{
 "topic": "Visual Impairment",
 "slug": "visual-impairment",
 "category_id": 15377,
 "summary": "Pediatric visual impairment: acuity-based grading, the developed-vs-developing world etiology split, cortical visual impairment as the leading cause in developed countries, and infancy red flags for early detection.",
 "written_by": "claude-sonnet",
 "references": [
  {
   "title": "AAP Developmental and Behavioral Pediatrics",
   "author": "AAP Section on Developmental and Behavioral Pediatrics,Robert G. Voigt,Michelle M. Macias ,Scott M. Myers ,Carl D Tapia",
   "pages": [
    283,
    284,
    285,
    291,
    298
   ]
  },
  {
   "title": "Kliegman R. Nelson Textbook of Pediatrics 2-Volume Set 22ed 2024",
   "author": null,
   "pages": [
    3953
   ]
  },
  {
   "title": "Cover",
   "author": "Vitalsource Download",
   "pages": [
    8744
   ]
  },
  {
   "title": "Illustrated Textbook of Paediatrics (Tom Lissauer, Will Carroll)",
   "author": "Lissauer, Tom,Carroll, Will",
   "pages": [
    73
   ]
  },
  {
   "title": "Pediatric Decision-Making Strategies",
   "author": "Pomeranz, Albert J.",
   "pages": [
    42
   ]
  },
  {
   "title": "CURRENT Diagnosis and Treatment Pediatrics, Twenty-Fourth Edition",
   "author": "Hay, William W., Levin, Myron J., Deterding, Robin R., Abzug, Mark J.",
   "pages": [
    497
   ]
  }
 ],
 "short": [
  {
   "title": "In short",
   "content": "- Severe visual impairment is defined as corrected vision poorer than 6/60 (20/200); blindness is worse than 6/120 (20/400). Overall incidence of severe visual impairment/blindness in children is about 2.5 per 100,000, higher in developing countries, low-birthweight infants, and the first year of life.\n- Worldwide (2015 estimate), about 1.14 million children age 0-16 were blind or severely visually impaired (acuity worse than 20/400), and roughly 17.5 million children (2010 estimate) had \"low vision\" (acuity 20/60 to 20/400).\n- In developed countries, the leading causes of childhood blindness/severe visual impairment are cerebral/cortical visual impairment (CVI), sequelae of extreme prematurity (retinopathy of prematurity), and genetic conditions; in developing countries, infections (trachoma, toxoplasmosis, onchocerciasis) and nutritional deficiency (vitamin A deficiency) predominate.\n- Among US preschoolers, the most common causes of severe visual impairment in decreasing frequency are: CVI, retinopathy of prematurity, optic nerve hypoplasia, structural eye abnormalities, and albinism.\n- CVI is the single most frequent cause of visual impairment in young children in developed countries and results from impaired brain interpretation of visual signals (posterior visual pathways) rather than an ocular abnormality; the eye exam (pupillary responses, eye movements) can be entirely normal.\n- Amblyopia is the most common cause of unilateral, preventable, permanent visual impairment in developed countries, affecting up to 5% of children and adults worldwide.\n- In a UK study, up to 50% of childhood visual impairment had an underlying cerebral cause, and about one-third was hereditary (eye-structure disorders).\n- Red flags for early detection: persisting wandering nystagmus and poor visual regard/tracking by 3-6 months of age; persisting excessive tearing and eye redness, significant strabismus, or leukocoria (white pupil) in the first 1-2 years.\n- Vertical nystagmus is associated with posterior fossa lesions; nystagmus should be characterized by waveform, direction, amplitude, frequency, velocity, and symmetry, often requiring neuroimaging, electroretinogram, or visual evoked potential testing.\n"
  }
 ],
 "long": [
  {
   "title": "Definition",
   "content": "Visual impairment in children is graded by best corrected visual acuity: normal vision is 20/20-20/30 (6/9 or better); slight visual impairment 20/40-20/50 (6/12-6/15); visual impairment 20/60-20/100 (6/18-6/30); severe visual impairment 20/200-20/400 (6/60-6/120); and blindness is worse than 20/400 (6/120). Severe visual impairment/blindness may result from defects at any point along the visual pathway, from the eye itself through the optic nerve to the cerebral visual pathways.\n"
  },
  {
   "title": "Epidemiology",
   "content": "The overall incidence of severe visual impairment and blindness in children is approximately 2.5 per 100,000, higher in developing countries, in low-birthweight infants, and in the first year of life. Worldwide, an estimated 1.14 million children from birth to 16 years were blind or severely visually impaired (acuity worse than 20/400) as of 2015, with roughly 17.5 million children having \"low vision\" (acuity between 20/60 and 20/400) as of 2010. Reported prevalence varies substantially with definitions used, surveillance methods, and a population's economic circumstances, and much of the world lacks robust epidemiological data. The relative importance of different causes also differs by setting: in developed countries, CNS-related conditions (cerebral/cortical visual impairment), sequelae of extreme prematurity, and genetic conditions predominate, while in poorer, developing countries, infections (trachoma, toxoplasmosis, onchocerciasis) and nutritional deficiencies (particularly vitamin A deficiency) are more prevalent causes.\n"
  },
  {
   "title": "Etiology",
   "content": "Causes are classified by timing of onset. Prenatal causes include genetic conditions, fetal malformations, prenatal infection, and hypoxia; abnormalities may be isolated to a single eye or brain structure (e.g., iris coloboma), affect multiple parts of the visual system (e.g., oculocutaneous albinism), or occur as part of a multisystem syndrome (chromosomal, such as Down syndrome; metabolic; or epigenetic, such as CHARGE syndrome). Perinatal causes include CNS hypoxia-ischemia, retinopathy of prematurity, and infection. Postnatal causes include amblyopia, tumors, nutritional deficiency, trauma (including nonaccidental trauma from abuse), infection, raised intracranial pressure, and systemic conditions. Among US preschoolers, the leading causes of severe visual impairment in decreasing order of frequency are cortical visual impairment (CVI), retinopathy of prematurity, optic nerve hypoplasia, structural eye abnormalities, and albinism. In the Nelson Textbook's account, prenatal and perinatal causes predominate overall, most often affecting the cerebral visual pathways, optic nerve (hypoplasia, atrophy), or retina (Leber congenital amaurosis); important prenatal causes include microphthalmia/anophthalmia, genetic disorders (autosomal recessive most common, also autosomal dominant and X-linked), hypoxia, and chromosomal syndromes, while perinatal/neonatal causes include retinopathy of prematurity, hypoxic-ischemic injury, and infection. Visual impairment beginning in older children may result from CNS or retinal tumors.\n"
