RAJESH.DODDA

The Pediatric Exam:
Examining kids is a difficult prospect, as children are moving targets and universally hate strangers messing with their eyes. You have limited time before your child further decompensates, so it’s important to hone in on any eye problems quickly.

                        Vision testing also depends upon the age of your patient. Young babies may only blink-to-light, but as the child gets older they start to track faces, and eventually identify pictures. It’s hard to measure quantitative vision in the young, so focus on asymmetry between the eyes. For example, cover each eye and watching how the child reacts and tracts. If a baby is fussier with a particular eye covered, then you may be covering his only good eye! Also, toddlers will cheat when covering the eyes, so watch them closely!

Refractive Error
Determining a child’s refractive error is even more challenging … how can you tell if a child is myopic or hyperopic when they can’t read the eye chart? Here’s how we do it:

Bruchner Test:
One quick method to estimate refractive error is by examining the red-reflex (the red-eye you get in photographs). Hold a direct scope from a distance and shine it so that the circle of light lights up both pupils at the same time.

Examine the red-reflex from each eye. Assuming that the child is looking right at you, the placement of the red-reflex gives some clues. Inferior crescents, such as in this drawing, indicate myopia (near-sightedness) while superior crescents indicate hyperopia.

Most children have some degree of hyperopia, as their eyes are small and still growing. This makes the Bruchner test more useful for picking up myopic (near-sighted) errors, but overall the test isn’t very accurate in undilated children as they have the ability to accommodate. Also, if the eyes are not well aligned, such as strabismus, the results are inaccurate.

Retinoscopy
Retinoscopy is a much more accurate way to check prescription, and is how we refract all pre-verbal children for glasses. By flashing a beam of light back-and-forth into the eye we can examine how the light bounces off the retina. By holding different power lenses in front of the eye we can figure out what power lens focuses the light properly and neutralizes the red-reflex. This is a difficult skill to learn, but surprisingly useful, even outside of the pediatric realm.
Amblyopia (a.k.a. “lazy eye”):
Amblyopia is decreased vision in an eye because of disuse of that eye during childhood development. The prevalence in the USA is 2-5%, the major risk factors being prematurity, developmental delay, and a family history.

The visual pathway is a plastic system that continues to develop during childhood until around 6-9 years of age. During this time, the wiring between the retina and visual cortex is still developing. Any visual problem during this critical period, such as a refractive error or strabismus (misaligned eyes) can mess up this developmental wiring, resulting in permanent visual loss that can’t be fixed by any corrective means when they are older.

How to Detect:
As you can imagine, you want to pick up amblyopia at an early age. Unfortunately, it is exactly these younger children who’s vision is most difficult to check. Pediatricians always check vision as part of a well-baby exam, and schools perform vision screenings – but vision assessment in children is tricky, even for trained ophthalmologists. We get many false-positive “poor vision” referrals from these sources, but that’s ok, because early detection is important!

The word “lens” is named after the lentil plant (greek name Lens culinaris) whose 2 – 9 mm disk-shaped seeds bear a remarkable resemblance in size and shape to the human lens.

The lentil legume was one of the first agricultural crops and was grown over 8,000 years ago. Introduced in the U.S. during the early 1900’s, the “lentil bean” is grown in drier Washington, Idaho, and Western Canada and the seeds can be used in soups, stews, casseroles and salad dishes.

Strabismus:
Strabismus describes when the eyes are not aligned with each other, such as when an eye is turned in (cross-eyed or esotropic) or turned out (wall-eyed or exotropic). Here are some terms we use in ophthalmology to describe misalignments:

Esotropia (ET): The eyes are turned inwards (cross-eyed) all the time.
Exotropia (XT): The eyes are turned outwards (wall-eyed) all the time.
Eso/Exo-phoria: Phorias are eye deviations that are only present some of the time, usually under conditions of stress, illness, fatigue, or when binocular vision is interrupted

 Detecting Strabismus in babies

A quick way to check alignment inbabies is to shine a penlight into their eyes. You can determine alignment by looking at the corneal-pupil light reflex (the light reflection off the cornea) to make sure it is centered over the pupil of each eye. A large percentage of newborn infants will have some tropia at birth that goes away within a few months.

Don’t be fooled by pseudostrabismus – this is the illusion of crossed eyes caused by nasal epicanthal skin folds found in many Asian and young children. On casual inspection of these children, less white sclera is seen nasally and the child “looks cross-eyed.” However, closer inspection will reveal normal corneal light reflexes and no refixation on cover testing. Children outgrow these epicanthal folds as the bridge of the nose becomes more prominent.

With younger children who don’t track well, you can use the Hirschberg’s test – a quick method to estimate the amount of prism deviation in a misaligned eye. For every mm the corneal light reflex is off center, equals approximately 15 diopters of prism.

You can pick up phorias and tropias with the cross-cover test. Since the cross-cover test breaks binocular vision, the phoric eye will wander off axis when it has nothing to focus on. The amount of deviation can be quantified using prisms. This is a difficult technique to describe in words … basically you alternately cover the eyes with a paddle and hold up prisms until the deviation is neutralized. Detecting and measuring tropias and phorias is much more complicated then this, but I think this is enough for now!

Strabismus as a major cause of amblyopia

If a child has misaligned eyes, they can unconsciously suppress one of their eyes to avoid seeing double. However, this suppression leads to amblyopia and permanent visual loss. Adults don’t have this ability to suppress vision and if they develop strabismus (such as from a nerve palsy or trauma) they will permanently see double.

Treatment of Strabismus:

                   Before taking anyone to surgery, correct all the non-surgical causes of strabismus: check for refractive error and treat any amblyopia - many cases of strabismus will improve or resolve by just doing these things. Eye surgery consists of shortening or relaxing the extraocular muscles that attach to the globe to straighten the eye.

Strabismus Surgery

                 To correct simple esotropias (cross-eyed) or exotropias (wall-eyed) we can weaken or strengthen the horizontal rectus muscles. A recession-procedure involves disinserting the rectus muscle and reattaching the muscle to the globe in a more posterior position. This effectively weakens the action of this muscle and turns the eye accordingly.