|Year : 2020 | Volume
| Issue : 3 | Page : 173-179
Effects of phacoemulsification on intraocular pressure and anterior chamber depth
Tarek A Hafez
Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria, Egypt
|Date of Submission||19-Jun-2019|
|Date of Decision||31-Jul-2019|
|Date of Acceptance||28-Dec-2019|
|Date of Web Publication||23-Sep-2020|
MD Tarek A Hafez
Department of Ophthalmology, Faculty of Medicine, Alexandria University, Alexandria 21523
Source of Support: None, Conflict of Interest: None
Purpose The aim of this study was to investigate the effects of phacoemulsification and intraocular lens (IOL) implantation, in nonglaucomatous patients with cataract, on intraocular pressure (IOP) and anterior chamber depth (ACD) together with quantification of other anterior chamber parameters.
Patients and methods A total of 76 patients (100 eyes) with senile cataract were included in this study. All patients had normal IOP. Patients with history of uveitis, glaucoma, other ocular diseases, or surgery were excluded. All patients underwent phacoemulsification with IOL implantation by the same surgeon from May 2018 to August 2018 and were followed up for 1 month. The ACD was measured with the use of Pentacam rotating Scheimpflug camera.
Results There was a significant difference between the preoperative IOP (15.24±7.05 mmHg) and the postoperative IOP (11.83±3.75 mmHg) (t=6.259, P<0.01). This was associated with a significant increase in the ACD from a preoperative value of 3.1±0.8 mm to a postoperative value of 3.8±0.8 mm (t=0.870, P<0.0001). There was also a significant increase in the anterior chamber angle from a preoperative value of 34.1±9.3° to a postoperative value of 40.6±5.9° (t=5.760, P=0.003) and in the anterior chamber volume from a preoperative value of 161.3±36.7 mm3 to a postoperative value of 197.1±26.1 mm3 (t=36.200, P<0.0001).
Conclusion The present study, performed with the Pentacam rotating Scheimpflug camera system, confirmed that, in normotensive eyes with open iridocorneal angles, the anterior chamber volume and ACD increased and the anterior chamber angle widened following uneventful phacoemulsification and IOL implantation. These changes were accompanied by a significant decrease in IOP 1 month postoperatively. Further studies are required to prove the safety and mechanism of lowering the IOP following phacoemulsification.
Keywords: anterior chamber depth, cataract, intraocular pressure, phacoemulsification
|How to cite this article:|
Hafez TA. Effects of phacoemulsification on intraocular pressure and anterior chamber depth. Delta J Ophthalmol 2020;21:173-9
| Introduction|| |
The incidence of cataract and glaucoma, including primary angle closure (PAC), gradually increases with age. Some patients experience both cataract and glaucoma. In the treatment of PAC, phacoemulsification and intraocular lens (IOL) implantation have been used. The occurrence and development of disease risk factors, the anterior chamber angle (ACA) of PAC, and the degree of intraocular pressure (IOP) were reported to be significantly improved by phacoemulsification ,.
The general risk factors for primary angle closure glaucoma (PACG) include family history of angle closure ,, age ,, sex ,,, and Asian descent . Other risk factors include hyperopia , the perimeter of the shallow anterior chamber , the perimeter of the central shallow anterior chamber , the steepness of corneal curvature , the thickness of the lens, and the axial length of the eye .
Although the most common way to control IOP in medically uncontrolled glaucoma is glaucoma filtering procedures, they carry significant risks . Considering that many patients with glaucoma have concurrent cataract, it seems reasonable to study the effect of cataract surgery on IOP changes and considering this effect to choose the patients in whom cataract surgery alone could be a safe alternative for glaucoma surgery. There is increasing evidence that uneventful cataract extraction can result in anterior chamber deepening, iridocorneal angle widening, and IOP reduction in glaucomatous or nonglaucomatous eyes . Several studies , showed that cataract extraction provides the opportunity to restore vision and to eliminate a narrow angle in eyes with acute PAC or chronic PACG. Previous studies confirmed that IOP lowering was related to angle opening induced by cataract surgery. However, the anatomic predictors of angle widening and IOP decrease after phacoemulsification with foldable IOL implantation have not been fully understood .
