Pediatric Low Vision

Key points at a glance

Key points of this disease

• Pediatric low vision refers to irreversible visual impairment in individuals under 21 years of age that cannot be improved by refractive correction, treatment, or surgery.
• A best-corrected visual acuity (BCVA) of 20/40 (0.5) or worse in the better eye is the diagnostic criterion.
• In developed countries, cerebral visual impairment (CVI) is the most common cause of pediatric visual impairment, accounting for up to 48% of severe pediatric visual impairment and blindness in the UK.
• The visual acuity test method varies by age; Teller Acuity Cards are recommended for infants, and LEA symbols for children aged 4–7.
• Comprehensive management by a multidisciplinary team is essential, with low vision aids and visual rehabilitation as the mainstays of treatment.
• Visual impairment is often mistaken for intellectual or learning disabilities, and early appropriate support greatly influences development.

1. What is Pediatric Low Vision?

Pediatric low vision refers to irreversible vision loss or permanent visual impairment in individuals under 21 years of age that cannot be improved by refractive correction, medical treatment, or surgical intervention.

The specific diagnostic criteria are as follows.

• BCVA 20/40 (0.5) or worse: Best corrected visual acuity in the better eye
• Reduced contrast sensitivity: If contrast sensitivity is less than 1.4 log units, even BCVA 20/30 (0.6) or worse qualifies as low vision
• Visual field constriction: Visual field less than 20 degrees

Regarding the epidemiology of childhood visual impairment in developed countries, cerebral/cortical visual impairment (CVI) is known as the most common cause. According to a WHO report (2001), central nervous system diseases account for 28% of childhood blindness in developed countries, and in the UK, CVI is reported to account for up to 48% of severe childhood visual impairment and blindness. ²⁾

Other major causes include nystagmus, optic atrophy, and optic nerve hypoplasia. According to the IRIS registry, the most common cause of visual acuity less than 20/200 in the better eye is retinopathy of prematurity (ROP).

Visual impairment can be mistaken for intellectual or behavioral disabilities, and early accurate diagnosis and support greatly influence developmental outcomes.

Q What level of visual impairment qualifies as pediatric low vision?

A

The criterion is a best-corrected visual acuity (BCVA) of 20/40 (0.5) or less in the better eye. If contrast sensitivity is less than 1.4 log units, a BCVA of 20/30 (0.6) or less also qualifies, and a visual field of less than 20 degrees is also included.

2. Main Symptoms and Clinical Findings

Subjective Symptoms

Signs of visual impairment vary by age. The main signs by age group are shown below.

Age	Main Signs
Birth to 4 months	Decreased sensitivity to bright light, absent or delayed blink reflex, delayed social smile, nystagmus
5 to 8 months	Lack of eye contact, poor fixation on objects or faces, strabismus
9 to 24 months	Unawareness of own hands, lack of purposeful hand or arm movements
24 months or older	Clumsiness during crawling, holding objects close to face, difficulty climbing curbs or stairs
School age	Difficulty reading, complaints of headache

Delays in gross and fine motor skills are also important clues for visual impairment. Difficulty reading may be mistaken for a learning disability.

Q What are some signs of low vision in infants and young children?

A

From birth to 4 months, absence or delay of blink reflex and delayed development of social smiling are observed. At 5–8 months, lack of eye contact and poor fixation; at 9–24 months, not noticing hands and lack of purposeful movements are signs. Delays in gross and fine motor skills are also important signs suggesting visual impairment.

Clinical Findings

Clinical findings characteristic of CVI are shown below. ²⁾

• Variability of visual function: Temporarily decreases due to epilepsy or poor physical condition, causing difficulty in visually complex environments.
• Crowding effect / simultanagnosia: 41% of children with CVI show a crowding ratio of 2.0 (4% in non-CVI children).
• Relative preservation of color vision: Due to bilateral color representation.
• Decreased contrast sensitivity: Causes dissociation between daily visual function and visual acuity
• Prolonged latency of visually guided eye movements: Delayed saccades and fixation
• Visual field defects: Show individual patterns depending on the lesion site
• Photophobia and paradoxical light gazing: The latter is presumed to result from thalamic damage

Higher-order visual cognitive impairments (Dutton classification) include recognition disorders (prosopagnosia: 15 of 20 cases), topographic agnosia, depth perception disorder (astereocognosis), motion perception disorder (akinetopsia), and simultanagnosia. ²⁾ Dorsal stream dysfunction may also present as visuomotor integration disorder and optic ataxia.

