Ultrasound Biomicroscopic Study of Anterior Segment Changes after Phacoemulsification and Foldable Intraocular Lens Implantation Frederico A. S. Pereira, MD, Sebastia˜o Cronemberger, MD Purpose: To report quantitative changes in the anterior segment configuration after clear corneal incision phacoemulsification and foldable intraocular lens (IOL) implantation by means of ultrasound biomicroscopy (UBM). Design: Prospective, nonrandomized, comparative (self-controlled) trial. Participants: Twenty-one eyes of 19 patients with senile or presenile cataracts and no other ocular illness. Methods: Patients were examined with UBM before and 1 and 3 months after surgery. At each UBM examination, axial images of the anterior chamber and radial sections of the angle at the superior, lateral, inferior, and medial quadrants were obtained. Main Outcome Measures: Central anterior chamber depth (ACD), iris–lens contact distance, iris–lens angle (ILA), angle opening distance at points 250 (AOD250) and 500 m (AOD500) from the scleral spur, trabecular–iris angle (TIA), iris thickness 500 m from the scleral spur (IT), trabecular– ciliary process distance (TCPD), iris– ciliary process distance (ICPD), iris–zonule distance, iris–sclera angle (ISA), and ciliary process–sclera angle (CPSA). After surgery, central anterior chamber depth was also measured from the cornea to the IOL (ACD) and from the cornea to the pupillary plane (ACD2). Each variable was measured twice in different days by the same observer. Results: The variables IT, TCPD, ICPD, IZD, and CPSA did not significantly change after surgery (P ⬎ 0.01). Central anterior chamber depth increased approximately 30% after surgery (approximately 850 m; P ⬍ 0.001), by both measurement methods used (ACD ⫻ ACD and ACD ⫻ ACD2). Anterior chamber angle significantly increased, by approximately 50% of the initial value, by the three measurement methods used: AOD250 (P ⱕ 0.002), AOD500 (P ⬍ 0.001), and TIA (P ⱕ 0.003). The ISA increased by approximately 10° (30%) after surgery (P ⬍ 0.001). The ILCD and ILA did not exist after surgery, except in two eyes. Conclusions: After phacoemulsification and foldable IOL implantation, UBM revealed that the iris diaphragm shifted backward, deepening the anterior chamber by approximately 850 m and widening its angle by approximately 10°. These findings may be of clinical significance in eyes with angle-closure glaucoma or with occludable angles. Ophthalmology 2003;110:1799 –1806 © 2003 by the American Academy of Ophthalmology.
Cataract surgery and intraocular lens (IOL) implantation bring about clinically evident changes in the anterior segment configuration. However, quantification of these changes is limited by the instruments and methods currently available. Gonioscopic methods of anterior chamber grading are either complicated to assimilate or too subjective. Originally received: December 7, 2001. Accepted: November 12, 2002. Manuscript no. 211021. From the Department of Ophthalmology, Federal University of Minas Gerais, Belo Horizonte, Brazil. Supported by Coordination for the Improvement of Higher Education Personnel (CAPES), Brası´lia, Brazil. The authors have no financial interest in any of the issues contained in this article and have no proprietary interest in the developing or marketing of the products or medical equipment mentioned in the study. Correspondence to Frederico A. S. Pereira, MD, Av. Joa˜o Pinheiro, 146, sl. 1307, Centro. Belo Horizonte, MG. Brazil 30130-922. E-mail:
[email protected]. © 2003 by the American Academy of Ophthalmology Published by Elsevier Inc.
