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Abstract
Purpose
To evaluate the changes and characteristics of the anterior segment of the eye after laser peripheral iridotomy (LPI) conducted on patients with acute angle closure crisis (AACC) for both therapeutic purposes and prophylactic purposes in the fellow eye.
Methods
Anterior segments were examined by topography, laser interferometry, anterior segment optical coherence tomography, anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), angle opening distance (AOD), central corneal thickness (CCT), and axial length as compared to prior procedures in 20 eyes with glaucoma (treatment group) and 20 contralateral eyes (prophylactic group) in 20 patients diagnosed with AACC.
Results
Before laser treatment, there were no significant differences in pre-LPI ACV, ACA, AOD and axial length, although differences in the CCT and ACD existed between the groups. Compared to prior laser treatment at 1 and 3 months after laser treatment, the ACV, ACA, AOD 500, and AOD 750 increased in both groups. When both groups were compared 1 month after their laser treatments, the AOD 750 was increased in the treatment group. There were no significant differences between two groups 3 months post LPI.
Conclusions
Other than changes in the ACD and CCT, no significant differences were observed in the anterior segment characteristics in AACC affected and contralateral eyes prior to LPI. After LPI, the treatment group showed greater changes in their anterior segments; however, the open angle was maintained at 1 month post treatment.
Figures and Tables
 | Figure 1Anterior chamber image of anterior segment optical coherence tomography. (A, B) anterior chamber angle (ACA) means apex in the iris recess (IR) and the arms of the angle passing through a point on the trabecular meshwork (TM) from the scleral spur and the point on the iris perpendicularly opposite, angle opening distance (AOD) 500, 750 means distance between the point which was 500 µm (750 µm) from anterior to the scleral spur (SS) and the iris (perpendicularly opposite point). SC = Schlemm's canal.
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 | Figure 2Changes in anterior segment parameters over time in treatment group and prophylactic group. (A) Angle opening distance 750 µm (AOD 750), (B) anterior chamber angle (ACA) (Confidence interval = 95%). Before laser treatment, there were no significant differences in pre- laser peripheral iridotomy (LPI) AOD 750, ACA between two groups. Compared with prior laser treatment, 1 month and 3 months after laser treatment, the AOD 750 and ACA was increased in both groups. When two groups were compared 1 month after the laser treatment, the change was greater in the treatment group. And no significant differences between two groups after 3 months of LPI.
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 | Figure 3Laser peripheral iridotomy (LPI) in patient with acute angle closure crisis (AACC). Pre-LPI anterior segment optical coherence tomography of a 70-year-old female with AACC on the right eye, showing closed angles (A) and the left eye (B). (C, D) Horizontal section scan showing increased anterior chamber angle and angle opening distance after 1 month from LPI. (E, F) Horizontal section scan after 3 months from LPI.
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Table 1
A comparison of the anterior segment parameters before and after LPI
Values are presented as mean ± SD unless otherwise indicated.
LPI = laser peripheral iridotomy; IOP = intraocular pressure; AXL = axial length; CCT = central corneal thickness; ACV = anterior chamber volume; ACD = anterior chamber depth; ACA = anterior chamber angle; AOD 500 = angle opening distance 500; AOD 750 = angle opening distance 750.
*Mann-Whitney U test (p < 0.05).
Table 2
Significances of anterior chamber changes over time in treatment group and prophylactie group
The above statistic was calculated based on the measurement value of Table 1.
LPI = laser peripheral iridotomy; AXL = axial length; CCT = central corneal thickness; ACV = anterior chamber volume; ACD = anterior chamber depth; ACA = anterior chamber angle; AOD 500 = angle opening distance 500; AOD 750 = angle opening distance 750.
*Wilcoxon signed rank test (p < 0.05).
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