|Year : 2018 | Volume
| Issue : 1 | Page : 30-35
Short-term study of intraocular lens position changes using ultrasound biomicroscopy in high myopia
Ayser A.H. Fayed MD
Department of Ophthalmology, Benha Faculty of Medicine, Benha University, Benha, Egypt
|Date of Submission||17-Feb-2017|
|Date of Acceptance||13-Jul-2017|
|Date of Web Publication||1-Feb-2018|
Ayser A.H. Fayed
Faculty of Medicine, Ophthalmology Department, Banha-Cornish El-Nile - El-Rahma Tower, Postal code 13512, Khalyopia, Benha
Source of Support: None, Conflict of Interest: None
The aim of this work was to study the performance of the implanted one-piece versus three-piece intraocular lenses (IOLs) in relation to the dimension of the capsular bag of the highly myopic eyes.
This was a retrospective comparative case–control study.
Patients and methods
One-piece IOL was implanted in 25 eyes of 13 patients (group A), and three-piece IOL was implanted in 25 eyes of 17 patients (group B). Ultrasound biomicroscopy was performed postoperatively. The main outcome measures included anterior chamber depth, angle opening distance, trabecular–iris angle, diameter of the capsular bag, diameter of the implanted IOL, and white-to-white distance. All patients included in this study had highly myopic eyes with axial length greater than 26.5 mm. All eyes were planned for clear lens extraction or cataract extraction.
The mean follow-up period was 3.81±1.82 months. In group A, a statistically significant negative correlation was found between the diameter of the capsular bag and the diameter of the implanted one-piece IOL (r=−0.56). In group B, a statistically significant positive correlation was found between the diameter of the capsular bag and the diameter of the implanted three-piece IOLs (r=0.88). There was a statistically significant correlation regarding anterior chamber depth, angle opening distance, and trabecular–iris angle (P=0.02, 0.03, and 0.04, respectively).
Ultrasound biomicroscopy showed that there was a difference regarding the positioning of the IOL in highly myopic eyes. The statistical analyses, in both groups, point to a statistically significant correlation between the diameter of the capsular bag and the diameter of the implanted IOL.
Keywords: capsular bag, intraocular lens, myopia, ultrasound biomicroscopy, white-to-white distance
|How to cite this article:|
Fayed AA. Short-term study of intraocular lens position changes using ultrasound biomicroscopy in high myopia. Delta J Ophthalmol 2018;19:30-5
|How to cite this URL:|
Fayed AA. Short-term study of intraocular lens position changes using ultrasound biomicroscopy in high myopia. Delta J Ophthalmol [serial online] 2018 [cited 2018 Mar 17];19:30-5. Available from: http://www.djo.eg.net/text.asp?2018/19/1/30/224559
| Introduction|| |
Ultrasound is a good imaging method and plays a critical part in ophthalmological diagnoses. Conventional B-scan examinations produce two-dimensional cross-sectional views of the eye and orbit. This strategy for imaging is the most vital examination system for intraocular lesions, particularly in the presence of anterior segment opacities .
Ultrasound biomicroscopy (UBM) gives images in vivo without influencing the internal relationship of the imaged structures. It provides information that is unobtainable by other noninvasive approaches. It is a good method to evaluate unequivocally anatomic relations among the anterior segment structures ,.
Moreover, UBM provides a unique technique to test the exact intraocular lens (IOL) location and its relationship to adjacent ocular structures. It produces short wavelengths that provide higher resolution and accurate measurement ,.
Most IOL companies manufacture a given IOL model with one overall diameter for implantation in the capsular bag, considering a certain uniformity of the capsular bags receiving these IOLs; however, a solitary IOL overall length may not ideally fit all capsular bags. Notwithstanding individual variety, axial length and age are additionally outstanding components in deciding crystalline lens diameter. This variability in the size of the capsular bag can be a reason for postoperative IOL complications including decentration, tilt, and refractive insecurity . Postoperative refraction deviations may develop through the postoperative axial movement of the optic, tilt, and/or decentration of the IOL ,,.
