ORIGINAL STUDY
Surgically Induced Astigmatism Following Glaucoma Surgery in Egyptian Patients Heba M. A. El-Saied, MD, Pakinam H. Foad, MD, Mohamed A. Eldaly, MD, FRCS (Glasg), and Mohamad A. S. E. Abdelhakim, MD
Purpose: The altered visual function induced by changes in corneal curvature following filtration surgery is distressing to patients. The aim of this study was to evaluate surgically induced astigmatism following trabeculectomy in comparison with deep sclerectomy. Methods: In a prospective interventional comparative study, patients with primary open-angle glaucoma were randomly allocated to either group A or B; deep sclerectomy with mitomycin C 0.2 mg/mL and trabeculectomy with mitomycin C 0.2 mg/mL, respectively. Keratometry was performed using Topcon KR-7000P autokerato-refractometer preoperatively and at 6 months postoperatively. Vector analysis was used to analyze the surgically induced astigmatism. Results: Sixty eyes of 45 patients in group A, and 60 eyes of 42 patients in group B were enrolled for vector analysis. The mean preoperative astigmatic vector power was 0.49 ± 1.65 D and + 0.47 ± 2.18 D in groups A and B, respectively. The mean postoperative astigmatic vector power was 1.14 ± 1.55 D in group A and 0.35 ± 1.8 D in group B. The mean change in astigmatic vector powers was 0.67 ± 1.63 D in group A and 0.82 ± 2.0 D in group B. When compared with preoperative data in either group, the differences were significant, P = 0.001 & 0.007 in groups A and B respectively, whereas the postoperative difference between either group was insignificant (P = 0.723). A total of 40% of corneas got flatter in group B compared with 25% in group A, P = 0.057. Conclusions: Both trabeculectomy and deep sclerectomy induced considerable postoperative astigmatism. A longer follow-up period is recommended to study the different patterns of astigmatism in either procedure. Key Words: trabeculectomy, deep sclerectomy, keratometry, astigmatic vector
(J Glaucoma 2014;23:190–193)
T
rabeculectomy remains the standard surgical procedure for glaucoma when medical and laser treatments fail to control intraocular pressure (IOP). However, many authors have stated that nonpenetrating filtering surgeries appear to provide reasonable control of IOP comparable with trabeculectomy.1 Altered visual function induced by changes in corneal curvature following filtration surgery may be distressing for the patient, particularly when changes are marked and
Received for publication March 25, 2013; accepted October 23, 2013. From the Department of Ophthalmology, Kasr El Aini Hospital, Faculty of Medicine, Cairo University, Cairo, Egypt. Disclosure: The authors declare no conflict of interest. Reprints: Mohamad A. S. E. Abdelhakim, MD, 11c, Street 199, Apt. # 9, Degla, Maadi, Cairo 11431, Egypt (e-mail: m.amr.salah@ gmail.com). Copyright r 2013 by Lippincott Williams & Wilkins DOI: 10.1097/IJG.0000000000000035
190 | www.glaucomajournal.com
continue beyond the first few postoperative months.2 In the 1990s, a number of authors have studied the refractive changes induced in the cornea as a result of the procedure.3,4 The aim of this study was to evaluate the astigmatism induced by trabeculectomy in comparison with deep sclerectomy.
