الفهرس 
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Abstract
Keratoconus is a vision disorder that occurs when the normally round cornea (the front part of the eye) becomes thin and irregular (cone) shaped. This abnormal shape prevents the light entering the eye from being focused correctly on the retina and causes distortion of vision.
Keratoconus causes blurring and distortion of vision and increased sensitivity to glare and light. These symptoms usually appear in the late teens or late 20s.
In patients with advanced keratoconus treatment options such as contact lenses or ICRS may fail to improve the CDVA often requiring keratoplasty, either lamellar or full thickness, depending on the extent of the stromal scar.
PKP has traditionally been the surgery of choice for keratoconus, but nowadays lamellar techniques are the gold standard for patients with moderate to severe disease. Currently, an elective PKP is reserved for those advanced cases with hydrops or deep corneal scar involving DM.
The precise apposition between the graft and host is an important goal of keratoplasty and is also a prognostic factor affecting the surgical outcome.
Many studies found correlation between size of mal apposition and IOP, final refraction, keratometric cylinder, wound strength and one study found a correlation between thickness disparity at wound interface and keratometric cylinder but they evaluated manual PKP cases only
So we conduct our study to compare between femtosecond laser assisted PKP and femtosecond laser assisted DALK regarding CCT, malapposition type and size, thickness disparity at wound interface in cases of moderate to severe keratoconus.
We find that all the graft–host junctions have continuous smooth epithelial surface.
But regarding internal malapposition we found in DALK 80.8% graft host junctions are well apposed compared to 18.3% graft host junctions in PKP group and 19.2%are malapposed compared to 81.6% mal apposesed junctions in PKP group and the difference between 2 groups was highly significant p-value < 0.001.
In PKP there are 4 types of malapposition. The most common form of mal apposition is stepping represent 54.2% from total graft host junctions and the second is protrusion 23 graft host junction 19.2% from the total graft host junctions and. The third is gapping 6.7%juctions and the last is tag 1.7% junctions.
We find only 1 type of malapposition protrusion represent 19.2% of the DALK graft host junctions and the difference in protrusion between both groups isn’t statistically significant but we don’t find any stepping, gapping so the difference is statistically significant between both groups.
There isn’t statistically significant difference between both groups regarding thickness disparity and centeral corneal thickness.
Conclusion
Based on our results we believe that DALK surgery is the gold standard and the best care of management of cases of advanced keratoconus not only because less endothelial rejection, less endothelial loss after surgery, being closed system surgery, less post operative complication, less use of steroids, early suture removal, and giving comparable visual acuity with new techniques compared to PKP but also it preserve the normal anatomy keep DM intact which possibly increases the graft apposition, wound strength, lessens exposure to bare sclera and as shown in previous studies less apposition less IOP, keratometric cylinder, total refraction.