*5.2.3.3 Bowman layer transplantation*

The PK or DALK may be disrupted by complications such as suture-related problems, graft rejection, epithelial wound-healing abnormalities, corneal curvature changes due to progression of KC in the peripheral host cornea resulting in disappointing visual results [86]. In KC corneas, pathological changes include the reduction of number of keratocytes, organization of the stromal lamellae, fragmentation or absent of Bowman's layer (BL) [91] It has been suggested that the BL may be the strongest biomechanical element of the human cornea followed by the anterior third of the cornea [92]. Therefore, the BL may play a structural role in maintaining the shape/tectonic stability in KC corneas [87]. This procedure was first described in 2014, Bowman's layer graft was positioned inside the recipient corneal stroma in a sandwich technique, without corneal incision or sutures, to pull the anterior corneal surface flatter and create homogeneous corneal topography [86]. BL transplantation can be performed under local anesthesia and low dose topical steroid can stop within 1 year post-operative, minimizing the risk of glaucoma development or cataract formation [86, 87, 93]. The reported complications are low such as intraoperative microperforation of the Descemet's membrane [87, 93]. Because of the transplanted tissue is acellular, no episodes of allograft rejection have been observed [86, 87]. This procedure may postpone penetrating keratoplasty (PK) or deep anterior lamellar keratoplasty (DALK) and potentially allowed long term contact lens wear [86]. Although graft preparation and surgical technique can be challenging, assisted technologies, such as femtosecond laser and intraoperative anterior segment optical coherence tomography (OCT), may

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*Keratoconus Treatment Toolbox: An Update DOI: http://dx.doi.org/10.5772/intechopen.94854*

stages of keratoconus is shown in **Table 5**.

change the course of the disease [15].

are listed in **Table 4**.

**6. Future directions**

**7. Conclusion**

help conquer these barriers [94, 95]. "Bowman layer onlay," a recently developed surgical technique in which an isolated Bowman's layer graft, is positioned onto the patient's anatomical Bowman's layer or anterior stroma, has demonstrated the rapid re-epithelization and integration of the tissue and comparable clinical outcomes to intrastromal transplantation [96]. The outcomes of each keratoplasty techniques

There are a variety of nomograms for the treatment of keratoconus which are mainly focused on the keratoconus grading, risk factors, the progressive nature of the disease, and contact lens tolerance [15]. The management algorithm in various

Treatment for advanced KC has trended away from invasive procedures such as PK and even DALK toward minimally invasive procedures such as CXL, ICRS or BL transplantation. Although keratoconus is a multifactorial disease, the pathogenesis of the disease is very much affected by genetic factors and positive family history [2, 8, 97]. By identifying pathogenic genes and changing the structure of cell proteins, gene therapy may be a very promising and effective treatment modality to

The two most important goals of management of keratoconus are stopping disease progression and visual rehabilitation. An ocular allergy should be treated. Care providers should instruct the patients to avoid eye rubbing to halt disease progression. A careful follow up is needed to document disease progression and provide prompt treatment. A nonsurgical treatment of keratoconus includes spectacles or contact lens. Contact lens use does not slow or halt progression but can provide satisfactory vision in early stages of keratoconus. A contact lens type is selected

The five operations (CXL, ICRS, PK, DALK and BL transplantation) currently represent the available surgical treatment options for advanced KC. Treatment for advanced KC has trended away from invasive procedures such as PK and even DALK toward minimally invasive procedures such as CXL, ICRS or BL transplantation. CXL and ICRS were once regarded only for mild to moderate keratoconus,

PK and DALK provide long term good vision but has slow visual rehabilitation and may be disrupted by complications such as suture-related problems and graft rejection. BL transplantation was introduced for advanced KC with extreme thinning/steepening. This novel procedure may postpone penetrating keratoplasty (PK) or deep anterior lamellar keratoplasty (DALK) and potentially allow long term contact lens wear. Since genetic factors play significant roles in KC, advances in gene

based on the manifest refraction and the degree of keratoconus.

their roles are now expanding in advanced diseases as well.

therapy may soon yield innovative treatments of this disease.

#### *Keratoconus Treatment Toolbox: An Update DOI: http://dx.doi.org/10.5772/intechopen.94854*

help conquer these barriers [94, 95]. "Bowman layer onlay," a recently developed surgical technique in which an isolated Bowman's layer graft, is positioned onto the patient's anatomical Bowman's layer or anterior stroma, has demonstrated the rapid re-epithelization and integration of the tissue and comparable clinical outcomes to intrastromal transplantation [96]. The outcomes of each keratoplasty techniques are listed in **Table 4**.

There are a variety of nomograms for the treatment of keratoconus which are mainly focused on the keratoconus grading, risk factors, the progressive nature of the disease, and contact lens tolerance [15]. The management algorithm in various stages of keratoconus is shown in **Table 5**.
