AMAUROSIS (BLINDNESS)

Amaurosis denotes severe or complete loss of vision due to organic causes, which may be primary (congenital) or secondary (acquired) (Table 26.15). Blindness at birth or in early life may be easily missed due to lack of clinical symptoms, difficulties in vision assessment and delayed appearance of objective signs, e.g.

Perception of light (PL), i.e. blinking or papillary conญstriction on exposure to torchlight and Projection of rays (PR), i.e. movement of gaze or head towards the light source are two commonly used tests to detect blindness in newborn or early infancy.

TABLE 26.14: Assessment of vision in children

Newborn - 6 months

• Pupillary reflex

• Fixing and following light

• Corneal light reflex (for strabismus)

6 months - 3 years

• Reach-out to colored objects

• Preferential looking tests (Teller acuty cards)

• Retinoscopy

• Electrophysiological tests:

- Pattern induced visual evoked response

- Optokinetic response to a moving object

• Cover test (for strabismus)

3 years - 5 years

• Picture tests and matching cards (Kays symbols)

• Tumbling E or HOTV cards

• Cover test (for strabismus)

Above 6 years (Conventional tests)

• Snellen's chart (alphabet, tumbling E, landolts-C)

• Visual field assessment

• Color-vision test

TABLE 26.15: Causes of blindness in children

Congenital (primary) blindness

• Congenital ocular defects

- Congenital cataract

- Congenital glaucoma

- Retinal defects: Leber congenital retinal amaurosis

- Optic nerve aplasia/hypoplasia or coloboma

- Others: Corneal opacities, microphthalmia

• Congenital CNS malformations

- Porencephaly, hydranencephaly, encephalocele

• Intranatal/perinatal injuries

- Intrauterine (TORCH) infections

- Birth asphyxia

- Birth trauma

Acquired (secondary) blindness

• Ocular defects

- Vitamin A deficiency

- Infections: Trachoma, keratitis, uveitis*

- Trauma*: Foreign body, sports injuries

- Tumors: Retinoblastoma

- Degenerative: ROP, R. pigmentosa, detachment

- Vascular: Retinal vein occlusion*

• CNS disorders

- Infections: Encephalitis, meningitis

- Head injuries*

- Vascular*: Strokes, migraine, raised ICP

- Tumors: Craniopharyngioma, optic glioma

- Degenerative: Storage disorders, leukodystrophies

• Psychogenic* (Hysteria/conversion reaction)

may lead to acute loss of vision.

ROP: Retinopathy of prematurity

Under the Indian Disability Act 2016, loss of vision is defined as:

Total Blindness with the inability to distinguish darkness from bright light in either eye, or

Low-vision with any of the following criteria:

• Visual acuity not exceeding 6/18 or less than 20/60 up to 3/60 or up to 10/200 (Snellen) in the better eye with best possible corrections.

• Limitation of the field of vision subtending an angle of less than 40 degree up to 10 degree.

26.3.2