**5. Discussion**

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

Diagnosis and Treatment of a Rare Complication

After Penetrating Keratoplasty: Retained Descemet's Membrane 125

Fig. 4. Scissors incomplete insertion results in retained Descemet's membrane

retention of the delaminated fetal Descemet's membrane on the recipient bed.

corneal opacity or oedema or after corneal surgeries.

imbibition, dishomogeneous thickness due to the pathology (often keratoconus).

A possible solution to this problem is the use of dye, such as trypan blue or indocyanine green, to highlight the Descemet's membrane. The use of indocyanine green staining of the Descemet's membrane to make DLEK surgery easier has previously been described. Although it bears further study to determine its value, the use of dye after Descemet's stripping in DSEK may improve visualization of this transparent membrane and alleviate the inadvertent

About DALK surgery it's possible to have retained Descemet's in management of a complication such as macroperforation and subsequently surgical switch to PKP in critical condition: shallow anterior chamber, poor surgical field vision for stromal air or fluid

Even during DSAEK Descemet's retention could be a complication which affects the outcome of corneal surgery. Crucial is in this case the presence of folded peripheral spurs that prevent the attachment of donor button being responsible of graft failure. In this case AS-OCT is a useful instrument for the early recognition of retained Descemet's membrane. Retained Descemet's membrane after keratoplasty can be difficult to diagnose in the early postoperative course and AS-OCT may be a useful adjunctive diagnostic tool to aid in the recognition and management of such a complication, especially for patients with either

To determine whether the entire desired surgical area of the Descemet's membrane has been removed in DSEK surgery, practitioners routinely examine the stripped Descemet's membrane during surgery with placement of the tissue onto the anterior corneal surface.

trephination when the recipient cornea is cut. Alternatively, it can be caused by improper instillation of a viscoelastic agent, which can dissect an artificial corneal plane and contribute to inadvertent retention of posterior corneal lamellae.

Fig. 3. Double anterior chamber in retained Descemet's membrane

The principal mechanisms which lead to Descemet's membrane's retention are:


The retained DM may be associated with progressive opacification of the graft that has been postulated to occur due to presence of a sliver of residual stroma with keratocytes from which the fibroblastic activity occurs. The differential time taken for the opacification of the retained DM is due to the thickness of the residual stroma retained along with the DM in these cases.

The best way to avoid this complication is to inspect the wound site carefully with the operating microscope at high magnification and pick up the iris with a fine-tipped forceps to detect a detached Descemet's membrane, especially in oedematous corneal host tissue.

Also, it is important to note that loss of aqueous humour during trephination indicates Descemet's membrane is perforated in 1 or more places, even if this doesn't strictly mean that Descemet's membrane has been completely cut.

trephination when the recipient cornea is cut. Alternatively, it can be caused by improper instillation of a viscoelastic agent, which can dissect an artificial corneal plane and

contribute to inadvertent retention of posterior corneal lamellae.

Fig. 3. Double anterior chamber in retained Descemet's membrane

complete the cut with forceps acting on different levels;

scar's marked fibrosis in case of retransplantation

that Descemet's membrane has been completely cut.

a further resistance to trephination.

these cases.

The principal mechanisms which lead to Descemet's membrane's retention are:

thereby predisposing to its separation from the overlying stroma

 inadvertent and incomplete trephination of oedematous corneas as in congenital hereditary endothelial dystrophy or bullous keratopathy that forces the surgeon to

longstanding stromal oedema which cause loosening of the attachment of the DM,

 stromal recipient imbibitions (not by chance in some techniques of DALK surgery the imbibitions is deliberately requested to make easier the identification of Descemet's membrane). It's important to underline that in case of corneal imbibitions Descemet's membrane becomes thickened due to endothelial decompensation and this fact leads to

The retained DM may be associated with progressive opacification of the graft that has been postulated to occur due to presence of a sliver of residual stroma with keratocytes from which the fibroblastic activity occurs. The differential time taken for the opacification of the retained DM is due to the thickness of the residual stroma retained along with the DM in

The best way to avoid this complication is to inspect the wound site carefully with the operating microscope at high magnification and pick up the iris with a fine-tipped forceps to detect a detached Descemet's membrane, especially in oedematous corneal host tissue. Also, it is important to note that loss of aqueous humour during trephination indicates Descemet's membrane is perforated in 1 or more places, even if this doesn't strictly mean

marked hypotonia of ocular globe with decrease of backpressure during the cut

Fig. 4. Scissors incomplete insertion results in retained Descemet's membrane

A possible solution to this problem is the use of dye, such as trypan blue or indocyanine green, to highlight the Descemet's membrane. The use of indocyanine green staining of the Descemet's membrane to make DLEK surgery easier has previously been described. Although it bears further study to determine its value, the use of dye after Descemet's stripping in DSEK may improve visualization of this transparent membrane and alleviate the inadvertent retention of the delaminated fetal Descemet's membrane on the recipient bed.

