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Descemet’s membrane detachment: A new classification system
New classification system for Descemet’s membrane detachment requires new treatment methods.
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Amar Agarwal, MS, FRCS, FRCOphth, has just completed his 100th Complications Consult column for Ocular Surgery News. Dr. Agarwal is an amazingly talented clinician, surgeon, innovator and leader who is also a prolific writer, sharing his knowledge with ophthalmologists worldwide in more than 60 textbooks, numerous lectures and in our publication, OSN. Amar and I have developed a special friendship, and I am very appreciative of his tireless efforts on behalf of OSN and our readers. On behalf of our entire OSN editorial team and readership, I want to express to him our sincere thanks.
Richard L. Lindstrom
Richard L. Lindstrom, MD
Chief Medical Editor, Ocular Surgery News
Descemet’s membrane detachment is a complication occasionally faced after surgery. A detached Descemet’s membrane can be diagnosed on slit lamp examination as a clear optical space between the stroma and the Descemet’s membrane.
It is conventionally treated by injecting trypan blue dye into the anterior chamber to stain the Descemet’s membrane and to aid in visualization. The anterior chamber is then irrigated with balanced salt solution to wash away excess trypan blue, and the dynamics of the detached Descemet’s membrane may then be better observed (Figure 1). An air bubble or a non-expansile concentration of gases, such as sulphur hexafluoride (SF6) or perfluoropropane (C3F8), is then injected to appose the Descemet’s membrane to the corneal stroma.
Amar Agarwal, MS, FRCS, FRCOphth, (left) was awarded a commemorative plaque for his 100th Complications Consult column at the Indian Intraocular Implant and Refractive Surgery meeting in Chennai, India, in July. Pictured at right, Ashvin Agarwal, MS, son of Amar.
Image: Mullin DW, OSN
New classification
Based on pathological features, Descemet’s membrane detachment was classified in 1928 by Bernard Samuels, MD, as active (pushed back) or passive (pulled back and torn away) due to differences in elasticity between the parenchyma and the glass membrane. 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’s membrane detachment has also been classified as planar (less than a 1-mm gap between the Descemet’s membrane and the stroma) or nonplanar (more than a 1-mm gap between the Descemet’s membrane and the stroma) based on morphology.
Soosan Jacob, MS, FRCS, DNB, proposed a new classification of Descemet’s membrane detachment based on clinico-morphological, etiological, tomographic and intraoperative features, as well as a new treatment algorithm for Descemet’s membrane detachment based on its classification. With newer surgeries such as Descemet’s membrane endothelial keratoplasty (DMEK) gaining acceptance, and a distinct layer of the cornea known as Dua’s layer being recognized, there is a need to focus in greater detail on Descemet’s membrane detachments.
This classification is analogous to the classification of retinal detachment; the Descemet’s 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. Just as a retinal detachment can be classified as rhegmatogenous (secondary to hole, tear or dialysis), tractional or bullous/exudative, Descemet’s membrane detachment can also be classified as rhegmatogenous, tractional, bullous or complex (Table 1).
A rhegmatogenous Descemet’s detachment generally occurs as an intraoperative event when there is a break in the Descemet’s membrane, with fluid accumulation between the Descemet’s membrane and overlying stroma. Analogous to a rhegmatogenous retinal detachment, a rhegmatogenous Descemet’s detachment can be secondary to a hole (eg, a double anterior chamber following perforation during deep anterior lamellar keratoplasty) or a tear (eg, a detachment that occurs during insertion of blunt instruments or IOL implantation during phacoemulsification). Rhegmatogenous detachments can also occur secondary to a dialysis of the Descemet’s membrane from its attachment at the Schwalbe’s line — a complication that is sometimes seen during trabeculotomy, punch insertion in trabeculectomy, anterior chamber maintainer insertion, or if stripping of the Descemet’s membrane accidentally extends toward the periphery during DMEK.
The Descemet’s membrane may also become detached secondary to an inflammatory or fibrotic process, resulting in a tractional detachment. This could occur secondary to incarceration of the Descemet’s membrane in an inflammatory process (eg, in peripheral anterior synechiae or within the graft host junction in large diameter grafts) or to incarceration in a wound or suture with subsequent contraction. A long-standing rhegmatogenous Descemet’s detachment could also sometimes adhere to intraocular contents with secondary fibrosis, thus turning into a tractional Descemet’s detachment.
A bullous Descemet’s detachment can occur secondary to a disease process, such as posterior corneal abscess, tumor, infection or inflammation, similar to bullous/exudative retinal detachment. With this type of detachment, a separation and convex bulging of the Descemet’s membrane into the anterior chamber occurs in the absence of a break in the Descemet’s membrane. The space in between the stroma and the Descemet’s membrane is filled with pus, exudates, fluid, viscoelastic or air, depending on the cause of the detachment. This configuration of Descemet’s membrane can also be seen as part of the Anwar’s big bubble technique in deep anterior lamellar keratoplasty, which detaches the Descemet’s membrane from the stroma and sometimes occurs from accidental injection of viscoelastic into the pre-Descemetic space.
A complex Descemet’s detachment shows complex folds or scrolls, or a combination of other features, and can sometimes occur as the result of a poorly attached DMEK graft.
Anterior segment OCT features
In all cases of Descemet’s membrane detachment, there is generally overlying corneal epithelial and stromal edema, which may make visualization difficult. In this case, the anterior segment optical coherence tomography is useful for diagnosis, as well as for differentiating between various types of Descemet’s membrane detachment.
