Abstract

P 236

Evaluation of vertical and horizontal ciliary sulcus diameter using ultrasound biomicroscopy

Julia Lasseck1, Laura Bredow1, Daniel Böhringer1, Enrique Pfeiffer2, Thomas Reinhard1
1Universitäts-Augenklinik FreiburgM; 2Sonomed, Inc, Barcelona, Espain

Objective
Phakic posterior intraocular lenses (pIOL) are a good alternative to corneal refractive surgery and are gaining popularity in the treatment of high myopia. Accurate pIOL sizing is important to minimize the risk of cataract and other complications. However, it is not easy to precisely measure the ciliary sulcus diameter. Horizontal white-to-white (WTW) measurement is a method to estimate the ciliary sulcus diameter. However, discussion around correlation between WTW distance and ciliary sulcus diameter is controversial. We therefore measured the vertical and horizontal ciliary sulcus diameter using ultrasound biomicroscopy (UBM) and evaluated correlations between these and other ocular measurements.
Methods
The vertical and horizontal ciliary sulcus diameters were measured using 35 MHz VuMax UBM (Sonomed) in emmetropic and myopic eyes (each n=8). Other ocular measurements (e.g. WTW, spherical equivalent (SE), anterior chamber depth, corneal curvature) were obtained using Orbscan II and Carl Zeiss IOL-Master. Using a paired t-test the correlation between vertical to horizontal sulcus diameter was analysed. Linear regression analysis was used to evaluate the correlation between vertical/ horizontal ciliary sulcus diameter and WTW or SE.
Results
In 15 from 16 eyes, vertical sulcus diameters were greater than horizontal diameters. In our cohort, the mean sulcus diameter (mean ± SD) was vertical 12,27 ± 0,38 mm, horizontal 12,02 ± 0,35 mm. The mean of the differences (vertical minus horizontal) was in the emmetropic eyes greater (0,27 mm, p<0,05) than in the myopic eyes (0,23 mm, p<0,02). No statistically significant correlation was found between the sulcus diameter and the SE. The coefficient of correlation between WTW (Orbscan) and horizontal sulcus was 0,71 (p<0,01), between WTW and vertical sulcus 0,46 (p=0,18).
Conclusions
Sulcus diameters can be most precisely measured with the UBM. The ciliary sulcus appears to have a vertically oval shape. This should be considered by surgeons to increase the safety and accuracy of pIOL sizing and to reach rotational stability. 

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