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Joshua Zubin Warren, Anisha Arora, Brian P Higgins, Erin Curran, Joseph Carroll; Examining axial length in congenital achromatopsia. Invest. Ophthalmol. Vis. Sci. 2018;59(9):2156.
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© ARVO (1962-2015); The Authors (2016-present)
Normal emmetropization matches the eye’s optical power with its axial length, bringing images into focus on the photoreceptor layer. Thus, photoreceptors may be involved in this process. In congenital achromatopsia (ACHM), cone function is absent from birth, so examining ocular biometry in these patients may provide insight into the role of cone function in emmetropization. Here we examined axial length in a large cohort of ACHM subjects.
Cross-sectional data from 93 subjects with genetically-confirmed ACHM were included in this study (49F, 44M; age: range = 5-66 yrs, mean ± SD = 27.7 ± 16.2 yrs). Axial length was measured using an IOL Master (Carl Zeiss Meditec, Dublin, CA). For comparison, we collated axial length data from 702 control subjects (366F, 336M; age: range = 7-85 yrs, mean ± SD age = 34.5±16.8 yrs); some of which was published in prior studies from the Advanced Ocular Imaging Program.[1,2] Differences between groups were assessed using Mann-Whitney analyses.
Axial length (mean ± SD) was 23.56 ± 1.99 mm across all ACHM subjects. This was significantly shorter than the normal controls (24.23 ± 1.27 mm, p<0.0001). However, axial length is known to be shorter in females, which was confirmed in our control population (male = 24.51 ± 1.32 mm; female = 23.97 ± 1.16 mm; p<0.0001). As we also noted that the control population was significantly older than our ACHM group (p=0.0001), a within-gender analysis was performed on subjects over 18 years. For the females over 18 years, the ACHM group still had shorter eyes (23.47 ± 2.09 mm vs 24.00 ± 1.18 mm; p=0.0039). For the males over 18 years, we observed no significant difference in axial length (ACHM = 24.27 ± 1.68 mm; normal = 24.56 ± 1.35 mm; p=0.32).
Our findings of shorter axial lengths in ACHM are consistent with reports of frequent hyperopia in these patients. However, the analysis in subjects over 18 years suggests this may be due in part to the early age at which ACHM patients present in the clinic, when the eye is not fully grown. We encourage reporting axial length in these subjects where possible to provide more data to examine this question. In addition, longitudinal studies are needed to determine whether emmetropization is altered in ACHM. PMID: 20149815 PMID: 28616362
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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