Download P4.27 Investigation into the relationship between

P4.27
Investigation into the relationship between anterior segment anatomy, corneal biomechanics
and refractive error in 10-12 year old school boys
A. Shah1, S. Low2, P.S. Lee2, E. White3, P. Foster2, D. Garway-Heath4, K. Barton5
1
Moorfields Eye Hospital and UCL Institute of Ophthalmology, London, UK; 2Moorfields Eye
Hospital and Division of Epidemiology & Genetics, UCL Institute of Ophthalmology, London, UK;
3
Glaucoma Research Unit, Moorfields Eye Hospital, London, UK; 4Moorfields Eye Hospital, UCL
Institute of Ophthalmology and Department of Optometry, City University, London, UK;
5
Moorfields Eye Hospital, London, UK
Purpose: Myopia is associated with anatomical changes in the anterior as well as the posterior
segment of the eye. Relatively little is known about the time course and incidence of the anterior
segment changes and there are no documented studies. Anterior segment optical coherence
tomography (AS-OCT) is a rapid non-invasive imaging modality that can be used to assess iris
profile in this age group. Iris concavity has been implicated in the pathogenesis of pigment
dispersion syndrome (PDS) but there is evidence to suggest that it may also be found in normal
subjects, more commonly in younger, myopic individuals. There are conflicting data on the
relationship between corneal biomechanics and components of refractive error in school age
children. The purpose of this study was to explore the relationship between iris concavity and
components of refractive error. The relationship between corneal biomechanics and components of
refractive error was also explored.
Methods: A cohort of 10-12 year old boys (n = 96) were recruited from a local school. AS-OCT
imaging was performed using both near and distance fixation targets. Iris profile was quantified
using Visante 3.0 software. A negative value indicated concavity, a positive value convexity.
Corneal hysteresis (CH) and corneal response factor (CRF) were measured using the Ocular
Response Analyser (ORA). ORA measurements with a waveform score ≥ 4 were included for
analysis. LogMAR visual acuity, focimetry, autorefraction and axial biometry were also performed.
Results: The mean age (± SD) of the cohort was 11.5 (± 0.5) (range 10.5 to 12.3) years. The
prevalence of iris concavity at distance fixation was 26% and at near fixation was 65%. Mean (±
SD) spherical equivalent (SE) and axial length (AL) were -0.37 (± 1.72) dioptres and 23.93 (± 0.95)
mm. Significant correlations were found between SE and iris concavity at distance fixation
(Spearman correlation coefficient [r] = 0.36, p = 0.0004) and between AL and iris concavity at near
fixation (Pearson correlation coefficient [r] = -0.22, p = 0.04). 79 subjects had at least 1 set of ORA
measurements meeting the quality criterion. Mean (± SD) CH, CRF and corneal-compensated IOP
were 11.8 (± 1.7), 11.9 (± 1.8) and 15.5 (± 4.3) mmHg. No significant correlations were found
between CH or CRF and SE or AL.
Conclusion: Iris concavity is a common finding in our cohort and the degree of concavity is related
to refractive error. Further work is required to clarify if anatomical differences exist between the
type of iris concavity seen in the adolescent eye, and that found in adults with PDS.