VITREOUS OPACITIES

Since vitreous is a transparent structure, any relatively
non-transparent structure present in it will form an
opacity and cause symptoms of floaters. Common
conditions associated with vitreous opacities are
described below.
Muscae volitantes. These are physiological opacities
and represent the residues of primitive hyaloid
vasculature. Patient perceives them as fine dots and
filaments, which often drift in and out of the visual
field, against a bright background (e.g., clear blue
sky).
Persistent hyperplastic primary vitreous (PHPV)
results from failure of the primary vitreous structure
to regress combined with the hypoplasia of the
posterior portion of vascular meshwork.
Clinically it is characterized by a white pupillary reflex
(leucocoria) seen shortly after birth. Associated
anomalies include congenital cataract, glaucoma, long
and extended ciliary processes, microphthalmos and
vitreous haemorrhage.
Differential diagnosis needs to be made from other
causes of leucocoria especially retinoblastoma,
congenital cataract and retinopathy of prematurity.
Computerised tomography (CT) scanning helps in
diagnosis.
Treatment consists of pars plana lensectomy and
excision of the membranes with anterior vitrectomy
provided the diagnosis is made early. Visual prognosis
is often poor.
Inflammatory vitreous opacities. These consist of
exudates poured into the vitreous in patients with
anterior uveitis (iridocyclitis), posterior uveitis
(choroiditis), pars planitis, pan uveitis and
endophthalmitis.
Vitreous aggregates and condensation with
liquefaction. It is the commonest cause of vitreous
opacities. Condensation of the collagen fibrillar
network is a feature of the vitreous degeneration
which may be senile, myopic, post-traumatic or postinflammatory
in origin.
Amyloid degeneration. It is a rare condition in which
amorphous amyloid material is deposited in the
vitreous as a part of the generalised amyloidosis.
These vitreous opacities are linear with footplate
attachments to the retina and the posterior lens
surface.
Asteroid hyalosis. It is characterised by small, white
rounded bodies suspended in the vitreous gel. These
are formed due to accumulation of calcium containing
lipids. Asteroid hyalosis is a unilateral, asymptomatic
condition usually seen in old patients with healthy
vitreous. There is a genetic relationship between this
condition, diabetes and hypercholesterolaemia. The
genesis is unknown and there is no effective
treatment.
Synchysis scintillans. In this condition, vitreous is
laden with small white angular and crystalline bodies
formed of cholesterol. It affects the damaged eyes
which have suffered from trauma, vitreous
haemorrhage or inflammatory disease in the past. In
this condition vitreous is liquid and so, the crystals
sink to the bottom, but are stirred up with every
movement to settle down again with every pause.
This phenomenon appears as a beautiful shower of
golden rain on ophthalmoscopic examination. Since
the condition occurs in damaged eye, it may occur at
any age. The condition is generally symptomless, but
untreatable.
Red cell opacities. These are caused by small
vitreous haemorrhages or leftouts of the massive
vitreous haemorrhage.
Tumour cells opacities. These may be seen as freefloating
opacities in some patients with
retinoblastoma, and reticulum cell sarcoma.