Retinal detachment
Retinal detachment
refers to separation of the inner layers of the retina(Neurosensory retina)
from the underlying retinal pigment epithelium (RPE). it is one of the most
time-critical eye emergencies encountered in the emergency setting. Normally, the retinal pigment epithelium is
able to maintain adhesion with the overlying neurosensory retina through a
variety of mechanisms. These mechanisms include active transport of subretinal
fluid and interdigitation of outer segments and the retinal pigment epithelium
microvilli. With retinal detachment, these mechanisms are overwhelmed leading to
separation of the neurosensory (inner layers) retina from the retinal pigment
epithelial layer.
Depending upon the
mechanism of Separation of the sensory
retina from the underlying RPE ;retinal detachment can be of of three types:-
A) Rhegmatogenous(Derived from, greek word, rhegma
meaning rent or break) Retinal detachment:-
A hole, tear, or break(. in the neuronal layer allowing fluid from the
vitreous cavity to seep in between and separate sensory and RPE layers (ie,
rhegmatogenous RD).The retinal breaks may be
of different types:- a) U-tears (horseshoe)
consist of a flap, its apex pulled anteriorly by the vitreous, the base
remaining attached to the retina.
b) Operculated
tears in which the flap is completely torn away from the retina by detached
vitreous gel to leave a round or oval break,
c) Retinal holes are round or oval, usually
smaller than tears and carry a lower risk of RD. Round holes may occur in
lattice degeneration.
d) Dialyses are circumferential tears along the ora
serrata; vitreous gel remains attached to the posterior margin. They can cause
RD, often slowly progressive .It may be associated with blunt ocular trauma. They
typically appear as large very peripheral breaks with a regular rolled edge.
Pathophysiology of Rhegmatogenous RD(RRD) Vitreoretinal traction is responsible for the occurrence of most
RRD. As the vitreous becomes more syneretic (liquefied) with age, a posterior
vitreous detachment (PVD) occurs. In most eyes, the vitreous gel separates from
the retina without any sequelae. However, in certain eyes, strong vitreoretinal
adhesions are present and the occurrence of a PVD can lead to a retinal tear
formation; then, fluid from the liquefied vitreous can seep under the tear,
leading to a retinal detachment.
Forces
promoting retinal detachment include vitreous traction, gravity and eye
movements.
Active traction on the flap of a horseshoe tear accelerates the
passage of liquid vitreous into the subretinal space. Gravity promotes the
spread of subretinal fluid, particularly with superior breaks.
A number of conditions exist that predispose to a PVD by
prematurely accelerating the liquefaction of the vitreous gel. Myopia, aphakia
or pseudophakia, familial conditions, and inflammation are among the common
causes. In other cases, retinal necrosis with a retinal break formation occurs;
then, fluid from the vitreous cavity can flow through the breaks and detach the
retina without there being overt vitreoretinal traction present. This commonly
occurs in acute retinal necrosis syndrome and in cytomegalovirus (CMV)
retinitis in AIDS patients.
B) Tractional Retinal
detachment:- Traction from inflammatory or vascular fibrous membranes on the
surface of the retina, which tether to the vitreous. proliferative membranes on the surface of the
retina or vitreous cause tractional retinal detachment.Proliferative membrane seen in proliferative retinopathy due to
diabetic disease, sickle cell and other disease processes leading to
neovascularization of the retina. proliferative vitreoretinopathy may be seen
after trauma or surgery These
membranes can pull on the neurosensory retina causing a physical separation
between the neurosensory retina and retinal pigment epithelium. This is called
a traction retinal detachment.
C)
Exudative retinal detachment:- It
is due to accumulation of subretinal fluid due to
inflammatory mediators or exudation of fluid from a mass lesion. This mechanism
is known as a serous or exudative retinal detachment. Serous detachments are
caused by a number of inflammatory, or exudative retinal disease processes such
as Sarcoidosis or choroidal neoplasms,exudative choroiditis or
retinopathy,toxaemia of pregnancy. Serous retinal detachments may also be the
presenting sign in patients with aggressive metastatic cancer.Tumours of the
choroid produce detachment partly by lifting retina mechanically and partly by
transudation of fluid due to circulatory disturbances caused by the tumor
Retinal detachments may
be associated with congenital malformations, metabolic disorders, trauma
(including previous ocular surgery),[1] vascular disease, choroidal tumors, high myopia
or vitreous disease, or degeneration.
