What is the first step if your patient is unable to read the largest letter on the Snellen chart?

When a patient is unable to read the largest letter on the Snellen chart, the appropriate first step is to ask the patient to count fingers. This action allows for a quick assessment of the patient's visual acuity at a more basic level, providing important information about their ability to perceive light and shapes, even when they cannot read the letters on the chart. This step helps determine if the patient has some level of functional vision or if further examination is necessary.

Other options, such as asking the patient to cover one eye or checking for color vision, would not effectively address the immediate concern of the patient’s visual capability in this scenario. Covering one eye could provide misleading information if the patient has significant visual impairment in both eyes. Checking for color vision is not relevant in this initial assessment because it doesn't help evaluate the basic visual acuity needed to establish a baseline for further testing. Scheduling a follow-up exam might be necessary depending on findings, but it is not a direct action that helps in assessing the current situation accurately.