First Author: A.Kakehashi JAPAN
Co Author(s): T. Hasegawa
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We report variations in the posterior vitreous structure using swept-source optical coherence tomography (SS-OCT) in normal eyes.
We studied 31 normal eyes (eyes without vitreoretinal diseases or ocular surgery, +6.0 diopters [D] > refractive error > -6.0 D) with no posterior vitreous detachment (PVD) diagnosed by slit-lamp biomicroscopy. All eyes underwent concurrent examinations of the posterior vitreous using SS-OCT (DRI OCT Triton Plus, Topcon, Tokyo, Japan).
Of the 31 eyes, 23 (74%) eyes did not have a shallow PVD and eight (26%) eyes had a shallow PVD, which was undetectable by slit-lamp biomicroscopy. The mean age of the patients without a shallow PVD (mean ± standard deviation [SD], 46.9 ± 11.8 years) was significantly (p<0.001) lower than those with a shallow PVD (69.3 ± 6.3 years). Of the 31 eyes, 17 (54.8%) eyes had an optically empty sheet-like space just in front of a thin posterior vitreous cortex (posterior vitreoschisis) and 14 (45.2%) eyes had no posterior vitreoschisis. The posterior vitreoschisis was undetectable by slit-lamp biomicroscopy similar to Cloquet’s canal. The ages of patients with posterior vitreoschisis (mean ± SD, 45.5 ± 13.5 years) was significantly (p<0.001) lower than those without posterior vitreoschisis (61.4±10.5 years). SS-OCT showed a presumed Bursa premacularis as an unclear, undemarcated oval space with coarse vitreous opacities in front of the posterior vitreoschisis, and slit-lamp biomicroscopy showed liquefaction. Only one eye had an optically empty oval space in front of the posterior vitreoschisis.
Shallow PVDs are undetectable by slit-lamp biomicroscopy and develop with progressive aging. The posterior vitreoschisis seems to correspond to a subbursal space, which Worst referred to using his technique of in vivo slit-lamp microscopy and later as an artifact. Because posterior vitreoschisis and Cloquet’s canal are optically empty spaces at any age, both vitreous pathologies could represent shedding after regression of the primary vitreous. Most Bursa premacularis were observed on SS-OCT images as coarse vitreous opacities in front of the posterior vitreoschisis and also as vitreous liquefaction by slit-lamp biomicroscopy. Thus, the Bursa premacularis seems to be an age-related pathology.