Quantitative measurements of the anterior chamber are possible by means of Scheimpflug camera devices, but posterior chamber structures are impossible to examine and measure directly because of their optical limitations.1–3 Conventional B-scan ultrasonography lacks resolution for precise quantitative measurements on the anterior segment. Pathologic studies are subject to artifacts during tissue preparation that may impair quantitative structural relationship analyses. Ultrasound biomicroscopy (UBM), developed by Pavlin et al4 in 1990, uses high-frequency ultrasound (50 MHz) to produce in vivo images of the anterior segment with resolution as high as 50 m. It is possible to study in detail and to quantify precisely anatomic relations among the anterior segment structures,5–7 with acceptable reproducibility.8 –11 Kurimoto et al12 previously reported on anterior segment configuration changes after small incision cataract surgery with posterior chamber IOL implantation using UBM. The ISSN 0161-6420/03/$–see front matter doi:10.1016/S0161-6420(03)00623-7
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Ophthalmology Volume 110, Number 9, September 2003 parameters measured included anterior chamber depth (ACD) at the center of the cornea and angle-opening measurements performed only on a temporal UBM radial section. We measured these and some other parameters on a central UBM section and on four radial sections performed on the cardinal quadrants of the globe to study more widely the anterior segment configuration changes after clear corneal phacoemulsification and foldable IOL implantation in the capsular bag.
Materials and Methods We prospectively studied 21 eyes of 19 patients (men, 12 eyes of 11 patients; women, nine eyes of eight patients; all patients aged from 45– 80 years; mean age ⫾ standard deviation, 64.9 ⫾ 10.1 years) with senile or presenile cataracts who consecutively underwent surgery from August 1997 through March 1999. Surgeries were performed at Sa˜ o Geraldo Eye Hospital, Federal University of Minas Gerais, in Belo Horizonte, Brazil, under peribulbar block by the same surgeon (FP). Surgical technique consisted of phacoemulsification and aspiration through a 3.0- to 3.5-mm clear corneal incision followed by foldable IOL implantation in the capsular bag. The IOL haptics were oriented vertically for the purpose of standardization during UBM image acquisition. Thirteen eyes received an AcrySof MA60BM (Alcon Laboratories, Fort Worth, TX) acrylic IOL (group A) and eight eyes received an SI-40NB (Allergan, Irvine, CA) SLM-2 silicone IOL (group S). Both IOLs have a 6-mm optic diameter, are 13 mm in overall length, and have polymethyl methacrylate “modified-C” haptics that are anteriorly angulated by 10°. All patients underwent complete ophthalmic examination, including anamnesis, visual acuity and refraction, keratometry, slitlamp biomicroscopy, applanation tonometry, and indirect ophthalmoscopy. Patients with any ocular abnormality other than senile cataracts and those who underwent previous ophthalmic surgery were not included. Surgical complications that forced changes in the surgical technique described above also led to patient exclusion. Informed consent was required for every patient included in the study. The study protocol was approved previously by the ethics committee of the department of ophthalmology of the Federal University of Minas Gerais. The UBM was performed before and 1 and 3 months after surgery with the Zeiss-Humphrey model 840 (Zeiss-Humphrey Instruments, San Leandro, CA), which incorporates a 50-MHz transducer producing images with 50 m resolution and 4 mm penetration in the ocular tissues. Examinations were performed under constant room illumination (50 lux), with the patient in the supine position. Accommodation was kept constant by asking the patient to fixate on a small light spot held 1 meter from the fellow eye. After instillation of topical 0.5% proparacaine, a polymethyl methacrylate shell was inserted between the lids and was filled with 2% methylcellulose and saline solution for immersion. The UBM section images were obtained axially and radially on the superior, lateral, inferior, and medial quadrants. Image acquisition and measurements were obtained by the same examiner (FP). Using the calipers included in the equipment software, the following variables were measured, as proposed by Pavlin et al6: ACD at the center of the cornea, measured in A-scan mode between the peaks of the posterior corneal surface and the anterior capsule and anterior IOL surface echoes (Fig 1A), iris–lens contact distance (Fig 1B), angle opening distance 250 m from the scleral spur (AOD250), angle opening distance 500 m from the scleral spur, trabecular–iris angle (TIA; Fig 2A), iris thickness 500 m from the scleral spur, trabecular– ciliary process distance, iris–
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Figure 1. Ultrasound biomicroscopic images of the anterior chamber and method of measurement of the variables (A) anterior chamber depth (ACD) and anterior chamber depth 2 (ACD2) and (B) iris–lens contact distance (ILCD) and iris–lens angle (ILA). Bar ⫽ 1 mm.