3. Causes and Risk Factors

The causes of childhood low vision are diverse. The main causes are classified below.

Ocular Structural Abnormalities and Eye Diseases

• Corneal opacity, congenital cataract, primary aphakia
• Choroidal coloboma, optic nerve hypoplasia, foveal hypoplasia
• Limbal stem cell deficiency, congenital nystagmus, aniridia
• Retinal dystrophy, trauma, iatrogenic injury

Hereditary and systemic syndromes

Representative syndromes and their main ocular symptoms are shown below.

Syndrome	Main ocular symptoms
Leber congenital amaurosis	Nystagmus, high hyperopia, poor accommodation, photophobia
Stargardt disease	Central vision loss, photophobia, color vision abnormalities, delayed dark adaptation
Retinitis pigmentosa	Night blindness, progressive peripheral visual field loss, tunnel vision
Achromatopsia	Reduced BCVA, color vision deficiency, photophobia, nystagmus
Oculocutaneous albinism	Optic nerve/foveal hypoplasia, nystagmus, strabismus, photophobia
Axenfeld-Rieger syndrome	Pupillary deviation, polycoria, glaucoma
Bardet-Biedl syndrome	Delayed dark adaptation, photophobia, loss of central vision and color vision
CHARGE syndrome	Chorioretinal coloboma, cataract, ptosis, strabismus
Hurler syndrome	Corneal opacity, retinitis pigmentosa, optic disc swelling, glaucoma
Lowe syndrome	Congenital cataract, corneal keloid, infantile glaucoma
Stickler syndrome	Vitreous liquefaction, retinal tear/detachment, pathologic myopia
Sturge-Weber syndrome	Choroidal hemangioma, glaucoma
Usher syndrome	Night blindness, progressive peripheral vision loss

Cerebral Visual Impairment (CVI)

CVI is the most common cause of visual impairment in children in developed countries. ²⁾

• Most common cause: Hypoxic-ischemic encephalopathy (especially in preterm infants)
• Other causes: Epilepsy, hydrocephalus, trauma, infections
• Pathophysiology: Damage to the visual pathways posterior to the lateral geniculate nucleus, with retrograde trans-synaptic degeneration affecting the anterior visual pathways
• It also occurs in some genetic syndromes.

4. Diagnosis and Examination Methods

Medical History Taking

A detailed medical history is essential for accurate assessment.

• Onset, severity, and progression details
• Family history of visual impairment
• Impact on daily activities and psychosocial effects
• History of low vision aid use
• Difficulty with near work and mobility
• Importance of the child’s participation (self-advocacy)

For children with developmental delay, select an examination method appropriate for their developmental age.

Visual acuity testing

The gold standard is logMAR testing (near and distance) using age-appropriate optotypes. Testing with a single optotype may overestimate visual acuity due to the crowding phenomenon.

0–36 months

Teller Acuity Cards: Gold standard. Validated even in children with low vision. Utilizes infants’ preference for striped patterns (PL method).

Grating acuity card method (TAC, Cardiff card): Can be easily performed in outpatient settings.

Morisane Dot Card: Possible from around 2 years of age. Performed at a distance of 30 cm. Since children with intellectual disabilities or physical disabilities often have difficulty pointing to small dots, a useful alternative for children who understand the concept of “which one” is to present both a 0 card and a card with an eye and let them choose.

VEP (Visual Evoked Potential): Shows higher values than PL visual acuity and OKN visual acuity, and can directly evaluate occipital cortex responses. OKN visual acuity estimates: newborn 20/400, 6 months 20/100, 1 year 20/60.

4–7 years

LEA Symbols: Applicable to pre-literate children. Picture and figure optotypes can be measured from 2.5 to 3.5 years old.

Landolt C / HOTV: Used for children learning letters. The success rate for Landolt C is 60% at age 3 and 95% at age 4.

Single optotype visual acuity 1.0 achievement rate: 67% at age 3, 75% at age 4, 85% at age 5, and nearly 100% at age 6.

Note: Distinguishing between single optotype and crowded optotype visual acuity is difficult until around 8–10 years of age (crowding phenomenon).

8–13 years

LogMAR Chart: The most suitable test for this age group.

Examination of children with nystagmus: Evaluate monocular visual acuity using blur with plus lenses or translucent occlusion.

Developmental considerations: Near visual acuity develops before distance visual acuity.

Q How is visual acuity measured in children with low vision?

