Pediatric Low Vision

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Pediatric low vision is defined as irreversible vision loss or permanent visual impairment in a person younger than 21 years old, which cannot be improved with refractive correction, medical treatment, or surgical intervention.[1] Pediatric low vision can result in challenges with reaching developmental milestones, obstacles to education, difficulty with social interactions, and loss of independence. In the pediatric population, low vision may be mistaken for intellectual disability or may be masked by concomitant systemic health issues that obscure its diagnosis. Therefore, a keen understanding of how to detect and manage pediatric low-vision can have an important and lifelong impact on this young patient population.


Definition of Pediatric Low Vision

Pediatric low vision, as defined by the American Academy of Ophthalmology’s Preferred Practice Patterns for Vision Rehabilitation, is irreversible vision loss or impairment in a person under 21 years old, which cannot be improved with refractive correction, medical treatment, or surgical intervention.[1] Specific parameters include a best-corrected visual acuity (BCVA) of 20/40 (the minimal visual acuity required for driving in many states) or worse in the better-seeing eye.[2] Low vision can also be characterized as a BCVA of 20/30 or better if contrast sensitivity is lower than 1.4 log units in an individual having difficulty performing everyday tasks such as reading, driving, or recognizing faces due to visual limitations.[3]


Causes of Pediatric Low Vision

The etiologies for low vision in the pediatric population are many and varied. For example, pediatric low vision may be due to a primary ocular structural abnormality, secondary to other ocular pathology, develop as one of the ophthalmologic manifestations of a genetic or systemic syndrome, or may occur as a result of cortical visual impairment (CVI). Limited epidemiologic data to date cite nystagmus, optic atrophy, optic nerve hypoplasia, and CVI as some of the most common causes of pediatric low vision.[4]

Structural abnormalities affecting any part of the eye, from front to back, may contribute to pediatric low vision. Examples include, but are not limited to, the following: corneal opacification, congenital cataract, primary aphakia, chorioretinal coloboma, optic nerve hypoplasia, and foveal hypoplasia. Ocular pathology such as limbal stem cell deficiency, congenital nystagmus, aniridia, retinal dystrophy, trauma, and iatrogenic damage can result in, or contribute to, low vision.[1][4]

The list of genetic and systemic conditions associated with pediatric low vision is extensive. Some of the more common syndromes include Leber congenital amaurosis, Stargardt disease, Retinitis Pigmentosa, Achromatopsia, and ocular or oculo-cutaneous albinism. Other less common but well-known syndromes that may be associated with pediatric low vision include, Axenfeld-Rieger, Bardet Biedl, CHARGE, Hurler, Lowe, Stickler, Sturge Weber, and Usher syndrome. A more extensive list of genetic conditions and their ocular manifestations leading to low vision can be found in Table 1.[5][6]

Table 1. Genetic and systemic syndromes associated with pediatric low vision[5][6]

Genetic or system condition Ocular manifestations contributing to low vision
Leber congenital amaurosis nystagmus, high hyperopia, reduced accommodative capacity, photophia
Stargardt disease central vision loss, photophobia, color vision deficit, delayed and/or reduced dark adaptation
Retinitis Pigmentosa night blindness, progressive peripheral visual field restriction, tunnel vision
Achromatopsia reduced BCVA, impaired color vision, photophobia, nystagmus
Oculo-cutaneous albinism optic nerve and/or foveal hypoplasia, nystagmus, strabismus, photophobia, refractive error
Axenfeld-Rieger Syndrome correctopia, polycoria, glaucoma
Bardet-Biedl Syndrome delayed and/or reduced dark adaptation, photophobia, loss of central and color vision
CHARGE Syndrome chorioretinal coloboma, cataract, ptosis, strabismus, microphthalmia, microcornea
Hurler Syndrome corneal clouding, retinal pigmentary degeneration, optic nerve head swelling, glaucoma
Lowe Syndrome congenital cataract, corneal keloid, infantile glaucoma
Stickler Syndrome optically empty vitreous, retinal tear or detachment, pathologic myopia
Sturge Weber Syndrome choroidal hemangioma, glaucoma
Usher Syndrome night blindness, progressive peripheral visual field loss

CVI in the absence of other ocular disease, may also be associated with pediatric low vision.1 CVI most commonly presents due to pre- or perinatal hypoxia, and can also be seen in the setting of some genetic syndromes.[7][8] CVI results from retrograde transsynpatic degeneration causing damage to the anterior visual pathways.[7][8] This damage most often manifests as visual field defects with loss of visual acuity. Other ocular manifestations of CVI include refractive error, reduced contrast sensitivity, and optic atrophy.[7][8] Any of these factors, or in combination, contribute to pediatric low vision.