Diagnosis:-
1. Diagnosis of Rhegmatogenous Retinal detachment:-
Diagnosis of retinal detachment is done by
seeing the retina with the help of an ophthalmoscope(e.g:- Indirect
Ophthalmoscope).In some situations where there is difficulty in viewing the
fundus(e.g:- Vitreous haemorrhage,dense cataract,) ultrasonography can detect
retinal detachment.
History:-
Specifically ask patients
about risk factors that predispose to premature PVD.
·
Myopia
·
Prior intraocular surgery
·
Family history
·
RRD in the fellow eye
Patient may have the following complains:-
Photopsias
Photopsias refer to the
perception of flashing lights by the patient. It probably arises from the
mechanical stimulation of vitreoretinal traction on the retina. It may be
induced by eye movements and appears to be more noticeable in dim illumination.
Visual field defect
Patients often describe
a black curtain (visual field defect) once the subretinal fluid extends
posterior to the equator.
Floaters
Floaters are opacities
in the vitreous that cast a dark shadow according to their form and shape in
the patient's visual field as they float in the vitreous cavity.
A ring-shaped floater is
the Weiss ring or the remnant of the hyaloid that was attached to the edges of
the optic disc.
Cobwebs are caused by
condensation of the collagen fibers.
Small spots usually
indicate fresh blood due to the rupture of a retinal vessel during an acute
PVD.
Loss of central vision
When the macula becomes
detached (ie, extension of subretinal fluid into the macula), the patient
experiences a drop in visual acuity.
In other cases, a large bullous
detachment may obstruct the macula, causing decreased visual acuity despite the
fact that the macula is not detached.
Signs:-
Cell and flare may be seen in the anterior chamber of eyes with a
rhegmatogenous retinal detachment (RRD).
The intraocular pressure is usually lower in the eye with a RRD
than in the fellow eye; this is usually reversed by retinal reattachment. In
certain cases, the intraocular pressure may be higher than in the fellow eye.
Pigment in the anterior vitreous (tobacco dusting or a Shaffer
sign) is usually present.
Once
the retina becomes detached, it assumes a slightly opaque color secondary to
intraretinal edema. It has a convex configuration, has a corrugated appearance,
and undulates freely with eye movements unless severe proliferative
vitreoretinopathy (PVR) is present. Proliferative
vitreoretinopathy (PVR) is caused by epiretinal and subretinal membrane
formation, contraction of which leads to tangential retinal traction and fixed
retinal fold formation
There is loss of the underlying choroidal
pattern and retinal blood vessels appear darker than in flat retina.SRF can
spread upto ora serrata.
A retinal break in the shape of a horseshoe or flap is often
present. Of all RRDs, 50% have more than 1 break. Of all breaks, 60% are
located in the upper temporal quadrant, and 15% are located in the upper nasal
quadrant. Another 15% are in the lower temporal quadrant, and 10% are in the
lower nasal quadrant (modified from
Lincoff’s rules).
Chronic RRD may present with retinal thinning, intraretinal cysts,
subretinal fibrosis, and demarcation lines. These lines are usually at the
junction of attached and detached retina. Even though they represent areas of
increased retinal adhesion to the RPE, it is not uncommon for subretinal fluid to
spread beyond the lines.
Relative afferent pupillary defect (Marcus Gunn pupil) is present in an eye
with an extensive RD.
Ultrasonographic
finding of RRD:-
On Bscan, it appears as echogenic dense
membrane, biconvex or biconcave with 100% attachment at the optic nerve head
(ONH) and 90- 100% reflectivity on Ascan. Attachment at ONH is not seen in
localized, peripheral RD where membrane is visible only in a single quadrant.If
after movemrnt is present,it means that the RD is fresh.Sometimes retinal tears especially operculated tears/
giant tears and even the trickle of vitreous haemorrhage from the break site
into the vitreous cavity may be picked up.
2. Diagnosis
of Exudative Retinal detachment:-
History
Patients may complain of
a red eye (eg, uveitic pathologies).
Patients may notice a
decrease in vision or visual field defect.
Pain may be present (eg,
scleritis).
Parents may notice a
white pupil (leukocoria).
There is no vitreoretinal traction, so
photopsia is absent.
Floaters
may be present if there is associated vitritis.
Signs:-
Bullous retinal detachment with shifting subretinal fluid:
Depending on the position of the patient, the fluid accumulates in its most
dependent position.
The retina is characterized by a smooth surface that lacks folds
as seen in a rhegmatogenous retinal detachment (RRD).
The anterior segment may show signs of inflammation (eg,
episcleral injection, iridocyclitis) or even rubeosis depending on the underlying
cause.