ciliary process distance (Fig 2B), iris–zonule distance, iris–sclera angle (Fig 2A), and ciliary process–sclera angle (Fig 2B). In pseudophakic eyes, however, the definition of Pavlin et al6 of ACD at the center of the cornea for phakic eyes is inadequate, because the measurement may extend into the posterior chamber. Therefore, Kurimoto et al12 defined the anterior chamber at the center of the cornea in pseudophakic eyes as ACD2 (Fig 1A), measured from the posterior corneal surface to the pupillary plane. In the present study, we adopted this definition for ACD measurement after surgery. Iris profile was classified subjectively as plane, concave, or convex from an anterior perspective. The Mann–Whitney rank-sum test was used to analyze differences between groups A and S. Differences between preoperative and postoperative UBM measurements were analyzed using Friedman repeated measures analysis of variance on ranks. Categorical variables were analyzed using the Fisher exact test. Statistical analyses were conducted using SAS version 5 software (SAS Institute, Cary, NC). Values of P ⬍ 0.01 were considered statistically significant.
Results Groups A and S were not statistically different for each variable studied. Therefore, a single group containing all patients from
Figure 2. Ultrasound biomicroscopic images of the anterior chamber and method of measurement of the variables: (A) angle opening distance 250 m from the scleral spur (AOD250), angle opening distance 500 m from the scleral spur (AOD500), trabecular–iris angle (TIA), iris–zonule distance (IZD), and iris–sclera angle (ISA) and (B) trabecular– ciliary process distance (TCPD), iris thickness 500 m from the scleral spur (IT), iris– ciliary process distance (ICPD), and ciliary process–sclera angle (CPSA). Bar ⫽ 1 mm.
Pereira and Cronemberger 䡠 UBM and Anterior Segment Changes after Phacoemulsification Table 1. Anterior Chamber Depth and Iris–Lens Contact Distance Variable
Before Surgery
30 Days after Surgery
90 Days after Surgery
P Value*
ACD (mm) ILCD (mm)
2.857 (0.402) 0.357 (0.081)
3.681 (0.301) 0.000 (0.047)
3.732 (0.303) 0.000 (0.054)
⬍0.001 ⬍0.001
ACD ⫽ anterior chamber depth; ILCD ⫽ iris–lens contact distance. Values are mean (standard deviation). *Friedman test (n ⫽ 17).
Figure 3. Composite ultrasound biomicroscopy of the same eye (A) before and (B) 30 days after surgery. Note the increase in anterior chamber depth and the change in iris configuration, widening the angle. The iris does not touch the intraocular lens (IOL) surface, whereas it touched the crystalline lens before surgery. Note that the iris profile changes from (A) slightly convex to (B) flat. Arrows ⫽ IOL haptics; bar ⫽ 1 mm.