Signs of Low Vision in Children

A child’s visual development is marked by specific milestones. From birth to approximately four months of age, an infant begins adjusting to light and focusing on objects in front of them.[9] From five to eight months depth perception and facial recognition become part of a child’s visual behavior. From nine to twelve months, babies begin to demonstrate hand-eye coordination and gross spatial recognition as they become mobile with crawling.[9] These skills build through the first two years of life allowing children to explore other objects of interest in their environment such as toys and foods.[9]

Knowing the key steps in normal visual development at a young age therefore helps to highlight early signs of delayed visual development. Table 2 outlines the signs of normal and delayed visual development according to a child’s age.[9][10] Decreased sensitivity to bright lights, delayed or absent eye contact, slowed development of an intentional social smile, lack of awareness of an infant’s own hands, the absence of goal-directed hand movements, and failure to fixate on familiar objects such as toys and faces may all be warning signs to the parents and/or the pediatrician of low vision.[9][10]

Table 2. Signs of normal and impaired visual development according to age

Age Normal visual development Signs of visual impairment
Birth-4 months Focusing on and tracking familiar objects Decreased sensitivity to bright light, absent or delayed blink reflex, slowed development of intentional social smile
5-8 months Depth perception, facial recognition, color vision Delayed or absent eye contact, failure to fixate on objects or familiar faces
9-24 months Hand-eye coordination, grasping objects, crawling Lack of awareness of own hands, absence of goal directed hand and/or arm movements
>24 months Crawling, walking, exploring the environment Clumsiness with crawling, difficulty reaching toys, holding objects close to the face, problems navigating curbs or steps, frequent tripping
School-age Reading Difficulty with reading, complaints of headache

Once children become mobile, signs of low vision may be more obvious due to clumsiness with crawling, difficulty reaching for toys, and holding objects very close to the face. Older children may start to verbalize symptoms of blurry vision, eye strain or headaches.[1][9][10] When a child learns to walk, which may be delayed in the setting of low vision, signs of visual impairment can include problems navigating curbs or steps, frequently tripping over objects on the floor, or bumping into walls and objects in a room.[1] By school age children with low vision may present with difficulty in tasks such as reading, which may be mistaken for a learning disability.


Evaluation of Low Vision in Children

Ideally children should be referred for low vision assessment as early as possible. Most commonly, children are referred to ophthalmology around school age or once they are old enough to vocalize symptoms of blurry vision.[11] Some parents seek earlier ophthalmologic evaluation when they notice that their child’s visual behavior is abnormal or delayed. The components and order of the pediatric low vision exam vary depending upon the age of the child and their ability to participate. The overarching goal of the pediatric low vision exam is to obtain as much information as possible regarding the child’s visual functioning.

History

Taking time to obtain a thorough history regarding onset, severity and progression of low vision symptoms is critical. If the child is old enough, it is important to involve them as much as possible to encourage self-advocacy from an early age. For many patients, this will become increasingly important as they learn to protect their independence as their vision declines. In addition to standard history questions regarding timing of onset, severity, and progression of visual symptoms, the following components should be included in the pediatric low vision history:

  1. Family history of visual impairment
  2. Degree of impairment the child has in day-to-day activities
  3. Impact of visual symptoms on the child’s wellbeing and psychosocial functioning
  4. Prior use of low vision aids, including spectacles
  5. Difficulty with near tasks and or their mobility.

