**5.1 Nonsurgical treatment**

*Eyesight and Imaging - Advances and New Perspectives*

than 1.5 D within 12 months

not required to document progression [10].

treatment toolbox is listed as in **Table 1**.

**Nonsurgical treatments Surgical treatments**

12 months

**5. Treatment**

• **Glasses**

• **Contact lens (CL)** Soft CL; toric, non-toric Rigid CL; RGP Hybrid lenses, Piggyback lens (PBCL)

Miniscleral Semiscleral Scleral lenses

*Photo Refractive Keratectomy.*

*The keratoconus treatment toolbox.*

2.An increase in (corneal) myopia by more than 3 D or astigmatism by more

3.An increase in mean corneal refractive power by more than 1.5 D within

4.A reduction in minimal corneal thickness of more than 5% within 12 months.

The important goals of keratoconus management are stopping disease progression and visual rehabilitation [10]. In cases of ocular allergies, patients should be treated with topical antiallergy and lubricants and should be instructed to avoid eye rubbing to halt disease progression. Corneal collagen crosslinking is a promising procedure to stop disease progression with minimal side effects [29]. For the visual rehabilitation, several treatment options corresponding to keratoconus grading have been established. Keratoconus can be treated by both nonsurgical and surgical approaches depend on severity and progression of the disease [15]. The keratoconus

• **Corneal collagen cross-linking (CXL)**

CXL + TG- PRK + phakic IOLS CXL + ICRS + phakic IOLS CXL in thin cornea

• **Corneal transplantation** Penetrating keratoplasty (PK)

*RGP = Rigid gas permeable contact lens, IOL = intraocular lenses, PBCL = Piggyback lens, TG-PRK = Topo guided-*

Bowman layer transplantation

• **Intrastromal corneal ring segments (ICRS)**

Deep Anterior Lamellar Keratoplasty (DALK)

Standard CXL Epi-on CXL Accelerated CXL CXL Plus CXL + TG-PRK CXL + ICRS

The regular topographic/tomographic check-ups can identify keratoconus progression. Regarding the examination intervals, the individual risk profiles need to be taken into consideration. The risk factors that should be considered include eye rubbing, ocular allergies, young age, steep corneal curvature gradient, high astigmatism, marked visual loss, documented progression in the fellow eye, atopic dermatitis or Down's syndrome [28]. In children, keratoconus tends to be more severe and progress faster requiring closer follow-up intervals [26]. The patient with low risks can be monitored less frequently than the one with high risks. Keratoconus progression is often associated with a decrease in best spectacle-corrected visual acuity (BSCVA), however, a change in both uncorrected visual acuity and BSCVA is

**40**

**Table 1.**

A nonsurgical treatment of keratoconus is spectacles and contact lens. For early stage of disease, those who achieve visual acuity 20/40 or better, spectacles can provide acceptable vision [15]. A toric soft contact lens also provides satisfactory vision for correcting myopia and regular astigmatism in early keratoconus. However, as the diseases progress, spectacles or soft contact lens may not provide acceptable vision because of the higher- order aberrations, in particular vertical coma was increased [30]. Therefore, other special lens such as rigid gas permeable (RGP) contact lens, hybrid lenses, piggy back, miniscleral lens, semiscleral lens or scleral lenses are needed to provide satisfactory vision [31]. The ultimate goal of fitting contact lens in keratoconus is to improve visual acuity without compromise ocular health. However, contact lens use does not slow or stop progression of the disease. In keratoconus, the cone is steeper but the cornea beyond the cone is flatter. In mild keratoconus, traditional RGP lens can provide an ideal fit. However, as the disease progress into advanced stages, it becomes difficult to achieve an ideal fit but compromised fit which is not damage to the ocular surface is acceptable. High oxygen transmissibility lens should be selected to prevent hypoxic-related corneal changes [31].

The type of contact lens selection is based on manifest refraction, degree of keratoconus, and morphology of the cone [31]. Corneal topography can aid in addressing the severity and morphology of the cone. Buxton et al. have classified keratoconus based on keratometry values (K) at the apex of the cone: mild if K is less than 45 D, moderate if K is between 45 and 52 D, advanced if K is more than 52 D and severe if K is more than 62 D [32]. The morphology of the cone is classifed as the following [33].