either group was considered when comparing preoperative and postoperative measurements. Each scanning site—superior, inferior, medial, and lateral—was compared individually in each operative period. Four patients did not show up for examination 3 months after surgery. Therefore, 17 eyes were available for statistical analysis. The lateral preoperative image of one patient was lost; therefore, 16 eyes were considered for statistical analysis in this site. The anterior chamber was significantly deeper in all postoperative periods. The average increase in ACD was 850 m (2.857 ⫾ 0.402 mm before surgery; 3.732 ⫾ 0.303 mm at the third postoperative month), approximately 30% deeper than before surgery (Fig 3 and Table 1). Iris–lens contact distance significantly decreased after surgery (Fig 3 and Table 1). In fact, contact between the iris and the IOL
was observed in only two patients. Both had received silicone IOLs. Angle opening distance 250 m from the scleral spur significantly increased after surgery in the four quadrants (Fig 4 and Table 2). The increase averaged approximately 100 m, 50% more than that before surgery. The measurement on the first month (0.314 ⫾ 0.127 mm) was also significantly higher than on the third postoperative month (0.295 ⫾ 0.138 mm) in the superior quadrant. No statistically significant difference was observed for the remaining quadrants between the first and the third postoperative months. Angle opening distance 500 m from the scleral spur and TIA significantly increased after surgery in the superior, lateral, and medial quadrants (average, 150 m and 10°, respectively; approximately 50% more than before surgery). There was no statistically significant difference between these figures for the first and the third postoperative months (Figs 5, 6, respectively, and Table 2). When comparing the anterior chamber angle opening in the four quadrants examined, we noted that the angle in the superior and inferior quadrants was consistently narrower than in the lateral and medial quadrants compared with the preoperative measurements (Table 2). This difference, however, was statistically significant only in the following circumstances: angle opening distance 500 m from the scleral spur before surgery (lateral greater than inferior and superior, and medial greater than superior; P ⫽ 0.002) and 90 days after surgery (lateral and medial greater than superior and inferior; P ⫽ 0.001), and TIA 30 days after surgery
Figure 4. Angle opening distance 250 m from the scleral spur (in mm) before and 30 and 90 days after surgery.
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Ophthalmology Volume 110, Number 9, September 2003 Table 2. Ultrasound Biomicroscopy Measurements in Each Quadrant
Quadrant
Time Point
Angle Opening Distance 250 mm from the Scleral Spur (mm)
Superior (n ⫽ 17)
Before surgery 30 days after surgery 90 days after surgery P value* Before surgery 30 days after surgery 90 days after surgery P value* Before surgery 30 days after surgery 90 days after surgery P value* Before surgery 30 days after surgery 90 days after surgery P value*
0.217 ⫾ 0.072 0.314 ⫾ 0.127 0.295 ⫾ 0.138 ⬍0.001 0.269 ⫾ 0.079 0.360 ⫾ 0.115 0.339 ⫾ 0.118 0.002 0.234 ⫾ 0.074 0.324 ⫾ 0.096 0.356 ⫾ 0.115 ⬍0.001 0.233 ⫾ 0.074 0.324 ⫾ 0.096 0.357 ⫾ 0.116 ⬍0.001
Lateral (n ⫽ 16)
Inferior (n ⫽ 17)
Medial (n ⫽ 17)
Angle Opening Distance 500 mm from the Scleral Spur (mm)
Trabecular–Iris Angle (Degrees)
Iris–Sclera Angle (Degrees)
0.284 ⫾ 0.095 0.433 ⫾ 0.194 0.430 ⫾ 0.175 ⬍0.001 0.361 ⫾ 0.142 0.509 ⫾ 0.157 0.516 ⫾ 0.162 ⬍0.001 0.297 ⫾ 0.124 0.441 ⫾ 0.142 0.406 ⫾ 0.138 0.012† 0.325 ⫾ 0.127 0.494 ⫾ 0.150 0.515 ⫾ 0.123 ⬍0.001
21.59 ⫾ 7.12 30.86 ⫾ 11.23 31.33 ⫾ 8.81 ⬍0.001 28.41 ⫾ 9.98 36.54 ⫾ 10.38 37.68 ⫾ 9.83 0.003 24.72 ⫾ 10.25 31.43 ⫾ 8.56 32.12 ⫾ 11.72 0.028† 25.05 ⫾ 9.98 36.55 ⫾ 9.86 36.52 ⫾ 7.32 ⬍0.001
29.69 ⫾ 4.59 39.14 ⫾ 2.13 39.56 ⫾ 3.47 ⬍0.001 32.48 ⫾ 4.98 41.00 ⫾ 3.32 42.22 ⫾ 3.41 ⬍0.001 32.45 ⫾ 6.06 40.56 ⫾ 2.82 42.02 ⫾ 3.72 ⬍0.001 31.21 ⫾ 4.41 38.04 ⫾ 3.37 41.15 ⫾ 3.29 ⬍0.001
Values are mean ⫾ standard deviations. *Friedman test, comparing preoperative and postoperative measurements. † Not significant.