Although cataract surgery and IOL implantation lead to clinically evident deepening of the anterior chamber and widening of the iridocorneal angle, quantification of these changes has been limited by the availability of instruments and methods with which to assess them. Traditional evaluation of the ACA by the Shaffer, Sheie, or Herick method depends on subjective assessment. Applanation or immersion A-scan ultrasound has shown considerable variability between measurements , between observers , and between manufacturers , primarily as a result of applanation effects and misalignment of the hand-held probe. More accurate and quantitative evaluation of the ACA or anterior chamber depth (ACD) with better resolution has been made possible by the use of ultrasound biomicroscopy (UBM). The resolution of UBM is much higher than that of conventional ultrasound. However, although intraobserver reproducibility of its quantitative measurements was reported to be good, interobserver reproducibility was poor, and observer experience was reported to influence the measurements . Noncontact methods, reported to provide accurate, repeatable, and comparable ACD measurements, include optical methods such as the Orbscan the Pentacam Comprehensive Eye scanner , partial coherence interferometry methods such as the IOL-Master, and optical coherence tomography (OCT) technology ,.
Previous studies using A-scan ultrasonography or UBM have shown that phacoemulsification with or without IOL implantation results in widening of the ACA and deepening of the anterior chamber in both normal and glaucomatous eyes . Furthermore, these changes have been reported to be accompanied by a significant decrease in IOP in these eyes.
The aim of the present study was to evaluate the effect of phacoemulsification on IOP and anterior chamber parameters in patients with cataract without glaucoma.
| Patients and methods|| |
From May 2018 to August 2018, 100 eyes of 76 patients undergoing senile cataract phacoemulsification and IOL implantation were investigated. A total of 27 males (46 affected eyes) and 49 females (54 affected eyes) were included in the study. The mean patients’ age was 65.8±8.3 years (range, 50–81 years).
Preoperatively, in addition to conventional visual acuity, refraction, keratometry, anterior segment assessment, and fundus examination, the IOP of all patients was measured using applanation tonometer before surgery. The Pentacam (Pentacam CES; Oculus GmbH, Wetzlar, Germany) was used to study the anterior chamber parameters before the surgical intervention planned. All patients signed a written informed consent to participate in the study and for publication of data before enrollment in the study. The study was approved by the Ethical Committee of Alexandria Faculty of Medicine.
All surgeries were performed by the same surgeon (T.H.). Routine phacoemulsification was performed in all patients. The artificial IOL (Acrisof, Alcon Laboratories, Fort Worth, Texas, USA) was implanted into the capsular bag.
The postoperative examination included slit-lamp examination of the anterior segment, keratometry, uncorrected visual acuity, and best-corrected visual acuity and refraction, both manual and subjective. The follow-up was conducted at 1 day, 1 week, and 1 month after surgery to measure the IOP. On the final visit, the ACA, volume, and depth of the operated eyes were checked for all cases using the Pentacam. The study was a short-term one, as the studied parameters were fairly stable rapidly after uneventful phacoemulsification surgery; hence, there was no need for a long-term study.
The analysis was carried out with the use of variance, bivariate Pearson’s correlation coefficient, multivariate linear regression techniques, and nonlinear regression models and the coefficient of determination (r2) was calculated.
| Results|| |
The mean preoperative IOP was 15.24±7.05 mmHg. The mean preoperative ACD was 3.1±0.8 mm. The mean preoperative ACA was 34.1±9.3°, and the mean preoperative anterior chamber volume (ACV) was 161.3±36.7 mm3. The mean power of IOL used during surgeries was 22.6±1 D ([Table 1]).
|Table 1 Mean preoperative and postoperative anterior chamber and iridocorneal angle parameters|
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The mean IOP was 11.83±3.75 mmHg 1 month after surgery. The difference between the IOP before surgery and 1 month after surgery was statistically significant (t=6.259, P<0.01).
