ORIGINAL STUDY
Postiridotomy Ultrasound Biomicroscopy Features in the Fellow Eye of Chinese Patients with Acute Primary AngleClosure and Chronic Primary Angle-Closure Glaucoma Hui-Jin Chen, MD, Xin Wang, MD, Yu-Jie Yan, MD, and Ling-Ling Wu, MD
Purpose: To compare the features of postiridotomy ultrasound biomicroscopy (UBM) in Chinese patients with acute primary angle-closure (aPAC) and with chronic primary angle-closure (cPAC) glaucoma. Patients and Methods: Consecutive cases were classified into acute and chronic groups. The acute group included 77 patients with unilateral aPAC. The chronic group included 57 patients with unilateral advanced cPAC glaucoma. In both the groups, the patients’ fellow eye underwent a laser iridotomy and was studied. The main outcome measures included qualitative UBM parameters such as a plateau iris, anterior iris insertion, and an anteriorly rotated ciliary process and quantitative UBM parameters such as central anterior chamber depth (ACD), basal iris thickness (IT500), and scleral ciliary process angle (SCPA). Results: For the qualitative parameters, more eyes in the chronic group had a plateau iris (P = 0.046), an anterior iris insertion (P = 0.222), and an anteriorly rotated ciliary process (P = 0.090) than those in the acute group. For the quantitative parameters, the eyes in the chronic group had a deeper ACD (P < 0.001), thicker IT500 (P < 0.001), and smaller SCPA (P < 0.001) than those in the acute group. Conclusions: The UBM features of Chinese patients with cPAC include a more plateaued iris, a thicker basal iris, and a smaller SCPA, whereas patients with aPAC may have a shallower ACD. For Chinese patients, a nonpupillary block component may play a more important role in asymptomatic cPAC than in aPAC. Key Words: primary angle closure, ultrasound biomicroscopy, iridotomy
(J Glaucoma 2015;24:233–237)
P
rimary angle-closure (PAC) and primary angle-closure glaucoma (PACG) have a high prevalence in Asia, especially in China.1,2 An acute angle-closure event (acute primary angle closure [aPAC]) and asymptomatic, chronic primary angle closure (cPAC) are 2 clinical presentations within 1 disease spectrum. Because the symptoms of an acute, complete angle closure are so severe and unpleasant that most patients seek immediate treatment, the angle can Received for publication July 2, 2013; accepted June 9, 2014. From the Key Laboratory of Vision Loss and Restoration, Peking University Eye Center, Ministry of Education, Peking University Third Hospital, Beijing, P.R. China. Disclosure: The authors declare no conflict of interest. Reprints: Ling-Ling Wu, MD, Key Laboratory of Vision Loss and Restoration, Peking University Eye Center, Ministry of Education, Peking University Third Hospital, 49# North Garden Road, Haidian District, Beijing 100191, P.R. China (e-mail: wullc@ hotmail.com). Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/IJG.0000000000000086
J Glaucoma
Volume 24, Number 3, March 2015
be mostly or completely reopened in cases that receive prompt and proper management. Fellow eyes with similar anatomic risk factors can also receive preventive treatment in advance. Therefore, most cases can be treated during the PAC or PAC suspect stage. However, on the other side of the spectrum, eyes that have an asymptomatic cPAC usually experience an insidious onset and often have a more severe visual field loss than those eyes with symptomatic aPAC.3 Most cases are treated during the PACG stage in at least 1 eye. Although aPAC and cPAC have some similarities within the same disease spectrum regarding their ocular biometry, subtle differences must exist between them. There are 2 basic mechanisms responsible for PAC: pupillary block and nonpupillary block.1 Laser peripheral iridotomy (LPI) can eliminate a pupillary block and is recognized as a standard first-line intervention for the treatment of PAC(G).4 Although the control of long-term intraocular pressure (IOP) after LPI depends on the disease stage at presentation,5,6 the effectiveness of an LPI in maintaining the angle configuration after aPAC and in preventing angle closure in the fellow eye suggests that a pupillary block is a significant mechanism responsible for aPAC.7–9 However, in our clinical experience, after LPI, cPAC eyes are more likely to have a residual appositional angle closure, as well as progression of peripheral anterior synechia (PAS). It was proposed that Asians are more likely to experience a nonpupillary block mechanism such as plateau iris leading to cPAC.10 So far, a limited number of studies have compared the biometric differences between aPAC and cPAC cases,11–14 and few have investigated the nonpupillary block component in aPAC and cPAC.14 Ultrasound biomicroscopy (UBM) is a useful tool for the investigation of PAC(G), because it is a relatively objective and reproducible examination that can provide cross-sectional images of the width of the chamber angle, the profile of the iris, and the size and position of the ciliary body. Both qualitative and quantitative parameters can be analyzed with UBM.11,12,15 In the current study, in order to compare the anatomic characteristics of the anterior segment, mainly the nonpupillary block component between aPAC and cPAC cases, we focused on those eyes with a patent LPI and compared their UBM features.
