الفهرس 
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Abstract
Deep lamellar keratoplasty(DLK) is a surgical technique of lamellar Keratoplasty for treating patients with corneal stromal disease and normal endothelium. There are different types of DLK.
1) Deep anterior lamellar Keratoplasty (DALK) which is a technique of corneal transplantation that entails the replacement of diseased host corneal stroma without replacing the healthy endothelium. The current techniques for deep anterior lamellar Keratoplasty are of two kinds.a- Deep stromal dissections achieved manually, microkeratome assisted or using femtosecond laser. b-Planned exposure of DM by the Big Bubble Technique.
2) Deep Posterior lamellar Keratoplasty (DPLK) is also a partial thickness corneal graft that is used to replace endothelium.
Advantages of lamellar over penetrating Keratoplasty are that is considered as extraocular procedure with less potential for intraocular complications , less chance of graft rejection, less wound dehiscence, low rate of chronic endothelial cell loss, donor quality criteria are less stringent, greater graft clarity.While Disadvantages of Deep Lamellar Keratoplasty(DLK) are that is technically difficult,Persistent epithelial defects Less than optimal visual results,precence of Interface scarring.
Indications of Deep Anterior Lamellar Keratoplasty are Keratoconus, Pellucid marginal degeneration,Progressive Post-LASIK keratectasia, Hereditary stromal dystrophies especially avellino, lattice and granular corneal dystrophies while macular dystrophy are not suitable, corneal stromal scars sparing DM, Tectonic indication as in area of thinning or small perforated ulcer Infectious keratitis as herpetic, non-perforated microsporidia, acanthamoebal, post-LASIK mycobacterial and gonococcalarea keratitis.
Contraindication of DALK are
1-Endothelial dysfunction which is an absolute contraindication for DALK.
2-Deep scars involving DM over the entrance pupil and pre-existing defects and breaks in the DM (e.g. acute hyDROPs) are relative contraindications.
Surgical techniques of DALK
Intrastromal air injection Hydrodelamination technique
Melles technique, Big air bubble technique
viscoelastic dissection Automated DALK with microkeratome Femtosecond laser assisted DALK
In Surgical techniques the depth of corneal incisions and lamellar dissections relative to the corneal thickness may be visualized by creating an optical interface at the posterior corneal surface by filling the anterior chamber by liquid or gas of which the refractive index differs from the cornea, for example air and use the folding,mirror,and the indentation effect.
The Big Bubble Technique is the safest and fastest way to expose the DM. The interface between the exposed DM and the Smooth posterior surface of the donor stroma is of high quality, The procedure is repeatable and standerised.InFemtosecond laser-assisted anterior LKP Procedure the FS LaserTM is programmed to produce anterior lamellar and trephination cuts at the desired depth and diameter.In Automated anterior lamellar keratoplasty a microkeratome is used to dissect a hinged anterior corneal flab, measuring 8.5-9.5 mm in diameter and 130-180 um in thickness.
The complications of DALK are DM perforation, Pseudoanterior chamber, fixed dilated pupil, Interface wrinkling, Graft rejection reaction, Interface vascularization and opacification, Interface keratitis.
Surgical techniques of Deep posterior lamellar keratoplasty(DPLK) DLEK,DSEK,DSAEK,DMEK, Automated DPLK, Femtosecond laser-assisted posterior LKP.
-Deep Lameller Endothelial Keratoplasty Procedure. (DLEK)
Surgical techniques either through 5.0mm or 9.0 mm sclera tunnel incision, The inherent value of this technique is that it allows preservation of the normal corneal topography, faster and stronger wound healing, and the avoidance of suture related problems such as induced astigmatism, unpredictable corneal power, infection, ulceration, and suture-induced vascularization leading to graft rejection. The current challenges of this technique are the technical difficulty of the procedure and the challenges in consistently obtaining an optically pure interface.
-Descemet’s Stripping Endothelial and automated Keratoplasty (DSEK) and(DSAEK). Francis W Price further modified and simplified the technique in preparation of the recipient′s bed by stripping off the recipient Descemet membrane, now popularly called ′Descemet stripping and endothelial keratoplasty′ or DSEK. It has the advantage of being easier for the surgeon to perform than DLEK, and of providing a smoother interface, faster visual recovery, better visual quality, no traumatic rupture of globe, no suture-related surface problems and less graft rejection or infection.
Indications of which are Fuchs dystrophy , Bullous Keratopathy, Corneal edema associated with iridocorneal endothelial syndrome and Restore clarity to a failed prior penetrating graft.The Postoperative complication are donor detachment, Graft rejection.
-Descemet’s Membrane Endothelial Keratoplasty (DMEK): With this procedure only donor Descemet and endothelium are transplanted onto the posterior corneal surface of the recipient eye. Manual stripping and dissection by means of specially designed micro- instruments (spatula,hook,etc.) are employed to sparate the donor Descemet’s membrane together with the endothelium from the overlying stroma. The donor endothelial graft can then be preserved rolled up in a special syring and shipped to the surgeon for transplantation.
Technical problems limited its popularity are waste of donor tissue when detaching Descemet from overlaying stroma and difficulties in manipulating the tissue during delivery and positioning.The Indications for DMEK are Pseudophakic or aphakic bullous keratopathy, Fuch’s endothelial disease, Posterior polymorphous corneal dystrophy, Iridocorneal endothelial syndrome, Congenital hereditary endothelial dystrophy, Endothelial decompensation, Endothelial failure in previous penetrating/deep anterior lamellar Keratoplasty, Failed DSAEK/DMEK grafts
-Automated posterior lamellar keratoplasty in which the automated microkeratome can also be used for corneal decompensation secondary to endothelial dysfunction.
In this technique, A hinged anterior stromal flap approximately 350 um (250-450 um) thick is first cut in the host cornea, and the diseased posterior cornea is trephined (the trephine size used depends on the diameter of the flap and hinge width) .The donor cornea is then prepared using the same microkeratome (without the stop screw) to cut the anterior corneal disc, and the residual posterior stroma and endothelium are trephined to the same size.
Complication of Endothelial lamellar keratoplasty are Interface Fluid, Primary Graft Failure, Donor detachment, Graft rejection, Infectious Keratitis, Corneal Graft Folds , Corneal stromal perforation during DLEK, Uncontrolled Glaucoma.