In chronic cases, deposition of hard exudates may be seen.
Dilated telangiectatic vessels may be seen.
‘Leopard spots’ consisting of scattered
areas of subretinal pigment clumping may be seen after the detachment has
flattened
Ultrasonography:-
The cause of exudative RD,e.g:- a choroidal
tumor may be evident.
3. Diagnosis of Tractional RD:-
History:-
Vitreoretinal traction develops insidiously in most cases(So
photopsia and floaters are absent).
The visual field defect progresses slowly and may become
stationary for months or years.
If the macula becomes involved, the patient will experience a drop
in vision.
Clinical
Features:-
The detachment has a concave configuration.
The subretinal fluid is shallower than in RRD and often does not
extend to the ora serrata.
The highest elevation of the retina occurs in sites of
vitreoretinal traction.
Retinal mobility is severely reduced, and shifting fluid is
absent.
Ultrasonographic finding:-
fibrovascular frond within the vitreous
cavity or along the vitreous face may be seen. This frond when exerts
tractional force on the retina, produces tent like elevation from the retina as
an echogenic membrane which may be localized or extensive enough to become total.
It does not show after-movement and vitreous cavity may show evidence
suggestive of old haemorrhage. On As c a n t h is t h i c k membrane produces
100% reflectivity. At times thick vitreous may be difficult to differentiate
from RD as it may have an attachment to the ONH and Quantitative echography II
may be used to differentiate the two.
Management:-
1. Rhegmatogenous retinal detachment:-
The two most important factors in the
development of RRD are retinal breaks and vitreous traction. Therefore, the two
goals of retinal reattachment surgery are to seal all retinal breaks with minimum iatrogenic damage and to relieve all vitreous traction. Most early surgical
failures are due to the inability to achieve one or both of these goals. Late
surgical failures are typically due to development of proliferative
vitreoretinopathy.
Closure of
the breaks occurs when the edges of the retinal break are brought into contact
with the underlying RPE. This is accomplished either by bringing the eye wall
closer to the detached retina (a scleral buckle) or by pushing the detached
retina toward the eye wall (intraocular tamponade with a gas bubble). Sealing
of the breaks is accomplished by creating a strong chorioretinal adhesion
around the breaks; this may be completed with diathermy, cryotherapy, or laser
photocoagulation.
(N.B:- Retinal breaks
without RD can be treated with laser (via a slit lamp or BIO) or cryotherapy.)
Pneumatic retinopexy
Pneumatic retinopexy is an outpatient
procedure in which an intravitreal gas bubble together with cryotherapy or
laser are used to seal a retinal break and reattach the retina without scleral
buckling. The most frequently used gases are sulfur hexafluoride (SF6) and the longer-acting perfluoropropane (C3F8). It has the advantage of being a
relatively quick, minimally invasive, ‘office-based’ procedure. However,
success rates are usually worse than those achievable with conventional scleral
buckling.
Principles of scleral buckling
Scleral buckling,
sometimes referred to as conventional or external RD surgery as opposed to the
internal approach of pars plana is a surgical procedure in which material
sutured onto the sclera (explant) creates an inward indentation. Its purposes
are to close retinal breaks by apposing the RPE to the sensory retina, and to
reduce dynamic vitreoretinal traction at sites of local vitreoretinal adhesion.
• Explants are made from soft or hard silicone. The entire break should
ideally be surrounded by about 2 mm of buckle. It is also important for the
buckle to involve the area of the vitreous base anterior to the tear in order
to prevent the possibility of subsequent reopening of the tear and anterior
leakage of SRF. The dimensions of the retinal break can be assessed by comparing
it with the diameter of the optic disc.
• Buckle configuration can be radial, segmental, circumferential or encircling, depending
on the size, configuration and number of breaks.
• Technique. A
conjunctival peritomy is performed with isolation of the recti muscles.
Indirect ophthalmoscopy is used to localize all the breaks. Once
the breaks are localized, they are usually treated with cryotherapy.
A buckling element is chosen and sutured over the breaks.
The surgeon decides whether to drain the subretinal fluid. The
buckle is adjusted to an appropriate height. The central retinal artery is
monitored carefully during this maneuver.
In cases where the subretinal fluid is not drained, an anterior
chamber paracentesis and/or liquid vitreous removal is performed.
Subretinal fluid drainage:-
The drainage of the subretinal fluid is a controversial topic
among vitreoretinal specialists. Reasons given for drainage include reduction
in intraocular volume, which allows elevation of the buckle without the
problems of increased intraocular pressure and settling of the breaks on the
buckle allowing rapid closure of the breaks.