PATIENTS AND METHODS Patients The subjects were consecutively enrolled among patients with aPAC and cPAC(G) that were newly diagnosed in our center from January 2010 to February 2011. Written informed consent was obtained from all subjects, and the study protocol was approved by the ethics www.glaucomajournal.com |
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committee of the hospital and was performed according to the tenets of the Declaration of Helsinki. For the acute group, the inclusion criteria included the following: (1) only 1 eye of a patient had a recent onset of aPAC; and (2) the fellow eyes (FaPAC) had never experienced an acute attack and had an occludable angle, but no PAS. For the chronic group, the inclusion criteria included the following: (1) only 1 eye of a patient had advanced cPACG; (2) the fellow eyes (FcPACG) had PAS for 40 mm Hg). (4) No glaucomatous optic neuropathy. Advanced cPACG was defined as: (1) the patient never experienced any symptoms pertaining to acute angle closure such as ocular or periocular pain, nausea, or intermittent blurry vision with halos; (2) an ocular examination showed no signs of a prior acute attack, for example, a mid-dilated pupil, segmental iris atrophy, and glaukomflecken; (3) chronically elevated IOP (>21 mm Hg); (4) gonioscopically confirmed PAS of >180 degrees; and (5) had a typical glaucomatous optic neuropathy. The exclusion criteria included the following: (1) cases with a secondary angle closure, such as uveitis, iris neovascularization, trauma, tumor, or any obvious cataract leading to an intumescent lens; (2) studied eyes had pupil distortion or posterior synechiae; (3) studied eyes had a prior intraocular surgery, except LPI; (4) subjects who were unable to tolerate a gonioscopy or an UBM examination; (5) aPAC cases with a bilateral acute attack; (6) subacute cases with atypical symptoms and signs; (7) FaPAC had PAS; and (8) FcPACG had PAS for >3 cumulative clockhours or extended PAS in the superior quadrant.
Methods A gonioscopic examination was performed and recorded by one of the researchers (L.-L.W.). An occludable angle was defined as the presence of at least 180 degrees of the angle in which the posterior trabecular meshwork was not visible with static gonioscopy. The presence, as well as the extension of PAS, was determined by using a dynamic compression technique with a Goldmann gonioscope (Single Mirror Gonio Lens; Ocular Instruments, Bellevue, WA). An LPI had been performed on all studied eyes. One percent pilocarpine was discontinued for at least 1 week before the UBM examination. UBM was performed in a supine position in a dark room (< 1 lux, measured with an ST-92 luminance meter; Beijing Teachers University Photoelectricity Instrument Factory, Beijing, China) by using a 50-MHz transducer (Paradigm Medical Instruments Inc.,
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Salt Lake City, UT). After a topical anesthesia was applied, an eyecup containing hydroxyethyl cellulose and a physiological saline were placed on the globe and care was taken not to exert pressure on the globe. Variation in accommodation was minimized by utilizing fixation of the contralateral eye on a standard distance target on the ceiling. Each eye was examined in its axial section with a probe kept perpendicular to the corneoscleral surface. All UBM images were analyzed by a single researcher (H.-J.C.). Areas with PAS were avoided during a biometric analysis and measurement. Standard photographs were selected for a qualitative assessment of the parameters including anterior iris insertion, anterior rotation of the ciliary process, and plateau iris (Fig. 1). The definitions of these qualitative parameters were as follows, and an eye was considered to have one of these factors if at least 2 quadrants fulfilled the following criteria: (1) Anterior iris insertion was defined as an iris insertion at the base of the ciliary body near the scleral spur. (2) Anterior rotation of the ciliary process was defined as an anteriorly directed ciliary process that was entirely in contact with the peripheral iris and without a ciliary sulcus. (3) Plateau iris was defined if all of the following points were fulfilled by using the criteria proposed by Kumar and colleagues.16,17 (a) The ciliary process was anteriorly directed and was supporting the peripheral iris, so it was parallel to the trabecular meshwork. (b) The iris root had a steep rise from its point of insertion, followed by a downward angulation to the corneoscleral wall. (c) Presence of a central, flat iris plane. (d) An absent ciliary sulcus. (e) An irido-angle contact (above the level of the scleral spur) in the same quadrant. For the quantitative measurements, the superior quadrant was selected. As illustrated in Figure 2, quantitative UBM parameters including central anterior chamber depth (ACD), basal iris thickness (IT500), and scleral ciliary process angle (SCPA) were measured according to the methods of Pavlin et al18 as follows: (1) The ACD was measured from the corneal endothelium to the anterior lens surface. (2) The IT500 was measured along a line extending from the corneal endothelium and 500 mm from the scleral spur, perpendicularly through the iris. (3) The SCPA was measured between a line that was tangent to the scleral surface and the axis of the ciliary body. UBM pro 2000 software (Paradigm Medical Industries Inc.) was used for the quantitative measurements.