Visual Acuity

Visual acuity should always be measured with the child’s age, school performance, and cognitive ability in mind.[11] Gold standard low vision acuity testing requires near and distance logMAR testing using age appropriate optotypes (Figure 1).[11][12][13] Single line testing may overestimate visual acuity compared to the full chart test; however full chart tests may cause a “crowding” or “contour interaction” which can falsely underestimate results.[11][12][13] Near vision testing may be more reflective of the child’s functional vision and in many cases may be the only option if the child is unable to identify the largest optotype at distance.

Assessment according to age

Teller Acuity Cards

1. 0-36 months: Teller Acuity Cards are the gold standard for visual acuity testing in this age group and have been validated for children with low vision.[13][14] Teller acuity cards rely on the patient’s behavior and eye movements in response to being shown a series of cards with different gratings.[15]

2. 4-7 year old: LEA symbols have been validated for pre-literate children.[12][13] For older children who have started to learn letters, Landolt C or HOTV optotypes are more accurate measures for detecting refractive error.[12][13]

3. 8-13 year old: The LogMAR chart is the best option for children with low vision who are literate.[13]

Visual Fields

Visual field assessment in young children can be difficult; however, results are important for understanding the impact of low vision on a child’s mobility and orientation.

Confrontation visual fields: Testing should be performed by having the child focus on a central object, while moving colorful targets into the peripheral field. How far the peripherally moving objects travel before the child notices them is the border of the visual field.

Kinetic perimetry: In cooperative children over approximately 6 years old, Goldman visual field testing is preferable for objective delineation of any field loss and for detecting the presence of visual scotomas.[10][16]


Contrast Sensitivity

Results of contrast sensitivity testing may provide insight into a discrepancy between a child’s formal visual acuity testing and their day-to-day visual functioning as decreased contrast sensitivity may correlate with poor visual functioning despite relatively intact visual acuity.[10]

Hiding Heidi Test

Hiding Heidi Low Contrast Face Test: Four charts with contrast levels of 1.25%,2.5%,5%, 10%, 25%, 100%, and a blank card. Children are presented with two cards, one blank and another a cartoon face at a specific contrast level. Children are asked to identify which card has the cartoon image.[17] Hiding Heidi example

Pelli Robson Chart

Pelli-Robson test: For older children, this test can be performed at a distance of 1 meter (Figure 2).[18]

Color Vision

Assessing a child’s color vision may help explain difficulties with object recognition as well as anticipate future challenges with schoolwork. Red/green color vision is evaluated using the Ishihara test.[10] Other validated color vision tests for children with reduced visual acuity include the Farnsworth D-15 test, or the abbreviated Mollon-Reffin minimalist (MRM) test.[10][16][19]

Refraction and Accommodative Capacity

Near point of convergence. Photo courtesy of AAO.

Cycloplegic refraction, while included in any pediatric eye exam, is especially important in the pediatric low vision evaluation as this population has a high incidence of refractive error. In addition, even minor refractive correction can lead to improved quality of vision and visual functioning. Polycarbonate lenses are prescribed for the added benefit of eye protection. Lastly, dynamic retinoscopy prior to cycloplegia can be used to evaluate the child’s accommodative capacity, which if impaired, may prompt the addition of bifocal correction to aid with near work at school and near leisure activities.[10]

Additional Testing

In many instances, additional testing may be pursued to collect both anatomic and functional information about the child’s visual system. Such tests may include: ocular coherence tomography (OCT) of the optic nerve and/or macula, electroretinogram (ERG), and visual evoked potential (VEP). Depending on the test and age of the child, in hospital sedation may be required.

Management of Pediatric Patients with Low Vision

The approach to management will vary depending on the child’s age and level of visual impairment. Fortunately, there is a wide array of tools available from in-person approaches to advanced technology. An interdisciplinary team, with special attention to the psychosocial impact of low vision on a child, is critical for comprehensive and effective care. Low vision services help alleviate restrictions in social activities, sports, and other hobbies or leisure activities, thereby helping to improve quality of life.

