Ultrasound biomicroscopy and LENSTAR interferometry of lens and IOL position before and after cataract surgery

Session Details

Session Title: Imaging

Session Date/Time: Tuesday 16/09/2014 | 08:00-10:30

Paper Time: 08:41

Venue: Capital Hall B

First Author: : P.Fedor USA

Co Author(s): :    A. Fedor   D. Fedor           

Abstract Details

Purpose:

To evaluate the quantitative biometry of the anterior segment and the position of the lens/IOL in myopic and hyperopic patients before and after cataract surgery using ultrasound biomicroscopy (UBM) and Lenstar interferometry. Effective lens position (ELP) is one of the most important variables and currently the most important source of error in prediction of refractive outcome after cataract surgery. Ciliary body is the structure holding the capsular bag and IOL, thus it is likely to influence the position of the IOL. A new system of quantitative analysis of the anterior segment was developed to describe the anterior segment anatomy. Measurements obtained from UBM were compared with established standard measurements of immersion ultrasound (IMM) and Lenstar interferometry (LS).

Setting:

Referral based private practice with four locations.

Methods:

This is a retrospective non-randomized study comprising 46 eyes. Inclusion criteria were patients with UBM exams before and after cataract surgery of sufficient quality for quantitative analysis. Single frames chosen from video recording had to include images of both ciliary bodies, cornea and anterior chamber structures. A new system of quantitative analysis of the anterior segment was developed to describe the anterior segment anatomy. Ciliary body depth (CBD) was defined as the distance of apex-to-apex line to anterior corneal vertex. Several other landmarks were defined to quantitatively analyze the anterior segment. Measurements obtained from ultrasound biomicroscopy were compared with standard measurements obtained by immersion ultrasound (IMM) and Lenstar interferometry (LS). Group with axial length of less than 23.5 mm was compared with eyes with axial length of more than 23.5 mm, as well as a subgroup of short eyes with axial length of less than 22.00 mm.

Results:

Twenty three eyes obtained Lenstar anterior chamber (AC) measurements preoperatively as well as immersion ultrasound A-scan and UBM. The Lenstar AC was 2.78 +/-0.49 mm, the IMM-AC was 2.94 +/-0.52 mm, with a correlation coefficient of 0.96. The UBM-AC was 2.97 +/-0.52 mm with a correlation coefficient of 0.97 with a Lenstar AC. In a group with axial length of less than 23.5 mm the preoperative AC measured with UBM was 2.81 +/-0.4 mm and AC measured with IMM was 2.76 +/-0.4 mm. In a group with axial length of more than 23.5 mm the preoperative AC measured with UBM was 3.55 +/-0.47 mm and AC measured with IMM was 3.47 +/-0.39 mm. In hyperopic group the preoperative CBD was 4.33 +/-0.23 mm and postoperative CBD was 4.70 +/-0.21. In myopic group the preoperative CBD was 4.91 +/-0.4 mm and postoperative CBD was 5.15 +/-0.43 mm. The posterior shift of CBD in hyperopic group was 0.37 +/-0.2 mm as compared to 0.24 +/-0.19 mm in myopic group. In the subgroup of 9 patients with high hyperopia the preoperative CBD was 4.34 +/-0.15 mm and postoperative CBD was 4.78 +/- 0.19 mm. The posterior shift of CBD was 0.43 +/-0.2 mm.

Conclusions:

In summary we confirm that UBM with new technique is suitable for quantitative analysis of the anterior segment. It has good correlation of the preoperative ACD and LT with immersion ultrasound and Lenstar values, with correlation coefficients in the range of 0.96 - 0.98. The Lenstar measurement of ACD and LT (although not AL) are approximately 0.15 mm shorter as compared to both immersion and UBM measurements. The exact reason for this systematic disparity is unknown. Our study shows with direct imaging of the ciliary body that the apex of the ciliary body moves posterior after cataract surgery and this effect is more pronounced in hyperopic/shorter as compared to myopic/longer eyes. The true measured position of the intraocular lens is compared to the predicted IOL position by standard IOL calculation formulas as well to the formula by Olsen derived from Lenstar measurements of the anterior chamber and the lens thickness. Biomechanics of the intraocular lens is analyzed as well as the detailed anatomy of anterior segment in specific cases. A new system of quantitative analysis of the anterior segment is described.

Financial Interest:

NONE