Statistics Analysis All analyses were performed by using the SPSS15.0 statistical software (SPSS Inc., Chicago, IL). For the quantitative parameters, the independent samples t test was used. For the qualitative data, a w2 test was used. A P value of 3 cumulative clock-hours or extended PAS in the superior quadrant, 13]. Finally, 77 eyes from 77 patients were Copyright
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In the current study, in order to investigate typical aPAC and cPAC cases, we used robust inclusion and exclusion criteria to exclude the subacute type of PAC and those cases with an overlap in their clinical presentation, including those with chronic angle-closure glaucoma developed after the resolution of the acute episode and those that had an acute-on-chronic PACG. As we know, the angle configuration and iris profile can be dramatically altered in eyes that are experiencing an acute attack or extensive PAS. However, PAC(G) is a bilateral disease, so patients have a similar anatomic configuration, as well as susceptibility in both the eyes. Therefore, for this study, we chose to analyze FaPAC and FcPACG, neither of which had experienced an acute attack nor had extensive PAS. The UBM results from the present study showed that a plateau iris was much more common in FcPACG (31.6% vs. 16.9%; P = 0.046) than in FaPAC. A plateau iris is a main component of a nonpupillary block mechanism in PACG, in which the angle remains appositionally closed or occludable after LPI.19 Kumar and colleagues found that about one third of eyes had a plateau iris in PAC suspect (32.3%) and PACG (32.4%).16,17 In the other study,14 the authors compared the prevalence of a plateau iris configuration between FaPAC and cPACG eyes in a relatively small group of patients and found no significant difference (37% in 27 FaPAC; 34.6% in 26 PACG eyes) that was different from our results. Several reasons may explain the difference. First, the inclusion and exclusion criteria in this study were stricter. Second, a diagnosis of a plateau iris included “irido-angle contact” in this study. Third, we had a higher patient number in this study. Our findings indicated that more eyes with cPAC(G) may still have an appositional angle closure and an increased risk of gradually developing PAS and may still experience an increase in IOP with an LPI treatment alone than eyes with aPAC. An “incomplete” type of plateau iris syndrome was considered to be more common than the “complete” form of the syndrome.20 With an incomplete plateau iris syndrome, the iris is not as far forward as in the complete syndrome, in the presence of an anteriorly positioned ciliary process and an absent ciliary sulcus. Therefore, in addition
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FIGURE 2. An illustration of the quantitative measurement for the ACD, IT500, and SCPA. A, ACD was measured from the corneal endothelium to the anterior lens surface. B, IT500 was measured along a line extending from the corneal endothelium and 500 mm from the scleral spur, perpendicularly through the iris. SCPA was measured between a line that was tangent to the scleral surface and the axis of the ciliary body. ACD indicates central anterior chamber depth; IT500, basal iris thickness; SCPA, scleral ciliary process angle.
to a “complete” plateau iris, we also analyzed the ciliary process position separately, and we found more eyes in the chronic group (25 of 57 eyes; 43.9%) had an anteriorly rotated ciliary process than those in the acute group (23 of 77 eyes; 29.9%), although the difference was not statistically significant (P = 0.09). As a quantitative UBM parameter, SCPA reflects the position of the ciliary process. Similarly, the FcPACG had a significantly smaller SCPA than the FaPAC in our study (27.32 ± 4.79 vs. 33.01 ± 5.03 degrees; P < 0.001) that demonstrated the ciliary process was more anteriorly rotated in FcPACG than in FaPAC. An anteriorly inserted iris root at the scleral spur was also considered responsible for cPAC.10 We found a higher proportion of an anterior iris insertion in FcPACG (59.65%) than in FaPAC (49.35%), but the difference was not statistically significant (P = 0.222). The present study showed that ACD was markedly shallower in FaPAC (1.802 ± 0.210 vs. 1.994 ± 0.210 mm; P < 0.001) than in FcPACG. This was consistent with the results of the other 2 studies.11,12 The shallower ACD noted in the acute group was likely to predispose an eye to a greater iris-lens contact and thus, pupillary block. Recent studies demonstrated that an increased iris thickness was associated with narrow angles and angle closure.21,22 The UBM results in the present study showed that FcPACG had a markedly thicker basal iris (0.409 ± 0.059 vs. 0.330 ± 0.051 mm; P < 0.001) than FaPAC under a dark condition. However, previous studies found no significant difference in IT500 between eyes TABLE 1. Comparison of Postiridotomy Ultrasound Biomicroscopy Parameters Between 2 Groups
FaPAC (N = 77) ACD (mm) IT500 (mm) SCPA (deg.) Anterior insertion of the iris [n (%)] Plateau iris [n (%)] Anterior rotation of ciliary process [n (%)]
1.802 ± 0.210 0.330 ± 0.051 33.01 ± 5.03 38 (49.35%) 13 (16.88%) 23 (29.87%)
FcPACG (N = 57)
P
1.994 ± 0.210 < 0.001 0.409 ± 0.059 < 0.001 27.32 ± 4.79 < 0.001 34 (59.65%) 0.222 18 (31.58%) 25 (43.86%)
0.046 0.090
ACD indicates anterior chamber depth; FaPAC, fellow eyes of acute primary angle closure; FcPACG, fellow eyes of chronic primary angle-closure glaucoma; IT500, basal iris thickness (measured on a line extending from the corneal endothelium 500 mm from the scleral spur perpendicularly through the iris); SCPA, scleral ciliary process angle.