An Interdisciplinary Team

May include, but not be limited to, a combination of the following:[20]

1. Pediatric ophthalmologist 2. Optometrist 3. Occupational therapist 4. Vision rehabilitation therapist 5. Assistive technology trainers 6. Orientation and mobility specialist 7. Psychologist 8. Vocational counselors

Near Vision Aids

Children who have poor near vision will often move closer and adopt an unnatural body position to view objects in more detail. This can be problematic overtime, as they can develop poor posture and strain on their neck. They may benefit greatly from a number of optical low vision devices to enhance their near vision including: single vision spectacle magnifiers, hand-held magnifiers, and monocular telescopes.[21]

Electronic Low Vision Devices

Electronic Video Magnifier

Video magnifiers (or closed-circuit television) systems use a mounted or handheld camera to project a magnified image onto a separate screen. They are ergonomically sound and offer the highest degree of magnification, but their cost may be prohibitive.[21] Smartphone applications, as well as artificial intelligence technology, have contributed significantly to the available assistive technology for individuals of all ages with low vision. For example, Siri and Alexa, operate using voice recognition and do not require visual cues or interaction. Audiobooks, screen readers for email and audio conversion for text messaging, are additional resources that can significantly impact individuals of all ages living with low vision. The American Foundation for the Blind offers a list of low vision assistive technology.

Glare Control

Individuals with low vision often experience photophobia for which tinted lenses both for near and distance can be prescribed. Tinted lens that come in different colors to provide contrast enhancement of objects in the environment. Furthermore, children who are sensitive to glare may benefit from glasses with special absorptive filters and side shields to filter out glare-producing light.[21][22]

ADL Assistance

Fostering independence with ADL’s from a young age is key for children with low vision. At home, consistent placement of items surrounding food preparation, hygiene and dressing helps a child develop systems for ADLs independent of visual cues. For children who have received instruction in braille, labeling of household items can help with certain tasks. At school, large print books, adaptive technology, bolded writing, sloped desks for closer working distance, optimal illumination, and even tablet/e-readers with font enlargement can enhance a child’s learning experience while at school.[21]

In both the home and school settings, occupational therapists can play a central role in helping a child with low vision optimize their gross and fine motor abilities needed for ADL independence.


Psychological Impact of Low Vision on Children

Children with low vision have a reportedly higher incidence of mental health concerns compared to their sighted peers.[23] Triggers may include reduced mobility, greater dependency on caretakers for day-to-day activities, limited participation in leisurely activities, and fewer opportunities for social development with peers.[23] Moreover, visual impairment can hinder a child’s ability to read facial expressions and learn to predict people’s behaviors, contributing to social isolation.[24][25]

Early detection of mental health concerns in children with low vision is crucial. Impaired mental health in children, unlike adults, may manifest with somatic symptoms such headaches, nightmares, irritable mood or changes in cognition.[23] Social support from family, teachers and friends, professional counseling, and a focus on maintaining a child’s independence are key to addressing mental health concerns. Furthermore, inclusion of the child in his or her own care as much as possible from a very young age is critical for optimizing low vision care. Children with low vision should be given the tools to learn how to advocate for themselves to further promote their independence and overcome future obstacles encountered during a lifetime with low vision.

Treatment Outcomes

There is well-documented evidence that gains in visual acuity, enhanced visual functioning, improved quality of life, and stronger academic performance in children can be achieved with appropriate and comprehensive low vision management.[26][27] Furthermore, early intervention with low vision services is associated with improved outcomes compared to low vision support initiated at school age.[26][27]

Evidence in the literature evaluating treatment outcomes following low-vision rehabilitation services for children is lacking and reports are largely limited to small studies or case series.[28][29] Available data confirm that a majority of children receiving mobility and orientation training demonstrate gains in food preparation skills, home management, orientation and mobility, and shopping skills.[29] With regards to fine-motor tasks, a study of 4-5 year old children were found to have improvement in performance speed and accuracy of a number of fine-motor exercises after twelve sessions of training with a stand magnifier.[28]

Knowledge and data surrounding low vision in children is growing. This area within pediatric ophthalmology clearly remains one of great interest and need.

References

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  15. Citation for Teller Acuity Card Image
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  17. Citation for Hiding Heidi Low Contrast Face Test
  18. Citation for Pelli Robson Chart Image
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