A study recently published in the British Journal of Ophthalmology evaluated the prevalence and associated factors of strabismus and nystagmus in preterm and full-term infants in adulthood.
Give me some background.
Preterm delivery and postnatal retinopathy of prematurity (ROP) are associated with an increased risk of strabismus and nystagmus in infancy and childhood.
Consequently, as survival rates of extremely preterm babies increase, more infants face a higher risk of eye conditions like strabismus and nystagmus in childhood and adolescence—impacting their quality of vision.
However, there are limited studies on the long-term effects of prematurity and associated factors on strabismus prevalence in adulthood—motivating a research team from Johannes Gutenberg University Mainz in Mainz, Germany to elucidate a potential relationship.
Now talk about the study.
Investigators analyzed data from the Gutenberg Prematurity Eye Study—a retrospective cohort study that recorded findings from ophthalmic examinations of participants born preterm and full-term (aged 18-52 years).
Perinatal data was assessed for risk factors alongside data from comprehensive ophthalmological examinations.
The associations between perinatal and exam data, strabismus, and nystagmus were evaluated by analyzing 16 different perinatal and actual risk factors in multivariable analysis.
How were participants organized?
Study participants were categorized into six groups:
- Full-term controls (gestational age [GA] at birth ≥37 weeks)
- Preterm without ROP and GA 33-36 weeks
- GA 29-32 weeks
- GA ≤28 weeks
- Non-treated ROP
- Treated ROP
Findings?
Overall, 892 eyes of 450 preterm and full-term individuals (251 females, mean age: 28.6 years, standard deviation [SD] ±8.6 years) were included in the study.
Esotropia was more frequent than exotropia and hypermetropia/hypometropia, and the research team noted that most strabismus cases occurred within the first 10 years of life.
What was the prevalence of strabismus and nystagmus?
The prevalence of strabismus was:
- Full-term controls: 2.1% (3/140)
- Preterm without ROP: 6.6% (9/137)
- GA 29-32 weeks: 17.4% (16/92)
- GA ≤28 weeks: 11.1% (2/18)
- Non-treated ROP: 27.1% (13/48)
- Treated ROP: 60% (9/15)
The prevalence of nystagmus was:
- Full-term controls: 0.7% (1/140)
- Preterm without ROP: 1.5% (2/137)
- GA 29-32 weeks: 4.3% (4/92)
- GA ≤28 weeks: 5.6% (1/18)
- Non-treated ROP: 10.4% (5/48)
- Treated ROP: 26.7% (4/15)
And potential risk factors for strabismus and nystagmus?
Using multivariable analysis, researchers determined that strabismus was associated with:
- GA (odds ratio [OR]=0.90, p=0.046)
- Anisometropia ≥1.5 diopters (OR=3.87, p=0.003)
- Hypermetropia ≥2 diopters (OR=9.89, p<0.001)
- Astigmatism ≥1.5 diopters (OR=2.73, p=0.017)
The strongest predictor associated with nystagmus was perinatal adverse events (OR=15.8, p=0.002).
Limitations?
The single-center design and predominantly Caucasian cohort were limitations to the study that may have impacted the generalizability of the findings.
Additionally, the low number of participants with advanced ROP stages and ROP requiring treatment may have led to lower statistical power and less precise estimates in these groups.
Expert opinion:
According to the study author: “Strabismus occurs in affected individuals, particularly in premature-born subjects within the first years of life, highlighting the need to evaluate whether screening in this high-risk population for amblyopia should be recommended.”
Take home.
These findings suggest that low GA and refraction of the eye (i.e., anisometropia, hypermetropia, astigmatism) were independent risk factors for strabismus, which typically occurs in the first 10 years of life.
Perinatal adverse events were the most important factors for the presence of nystagmus in adulthood.