EVALUATION OF GLAUCOMA

AFTER CATARACT SURGERY

Significant glaucoma may develop after complicated cataract surgery with a broken posterior lens capsule and retained lens material. Lens cortex, hemorrhage, and corneal edema may obscure the view of the posterior segment. B-scan ultrasonography can assess the status of the retina and can allow a crude estimate of the amount of retained lens material and hemorrhage in the eye for planning appropriate surgery. A vitrectomy with or without concurrent use of a glaucoma drainage device may be required for intraocular pressure control.

A secondary pigmentary glaucoma can develop after placement of a plate-haptic posterior chamber IOL in the ciliary sulcus. The posterior surface of the iris can rub against the anterior surface of the lens implant haptic, resulting in pigment dispersion. Pseudophakic pigment dispersion usually is more coarse and irregular than in phakic eyes. Iris transillumination defects usually are seen directly over the intraocular lens plate haptic. UBM scanning can show apposition of the intraocular lens plate haptic with the posterior iris surface.

EVALUATION AFTER GLAUCOMA SURGERY

Filtering Bleb

Postoperatively, UBM scanning has been used to evaluate glaucoma filtering blebs after trabeculectomy and nonpenetrating glaucoma surgery.13 Most glaucoma filtering blebs are evaluated easily at the slit lamp, particularly after the most commonly performed glaucoma surgical filtering procedure, trabeculectomy. UBM scanning can determine if there is successful filtration after the less commonly performed nonpenetrating glaucoma filtering surgery, which typically produces

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less elevated and less evident glaucoma filtering blebs (Fig. 9).

Hypotony

In the early postoperative period after glaucoma filtering surgery, intraocular pressure may be low. In the eye with clear ocular media, choroidal effusion may be seen, often presenting a pincushionshaped appearance of the retina and choroid. Typically the filtering bleb is oversized, and the anterior chamber is shallow. B-scan ultrasonography confirms the choroidal separation and echofree suprachoroidal space (see the article by Sharma and colleagues, elsewhere in this issue).

Choroidal Effusion/Hemorrhage

Occasionally, a patient who has a low intraocular pressure develops acute-onset, severe pain in the eye, typically after a Valsalva maneuver. Clinical examination also usually reveals a shallow anterior chamber. The intraocular pressure may be low, normal, or, sometimes, substantially elevated because of a choroidal hemorrhage. Examination of the posterior segment reveals choroidal elevation to varying degrees; however, the choroidal separation typically appears darker than in simple choroidal effusion because of the presence of dark subretinal blood. B-scan ultrasonography can determine whether the choroidal separation is indeed serous and nonhemorrhagic or is hemorrhagic (see the article by Dadgostar and Hayden, elsewhere in this issue). In the former case, the suprachoroidal space is echo-free; in the latter case, internal echoes suggestive of hemorrhage are present on B-scan ultrasonography. Smaller choroidal hemorrhages usually do not require surgical drainage. Larger choroidal hemorrhages, particularly when they extend under the macula or cause opposite sides of the retina to appose

each other (‘‘kissing choroidal hemorrhage’’), usually are drained in the operating room by vitreoretinal surgical specialists (see the article by Dadgostar and Hayden, elsewhere in this issue).

Vitreous Hemorrhage

The presence of a vitreous hemorrhage after choroidal hemorrhage is a more ominous sign, possibly signaling that retinal penetration by the blood has occurred, with the increased likelihood of an associated retinal detachment. B-scan ultrasonography can assist the retinal surgeon in assessing both choroidal hemorrhage and retinal detachment and in planning combined drainage of choroidal hemorrhage and repair of retinal detachment (see the article by Sharma and colleagues, elsewhere in this issue).

Aqueous Misdirection

Early or late after glaucoma filtering surgery, the glaucoma patient may present with a shallow anterior chamber and elevated intraocular pressure. If no choroidal hemorrhage is seen

by direct visualization or on B-scan ultrasonography in a patient in whom there is little or no view of the fundus, aqueous misdirection (formerly termed ‘‘malignant glaucoma’’) is suspect. In aqueous misdirection, posteriorly directed aqueous humor pushes the natural lens or intraocular lens forward, shallowing or flattening the anterior chamber.

Glaucoma Drainage Device

B-scan ultrasonography can be used to evaluate the function of a glaucoma drainage device. Usually, a thick, elevated bleb, visible at the slit lamp, is seen over the surface of the plate of the glaucoma drainage device. If the plate has been placed more posteriorly, the bleb may be more difficult to see. B-scan ultrasonography shows an echo-free cystic space surrounding the plate in an eye with a functioning glaucoma implant (Fig. 10). Elevated intraocular pressure and absence of a visible bleb suggest nonfunction or failure of the glaucoma drainage device.