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Ocular biometric correlates of ciliary muscle thickness in human myopia
Author(s) -
Buckhurst Hetal,
Gilmartin Bernard,
Cubbidge Robert P,
Nagra Manbir,
Logan Nicola S
Publication year - 2013
Publication title -
ophthalmic and physiological optics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.147
H-Index - 66
eISSN - 1475-1313
pISSN - 0275-5408
DOI - 10.1111/opo.12039
Subject(s) - refractive error , ciliary muscle , ophthalmology , anatomy , medicine , optometry , mathematics , eye disease , optics , physics , accommodation
Purpose Anterior segment optical coherent tomography ( AS ‐ OCT ) is used to further examine previous reports that ciliary muscle thickness ( CMT ) is increased in myopic eyes. With reference to temporal and nasal CMT , interrelationships between biometric and morphological characteristics of anterior and posterior segments are analysed for B ritish‐ W hite and B ritish‐ S outh‐ A sian adults with and without myopia. Methods Data are presented for the right eyes of 62 subjects ( B ritish‐ W hite n = 39, B ritish‐ S outh‐ A sian n = 23, aged 18–40 years) with a range of refractive error (mean spherical error ( MSE (D)) −1.74 ± 3.26; range −10.06 to +4.38) and separated into myopes ( MSE (D) <−0.50, range −10.06 to −0.56; n = 30) and non‐myopes ( MSE (D) ≥−0.50, −0.50 to +4.38; n = 32). Temporal and nasal ciliary muscle cross‐sections were imaged using a Visante AS ‐ OCT . Using Visante software, manual measures of nasal and temporal CMT ( NCMT and TCMT respectively) were taken in successive posterior 1 mm steps from the scleral spur over a 3 mm distance (designated NCMT 1, TCMT 1 et seq ). Measures of axial length and anterior chamber depth were taken with an IOLM aster biometer. MSE and corneal curvature ( CC ) measurements were taken with a S hin‐ N ippon auto‐refractor. Magnetic resonance imaging was used to determine total ocular volume ( OV ) for 31 of the original subject group. Statistical comparisons and analyses were made using mixed repeated measures anova s, P earson's correlation coefficient and stepwise forward multiple linear regression. Results MSE was significantly associated with CMT , with thicker CMT 2 and CMT 3 being found in the myopic eyes ( p = 0.002). In non‐myopic eyes TCMT 1, TCMT 2, NCMT 1 and NCMT 2 correlated significantly with MSE , AL and OV ( p < 0.05). In contrast, myopic eyes failed generally to exhibit a significant correlation between CMT , MSE and axial length but notably retained a significant correlation between OV , TCMT 2, TCMT 3, NCMT 2 and NCMT 3 ( p < 0.05). OV was found to be a significantly better predictor of TCMT 2 and TCMT 3 than AL by approximately a factor of two ( p < 0.001). Anterior chamber depth was significantly associated with both temporal and nasal CMT 2 and CMT 3; TCMT 1 correlated positively with CC . Ethnicity had no significant effect on differences in CMT . Conclusions Increased CMT is associated with myopia. We speculate that the lack of correlation in myopic subjects between CMT and axial length, but not between CMT and OV , is evidence that disrupted feedback between the fovea and ciliary apparatus occurs in myopia development.