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experiencing cPAC and aPAC with light-conditioned UBM.11,12 Use of a different illumination during a UBM examination may be one reason for this discrepancy. Another reason may be pharmaceutical influence on iris thickness. In our study, pilocarpine was discontinued in all eyes at least 1 week before the examination. There were some limitations in the current study. As previously mentioned, we focused only on the 2 ends of the PAC(G) spectrum; however, there were some cases with an overlapping clinical presentation that existed in the middle of the spectrum that were not studied here. For a qualitative assessment, by using a uniform definition for the parameters and standard photographs, we created a dichotomous classification of the parameters including anterior iris insertion, anterior rotation of the ciliary process, and plateau iris. However, there may be a range of appearances with UBM, and some mild cases were not diagnosed according to the criteria in our study. This was a potential source of bias. In the quantitative study, all 4 quadrants were not studied. As the superior quadrant is most susceptible to angle closure, the superior quadrant was selected for the quantitative measurement. Moreover, according to the inclusion criteria of the 2 study groups, the FaPAC did not have PAS, but the FcPACG had limited PAS that should be avoided while interpreting UBM images; therefore, the person who interpreted the images was aware of the clinical diagnosis. This was also a potential source of bias. Another potential weakness that should be mentioned here was the use of a Goldmann lens to perform indentation gonioscopy. Because of the depth of the central “well” of the lens, a Goldmann lens would not likely be as effective at indenting the central cornea or opening the peripheral angle as a flatter “Zeiss” type lens would and it was likely that we overestimated the extent of PAS in some patients. Finally, the lens position and thickness,23 as well as a new parameter, the lens vault,24 defined as the perpendicular distance between the anterior pole of the crystalline lens and a horizontal line joining the 2 scleral spurs, were also important factors contributing to angle closure. However, the lens parameters could not be well investigated with UBM and were not included in this study. The concept that a nonpupillary block component may play a more important role in the chronic type than in the acute type of PAC(G) has been widely accepted. However, a theoretical basis for this concept is limited.14 In our study, we analyzed most of the parameters related to a nonpupillary block mechanism including plateau iris,
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Volume 24, Number 3, March 2015
anterior inserted iris, anteriorly rotated ciliary process, and IT500. Besides, by just analyzing the fellow eyes in both the groups, we did not measure the areas that had a dramatic angle alteration that resulted from an acute attack or extensive angle synechia; therefore, this made our study results more reliable. Our study suggests that with a different clinical presentation and natural disease course, some variations exist regarding the anatomic configurations between aPAC and asymptomatic cPAC in Chinese patients. Accordingly, we should treat aPAC and cPAC separately, rather than combining them in clinical practice and research. Also, we believe further refinement of the current classification systems (such as including the symptoms and signs of an acute attack as a defining feature of an angle closure) is advisable. REFERENCES 1. Wang N, Wu H, Fan Z. Primary angle closure glaucoma in Chinese and Western populations. Chin Med J (Engl). 2002; 115:1706–1715. 2. Foster PJ, Johnson GJ. Glaucoma in China: how big is the problem? Br J Ophthalmol. 2001;85:1277–1282. 3. Ang LP, Aung T, Chua WH, et al. Visual field loss from primary angle-closure glaucoma: a comparative study of symptomatic and asymptomatic disease. Ophthalmology. 2004; 111:1636–1640. 4. American Academy of Ophthalmology. Laser peripheral iridotomy for pupillary-block glaucoma. Ophthalmology. 1994; 101:1749–1758. 5. Aung T, Ang LP, Chan SP, et al. Acute primary angle-closure: long-term intraocular pressure outcome in Asian eyes. Am J Ophthalmol. 2001;131:7–12. 6. Aung T, Friedman DS, Chew PT, et al. Long-term outcomes in Asians after acute primary angle closure. Ophthalmology. 2004; 111:1464–1469. 7. Lim LS, Aung T, Husain R, et al. Acute primary angle closure: configuration of the drainage angle in the first year after laser peripheral iridotomy. Ophthalmology. 2004;111:1470–1474. 8. Friedman DS, Chew PT, Gazzard G, et al. Long-term outcomes in fellow eyes after acute primary angle closure in the contralateral eye. Ophthalmology. 2006;113:1087–1091. 9. Ang LP, Aung T, Chew PT. Acute primary angle closure in an Asian population: long-term outcome of the fellow eye after prophylactic laser peripheral iridotomy. Ophthalmology. 2000; 107:2092–2096.
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Comparison of UBM Features Between aPAC and cPAC in Chinese
10. Salmon JF. Predisposing factors for chronic angle-closure glaucoma. Prog Retin Eye Res. 1999;18:121–132. 11. Marchini G, Pagliarusco A, Toscano A, et al. Ultrasound biomicroscopic and conventional ultrasonographic study of ocular dimensions in primary angle-closure glaucoma. Ophthalmology. 1998;105:2091–2098. 12. Sihota R, Dada T, Gupta R, et al. Ultrasound biomicroscopy in the subtypes of primary angle closure glaucoma. J Glaucoma. 2005;14:387–391. 13. Sihota R, Lakshmaiah NC, Agarwal HC, et al. Ocular parameters in the subgroups of angle closure glaucoma. Clin Experiment Ophthalmol. 2000;28:253–258. 14. Mochizuki H, Takenaka J, Sugimoto Y, et al. Comparison of the prevalence of plateau iris configurations between angleclosure glaucoma and open-angle glaucoma using ultrasound biomicroscopy. J Glaucoma. 2011;20:315–318. 15. Jiang Y, He M, Huang W, et al. Qualitative assessment of ultrasound biomicroscopic images using standard photographs: the liwan eye study. Invest Ophthalmol Vis Sci. 2010;51: 2035–2042. 16. Kumar RS, Baskaran M, Chew PT, et al. Prevalence of plateau iris in primary angle closure suspects an ultrasound biomicroscopy study. Ophthalmology. 2008;115:430–434. 17. Kumar RS, Tantisevi V, Wong MH, et al. Plateau iris in Asian subjects with primary angle closure glaucoma. Arch Ophthalmol. 2009;127:1269–1272. 18. Pavlin CJ, Harasiewicz K, Foster FS. Ultrasound biomicroscopy of anterior segment structures in normal and glaucomatous eyes. Am J Ophthalmol. 1992;113:381–389. 19. Pavlin CJ, Ritch R, Foster FS. Ultrasound biomicroscopy in plateau iris syndrome. Am J Ophthalmol. 1992;113: 390–395. 20. Robert LS, Marc FL, Michael VD. Primary angle-closure glaucoma. In: Stamper RL, Lieberman MF, Drake MV, eds. Becker-Shaffer’s Diagnosis and Therapy of the Glaucomas. Philadelphia: Mosby Elsevier Inc; 2009:204–206. 21. Wang BS, Narayanaswamy A, Amerasinghe N, et al. Increased iris thickness and association with primary angle closure glaucoma. Br J Ophthalmol. 2011;95:46–50. 22. Wang B, Sakata LM, Friedman DS, et al. Quantitative iris parameters and association with narrow angles. Ophthalmology. 2010;117:11–17. 23. Tarongoy P, Ho CL, Walton DS. Angle-closure glaucoma: the role of the lens in the pathogenesis, prevention, and treatment. Surv Ophthalmol. 2009;54:211–225. 24. Nongpiur ME, He M, Amerasinghe N, et al. Lens vault, thickness, and position in Chinese subjects with angle closure. Ophthalmology. 2011;118:474–479.