In a myopic eye with a larger capsular bag, the use of the same IOL size could lead to an insufficient capsular tension, resulting in asymmetrical IOL fixation, capsular fold, and an increased likelihood of posterior capsule opacification . This situation leads to various inquiries: what is the anatomical position of the IOL and capsular bag in various sized eyes implanted with IOLs of the same diameter? Could increasing IOL diameters, as a function of the increasing axial length of the eye, improve the anatomical and functional results of bag implantation? Could experimentation enhance adaptability of such an IOL system? 
The purpose of this study was to assess, through UBM, the characteristics of the anterior segment and IOL position. The short-term outcome of the implanted one-piece versus three-piece IOLs in relation to the dimensions of the capsular bags of the highly myopic eyes.was compared
| Patients and methods|| |
This is a retrospective comparative case–control study based on the review 50 eyes of 30 patients, who had undergone phacoemulsification with posterior chamber IOL implantation and who were selected randomly. All surgeries were performed by three experienced surgeons under local anesthesia. Patients were divided into two groups: group A included 25 eyes that underwent phacoemulsification with implantation of one-piece IOLs (corneal IOLs, with optic diameter of 6.00 mm and an overall diameter of 12.00 mm) and group B that included 25 eyes that underwent phacoemulsification with implantation of three-piece IOLs (Acrysof IOLs; Alcon Laboratories Inc., Fortworth, Texas, USA, with optic diameter of 6.00 mm, and an overall diameter of 13.00 mm, with an acrylic optic and polymethyl methacrylate haptics). All patients included in this study had highly myopic eyes, with axial length greater than 26.5 mm. The spherical equivalent in all patients was more than −6.00 D. The patients were planned for clear lens extraction or cataract extraction by Megatron phacoemulsification machine (Geuder AG, Heidelberg, Germany).
The patients were recruited from the outpatient clinic of the Ophthalmology Department of Benha University Hospital, Benha, Egypt.
Any ocular pathology (other than cataract), including corneal opacities, history of previous ocular surgery, lens subluxation, and pseudoexfoliation syndrome as well as any operative complications such as ruptured posterior capsule and cases that had sutured wounds were excluded from the study. Moreover, cases that did not show in the bag implantation of their IOLs or signs of decentration during the postoperative follow-up were also excluded.
Ethical approval for this study was provided by the Institutional Review Board of the College of Medicine of Benha University, and a written informed assent was obtained from all patients.
Preoperative examination included full medical history; refraction whenever possible; best-corrected visual acuity; intraocular pressure measurement by applanation tonometry; slit-lamp examination for the conjunctiva, cornea, anterior chamber, iris, and lens; and fundus examination. Ultrasonography was used to assess the fundus in opaque media. The axial length of the eye was measured by A-scan biometry for IOL power calculation (Sonomed Inc., Lake, New York, USA) in eyes with dense cataract, whereas most of the eyes were examined by LensStar (LS 900; Haag Streit Diagnostic, Switzerland). SRK-T formula was used, with target postoperative refraction of −1 D.
Ultrasound biomicroscopy of the ocular anterior segment
Scanning was performed preoperatively, and then at one and at least 3 months postoperatively. It was conducted with nondilated pupil and with the patient in a supine position, using UBM model (VUMAX II; Sonomed Inc.). The UBM probe was used to obtain four radial scans at the four quadrants, while kept perpendicular to the ocular surface and central on the pupil. The depth of scans ranged from the anterior corneal surface to the posterior lens capsule. The UMB images were exported and analyzed. For best and easy understanding of the statistical results and standardized change, the temporal one was chosen for data acquisition (which is approved by many researchers).
The device has been shown to measure the central anterior chamber depth (ACD), defined as the distance between the center of the corneal surface (corneal endothelium) and the anterior lens capsule; angle opening distance (AOD 500 μm), defined as the distance between the posterior corneal surface and the anterior iris surface measured on a line perpendicular to the trabecular meshwork at 500 µm from the sclera; and trabecular–iris angle (TIA), measured with the apex at the scleral spur and the arms of the angle passing through the point on the meshwork 500 µm from the scleral spur and the point on the iris perpendicularly opposite side.
