What You'll Get
- Comprehensive Eye Exam with $100 Towards Prescription Eyeglasses or Sunglasses
20/20 Vision: An Imperfect Ratio
The included eye exam will determine your visual acuity, which compares your vision to the 20/20 standard. Read on to find out what this metric really means.
Possessing 20/20 vision may be considered perfect, a level of visual acuity reserved for Navy pilots and the bald eagles that train them, but in fact it’s not even close to average. Developed by Dutch optometrist Hermann Snellen in the 1860s, the 20/20 standard is a somewhat arbitrary distinction. After inventing his now-iconic eye chart—which consists of lines of standardized letters that get progressively smaller—Snellen also instituted the concept of a ratio to define the clarity of a patient’s vision. The denominator represents how many feet away a person of normal visual acuity could stand while still discerning the letters with the same level of clarity as the patient. In other words, 20/40 vision means the patient needs to stand 20 feet away to make out the same size letters as a person with standard vision can from 40 feet.
Because the 20/20 standard is arbitrary, many people actually have considerably better eyesight, represented by such ratios as 20/15 or 20/10. In fact, in the United States, the average visual acuity is sharper than 20/20 until about age 60 or 70, when people’s vision naturally starts to decline as their bangs finally grow past their eyes. Also, though it’s useful for determining basic shortcomings of vision, an eye chart can’t diagnose a proper glasses or contact prescription. To determine that, optometrists test many other factors, including depth perception, peripheral vision, x-ray vision, and focusing skills.
The Fine Print
Promotional value expires 120 days after purchase. Amount paid never expires. Consultation required; non-candidates and other refund requests will be honored before service provided. Appointment required. Merchant’s standard cancellation policy applies (any fees not to exceed the price paid for the voucher). Limit 1 per person, may buy 1 additional as gift. Not valid for contact lenses. excludes off the shelf sunglasses. May be repurchased every 30 days. Merchant is solely responsible to purchasers for the care and quality of the advertised goods and services.