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C.J. Abbott, M.J. Pianta, U. Grunert, N.A. McBrien; Retinal Thinning in High Myopia – A Comparison of Optical Coherence Tomography and Histology . Invest. Ophthalmol. Vis. Sci. 2006;47(13):1144.
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© ARVO (1962-2015); The Authors (2016-present)
To establish whether optical coherence tomography (OCT) is able to detect retinal thinning in highly myopic tree shrew eyes and to determine whether the amount of thinning detected with OCT correlates with the amount of thinning detected using a histological method.
Two adult tree shrews had high myopia induced in one eye using lid–suture while the other eye acted as a control. After 18 months of myopia induction retinal thinning was assessed as follows. The Zeiss STRATUS OCT system was used to scan the retina over an area of ∼4 mm2 centred on the optic disc, using a raster pattern of 2 mm long horizontal scans separated vertically by 0.17 mm. A–scan ultrasonography, keratometry and retinoscopy were then performed. The retinas were immersion fixed with 2.5% glutaraldehyde and 1% paraformaldehyde in phosphate buffer. Retinal thickness measurements were obtained using the OCT reflectivity profiles and vertical histology sections for corresponding retinal locations. Myopic retinal thinning was expressed as a percentage reduction in thickness relative to control: (1–(treated/control)) x 100%.
Both treated eyes developed a high degree of axial myopia, with a relative myopia of –18.4 D (treated – control) for tree shrew 1 and –13.2 D for tree shrew 2. The vitreous chamber depth elongation was 0.84 mm (treated – control) and 0.49 mm respectively. The average myopic retinal thinning (mean ± SD) in the inferior–temporal quadrant of tree shrew 1 was 10.64% ± 5.02 measured by OCT and 17.92% ± 3.36 measured in histological sections (n = 3 locations). Similarly, the average myopic retinal thinning in the superior hemi–field of tree shrew 2 was 9.02% ± 3.41 by OCT and 21.30% ± 4.35 by histology (n = 11 locations).
The results show that OCT is able to detect retinal thinning in highly myopic tree shrews. Thinning obtained using in vivo measures (OCT) was less than the thinning obtained using in vitro measures (histology). These findings have positive implications for the use of OCT as an early detection method of retinal thinning in myopic humans.
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