**5. Treatment**

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


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

**41**

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

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

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

• nipple cone: small, paracentral, steeper located inferiorly or inferonasally

• globus cone: overall steeper cornea, involves more than three forth of the

The three essential parameters in contact lens fitting are power, diameter, and

• Power: Low minus for mild keratoconus, high minus for severe keratoconus

• Base curve: Flatter base curve for mild keratoconus, steeper base curve for

• Diameter: Based on the cone location, its size and steepness, nipple has a small diameter, usually start with a small diameter such as 8.7 mm, oval cone needs larger diameter lens, globus cone or severe apical displacement need large

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

• oval cone: inferiorly or inferotemporally steeper cornea

**5.1 Nonsurgical treatment**

changes [31].

the following [33].

cornea up to limbus

base curve of contact lens.

severe keratoconus

diameter contact lens.
