Childhood Visual Impairment in New Zealand: Identifying, Assessing, Treating

Abstract

Paediatric visual impairment and blindness has emotional, social and economic impacts for the individual, their family, and the wider community. Causes of visual impairment in children are multifarious and include prematurity, structural abnormalities, inherited conditions, infective diseases, and nutritional deficiencies. A large number of paediatric ocular conditions are avoidable, being either preventable or treatable. Thus, early detection through screening programs and accurate assessment is essential to improve long term outcomes for children through timely management and treatment. Retinopathy of prematurity (ROP) is a disease that affects low birth weight and extremely premature infants. Screening to detect ROP which requires treatment is recommended for all at-risk infants by the World Health Organization. However, worldwide the numbers of infants at-risk of ROP is increasing and the number of ophthalmologists willing to screen is decreasing. The development of wide-field digital imaging (WFDI) as a potential alternative for ROP screening may alleviate the current workflow challenge. The Auckland Regional Telemedicine ROP network (ART-ROP) is one of the first programs worldwide to exclusively use WFDI to detect and manage ROP. A large review of all infants screened by ART-ROP between 2006 and 2015 was undertaken revealing no infant with treatment-requiring ROP was missed by this screening method. A cohort of these children were prospectively recruited to further assess the efficacy of ART-ROP by evaluating long term ophthalmic structural and visual outcomes of children who were previously screened for ROP in our telemedicine system. No new cases of ROPrelated retinal changes were detected indicating the safety and reliability of ART-ROP screening. Of note, no visual difference was noted between premature children with and without a history of ROP. With the efficacy of WFDI established in premature infants, the potential of it being used as a screening method for all infants was investigated. Universal newborn eye screening (UNES) utilised WFDI of the anterior and posterior eye to detect the prevalence of congenital ocular abnormalities including birthrelated retinal haemorrhages in a prospective cohort of newborns. Importantly, ocular abnormalities were detected in a significant number of infants. Retinal haemorrhages were the most common with 94% of these resolved by six-week follow up examination. However, the impact of retinal haemorrhages, in particular those that are long-standing or that affect the macula, are unknown. Other key observations included congenital cataract, optic nerve hypoplasia, and other retinal lesions, indicating that UNES with WFDI is a successful screening tool for detecting congenital ocular abnormalities. A paediatric visual field screening technique called the Saccadic Vector Optokinetic Perimeter (SVOP) has been recently developed for young children or those with neuro-disabilities. SVOP utilises infra-red eye tracking to potentially overcome some of the challenges with current paediatric visual field techniques such as Goldmann perimetry or the confrontation method. The clinical applicability of SVOP was evaluated in children with both normal and impaired vision. The majority of children were able to complete SVOP, with good agreement observed between SVOP, Goldmann, and the confrontation visual field method in children with normal vision. SVOP was also significantly faster to perform. Therefore, SVOP is a potential screening tool for visual fields in children who are unable to perform standard techniques due to neuro-disabilities, complex needs, or mobility issues. The field of paediatric visual impairment is extensive but extremely important. The inter-related research studies contained within this PhD thesis aim to improve screening and assessment techniques of newborns, both premature and full-term, and children. Improvements and novel developments in these areas, as identified in this thesis, may help to eliminate the significant burden of avoidable visual impairment in the paediatric population.