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THE VITREOUS
Abdelmonem Hamed, M.D.Professor of OphthalmologyBenha College of MedicineFellow of Baylor College of Medicine, USA
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.
Wight: 4gmVolume: 4ml
Attachments: It is attached
anteriorly to the lens and ciliary epithelium.
It is known as the "vitreous base".
Attachments: It is attached posteriorly to the edge
of the optic disc and macula lutea.
Function: The vitreous forms one of the
refractive media of the eye. (RI 1.33)
RI of H2o = 1.369 RI of air = 1 .00 RI=Measure of the
refraction of a beam of light on entering a denser medium Nutrition :
It derives nutrition from the surrounding structures like choroids, ciliary body.
OPACITIES IN THE VITROUS
Etiology: Development causes: The
opacities are usually located in the Cloquet's canal.
Degenerative causes.
OPACITIES IN THE VITROUS
Vitreous: is optically clear
structure Pseudo membranes
and pseudo fibers appearing as moving folds (Vit. floaters, or Muscae volitantes)
Weiss’ ring
Asteroid hyalosis:
Spherical, white bodies of calcium soaps resembling snowball.
It is asymptomatic therefore no treatment is required.
A pars plana vitrectomy may be considered if vision is markedly reduced.
Synchysis scintillans:
deposition of highly refractive cholesterol crystals in the vitreous.
Golden shower is seen during the movements of the eye.
No treatment is indicated.
Other causes of vit. opacities: High myopia. Retrolental fibroplasia. Wagner's disease. Ehlers- Danlos syndrome Marfan's syndrome Chronic cyclitis. Diabetes and Eale's disease Neoplasm. Amyliodosis
Q: Can vitreous
degeneration be treated?A: Molecular bonds of the clear vitreous cannot be restored after vitreous
collapse = no medical ttt
VITAMINS
Antioxidants may retard the denaturation of protein
Treatment of vitreous opacitiec1. YAG laser2. Vitrectomy
NEODYMIUM-YAG LASER infrared spectrum focused beam energy 4 - 6 milli
joules 200 - 600 shots total 1 - 3 treatments Photodisruption
LASER SURGERY
COMPLICATIONS
elevated intraocular pressure chroidal micro hemorhage retinal detachment cataract
VITREOUS BANDS AND MEMBRANES
They consist of hyalocytes, fibrocytes and endothelial cells of the capillaries.
They cause oedema, haemorrhage and hole formation in the retina. Why?
This is may be followed by RD. TTT: PP vitrectomy.
PERSISTENT HYPERPLASTIC PRIMARY VITREOUS
Etiology: failure of primary vitreous
structure to regress after birth.
Symptoms: White reflex is seen in the
papillary area. it may be associated
cataract, glaucoma, microphthalmos, intraocular haemorrhage.
PERSISTENT HYPERPLASTIC PRIMARY VITREOUS
Diagnosis: It is diagnosed by
CT. Treatment: Lensectomy and
vitrectomy
VIREOUS HAEMORRHAGE
Types:There are two types of vitreous haemorrhage:
1. Preretinal or subhyaloid haemorrhage: 1. The haemorrhage occurs between the retina and
the vitreous. 2. The blood remains fluid, red in colour and moves
with gravity . 2. IntraVitreal haemorrhage: The
haemorrhage may get absorbed or degenerate to form a white fibrous tissue mass.
Intravitreal haemorrhage
subhyaloid haemorrhage
Etiology:
1. Trauma 2. Vitreous traction.3. Diabetes mellitus.4. Central retinal vein thrombosis.5. Eale's disease: It is due to retinal
vasculitis and periphlebitis. 6. Malignant hypertension7. Blood diseases: Leukemia, sickle cell
anaemia, etc.
Symptoms:
1. Black spots or cloud may be seen in front of the eye.
2. There is impaired vision. It may be reduced to perception of light.
Signs:
1. Fundus examination:i. No red reflex is seen. ii. Grey opacities may be present in the vitreous.
2. Slit-lamp examination: Fresh blood or clotted blood may be seen in the vitreous.
Complications:
1. Complicated cataract may occur. 2. Retinal atrophy may be present due
to haemosiderosis.3. Retinal detachment may occur due
to organized fibrous tissue bands…..TRACTION
Treatment:
1. Bed-rest with elevation of head. 2. Photocoagulation: It is done if new
vessels or retinal tears are seen. 3. Vitrectomy: It is done after 3 months
if no visual improvement
VITREOUS LOSS
Definition: Herniation of vitreous
only in the anterior chamber or outside the eye.
Etiology:Accidental vitreous loss may occur during surgery on the lens, cornea and iris.
Signs:
1. Corneal oedema due to endothelium touch.
2. Updrawn pupil due to attachment of vitreous between the papillary margin and wound.
3. Macular oedema. 4. Aphakic glaucoma
due to papillary block.
Treatment:
Anterior vitrectomy By vitrectomy machine, or By vitreous scissors is performed
through a large corneal section .
VITREOUS INFLAMMATION
Vitreous is an excellent culture medium for the growth of bacteria and fungus leading to endophthalmitis and vitreous abscess formation.
Signs of endophthalmitis
The presence of WBCs lead to formation of fibrous connective tissue >>>>>>retinal detachment due to contraction.
TTT: Medical IO injection Vitrectomy
VITRECTOMY
Excision and replacement of the vitreous is known as vitrectomy.
Indications for vitrectomy:
1. Persistent vitreous opacity. i. Haemorrhage.ii. Vitreous membrane and bands.iii. Preretinal membranes.
Indications for vitrectomy:
2. Complications of cataract extraction:i. Loss of vitreous. ii. Vitreous touch with bullous keratopathy.iii. Incarceration of vitreous in wound.iv. Malignant glaucoma.v. Removal of intraocular lens or nucleus from the vitreous cavity.
3. Endophthalmitis with vitreous abscess.
Indications for vitrectomy:
4. Trauma:i. Intraocular foreign body. ii. Subluxated or dislocated lens.
5. Complicated retinal detachmenti. Vitreous traction by fibrovascular bands.ii. Gaint retinal tear. iii. Retinal dialysis.
6. Congenital cataract (lensectomy).7. Persistent hyperplastic primary
vitreous.
TYPES OF VITRECTOMY
Anterior vitrectomy PP vitrectomy 3.5mm from
limbus = pars plana
VITREOUS SUBSTITUTES
Liquid: Normal saline, BSS (balanced salt solution), silicone oil, sodium hyaluronate (Healon). Perfluorocarbon liquids (PFCL), etc.
VITREOUS SUBSTITUTES
Gas:a. Air.b. Sulfur hexafluoride (SF6).c. Perfluoro-propane (C3F8) d. Octa-fluoro-cyclo-butane (C4F8).