The mean postoperative ACV and ACD were statistically significantly increased when compared with the corresponding preoperative values (P<0.001 and 0.001, respectively, paired t test). The mean postoperative ACA values measured were also significantly increased compared with the preoperative values (P=0.003, paired t test, [Table 1]).
The lower the chamber volume, the shallower the anterior chamber, or narrower the chamber angle preoperatively, the more significant were the increases in the ACV, ACD, and ACA postoperatively (P=0.006, 0.043, and 0.001, respectively, one-way analysis of variance). [Figure 1] demonstrates the correlation between the preoperative and postoperative values for the ACV. [Figure 2] demonstrates the correlation between the preoperative and postoperative values for the ACD. [Figure 3] demonstrates the correlation between the preoperative and postoperative values for the ACA.
|Figure 1 Anterior chamber volume (ACV): correlation between preoperative and postoperative values.|
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|Figure 2 Anterior chamber depth (ACD): correlation between preoperative and postoperative values.|
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|Figure 3 Anterior chamber angle (ACA): correlation between preoperative and postoperative values.|
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| Discussion|| |
Glaucoma has become the second most prevalent cause of blindness and the primary cause of irreversible blindness . Previous studies have confirmed that the damaging effects of PACG occur more rapidly and are more severe than those of primary open-angle glaucoma . In China, PACG is estimated to cause unilateral blindness (visual acuity <3/60 or visual field ≤10°) in 1.5 million individuals and bilateral blindness in another 1.5 million . Elevated IOP caused by the lens element is a primary reason for these types of blindness. With cataract development, the lens thickness and volume increases. The lens also moves forwards, which is known as a predominant risk factor for pupillary block, during this process. Removal of the lens may effectively prevent the pathogenesis of angle closure glaucoma .
The results of the current study revealed that a simple phacoemulsification cataract surgery may significantly increase the ACD and thus lower the IOP. Following successful phacoemulsification surgery with capsular bag implantation of the IOL results in a reduced lens thickness and significantly changes the ACD. Several studies have interpreted the mechanism of phacoemulsification and IOP reduction, including the pupillary block relief, iris-lens diaphragm posterior shift, ACA widening, and peripheral anterior synechiae reopening. Johnstone  proposed a new mechanism of aqueous drainage and IOP. He indicated that the active expansion and retraction of the trabecular meshwork with IOP caused various fluctuations, including blinking and eye movement. The combined Schlemm’s tube within the valve forms a mechanical aqueous drainage pump system, which provides short-term and long-term stability regulations for IOP . With the collapse and hardening of the Schlemm’s and trabecular meshwork tube, the aqueous drainage pumps gradually fail. Thus, the amount of fluid pulsed into the aqueous veins decreases. The lens gradually thickens and the relative position of the lens front surface moves forward, the trabecular meshwork and Schlemm’s tube pressure increases, and aqueous drainage pump failure increases. Johnstone  considered that the failure of the aqueous drainage pump is due to scleral and ciliary muscle attachment. Phacoemulsification and IOL implantation significantly decreases the space occupied by the lens in the anterior segment. Thus, the front surface of the lens moves backward, the ciliary muscle relaxes and returns to its physiological position, the trabecular meshwork and Schlemm’s tube stretch, and the aqueous drainage pump function is restored. MRI has been used to visualize the anterior segment aqueous drainage pumps to validate this theory. Phacoemulsification imaging studies have shown that the anatomical location of the aqueous drainage pump changes in all ages, as well as the recovery process following cataract surgery . Our clinical observations suggest that phacoemulsification may cause the ACD to be increased and the physiological aqueous drainage pump recovers the anatomical position once aqueous drainage function is restored.
Small incision phacoemulsification may effectively reduce the IOP, deepen the anterior chamber, open the angle, and restore the patient’s visual function. Glaucoma medications may also be reduced. However, a number of patients may forego antiglaucoma surgery and trabeculectomy surgery to avoid complications, such as excessive filtration, hypotony, shallow anterior chamber, corneal endothelial damage, cystoid macular edema, choroidal leakage, bleeding or scarring of the bleb, and poor IOP control, before surgery .
