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Differentiation of Descemet’s detachments needed for proper management
The classification includes rhegmatogenous Descemet's detachment, tractional Descemet's detachment, bullous Descemet's detachment and complex Descemet's detachment.
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Descemet’s membrane detachment is a complication occasionally faced by every ophthalmologist. It has been previously classified as planar, or less than a 1-mm gap between Descemet’s membrane and stroma, or nonplanar, or more than a 1-mm gap between Descemet’s membrane and stroma, based on morphology.
As head of the Cornea and Refractive Foundation at Dr. Agarwal’s Eye Hospital, I have had the opportunity to see, analyze and treat many cases of postoperative Descemet’s detachments that have been referred for not settling either spontaneously or after multiple air and long-acting gas injections into the anterior chamber. The clinical findings as well as the anterior segment OCT findings that I observed in these cases led me to propose a classification of Descemet’s detachments into rhegmatogenous Descemet’s detachment, tractional Descemet’s detachment, bullous Descemet’s detachment and complex Descemet’s detachment.
We know that the Descemet’s membrane is a vital layer of the cornea. A closer look, however, shows us that it can be considered analogous to the neurosensory retina in its detachments. Just as a retinal detachment can be rhegmatogenous (secondary to hole, tear or dialysis), tractional, serous/exudative and complex Descemet’s detachments can also be classified similarly.
Rhegmatogenous Descemet’s detachment
A rhegmatogenous Descemet’s detachment is the most commonly seen Descemet’s detachment, generally occurring as an intraoperative event wherein there is a tear in the Descemet’s membrane with fluid accumulating in between the membrane and overlying stroma. This is generally seen after phacoemulsification, with the detachment extending from a large break or tear in the Descemet’s membrane. Rarely, however, a rhegmatogenous Descemet’s detachment can also be secondary to a hole (microperforation during deep anterior lamellar keratoplasty with a detached Descemet’s membrane and a double anterior chamber formation) or a dialysis of the Descemet’s membrane from its attachment at the Schwalbe’s line, such as sometimes seen as a complication during trabeculotomy, punch insertion during trabeculectomy, or anterior chamber maintainer insertion as well as during an end-to-end stripping of the Descemet’s membrane all the way to its attachment at the Schwalbe’s line in an endothelial keratoplasty.
Source: Soosan Jacob, MS, FRCS, DNB
The classical presentation in rhegmatogenous Descemet’s detachment is a sight that is familiar to all ophthalmologists: an undulating membrane with folds that lie loose in the anterior chamber. It may also be scrolled or crumpled depending on the extent of detachment. The folds are mobile, similar to a rhegmatogenous retinal detachment.
Bullous Descemet’s detachment
A bullous Descemet’s detachment, somewhat similar to a serous retinal detachment in its configuration, is in my opinion the second most commonly seen type of Descemet’s detachment. However, it is a commonly misdiagnosed entity and is the type that generally does not respond immediately to repeated bubbling with either air or long-acting gas. It is commonly seen at the end of an uneventful phacoemulsification when the surgeon is performing stromal hydration. Holding the cannula too close to the posterior stroma can cause the fluid wave to propagate between the Descemet’s membrane and the stroma, thus causing a Descemet’s detachment that is essentially fluid trapped under the Descemet’s membrane. This causes a bullous appearance to the membrane, and even though some of the fluid may escape out through the extremely small puncture wound at the site of initiation, it requires creating a larger exit wound for the fluid to completely evacuate and for the detachment to decompress fully with air bubbling in order to allow reattachment.
Most important at this point is for the surgeon to recognize this entity when he sees a fluid wave propagating across the posterior aspect of the cornea, similar to a hydrodissection wave. Once it is recognized as distinct from a rhegmatogenous Descemet’s detachment, it is a simple matter to understand that bubbling alone will not work. In this case, it can be easily decompressed by a technique that I call “relaxing descemetotomy.” This can be performed ab externo by creating a keratome entry into the supra-Descemetic space. This provides an exit route for the fluid to drain out through the cut in the Descemet’s membrane after air bubbling. In the postoperative scenario or in referred cases, it is distinguished from rhegmatogenous Descemet’s detachment as a mildly convex or planar separation of the Descemet’s membrane into the anterior chamber in the absence of a break. The numerous folds seen with rhegmatogenous Descemet’s detachment are not seen here, and it is not freely mobile. Anterior segment OCT confirms these findings.
