Progression From–

Progression From No AMD to Intermediate AMD as Influenced by Antioxidant Treatment and Genetic Risk: An Analysis of Data From the Age-Related Eye Disease
Study Cataract Trial

 ASRS-American Society of Retina Specialists

Journal of VitreoRetinal Diseases
2017, Vol. 1(1) 45-51
ª The Author(s) 2017
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DOI: 10.1177/2474126416680931
jvrd.sagepub.com

Carl C. Awh, MD1, Brent Zanke, MD, PhD2,3, and Rafal Kustra, PhD4

1 Tennessee Retina, PC, Nashville, TN, USA
2 Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
3 Arctic Diagnostics Inc, Toronto, Ontario, Canada
4 Division of Biostatistics, Dalla Lana School of Public Health, University of
Toronto, Toronto, Ontario, Canada
Corresponding Author:
Carl C. Awh, MD, Tennessee Retina, PC, 345 23rd Ave N Suite 350, Nashville,
TN 37203, USA.
Email: carlawh@gmail.com

Abstract
Purpose: To investigate the impact of antioxidant treatment and genetic risk on the development of intermediate age-related
macular degeneration (AMD) in patients without baseline AMD, using data from the Age-Related Eye Disease Study (AREDS)
Cataract Trial. Methods: Genetic risk and antioxidant treatment were analyzed as independent and interacting risk factors for
the development of intermediate AMD in 554 AREDS individuals for whom genotyping was available. Genetic risk was determined
using an allele dosage model based on the total number of complement factor H and age-related maculopathy sensitivity 2 risk
alleles. Results: Overall, 14% of patients developed intermediate AMD over approximately 8 years. The risk of developing
intermediate AMD varied from 6.5% for patients with 0 risk alleles to 39% for those with 3 or 4 risk alleles (P < .0001). Antioxidants
had no impact on the development of intermediate AMD overall. However, antioxidant treatment had a significant
impact on progression to intermediate AMD for patients with low or high genetic risk. Patients with 0 or 1 risk alleles had
increased risk of progression to intermediate AMD (hazard ratio [HR] ¼ 2.31, P ¼ .017) if treated with antioxidants compared to
placebo. Patients with 3 or 4 risk alleles had decreased risk of progression to intermediate AMD (HR ¼ 0.27, P ¼ .0008) if treated
with antioxidants compared to placebo. Conclusion: On average, antioxidant treatment has no impact on the development of
intermediate AMD in patients without AMD. However, antioxidant treatment may increase the risk of developing intermediate
AMD in patients with low genetic risk and may reduce the risk of developing intermediate AMD in patients with high genetic risk.
Since patients with high genetic risk have the greatest risk of progressing from intermediate to advanced AMD, genotype-directed
antioxidant treatment of patients without AMD may ultimately lead to fewer cases of advanced AMD.
Keywords
age-related macular degeneration, antioxidants, AREDS, genetics, complement factor H, ARMS2, vitamins, environment, carotenoids,
blindness, interaction
Introduction
Age-related macular degeneration (AMD) is the leading cause of severe vision loss in industrialized countries. Age-related macular degeneration progresses through well-characterized
stages. Early AMD is characterized by the presence of small drusen; intermediate AMD by large drusen, pigment changes, and occasional mild vision loss; and advanced AMD by choroidal
neovascularization or central geographic atrophy, typically with significant vision loss. Supplementation with zinc and antioxidants reduces the risk of progression from intermediate
to advanced AMD in some patients. No identified means exist to decrease the development of early or intermediate AMD, although evidence suggests that lifestyle modifications
such as smoking cessation and a healthy diet may reduce this risk.1 Despite the lack of evidence of benefits of nutritional supplements for patients with minimal or no AMD, ocular
nutritional supplements are widely marketed and used. In the United States, dietary supplements are not evaluated or regulated for efficacy or safety.2 Supplements promoting
‘‘eye health’’ are readily available, and of the 59% of adults in the United States who take dietary supplements, 7% use a supplement for eye health.2

The Age-Related Eye Disease Study (AREDS) primary analysis of the influence of nutritional supplements on AMD progression included patients with categories 2 (minimal), 3
(intermediate), and 4 (advanced in the nonstudy eye) AMD. These patients were assigned to treatment with placebo, antioxidants (b-carotene, vitamin C, and vitamin E), zinc (80 mg
daily), or antioxidants plus zinc. The AREDS investigators concluded that, for patients with category 3 or 4 AMD, antioxidants plus zinc reduced the 5-year risk of progression to
advanced AMD by 25% and produced a 19% reduction in severe vision loss.3 The Age-Related Eye Disease Study 2 (AREDS2) showed that omega-3 fatty acids or the alternate
carotenoids, lutein and zeaxanthin, did not improve upon the original AREDS formulation.4 However, lutein and zeaxanthin are safe and effective substitutes for b-carotene—a known promoter
of lung cancer risk in smokers.4 The AREDS or AREDS2 formulations are recommended currently for people with intermediate AMD in both eyes or with intermediate AMD in 1 eye and advanced AMD in the fellow eye.

