TAILIEUCHUNG - Ebook Basic ophthalmology (4/E): Part 2
(BQ) Part 2 book “Basic ophthalmology” has contents: The vitreous, glaucoma, the retina, the optic nerve, injuries to the eye, the ocular motility and squint (strabismus), the lids, the lacrimal apparatus, the orbit, general therapeutics, the causes and prevention of blindness, ophthalmic instruments. | APPLIED ANATOMY The vitreous is an inert, avascular, transparent, jelly-like structure which serves only optical functions. It consists of a delicate framework of collagen and hyaluronic acid. It is a hydrophilic gel which becomes “fluid” when its protein basis is coagulated due to, • Advancing senile age. • Degenerations, . as in high myopia. • Chemical and mechanical trauma. Attachments 1. It is attached anteriorly to the lens (Hyaloid capsular ligament of Wieger) and ciliary epithelium in front of the ora serrata. The part of the vitreous about 4 mm across the ora serrata is known as the “base of vitreous,” where the attachment is strongest. 2. It is attached posteriorly to the edge of the optic disc and macula lutea (foveal region) forming ring-shaped structure around them. Age Changes in the Vitreous The vitreous undergoes significant physical and biochemical changes with aging. 1. At birth—The Cloquet’s canal runs straight from lens to the optic disc. It contains the primary vitreous. The Vitreous i. ii. iii. iv. v. vi. vii. 247 Diseases of the vitreous Opacities in the vitreous, Vitreous bands and membranes, Persistent hyperplastic vitreous, Vitreous haemorrhage, Vitreous loss, Vitreous inflammation, Vitreous detachment 2. In young persons—The vitreous gel is homogeneous but its fibres become coarse with the process of advancing age. 3. In old age and in high myopes—The secondary vitreous liquefies (syneresis) and shrinks, producing a vitreous detachment, vitreous and retinal haemorrhage and retinal break. Function The vitreous forms one of the refractive media of the eye. The vitreous does not have any blood vessels. It derives nutrition from the surrounding structures like choroid, ciliary body. OPACITIES IN THE VITREOUS Opacities in the vitreous may result in marked visual impairment due to ‘floaters’ or visual loss. Etiology 1. Developmental causes—The opacities are usually located in the Cloquet’s canal and are remnants of the hyaloid .
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