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Factors affecting pupil size after dilatation: the Twin Eye Study
C J Hammond1, H Snieder, T D Spector
1Twin Research and Genetic Epidemiology Unit, St Thomas's Hospital, London SE1 7EH, UK. ch@twin-research.ac.uk
The British Journal of Ophthalmology
|September 27, 2000
Summary
Pupil size after eye dilation is primarily determined by genetics, with heritability up to 80%. Environmental factors play a smaller role, while age, iris color, and refractive error have minimal impact.
Area of Science:
- Ophthalmology
- Human Genetics
- Twin Studies
Background:
- Pupil dilation is crucial for successful eye surgery.
- Understanding the genetic and environmental influences on pupil size is important.
Purpose of the Study:
- To determine the relative importance of genes versus environment on pupil size after mydriasis.
- To investigate the impact of age, iris color, and refractive error on pupil size.
Main Methods:
- A classic twin study involving 506 twin pairs (226 monozygotic, 280 dizygotic) aged 49-79.
- Pupil size was measured using digital retroillumination images after pharmacologic mydriasis.
- Univariate maximum likelihood models were used to estimate genetic and environmental variance.
Main Results:
- Higher correlation of dilated pupil size in monozygotic (MZ) twins (0.82) compared to dizygotic (DZ) twins (0.39).
- Heritability estimates for pupil size ranged from 78-80%, indicating strong genetic determination.
- Individual environmental factors accounted for 18-19% of the variance; age, iris color, and refractive error had minimal contributions.
Conclusions:
- Dilated pupil size is predominantly genetically determined, with heritability up to 80%.
- Genetic factors significantly influence pupil size variability, impacting ophthalmic procedures.