In the present study, the IOP of the patients and the changes in their central ACD before surgery and 1 day after surgery demonstrated no differences. This finding may be related to surgical damage to the blood aqueous barrier, mechanical injury, inflammation of the iris, or a surgical residual viscoelastic response of the IOP caused by temporary factors. Within 1 week of surgery, the IOP of the patients had decreased significantly compared with their values before surgery. The method currently used as a standard treatment for PAC acute cases is laser peripheral iridotomy. A randomized study revealed that after 18 months of continuous follow-up, compared with laser peripheral iridotomy, the effect of cataract phacoemulsification and IOL implantation was more precise in controlling the IOP . Our observations also confirmed that phacoemulsification and IOL implantation controlled the effect of cataract-associated IOP and decreased the range of IOP. Intraocular inflammation requires effective control following surgery to avoid serious reaction.
In a previous study, the preoperative ACD was 2.28±0.32 mm. Postoperatively, the ACD was increased to 3.04±0.39 mm, and the angle was greater than 200°, with no possibility of angle closure glaucoma , which was consistent with the study of Cekic et al. . Filtering surgery had been recommended for eyes with peripheral anterior synechiae of more than 180°. However, for the present study group cases, we considered that cataract plays an important role in the development of angle closure. Phacoemulsification and IOL implantation remove the triggers of lens expansion, deepen the anterior chamber following surgery, open the angle, increase the functionality of the trabecular meshwork, and decrease the IOP . Patients who use drugs for the effective control of IOP may use this method as a safe and effective surgical choice.
The Pentacam is an easy-to-use, noncontact biometry system that uses a Scheimpflug rotating camera for the analysis of the anterior segment. The measurements taken by the system are fast and user independent. Recently, Pentacam has been reported to calculate ACD, with a mean SD of 20 µm in healthy eyes . We demonstrated significant deepening of the anterior chamber and opening of the iridocorneal angle, with a resultant increase in ACV at 1 month after surgery. Mean ACV increased 1.22 times, mean ACD increased 1.34 times, and mean ACA increased 1.23 times. Moreover, quantitatively documenting the widening of the iridocorneal angle, we also noted an obvious backward shift of the iris in the Scheimpflug images, especially in eyes with very shallow anterior chamber. Marked anterior chamber changes have been reported following cataract surgery with phacoemulsification and foldable IOL implantation, using A-scan ultrasonography, UBM, and Scheimpflug photography . Using UBM, Kurimoto et al.  reported that the anterior chamber was 1.37 times deeper and the temporal ACA was 1.57 times wider at 3 months after surgery . Another UBM study  reported the ACD to increase 1.31 times and the angle to widen 1.26, 1.53, 1.36, and 1.52 times temporally, nasally, superiorly, and inferiorly, respectively. Both the latter studies attributed the anterior chamber changes to be owing to a backward shift of the iris with ∼10° angular movement after crystalline lens removal and the relief of possible accompanying relative pupillary block in eyes with a shallow anterior chamber. Hayashi et al.  demonstrated that ACA and ACD at the vertical axis increased significantly after phacoemulsification and IOL implantation in eyes with angle closure glaucoma, open-angle glaucoma, and in normal eyes. Documented changes in the anterior chamber parameters following phacoemulsification and foldable IOL implantation have been reported to be accompanied by significant decreases in IOP in several studies in both normotensive eyes and in eyes with open-angle glaucoma  or angle closure glaucoma .
Limitations of the Pentacam CES Scheimpflug technique for ACA imaging include light scattering at the angle region, which may lead to reduced visualization of the angle structures and therefore might increase the risk of measurement errors. Further refinements in instrumentation may improve such limitations .
| Conclusion|| |
The present study, performed with the Pentacam rotating Scheimpflug camera system, confirmed that in normotensive eyes with open iridocorneal angles, the ACV and ACD increased and the ACA widened in the studied patients following uneventful phacoemulsification and IOL implantation. These changes were accompanied by a significant decrease in IOP 1 month postoperatively. Further studies are required to prove the safety and mechanism of lowering IOP following phacoemulsification.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]