122 I: Principles

rhegmatogenous detachments. The retina is generally tight and on stretch in tractional detachments, whereas rhegmatogenous detachments are more loose and undulating. Tractional detachments may be complicated by the development of a retinal tear with the development of features of rhegmatogenous detachment. Since PVR is primarily a tractional process, rhegmatogenous retinal detachment may likewise develop some features of tractional detachment. Because vitreoretinal traction is the cause of retinal tears, traction is a factor in the development of most rhegmatogenous detachments.

CAUSES OF TRACTIONAL RETINAL DETACHMENT

Tractional detachments are frequently due to vascular proliferation triggered by ischemia; thus they are caused by proliferative diabetic retinopathy, retinal vein occlusion, cicatricial retinopathy of prematurity, or proliferative sickle retinopathy. Penetrating trauma may also cause tractional detachment. Underlying causes of the tractional process should be sought.

The treatment for tractional retinal detachment usually involves a vitrectomy with peeling or dissection of the tractional membranes, and treatment of any coexisting retinal breaks (see Chapter 9). Treatment of underlying conditions (such as diabetes) is emphasized.

LESIONS SIMULATING RETINAL DETACHMENT

Lesions that might be confused with retinal detachment include degenerative retinoschisis, choroidal detachment, tumors of the choroid, vitreous membranes, and white-with-pressure or white-without-pressure.

Retinoschisis

Elevation of the retinal surface may be due to retinoschisis instead of retinal detachment. Retinoschisis constitutes splitting of the sensory retina into two sheets, like separating the two plies of a tissue. It differs from retinal detachment in that the outer retina is still attached to the eye wall. (See also Chapter 2, page 25.)

Retinoschisis can also coexist with retinal detachment, called schisis detachment. When retinoschisis accompanies detachment, it predates the onset of detachment. An attempt should be made to record the extent of the schisis cavity, as well as the area of detached retina. Determining the extent of each where there is overlap is often difficult, but this becomes better defined during cryopexy. A diagnostic feature of retinoschisis is the “white Swiss cheese” appearance of the outer layer of the schistic retina as it is frozen. In contrast, the retinal pigment epithelium deep to an overlying detached retina appears dull orange when viewed during cryopexy.

Type 1 schisis detachment refers to detachment that does not extend beyond the area of retinoschisis, whereas type 2 schisis detachment extends beyond the schisis (Figure 5–29). Type 2 schisis detachments generally require retinal detachment repair, whereas type 1 generally do not. Type 2 schisis detachments accompanied

SCHISIS

RD

PE

choroid

sclera

Figure 5–29. Cross-section of type 2 schisis detachment.

by extensive schisis generally have a poorer prognosis for surgical repair than detachments without schisis.

Surgical repair of schisis detachments focuses on closing outer layer breaks and full-thickness retinal breaks. Inner layer breaks do not require treatment.

Retinoschisis is classified as flat or bullous. As a rule, flat retinoschisis is not progressive or slowly progressive. Occasionally, bullous retinoschisis will progress and threaten to involve the macula.

Intraretinal macrocysts

Intraretinal macrocysts, which are defined as focal secondary retinoschisis, may mimic degenerative retinoschisis. They occur only in areas of long-standing retinal detachment. Intraretinal macrocysts are usually 2 or 3 disc diameters in size and are most often found in the periphery. Macrocysts require no special treatment and disappear after retinal reattachment. (see Figure 2–27)

Choroidal detachment

Choroidal detachment is usually bullous, with a smooth rather than undulating contour. Nasal or temporal bullae tend to be larger than superior and inferior bullae. Usually, the brown choroid can be seen immediately beneath the retina, and the translucent appearance seen with a retinal detachment is lacking (Figure 5–30).

In the deep valleys between choroidal bullae, the choroid is tethered to the sclera by the vortex veins or along the course of the long posterior ciliary artery and nerve. The result is a characteristic “hour glass” configuration to the bullae (Figure 5–31). The tethering effect tends to limit the posterior extension of the detachment, and therefore the posterior pole is often spared. While retinal detachment usually extends anteriorly only as far as the ora serrata, detachment of the choroid extends anteriorly to the scleral spur. There may be folds in the retina, but usually there is little or no retinal detachment associated with choroidal detachment.

Most choroidal detachments are serous, but occasionally a hemorrhagic detachment is seen. Serous and hemorrhagic detachments can be readily differentiated by scleral transillumination. There are many causes for choroidal detachment, but the most common is hypotony following intraocular surgery, especially trabeculectomy and sometimes cataract surgery.

124 I: Principles

Figure 5–30. Choroidal detachment.

Figure 5–31. Typical configuration of choroidal detachment with limited serous retinal detachment.

Choroidal detachment usually requires no intervention. However, if the anterior chamber angle has been closed because of pressure from behind, resulting in a marked increase in intraocular pressure, surgical drainage of the choroidal detachments may be necessary to reduce the pressure. Also, when choroidal detachment is so massive that it brings the retina from opposite sides of the eye together in the middle of the vitreous cavity, retina-to-retina adhesions may develop over time, and surgical intervention may be necessary to prevent this.

Figure 5–32. Malignant melanoma.

Choroidal tumors

Occasionally, elevated choroidal lesions are confused with retinal detachments. An experienced observer can tell the difference between a choroidal detachment or choroidal mass and a retinal detachment. The choroidal lesion appears more solid, lacking the translucent appearance of a retinal detachment. Choroidal lesions also tend to be smooth in contour, lacking the undulations of retinal detachment (Figure 5–32). However, secondary serous retinal detachment may also be present, which can make the distinction more difficult (as discussed above).

Vitreous opacities

When the view is cloudy, vitreal membranes or hemorrhage may mimic retinal detachment. In contrast to retinal detachment, vitreal membranes are avascular or have abnormal neovascularization, unlike normal retinal vasculature. With cloudy media, ultrasound may be helpful in making the distinction. Sometimes retinal detachment cannot be ruled out. Serial observations can rule out progression, or a vitrectomy may be indicated to clear the media and allow treatment of retinal detachment if present.

White-with-pressure and white-without-pressure

Where the vitreous is adherent to the peripheral retina, the retina may take on a whiter color than the surrounding area, visible at all times or only visible with pressure from scleral depression. This is usually fairly well demarcated and geographic in shape, and may mimic the coloration of a shallow retinal detachment. By placing the area in question on the crest of scleral indentation while examining with an indirect ophthalmoscope, the absence of separation from the underlying retina can be determined.