**5. IOL power calculation in post-myopic excimer laser eyes using SD-OCT**

**6. Conclusions**

**Grant information**

**Financial interests**

tioned in this paper.

**Author details**

Xiaogang Wang1

PR China

**References**

\*, Jing Dong2

\*Address all correspondence to: movie6521@163.com

age. Acta Ophthalmologica. 1974;**52**:688-706

Archives of Ophthalmology. 2001;**119**:1179-1185

1 Department of Cataract, Shanxi Eye Hospital, Taiyuan, China

No. 81501544.

In conclusion, OCT, as a noninvasive and high-resolution imaging technology, can provide the ophthalmologist with clinically useful findings not only about the retina, but also for the cornea, lens, and anterior chamber. Anterior segment high-speed SD-OCT system offers efficient information about lens capsule evaluation, clear corneal incision investigation, capsular block syndrome management, and post-refractive surgery IOL power calculation. In the future, anterior segment SD-OCT may be a useful tool for detecting and monitoring more

OCT Application Before and After Cataract Surgery http://dx.doi.org/10.5772/intechopen.77281 185

This work was supported by the National Natural Science Foundation of China under Grant

The authors have neither a conflict of interest nor commercial interest in the equipment men-

2 Department of Ophthalmology, The First Hospital of Shanxi Medical University, Shanxi,

[1] Huang D, Swanson EA, Lin CP, Schuman JS, Stinson WG, Chang W, Hee MR, Flotte T, Gregory K, Puliafito CA, et al. Optical coherence tomography. Science. 1991;**254**:1178-1181

[2] Seland JH. Ultrastructural changes in the normal human lens capsule from birth to old

[3] Radhakrishnan S, Rollins AM, Roth JE, Yazdanfar S, Westphal V, Bardenstein DS, Izatt JA. Real-time optical coherence tomography of the anterior segment at 1310 nm.

and Bin Sun1

, Suhua Zhang1

ocular disease progression and treatment response in clinic.

It is well known that correct IOL power calculation in patients undergoing cataract surgery depends mainly on the accurate measurement of corneal power, axial length, corneal keratometry, and the effective lens position after surgery [44, 45]. Due to index of refraction error, instrument error, and IOL formula error, precise prediction of IOL power is always a big challenge for cataract surgery in patients with previous corneal refractive surgery (PRK, LASIK, RK) [46–51]. For post corneal refractive surgery cataract patients, both, patient expectations of spectacle independence and reduction in the accuracy of conventional IOL power calculation formulas due to previous corneal surgery should be considered. To deal with these issues, many innovative post-corneal refractive surgery IOL power calculation formulas have been developed [52–58]. Compared to traditional keratometry, RTVue spectral-domain AS-OCT can measure anterior and posterior corneal curvature and then calculate the net corneal power, which in conjunction with IOLMaster biometry data (AL, ACD) provides the IOL power [59]. Previous studies have demonstrated that Fourier-domain AS-OCT can provide highly repeatable corneal power measurement and spectral-domain OCT-based IOL formulas have also provided promising results in post-refractive surgery IOL calculation in eyes undergoing cataract surgery; this is especially meaningful for patients for whom prior data are not available [59–61]. To avoid significant IOL power fluctuation between different formulas, surgeons can also use ASCRS online post-refractive IOL calculator (link: http://iolcalc. ascrs.org/) to get the average IOL power value to make sure the real postoperative refraction deviation from the target refraction is not large (**Figure 8**).

#### **5.1. Summary**

Anterior segment SD-OCT can noncontactly provide true net corneal power, which is essential for IOL power calculation after excimer laser corneal surgery. The SD-OCT-based IOL formulas enable to provide promising results in post-refractive surgery IOL calculation, especially meaningful for eyes whose prior data unavailable.


**Figure 8.** Average IOL power information for all available formulas using ASCRS online post-refractive IOL calculator.
