Shadi Awwad, MD
Posterior
Vitreous Detachment (PVD)
A. Definition
It is the separation of the vitreous from the posterior
portion of the retina. The prevalence increases with
age and axial length (Myopia). It is found in 60% of people above
70 years of age.
B. Clinical Features:
Patients with acute PVD experience brief flashes of light (
photopsia) and/or "floaters". Flashes represent retinal
stimulation from vitreous traction whereas floaters are shadow
cast from particulate matter suspended in the vitreous over the
retina, and these can be: vitreous collagen fibers, hemorrhage, or
epiretinal glial tissue torn from the optic disk. At least one
retinal tear is found in 15% of patients with acute PVD, and if
vitreous hemorrhage is seen, a tear is found in 2/3 of cases. PVD
might tear the retina at areas where the vitreous is firmly
attached. When a piece of the retina is torn free, the remaining
tear is called operculated tear. When the torn retina
remains adherent , we have a flap oor Horseshoe tear. Flap
tears are more likely to progress into retinal detachment than
operculated tears, because of the continuing vitreal traction on
the retinal flap.
C. Management
The fundus should be carefully examined to rule out retinal
tears
Retinal Detachment
A. Definition
It is the
separation of the sensory retina (photoreceptors and inner tissues
up the nerve fiber layer) from the retinal pigment epithelial
layer.
B. Classification
Retinal
detachments are divided into 3 categories according to the
etiology
A.
Rhegmatogenous
B.
Tractional
C.
Exudative
I. Acute Rhegmatogenous Retinal
Detachment
Liquefied vitreous gets access to the subretinal space through an
existing retinal break(rhegma means break in greek) and peels off
the sensory retina from the underlying pigment epithelium. It
occurs in patients with a history of previous trauma to the eye,
myopes ( due to thin retina and liability to tears), and
peripheral retinal degenerations like lattice degeneration.
a) Clinical Features:
There is a
history of recent flashes and floaters in 50% of cases. If the
detachment is recent, the detached retina appears opaque and
corrugated with loss of underlying choroidal details; it undulates
but the sub-retinal fluids do not shift. Patients might notice a
visual field loss, and if the macula becomes involved, a sudden
decrease in central vision, "as if a veil has been dropped
down" before one's eye.
Fig.1: Rhegmatogenous retinal detachment
b) Management:
1. Scleral
Buckle:
A kind of silicone explant is mounted over the sclera 360 degrees
and tightened in order to indent the sclera and make it
apposed to the underlying detached retina.
2. Pneumatic
Retinopexy:
Intra-ocular injection of gas ( air or expandable gas) in order to
tamponade the retinal detachment and break while the choroidal
adhesions form.
Each procedure requires location of the tear and treating the
retina around its edges by cryotherapy or laser in order to create
firm adhesions between the sensory retina and the RPE layer and
preventing detachmnent. The gas bubble will expand and being
lighter than the ocular fluids, will migrate upward to tamponade
superior breaks. Hence positioning post-op is of critical: if the
break is in the posterior pole (close to the macula), the patient
should remain face down. If the break was in the right temporal
retina, he should lie flat on his left side. Positioning should be
applied for the first 2 weeks. Pneumatic retinopexy is best done
for superior breaks.
3. Vitrectomy
with silicone oil injection:
When the retina detaches, a large number of retinal pigment
epithelial cells can separate from Bruch's membrane. These will
float in the vitreous or under the retina and proliferate together
with glial tissue, forming contractile membranes. These
contractile fibrovascular membranes can open preciously closed
retinal breaks or produce tractional retinal detachment on top of
an existing rhegmatogenous retinal detachment. This entity is
labeled Proliferative Viteoretinopathy (PVR), and is considered an
ominous sign. The surgeon has then to perform a vitrectomy, peel
off the traction bands and membranes, and inject silicone
oil to tamponade the the break and detachment for a long time, in
fear of recurrence. Silicone oil should be removed subsequently
after 3 to 12 months to prevent toxicity to the cornea, lens
(cataract), trabecular meshwork(glaucoma), etc.. Silicone oil
injection . It has the advantage of staying for a long time and
does not require positioning post-op. But in view of its higher
specific gravity(0.97) and its non-expandability, its tamponading
effect is less.
II. Traction Retinal Detachment
A. Definition:
The retina is
pulled into the vitreous cavity by transvitreal traction.
B. Etiology:
Diabetic Retinopathy, PVR, old
penetrating injuries...
C. Clinical Features:
The detached retina
is smooth, immobile, and concave toward the pupil. No breaks are
usually found on ophthalmoscopy.
D. Management:
Vitrectomy,
with release of vitreous tractions is required. Scleral Buckle,
injection of gas or oil, laser and cryotherapy are additional
interventions.
III. Exudative Retinal Detachment
A. Definition:
The
result of collection of fluid beneath an intact sensory retina.
B. Etiology:
Choroidal neoplasm (e.g
melanoma), chorioretinal inflammatory diseases, malignant
hypertension (as in toxemia of pregnancy), hemorrhage from a sub
retinal neo-vascular membrane( as in AMD), systemic vascular and
inflammatory diseases.
C. Clinical Features:
Smooth,
transparent, dome-shaped retinal elevation with shifting
fluids (upon head maneuvers). No retinal breaks nor
pigment clumps or red blood cells in the vitreous are identified.
Rhegmatogenous retinal detachment must still be ruled out by a
careful fundus exam .
D. Management
Treat the
underlying condition if possible.
IV. Symptoms
and corresponding signs of acute retinal diseases
| Symptoms |
Signs |
|
Photopsia |
Migraine
Retinal break
Posterior Vitreous Detachment
Retinal detachment |
|
Floater |
Vitreous detachment
Vitreous hemorrhage
Retinal break with hemorrhage
Any of the above with retinal detachment |
|
|