A

Recommended examination methods vary by age. For 0–36 months, Teller Acuity Cards or grating acuity cards are recommended; for 4–7 years, LEA symbols or Landolt C rings; for 8–13 years, LogMAR charts. Since testing with a single optotype overestimates visual acuity, it is important to use methods that maintain crowding.

Visual Field Testing

• Confrontation visual field testing: Fixation on a central object plus peripheral colorful targets (easily applicable to children)
• Kinetic perimetry (Goldmann): Possible from about 6 years old. Excellent for detecting scotomas.
• Static automated perimetry (Humphrey, Octopus): Rapid and accurate.

Contrast Sensitivity Testing

It provides important clues to explain the discrepancy between visual acuity and daily visual function.

• Hiding Heidi Test: Uses 4 contrast levels (1.25% to 100%) plus a blank card, total 5 cards.
• Pelli-Robson test: For older children. Performed at a distance of 1 meter.

Color Vision Test

• Ishihara test (detection of red-green color vision deficiency)
• Farnsworth D-15 test, MRM test (for children with low vision)

Evaluation of Refraction and Accommodation

Children with low vision have a high frequency of refractive errors, and cycloplegic refraction is particularly important. Because children have strong accommodation, refraction using cycloplegic agents is necessary. Accommodative ability is assessed with dynamic retinoscopy, and if impairment is present, consider adding bifocal correction. Eye protection with polycarbonate lenses should also be considered.

Additional Tests

• OCT, electroretinogram, VEP (performed under sedation or general anesthesia if necessary)
• CVI assessment: caregiver questionnaire, fMRI, diffusion tensor MRI, genetic testing²⁾

5. Standard treatment

Comprehensive management by a multidisciplinary team

Management of pediatric low vision requires multidisciplinary collaboration. The team members are as follows.

• Pediatric ophthalmologist, optometrist
• Occupational therapist, vision rehabilitation therapist
• Assistive technology trainer, orientation and mobility instructor
• Psychologist, vocational counselor

Q What professionals are involved in managing pediatric low vision?

A

A multidisciplinary team centered on a pediatric ophthalmologist and optometrist, including occupational therapists, vision rehabilitation therapists, assistive technology trainers, orientation and mobility instructors, psychologists, and vocational counselors, is involved. Comprehensive support tailored to the child’s developmental stage and living environment is important.

Low vision aids (near vision aids)

• Single-vision spectacle magnifiers: Useful for near tasks, but unnatural posture may lead to poor posture and neck strain.
• Handheld and stand magnifiers: Used depending on the task.
• Monocular telescopes: Used for distance visual tasks.

Electronic Low Vision Devices

• CCTV (Closed-Circuit Television) magnifiers: Display magnified images on a screen. Offer highest magnification but are costly.
• Smartphone apps and AI technology: Utilize voice assistants such as Siri and Alexa.
• Audiobooks, screen readers, and speech-to-text: Support for reading and writing difficulties

Electronic visual devices providing 5–10× magnification have been reported to improve perceptual learning outcomes in children with moderate to severe visual impairment. ¹⁾

Glare control

• Tinted lenses
• Special absorption filters and glasses with side shields

Support in daily life and at school

The following are effective as adaptive support at school.

• Use of large-print books and bold writing utensils
• Ensuring a tilted desk and appropriate lighting
• Use of tablets and e-book readers
• Braille labeling (combined with fixed placement of household items)

In Japan, there are three types of school placements: regular classes, special needs classes, and special needs schools. For children with very severe visual impairments, even if they have multiple disabilities, it is important to connect early with the educational consultation services of a regional special needs school for the visually impaired (school for the blind). It is recommended that the medical information provided to the school include specific details such as visual acuity, refractive error, necessity and usage of glasses, presence of strabismus and binocular vision, eye movements, visual field, color vision, need for light shielding, need for seating considerations, and the size of textbook characters.

Psychosocial Support

Children with low vision frequently have mental health concerns. Major triggers include reduced mobility, dependence on caregivers, limited leisure activities, and fewer opportunities for social development. Symptoms in children may manifest as physical complaints such as headaches, nightmares, irritability, and cognitive changes.

Important coping strategies include social support from family, teachers, and friends, professional counseling, and promoting independence. Early self-advocacy education is also recommended.

Treatment Considerations

The effectiveness of low vision aids varies depending on the underlying disease and the degree of visual impairment. Selection of aids should be based on individual assessment by a multidisciplinary team, and regular re-evaluation is necessary. Aids that force unnatural postures may lead to postural deterioration and orthopedic problems with long-term use.

