If a patient cannot see the big "E" on the Snellen chart, what notation is acceptable?

When assessing visual acuity using the Snellen chart, if a patient cannot see the largest letter, which is typically the big "E," the notations 20/200 and 20/400 are often used. The notation 20/400 represents a level of vision where the patient can see at 20 feet what a person with normal vision can see at 400 feet. This notation indicates a significant level of visual impairment.

The important aspect of notation for patients who cannot see the big "E" is that these measurements help convey the extent of their visual limitations. The specific choice of 20/400 in this case suggests that the vision is severely reduced, requiring alternative methods for assessing acuity or visual function. For practitioners, recognizing such notations assists in determining further treatment or referral options.

In this context, the other choices of 20/200 and 20/100 would imply a lesser degree of visual impairment compared to 20/400; therefore, they do not align with the situation of a patient unable to perceive the top letter on the chart as accurately. The choice of 20/20 reflects normal vision, which would not apply here since the patient cannot identify the large letter.