Figure 1. A stripped Descemet’s membrane is shown. It is typically seen near incisions and it lies loose, floating in the anterior chamber. It may have a crumpled or rolled-up edge with an undulating appearance on anterior segment optical coherence tomography, and it flutters on irrigating the anterior chamber with balanced salt solution.
Figure 2. A taut Descemet’s membrane detachment is seen stretched out in between points of attachment on anterior segment OCT. It appears as a taut, linear, hyper-reflection. Intraoperatively, it does not show much movement upon irrigating the anterior chamber with balanced salt solution.
Images: Agarwal A
Figure 3. Relaxing descemetotomy is done to relieve the tension and stress forces acting on the tractional Descemet’s detachment. Once the relaxing descemetotomy cuts are made (arrows), the Descemet’s membrane becomes lax and can then be apposed to the overlying corneal stroma by injecting an air bubble.
Figure 4. (Top) Preoperative OCT shows a tractional Descemet’s detachment. (Bottom) Postoperative OCT shows the Descemet’s membrane attached after relaxing descematotomy was performed.
A rhegmatogenous Descemet’s detachment is usually seen as an undulating, linear, hyper-reflective signal 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 a rhegmatogenous retinal detachment. On the other hand, a tractional detachment is seen as a straight, taut linear signal between two points of attachment (Figure 2). It has no folds and is not mobile.
With a tractional Descemet’s detachment, the arc length of the cornea is more than the length of the detached Descemet’s membrane, unlike with a rhegmatogenous detachment, where the arc length of the overlying corneal stroma is similar to the length of the detached Descemet’s membrane.
A bullous Descemet’s detachment is seen as a curved, hyper-reflective signal bulging into the anterior chamber from the overlying stroma, and a complex Descemet’s detachment shows complex configurations on anterior segment OCT.
Relaxing descemetotomy
The term “descemetotomy” was first used by Lowenstein in 1993 in reference to a procedure where the Nd:YAG laser was used in the postoperative period to create communication between the anterior chamber and the supernumerary chamber after intentionally retaining the Descemet’s membrane during keratoplasty for bullous keratopathy. Steinemann et al and Masket et al also used the Nd:YAG laser to create a central opening in inadvertently retained opacified host Descemet’s membrane after penetrating keratoplasty.
Previously, the authors used the term “iatrogenic descemetorrhexis” for a case where accidental descemetorrhexis occurred in a patient during phacoemulsification. A similar case was also reported by Pan and Au Eong. Descemetorrhexis has been described as part of endothelial keratoplasty procedures where the central Descemet’s membrane is intentionally removed from the host cornea.
The term “relaxing descemetotomy,” which the authors have coined, differs from the aforementioned terms in that it describes a therapeutic procedure that relieves the traction forces and decreases foreshortening of the Descemet’s membrane in a procedure similar to that of a relaxing retinotomy. The relaxing descemetotomy incisions break the stress forces acting on the Descemet’s membrane. The tautness of the Descemet’s membrane is relieved, and an air or gas bubble is used to appose the now lax Descemet’s membrane against the overlying corneal stroma. A non-expansile concentration of a long-acting gas, such as C3F8 or SF6, may be used to provide a longer period of tamponade, such as is sometimes preferred in more severe and complex cases of rhegmatogenous Descemet’s detachment.
Classification-based treatment
Treatment for each of the Descemet’s detachment classifications varies. Although both rhegmatogenous and tractional Descemet’s detachment require internal gas tamponade or pneumodescemetopexy and internal/external (via corneal stab incisions) sub-Descemet’s fluid drainage, tractional Descemet’s detachment also requires relief or removal of the element of traction for the Descemet’s membrane to settle onto the stroma. This can be done by performing relaxing descemetotomy incisions.
Relaxing descemetotomy may be performed with the anterior chamber filled with viscoelastic or air. The tip of a 26-gauge needle is bent in the reverse direction, as in a capsulotomy needle, and is introduced into the anterior chamber to make the relaxing descemetotomy incisions (Figure 3). The extent of the incision is determined during surgery by assessing the degree of foreshortening that still remains. If foreshortening is not completely relieved, the incisions are further extended until the Descemet’s membrane is able to lie fully apposed against the stroma. These incisions are made in the peripheral cornea avoiding the pupillary plane and the visual axis.
In the presence of synechiae causing tractional Descemet’s detachment, synechiolysis and membrane peeling may also be required to remove tractional fibrotic bands pulling on the Descemet’s membrane. Sub-Descemet’s fluid drainage is carried out by injecting gas from the side opposite to the tear or, in some cases, by making a small stab incision in the cornea overlying the Descemet’s membrane detachment to drain the fluid externally.
Postoperative tamponade with nonexpansile concentration of C3F8 (14%) or SF6 (12%) is administered with face-up positioning of the patient for 1 hour (Figure 4). A reattachment may not occur in all cases, depending on the extent of inflammatory fibrotic damage to the endothelium, in which case the patient may require a posterior lamellar or full-thickness graft. The decision for relaxing descemetotomy is made based on clinical significance of the tractional Descemet’s detachment and the presence of functional endothelium. Clinically insignificant, asymptomatic detachments may be left alone, whereas in case of dysfunctional endothelium, endothelial keratoplasty is preferred.