CLASSIFICATION OF DESCEMET’S DETACHMENT:
Descemet’s detachment (DD) is most commonly seen postoperatively and has classically been treated by injecting air or long-acting gas into the anterior chamber (AC) to appose Descemet’s membrane (DM) against the overlying stroma. This is sometimes combined with stab incisions in the overlying cornea to drain supra-Descemetic fluid (SDF).
However, though this works in the vast majority of cases, there are specific situations when this is not effective. I have described a classification for DD based on etio-pathogenesis, clinical features, optical coherence tomographic, intraoperative features and also described a management protocol for these detachments based on this classification. Analogous to retinal detachment, DD may be classified as – rhegmatogenous DD, tractional DD, bullous DD and complex DD. I have also described a new surgical technique called relaxing descemetotomy which can be used in a few select situations of tractional or bullous DD.
RHEGMATOGENOUS DESCEMET’S DETACHMENT(RDD):
This includes detachments secondary to tear, hole or dialysis of the DM from its attachment at Schwalbe’s line. Though tear is the most commonly seen variant (insertion of blunt instruments/intraocular lens in phaco), hole (microperforation in deep anterior lamellar keratoplasty) and dialysis of DM at Schwalbe’s line (complication during trabeculotomy, viscocanalostomy, punch insertion in trabeculectomy or with peripheral extension of descemetorhexis during endothelial keratoplasty) may also occur. RDD is seen as an undulating membrane clinically and are freely mobile on irrigation with balanced salt solution (BSS) during surgery.
TRACTIONAL DESCEMET’S DETACHMENT(TDD):
This is less common and is caused by traction on or foreshortening of DM secondary to inflammation/fibrosis or its incarceration in a wound/graft-host junction in penetrating keratoplasty/peripheral anterior synechiae or suture. The DD is seen as taut and stretched out. These are not freely mobile on irrigation with BSS.
BULLOUS DESCEMET’S DETACHMENT(BDD):
This is seen as a convex bulge of DM into the AC in the absence of DM break or traction. This is commonly due to introduction of fluid (BSS/viscoelastic/air/blood) in the supra-Descemet’s space during viscocanalostomy or cataract surgery. A possible presentation may be as a localised island of DD in an otherwise attached graft after DM endothelial keratoplasty (DMEK) or due to loculated blood. A BDD is intentionally achieved in Anwar’s big bubble technique.
COMPLEX DESCEMET’S DETACHMENT(CDD)
This type of DD features DM macrofolds/rolls/scrolled edges and combinations of other variants. These may be seen more frequently while learning DMEK secondary to large, improperly repositioned RDD.
Overlying corneal oedema may make visualisation of the DM difficult in DD. Anterior segment-optical coherence tomography (AS-OCT) is therefore very useful for detecting and classifying DD. A rhegmatogenous DD is seen as an undulating linear hyperreflective signal, whereas a tractional DD is seen as a straight taut linear signal with two points of attachment. In tractional DD, the arc length of the detached DM is shorter than that of the overlying cornea, whereas in rhegmatogenous DD these are equal. A bullous DD is seen as a convex hyperreflective signal on AS-OCT, whereas a complex DD shows complex folds, scrolls, adhesions etc.
MANAGEMENT OF DD:
Classifying DD appropriately is important as treatment differs. All DDs require internal air/gas tamponade (pneumodescemetopexy) and SDF drainage. However, a tractional DD also requires relief or removal of the element of traction to allow the DM to settle on to the stroma.
This is a technique described by the author wherein careful small incisions are made on the DM in a can-opener, circumferential pattern in the periphery outside the optic zone. Relaxing descemetotomy relieves traction forces and foreshortening of the DM in a procedure similar to that of relaxing retinotomy described by Machemer in 1979 for tractional retinal detachment to address peri-retinal traction and retinal foreshortening. This is done under pressurised air infusion through an AC maintainer via an air pump in order to perform a controlled surgery. A 26-gauge needle bent upwards similar to a reverse Sinskey at its tip as well as at mid-shaft is introduced into the AC and relaxing descemetotomy incisions are made. The number and extent of the incisions are determined during surgery by assessing the degree of foreshortening. Relaxing descemetotomy incisions break the stress forces acting on the DM, relieving its tautness enabling an air or gas bubble to appose the now lax DM against the overlying stroma. External drainage alone without relaxing descemetotomy does not appose the DM to the overlying stroma because of the DM foreshortening.
A bullous DD requires an outlet for either internal drainage of the SDF by means of descemetotomy incisions or external drainage by stromal stab incisions. Postoperatively, a YAG Descemetopuncture may also be tried. Treatment for complex DD is individualised to the case and could require observation, re-DMEK/re-PDEK with same or different graft, Descemet’s stripping automated endothelial keratoplasty (DSAEK) or penetrating keratoplasty.
The final clarity achieved by the cornea depends not only on whether the DM reattaches, but also on the functionality and count of the endothelial cells. Manoeuvres such as repositioning of graft or relaxing descemetotomy may lead to varying levels of endothelial loss and therefore, I do not recommend these in cases with small, localised DD where the patient is asymptomatic. Similarly, in cases where the endothelium is unhealthy and unlikely to recover, it is preferable to perform an endothelial keratoplasty rather than a relaxing descemetotomy or repositioning.
Rhegmatogenous DD is the most commonly seen form of DD, however tractional DD, bullous DD and complex DD are rarer types of detachments. These should be recognised to facilitate appropriate management in these rarer entities. The configuration of DD should be evaluated clinically as well as by AS-OCT to diagnose the type of DD. Relaxing descemetotomy may be an option in a few select cases.
Dr Soosan Jacob is Director and Chief of Dr Agarwal’s Refractive and Cornea Foundation at Dr Agarwal’s Eye Hospital, Chennai, India, and can be reached at: firstname.lastname@example.org