesis. Cyp27a1-/- mice developed retinal lesions characterized by cholesterol deposition beneath the retinal pigment epithelium. Further, Cyp27a1-null mice showed pathological neovascularization, which likely arose from both the retina and the choroid, that led to the formation of retinal-choroidal anastomosis. Blood flow alterations and blood vessel leakage were noted in the areas of pathology. The Cyp27a1-/- retina was hypoxic and had activated Müller cells. We suggest a mechanism whereby abolished sterol 27-hydroxylase activity leads to vascular changes and identify Cyp27a1-/- mice as a model for one of the variants of type 3 retinal neovascularization occurring in some patients with age-related macular degeneration.

Repeated Intravitreous Ranibizumab Injections for Diabetic Macular Edema and the Risk of Sustained Elevation of Intraocular Pressure or the Need for Ocular Hypotensive Treatment

IMPORTANCE For the management of retinal disease, the use of intravitreous injections of anti-vascular endothelial growth factor has increased. Recent reports have suggested that this therapy may cause sustained elevation of intraocular pressure (IOP) and may potentially increase the risk of glaucoma for patients with retinal disease. OBJECTIVE To assess the risk of sustained IOP elevation or the need for IOP-lowering treatments for eyes with diabetic macular edema following repeated intravitreous injections of ranibizumab. DESIGN, SETTING, AND PARTICIPANTS An exploratory analysis was conducted within a Diabetic Retinopathy Clinical Research Network randomized clinical trial. Study enrollment dates were from March 20, 2007, to December 17, 2008. Of 582 eyes (of 486 participants) with center-involved diabetic macular edema and no preexisting open-angle glaucoma, 260 were randomly assigned to receive a sham injection plus focal/grid laser treatment, and 322 were randomly assigned to receive ranibizumab plus deferred or prompt focal/grid laser treatment. MAIN OUTCOMES AND MEASURES The cumulative probability of sustained IOP elevation, defined as IOP of at least 22 mm Hg and an increase of at least 6 mm Hg from baseline at 2 consecutive visits, or the initiation or augmentation of ocular hypotensive therapy, through 3 years of follow-up. RESULTS The mean (SD) baseline IOP in both treatment groups was 16 (3) mm Hg (range, 5-24 mm Hg). The cumulative probability of sustained IOP elevation or of initiation or augmentation of ocular hypotensive therapy by 3 years, after repeated ranibizumab injections, was 9.5% for the participants who received ranibizumab plus prompt or deferred focal/grid laser treatment vs 3.4% for the participants who received a sham injection plus focal/grid laser treatment (difference, 6.1% [99% CI, -0.2% to 12.3%]; hazard ratio, 2.9 [99% CI, 1.0-7.9]; P = .01). The distribution of IOP and the change in IOP from baseline at each visit through 3 years were similar in each group. CONCLUSIONS AND RELEVANCE In eyes with center-involved diabetic macular edema and no prior open-angle glaucoma, repeated intravitreous injections of ranibizumab may increase the risk of sustained IOP elevation or the need for ocular hypotensive treatment. Clinicians should be aware of this risk and should consider this information when following up with patients who have received intravitreous injections of anti-vascular endothelial growth factor for the treatment of diabetic macular edema.

Aflibercept-Related Sterile Inflammation

All injections were performed with standard techniques based on survey responses. Povidone-iodine 5% was applied before injection in all cases. Thirteen of 15 eyes were administered topical anesthesia, and 2 eyes were given subconjunctival lidocaine. All eyes were injected with the Becton Dickinson (Franklin Lakes, NJ) 1-ml Luer-Lok syringe included in the aflibercept packaging. The majority of eyes were injected in the superotemporal quadrant (12 of 15 eyes) and with a 32-G needle (13 of 15 eyes), while the remainder were injected in the inferotemporal quadrant (3 of 15 eyes) and with a 30-G needle (2 of 15 eyes). These differences likely represent individual practice pattern differences and are not an implication of these techniques. Five physicians practicing in the Northeast, the Southeast, and the Southern United States reported cases of sterile inflammation. Three physicians practiced in the same retina group, and 9 of 15 cases (60%) were reported by a single retina specialist in this practice, consistent with a clustering pattern previously reported with other intravitreal therapies. 2 All cases were attributed to 5 separate drug lots, with 3 lots accounting for 13 of 15 cases. All but 1 patient experienced symptoms within 3 days. Visual acuity generally recovered to baseline levels with nearly identical mean visual acuities at baseline (0.4 logarithm of the minimum angle of resolution) and after resolution (0.32 logarithm of the minimum angle of resolution) and a mean time to resolution of 30 days. No patient lost 1 Snellen line of visual acuity. In contrast with previous reports associating sterile inflammation from other intravitreal therapies with painless loss of vision, 3 9 of these 15 aflibercept-related cases (60%) presented with pain. Redness was noted only in eyes presenting with pain and in 6 of these 9 painful cases. It is possible that aflibercept-related sterile inflammation may be associated with higher rates of pain than previously reported. Alternatively, this difference may reflect differences in the treatment cohorts. Distinguishing between infectious and sterile endophthalmitis was at the discretion of the treating physician. Although all reported cases were culture negative, some of the cases treated with intravitreal antibiotics may have represented culture-negative infectious endophthalmitis, which is associated with increased pain, and not true sterile inflammation. However, 5 of 9 cases associated with pain were treated with vitreous tap and intravitreal antibiotic injection, and the remaining 4 cases were treated with topical steroids only, suggesting that potential misclassification of these symptoms is not fully responsible for this difference. It is likely that patients presenting with more pain were biased toward an initial diagnosis of infectious endophthalmitis (treated with tap/antibiotic injection) compared with those patients managed with topical steroids alone. Small sample size, clinical variation, and the limitations of voluntary reporting preclude definitive conclusions. Subgroup analysis did not detect any variables significantly affecting visual outcome or number of days to resolution (Tables 4 and 5; available at http://www.aaojournal.org). This letter serves as a descriptive case series to better understand the clinical characteristics of a cluster of aflibercept-related sterile inflammation. The manufacturer reports that approximately 30 000 injections had been administered during the reporting period, corresponding with a sterile inflammation rate of approximately 0.05%. Although there may certainly be additional, nonreported cases resulting in a higher actual rate, this frequency lies within the range documented by pivotal, prospective trials with aflibercept and other intravitreal agents and by retrospective analyses (Tables 6 and 7; available at http://www.aaojournal.org). The manufacturer continued to closely observe without public recalls or testing, and use of aflibercept has continued without persistent reports of unexpected rates of complications. The American Society of Retina Specialists Therapeutic Surveillance Subcommittee strongly urges practitioners to actively participate in postmarket surveillance of drug- and device-associated adverse events.