Our survey shows that of Norwegian children registered as visually impaired, 66 % were partly sighted (defined by us as visual acuity 0.33 plus WHO category 1 and 2) and 31 % blind (WHO category 3, 4 or 5). This distribution between partial sightedness and blindness corresponds well with the distribution in the similar Swedish study from the 1990s (12) and in the NORDSYN study (7).
Interesting in itself is the finding that almost a third of the registered children had visual acuity > 0.33, and thus are not visually impaired according to the WHO definition. This may indicate that the special needs service does not focus solely on visual acuity as a referral criterion, but considers the patient’s overall situation. If this is the case, we regard this as a good assessment, as we know that a number of children with multiple disabilities have visual problems that may not necessarily affect their visual acuity, but tend more to affect their visuocognitive functions. Our data are not detailed enough to show with any certainty whether this is the reason for the large number of children with visual acuity > 0.33.
There is a preponderance of boys in most studies of visual impairment in children, as was also the case for our dataset. In the NORDSYN study, a boy/girl ratio of 1.39 was found (7). In our study this ratio was 346/282 = 1.22, in practice the same as the ratio of 1.20 in Blohmé and Tornqvist’s study from Sweden (12).
Two main findings emerge from our study. One is that neuro-ophthalmological diseases, particularly cerebral visual impairment, are the predominant diagnoses. Similar findings were made by the NORDSYN group (9) and Blohmé and Tornqvist in Sweden (14). Aetiologically, this is a heterogeneous group – some have known brain damage from the perinatal period (including birth asphyxia and prematurity), while others have genetic conditions.
There are recently published studies in which whole genome sequencing has been able to verify the genetic cause in a large percentage of children with cerebral visual impairment and cognitive impairments (16). These are diagnostics that are increasingly used in ordinary clinical assessments and which may be able to provide a specific diagnosis for more of these children in the future.
The second main finding is that more than half of the visually impaired children had additional impairments, particularly motor (cerebral palsy) and cognitive impairments. This finding corresponds well with the Swedish study, in which 60 % of all children with visual impairment had additional disabilities (13). The highest prevalence of additional impairments (85 %) was found in the group with neuro-ophthalmological diseases, which is consistent with the findings of the Swedish study (88 %) (14).
This means that the ophthalmic health service for visually impaired children in many cases has to be a cross-disciplinary collaboration involving paediatricians, special needs teachers for the visually impaired, psychologists, neuropsychologists, physiotherapists and social workers. Close cooperation with patient associations and the Norwegian Association of the Blind and Partially Sighted is also crucial to an optimal result.
A special group that it is important to be aware of consists of those who have both visual and hearing impairment. Deafblindness is defined as a separate specialist area in the Statped system, and covers all those who have combined visual and hearing impairment. In our dataset there were 46 such patients (7.3 %).
Our study has some manifest weaknesses. For various reasons, the logistics of sending out the invitations to participate, the reminder letters, the receipt of statements of consent, and the organisation and collection of the data turned out to be far more time-consuming than initially assumed, and hence the study has extended over a period of very many years. Similarly, the analysis of the database with quality assurance of the data has taken considerably more time than expected.
Because we had to recruit patients to this study via the special needs education service, and because we were dependent on written consent, the patient data in the study are incomplete and may be selective. This means that the data must be interpreted with caution in an epidemiological context. The medical data available are of variable quality. Nonetheless, the material provides a picture of the group of children with visual impairment who are being monitored in the special needs education system for the visually impaired.
The similarities between our data, the NORDSYN study and Blohmé and Tornqvist’s data indicate that the distribution among the various diagnostic groups and the distribution between partial sightedness and blindness are roughly the same in Norway as in the other Nordic countries.
If we assume that the Swedish age-specific prevalence data from the 1990s (12) are correct, we should have about 1 450 blind and partially sighted children and adolescents here in Norway. A recent study from the UK indicates that while the percentage of adults with visual impairment is declining, the percentage of children with such disabilities is rising (17). It is assumed that there are various reasons for this, but that the increased survival of small prematures and increasing immigration are two contributory factors. Because we do not have a Norwegian register, we do not know whether there is a similar trend in Norway.
We found during our registration work that the archived medical information in the special needs education register cannot function as a complete register for ophthalmological data, nor can this be expected. Subsequent to the conclusion of the data collection in this research project, the special needs education service for the visually impaired has also been reorganized, as mentioned initially.
The Statped system is now required to deal with the municipal authorities and not the specialist health service. This presents a regrettable bureaucratic obstacle to the important cooperation between ophthalmologists and special needs educators, which makes it even more necessary to establish a special ophthalmological register for children and adolescents with visual impairment.