Diagnosis and Associated Risk Factors

When evaluating a patient who shows signs and symptoms that suggest age-related macular degeneration (AMD), it is important to conduct a comprehensive adult medical eye evaluation, paying special attention to those aspects that are relevant to AMD.¹

Risk factors for AMD

Common in older adults, age is the most significant risk factor for AMD, with the prevalence increasing with age.^2–5

Smoking is the environmental factor that is most strongly associated with AMD, particularly neovascular AMD (nAMD), increasing the risk of atherosclerosis that can affect the choroidal vessels of the eye. Nicotine also promotes inflammation and angiogenesis through the upregulation of vascular endothelial growth factor (VEGF). Patients who smoke cigarettes are twice as likely to develop AMD as nonsmokers; however, quitting smoking can lower both the risk and severity of the condition.^3,6,7,8

Symptoms of AMD

People at higher risk for AMD should have increased vigilance for symptoms of AMD to allow for earlier detection and treatment, which can offer improved outcomes.^2,3,8 Symptoms of AMD include central blurring, metamorphopsia, decreased vision, scotoma, photopsia, colors appearing faded, and difficulties in dark adaptation, and can change as the disease progresses:^2,3,6

Early AMD is often not noticed by many people, other than noticing increasing difficulty seeing in low-light situations
Intermediate AMD symptoms can include a blurry spot in the center of patient’s vision, perception of less intense colors or contrast sensitivity, and increasing difficulty in low light
Advanced, or late-stage AMD, can present as worsening or distorted visual acuity, central vision loss, and difficulty in recognizing faces

Screening and monitoring for AMD

The American Academy of Ophthalmology (AAO) recommended frequency for adult comprehensive medical eye examinations for asymptomatic patients, and for patients who do not have risk factors for eye disease, is under 40 years–every 5 to 10 years; 40 to 54 years–every 2 to 4 years; 55 to 64 years–every 1 to 3 years; and 65 years or older–every 1 to 2 years.¹

Patients at higher risk should be evaluated more frequently^1,5:

Findings of macular drusen may be an incidental funduscopic finding that should prompt providers to refer patients with significant risk factors to an ophthalmologist.¹⁰

For a patient with AMD, more frequent retinal examinations are recommended, such as moving from a 12-month follow-up interval to a 6-month interval to monitor disease progression, or every 3-4 months for those who are progressing rapidly or at high risk for choroidal neovascularization (CNV).³

Patients with the onset of new symptoms, such as new visual loss, metamorphopsia, or scotoma, should be examined promptly. Any sudden loss of vision (days up to a week) should be evaluated within 48 hours; visual changes occurring over weeks to months should be assessed nonurgently at the next available appointment.^3,10

Making the diagnosis

The diagnosis of AMD usually is made clinically based on the patient’s history, symptoms, and a dilated eye exam using a binocular slit-lamp biomicroscopy of the ocular fundus to detect drusen, abnormalities in the retinal pigment epithelium (RPE), geographic atrophy (GA), CNV, subretinal fluid (SRF), and hemorrhage.⁶

Clinicians should obtain a thorough history for symptomatic patients to assess the onset of visual symptoms, whether one or both eyes are affected, and if the vision loss involves far vision, near vision, or both. The physical examination should include visual acuity, visual fields by confrontation, external eye and lid assessment, pupillary function, extraocular movement, and a funduscopic evaluation.¹⁰

An optometrist or ophthalmologist can use different imaging tests to assess, diagnose, and classify AMD, as well as to monitor treatment and disease progression.^3,10,11

Optical coherence tomography (OCT) is a noninvasive imaging technique that provides high-resolution, cross-sectional images of the retina, retinal nerve fiber layer, and the optic nerve head. OCT can be used to determine the presence of subretinal and intraretinal fluid and retinal thickening and is used to monitor progression and therapeutic responses to therapy in patients with nAMD. Home-based OCT scanning could be used to monitor disease progression and treatment efficacy, potentially alleviating some of the burden involved with managing AMD.^3,10,11
Fluorescein angiography should be performed on patients suspected of having choroidal neovascularization based on symptoms or findings on physical examination. This includes patients complaining of new metamorphopsia or unexplained blurred vision; those with findings of macular edema, subretinal blood, elevation of the RPE on examination; or those with OCT-detected fluid. Patients being considered for treatment with either photodynamic therapy or laser photocoagulation should have angiography to guide therapy and to evaluate recurrences after-treatment. The dye is injected intravenously as a bolus and a sequence of photographs are taken. Newly formed choroidal vessels leak fluorescein that appears on imaging; normal retinal vessels do not.^3,10,12

Fundus autofluorescence (FAF) is a non-invasive imaging modality that can identify areas of geographic atrophy and can be used to monitor these areas for disease progression. This test also allows for identification of lipofuscin accumulation in the RPE. Atrophic RPE typically appears as dark patches in FAF, and some patterns may predict faster rates of geographic atrophy. Green-light FAF images may be superior to blue-light to accurately determine small, central, pathologic changes, and central atrophic lesion boundaries.^3,10,13,14

Pathophysiology of AMD