(lateral and medial greater than superior and inferior; P ⬍ 0.001; Figs 5, 6 and Table 2). No statistically significant difference was observed between the quadrants in AOD250 in any of the operative periods (Fig 4 and Table 2). Iris–sclera angle increased significantly after surgery in the four quadrants (Fig 7 and Table 2). The increase averaged 10°, 30% more than before surgery. No statistically significant differences were observed between the measurement for the first and the third postoperative months. Only in the lateral quadrant did we observe a statistically significant decrease of iris–zonule distance after surgery (Table 3). The iris thickness 500 m from the scleral spur significantly increased only in the inferior quadrant 90 days after surgery (Table 3). No statistically significant differences were found between preoperative and postoperative measurements of the following
variables: trabecular– ciliary process distance, iris– ciliary process distance, and ciliary process–sclera angle (Table 3). Before surgery, the iris had a flat profile in 11 of the 21 eyes. A convex profile was observed in the remaining 10 eyes. After surgery, all eyes had a flat iris profile (Fig 3). The differences between the frequencies of these findings were statistically significant (P ⬍ 0.001, Fisher exact test).
Discussion The reproducibility of measurements made by UBM was previously assessed by other authors.8 –11 Intraobserver reproducibility was considered good for most of the variables,
Figure 5. Angle opening distance 500 m from the scleral spur (in mm) before and 30 and 90 days after surgery.
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Pereira and Cronemberger 䡠 UBM and Anterior Segment Changes after Phacoemulsification
Figure 6. Trabecular–iris angle (in degrees) before and 30 and 90 days after surgery.
whereas interobserver reproducibility was poor. The experience of the examiner during either image acquisition or analysis is a determinant factor of influence on the results, so comparisons of measurements before and after any intervention should be made by the same observer.8,11 Standardization of the examination procedures, such as accommodation control and room lighting, is also crucial to avoid physiologic alterations in the parameters under investigation. A target for the fellow eye such as a letter or figure on the ceiling with enough detail to produce a blurred image on the retina would be more suitable than the small light spot we used to attempt accommodation control, but most of the patients in the present study had cataract in the fellow eye as
well. Therefore, precise control of accommodation was limited in this study. Although the measurement of some variables may vary largely, with a wide distribution around the mean, statistical analysis may still yield significant results if the differences among the measurements are sufficiently large.11,13 To assess only the most relevant and unequivocal changes, we chose a P value of less than 0.01 as statistically significant. Despite some study limitations, such as sample size, variations in UBM examination, and surgery, we believe that the data obtained can be trusted for quantitative analysis. Anterior chamber depth significantly deepened after surgery (approximately 850 m; P ⬍ 0.001; Table 1) because
Figure 7. Iris–sclera angle (in degrees) before and 30 and 90 days after surgery.