METHODS This is a prospective interventional comparative study conducted on 132 eyes of 93 patients. The study was performed during the time between July 2011 and July 2012. Patients were selected from the Kasr Al-Aini Cairo University Hospitals outpatient clinic of Ophthalmology. Kasr Al-Aini hospital is a central university hospital in Cairo, and it is a tertiary referral center for most of the governorates in Egypt. Approval for the study was obtained from the hospital’s ethical committee (according to the WMA Declaration of Helsinki). All patients received a thorough explanation of the study design and aims, and were provided with written informed consent. Inclusion criteria were patients with medically uncontrolled primary open-angle glaucoma, or not tolerating medical therapy, and with clear media. Cases with media opacities interfering with refraction (corneal opacities, cataract, or vitreous opacities), and other glaucomas, including; angle closure glaucoma, congenital glaucoma, uveitic glaucoma, and neovascular glaucoma, were excluded from the study. Furthermore, patients with corneal ectatic conditions or previous laser refractive surgery and pseudophakic eyes were excluded. In addition, we excluded patients who were unfit for general anesthesia to obviate the effect of local anesthesia on wound healing. Postoperatively, eyes which developed postoperative cataract or required suture manipulations were excluded from analysis. The enrolled patients randomly allocated using computer-generated numbers to either group A or B. In group A; they were operated for deep sclerectomy with mitomycin C (MMC) 0.2 mg/mL, whereas group B was trabeculectomy with MMC 0.2 mg/mL. The 8 eyes that developed mild cortical cataract and the 4 eyes that required suture manipulation in group B were excluded from analysis after enrollment in group B, whereas all eyes in group A were intention-to-treat. All the patients received complete ophthalmological examination, including; measurement of the best corrected visual acuity, refractive status (sphere and cylinder), slitlamp examination, IOP measurement with Goldmann applanation tonometry, dilated fundus examination, gonioscopy for angle grading using Schaeffer’s method, Humphery SITA standard perimetry to assess the field of vision, and corneal pachymetry. J Glaucoma
Volume 23, Number 3, March 2014
J Glaucoma
Volume 23, Number 3, March 2014
The location of the surgical site, whether for trabeculectomy or deep sclerectomy was the same. We selected the upper temporal quadrant for all eyes. That was at 10 o’clock (110-degree meridian) if it was right eye and 2 o’clock (70-degree meridian) for the left. This was achieved preoperatively at the slit-lamp, in a sitting position (to obviate the torsion effect of the oblique muscles in supine position), where the desired corneal meridian was marked with a sterile marker. All surgeries were performed under general anesthesia, with a fornix-based conjunctival flap. In deep sclerectomy with MMC: a rectangular (4 3 mm) superficial scleral flap half of the sclera thickness was fashioned. Subsequently, MMC (0.2 mg/mL) was applied under the scleral flap and the conjunctiva for 3 minutes, and then it was washed. The deep flap was fashioned then excised. Deroofing of Schlemm’s canal was followed by peeling of the juxtacanalicular meshwork with blunt tipped forceps. The superficial scleral flap was then replaced using two 10/0 nylon sutures at its corners, and the conjunctiva was closed using two 8/0 virgin silk sutures at either end of the conjunctival flap. In trabeculectomy with MMC, a rectangular (4 3 mm) superficial scleral flap half of the sclera thickness was fashioned. Subsequently, MMC (0.2 mg/mL) was applied under the scleral flap and the conjunctiva for 3 minutes, and after that it was washed. Excision of trabecular meshwork block (2 1 mm) by vannas scissors was followed by peripheral iridectomy then replacing the scleral flap using two 10/0 nylon sutures at its corners. Finally, the conjunctiva was closed using two 8/0 virgin silk sutures at either end. All the patients were examined on the first day postoperatively, after 1 week and then monthly for 6 months. Examination involved measurement of the BCVA, refractive status (sphere and cylinder), slit-lamp examination, and IOP measurement with Goldmann applanation tonometry. In addition, Humphery SITA standard perimetry to assess the field of vision was performed at 3- and 6-month postoperatively. Keratometry using the Topcon KR-7000P autokerato-refractometer, was performed preoperatively and after 6 months postoperatively. It was performed by the same person, who was masked with respect to previous data. Reproducibility analysis of 10 measurements for each eye at each time was