11.1 Descemet Membrane Detachment

Descemet membrane detachment is a complication patients occasionally face after surgery. ^{7 ,​ 8} Various techniques have been proposed as treatment for detachment of the Descemet membrane, including observation, ⁹ viscoelastic injection, ¹⁰ air injection, the use of long-acting intracameral gas, ^{11 ,​ 12} and insertion of transcorneal mattress sutures. ¹³ A detached Descemet membrane can be diagnosed on slit-lamp examination as a clear optical space between the stroma and the Descemet membrane.

Trypan blue dye may be injected into the anterior chamber to stain the Descemet membrane and aid in visualization. The anterior chamber is then irrigated with balanced salt solution (BSS) to wash away excess trypan blue and to study the dynamics of the detached Descemet membrane (Fig. 11.1). An air bubble is then injected to appose the Descemet membrane to the corneal stroma. Gases, such as sulphur hexafluoride (SF6) or perfluoropropane (C3F8), can also be used in more severe or long-standing cases.

11.2 New Classification of Descemet Membrane Detachment

Based on pathological features, in 1928, Samuels classified Descemet membrane detachment as active (pushed back) or passive (pulled back and torn away) owing to differences in elasticity between the parenchyma and the glass membrane. ⁶ Samuels also stated that this classification was more relevant pathologically and no great importance could be ascribed to these forms of detachment from the surgical standpoint. Descemet membrane detachment has also been previously classified as planar (a 1-mm or smaller gap between the Descemet membrane and the stroma) or nonplanar (a gap of 1 mm or larger) between the Descemet membrane and the stroma) based on morphology. ⁷

Dr. Soosan Jacob proposed a new classification of Descemet membrane detachment based on the clinicomorphologic, etiologic, tomographic, and intraoperative features and proposed a new treatment algorithm for detachment of the Descemet membrane based on its classification. This classification is analogous to the classification of retinal detachment. The Descemet membrane is a vital layer of the cornea and is necessary for maintaining the clarity of the cornea, just as the neurosensory retina is required for visual perception. Because retinal detachment can be rhegmatogenous retinal detachment (RRD [secondary to hole, tear, or dialysis]), tractional retinal detachment (TRD), or bullous/exudative retinal detachment (BDD), we would classify Descemet membrane detachment as RDD, TRD (or TDD), BDD, or complex detachment (CDD) (Table 11.1).

An RDD generally occurs as an intraoperative event when there is a break in the Descemet membrane with fluid accumulation between the Descemet membrane and overlying stroma. Analogous to an RRD, an RDD can be secondary to a hole (e.g., a double anterior chamber after perforation during deep anterior lamellar keratoplasty) or a tear (e.g., Descemet membrane detachment occurring during insertion of blunt instruments or IOL implantation during phacoemulsification). RDD can also occur secondary to dialysis of the Descemet membrane from its attachment at the Schwalbe line, a complication that is sometimes seen during trabeculotomy, punch insertion in trabeculectomy, or anterior-chamber maintainer insertion or if stripping of the Descemet membrane accidentally extends toward the periphery during endothelial keratoplasty of the Descemet membrane.

The Descemet membrane may also become detached secondary to an inflammatory or fibrotic process, resulting in TDD, which is analogous to a TRD. This could occur secondary to incarceration of the Descemet membrane in an inflammatory process (e.g., in peripheral anterior synechiae or within the graft-host junction in large-diameter grafts) or secondary to incarceration in a wound or suture with subsequent contraction, resulting in a TDD. A long-standing RDD could also sometimes adhere to intraocular contents with secondary fibrosis, thus turning into a TDD. A BDD can occur secondary to a disease process, such as posterior corneal abscess, tumor, infection, or inflammation (analogous to bullous retinal detachment). In this type of Descemet membrane detachment, a separation and convex bulging of the Descemet membrane into the anterior chamber occur in the absence of a break in the Descemet membrane. The space between the stroma and the Descemet membrane is filled with pus, exudates, fluid, viscoelastic, or air, depending on the cause of BDD. This configuration of Descemet membrane can also be seen as part of the Anwar “big bubble” technique in deep anterior lamellar keratoplasty, which detaches the Descemet membrane from the stroma and sometimes occurs from accidental injection of viscoelastic into the pre-Descemetic space. ³³ Clinically, an RDD is usually seen as an undulating membrane lying loose in the anterior chamber. It may also be scrolled or crumpled, depending on the extent of detachment. It has folds and is mobile, similar to an RRD. On the other hand, a TDD is stretched out tight, like a trampoline, between the points of attachment. It has no folds and is not mobile. A BDD is seen as a convex membrane bulging into the anterior chamber, similar to a bullous retinal detachment. A complex Descemet detachment shows complex folds or scrolls or shows a combination of features of others and can be seen sometimes in a poorly attached Descemet membrane endothelial keratoplasty (DMEK) graft.

11.3 Anterior-Segment OCT Features

In all cases of Descemet membrane detachment, there is generally overlying corneal epithelial and stromal edema, which may make visualization difficult. In this case, the anterior-segment OCT is useful for diagnosing this condition, as well as differentiating between various types of Descemet membrane detachment. An RDD is seen as an undulating linear hyperreflective signal in the anterior chamber, whereas a TDD is seen as a straight, taut linear signal between two points of attachment (Fig. 11.2). In TDD, the arc length of the cornea, if measured, is found to be more than the length of the detached Descemet membrane, unlike in RDD, where the arc length of the overlying corneal stroma is similar to the length of the detached Descemet membrane. A BDD is seen as a convex, hyperreflective signal bulging into the anterior chamber from the overlying stroma, with the space between filled with exudate, pus, fluid, or air, depending on the cause of the Descemet membrane detachment. A CDD shows complex configurations on anterior-segment OCT.

Intraoperatively, TDD can be verified by its more immobile nature and the absence of the typical undulating movement that is associated with an RDD on irrigating the anterior chamber with BSS. A taut Descemet membrane does not move with the undulations seen in an RDD, although with BSS it might show some sharp, small, fluttery movements on forcible irrigation.