About DALK surgery it's possible to have retained Descemet's in management of a complication such as macroperforation and subsequently surgical switch to PKP in critical condition: shallow anterior chamber, poor surgical field vision for stromal air or fluid imbibition, dishomogeneous thickness due to the pathology (often keratoconus).

Even during DSAEK Descemet's retention could be a complication which affects the outcome of corneal surgery. Crucial is in this case the presence of folded peripheral spurs that prevent the attachment of donor button being responsible of graft failure. In this case AS-OCT is a useful instrument for the early recognition of retained Descemet's membrane. Retained Descemet's membrane after keratoplasty can be difficult to diagnose in the early postoperative course and AS-OCT may be a useful adjunctive diagnostic tool to aid in the recognition and management of such a complication, especially for patients with either corneal opacity or oedema or after corneal surgeries.

To determine whether the entire desired surgical area of the Descemet's membrane has been removed in DSEK surgery, practitioners routinely examine the stripped Descemet's membrane during surgery with placement of the tissue onto the anterior corneal surface.

**9** 

*India* 

**Topical Bevacizumab** 

Sandeep Saxena and Neha Sinha

**Therapy in Graft Rejection** 

**After Penetrating Keratoplasty** 

*Department of Ophthalmology, C.S.M. Medical University (Erstwhile King George's Medical University) Lucknow,* 

Neovascularization is defined as formation of new vessels from vascular endothelial cells derived from existing blood vessels. These new immature vessels are friable. They have increased permeability, lack structural integrity, and can result in lipid deposition and corneal opacities. Ultrastructurally, corneal neovascularization is characterized by vessels encroaching through separated stromal lamellae. Corneal vascularization following

Angiogenesis is a complex processs. First, inflammatory mediators trigger vasodilation and increase vascular permeability of limbal and conjunctival vasculature. Vascular endothelial growth factor (VEGF) is one of the most important regulators of corneal angiogenesis. It is produced primarily by macrophages, T cells, and smooth muscle cells in ocular surface. A second important regulator of corneal neovascularization is basic fibroblast growth factor (bFGF) and the third important signal is platelet aggregation factor (PAF). Others include insulin like growth factor, integrins, transforming growth factor, tumor necrosis factor and

Corneal neovascularization can be prevented by various anti angiogenic factors that have been identified in the cornea. Angiostatin, a proteolytic fragment of plasminogen prevents neovascularization and also induces regression of existing vessels. This has been identified in chronic contact lens user where it suppresses the angiogenic stimuli of hypoxia. Second antiangiogenic factor is endostatin which is a proteolytic fragment of collagen XVIII inhibits bFGF and VEGF stimulated corneal neovascularization. Third naturally occurring antiangiogenic factor is pigment epithelium derived growth factor (PEDF) which is a serine

Corneal neovascularization most frequently results from corneal oxygen deprivation, or hypoxia. In response to this hypoxia, the body attempts to provide necessary nutrients and oxygen to the deprived corneal tissues by the creation of new blood vessels. During the early stages, this abnormal growth of blood vessels may produce no signs at all, or it may

protease inhibitor and inhibits bFGF stimulated corneal neovascularization.

**1. Introduction** 

**2. Pathophysiology** 

matrix metalloproteinase.

penetrating keratoplasty may result in graft rejection.

Doing so allows the surgeon to visually inspect the tissue for missing fragments, which could be removed from the anterior chamber. Despite this precaution, it would be difficult, if not impossible, for the surgeon to discern whether a small lamellar remnant was retained on the recipient's posterior cornea.

Retention of the host's Descemet's membrane is a complication which can occur during the course of a penetrating keratoplasty and which eventually leads to loss of graft clarity by clouding or by coming into contact with the graft endothelium. The retained Descemet's membrane can compromise endothelial tissue by contact injury or by limiting diffusion of aqueous humour nutrients. That's why the use of YAG laser could allow not only the optic zone relief but also the diffusion of aqueous humour nutrients, avoiding complications related to retransplantation. Moreover this "non open sky" technique grants us smaller risk of postoperative complications but avoids only a little central hole which results inadequate in case of big descemetical residue. We have also to notice that Yag laser could induce a further Descemet's – endothelial failure thanks to its thermic effect.

#### **6. References**

