Sensory Impairment

Visual Impairment

The most common visual problems in prematurely born infants result from Retinopathy of Prematurity (ROP).  Retinopathy of Prematurity is a condition in which the blood vessels in the retina develop abnormally.  It is most common in babies born more than 12 weeks early.  The growth of blood vessels in the retina is normally completed just a few weeks before the normal time of delivery, and when babies are born before this process is complete the vessels may grow and branch abnormally.  The abnormal vessels can actually cause the inner lining of the retina to be pulled away from the outer lining.

Over one-half of patients with resolved ROP develop ophthalmological problems of some type.  Up to 80% of those with scarring from ROP develop near-sightedness.  These children are also at increased risk for blurred vision and various types of unequal vision in the two eyes.

ROP is not the only risk factor for vision difficulties in prematurely born infants.  Grades III and IV intraventricular hemorrhage are strongly associated with vision problems.  Some types of vision problems, including strabismus and amblyopia, are more common in prematurely born infants even without a history of brain bleeds or ROP.  It is also possible to have visual impairment due to damage to the part of the brain that processes visual input or due to optic nerve damage interfering with transmitting visual input to the brain.

Vision screens in the first year are valuable in early detection of vision problems, but early screens cannot rule out later vision problems.  Because vision problems are known to increase for some extremely prematurely born children between 12 and 24 months of age (Page, et. al. 1993), a second vision screen at age two is warranted.  Certainly, any time a parent suspects vision difficulty, a vision exam should be requested.

Some Signs of Possible Vision Problems

• Infant is behind with developmental milestones, for visual tracking and following
• Infant is behind with motor milestones
• Infant moves too little or seems uninterested in moving about
• Infant visually follows objects which make noise, but does not follow without sound
• Difficulty getting or keeping eye contact with an infant
• Infant tilts head to the side frequently (after good head control is established)
• Anything unusual in the appearance of the eyes (including red eyes, frequent rubbing of the eyes,  drooping eyelids, wandering eye, crossed eyes, rapid back-and-forth movements of the eye when  the infant is at rest, unequal appearance of the eyes, jerky eye movements, unusual eye coloring or dull appearance of eyes, etc.)
• Older infants may seem poorly coordinated, move into things unexpectedly and show little interest in visual stimuli such as books, television, balloons, and balls.

Hearing Loss

Between 3-25% of very low birth weight infants will develop mild to moderate hearing loss.  A smaller percentage (1-3%) will be profoundly deaf.  Certain neonatal illnesses and early exposure to ototoxic drugs may result in hearing loss that appears later in infancy, and therefore would not be identified through NICU hearing screens.  Frequent ear infections not only increase the risk of intermittent conductive hearing loss due to fluid in the ears, but chronic ear infections can also result in long-term damage to hearing.

Assessment of hearing can be complicated for children with partial hearing loss.  Hearing loss for certain frequencies or other relatively mild forms of hearing loss can interfere with speech development.  Intermittent hearing loss, associated with recurrent ear infections, is also thought to interfere with speech and language development.  It is also possible to have intact hearing at a sensory level (e.g., the ear is working properly), yet to have a problem with the part of the brain that interprets the signals from the auditory nerve.  This results in auditory processing problems which can be as or more disabling than actual hearing loss.

The earlier hearing problems are detected and treated, the more successful are outcomes.  The American Academy of Pediatrics recommends universal screening for hearing impairment for all newborns and repeated screenings for infants at high risk for delayed onset hearing loss.  Any child with behavior suggestive of hearing loss should have an audiological examination.

Behaviors Suggestive of Possible Hearing Loss

• Infant does not respond to sounds (becoming more still and quiet is a normal response to sound for very young infants; and it is also normal for a child to stop responding to the same sound after a few repetitions.)
• Infant turns to follow visual stimuli, but not to locate sounds.
• Infant  does not babble or stops babbling after a period of normal babbling.
• Older infant does not respond to his/her name.
• Any delays in onset or progression of language skills.
• Unusual vocal quality.
• Unusual articulation errors after child begins to use words

Tactile and Sensory Integration Difficulties

Parents and therapists frequently note that many prematurely born children tend to have unusual reactions to certain types of touch and textures. The hands, feet, and/or mouth may appear to be particularly over- or under-sensitive, and unusual taste preferences are also frequently reported. The behavior of some children suggests vestibular and/or proprioceptive dysfunction. The cause of unusual sensory reactions in prematurely born children is not well-understood. Various theories include early stimulation of the immature nervous system altering or damaging the developing nerve connections, early traumatic or painful experiences in the NICU contributing to psychological aversion or increased tolerance to certain types of touch or sensations, or early brain injury resulting in a change in the way the brain perceives sensory input. For most children, the unusual sensory reactions are benign and appear to resolve with maturity. For a few children, abnormal responses to certain types of stimuli are so severe as to interfere with other aspects of their development. Children with neurological damage are more likely to have extreme and long-term sensory difficulties. All children with sensory dysfunction deserve to have their sensory issues addressed seriously.

