pathogenisis of rhegmatogenous rd

7/28/2019 Pathogenisis of Rhegmatogenous RD

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Pathogenisis Of

Rhegmatogenous RD

Dr Nadia Amin


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Definition

Retinal detachment is the separation of the

neurosensory retina (NSR) from the underlying

retinal pigment epithelium (RPE). These two layers are derived from

neuroectoderm that lines the optic vesicle during

embryogenesis.

As the optic vesicle invaginates to form the optic

cup, the two layers come in apposition.


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The inner layer differentiates into the NSRand the outer into RPE.

No real anatomic junctions form between

the cells of the two layers.Therefore, theforces of attachment of the NSR to RPEare weak.

A retinal detachment occurs when theforces of adhesion between the NSR andthe RPE are overwhelmed


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Types of retinal detachment:

There are four major types of retinal

detachment:

rhegmatogenous,

traction,

exudative or serous,

combined traction-rhegmatogenous.


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Rhegmatogenous retinal

detachment

Rhegmatogenous retinal detachment

(RRD) is characterized by the presence of

a full thickness retinal break.

This break is held open by vitreoretinal

traction that allows accumulation of

liquefied vitreous under the retina

separating it from the RPE.


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The precursors to this type of retinal

detachment are liquefied vitreous,

tractional forces that can produce and

maintain a retinal break, and a breakthrough which fluid gains access to the

subretinal space


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Even if a full thickness break is present in the

retina, a retinal detachment will not occur if the

vitreous is not at least partially liquefied and if

the necessary traction is not present. Vitreous syneresis, which culminates in posterior

vitreous detachment (PVD), can produce all

three precursors of RRD. This is why in most

instances an RRD is preceded by a PVD.


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. Depending on the location of this

pathology, RRD can be classified into

Equatorial,

Oral

Macular RRD

Equatorial RRD occurs in cases of

myopia, lattice degeneration, horseshoetears and round retinal holes.


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Oral RRD is most commonly seen in

cases of aphakia, pseudophakia, and

giant retinal tears.

Macular type is seen in high myopia,

traumatic holes and idiopathic macular

holes.


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Otherless frequent causes of RRD

include various forms of necrotizing

retinitis, like toxoplasmosis,

cytomegalovirus infection, and acuteretinal necrosis syndrome all of which

increase the chance of developing full

thickness retinal tears.


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Predisposing factors to retinal

detachment

. These include vitreoretinal adhesions in

association with PVD; local ocular diseases such

as retinoschisis and myopia; cataract surgery;trauma;.

Most of these entities predispose to RRD

because of the high incidence of associated

vitreous detachment and retinal breaks.


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. RRD in retinoschisis occurs when holes

are present in both the inner and outerlayers of the retina involved by schisis.

In these cases fluid passes into the

subretinal space through the inner andouter holes.

Retinoschisis was observed in 2.5% of

patients with RRD.


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Myopia is a definite risk factor for retinaldetachment and the risk increases withhigher degrees of myopia.

PVD occurs early, lattice degeneration ismore common and the retina is thinner inmyopic patients than in emmetropes, andthis makes retinal breaks and detachment

a more frequent occurrence and they areoften bilateral.


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POSTERIOR VITREOUS

DETACHMENT (PVD

1. it is defined as a separation betweenthe posterior vitreous cortex and theinternal limiting membrane (ILM) of

the retina.2. At the initial examination, more than

10% of patients with symptomaticPVD may have retinal breaks orretinal detachments that require

immediate treatment.


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Safe versus anomalous PVD:.

SafePVD: For PVD to occur withoutcomplications (safe PVD), two differentprocesses must occur concurrently and toa similar extent:

weakening of vitreo-retinal adhesion

and vitreous liquefaction. There must besufficient weakening of vitreo-retinal

adherence so that when the criticalamount of liquefaction has developed, thecollapsing vitreous separates away fromthe retina and PVD occurs withoutcomplications.


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Anomalous PVD

Anomalous PVD results when the extent

of vitreous liquefaction exceeds the

degree of weakening of vitreo-retinal

adherence and traction is exerted at thisinterface.


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Symptoms o f acu te PVD

Acute PVD usually occurs between 4565years in the general population, but mayoccur earlier in myopic individuals.

.Vitreous separation may go unnoticed bythe patient, but in those individuals whoare symptomatic, acute PVD is associated

with a sudden onset of new floaters


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. Ind i rect ophthalmoscopy:Using indirect ophthalmoscopy with

indentation is the main method ofevaluation of the retina in cases withacute PVD.

Peripheral punctate intraretinalhemorrhages may indicate areas oftransient vitreous traction during the

PVD event and may represent thesites for future retinal tears.


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. The presence of vitreous hemorrhageis important risk factor that warrants

extensive examination of retinalperiphery.

The incidence of retinal tears in acute

PVD with vitreous hemorrhage was foundto be 70% compared with a 2% to 4%

incidence in acute PVD without vitreous

hemorrhage.


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PVD and fellow eye

PVD and fellow eye: Patients with

unilateral PVD are potentially at risk

of developing retinal breaks or retinaldetachments associated with PVD in

the fellow eye.


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. In conclusion, acute PVD is a

common event that usually endswithout major complications.

Symptomatic acute PVD carries ahigh risk of retinal tear anddetachment that warrants prompt andaccurate follow up and management.


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pathogenisis of rhegmatogenous rd

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