6. Pathophysiology and Detailed Mechanisms of Onset

Stages of normal visual development

Visual development begins immediately after birth, and functions are acquired in stages.

• Birth to 4 months: Adaptation to light, focusing on objects in front of the eyes
• 5 to 8 months: Development of depth perception (stereopsis), face recognition
• 9 to 12 months: Hand-eye coordination, establishment of gross spatial awareness
• First 2 years of life: Building the ability to explore objects in the environment

Near visual acuity develops before distance visual acuity. Impairments during this developmental process determine the functional impact of low vision.

Pathophysiology of CVI

The main pathophysiological features of CVI are as follows. ²⁾

• Most common cause: Damage to the post-geniculate visual pathways due to hypoxic-ischemic encephalopathy (especially in preterm infants)
• Retrograde trans-synaptic degeneration: Damage to the posterior visual pathways also affects the anterior visual pathways (lateral geniculate body and retinal ganglion cells)
• Predominant dorsal stream impairment: The dorsal stream (where pathway) is more susceptible to damage than the ventral stream.
• “Blindsight”: A phenomenon related to extrageniculate visual pathways or reorganization of the visual system
• Motion perception deficits: Abnormal detection of optic flow, global/biological motion

For contrast sensitivity after congenital cataract, it has been reported that a contrast increase of 1 to 1.5 log units is required across the entire visual field.

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7. Latest Research and Future Perspectives (Reports at Research Stage)

For patients: Please be sure to read

The following content is currently at the research stage or in clinical trials and is not standard treatment available at general hospitals. It is reference information for professionals regarding future medical developments.

Viewing Strategy Research in Children with Visual Impairment

It has been systematically clarified that eye movement patterns in children with visual impairment differ from those with normal vision. ¹⁾

In a systematic scoping review by Fonteyn-Vinke et al. (2022), it was reported that the reaction time to visual stimuli in children with ocular visual impairment (VI) was delayed by 170±28 ms, and in children with CVI by 232±36 ms. In children with VI who have reading difficulties, increased fixation count, prolonged fixation duration, reduced saccade amplitude, and disorganized eye movement strategies are observed, whereas normal readers show similar eye movement patterns across lines. Increased fixation area is also observed in children with low vision and nystagmus. ¹⁾

Perceptual Learning

Perceptual learning is attracting attention as a new rehabilitation intervention for children with visual impairment. ¹⁾

Computerized crowded letter discrimination training has been reported to improve reading acuity and critical print size. In paper-based perceptual learning, transfer to crowded near visual acuity was confirmed only in the crowded training group. Near visual acuity, stereopsis, and crowding improved, and the effects were sustained. Using electronic vision devices (5–10× magnification) further enhances perceptual learning effects in children with moderate to severe visual impairment. ¹⁾

Visual Attention Span (VAS)-Based Training

Improvements in both VAS function and reading performance have been reported in children with VAS dysfunction and reading difficulties. ¹⁾ The training consists of the following three components.

• Length estimation task (promoting bottom-up attention)
• Visual search and digit cancellation (promoting top-down attentional modulation)
• Visual tracking (improving eye movement control)

Viewing strategy and attention networks

Viewing strategy has been shown to be associated with three attention networks. ¹⁾

• Alerting network: Color cue support is effective
• Orienting network: Holistic gaze strategy is effective for facial expression recognition and reading
• Executive network: Training of structured eye movement patterns is effective

Advances in CVI management

Visual stimulation therapy and stem cell therapy have been proposed as treatments for CVI. ²⁾ The potential of evaluation using new neuroimaging techniques such as fMRI and diffusion tensor MRI is also being studied.

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8. References

1. Fonteyn-Vinke A, Huurneman B, Boonstra FN. Viewing Strategies in Children With Visual Impairment and Children With Normal Vision: A Systematic Scoping Review. Front Psychol. 2022;13:898719.

2. Chang MY, Borchert MS. Advances in the evaluation and management of cortical/cerebral visual impairment in children. Surv Ophthalmol. 2020;65:708-724.

3. Kim S, Rachitskaya A, Babiuch A, Eisenberg M, Ghasia F, Sears J, et al. Characterization of pediatric low vision and socioeconomic determinants of health at an academic center: a 5-year analysis. J AAPOS. 2024;28(6):104033. PMID: 39522590.