performed. After each single measurement, the patient was asked to sit back away from the machine to simulate a separate examination episode. The first scan acted as the baseline and all other scans were compared with it, resulting in 9 “induced vectors” to analyze and decompose. Vector analysis was performed through vector decomposition,5 which provided a mathematical expression to the change in astigmatism, whether steepening or flattening along the vertical meridian taking the surgical incision as a start point. We used simple (m) cos (x) functions, multiplied by the scalar magnitude, in this case the astigmatic magnitude in diopters (m), to decompose the astigmatism by algebraic vector theorem at meridian (x).6 This resulted in the magnitude of change of steepening and flattening for each eye. Postoperative data were compared with the preoperative data set in either group and the astigmatic change in group A was compared with group B. Data were statistically described in terms of range, mean ± SD, median frequencies (number of cases), and percentages when appropriate. Comparison of numeric variables between the study groups was done using MannWhitney test for independent samples, whereas withinr
2013 Lippincott Williams & Wilkins
Astigmatism Following Glaucoma Surgery
group comparison of numeric variables was performed using the Wilcoxon Signed-Rank test. Correlation between variables was carried out using Spearman rank correlation equation for non-normal variables. w2 test was performed for comparing categorical data. All P values
Surgically Induced Astigmatism Following Glaucoma Surgery in Egyptian Patients Heba M. A. El-Saied, MD, Pakinam H. Foad, MD, Mohamed A. Eldaly, MD, FRCS (Glasg), and Mohamad A. S. E. Abdelhakim, MD
Purpose: The altered visual function induced by changes in corneal curvature following filtration surgery is distressing to patients. The aim of this study was to evaluate surgically induced astigmatism following trabeculectomy in comparison with deep sclerectomy. Methods: In a prospective interventional comparative study, patients with primary open-angle glaucoma were randomly allocated to either group A or B; deep sclerectomy with mitomycin C 0.2 mg/mL and trabeculectomy with mitomycin C 0.2 mg/mL, respectively. Keratometry was performed using Topcon KR-7000P autokerato-refractometer preoperatively and at 6 months postoperatively. Vector analysis was used to analyze the surgically induced astigmatism. Results: Sixty eyes of 45 patients in group A, and 60 eyes of 42 patients in group B were enrolled for vector analysis. The mean preoperative astigmatic vector power was 0.49 ± 1.65 D and + 0.47 ± 2.18 D in groups A and B, respectively. The mean postoperative astigmatic vector power was 1.14 ± 1.55 D in group A and 0.35 ± 1.8 D in group B. The mean change in astigmatic vector powers was 0.67 ± 1.63 D in group A and 0.82 ± 2.0 D in group B. When compared with preoperative data in either group, the differences were significant, P = 0.001 & 0.007 in groups A and B respectively, whereas the postoperative difference between either group was insignificant (P = 0.723). A total of 40% of corneas got flatter in group B compared with 25% in group A, P = 0.057. Conclusions: Both trabeculectomy and deep sclerectomy induced considerable postoperative astigmatism. A longer follow-up period is recommended to study the different patterns of astigmatism in either procedure. Key Words: trabeculectomy, deep sclerectomy, keratometry, astigmatic vector
(J Glaucoma 2014;23:190–193)
T
rabeculectomy remains the standard surgical procedure for glaucoma when medical and laser treatments fail to control intraocular pressure (IOP). However, many authors have stated that nonpenetrating filtering surgeries appear to provide reasonable control of IOP comparable with trabeculectomy.1 Altered visual function induced by changes in corneal curvature following filtration surgery may be distressing for the patient, particularly when changes are marked and
Received for publication March 25, 2013; accepted October 23, 2013. From the Department of Ophthalmology, Kasr El Aini Hospital, Faculty of Medicine, Cairo University, Cairo, Egypt. Disclosure: The authors declare no conflict of interest. Reprints: Mohamad A. S. E. Abdelhakim, MD, 11c, Street 199, Apt. # 9, Degla, Maadi, Cairo 11431, Egypt (e-mail: m.amr.salah@ gmail.com). Copyright r 2013 by Lippincott Williams & Wilkins DOI: 10.1097/IJG.0000000000000035
190 | www.glaucomajournal.com
continue beyond the first few postoperative months.2 In the 1990s, a number of authors have studied the refractive changes induced in the cornea as a result of the procedure.3,4 The aim of this study was to evaluate the astigmatism induced by trabeculectomy in comparison with deep sclerectomy.