The AREDS AMD trial was designed to study the progression of patients with established AMD. Patients in the AREDS trial with category 1 (no AMD, total drusen area <63 mm) were
thought to be at low risk for vision loss from AMD and were not included in the AMD trial. These patients were enrolled in the AREDS cataract trial and were randomized to treatment
with placebo or antioxidants to study the impact on cataract progression. Patients in the AREDS cataract trial were not treated with zinc or antioxidants plus zinc, because AREDS
investigators had no reason to suspect that zinc would reduce the risk of progression of lens opacities.3 Retinal outcomes were recorded, enabling a study of antioxidant treatment as
primary prevention of AMD. We previously reported the results of a genetic subgroup analysis of AREDS patients, concluding that complement factor H (CFH) and age-related maculopathy sensitivity 2 (ARMS2) genetic polymorphisms may predict response to antioxidants and/or zinc, the major components of the AREDS formulation. 5 Others have also studied the relationship between nutritional supplementation and genetic risk alleles in patients with AMD and have reached differing conclusions. 6-12 We identified an adverse response to the AREDS
formulation, compared to placebo, in patients homozygous for CFH genetic risk and without ARMS2 genetic risk. Based on this evidence, we concluded that genotype-directed nutritional
therapy for individuals with intermediate AMD could lead to an overall reduction in the incidence of advanced AMD. A more recent analysis of over 4000 eyes of patients
enrolled in the AREDS has confirmed the presence of a significant interaction between CFH and ARMS2 genetic risk and treatment with antioxidants plus zinc for patients with intermediate
to unilateral advanced AMD.13 Given evidence of the interaction between genetic risk factors and nutritional supplements in the progression of intermediate to advanced AMD, we now investigate the potential for interaction between antioxidants, genetic polymorphisms, and the de novo development of intermediate AMD among individuals enrolled in the AREDS cataract trial. The long and detailed observation and documentation of progression of these patients provide a useful data set with which the interaction of genetics, antioxidant therapy, and the development of intermediate AMD can be evaluated. Dietary antioxidants have been shown to have a differential impact on the progression of AMD based on a conventional allele dosage model of total CFH and ARMS2 risk allele number. 14 We chose to analyze the impact of antioxidant supplementation on AMD development using a similar approach, based on total CFH and ARMS2 genetic risk allele number.
Methods
Patients were derived from the AREDS population. Study procedures have been reported previously.15 Patient consent was given to permit genetic samples to be used for eye diseases only or for
general research use. Patients were characterized by AREDS investigators at enrollment with time course retinal images classified by a central reading center, allowing determination of the
time interval from study enrollment to AMD progression.15 Patients with AREDS category 1 disease were enrolled only in the AREDS cataract trial and were randomized to treatment with
either placebo or antioxidants (b-carotene 15 mg, vitamin C 500mg, and vitamin E 400 IU). Retinal phenotype was documented with fundus photographs at 12-month intervals. Since genetic risk
factors for AMD have been best characterized in white persons,we restricted our analysis to this group.
Genotyping
Targeted sequencing was performed on over 3000 samples from the AREDS and Universities of Michigan and Pennsylvania samples as described elsewhere.16 The short-read
sequences were matched to Genome Reference Consortium Build 37 (GRCh37) assembly before being deposited into the dbGaP database of the National Institutes of Health (NIH). We
obtained the aligned sequences from dbGaP service using NIH’s SRA toolkit (version 2.5.4). The read sequences for the
CFH (chromosome 1) and ARMS2 (chromosome 10) loci were processed using the SAMtools package (http://www.htslib.org) to deduce unphased genotypes at single-nucleotide polymorphic
(SNP) variants in the CFH genomic region (rs1061170, rs3766405, rs1410996, rs412852) and 1 SNP
(rs10490924) in the ARMS2 region (http://www.htslib.org). To validate the sequencing data and the deduced SNP genotypes obtained via dbGAP database, we identified 139 AREDS cases for whichDNAwas available fromthe Coriell Institute (Camden, New Jersey). Genotyping on this subset of cases was performed by Beckman Coulter Genomics (Danvers, Massachusetts) using bidirectional Sanger dideoxy sequencing. Genotypes from the same group of patients from these 2 sources were directly compared, resulting in complete concordance.

Source: Zanke Family HX.pdf

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