The three essential parameters in contact lens fitting are power, diameter, and base curve of contact lens.


A contact lens type is selected based on the manifest refraction and the degree of keratoconus. The contact lens of choice for keratoconus patients is RGP lens. However, if the patients develop intolerance or discomfort, customized soft toric contact lens, PBCL, hybrid lens or scleral lens can be considered. The indications, advantages and disadvantages of each contact lens type are summarized as in **Table 2** [30, 31, 34]. Fitting contact lens in keratoconus can improve vision and


*RGP = Rigid gas permeable, Hybrid lens = rigid lens in the center and a soft skirt in the periphery, PBCL = Piggy back lens (RGP lens sitting on top of a soft contact lens) KC = keratoconus, GPC = giant papillary conjunctivitis, VA = visual acuity.*

**43**

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

*5.2.1 Corneal collagen cross-linking (CXL)*

collagen covalent bonds [37].

to 370 nm UVA with an irradiance of 3 mW/cm2

keratoplasty [31].

**Table 3**.

**5.2 Surgical treatment**

delay the need for keratoplasty. Moreover, contact lens in keratoconus patient also have a role in correcting residual refractive error after Corneal collagen cross-linking (CXL), after Intrastromal corneal ring segments (ICRS) or post-

Even though the specialized imaging device can provide grading scheme of keratoconus, for practical purposes, the term "advanced keratoconus" may apply to any cases that have unacceptably poor spectacle distance vision and contact lens intolerance. As the diseases progress, spectacles or contact lens cannot provide acceptable vision. This group of patients requires a surgical management such as Corneal collagen cross-linking (CXL), Intrastromal corneal ring segments (ICRS), and Corneal

The special considerations in surgical management of keratoconus are listed in

Keratoconus typically progresses until the fourth decade, when most but not all, slows or stabilizes [36]. Corneal crosslinking (CXL) has been proposed as a new treatment modality to stop progression of keratoconus since the late 1990s [27]. Currently, CXL is the gold standard and only minimally invasive surgical procedure that halt the progression of keratoconus [27]. The indications for CXL are progressive keratoconus in adults and postoperative ectasia, central corneal thickness more than 400 μm, Kmax 58 D or less [36, 38]. However, the procedure is not approved for stable keratoconus currently. CXL is the promising treatment that can prevent progressive visual loss due to disease evolution and delay invasive surgical procedures such as corneal transplantation. The mechanism of cornea strengthening is a photochemical reaction of corneal collagen by the Riboflavin as a photosensitizer in the photopolymerization process and ultraviolet A irradiation (UVA). The interaction between Riboflavin and UVA can increases the formation of intrafibrillar and interfibrillar carbonyl-based

The standard Dresden protocol was proposed as a treatment option for keratoconus by Wollensak et al. in 2003 [38]. This standard technique is conducted under topical anesthesia. The central corneal epithelium is removed followed by application of 0.1% riboflavin solution (0.1% riboflavin in 2o% dextran solution) as a photosensitizer every 5 minutes for 30 minutes. Then the cornea is exposed

riboflavin solution is re-applied every 5 minutes. After the treatment, topical antibiotics eye drops are applied and bandage contact lens placed upon the eye [38]. Although this standard protocol has been proven to be an effective procedure to halt keratoconus progression [39], it is a time-consuming procedure, may create patient discomfort and has post-operative complications related to corneal abrasion. The reported complications in association with CXL include corneal haze, corneal infection, corneal edema, and corneal melting. Adverse effects are common but mostly transient and of low clinical significance [40]. However, anterior corneal stromal haze is a typical postoperative finding that often occurs in the first month after treatment and typically resolves after 12 to 20 weeks [41]. The posterior aspect of this haze is an indistinct hyperreflective demarcation line seen in the mid stroma that represents the depth of CXL [37]. Two trends have emerged to modify the standard Dresden protocol. The first is a tendency to shorten treatment times [42]. Alternative treatment protocols with different formulations of riboflavin solution

or 5.4 J/cm2

, during which time

transplantation to restore vision and/or stabilize progression of diseases.

delay the need for keratoplasty. Moreover, contact lens in keratoconus patient also have a role in correcting residual refractive error after Corneal collagen cross-linking (CXL), after Intrastromal corneal ring segments (ICRS) or postkeratoplasty [31].
