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Superfi cial anterior lamellar keratoplasty (s-ALK). For superfi cial stromal
disorders a microkeratome or femtosecond laser assisted lamellar resection
from 100 to 400 µm stromal depth followed by transplantation of a donor
lamella of the same dimensions onto the recipient bed can be performed.
The automated or laser assisted nature of the dissection results in smoother
and enhanced high quality as compared to manual dissection. The major
disadvantage of this procedure is the possibility of sub-optimal visual
outcomes due to interface related problems. Conditions such as anterior
stromal scarring following infectious keratitis or corneal stromal dystrophies
affecting superfi cial layers are the main indications of this procedure
(Shousha et al. 2011).
Deep anterior lamellar keratoplasty (DALK). DALK can be performed in most
diseases treated by PK in which there is a healthy corneal endothelium.
The principle of this technique is to remove all recipient stromal tissue
to Descemet's membrane (DM) and place a donor cornea over the bed
after DM and endothelium removal. The main parameter for good visual
function after DALK is the thickness of residual recipient stromal bed
( Fig. 4 ) (Ardjomand et al. 2007). The drawback of DALK is that deep
dissection is time consuming and relatively diffi cult with a steep learning
curve.
Two main techniques are performed to get this aim. Melles reported a
technique for effective tissue dissection using air injection in the anterior
chamber. The difference in optical index between cornea and anterior
chamber fi lled with air makes the dissection easier (Melles et al. 1999).
Anwar described the “big bubble technique” consisting in forceful intra-
stromal air injection to split DM away from the posterior stroma. Clean
Figure 4 Left: Surgical view of the bared Descemet membrane after deep lamellar dissection.
Small bubbles of air show the integrity of the anterior chamber. Right: Graft sutured with
10/0 nylon interrupted suture technique. Coloured graft is due to the use of trypan blue in
the harvest of Descemet-endothelium complex for a DMEK with the split technique.
Color image of this figure appears in the color plate section at the end of the topic.
 
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