Rarely, bullous Descemet’s detachment can also occur secondary to accidental injection of viscoelastic into the supra-Descemetic space during viscocanalostomy or cataract surgery and also sometimes secondary to a disease process such as posterior corneal abscess. The type 2 big bubble that sometimes forms during DALK is an example of an iatrogenic bullous Descemet’s detachment. For a more centrally located bullous Descemet’s detachment, an ab interno approach to relaxing descemetotomy can be done either surgically or with the Nd:YAG laser.
Tractional Descemet’s detachment
More rarely the Descemet’s detachment may be detached secondary to an inflammatory or fibrotic process, analogous to a tractional retinal detachment, and I have termed this as a tractional Descemet’s detachment. As already mentioned, this is rare, and we have seen it secondary to incarceration of the Descemet’s membrane in an inflammatory process, for example, in peripheral anterior synechiae, within the graft-host junction or secondary to incarceration in a wound/suture with subsequent contraction. Rarely, a long-standing rhegmatogenous Descemet’s detachment adheres to the iris with secondary fibrosis, thereby turning into a tractional Descemet’s detachment. A tractional Descemet’s detachment is seen stretched out tight like a trampoline between the points of attachment. It has no folds and is not mobile. Sometimes, a tight scroll may be seen stretched out between the two points. In these cases, an ab interno relaxing descemetotomy approach is preferred.
Complex Descemet’s detachment
This refers to cases in which the Descemet’s detachment has multiple Descemet’s membrane macrofolds/rolls/scrolled edges as well as combinations of other variants of Descemet’s detachment.
Role of anterior segment OCT
In all cases of Descemet’s detachment, there is generally overlying corneal epithelial and stromal edema, which may make visualization difficult. Anterior segment OCT is therefore a useful tool for diagnosing this condition as well as differentiating between various types of Descemet’s detachment. A rhegmatogenous Descemet’s detachment is seen as an undulating linear hyperreflective signal in the anterior chamber whereas a bullous Descemet’s detachment is seen as a mild to moderate convex hyperreflective signal bulging into the anterior chamber. A tractional Descemet’s detachment is seen as a taut linear hyperreflective signal between points of attachment. In rhegmatogenous Descemet’s detachment, the arc length of the overlying corneal stroma corresponds to the length of the detached Descemet’s membrane whereas it may not be so in a case of tractional Descemet’s detachment.
Treatment
Treatments differ for these conditions. Rhegmatogenous Descemet’s detachment can be treated by internal air/gas tamponade (pneumodescemetopexy) and supra-Descemetic fluid drainage analogous to internal tamponade and subretinal fluid drainage in retinal detachments. Supra-Descemetic fluid drainage is done by injecting gas from the side opposite to the tear (internal drainage) or in some cases by making a small stab incision in the cornea overlying the Descemet’s detachment to drain the fluid externally, as in Descemet’s stripping automated endothelial keratoplasty. The treatment of bullous Descemet’s detachment has been discussed above. Tractional Descemet’s detachment may also require relaxing descemetotomy incisions.
The final clarity achieved by the cornea depends not only on whether the Descemet’s membrane reattaches but also on the functionality and count of the endothelial cells. In cases with decreased endothelial pump function, the overlying cornea may not clear fully despite successful reattachment and an endothelial keratoplasty may finally be indicated.
Conclusion
It is important to recognize the existence of these distinct entities and to understand the differences among them so as to facilitate proper management. I would recommend that cases with overlying corneal edema undergo anterior segment OCT along the appropriate meridian to diagnose the type of detachment and to decide on appropriate management.
- Reference:
- Jacob S, et al. Cont Lens Anterior Eye. 2015; doi:10.1016/j.clae.2015.03.012.
- For more information:
- Soosan Jacob, MS, FRCS, DNB, is director and chief of Dr. Agarwal’s Refractive and Cornea Foundation at Dr. Agarwal’s Eye Hospital, Chennai, India. She can be reached at email: dr_soosanj@hotmail.com.
Disclosure: Jacob reports no relevant financial disclosures.