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Monica Jong, Padmaja Sankaridurg, Serge Resnikoff, Wayne Li, Kovin Shunmugam Naidoo, Mingguang He; Vision impairment in highly myopic eyes without ocular pathology: the ZOC-BHVI High Myopia Study. Invest. Ophthalmol. Vis. Sci. 2016;57(12):2470. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To investigate the association of refractive error and axial length with vision impairment in in highly myopic eyes without ocular pathology.
Six hundred and forty six individuals without ocular pathology were enrolled in the ongoing ZOC-BHVI high myopia study at the Zhongshan Ophthalmic Centre, Guangzhou, China. Participants aged 7 to 63 with myopia of -6.00D or worse (both eyes) underwent a full eye examination. Both eyes were considered. Baseline measurements taken were: visual acuities (VA), autorefraction (mostly cycloplegic) and axial length (AL). Eyes were categorised according to best corrected spectacle VA as: no vision impairment (VI) (≥ 20/20); mild VI (<20/20 to ≥20/60); moderate VI(<20/60 to ≥20/200); severe VI (<20/200 to ≥20/400); and blindness (<20/400). The percentage of eyes in each category were calculated as a function of age, spherical equivalent refractive error (SEQ), and AL. Multiple linear regression was used to test for significance (p<0.05).
The mean age of the group was 20.0 ± 9.3 years and 52% were female. The mean SEQ was -8.7 ± 2.9D (range -6.00 to -40.00D) and mean AL was 27.2 ± 1.4mm (range 23 to 32mm). With respect to VA, 63.3% (n = 818) had no VI, 35.1% (n = 454) had mild VI, 1.2% (n=16) had moderate VI and 0.3% (n=4) had severe VI. There were no cases of blindness. Percent of eyes with mild VI increased with increasing SEQ and was: 14.1% for -6.00< SEQ ≤-7.00 D; 22.8% for -7.00 D< SEQ ≤-8.00 D; and 84.3% -15.00 D< SEQ ≤-40.00 D. A small percentage of eyes experienced moderate VI at SEQ ≤-10.00 D and severe VI at ≤-12.00 D. Similar to that seen with increasing SEQ, percentage of eyes with mild VI increased with increasing AL: 27.5% for 23 mm≤ AL < 26 mm; 24.9% for AL 26 mm≤ AL <27 mm and increasing to 77.4% for 30 mm≤ AL <32 mm. The greatest occurrence of mild VI was seen in those ≤20 years (23.4%). Vision impairment was significantly associated with the SEQ (p <0.0001) and AL (p <0.0001) but not associated with age (p=0.89).
In this group of high myopeswith no obvious retinal pathology, a significant percentage of eyes had mild VI especially at high levels of SEQ and longer AL. The reasons for the VI are unknown and remain to be explored, possible reasons include one or both: a) minification with spectacle lenses and, b) high myopia associated with retinal stretching leading to increased spacing between cone cells.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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