|
Approximately 2/3 of the
total volume of the eye is occupied by the vitreous gel.
The vitreous gel is a semisolid or liquid substance that
occupies the space between the lens in the front of the
eye and the  retina lining the back of the eye. The
vitreous gel, under normal circumstances, is colorless
and highly transparent permitting the eye to produce
crystal clear vision. The vitreous gel is made up
primarily of water (99%) and has only 1% solid, chemical
and protein constituents. There are normally no blood
vessels within the vitreous gel. Abnormal blood vessels
can grow into the vitreous gel in a variety of eye
diseases, most commonly diabetic retinopathy. There are,
of course, many blood vessels surrounding the vitreous
gel, primarily in the region of the optic nerve, the
retina itself and other structures of the eye
surrounding the lens. A vitreous hemorrhage occurs when
a blood vessel ruptures and bleeds within the vitreous
gel or near the vitreous cavity. Blood can then enter
into the clear vitreous gel producing visual symptoms.
The initial symptoms of a
sudden vitreous hemorrhage result from a sudden increase
in the number and size of vitreous floaters. Normal
benign, age-related vitreous floaters are related to
protein clumping within the vitreous gel, and are
usually described as thin, transparent lines and dots
that float in and out of the field of vision associated
with eye movement. Abnormal bleeding into the vitreous
gel, however, is associated with a marked increase in
floaters that are dark or red in color. Floaters
associated with bleeding are described as lines or
threads or spider webs or many dark dots. Depending on
the size and degree of the vitreous bleeding, there may
be an associated reduction in vision, so that patients
also describe their vision as blurry or cloudy or hazy.
If the vitreous gel hemorrhage is very significant,
there could be a major loss of vision.
Whenever there has been a
sudden onset of floaters or visual loss in a patient, a
prompt, careful retinal examination is necessary both to
diagnose the underlying cause of the vitreous bleeding
and to determine if any specific therapy is required.
Important factors to
evaluate at the time of the initial examination is
whether or not there is a preexisting systemic disease,
such as diabetes mellitus or sickle cell disease, that
might have predisposed the patient to bleeding into the
vitreous gel. Any significant ocular injury, whether
penetrating or blunt, could also result in acute
vitreous hemorrhage. It is important to know whether the
patient has any previous history of eye disease, such as
a previous retinal vein occlusion, that might have
predisposed the eye to bleeding into the vitreous gel.
It is important to determine the duration of the
vitreous bleeding and whether or not previous episodes
had ever occurred and cleared. We will want to know
whether there are associated symptoms, such as flashing
lights, that might be suggestive of an acute retinal
tear or retinal detachment in addition to the vitreous
bleeding.
A careful examination
will be done promptly to determine the underlying cause
of the vitreous bleeding. Measurement of visual function
will be done initially. The degree of visual blur is
dependent on the amount and location of blood within the
vitreous gel. On occasion there is so much blood within
the vitreous gel that the patient cannot see even hand
motions. When visual acuity is reduced to this degree,
some determination of the visual field will be important
to help to rule out an underlying retinal detachment.
The structures in the front part of the eye will also be
examined. Although rare, structural abnormalities in the
front of the eye, such as an eroding lens implant, could
result in bleeding into the posterior vitreous gel. The
ophthalmologist, with the help of a indirect
ophthalmoscope and using techniques such as scleral
depression, can usually be certain that the retina at
least has not detached even if the entire retina can not
be adequately seen.
In cases where there is
absolutely no view of the retinal structures, even with
the bright instruments available, the ophthalmologist
can utilize diagnostic ultrasonography equipment to
study the interior of the eye. This instrumentation uses
ultrasonic energy to create a picture of the structures
within the eye. This technique will allow us to
determine the degree and extent of retinal attachment
and whether or not there is retinal detachment or any
other abnormality in the eye such as intraocular tumor
formation.
There are many possible
causes for vitreous hemorrhage. The vitreous gel
separates spontaneously from the posterior retina with
age. In the vast majority of eyes, this separation
results in an initial increase in floaters and some
episodes of flashing lights. These symptoms gradually
subside and there is usually no adverse effect on vision
or retinal function. This change in the eye will occur
at a younger age if the eye is highly myopic or if the
eye has undergone previous cataract surgery. Certainly,
ocular injury and any other longstanding ocular disease
can result in premature separation of the vitreous gel.
Whenever there is a significant hemorrhage associated
with an acute posterior vitreous separation, this raises
our concern regarding the possibility of an associated
acute retinal tear. If a retinal tear does exist and it
is not possible to detect this or treat it initially,
this can then lead to a retinal detachment that
ultimately would require surgery to repair. Therefore,
other important causes of acute vitreous hemorrhage
would include both a retinal tear and retinal
detachment.
 If
you do not have a copy of Acrobat Reader you can get one
for free by clicking on the icon, or 'Get
Acrobat® Reader'. This will take you to
Adobe's website and enable you to download the Acrobat
program to your computer.
|
|
