The highest test that the child is capable of performing should be used; in general, the tumbling E chart should be used for children aged 3 to 5 years and Snellen letters or numbers for children aged 6 years and older. 2. Testing distance of 10 ft (3 m) is recommended for all visual acuity tests.
http://www.aafp.org/afp/1998/0901/p691.html
Baby's First Eye Exam. An infant should receive his or her first eye exam between the ages of 6 and 12 months. Even if no eye or vision problems are apparent, at about age 6 months, you should take your baby to your doctor of optometry for his or her first thorough eye examination.
http://www.aoa.org/patients-and-public/good-vision-throughout-life/childrens-vision/infant-vision-birth-to-24-months-of-age
(Right) “Tumbling E” chart. For children in kindergarten or first grade, the Snellen letter or number charts represent the gold standard for in-office assessment of visual acuity. Children usually stand 10 ft (3 m) away from the visual chart to minimize the distraction that may occur in a busy office.
http://www.aafp.org/afp/1998/0901/p691.html
Babies also like objects with high contrast, such as black-and-white bull’s-eye patterns, checkerboards, and concentric circles of contrasting colors. It is good for your baby to have different things to look at, and she enjoys it when you occasionally change the objects in her environment.
https://www.healthychildren.org/English/ages-stages/baby/Pages/Your-Baby's-Vision-1-Month.aspx
The highest test that the child is capable of performing should be used; in general, the tumbling E chart should be used with children aged 3 to 5 years and Snellen letters or numbers with children aged 6 years and older. 2. Testing distance of 10 ft (3 m) is recommended for all visual acuity tests. 3.
http://www.aafp.org/afp/1998/0901/p691.html
1 Although an infant's color vision is not as sensitive as an adult's, it is generally believed that babies have good color vision by five months of age. 2  Most babies start crawling at about 8 months old, which helps further develop eye-hand-foot-body coordination.
http://www.aoa.org/patients-and-public/good-vision-throughout-life/childrens-vision/infant-vision-birth-to-24-months-of-age
1 Their primary focus is on objects 8 to 10 inches from their face or the distance to parent's face. 2  During the first months of life, the eyes start working together and vision rapidly improves. 3  Eye-hand coordination begins to develop as the infant starts tracking moving objects with his or her eyes and reaching for them.
http://www.aoa.org/patients-and-public/good-vision-throughout-life/childrens-vision/infant-vision-birth-to-24-months-of-age
Before birth, your baby was accustomed to a dark, muted environment. The fetus’ eyelids fuse (close) during week 10 of gestation and remain closed until about 26 weeks’ gestation. Newborn infants generally have poor eyesight and little ability to focus beyond 6 or 10 inches away. The amount of color vision is not known for certain, but infants probably do not see subtle differences in color until 2 to 3 months of age. 1  If your baby is born with closed eyelids, no special precautions or treatments are necessary. 2  The lids will open on their own within a short time, or by around 26 weeks.
https://www.healthychildren.org/English/ages-stages/baby/Pages/Your-Baby's-Vision-1-Month.aspx
Initially, your baby may not be able to look at you and follow your face, but as she grows and remains awake for longer periods, her eyesight will improve. Position your baby face-to-face about 6 to 10 inches away.
https://www.healthychildren.org/English/ages-stages/baby/Pages/Your-Baby's-Vision-1-Month.aspx
Birth to four months. Up to about 3 months of age, babies' eyes do not focus on objects more than 8 to 10 inches from their faces. 1  At birth, babies' vision is abuzz with all kinds of visual stimulation.
http://www.aoa.org/patients-and-public/good-vision-throughout-life/childrens-vision/infant-vision-birth-to-24-months-of-age
vision distance for infants
The vision distance for infants is 6 or 10 inches away.