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Postiridotomy Ultrasound Biomicroscopy Features in the Fellow Eye of Chinese Patients with Acute Primary AngleClosure and Chronic Primary Angle-Closure Glaucoma Hui-Jin Chen, MD, Xin Wang, MD, Yu-Jie Yan, MD, and Ling-Ling Wu, MD
Purpose: To compare the features of postiridotomy ultrasound biomicroscopy (UBM) in Chinese patients with acute primary angle-closure (aPAC) and with chronic primary angle-closure (cPAC) glaucoma. Patients and Methods: Consecutive cases were classified into acute and chronic groups. The acute group included 77 patients with unilateral aPAC. The chronic group included 57 patients with unilateral advanced cPAC glaucoma. In both the groups, the patients’ fellow eye underwent a laser iridotomy and was studied. The main outcome measures included qualitative UBM parameters such as a plateau iris, anterior iris insertion, and an anteriorly rotated ciliary process and quantitative UBM parameters such as central anterior chamber depth (ACD), basal iris thickness (IT500), and scleral ciliary process angle (SCPA). Results: For the qualitative parameters, more eyes in the chronic group had a plateau iris (P = 0.046), an anterior iris insertion (P = 0.222), and an anteriorly rotated ciliary process (P = 0.090) than those in the acute group. For the quantitative parameters, the eyes in the chronic group had a deeper ACD (P < 0.001), thicker IT500 (P < 0.001), and smaller SCPA (P < 0.001) than those in the acute group. Conclusions: The UBM features of Chinese patients with cPAC include a more plateaued iris, a thicker basal iris, and a smaller SCPA, whereas patients with aPAC may have a shallower ACD. For Chinese patients, a nonpupillary block component may play a more important role in asymptomatic cPAC than in aPAC. Key Words: primary angle closure, ultrasound biomicroscopy, iridotomy
(J Glaucoma 2015;24:233–237)
P
rimary angle-closure (PAC) and primary angle-closure glaucoma (PACG) have a high prevalence in Asia, especially in China.1,2 An acute angle-closure event (acute primary angle closure [aPAC]) and asymptomatic, chronic primary angle closure (cPAC) are 2 clinical presentations within 1 disease spectrum. Because the symptoms of an acute, complete angle closure are so severe and unpleasant that most patients seek immediate treatment, the angle can Received for publication July 2, 2013; accepted June 9, 2014. From the Key Laboratory of Vision Loss and Restoration, Peking University Eye Center, Ministry of Education, Peking University Third Hospital, Beijing, P.R. China. Disclosure: The authors declare no conflict of interest. Reprints: Ling-Ling Wu, MD, Key Laboratory of Vision Loss and Restoration, Peking University Eye Center, Ministry of Education, Peking University Third Hospital, 49# North Garden Road, Haidian District, Beijing 100191, P.R. China (e-mail: wullc@ hotmail.com). Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved. DOI: 10.1097/IJG.0000000000000086
J Glaucoma
Volume 24, Number 3, March 2015
be mostly or completely reopened in cases that receive prompt and proper management. Fellow eyes with similar anatomic risk factors can also receive preventive treatment in advance. Therefore, most cases can be treated during the PAC or PAC suspect stage. However, on the other side of the spectrum, eyes that have an asymptomatic cPAC usually experience an insidious onset and often have a more severe visual field loss than those eyes with symptomatic aPAC.3 Most cases are treated during the PACG stage in at least 1 eye. Although aPAC and cPAC have some similarities within the same disease spectrum regarding their ocular biometry, subtle differences must exist between them. There are 2 basic mechanisms responsible for PAC: pupillary block and nonpupillary block.1 Laser peripheral iridotomy (LPI) can eliminate a pupillary block and is recognized as a standard first-line intervention for the treatment of PAC(G).4 Although the control of long-term intraocular pressure (IOP) after LPI depends on the disease stage at presentation,5,6 the effectiveness of an LPI in maintaining the angle configuration after aPAC and in preventing angle closure in the fellow eye suggests that a pupillary block is a significant mechanism responsible for aPAC.7–9 However, in our clinical experience, after LPI, cPAC eyes are more likely to have a residual appositional angle closure, as well as progression of peripheral anterior synechia (PAS). It was proposed that Asians are more likely to experience a nonpupillary block mechanism such as plateau iris leading to cPAC.10 So far, a limited number of studies have compared the biometric differences between aPAC and cPAC cases,11–14 and few have investigated the nonpupillary block component in aPAC and cPAC.14 Ultrasound biomicroscopy (UBM) is a useful tool for the investigation of PAC(G), because it is a relatively objective and reproducible examination that can provide cross-sectional images of the width of the chamber angle, the profile of the iris, and the size and position of the ciliary body. Both qualitative and quantitative parameters can be analyzed with UBM.11,12,15 In the current study, in order to compare the anatomic characteristics of the anterior segment, mainly the nonpupillary block component between aPAC and cPAC cases, we focused on those eyes with a patent LPI and compared their UBM features.
