**3. Retention of Descemet's membrane**

120 Keratoplasties – Surgical Techniques and Complications

place with four cardinal sutures whose depth is typically 90% of the corneal thickness. After placement of the 12 o'clock suture, particular attention is paid to the 6 o'clock suture because these two sutures follow a vertical line and bisect the entire donor button such as the two at 3 and 9 o'clock. The rest of the sutures could be a combination of interrupted and

But since the advent of penetrating keratoplasty surgeons have recognized the undesirable postoperative consequences of full-thickness corneal surgery such as high astigmatism, unpredictable refractive outcomes and prolonged visual rehabilitation. That's why ophthalmologists have conceptualized more selective transplanting techniques such as deep

Lamellar keratoplasty involves placing a partial thickness donor corneal graft within a recipient corneal bed prepared by lamellar dissection of abnormal corneal tissue. It could be considered an alternative surgical option to penetrating keratoplasty in many specific cases such as all the ectactic corneal disorders that don't affect the endothelial cell layer. Lamellar keratoplasty offers several advantages over traditional PKP by avoiding complications associated with the "open sky" surgery and decreasing allograft rejection. The goal of this kind of surgery is a sufficient restoration of optical clarity of the central cornea; achievement of this objective is dependent upon a clean and complete posterior lamellar dissection of the host's corneal stroma from Descemet's membrane. An inadequate dissection could result in stromal and interface opacification and irregular

Descemet's stripping automatic endothelial keratoplasty (DSAEK) has become the preferred method of corneal transplantation for endothelial disease with improved safety, reduced astigmatism, and faster visual recovery. It is often performed with topical anaesthesia and monitored intravenous sedation. With the patient in a supine position, the horizontal corneal diameter of the recipient eye is measured with callipers to guide the selection of an appropriate donor tissue diameter. A 5 mm temporal clear corneal or sclera tunnel incision is made in the recipient eye. If the recipient epithelium is hazy or scarred it can be removed and this usually improves the view into the eye. Multiple ink points around the entire diameter of recipient cornea are used to lightly mark the surface of the recipient cornea to delineate the area for Descemet's membrane removal. The recipient endothelium, in fact, should only be stripped from the area that will be covered by the donor tissue because any stripped area not covered with donor tissue will become oedematous. To prevent this occurrence some surgeons score an area somewhat smaller than the planned donor diameter. Trypan blue could also be introduced in the anterior chamber to improve membrane visualization during the stripping. Descemet's membrane is then scored in a circular pattern along the perimeter of the area to be removed with a modified hook. During the scoring and stripping steps the anterior chamber can remain formed by continuous infusion of balanced salt solution or air (we prefer to avoid the use of viscoelastic because, if it will not be completely removed before inserting the donor button, it will impair donor

After the donor tissue is inserted the anterior chamber is inflated by injecting air or balanced salt solution which allows the posterior portion of the donor tissue to unfold. The anterior chamber is then completely filled with air to firmly press the donor tissue up against the

running sutures.

astigmatism.

adherence).

recipient cornea.

stromal and endothelial keratoplasty.

Retention of the host's Descemet's membrane is a complication which can occur during the course of a penetrating keratoplasty (but also DALK and DSAEK present retention of Descemet's complications) and which eventually leads to loss of graft clarity by clouding or by coming into contact with the graft endothelium. Penetrating keratoplasty is a common technique with good prognosis value and has been the first choice for corneal endothelial decompensation even if in the last years for this kind of diseases DSAEK is preferred in order to its minimal sequelae. DSAEK requires much less manipulation of the recipient cornea and anterior chamber, compared with the earlier PK and DALK procedure and this help to minimize intraoperative and postoperative complications. Moreover DSAEK technique does not induce significative alterations of corneal topography so that it could be considered an essentially refractive neutral transplant procedure.

Postoperative complications of penetrating keratoplasty include high or irregular astigmatism, prolonged wound healing, late wound dehiscence with trauma, suture-related infections, vascularisation, and graft rejection. The most postoperative complication with DSAEK, instead, is that sometimes the donor tissue detaches in the early postoperative period (from 1 day to 1 week after surgery) so that additional air must to be injected to again firmly press the donor tissue against the recipient cornea.

In addition, retention of the host's Descemet's membrane can be seen as a rare complication of these surgical techniques. The retained Descemet's membrane can compromise endothelial tissue by contact injury or by limiting diffusion of aqueous humour nutrients.

Fig. 1.a Retained Descemet's membrane after PK treated with YAG laser

Diagnosis and Treatment of a Rare Complication

which it was performed a retransplantation.

his right eye was limited to hand motions.

**4.2 Case 2** 

**4.3 Case 3** 

**5. Discussion** 

After Penetrating Keratoplasty: Retained Descemet's Membrane 123

A 54 year old white woman was referred to our department on December 2002. The patient was diagnosed as having glaucoma in 1990 and since than on she was treated with Timololo. In 1998 a cataract extraction was performed in patient's right eye and on December 03, 2002 she underwent a penetrating keratoplasty in RE for endothelial decompensation. After surgery the patient reported excellent visual function lasting for some time but on July 2003 she had experienced decreased visual acuity and marked diffuse corneal oedema, later on

On the first post-operative control the slit lamp biomicroscopy revealed a Descemet's retention with a supernumerary anterior chamber so that the patient underwent descemetorhexis to leave the pupillary field one month later. Nine months after the treatment the patient had a best-corrected visual acuity of 5/10 and the graft was clear.

An 81 year old man with a history of cataract extraction in both eyes, glaucoma and penetrating keratoplasty in right eye in 2000, was referred to the Department of Ophthalmology of San Matteo General Hospital with ocular pain and marked reduction of visual acuity. In spite of risks connected with his glaucomatous history, the patient opted for new surgical treatment and on October 2003 he underwent a new penetrating keratoplasty. On the first post-operative control was referred Descemet's retention from removed graft. On September 2004 the graft appeared oedematous and with a lot of new vessels all around the limbus. Because of this on November 23, 2004 was performed a new penetrating keratoplasty in right eye. On the last control (September 2010) the patient's visual acuity in

These cases document the occurrence of a retained Descemet's membrane following penetrating keratoplasty especially in case of severe oedema and thickening of the recipient cornea, which facilitates the separation of Descemet's membrane and, in turn, incomplete

Fig. 2. Partial double anterior chamber in retained Descemet's membrane

Unfortunately the patient did not complete the follow-up in our department.

Fig. 1.b Retained Descemet's membrane after PK treated with YAG laser

This complication consists in the incomplete removal of the host cornea: after partial trephination we make an opening into the anterior chamber and introduce curved corneal scissors. Especially in an oedematous cornea it could occur that the lower blade is placed anterior to Descemet's membrane so that, when the button is lifted from the eye, a portion of Descemet's membrane leaves behind.

The result is a wavy, diaphanous membrane that creates a supernumerary anterior chamber behind the graft on the first postoperative control by slit lamp examination.

The following case histories from the Department of Ophthalmology of San Matteo General Hospital of Pavia, may help to illustrate the course and prognosis of this mishap.