Complications during drainage include choroidal hemorrhage,
retinal perforation, retinal incarceration, and choroidal neovascularization.
Complications
of scleral buckling
Postoperative glaucoma: Angle closure may occur secondary to a
detachment and an anterior displacement of the ciliary body.
Anterior segment ischemia: Patients at risk are those with sickle
cell (SC) hemoglobinopathy and high encircling buckles. Infection and extrusion
of the buckle probably occur in 1% of cases. In these cases, the buckle needs
to be removed.
Choroidal detachments have been reported to occur in as many as
40% of cases. They arise from vortex vein obstruction. Most cases can be
followed without drainage.
Cystoid macular edema arises from the inflammatory response to the
surgical trauma. Its incidence is reported to be around 25% of cases
Strabismus following scleral buckling occurs in as many as 50% of
cases. It is more common after reoperations. Most cases resolve spontaneously.
However, as many as 25% have long-standing diplopia. The main cause is
restrictive strabismus. This may be corrected with prisms, botulinum toxin
injections, or surgery with adjustable sutures.
Macular pucker has been reported in as many as 17% of cases.
PVR is the most common cause for surgical failure. In this
condition,
Persistent subclinical subfoveal fluid has been reported to be
present in up to 45% of eyes after successful retinal reattachment with scleral
buckling at 6 months and 11% at 12 months.
Buckle extrusion, intrusion or infection :-Removal is usually
required, with aggressive antibacterial therapy as indicated.
Buckle failure may occur due to inadequate
size, incorrect positioning or inadequate height or due to missed break; Fish-mouthing’
(Fig. 16.38D) describes the phenomenon of a tear, typically a large superior
equatorial U-tear in a bullous RD, to open widely following scleral buckling,
requiring further operative treatment.
Pars
Plana Vitrectomy:-
Vitrectomy
begins with the removal of the vitreous humor causing the retinal detachment,
followed by displacement of the subretinal fluid by means of a heavy tamponade
and scarring of the retina by laser coagulation or cryocoagulation. The
vitreous is then replaced by a tamponade.
Over the
past decade, more and more surgeons have been advocating pars plana vitrectomy
for the primary management of retinal detachments probably due to the
vitreo-retinal training patterns and better technology in vitrectomy machinery
and wide angle visualization.
Technique involves a standard 3-port pars plana vitrectomy with
removal of the juxta basal vitreous. During this process, retinal breaks are
identified, freed of vitreous traction and marked. Internal subretinal fluid
drainage is then performed by one of 3 techniques: either through the causative
anterior breaks using perfluorocarbon liquids or through one of the causative
anterior breaks using a cannulated extrusion during fluid–air exchange or
through a posteriorly created retinotomy during fluid–air exchange. The breaks
are then treated with endolaser, either through perfluorocarbon liquids or
under air. Some surgeons will only treat the identified retinal breaks, whereas
some other will perform 360° peripheral laser, placing several rows posterior
to the vitreous base. The air is finally exchanged for a longacting gas/
silicone oil. The patient has to maintain position postoperatively.Vitrectomy can be done with 20 gauge system.Now a days
sutureless 23G,25G and 27G system has become more popular.
Combined
PPV and Scleral Buckle
At times,
combined PPV/SB may be indicated to repair a primary retinal detachment. In these situations, a solid silicone encircling
element is placed around the eye to support the posterior vitreous base and a
vitrectomy is performed and drainage of subretinal fluid is performed
internally. The PPV/SB can be used in situations where there is widespread
peripheral pathology associated with a retinal detachment.
2. Treatment
of Exudative RD:-
Treatment depends on
the cause. Some cases resolve spontaneously, whilst others are treated with
systemic corticosteroids (Harada disease and posterior scleritis). In some eyes
with bullous central serous chorioretinopathy, the leak in the RPE can be
sealed by laser photocoagulation.
3.Treatment of Tractional RD:-
Depending on the underlying cause and extent of the TRD, surgical
intervention is offered to patients. For instance, a patient with TRD secondary
to PDR that does not threaten the macula probably can be monitored closely. The
main surgical goal in all these cases is to relieve vitreoretinal traction.
Traction may be relieved with scleral buckling techniques and/or with
vitrectomy.
In certain cases, combined RRD and TRD may be present. Usually,
the retina becomes detached from the vitreoretinal traction. With further
traction, small breaks may occur causing a combined TRD-RRD. In these cases,
the surgical goal is to identify all the breaks and to close them in addition
to the relief of vitreoretinal traction.
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