Eye Model and Its Application - Computational Biomechanics of the Musculoskeletal System - page 272

as boxing (Bianco et al., 2005), tennis (Nadeem et al., 2007), and diving (Chorich et al., 1998; Xu
et al., 2006). In addition, the eye is also susceptible to blunt trauma when impacting an airbag in
vehicle collisions (Kuhn et al., 1995; Manche et al., 1997).
Experimental testing of eye impact by a standardized projectile (a BB with a diameter of
4.5 mm and a mass of 0.375 g) is an effective approach to study blunt ocular trauma. Using
high-speed cameras, previous studies have been conducted on human or animal eyes to inves-
tigate various ocular blunt traumas (Delori et al., 1969; Scott et al., 2000; Pahk and Adelman,
2009; Sponsel et al., 2011). Although high-speed cameras can record deformation and displace-
ment of the globe and the projectile object, in vivo imaging of the inner structures of the eye
is still unavailable. Compared to experimental methods, numerical simulation not only allows
various mechanical conditions and parametric tests to be performed but also provides quanti-
tative analysis. Various ocular injuries have been previously investigated using the finite ele-
ment method. Uchio et al. (1999) developed the first dynamic eye model to study mechanical
conditions for intraocular foreign body (IOFB) injury. Later, a more sophisticated eye model
named the Virginia Tech eye model (VTEM) was introduced by Stitzel et al. (2002). The VTEM
was empirically validated to predict globe rupture at a stress of 23 MPa in the corneoscleral
shell. Other simulation studies related to traumatic ocular injuries investigated optic nerve dam-
age (Cirovic et al., 2006), corneal rupture after photorefractive keratectomy (PRK) and laser-
assisted in situ keratomileusis (LASIK) (Mousavi et al., 2012), retinal detachment (Hans et al.,
2009; Rangarajan et al., 2009), and retinal damage (Rossi et al., 2011). Previous studies have
confirmed that the finite element method is an effective tool to analyze various ocular injuries
under different impact conditions.

21.2 develoPment oF the FInIte element eye model
The human eye is roughly spherical in shape and about 24 mm in diameter. Several structures
compose the human eye. Among the most important anatomical components are the cornea, sclera,
crystalline lens, ciliary, zonules, iris, optic nerve, choroid, retina, and the vitreous and aqueous
humors (Figure 21.1).

Aqueous

Cornea

Lens

Zonules

Iris

Sclera

Ciliary

Retina

Choroid

Vitreous

Optic nerve

FIgure 21.1 (See color insert.) Ocular structure: cornea, sclera, iris, ciliary body, zonules, lens, optic
nerve, retina, choroid, and vitreous and aqueous humors.