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ORIGINAL ARTICLE
Year : 2020  |  Volume : 33  |  Issue : 2  |  Page : 546-550

The role of preoperative Pentacam in optimizing visual outcome after cataract surgery


1 Department of Ophthalmology, Faculty of Medicine, Menoufia University, Shebeen El-Kom, Egypt
2 Department of Ophthalmologylogy, Ministry of Health, Damietta, Egypt

Date of Submission22-Dec-2018
Date of Decision19-Jan-2019
Date of Acceptance20-Feb-2019
Date of Web Publication27-Jun-2020

Correspondence Address:
Fatma A. A. Shakal
Kafr Elbatikh, Damietta
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/mmj.mmj_421_18

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  Abstract 


Objective
To evaluate the role of preoperative Pentacam in optimizing visual outcome after cataract surgery.
Background
It has been suggested that Pentacam gives comprehensive data about preoperative astigmatism, lens density, and refractive power helping in optimizing the visual outcome after cataract surgery.
Patients and methods
Preoperatively, the patients were subjected to careful history taking, thorough ocular examination including assessment of manifest refraction, measurement of logMAR uncorrected distance visual acuity, and corrected distance visual acuity, biometry and keratometry with the Intraocular lens (IOL) Master partial coherence interferometry device, corneal topography (Pentacam) and to exclude irregular astigmatism, mean lens density, and cataract grading score were evaluated. Slit lamp examination, dilated funduscopy under pharmacological, intraocular pressure, and Hoffer Q formula was used in eyes with an axial length shorter than 22 mm, and SRK/T formula was used for all other cases. Cataract surgery were performed according to the standard protocols. Postoperative manifest refraction (sphere and cylinder) and visual acuity (uncorrected and corrected) were obtained.
Results
There was significant improvement of astigmatism postoperatively. Also, there were significant improvements of UCVA and BCVA in postoperative assessment as compared with preoperative evaluation.
Conclusion
Preoperative Pentacam can help in the improvement of preoperative astigmatism. It also resulted in the improvement of Uncorrected visual acuity (UCVA) and Best corrected visual acuity (BCVA).

Keywords: astigmatism, cataract, densitometry, Pentacam, visual outcome


How to cite this article:
Sarhan AE, Elhagaa AA, Shakal FA. The role of preoperative Pentacam in optimizing visual outcome after cataract surgery. Menoufia Med J 2020;33:546-50

How to cite this URL:
Sarhan AE, Elhagaa AA, Shakal FA. The role of preoperative Pentacam in optimizing visual outcome after cataract surgery. Menoufia Med J [serial online] 2020 [cited 2020 Jul 16];33:546-50. Available from: http://www.mmj.eg.net/text.asp?2020/33/2/546/287803




  Introduction Top


Cataracts are a major cause of blindness worldwide, affecting almost 18 million people[1]. Fortunately, the visual impairment caused by cataract is reversible in the majority of patients after surgery[2]. Thus the assessment, grading, and classification of cataract stage and the evaluation of cataract progression are vital, as they help both eye care providers and to optimize patients' visual outcome after a cataract surgery[3].

There are multiple subjective and objective methods used to assess cataracts, for example, the Lens Opacities Classification System III, the Visual Function Index-14, double-pass retinal images recording and analyzing, and the one widely used objective method is Scheimpflug imaging (Pentacam), which assesses cataracts by analyzing the lens density[3].

The Pentacam is a family of instruments that perform corneal tomography using a rotating Scheimpflug camera. The Pentacam offers evaluation of the entire anterior segment from the anterior corneal surface to the posterior lens surface using a rotating Scheimpflug camera[4].

The captured images of the anterior eye segment are used to create a precise, three-dimensional view, and use the digitally acquired data to evaluate the parameters of the lens, cornea, and the anterior chamber which in turn help in optimizing the outcome of cataract surgery[5].

The Pentacam is a multipurpose instrument that is capable of external ocular photography, corneal pachymetry, corneal topography, densitometry, and anterior chamber analysis. The oculus Pentacam provides the user with the ability to view, photograph, and measure the anterior segment of the eye without invasive operation or direct contact with the eye[6].

For calculating corneal thickness, the camera measures from the top of the epithelium to the anterior surface of the endothelium. Importantly, it does not measure the tear film. The corneal thickness is displayed as a color image and can be evaluated at any particular location by clicking on the area or by using the numerical function[7].