  },
  {
   "title": "Pathophysiology",
   "content": "Cortical visual impairment (CVI), also called cortical blindness, occurs when visual signals from the retinas and optic nerves are not accurately or consistently interpreted by the brain's posterior visual pathways - either temporarily, as in delayed visual maturation, or permanently. It can result from generalized cerebral damage or targeted injury to the occipital lobes or visual association pathways, commonly from perinatal hypoxia, prematurity, hydrocephalus, congenital CNS anomalies, trauma, intracranial hemorrhage, or periventricular leukomalacia. Because the eye itself is often structurally normal, pupillary responses, eye movements, and the eye examination can all be entirely normal in CVI, and dysfunction ranges widely in severity and frequently coexists with other neurodevelopmental disorders.\n"
  },
  {
   "title": "Clinical Features",
   "content": "Affected infants with CVI show poor eye contact, failure to fixate on or follow a visual target, and unresponsiveness to visual threat; wandering or roving eye movements and nystagmus are common, and eye-poking is seen in some infants with low vision. In ocular causes of impairment beginning in infancy, caregivers typically notice persisting wandering nystagmus and poor visual regard/tracking by 3-6 months of age; other findings prompting attention in the first 1-2 years include persistent excessive tearing and eye redness, significant strabismus, and leukocoria (a white pupillary reflex). Amblyopia, by contrast, is often insidious and unsuspected without systematic screening. Nystagmus should be characterized as rhythmic/swinging versus nonrhythmic, along with waveform, direction, amplitude, frequency, velocity, and symmetry between the eyes; some patterns carry diagnostic significance, such as vertical nystagmus, which is associated with posterior fossa lesions (and occasionally drug-induced nystagmus).\n"
  },
  {
   "title": "Diagnostics",
   "content": "Early detection by primary pediatric health care professionals is critical, both for conditions treatable to prevent permanent vision loss and for those requiring early tailored educational and environmental support. Evaluation of nystagmus or suspected low vision may require neuroimaging and specialized testing such as electroretinogram and visual evoked potential/response testing; referral to ophthalmology, and sometimes genetics and neurology, is appropriate to determine etiology.\n"
  },
  {
   "title": "Treatment",
   "content": "Some vision-impairing conditions, if detected early enough, can be treated medically or surgically to prevent permanent or significant loss of visual function. When no medical or surgical treatment exists, early detection followed by tailored educational interventions, environmental modification (larger print, reduced glare, increased contrast), low-vision devices to maximize residual visual function, and family support services can substantially improve a child's learning, functional independence, and social-emotional adjustment.\n"
  },
  {
   "title": "Complications",
   "content": "Because visual impairment is a relatively low-incidence disability, often with neurological comorbidities, much of the expanding research knowledge about its developmental implications has been slow to reach medical and educational practice. A majority of causes of childhood blindness are, in fact, preventable or treatable, underscoring the value of early identification and referral to specialized services.\n"
  }
 ],
 "clinical": [
  {
   "title": "Early Detection in Primary Care",
   "content": "Screen visual behavior at every well-child visit, since early detection of significant visual impairment - and of conditions that risk permanent vision loss if untreated - is one of the primary care clinician's most important responsibilities here. By 3-6 months of age, persisting wandering nystagmus or poor visual regard/tracking should prompt urgent ophthalmology referral. In the first 1-2 years, treat persistent excessive tearing and eye redness, significant strabismus, and leukocoria (white pupillary reflex) as red flags requiring prompt evaluation. Remember that amblyopia - the most common cause of unilateral, preventable, permanent visual impairment in developed countries, affecting up to 5% of the population - is often insidious and will not be caught without systematic vision screening, so do not rely on parental observation alone to exclude it.\n"
  },
  {
   "title": "Working Up Nystagmus or Suspected Cortical Visual Impairment",
   "content": "When evaluating abnormal eye movements, characterize them as rhythmic/swinging versus nonrhythmic, and describe waveform, direction, amplitude, frequency, velocity, and symmetry between the two eyes, noting any associated nonocular muscle movement - vertical nystagmus in particular raises concern for a posterior fossa lesion. If an infant has poor eye contact, fails to fixate and follow, is unresponsive to visual threat, or shows wandering/roving eye movements with a normal eye exam (normal pupillary responses and eye movements on structural exam), consider cortical visual impairment from perinatal hypoxia, prematurity, hydrocephalus, congenital CNS anomaly, trauma, intracranial hemorrhage, or periventricular leukomalacia. Refer to ophthalmology to determine etiology, and pursue electroretinogram, visual evoked potential testing, brain imaging, and genetics/neurology consultation as indicated. Once a vision-impairing condition without medical or surgical treatment is identified, arrange early referral for tailored educational intervention, environmental modification, low-vision devices, and family support services rather than delaying care while awaiting a precise etiologic diagnosis.\n"
  }
 ]
}