Table 4 Main anatomical site of abnormality, and underlying aetiology in 1935 severely visually impaired and blind children, by age of onset of disorder.
| Congenital | Infantile* | ⩾1 to <5 years | ⩾5 to <16 years | |
|---|---|---|---|---|
| n (%) | n (%) | n (%) | n (%) | |
| Anatomical p<0.001† | ||||
| Whole globe | 199 (78.7) | 14 (5.5) | 26 (10.3) | 14(5.5) |
| Cornea | 38 (7.4) | 82 (16.0) | 281 (54.7) | 113 (22.0) |
| Lens | 189 (30.1) | 230 (36.6) | 152 (24.2) | 58 (9.2) |
| Uvea | 15 (39.5) | 2 (5.3) | 5 (13.2) | 16 (42.1) |
| Retina | 105 (42.9) | 39 (15.9) | 59 (24.1) | 42 (17.1) |
| Optic nerve | 23 (14.9) | 25 (16.2) | 51 (33.1) | 55 (35.7) |
| Glaucoma | 37 (44.6) | 19 (22.9) | 14 (16.9) | 13 (15.7) |
| Other‡ | 6 (31.6) | 3 (15.8) | 4 (21.1) | 6 (31.6) |
| Aetiology p<0.001† | ||||
| Hereditary | 156 (53.6) | 52 (17.9) | 55 (18.9) | 28 (9.6) |
| Childhood factor | 20 (3.4) | 103 (17.4) | 319 (53.8) | 151 (25.5) |
| Other§ | 12 (70.6) | 2 (11.8) | 2 (11.8) | 1 (5.9) |
| Unknown | 424 (41.0) | 257 (24.9) | 216 (20.9) | 137 (13.3) |
| Type of blindness p<0.001† | ||||
| Preventable | 14 (2.6) | 84 (15.6) | 305 (56.8) | 134 (25.0) |
| Treatable | 246 (30.7) | 259 (32.3) | 183 (22.9) | 113 (14.1) |
| Unavoidable | 352 (59.0) | 71 (11.9) | 104 (17.4) | 70 (11.7) |
| Total | 612 (31.6) | 414 (21.4) | 592 (30.6) | 317 (16.4) |
*Postnatal to <1 year.
†χ2, showing significant differences in anatomical, aetiological and type of blindness by age of onset of disorder.
‡Includes children that had either no anatomical abnormality (n = 14) or no anterior segment abnormality, but the posterior segment was not examined (n = 5) because the child was too young and/or uncooperative and/or had multiple disabilities.
§Perinatal, intrauterine.