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Relaxing descemetotomy relieves stress forces in taut Descemet’s membrane detachment
The technique allows the Descemet’s membrane to become lax and apposed to the overlying corneal stroma.
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 Amar Agarwal |
Relaxing retinotomy is an established surgical technique in vitreoretinal surgery for periretinal traction and retinal foreshortening that does not allow the retina to settle down. Similar traction on Descemet’s membrane secondary to inflammation or fibrosis or Descemet’s membrane getting incarcerated in a wound or suture can lead to a taut Descemet’s membrane detachment as opposed to a Descemet’s membrane that is stripped and detached from the overlying stroma, such as seen after phacoemulsification. Injecting air or long-acting gas into the anterior chamber in an eye with a taut Descemet’s membrane detachment will not appose it to the corneal stroma because of the foreshortening. Dr. Jacob started a technique called relaxing descemetotomy based on a principle similar to relaxing retinotomy as a solution for this scenario.
Classification
We propose a new classification of Descemet’s membrane detachment based on etiopathogenesis as either a stripped Descemet’s membrane detachment (Figure 1) or a taut Descemet’s membrane detachment (Figure 2).
Stripped Descemet’s membrane detachment occurs intraoperatively and is generally during viscoelastic injection or during insertion of blunt instruments or the IOL.
Taut Descemet’s membrane detachment could be due to inflammation involving the Descemet’s membrane, resulting in fibrosis and consequent contraction causing separation of the Descemet’s membrane from the overlying stroma; secondary incarceration of the Descemet’s membrane in an inflammatory process, eg, in peripheral anterior synechiae or within the graft-host junction; or secondary incarceration in a wound/suture with subsequent contraction. A long-standing stripped Descemet’s membrane detachment could sometimes adhere to intraocular contents with secondary fibrosis, thus turning into a taut Descemet’s membrane detachment.
Diagnosis
Clinical examination, anterior segment optical coherence tomography and intraoperative findings help in determining the extent and characteristics of the taut Descemet’s membrane detachment. A taut Descemet’s membrane detachment is seen stretched out tight like a trampoline between the points of attachment. Slit lamp examination as well as anterior segment OCT determine the extent of detachment and the degree of tautness. Anterior segment OCT is especially invaluable in case of an edematous cornea. The Descemet’s membrane may be seen to be thickened if it is also inflamed.
A stripped Descemet’s membrane detachment is usually seen as an undulating membrane lying loose in the anterior chamber. It may also be scrolled or crumpled up depending on the extent of detachment. On anterior segment OCT, a stripped Descemet’s membrane detachment is seen as an undulating linear hyper-reflective echo in the anterior chamber whereas a taut Descemet’s membrane detachment is seen as a straight, taut line between two points of attachment (Figure 2). Intraoperatively, the characteristic fluttering movements seen with a stripped Descemet’s membrane detachment are not seen in case of a taut Descemet’s membrane detachment on irrigating the anterior chamber with saline.
 Figure 1. A stripped Descemet’s membrane is seen. It is typically seen near incisions and it lies loose, floating in the anterior chamber. It may have a crumpled or rolled-up edge on anterior segment OCT, and it flutters on irrigating the anterior chamber with balanced salt solution. |
 Figure 2. A taut Descemet’s membrane detachment is seen stretched out taut in between points of attachment on anterior segment OCT. It appears as a taut, linear hyper-reflection. Intraoperatively, it does not show much movement on irrigating the anterior chamber with balanced salt solution. Images: Agarwal A
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 Figure 3. Relaxing descemetotomy is done to relieve the tension and stress forces acting on the taut Descemet’s membrane detachment. Once the relaxing descemetotomy cuts are made (shown in arrows), the Descemet’s membrane becomes lax and can now be apposed to the overlying corneal stroma by injecting an air bubble. |
 Figure 4. Preop OCT shows a taut Descemet’s membrane detachment, and postop OCT shows Descemet’s membrane attached after relaxing descemetotomy. |
Surgery
Trypan blue dye may be injected into the anterior chamber to stain the Descemet’s membrane and aid in visualization. The anterior chamber is then irrigated with balanced salt solution to wash away excess trypan blue and to study the dynamics of the detached Descemet’s membrane. An air bubble is then injected to differentiate between a taut Descemet’s membrane detachment and a stripped Descemet’s membrane detachment. If the Descemet’s membrane gets well-apposed to the corneal stroma on injection of an air bubble, it is a stripped Descemet’s membrane detachment, whereas if there is inadequate apposition after air injection, it is a taut Descemet’s membrane detachment and a relaxing descemetotomy is proceeded with.
Relaxing descemetotomy may be performed with the anterior chamber filled with viscoelastic. The tip of a 26-gauge needle is bent in the reverse direction as a capsulotomy needle and is introduced into the anterior chamber to make the relaxing descemetotomy incisions (Figure 3). The extent of the incisions 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. Postoperative tamponade with non-expansile concentration of C3F8 (14%) or SF6 (12%) is given with face-up positioning for 1 hour. Long-acting gas is preferred, as the taut Descemet’s membrane detachment may sometimes take longer to recover function enough to adhere well, thus requiring a longer period of tamponade (Figure 4).
Conclusion
Relaxing descemetotomy incisions act by breaking the stress forces that are acting on the Descemet’s membrane and holding it taut. It makes the Descemet’s membrane lax and thus allows an air or gas bubble to appose Descemet’s membrane against the corneal stroma.
- Amar Agarwal, MS, FRCS, FRCOphth, is director of Dr. Agarwal’s Eye Hospital and Eye Research Centre. Prof. Agarwal is the author of several books published by SLACK Incorporated, publisher of Ocular Surgery News, including Phaco Nightmares: Conquering Cataract Catastrophes, Bimanual Phaco: Mastering the Phakonit/MICS Technique, Dry Eye: A Practical Guide to Ocular Surface Disorders and Stem Cell Surgery and Presbyopia: A Surgical Textbook. He can be reached at 19 Cathedral Road, Chennai 600 086, India; fax: 91-44-28115871; e-mail: dragarwal@vsnl.com; website: www.dragarwal.com.