PATIENTS AND METHODS Patients The subjects were consecutively enrolled among patients with aPAC and cPAC(G) that were newly diagnosed in our center from January 2010 to February 2011. Written informed consent was obtained from all subjects, and the study protocol was approved by the ethics www.glaucomajournal.com |
233
Chen et al
J Glaucoma
committee of the hospital and was performed according to the tenets of the Declaration of Helsinki. For the acute group, the inclusion criteria included the following: (1) only 1 eye of a patient had a recent onset of aPAC; and (2) the fellow eyes (FaPAC) had never experienced an acute attack and had an occludable angle, but no PAS. For the chronic group, the inclusion criteria included the following: (1) only 1 eye of a patient had advanced cPACG; (2) the fellow eyes (FcPACG) had PAS for 40 mm Hg). (4) No glaucomatous optic neuropathy. Advanced cPACG was defined as: (1) the patient never experienced any symptoms pertaining to acute angle closure such as ocular or periocular pain, nausea, or intermittent blurry vision with halos; (2) an ocular examination showed no signs of a prior acute attack, for example, a mid-dilated pupil, segmental iris atrophy, and glaukomflecken; (3) chronically elevated IOP (>21 mm Hg); (4) gonioscopically confirmed PAS of >180 degrees; and (5) had a typical glaucomatous optic neuropathy. The exclusion criteria included the following: (1) cases with a secondary angle closure, such as uveitis, iris neovascularization, trauma, tumor, or any obvious cataract leading to an intumescent lens; (2) studied eyes had pupil distortion or posterior synechiae; (3) studied eyes had a prior intraocular surgery, except LPI; (4) subjects who were unable to tolerate a gonioscopy or an UBM examination; (5) aPAC cases with a bilateral acute attack; (6) subacute cases with atypical symptoms and signs; (7) FaPAC had PAS; and (8) FcPACG had PAS for >3 cumulative clockhours or extended PAS in the superior quadrant.
Methods A gonioscopic examination was performed and recorded by one of the researchers (L.-L.W.). An occludable angle was defined as the presence of at least 180 degrees of the angle in which the posterior trabecular meshwork was not visible with static gonioscopy. The presence, as well as the extension of PAS, was determined by using a dynamic compression technique with a Goldmann gonioscope (Single Mirror Gonio Lens; Ocular Instruments, Bellevue, WA). An LPI had been performed on all studied eyes. One percent pilocarpine was discontinued for at least 1 week before the UBM examination. UBM was performed in a supine position in a dark room (< 1 lux, measured with an ST-92 luminance meter; Beijing Teachers University Photoelectricity Instrument Factory, Beijing, China) by using a 50-MHz transducer (Paradigm Medical Instruments Inc.,
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Salt Lake City, UT). After a topical anesthesia was applied, an eyecup containing hydroxyethyl cellulose and a physiological saline were placed on the globe and care was taken not to exert pressure on the globe. Variation in accommodation was minimized by utilizing fixation of the contralateral eye on a standard distance target on the ceiling. Each eye was examined in its axial section with a probe kept perpendicular to the corneoscleral surface. All UBM images were analyzed by a single researcher (H.-J.C.). Areas with PAS were avoided during a biometric analysis and measurement. Standard photographs were selected for a qualitative assessment of the parameters including anterior iris insertion, anterior rotation of the ciliary process, and plateau iris (Fig. 1). The definitions of these qualitative parameters were as follows, and an eye was considered to have one of these factors if at least 2 quadrants fulfilled the following criteria: (1) Anterior iris insertion was defined as an iris insertion at the base of the ciliary body near the scleral spur. (2) Anterior rotation of the ciliary process was defined as an anteriorly directed ciliary process that was entirely in contact with the peripheral iris and without a ciliary sulcus. (3) Plateau iris was defined if all of the following points were fulfilled by using the criteria proposed by Kumar and colleagues.16,17 (a) The ciliary process was anteriorly directed and was supporting the peripheral iris, so it was parallel to the trabecular meshwork. (b) The iris root had a steep rise from its point of insertion, followed by a downward angulation to the corneoscleral wall. (c) Presence of a central, flat iris plane. (d) An absent ciliary sulcus. (e) An irido-angle contact (above the level of the scleral spur) in the same quadrant. For the quantitative measurements, the superior quadrant was selected. As illustrated in Figure 2, quantitative UBM parameters including central anterior chamber depth (ACD), basal iris thickness (IT500), and scleral ciliary process angle (SCPA) were measured according to the methods of Pavlin et al18 as follows: (1) The ACD was measured from the corneal endothelium to the anterior lens surface. (2) The IT500 was measured along a line extending from the corneal endothelium and 500 mm from the scleral spur, perpendicularly through the iris. (3) The SCPA was measured between a line that was tangent to the scleral surface and the axis of the ciliary body. UBM pro 2000 software (Paradigm Medical Industries Inc.) was used for the quantitative measurements.
