- MedOne Ophthalmology
- ChapterSource: Freitag S, Lefebvre D, Lee N et al., ed. Eyelid Reconstruction. 1st Edition. Thieme; 2020. doi:10.1055/b-006-160141Comment: The main function of the eyelid is to protect the eye. The eyelids attach to orbital bones via the medial canthal tendon (MCT) and lateral canthal tendon (LCT) forming two opposite arches. The lateral canthus is usually approximately 2 mm higher than the medial canthus. The horizontal length of the eyelid is about 30 mm and the vertical aperture height (palpebral fissure) is about 10 mm. The adult upper eyelid rests about 1.5 mm below the superior limbus of the cornea, while the lower eyelid rests at the level of the inferior limbus. The peak of the upper eyelid is at the medial border of the pupil, and the lowest point of the lower eyelid margin is the lateral aspect of the pupil. The eyelid margin can be conceptually divided into anterior (skin and orbicularis muscle) and posterior (tarsus and conjunctiva) lamellae for the purposes of eyelid reconstruction.
- ChapterSource: Ehlers J, ed. The Retina Illustrated. 1st Edition. Thieme; 2019. doi:10.1055/b-006-161169Comment: Posterior vitreous detachment (PVD) is the dehiscence of the posterior vitreous cortex from the retina, usually in patients aged 50 and over, as a result of the weakening of the vitreoretinal adhesion in conjunction with vitreous liquefaction (synchysis senilis). PVD typically begins in the perifoveal macula and extends slowly over months or years until complete vitreous separation occurs. PVD manifestations are usually benign, but in some cases vitreous liquefaction occurs without concurrent weakening of vitreoretinal adherence, which may induce numerous pathologic events at the vitreoretinal interface. The most known PVD complications usually occur in the retinal periphery, following the complete PVD, such as retinal tear and rhegmatogenous retinal detachment. Visual symptoms related to PVD include floaters and photopsias, which tend to improve over time. The conventional method for diagnosing PVD is slit-lamp biomicroscopy or indirect ophthalmoscopy by the presence of Weiss ring attached to the posterior hyaloid membrane. Ultrasonography and optical coherence tomography may also have value. No active treatment is usually needed; however, in cases of PVD complications, laser or pars plana vitrectomy surgery may be required.
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