Infant Eye Exams

In our Vision Science class during first year, Dr. Pang and Dr. Allison stopped by and perform eye exams on our professor’s three young grandchildren.

For a baby, the eye exam starts the moment the doctor walks into the room: The clinician pays close attention to the baby, watching the child as they look at the doctor, look at their parents, shift their gaze around the room, etc. Even at three months of age, a baby should be able to track an object up to 10 inches from them; if not, there may be an indication of a neurological deficiency. The best time to do an infant eye exam is first thing in the morning, when the baby is wide awake, fed and ready for their day.

Visual attention is an important cue and the baby should be able to follow an object or person moving around the room. In our class, the babies were six months and six weeks of age, and I can imagine that their attention was difficult to monitor with all the faces in the class looking at them. Watching the baby track an object, such as a bottle or rattle, is very important. Because a baby is a non-verbal patient at this point, the parents will become the key source of information and will usually notice if something seems not quite right; most commonly they’ll notice either an eye turn, or that the eyes aren’t tracking objects well.

Teller acuity cards, www.stereooptical.com

Teller acuity cards, www.stereooptical.com

How a baby’s vision quality is assessed
The traditional procedures for determining visual acuity can’t be used on a baby for obvious reasons–they can’t exactly tell you which one is better? One or two? An interesting way the profession has gotten around this is through the use of Teller acuity cards. The card has two sections: One section has a striped pattern, known as gratings, that varies from card to card; the other section is a uniform gray. Between the sections is a peephole that the clinician can use to view the baby’s response to the card, while keeping their face hidden. If the baby spends more time looking at the gratings than the uniform gray, that means they can visually detect the pattern presented to them.

Once it’s determined the baby is looking at the gratings, the clinician will move on to a finer grating, to determine the limits of acuity. As soon as the baby chooses to look at the uniform gray instead of the gratings, we know it has gone beyond the limits of their detection. A similar technique for measuring acuity in infants is using LEA paddles, which work the same way as the Teller cards; the difference is that Teller cards hide your face. A baby will always choose to look at a face over anything else because it is much more interesting to them–it’s one of the obstacles in doing infant eye exams.

In the class demonstration, we encountered a limitation when determining acuity: We weren’t sure whether the babies were done looking at the gratings because they couldn’t detect the pattern, or because they were preoccupied with all of the students staring.

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A common entrance test done as part of the exam sequence is the cover test,which allows the doctor to check the alignment of the eyes. This test is most commonly done using an occluder to cover each eye, one after the other, at a rapid rate while the patient fixates on an object of interest. For the baby eye exam, this technique has been altered to be much quicker–the clinician uses their thumb instead of the occluder and it seems to work well.

OKN drum, www.bernell.com

OKN drum, www.bernell.com

One of the techniques used to evaluate the network of nerves connecting the eyes to the brain–the cortical system–is to use the optokinetic drum. The OKN drum has black and white stripes on it so that when spun,a particular involuntary eye motion will follow the stripes if the patient is able to detect the grating.  This drum can be used either horizontally or vertically, and provides information to the optometrist regarding the quality of the cortical system.

How a baby’s prescription is determined
A technique called retinoscopy is used as an objective test to determine the approximate refractive error of the eye.  Depending on the brightness and speed of the light reflecting back out of the eye, the doctor can estimate if this is a +1D or a +10D refractive error, and begin to neutralize it with a set of skiascopy bars.  It is most common for young babies to have +1D to +1.5D refractive error and in most cases, the refractive error is monitored.

How ocular health is assessed
During the ocular health portion of the eye exam, one must be creative to keep the baby’s attention where it is needed while still getting all the pertinent information. For example, the clinician can play a peek-a-boo game with the baby and the Burton lamp (which provides light, magnification and a cobalt filter). This lamp allows the clinician to view the front surface of the eye and check for scratches on the cornea.

It’s common practice to dilate your little patients. Once their eyes are dilated, the clinician can use the BIO (binocular indirect ophthalmoscope) to view the entire retina from central to farthest periphery, and assess the health of the back of the eye. It’s helpful to perform this procedure while the baby is drinking from a bottle so they can lie back make that their focus!

If the baby presents visual conditions, at the end of the exam the doctor will prescribe glasses in the cases of high refractive error, or choose to monitor. In the case of a healthy baby, it’s common practice to see the baby on an annual basis. It’s important for the clinician to work efficiently during an infant eye exam, so the patient doesn’t tire before the doctor is finished.

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