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Ophthalmology Volume 110, Number 9, September 2003 Table 3. Ultrasound Biomicroscopy Measurements in Each Quadrant
Quadrant
Time Point
Iris–Zonule Distance (mm)
Superior (n ⫽ 17)
Before surgery 30 days after surgery 90 days after surgery P value* Before surgery 30 days after surgery 90 days after surgery P value* Before surgery 30 days after surgery 90 days after surgery P value* Before surgery 30 days after surgery 90 days after surgery P value*
0.651 ⫾ 0.082 0.576 ⫾ 0.098 0.593 ⫾ 0.091 0.056† 0.626 ⫾ 0.088 0.546 ⫾ 0.106 0.571 ⫾ 0.106 0.003 0.625 ⫾ 0.108 0.539 ⫾ 0.111 0.584 ⫾ 0.106 0.035† 0.618 ⫾ 0.106 0.588 ⫾ 0.108 0.620 ⫾ 0.136 0.663†
Lateral (n ⫽ 16)
Inferior (n ⫽ 17)
Medial (n ⫽ 17)
Iris Thickness (mm)
Trabecular–Ciliary Process Distance (mm)
Iris–Ciliary Process Distance (mm)
Ciliary Process–Sclera Angle (Degrees)
0.291 ⫾ 0.062 0.317 ⫾ 0.067 0.323 ⫾ 0.079 0.012† 0.296 ⫾ 0.062 0.301 ⫾ 0.058 0.334 ⫾ 0.069 0.210† 0.319 ⫾ 0.071 0.341 ⫾ 0.115 0.315 ⫾ 0.071 0.790† 0.320 ⫾ 0.057 0.296 ⫾ 0.058 0.337 ⫾ 0.063 0.005
0.916 ⫾ 0.239 0.945 ⫾ 0.271 0.904 ⫾ 0.217 0.220† 0.896 ⫾ 0.253 0.929 ⫾ 0.177 0.926 ⫾ 0.153 0.544† 0.867 ⫾ 0.235 0.890 ⫾ 0.256 0.962 ⫾ 0.247 0.101† 0.965 ⫾ 0.237 0.940 ⫾ 0.289 1.078 ⫾ 0.305 0.112†
0.357 ⫾ 0.155 0.251 ⫾ 0.179 0.240 ⫾ 0.170 0.018† 0.273 ⫾ 0.157 0.208 ⫾ 0.107 0.180 ⫾ 0.095 0.039 0.276 ⫾ 0.126 0.192 ⫾ 0.136 0.287 ⫾ 0.165 0.060† 0.343 ⫾ 0.170 0.239 ⫾ 0.211 0.303 ⫾ 0.210 0.080†
46.32 ⫾ 8.36 51.39 ⫾ 6.59 51.79 ⫾ 8.84 0.056† 48.02 ⫾ 6.95 52.44 ⫾ 5.42 49.60 ⫾ 4.63 0.029† 49.26 ⫾ 5.48 51.30 ⫾ 6.00 52.15 ⫾ 6.35 0.230† 48.17 ⫾ 8.36 53.11 ⫾ 7.45 52.51 ⫾ 7.11 0.012†
Values are mean ⫾ standard deviations. *Friedman test, comparing preoperative and postoperative measurements. † Not significant.
of a backward movement of the iris diaphragm away from the corneal inner surface (Fig 3). Kurimoto et al12 found similar results studying 20 eyes. Iris–lens or iris–IOL contact distance and the angle formed by this contact are variables of special interest when investigating pigment dispersion syndrome and pigmentary glaucoma14 –17 and angle-closure glaucoma.18 –22 In situations of blood–aqueous barrier breakage, contact of the posterior iris surface to the IOL or the anterior capsule may lead to posterior synechiae formation and IOL capture, and ultimately to pupillary block.23–25 Contact between IOL and uveal tissue, moreover when the IOL is implanted in the ciliary sulcus, was pointed out as an important etiologic factor in other IOL-related complications, such as uveitis, glaucoma, hyphema, iris chafing, and pupillary distortion.26 –30 In the present study, iris–lens contact was observed in all eyes before surgery (Fig 3). After surgery, iris–IOL contact was observed only in two eyes, but none of the complications listed above have yet been observed. Those two patients received silicone lenses, which are thicker than the acrylic lenses because of their lower index of refraction. One of these patients had the smallest axial length of the entire sample studied (21.46 mm), which may have contributed to the proximity of the IOL to the iris. Kurimoto et al12 studied in 20 eyes the variables related to anterior chamber angle measurement (AOD250, angle opening distance 500 m from the scleral spur, and TIA) before and 3 months after phacoemulsification and foldable IOL implantation. The type of IOL implanted was not mentioned. Only the lateral quadrant was examined. They found significant increase in the anterior chamber angle opening after surgery in these three variables. There was a significant correlation between the preoperative values and the postoperative changes: the shallower the preoperative anterior chamber, the greater the postoperative deepening; the narrower the preoperative angle, the greater the postop-