Pentacam accurately measures the global corneal astigmatism, quantifies the nature of the astigmatism (i.e., symmetric -bow tie- vs. asymmetric or irregular astigmatism) and identifies the steep meridian of astigmatism and accordingly aids in the decision making for correction of astigmatism[8],[9].

The Pentacam provides a comprehensive, precise, and valid measurement of corneal power and optical aberrations, which allows the ophthalmologist to make better decisions regarding the intraocular lens design and power[10].

Opacification of the crystalline lens can be quantitatively imaged and analyzed using the Pentacam. The grading of lens density through Scheimpflug images has been found to correlate well with the Lens Opacification Classification System III grading system for cataracts. This densitometry helps in choosing the power modality during phacoemulsification. It is also an excellent tool for identifying intralenticular foreign bodies[11].

The Pentacam is useful in the assessment of patients after cataract surgery as in cases of posterior capsular opacification and intraocular lens dislocation[12].

The aim of this study was to evaluate the role of preoperative Pentacam in optimizing visual outcome after cataract surgery.


  Patients and Methods Top


A total of 50 cataract patients with preoperative corneal astigmatism were assessed between 0.5 and 2.50 diopters (D), aged 48–79 years, at the International Eye Hospital in Damietta between March 2017 and June 2018. All patients were adequately informed and signed a consent form before surgery after they had received an explanation about the nature of the study and its potential complications. This study was approved by the local ethics committee. All the procedures were in accordance with the ethical standards of the responsible committee on human experimentation. Inclusion criteria were age older than 40 years and visually significant cataract (best corrected visual acuity worse than 0.5 immature senile and posterior subcapsular cataract detected by slit lamp, lens densitometry from 0 to 4 detected by Pentacam), regular corneal astigmatism between 0.5 and 2.00 D, and pharmacologic mydriasis of at least 6.0 mm to allow proper intraoperative visualization. The following were the exclusion criteria: previous intraocular surgery in the eye, pterygium, ocular disease that would lead to poor postoperative corrected visual acuity (corneal scarring, uveitis, advanced glaucoma, neuro-ophthalmic disease, significant macular disease, or other retinopathy), zonule or pupil abnormalities and any irregular corneal astigmatism. Preoperatively, the patients were subjected to careful history taking, thorough ocular examination including assessment of manifest refraction, measurement of uncorrected distance visual acuity, and corrected distance visual acuity; biometry and keratometry with the IOL Master partial coherence interferometry device (Carl Zeiss Meditec AG, Jena, Germany Abbott Medical Optics Inc., Santa Ana, CA, USA), corneal topography (Pentacam, OCULUS, Inc., Arlington, WA, USA) to exclude irregular astigmatism, and mean lens density, cataract grading score were evaluated. Slit lamp examination, intraocular pressure measurement, and dilated funduscopy under pharmacological mydriatic eye drops were done. The Hoffer Q formula was used in eyes with an axial length shorter than 22 mm, and SRK/T formula was used for all other cases. Assessment of corneal astigmatism was done by identifying the steepest corneal meridian and using it as a site for clear corneal incision. In cases with the amount of topographic corneal astigmatism more than 2 D, an opposite clear corneal incision had been added. Cataract surgery was performed with phacoemulsification, followed by IOL implantation into the capsular bag using the Unfolder Platinum 1 system (Abbott Medical Optics Inc.). In the postoperative period, patients were given an eye drop combination of moxifloxacin and dexamethasone four times daily for a week and, then prednisolone four times daily tapered throughout another 3 weeks. Postoperative manifest refraction (sphere and cylinder) and visual acuity (uncorrected and corrected) were obtained. Statistical analyses in this study were performed by using SPSS software version 18.0 (SPSS Inc., Chicago, Illinois, USA). Continuous data were expressed in the form of mean ± SD, while categorical data were expressed in the form of count and percent. Comparison of continuous data were performed utilizing Student's t-test, while categorical data were done using χ2-test. A P value less than 0.05 was considered statistically significant.