METHODS This is a prospective interventional comparative study conducted on 132 eyes of 93 patients. The study was performed during the time between July 2011 and July 2012. Patients were selected from the Kasr Al-Aini Cairo University Hospitals outpatient clinic of Ophthalmology. Kasr Al-Aini hospital is a central university hospital in Cairo, and it is a tertiary referral center for most of the governorates in Egypt. Approval for the study was obtained from the hospital’s ethical committee (according to the WMA Declaration of Helsinki). All patients received a thorough explanation of the study design and aims, and were provided with written informed consent. Inclusion criteria were patients with medically uncontrolled primary open-angle glaucoma, or not tolerating medical therapy, and with clear media. Cases with media opacities interfering with refraction (corneal opacities, cataract, or vitreous opacities), and other glaucomas, including; angle closure glaucoma, congenital glaucoma, uveitic glaucoma, and neovascular glaucoma, were excluded from the study. Furthermore, patients with corneal ectatic conditions or previous laser refractive surgery and pseudophakic eyes were excluded. In addition, we excluded patients who were unfit for general anesthesia to obviate the effect of local anesthesia on wound healing. Postoperatively, eyes which developed postoperative cataract or required suture manipulations were excluded from analysis. The enrolled patients randomly allocated using computer-generated numbers to either group A or B. In group A; they were operated for deep sclerectomy with mitomycin C (MMC) 0.2 mg/mL, whereas group B was trabeculectomy with MMC 0.2 mg/mL. The 8 eyes that developed mild cortical cataract and the 4 eyes that required suture manipulation in group B were excluded from analysis after enrollment in group B, whereas all eyes in group A were intention-to-treat. All the patients received complete ophthalmological examination, including; measurement of the best corrected visual acuity, refractive status (sphere and cylinder), slitlamp examination, IOP measurement with Goldmann applanation tonometry, dilated fundus examination, gonioscopy for angle grading using Schaeffer’s method, Humphery SITA standard perimetry to assess the field of vision, and corneal pachymetry. J Glaucoma
Volume 23, Number 3, March 2014
J Glaucoma
Volume 23, Number 3, March 2014
The location of the surgical site, whether for trabeculectomy or deep sclerectomy was the same. We selected the upper temporal quadrant for all eyes. That was at 10 o’clock (110-degree meridian) if it was right eye and 2 o’clock (70-degree meridian) for the left. This was achieved preoperatively at the slit-lamp, in a sitting position (to obviate the torsion effect of the oblique muscles in supine position), where the desired corneal meridian was marked with a sterile marker. All surgeries were performed under general anesthesia, with a fornix-based conjunctival flap. In deep sclerectomy with MMC: a rectangular (4 3 mm) superficial scleral flap half of the sclera thickness was fashioned. Subsequently, MMC (0.2 mg/mL) was applied under the scleral flap and the conjunctiva for 3 minutes, and then it was washed. The deep flap was fashioned then excised. Deroofing of Schlemm’s canal was followed by peeling of the juxtacanalicular meshwork with blunt tipped forceps. The superficial scleral flap was then replaced using two 10/0 nylon sutures at its corners, and the conjunctiva was closed using two 8/0 virgin silk sutures at either end of the conjunctival flap. In trabeculectomy with MMC, a rectangular (4 3 mm) superficial scleral flap half of the sclera thickness was fashioned. Subsequently, MMC (0.2 mg/mL) was applied under the scleral flap and the conjunctiva for 3 minutes, and after that it was washed. Excision of trabecular meshwork block (2 1 mm) by vannas scissors was followed by peripheral iridectomy then replacing the scleral flap using two 10/0 nylon sutures at its corners. Finally, the conjunctiva was closed using two 8/0 virgin silk sutures at either end. All the patients were examined on the first day postoperatively, after 1 week and then monthly for 6 months. Examination involved measurement of the BCVA, refractive status (sphere and cylinder), slit-lamp examination, and IOP measurement with Goldmann applanation tonometry. In addition, Humphery SITA standard perimetry to assess the field of vision was performed at 3- and 6-month postoperatively. Keratometry using the Topcon KR-7000P autokerato-refractometer, was performed preoperatively and after 6 months postoperatively. It was performed by the same person, who was masked with respect to previous data. Reproducibility analysis of 10 measurements for each eye at each time was performed. After each single measurement, the patient was asked to sit back away from the machine to simulate a separate examination episode. The first scan acted as the baseline and all other scans were compared with it, resulting in 9 “induced vectors” to analyze and decompose. Vector analysis was performed through vector decomposition,5 which provided a mathematical expression to the change in astigmatism, whether steepening or flattening along the vertical meridian taking the surgical incision as a start point. We used simple (m) cos (x) functions, multiplied by the scalar magnitude, in this case the astigmatic magnitude in diopters (m), to decompose the astigmatism by algebraic vector theorem at meridian (x).6 This resulted in the magnitude of change of steepening and flattening for each eye. Postoperative data were compared with the preoperative data set in either group and the astigmatic change in group A was compared with group B. Data were statistically described in terms of range, mean ± SD, median frequencies (number of cases), and percentages when appropriate. Comparison of numeric variables between the study groups was done using MannWhitney test for independent samples, whereas withinr
2013 Lippincott Williams & Wilkins
Astigmatism Following Glaucoma Surgery
group comparison of numeric variables was performed using the Wilcoxon Signed-Rank test. Correlation between variables was carried out using Spearman rank correlation equation for non-normal variables. w2 test was performed for comparing categorical data. All P values
