This older adult patient with vision difficulties should be referred to an eye professional. Vision impairment is common in older adults, and unlike in younger patients, older patients are more likely to have conditions such as glaucoma, macular degeneration, or diseases of the vitreous body or retina. An undilated ophthalmoscopic examination in the primary care setting is insufficient to diagnose these eye disorders. Evaluation for glaucoma involves measurement of intraocular pressure (tonometry), which is not available in most clinicians' offices, and other conditions involving the vitreous body or retina require eye dilation and examination with a slit lamp to allow for full evaluation. Additionally, the relatively rapid change in this patient's otherwise stable vision is suggestive of an acute or rapidly progressive process. Therefore, timely referral to an eye professional is the most appropriate next step in managing this patient's vision symptoms.

Obtaining an erythrocyte sedimentation rate is necessary in patients with suspected giant cell arteritis; however, this patient does not present with symptoms of headache, muscle aches, or jaw claudication, making the pretest probability of giant cell arteritis very low. Therefore, obtaining an erythrocyte sedimentation rate is not indicated at this time.

Visual screening tests, such as the Snellen eye chart or the pinhole test, are used primarily to assess for presbyopia. Although these tests may be abnormal in this patient, they would not sufficiently evaluate other potentially serious visual conditions that may be present.