Diameter of the capsular bag was measured from the equatorial edge of the capsular bag. Diameter of the implanted IOL was measured from the end of one haptic to the end of the other haptic, and white-to-white distance was measured from the outer aspect of the corneoscleral junction on one side to the opposite side. The data were then analyzed with a view to its consequences for the sizing and design of IOLs. The capsular bag diameter (CBD) of the myopic eyes was measured after implantation, in order to compare both different designs and sizes of IOLs (one-piece and three-piece IOLs).
Comparison of quantitative variables of the two groups was done using Student’s t-test. Comparison between preoperative and postoperative data was done using paired t-test for comparing categorical data. χ2-Test was performed. The association between two variables was done using correlation coefficient. A P value less than 0.05 was considered statistically significant. P value less than 0.001 was considered statistically highly significant. All statistical calculations were done using statistical package for the social sciences (version 16; SPSS Inc., Chicago, Illinois, USA).
| Results|| |
The study included 50 eyes of 30 patients: 11 (36.6%) women and 19 (63.3%) men, with a mean age of 49.07 years. All the eyes were highly myopic. The mean spherical equivalent was −19.87 D (range: −13.60 to −24.60 D) preoperatively and became −1.89 D (plano to −2.10 D), postoperatively. The mean axial length was 29.59±1.94 mm. A larger proportion of the patients had nuclear cataracts (51%) and posterior subcapsular cataract (44%), whereas small proportion (5%) had clear lens. The outcome of UBM of the anterior segment is listed in [Table 1],[Table 2],[Table 3].
|Table 1: Anterior chamber depth (mm) in the study population throughout the follow-up with comparison between preoperative and 3-month postoperative values|
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|Table 2: Values of temporal angle opening distance (mm) in the study population throughout the follow-up with comparison between the preoperative and 3-month postoperative values|
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|Table 3: Values of temporal trabecular–iris angle (deg.) in the study population throughout the follow-up with comparison between the preoperative and 3-month postoperative values|
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The mean increase in ACD was 1.09 mm, ∼32% deeper than before surgery ([Table 1] and [Figure 1] and [Figure 1]b). AOD 500 μm, AOD, and TIA were significantly increased postoperatively, with highly significant correlation (P=0.02, 0.03, and 0.04, respectively), as shown in [Table 2] and [Table 3]. The diameters of the capsular bags in relation to the implanted IOLs were statistically analyzed ([Table 4],[Table 5],[Table 6],[Table 7] and [Figure 2]). The measured values of the CBD in groups A and B were not statistically different, whereas on comparing the CBD in relation to the implanted IOL diameter, in group A, a statistically significant negative correlation was found between the diameter of the capsular bag and the diameter of the implanted one-piece IOL (r=−0.56), as shown in [Table 6] and [Figure 3]a and [Figure 4], whereas in group B, a statistically significant positive correlation was found between the diameter of the capsular bag and the diameter of the implanted three-piece IOLs (r=0.88), as shown in [Table 6] and [Figure 5]. In both groups, a statistically significant positive correlation was found between the CBD and white-to-white distance ([Table 7]).
|Figure 1: The ultrasound biomicroscopy view measuring caliper on the image to measure the anterior chamber depth (white line), capsular bag diameter (yellow line, head arrows), white-to-white distance (red line), and intraocular lens diameter (green line)|
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|Table 6: Correlation between capsular bag and intraocular lens diameter in the study groups|
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|Table 7: Correlation between capsular bag diameter and white-to-white distance in the study groups|
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|Figure 2: Anterior chamber depth: (a) preoperative and (b) postoperative (red line)|
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|Figure 3: (a) Ultrasound biomicroscopy (UBM) view of the implanted one-piece intraocular lens (IOL); IOL diameter is 10.00 mm (yellow) and capsular bag diameter is 12.42 mm (green). (b) UBM view of the implanted three-piece IOL; IOL diameter is 10.15 mm (yellow) and capsular bag diameter is 11.68 mm (green)|
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|Figure 4: Correlation between capsular bag diameter (Y) and intraocular lens diameter (X) in group A|
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|Figure 5: Correlation between capsular bag diameter (Y) and intraocular lens diameter (X) in group B|
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The measured values in this study were used to provide a formula, using the white-to-white distance of the eye to calculate the CBD. It is as follows: CBD=1.023×white-to-white distance −0.839. This formula represents an attempt to find an accurate method for predicting the CBD.