  Results Top


The studied patients had a mean age of 56.4 ± 7.6 years. There were 28 (56.0%) women and 22 (44.0%) men. Fundus examination revealed that 18% of patients have early D changes (dot and blot hemorrhages). The most common type of cataract was immature senile cataract (38%). The mean of K reading was 45.2 ± 3.6 and the mean of the steepest corneal axis was 97.7 ± 47.39 [Table 1]. In this study, the preoperative data of the patients included showed that the mean astigmatism was 1.12 ± 0.46 D and the postoperative data of patients included for phacoemulsification through clear corneal incision showed that the mean astigmatism was 0.54 ± 0.38 D. [Table 2] shows significant improvement of astigmatism postoperatively (P = 0.0003). Also, the operated patients with phacoemulsification through clear corneal incision showed that the achieved visual acuity was as good as or better than that preoperatively with correction. There were significant improvement of UCVA and BCVA in the postoperative assessment as compared with preoperative evaluation (P = 0.003) ([Table 3] and [Table 4]).
Table 1: Basic data of the studied patients

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Table 2: Comparison between preoperative and postoperative astigmatism in the studied patients

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Table 3: Comparison between preoperative and postoperative visual outcome in the studied patients

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Table 4: Postoperative change in UCVA and BCVA

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  Discussion Top


There is an increased demand for objective methods that can measure a cataract's impact on vision, to improve our sensitivity in identifying those patients whose quality of life can be markedly improved with cataract surgery[13]. The distinct assessment methods need to be integrated with clinical data, such as visual function and functional impairment tests, to clarify the impact of the cataract on patient's visual status or functional ability[3],[14]. Visual acuity is the standard measurement of visual function in cataract patients. Nevertheless, cataract patients may present relatively good visual acuity but still complain of poor vision. It has been suggested that visual acuity provides an inaccurate assessment of vision in these patients and other tests should be used to clarify the status of the crystalline lens[15]. Pentacam accurately measures global corneal astigmatism, quantifies the nature of the astigmatism (i.e. symmetric -bow tie- vs. asymmetric or irregular astigmatism), and identifies the steep meridian of astigmatism and accordingly aids in the decision making for correction of astigmatism. Also, it is useful in the assessment of postcataract surgery patients as in cases of posterior capsular opacification and intraocular lens dislocation[8],[9]. This is a prospective study aimed to evaluate the role of preoperative Pentacam in optimizing visual outcome after cataract surgery. A total of 50 eyes in 50 patients were enrolled in this study and were followed up preoperatively and postoperatively. The age distribution of the patients showed that the majority were between the ages of 48 and 79 years with mean age at the time of surgery being 56.4 ± 7.6 years. This age distribution is in conformity with what is seen in cataract patients in the study reported by Adepoju et al.[16] who found a mean age of 58.2 years. A similar age range have also been reported in other studies[17]. However, Nwosu et al.[18] found a mean age of 66.1 years and Bekibele[19] found a mean age of 64 years. There were more women (56%) than men (44%) in this study. However, several studies have found a male preponderance among cataract patients presenting to the eye clinics as in the study by Adepoju et al.[16]. No significant statistical difference was recorded between patients regarding age and sex. No perioperative complications were noted. Furthermore, none of the eyes shifted from phacoemulsification to extracapsular cataract extraction intraoperatively. However, Jackson and Glasser[20] reported that posterior capsular tear may occur as intraoperative complications in up to 15% of surgeries among junior surgeons but is uncommon (<1%) among experienced surgeons; also posterior capsular opacification is a more common postoperative complication which occurs in less than 10% at 2 years postsurgically[21]. This study revealed that the highest prevalence of cataract is immature senile cataract (38%) slit-lamp examination, while that of complicated and mature cataract are the minimum and their prevalence is 2%. These agree with Avachat et al.[22] who reported that senile cataract was the most common cause (53.85%), while traumatic and congenital cataract were the least common (3.8%). Corneal astigmatism after phacoemulsification surgery depends on the type, location, and configuration of cataract incision and presence or absence of wound suture[23]. During cataract surgery it is possible to reduce the pre-existing astigmatism by modifying the length, shape, type, and the localization of the incision[24]. Ferrer-Blasco et al.[21] studied the prevalence of corneal astigmatism before cataract surgery and found that in 13.2% of eyes no corneal astigmatism was present; in 64.4%, corneal astigmatism was between 0.25 and 1.25 D; and in 22.2%, it was 1.50 D or higher. This finding implies that when planning a surgery, both the spherical and the astigmatic components should be considered to achieve postoperative outcomes as close to emmetropia as possible. Improved spherical and astigmatic outcomes are now well-recognized benefits of modern small-incision cataract surgery. Although standard 2.8–3.2 mm phacoemulsification provides satisfactory results in terms of safety, efficiency, and refractive outcomes, studies have shown that microincision cataract surgery – defined as cataract surgery performed through an incision of less than 2 mm is a minimally invasive procedure with increased safety and less postoperative surgically induced astigmatism[25]. In this study assessment of corneal astigmatism was done by identifying the steepest corneal meridian and using it as a site for clear corneal incision. In cases with the amount of topographic corneal astigmatism was more than 2 D, an opposite clear corneal incision had added. The preferred clear corneal incision location was the superior temporal quadrant and the surgeon's estimated surgically induced corneal astigmatism was 0.5 D. Regarding the prevalence of corneal astigmatism in patients before cataract surgery, the data of patients included in our study showed that the preoperative mean astigmatism was 1.12 ± 0.46 D and the majority of the patients (56%) had preoperative astigmatism of 0.5–1 D. The same was reported by Yuan et al.[26] that among all the patients, astigmatism of 0.51–1.00 D was the most common cylinder value, followed by 1.01–1.50 and 0.0–0.50 D. However, they also reported that the results in total (32 eyes, 25.41%) exhibited a corneal astigmatism of 1.5 D or greater[27]. Other studies have shown that a large majority (56%) of patients in this study had preoperative astigmatism in the 0–0.5 D range which is in accordance with the values of the Duke-Elder ophthalmology[28].

