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Modifiable risk factors and AMD
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There are various genetic and environmental risk factors in the development and progression of AMD. Patient age and genetic risk factors cannot be changed. Environmental risk factors, such as smoking, body mass index (BMI) and diet, are modifiable (Table1.). The interaction of genes with modifiable risk factors will likely play a significant role in the management of AMD in the future. It is important for ophthalmologists to know the patient’s genotype in order to modify the patient’s lifestyle and improve visual results.
Interaction of genes and environment
The gene variant that ophthalmologists are most concerned about is the complement factor H (CFH) gene. The CFH gene accounts for nearly 70% of AMD, whether it is geographic atrophy or choroidal neovascularization (CNV).1 In addition, LOC387715 is a mitochondrial protein that is expressed in the retina and is associated with other modifiable risk factors.
Compounded risk
Patients who have a variant of the CFH gene and are homozygous are three times more likely to develope AMD, geographic atrophy or CNV than are normal subjects. Patients who are homozygous for the LOC387715 variant are four times more likely than normal subjects to develop AMD.2
| Patients who are homozygous for the LOC387715 gene and smoke are 22 times more likely to develop AMD. — Elias Reichel, MD | ||
Patients who have both copies of the CFH gene and a high BMI are 12 times more likely to develop AMD. Patients who are homozygous for the LOC387715 gene and smoke are 22 times more likely to develop AMD. The risk of AMD is high in patients who have both copies of the “bad” genes and one of the modifiable risk factors.3
These numbers are good for patients when used as motivational tools to modify their lifestyle. Patients who are told they are 22 times more likely to develop AMD will likely be motivated to make improvements regarding the modifiable risk factors, no matter how difficult those changes may be. It is important for ophthalmologists to educate their patients about these modifiable risk factors that may have a role in affecting their genetic diseases.
Ophthalmologists are concerned about geographic atrophy and CNV in patients with AMD. Geographic atrophy and CNV are the severe endpoints of AMD disease process, and high-risk patients are susceptible to this endpoint.
Risk factor screening
| Once the genotype is determined, it is important to encourage follow-up visits with those patients dependent on their calculated risk. — Elias Reichel, MD | ||
A high-risk screening is important to identify the risk factors that may have an impact on the development of AMD. Ophthalmologists treating patients who are smokers or who have a high BMI need to determine the genotype of those patients. Once the genotype is determined, it is important to encourage follow-up visits with those patients dependent on their calculated risk. Patients who, for example, are 22 times more likely to develop CNV or geographic atrophy should be followed up more closely than a patient with a lower risk of developing those diseases.
Future role
In the future, ophthalmologists will play a significant role in identifying people at high risk for developing end-stage AMD. Identifying people and risk factors may start at a very young age as patients need to be educated about their genotype so they can change any environmental risk factors. Ultimately, ophthalmologists are going to work with other health care providers, such as primary care doctors, endocrinologists and cardiologists in trying to prevent blindness in patients who are highly susceptible.
References
- Lotery A, Trump D, Progress in defining the molecular biology of age related macular degeneration. Human Genetics. 2007;122:219-236.
- Seddon JM, Francis PJ, Gearge S, et al Association of CFH Y402H and LOC387715 A69S with progression of age-related macular degeneration Association of CFH Y402H and LOC387715 A69S with progression of age-related macular degeneration. JAMA. 2007;297:1793-1800.
- Schaumberg DA, Hankinson SE, Guo Q, et al. A prospective study of 2 major age-related macular degeneration susceptibility alleles and interactions with modifiable risk factors. Arch Ophthalmol.2007;125:55-62.