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erative opening of the angle. In these three variables, we also observed in the present study a significant increase in the anterior chamber angle opening (Figs 4 – 6 and Table 2). We found a statistically significant difference between the first and the third postoperative month on the superior quadrant for AOD250. This difference was 0.019 mm (mean), representing approximately the size of a pixel (0.012 ⫻ 0.024 mm), and was under the resolution of the ultrasound biomicroscope. Therefore, this difference is not clinically significant. The finding that the angle opening was statistically narrower in the horizontal quadrants in some instances may not be attributed to the IOL haptics, positioned in the vertical meridian, because this difference was also observed before surgery. The IOL haptics were implanted in the capsular bag, in a position unlikely to cause anterior displacement of the iris or angle structures. This is probably the normal configuration of the human angle in the supine position, but this assumption requires confirmation in further studies. Iris–sclera angle significantly increased after surgery in all quadrants (Fig 7 and Table 2). This means that after surgery, a posterior shift of the iris diaphragm took place, increasing the ACD and the angle opening. This posterior shift occurred by means of an angular movement of the iris (Fig 3). The ciliary processes and the zonules did not show significant changes in configuration after surgery. When the pressures in the anterior and posterior chambers are different, there is a corresponding change in the iris profile, as opposed to the flat profile observed when the pressures are balanced. A concave iris profile may be observed in patients with pigment dispersion syndrome or pigmentary glaucoma.16,17,31 A convex iris profile may be related to relative pupil block and can be seen in narrowangle glaucoma.18,20,32,33 In the present study, all of the eyes with a convex iris profile before surgery assumed a planar iris profile after surgery (Fig 3). When the catarac-
Pereira and Cronemberger 䡠 UBM and Anterior Segment Changes after Phacoemulsification tous lens was removed, it was possible to balance the pressure in the anterior and posterior chambers by eliminating the contact between it and the iris. Because the IOL is much thinner than the natural lens, this contact did not happen after surgery. Our findings support those of Kurimoto et al.12 By studying other structures that participate in the anterior segment anatomy, such as the ciliary processes, the zonules, and the iris, additional elements were added to understand the mechanisms of the changes that occur after cataract surgery and IOL implantation. As stated by Kurimoto et al,12 whereas the iris in phakic eyes was in contact with the lens, the iris in pseudophakic eyes was free from IOL contact, as long as it was implanted in the capsular bag. This suggests that the iris was pushed forward by the lens in phakic eyes and shifted backward after lens removal and IOL implantation, thus deepening the anterior chamber and widening the angle. Our findings support these observations, adding the objective measurement of the angular movement of the iris. This movement comprised approximately 10°, resulting in a similar increase in the anterior chamber angle. The pupillary plane shifted backwards from the anterior chamber wall, deepening the anterior chamber by approximately 850 m. All these findings can be observed in Figure 3. By means of Scheimpflug videophotography, anterior chamber deepening and angle opening in eyes with primary angle-closure glaucoma (PACG) were demonstrated quantitatively after phacoemulsification and foldable acrylic IOL implantation by Hayashi et al.34 Angle opening increase was similar to that observed in the present study, which did not include glaucomatous eyes and occludable angles. They also noted that the anatomic differences between PACG eyes and normal or open-angle glaucoma eyes decreased after surgery. The IOP decreased after surgery and up to 12 months of follow-up. Primary angle-closure glaucoma as a cause is mainly attributed to anatomic factors. In PACG patients, the anterior chamber is shallower and of smaller volume than in normal eyes and the lens is usually thicker than normal and is located in a more anterior position than in an eye with a short axial length.35–39 Cataract extraction has been studied as an effective therapeutic option for patients with PACG or narrow angle by several authors since as early as 1945.12,34,40 – 48 The anatomic changes observed in the present study provide an anatomic basis to support previous and future studies addressing cataract extraction and IOL implantation as an appropriate treatment for patients with cataract and PACG or occludable angles.
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