**3. Investigation of clear corneal incision using SD-OCT**

with previous findings regarding the positive correlation between age and lens capsule or

With the help of anterior segment SD-OCT, researchers also can obtain more detailed useful information regarding accommodation, presbyopia, Fuchs' heterochromic iridocyclitis (**Figure 3**), posterior capsule opacification, and pseudoexfoliation syndrome [10–13]. Moreover, with the OCT technology development, the respective measurement of anterior capsule, posterior capsule and epithelium layer thickness, even plotting corresponding

In summary, anterior segment SD-OCT can be used to visualize anterior and posterior lens capsule, lens epithelium, keratic precipitates, iris stroma atrophy. The use of anterior segment SD-OCT will enable us to better investigate changes in lens structure of patients with Fuchs'

**Figure 3.** Color images and optical coherence tomography cross-sectional images of a 60-year-old female with Fuchs' heterochromic iridocyclitis. The anterior color slit-lamp photos and corresponding anterior segment OCT crosssectional images show atrophy of the iris stroma (panel A, A′), small keratic precipitates scattered over the entire corneal

endothelium (panel B, B′), and plaque of posterior subcapsular opacity (panel C, C′).

topography in specific regions will be available in the future.

heterochromic iridocyclitis or other lens related conditions.

total lens thickness [8, 9].

178 OCT - Applications in Ophthalmology

**2.1. Summary**

In most industrialized countries, cataract surgery accounts for the largest proportion of surgical interventions in ophthalmology. The advent of minimal incision, phacoemulsification (introduced by Charles Kelman in the 1970s), and foldable intraocular lens, has made cataract surgery safer and more efficient [14]. Moreover, modern cataract surgery combined with new generation intraocular lens types, which can be designated refractive surgery, aims to provide optimal visual quality and render the visual function better [15]. As a significant part of the cataract surgery, the constructional architecture of proper clear corneal incisions (CCIs) is vital for a perfect outcome of phacoemulsification. Faulty CCI construction can lead to complications, such as wound leak, Descemet's membrane detachment, and excessive surgicallyinduced astigmatism, and is a situation every cataract surgeon attempts to avoid. However, it is not easy to predictably construct perfect manual single-plane, two-plane, or three-plane clear corneal tunnels using steel or diamond blades [16]. With the higher expectations of patients from modern cataract and refractive surgery and the advent of trifocal and accommodating IOLs, femtosecond laser was introduced into cataract surgery by Zoltan Nagy in 2009 [17]. Previous studies demonstrated that a femtosecond laser-assisted cataract surgery technique could provide repeatable, predictable clear corneal incisions, perfect capsulotomies, and safe nuclear fragmentation [18, 19]. Therefore, CCIs created using femtosecond laser have the advantage of predictable configuration and dimensions.

Clinical manual CCI parameters (incision location, angle of incision, incision length) and features (posterior wound gape, Descemet's membrane detachment, posterior wound retraction, loss of coaptation along the CCI tunnel) in the early postoperative period (up to 1 month) of standard cataract surgery have been reported [20–23]. Based on the above-mentioned studies, we evaluated the quantitative CCI parameters and features in subjects who underwent femtosecond laser-assisted cataract surgery [24]. Except for no sign of loss of coaptation along the CCI tunnel, all the other three CCI features were found in femtosecond laser CCI (**Figure 4**).

As expected, the femtosecond laser lens fragmentation ensures that the phacoemulsification energy (Femto group: 16 ± 13%; manual group: 20 ± 5%) and effective phacoemulsification time (Femto group: 17 ± 9 s; manual group: 32 ± 13 s) were dramatically lower in the Femto group than in the conventional manual group. Moreover, the femtosecond laser group had a lower incidence of Descemet's membrane detachment and posterior wound gape at each follow-up time-point. However, a higher incidence of posterior wound retraction was found in the femtosecond laser group.