In our study, the postoperative data of patients included for phacoemulsification through clear corneal incision has shown that the mean astigmatism was 0.54 ± 0.38 D. On day 30 postoperatively 86% of the operated patients had astigmatism between 0 and 1.0 D while only 14% had an astigmatism of more than 1 D to less than 2 D. This study showed that there was a highly statistically significant difference between preoperative and postoperative astigmatism. In agreement with Khokhar et al.[29] who reported that the mean preoperative and postoperative topographic corneal astigmatism was 2.51 ± 0.92 D (SD) and 0.91 ± 0.54 D, respectively, in group 1 and 2.16 ± 0.80 and 1.57 ± 0.70 D, respectively, in group 2. Mean astigmatic correction was 1.66 ± 0.5 and 0.85 ± 0.75 D in group 1 and group 2, respectively. Mean surgically induced astigmatism, measured by a vector-corrected method, was 1.66 ± 0.50 and 0.85 ± 0.75 D in group 1 and group 2, respectively (insignificant). In conclusion, they reported that a clear corneal incision at the steep corneal axis in cataract patients having phacoemulsification is effective in providing an enhanced effect for correcting the pre-existing corneal astigmatism n cataract surgery. In contrast with Masnec-Paškvalin et al.[30] stated that there was no statistically significant difference between preoperative and postoperative astigmatism. These differences may be due to that the different study sample has different results, also different location as well as the width of the incision affects the degree of postoperative astigmatism. This study found that 92% of the operated patients with phacoemulsification through clear corneal incision revealed that the achieved visual acuity was as good as or better than that preoperatively with correction. In a comparison of preoperative BCVA and (day 30) postoperative BCVA in logMAR in our cases, the BCVA improved for all eyes except for eight (16%) in which the BCVA was unchanged, and only two (4%) cases became worse in visual performance postoperatively. The postoperative visual outcome in this study was same as Ho et al.[27] reported that the preoperative mean UCVA and BCVA was significantly improved, respectively. All eyes had an improved UCVA except for three, including two with no change in UCVA and one with a decrease in UCVA and 92.3% cases achieved visual acuity was as good as or better than that preoperatively with correction. The BCVA improved for all eyes except for four in which the BCVA was unchanged, and one, which lost BCVA postoperatively. The comparatively better visual outcome in our patients than that was reported by Bekibele et al. where he found good vision in 65.5%[19]. It is also better than the best corrected visual acuity (75.4%) reported by Masket and Tennen[23]. These differences in the visual outcome are the result of many factors which include the surgeons' skill, presence of intraoperative and postoperative complications, different follow-up period, and presence of pre-existing ocular pathology.


  Conclusion Top


Preoperative Pentacam results in an improvement of preoperative astigmatism. It also resulted in an improvement of UCVA and BCVA.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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  [Table 1], [Table 2], [Table 3], [Table 4]



 

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