| Discussion|| |
An important aim of this study was to assess, through UBM, the positioning of the IOL as related to the CBD and try to answer a critical question, that is, does one design of IOL fit for all capsular bags? For this purpose, two different IOL types with different overall diameters were used in this study, and the selected patients had highly myopic eyes with axial length greater than 26.5 mm. The spherical equivalent in all patients was more than −6 D.
In group A, in which one-piece IOLs (with overall diameter of 12 mm) were implanted, the mean diameter of the implanted one-piece IOLs was 10.01 mm. The correlation between the measured IOL and CBD in this group was found to be statistically significant. Moreover, this correlation was found to be negative (r=−0.56). This means that from the statistical point of view, the larger the CBD, the smaller the IOL diameter needed. In group B, in which three-piece IOLs (with overall diameter of 13 mm) were implanted, the mean diameter of the implanted three-piece IOLs was 10.4 mm. The correlation in this group between the measured IOL and CBD was additionally statistically highly significant. It is a positive correlation in which the correlation coefficient r was 0.88. So, from the statistical point of view, the larger the CBD was, the larger the IOL diameter needed.
Additionally, on comparing the two IOL types, the three-piece IOL appears to show better anatomical fitting in the capsular bag than the one-piece IOL. This is attributed to the negative correlation found in group A between the diameters of the capsular bags and those of the one-piece IOLs in contrast to the positive correlation found in group B between the diameters of the capsular bags and those of the three-piece IOLs and is also attributed to the statistically significant difference found between groups A and B regarding the measured values of the IOL diameters.
Quantitative measurement of anterior segment parameters both preoperatively and postoperatively demonstrated that the mean difference in ACD was 1.09 mm, ∼32% deeper than before surgery, which is statistically highly significant. Similarly, AOD 500 μm and TIA revealed statistically highly significant difference. These finding are supported by previous other studies ,,,,,.
In 2009, an experimental study was performed by Sourdille et al.  to analyze 25 eyes in which phacoemulsification was done, and the capsular bags were implanted with different IOLs of different diameters (including one-piece and three-piece designs) followed by measuring the modifications that were incited in the shape and size of the capsular bags with the guide of high-frequency ultrasound. Three of the implanted three-piece IOL models reliably expanded and ovalized the capsular bags, frequently causing central capsular folds, and these IOLs likewise moved the bag into a retrociliary position. On the contrary, the one-piece IOLs implanted in this study caused no fold and no ovalization of the capsular bags, presuming that an IOL fabricated with only a solitary measurement did not anatomically fit every capsular bag. They also concluded that the concept behind the lens which expresses that highly axial myopic eyes need larger IOL diameter and shorter eyes needed shorter IOL diameters enhances the anatomical circumstance and may maintain best refractive results. These finding were clinically attested in another late prospective randomized bilateral clinical study . All the aforementioned results point to the importance of the adaptability of the IOL diameter to the different bag sizes and the correlation of the IOL diameter with the dioptric power and the axial length of the eye which should result in better capsular bag fitting. Moreover, the difference in the capsular bag size of the highly ametropic eyes may result in unpredictable IOL position with inaccurate refractive outcome.
| Conclusion|| |
Three-piece IOL appears to be better anatomically fitting in the capsular bag than the one-piece IOL. ‘Is one-diameter IOL suitable for every capsular bag?’ is an important question which requires future studies with large number of highly ametropic eyes and different designs of IOL to be answered correctly.
The author thanks Dr Tarek Abulnasr, MD, for his suggestions and commentary on the manuscript.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]