Table 1.
Qualitative questioning about the possible reasons for discordance (prior to questionnaire), divided into total number of twins, number of twins with higher SphE and with lower SphE suggesting possible reasons
| Theory | N (Total) | N (Higher SphE) | N (Lower SphE) | p‐value |
|---|---|---|---|---|
| Close work | 28 | 12 | 16 | 0.45 |
| Job vs raising family before 25 | 26 | 14 | 12 | 0.69 |
| Residence | 23 | 10 | 13 | 0.53 |
| Association with other illnesses/medication (e.g. measles, depression, asthma medication) | 17 | 9 | 8 | 0.81 |
| Heredity | 16 | 6 | 10 | 0.32 |
| Prematurity/lower birth weight | 10 | 5 | 5 | 1 |
| Diet/life style | 10 | 6 | 4 | 0.53 |
| Outdoor exposure/night work and poor light | 9 | 3 | 6 | 0.32 |
| Injury | 5 | 2 | 3 | 0.65 |
| Mirror image twins (theory that phenotypes are opposite for certain traits) | 4 | 3 | 1 | 0.32 |
| Other (contact lenes, hair occluding eyes, birth trauma, eye deformity at birth, pregnancy‐associated myopia, eye exercising, wealth) | 11 | 5 | 6 | 0.76 |