Descemet's membrane detachment may potentially hinder the local endothelium pump mechanism and affect corneal wound healing. The routine procedure for CCI by femtosecond laser is from the anterior chamber (inner cornea) to the epithelium (outer cornea), which makes the Descemet's membrane detachment an unusual complication for this group. However, phacoemulsification probe manipulation through the CCI, the blunt dissection of the tunnel, and incision hydration probably contributed to the occurrence of Descemet's membrane detachment in the femtosecond group. For the difference in posterior wound gape incidence, we are inclined to implicate the difference in tunnel incision geometry between the two groups. Compared to 1-plane manual CCI, we mainly used a 2-plane CCI in femtosecond group. As previous studies have mentioned, a 2-plane CCI with a partial lamellar cut positioned parallel to the collagen lamellae may improve the shearing force effects of the stromal collagen lamellae across the entire depth of the cornea [25–27]. Posterior wound retraction, defined as an abrupt step-off or recession of the central edge of the posterior wound surface, was not observed in manual group in this study. This may be attributed to the relatively high incidence of posterior wound gape, in which the posterior wound margins were still separated. A high incidence of posterior wound retraction in the femtosecond group may indicate remodeling of the CCI resulting from endothelial cell necrosis, molecular dissociation, and biomechanical and thermal changes from the femtosecond laser [28]. A previous study, using transmission electron microscopy confirmed the difference between femtosecond laser corneal flap formation (necrotic keratocytes) and microkeratome corneal flap formation (keratocyte apoptosis), which may potentially explain the different incidence of posterior wound retraction in this study [29]. Moreover, the above-mentioned three CCI features may cause changes to posterior corneal curvature, corneal astigmatism, and total corneal power; these should be evaluated in future studies.

and comparison of surgical induced astigmatism and corneal remodeling by different surgical technology. In the future, clear corneal incision length, inner and outer corneal incision thickness, even the lens capsulotomy margin may be evaluated in traditional and femtosec-

OCT Application Before and After Cataract Surgery http://dx.doi.org/10.5772/intechopen.77281 181

Capsular block syndrome (CBS), as an uncommon complication of phacoemulsification, is characterized by the accumulation of liquid between the IOL and posterior capsule [30]. Davison and Holtz first described this syndrome in 1990 and 1992, respectively [31, 32]. In

**Figure 5.** Slit lamp, Pentacam Scheimpflug, and AS-OCT images of an ultra-late capsular block syndrome before (panels A–D) and after surgery (panels E and F). Slit lamp photograph shows white proliferation tissue infero-nasally and nasal tight adhesion of anterior capsule opening fibrosis and IOL (panel A). Scheimpflug-based photography showing the contour of the IOL and the underlying milky-white fluid (panel B). Slit lamp photograph showing a large amount of white fluid trapped behind the IOL (panel C). AS-OCT showing a transparent IOL and accumulation of a milky-white liquefied substance between the posterior capsular bag and IOL (panel D). Slit lamp photograph showing posterior capsular folds and no milky-white liquid after surgery (panel E). AS-OCT shows that the capsular block syndrome is resolved after surgery, with parts of posterior capsule in contact with IOL and posterior capsule folds (panel F).

**4. Capsular block syndrome evaluation before and after treatment** 

ond laser-assisted cataract surgery using OCT.

**using SD-OCT**

#### **3.1. Summary**

Anterior segment SD-OCT can highlight CCIs findings that are not as obvious by UBM, slit lamp. The ability to detect detailed postoperative corneal incision changes of standard or femtosecond laser-assisted cataract surgery is clinically important as it allows for the evaluation

**Figure 4.** High-resolution anterior segment SD-OCT clear corneal incision images of femtosecond laser-assisted cataract surgery showing a 1-plane CCI (panel A), 2-plane CCI (panel B), 3-plane CCI (panel C), stripping of Descemet's membrane (panel D), posterior wound gape (panel E), and posterior wound retraction (panel F).

and comparison of surgical induced astigmatism and corneal remodeling by different surgical technology. In the future, clear corneal incision length, inner and outer corneal incision thickness, even the lens capsulotomy margin may be evaluated in traditional and femtosecond laser-assisted cataract surgery using OCT.
