- 1.
What is retinal detachment?
Retinal detachment (RD) is separation of the neurosensory retina from the underlying retinal pigment epithelium with accumulation of fluid in the potential space between the two layers. The types of retinal detachment include rhegmatogenous, tractional, and exudative.
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In rhegmatogenous retinal detachment (RRD) , a break in the retina allows fluid from the vitreous cavity access to the potential space between the retina and the retinal pigment epithelium.
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Tractional retinal detachment occurs when epiretinal tissue forms and contracts, pulling the retina away from the pigment epithelial layer. Occasionally the severe traction caused by epiretinal membranes may cause a tear in the retina, creating a combined rhegmatogenous–tractional detachment.
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Exudative retinal detachment is produced by retinal and choroidal conditions that damage the blood–retina barrier and allow fluid to accumulate in the subretinal space (the potential space between the retina and the retinal pigment epithelium).
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- 2.
What are the major characteristics of each type of retinal detachment?
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Rhegmatogenous retinal detachments typically have a corrugated appearance caused by intraretinal edema ( Fig. 48-1 ). Obviously, they are associated with a retinal break, although in a small percentage of cases the break is not easily identifiable. Decreased intraocular pressure, pigmented cells in the vitreous cavity, and vitreous hemorrhage are also associated with RRDs. Fixed folds and other signs of proliferative vitreoretinopathy (PVR) strongly suggest an RRD. Extension of fluid through the macula is a poor prognostic sign. The intraocular pressure is usually low.
Figure 48-1
Bullous rhegmatogenous retinal detachment with mobile, corrugated appearance.
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Tractional retinal detachments are characterized by a smooth and stiff-appearing retinal surface. In most cases the epiretinal membranes that cause the traction may be ophthalmoscopically observed. The detachment is usually concave toward the front of the eye. The most common location of the tractional membranes is in the postequatorial region; the traction detachment rarely extends to the ora serrata.
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Exudative retinal detachments are characterized by shifting subretinal fluid. The subretinal fluid accumulates according to gravitational forces and detaches the retina in the area where it accumulates. Thus, the fluid is noted to shift when the patient is viewed in an upright compared with a supine position. The surface of the retina is usually smooth in exudative detachments, compared with the corrugated appearance of an RRD. Occasionally the retina may be seen directly behind the lens in exudative detachments. This rarely occurs in RRDs, unless severe vitreoretinal traction is present.
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- 3.
What are the major causes of exudative retinal detachments?
The major causes of exudative RDs are intraocular tumors, intraocular inflammatory diseases, and congenital abnormalities. Intraocular neoplasms, such as choroidal melanomas, choroidal hemangiomas, and metastatic choroidal tumors, are most likely to produce serous RDs. Intraocular inflammation, such as posterior scleritis, Harada’s disease, severe posterior uveitis, and central serous chorioretinopathy, occasionally produce shifting subretinal fluid. The most common congenital abnormalities known to produce exudative RDs are optic pits, nanophthalmos, and the morning glory disc syndrome.
- 4.
How does the retina remain attached?
The retinal photoreceptors and retinal pigment epithelial (RPE) cells are oriented with the apices of the cells in apposition. An interphotoreceptor matrix between the cells forms a “glue” that helps to maintain cellular apposition. It also has been postulated that the RPE functions as a cellular pump to remove ions and water from the interphotoreceptor matrix, providing a “suction force” that helps to keep the retina attached.
- 5.
What are the major predisposing factors for rhegmatogenous retinal detachments?
The main predisposing factors for RRDs are previous cataract surgery, lattice degeneration, and myopia. The incidence of RRD after cataract surgery is approximately 2 in 1000. The incidence becomes much higher after complicated cataract surgery, including posterior capsule rupture, vitreous loss, and retained lens fragments. Some studies have shown an incidence of RRD after complicated cataract surgery as high as 15%. Currently, approximately half of all primary RRDs occur in patients with a history of cataract surgery.
Lattice degeneration ( Fig. 48-2 ) is a peripheral retinal degeneration characterized by thinning of the retina with liquefaction of the overlying vitreous, which results in a high risk for retinal tears and breaks. Lattice degeneration is found in 6% to 7% of the population and is often bilateral. Lattice degeneration is the direct cause of primary RRD in approximately 25% of eyes.
Figure 48-2
Lattice degeneration.
High myopes have a high risk of RD for several reasons. First, the incidence of lattice degeneration is higher in myopes. Second, myopes tend to have a higher rate of posterior vitreous detachment. Of greater importance, myopic eyes have a higher rate of retinal breaks because of the thin peripheral retina. The rate of retinal breaks tends to be higher with increasing myopia.
- 6.
What are the signs and symptoms of a retinal break?
Flashes and floaters are the classic symptoms. Pigmented cells or blood in the vitreous strongly suggests the possibility of a retinal break.
- 7.
What are the types of retinal breaks?
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Horseshoe tear: A flap of retina created by vitreous traction gives the appearance of a horseshoe. The open end of the horseshoe is anterior. A retinal vessel may bridge the gap of the tear ( Figs 48-3 and 48-4 ). The risk of subsequent RD is high, especially with acute tears.
Figure 48-3
Horseshoe retinal tear with a bridging vessel.
Figure 48-4
Horseshoe retinal tear after laser photocoagulation.
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Operculated tear: When a piece of retina is completely torn away by vitreous traction, the fragment is seen floating over the retinal defect. The risk of RD is lower than with a horseshoe tear.
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Atrophic hole: A round hole without evidence of retinal traction is often associated with lattice degeneration. The risk of RD is low.
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Dialysis ( Fig. 48-5 ): A disinsertion of the retina at the ora serrata, this is most common in the inferotemporal quadrant. The second most common site is superonasal. A frequent cause is trauma.
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