Tactile

Unusual sensitivity of the palms of the hands and soles of the feet are the most often reported, but many former premature infants have increased or decreased sensitivity to touch for other areas as well. Reactions to different types of touch vary from one child to another. A commonly reported pattern includes an apparent high tolerance for pain together with a low tolerance for light touch. A child with this pattern may not cry over a badly skinned knee, yet find the light scratch of clothing labels unbearable. In extreme cases, over-sensitivity can prevent a child from using the hands to explore objects or from walking flat on bare feet.

Some suggestions for parents of children with tactile sensitivity issues:

1. Make an effort to determine exactly what is different about your child's sensory reactions. Does he or she prefer light or firm touch? Are there certain textures in materials or even foods that are consistently avoided? Do the things your child avoids share common characteristics?
2. As long as it does not create a major inconvenience for other people and does not interfere with age appropriate activities, try to respect your child's unusual sensitivities. Minor adjustments (removing tags from clothing, avoiding abrupt temperature changes, reducing overall stimulation, etc.) may reduce anxiety and frustration surrounding the problem.
3. If the child's sensitivities are so extreme as to interfere with daily activities considered normal for a child of his or her developmental level, ask your primary medical care provider for a referral to an occupational therapist.
4. Look for alternative materials that will allow your child to move forward in other areas of development. 

Ideas For Children With Tactile Sensory Issues:

• If the ridges in the toes of socks bother your child, try turning them inside out.
• Try removing labels from clothes that some children finding irritating.
• If your child has trouble excepting foods with new textures, try adding tastes they already like as you gradually change the texture of the food.
• Many children who will not accept a new texture (with the hands or mouth) from someone else, are much more willing if they are allowed to have control over the material or food.  That is, make the material or food available and let the child decide when and how to touch it or taste it.
• Make sure that the child gets much more praise and attention for trying new things than for avoiding them.  (For example, if you find yourself spending most of your meal time fussing over the child for NOT eating, make a conscious effort to change your strategy to praising any small attempts and ignoring avoidance.  Try not to talk about the child's unusual avoidant behaviors when the child is around; but make opportunities to mention and praise any new positive behavior.)

Sensory Integration Dysfunction

Difficulty processing and/or integrating information received through the senses is sometimes referred to as "Sensory Integration" (SI) dysfunction. Some professionals define SI dysfunction broadly to include all forms of alterations in sensitivity or sensory processing difficulties (even only one type of sensation is involved). More frequently, SI dysfunction is applied to problems in integrating different types of sensory information. Very sophisticated sensory integration is required to see an object and associate the sight with the sound it makes and the way it feels to the hands when touched. Another example of complex sensory integration is the ability to judge one's own body position relative to other objects seen visually while moving about a room.

Children who have difficulties integrating information they receive simultaneously from two or more senses may appear exceptionally cautious and unsure of themselves. They may be slow to reach certain developmental milestones due to a reluctance to try new activities (including walking, climbing, and jumping). As social interaction requires especially complex sensory processing (including making sense of visual cues, understanding the spoken language and interpreting nuisances of vocal characteristics, judging one's own body positioning and controlling nonverbal responses while producing appropriate verbal responses), social difficulties are common among children with sensory integration dysfunction.

Some occupational therapists have specialized training in treating these problems. Research on the effectiveness of sensory integration therapy has yielded inconsistent results. Some parents report much success with SI therapy, but others do not see an improvement. Questions regarding when and how long SI therapy should be conducted, which types of sensory integration dysfunction respond best to SI therapy, how long the benefits last remain unanswered at present. At present, the efficacy of SI therapy must be determined on a case-by-case basis. If you think your child may benefit from help in this area, begin by asking your child's pediatrician for a referral to an occupational therapist who has experience in SI therapy. A developmental psychologist or special education teacher who has training and experience with prematurely born children may also be able to provide therapy or direct you to someone in your area who can.