Statistics Analysis All analyses were performed by using the SPSS15.0 statistical software (SPSS Inc., Chicago, IL). For the quantitative parameters, the independent samples t test was used. For the qualitative data, a w2 test was used. A P value of 3 cumulative clock-hours or extended PAS in the superior quadrant, 13]. Finally, 77 eyes from 77 patients were Copyright
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In the current study, in order to investigate typical aPAC and cPAC cases, we used robust inclusion and exclusion criteria to exclude the subacute type of PAC and those cases with an overlap in their clinical presentation, including those with chronic angle-closure glaucoma developed after the resolution of the acute episode and those that had an acute-on-chronic PACG. As we know, the angle configuration and iris profile can be dramatically altered in eyes that are experiencing an acute attack or extensive PAS. However, PAC(G) is a bilateral disease, so patients have a similar anatomic configuration, as well as susceptibility in both the eyes. Therefore, for this study, we chose to analyze FaPAC and FcPACG, neither of which had experienced an acute attack nor had extensive PAS. The UBM results from the present study showed that a plateau iris was much more common in FcPACG (31.6% vs. 16.9%; P = 0.046) than in FaPAC. A plateau iris is a main component of a nonpupillary block mechanism in PACG, in which the angle remains appositionally closed or occludable after LPI.19 Kumar and colleagues found that about one third of eyes had a plateau iris in PAC suspect (32.3%) and PACG (32.4%).16,17 In the other study,14 the authors compared the prevalence of a plateau iris configuration between FaPAC and cPACG eyes in a relatively small group of patients and found no significant difference (37% in 27 FaPAC; 34.6% in 26 PACG eyes) that was different from our results. Several reasons may explain the difference. First, the inclusion and exclusion criteria in this study were stricter. Second, a diagnosis of a plateau iris included “irido-angle contact” in this study. Third, we had a higher patient number in this study. Our findings indicated that more eyes with cPAC(G) may still have an appositional angle closure and an increased risk of gradually developing PAS and may still experience an increase in IOP with an LPI treatment alone than eyes with aPAC. An “incomplete” type of plateau iris syndrome was considered to be more common than the “complete” form of the syndrome.20 With an incomplete plateau iris syndrome, the iris is not as far forward as in the complete syndrome, in the presence of an anteriorly positioned ciliary process and an absent ciliary sulcus. Therefore, in addition
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Volume 24, Number 3, March 2015
FIGURE 2. An illustration of the quantitative measurement for the ACD, IT500, and SCPA. A, ACD was measured from the corneal endothelium to the anterior lens surface. B, IT500 was measured along a line extending from the corneal endothelium and 500 mm from the scleral spur, perpendicularly through the iris. SCPA was measured between a line that was tangent to the scleral surface and the axis of the ciliary body. ACD indicates central anterior chamber depth; IT500, basal iris thickness; SCPA, scleral ciliary process angle.
to a “complete” plateau iris, we also analyzed the ciliary process position separately, and we found more eyes in the chronic group (25 of 57 eyes; 43.9%) had an anteriorly rotated ciliary process than those in the acute group (23 of 77 eyes; 29.9%), although the difference was not statistically significant (P = 0.09). As a quantitative UBM parameter, SCPA reflects the position of the ciliary process. Similarly, the FcPACG had a significantly smaller SCPA than the FaPAC in our study (27.32 ± 4.79 vs. 33.01 ± 5.03 degrees; P < 0.001) that demonstrated the ciliary process was more anteriorly rotated in FcPACG than in FaPAC. An anteriorly inserted iris root at the scleral spur was also considered responsible for cPAC.10 We found a higher proportion of an anterior iris insertion in FcPACG (59.65%) than in FaPAC (49.35%), but the difference was not statistically significant (P = 0.222). The present study showed that ACD was markedly shallower in FaPAC (1.802 ± 0.210 vs. 1.994 ± 0.210 mm; P < 0.001) than in FcPACG. This was consistent with the results of the other 2 studies.11,12 The shallower ACD noted in the acute group was likely to predispose an eye to a greater iris-lens contact and thus, pupillary block. Recent studies demonstrated that an increased iris thickness was associated with narrow angles and angle closure.21,22 The UBM results in the present study showed that FcPACG had a markedly thicker basal iris (0.409 ± 0.059 vs. 0.330 ± 0.051 mm; P < 0.001) than FaPAC under a dark condition. However, previous studies found no significant difference in IT500 between eyes TABLE 1. Comparison of Postiridotomy Ultrasound Biomicroscopy Parameters Between 2 Groups
FaPAC (N = 77) ACD (mm) IT500 (mm) SCPA (deg.) Anterior insertion of the iris [n (%)] Plateau iris [n (%)] Anterior rotation of ciliary process [n (%)]
1.802 ± 0.210 0.330 ± 0.051 33.01 ± 5.03 38 (49.35%) 13 (16.88%) 23 (29.87%)
FcPACG (N = 57)
P
1.994 ± 0.210 < 0.001 0.409 ± 0.059 < 0.001 27.32 ± 4.79 < 0.001 34 (59.65%) 0.222 18 (31.58%) 25 (43.86%)
0.046 0.090
ACD indicates anterior chamber depth; FaPAC, fellow eyes of acute primary angle closure; FcPACG, fellow eyes of chronic primary angle-closure glaucoma; IT500, basal iris thickness (measured on a line extending from the corneal endothelium 500 mm from the scleral spur perpendicularly through the iris); SCPA, scleral ciliary process angle.
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experiencing cPAC and aPAC with light-conditioned UBM.11,12 Use of a different illumination during a UBM examination may be one reason for this discrepancy. Another reason may be pharmaceutical influence on iris thickness. In our study, pilocarpine was discontinued in all eyes at least 1 week before the examination. There were some limitations in the current study. As previously mentioned, we focused only on the 2 ends of the PAC(G) spectrum; however, there were some cases with an overlapping clinical presentation that existed in the middle of the spectrum that were not studied here. For a qualitative assessment, by using a uniform definition for the parameters and standard photographs, we created a dichotomous classification of the parameters including anterior iris insertion, anterior rotation of the ciliary process, and plateau iris. However, there may be a range of appearances with UBM, and some mild cases were not diagnosed according to the criteria in our study. This was a potential source of bias. In the quantitative study, all 4 quadrants were not studied. As the superior quadrant is most susceptible to angle closure, the superior quadrant was selected for the quantitative measurement. Moreover, according to the inclusion criteria of the 2 study groups, the FaPAC did not have PAS, but the FcPACG had limited PAS that should be avoided while interpreting UBM images; therefore, the person who interpreted the images was aware of the clinical diagnosis. This was also a potential source of bias. Another potential weakness that should be mentioned here was the use of a Goldmann lens to perform indentation gonioscopy. Because of the depth of the central “well” of the lens, a Goldmann lens would not likely be as effective at indenting the central cornea or opening the peripheral angle as a flatter “Zeiss” type lens would and it was likely that we overestimated the extent of PAS in some patients. Finally, the lens position and thickness,23 as well as a new parameter, the lens vault,24 defined as the perpendicular distance between the anterior pole of the crystalline lens and a horizontal line joining the 2 scleral spurs, were also important factors contributing to angle closure. However, the lens parameters could not be well investigated with UBM and were not included in this study. The concept that a nonpupillary block component may play a more important role in the chronic type than in the acute type of PAC(G) has been widely accepted. However, a theoretical basis for this concept is limited.14 In our study, we analyzed most of the parameters related to a nonpupillary block mechanism including plateau iris,
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J Glaucoma
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anterior inserted iris, anteriorly rotated ciliary process, and IT500. Besides, by just analyzing the fellow eyes in both the groups, we did not measure the areas that had a dramatic angle alteration that resulted from an acute attack or extensive angle synechia; therefore, this made our study results more reliable. Our study suggests that with a different clinical presentation and natural disease course, some variations exist regarding the anatomic configurations between aPAC and asymptomatic cPAC in Chinese patients. Accordingly, we should treat aPAC and cPAC separately, rather than combining them in clinical practice and research. Also, we believe further refinement of the current classification systems (such as including the symptoms and signs of an acute attack as a defining feature of an angle closure) is advisable. REFERENCES 1. Wang N, Wu H, Fan Z. Primary angle closure glaucoma in Chinese and Western populations. Chin Med J (Engl). 2002; 115:1706–1715. 2. Foster PJ, Johnson GJ. Glaucoma in China: how big is the problem? Br J Ophthalmol. 2001;85:1277–1282. 3. Ang LP, Aung T, Chua WH, et al. Visual field loss from primary angle-closure glaucoma: a comparative study of symptomatic and asymptomatic disease. Ophthalmology. 2004; 111:1636–1640. 4. American Academy of Ophthalmology. Laser peripheral iridotomy for pupillary-block glaucoma. Ophthalmology. 1994; 101:1749–1758. 5. Aung T, Ang LP, Chan SP, et al. Acute primary angle-closure: long-term intraocular pressure outcome in Asian eyes. Am J Ophthalmol. 2001;131:7–12. 6. Aung T, Friedman DS, Chew PT, et al. Long-term outcomes in Asians after acute primary angle closure. Ophthalmology. 2004; 111:1464–1469. 7. Lim LS, Aung T, Husain R, et al. Acute primary angle closure: configuration of the drainage angle in the first year after laser peripheral iridotomy. Ophthalmology. 2004;111:1470–1474. 8. Friedman DS, Chew PT, Gazzard G, et al. Long-term outcomes in fellow eyes after acute primary angle closure in the contralateral eye. Ophthalmology. 2006;113:1087–1091. 9. Ang LP, Aung T, Chew PT. Acute primary angle closure in an Asian population: long-term outcome of the fellow eye after prophylactic laser peripheral iridotomy. Ophthalmology. 2000; 107:2092–2096.
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