|Year : 2015 | Volume
| Issue : 1 | Page : 197-202
Management of pre-existing regular astigmatism in phacoemulsification
Mostafa Kamal Nassar1, Khaled El-Gonemy Said-Ahmed1, Osamaa Abd-Allah Al-Morsy1, Dina Said Gawish2
1 Department of Ophthalmology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Ophthalmology, Shibin El-Kom Ophthalmology Hospital, Menoufia, Egypt
|Date of Submission||13-Apr-2014|
|Date of Acceptance||11-Jun-2014|
|Date of Web Publication||29-Apr-2015|
Dina Said Gawish
Shibin El-Kom Ophthalmology Hospital, Shibin El-Kom, Menoufia
Source of Support: None, Conflict of Interest: None
The objective of this study was to compare the effect of single clear corneal incision (CCI) on the steep axis with opposite clear corneal incisions (OCCIs) on pre-existing regular corneal astigmatism in cataract patients having phacoemulsification.
Correction of pre-existing regular astigmatism in phacoemulsification.
Patients and methods
This randomized prospective clinical study included 30 eyes of 30 cataract patients with corneal regular astigmatism greater than 1 D. The patients were randomly divided into two groups, each group involving 15 eyes. Paired 3 mm CCI were made on the steep axis in Group A and single in Group B. Preoperative evaluation included uncorrected visual acuity, refraction, best-corrected visual acuity, applanation tonometry, fundus examination, biometry, keratometry, and corneal topography. The vertical axis was marked before peribulbar anesthesia was given and routine phacoemulsification was performed through a 3-mm CCI on the steep axis. An additional opposite 3-mm self-sealing CCI was made opposite to the first one in Group A. Patients were examined 2, 4, and 8 weeks postoperatively. Visual acuity, refraction, keratometry, and corneal topography were used to evaluate the improvement.
The mean preoperative and postoperative topographic corneal astigmatism was 1.95 D ± 0.83 (SD), 0.59 D ± 0.47 (SD) and 1.93 D ± 0.51 (SD), 1.53 D ± 0.62 (SD), respectively, in Groups A and B. There was a significant difference between the mean values of astigmatism in the two groups postoperatively. The mean surgically induced astigmatism, measured by a vector-corrected method, was 1.2 ± 80.11 D and 1.09 ± 0.13 D in Group A and Group B, respectively (P = 0.00). The mean values of best-corrected visual acuity were 0.11 ± 0.13 in Group A and 0.22 ± 0.15 in Group B postoperatively (P < 0.05).
OCCIs on the steep axis were more effective than single CCI in the correction of mild to moderate pre-existing corneal astigmatism.
Keywords: Astigmatism, corneal incisions, phacoemulsification
|How to cite this article:|
Nassar MK, Said-Ahmed KE, Al-Morsy OA, Gawish DS. Management of pre-existing regular astigmatism in phacoemulsification. Menoufia Med J 2015;28:197-202
|How to cite this URL:|
Nassar MK, Said-Ahmed KE, Al-Morsy OA, Gawish DS. Management of pre-existing regular astigmatism in phacoemulsification. Menoufia Med J [serial online] 2015 [cited 2019 Sep 21];28:197-202. Available from: http://www.mmj.eg.net/text.asp?2015/28/1/197/155994
| Introduction|| |
Astigmatism may cause blurred vision, glare sensation, monocular diplopia, and visual aberrations .
Patients expect their vision to improve after cataract surgery and, increasingly, they expect to be free of the encumbrance of glasses and contact lenses .
These expectations are driven by technological advancements throughout the ophthalmic industry and the experiences of family and friends .
Pre-existing corneal astigmatism is a significant component of preoperative ametropia. To achieve satisfactory postoperative refractive results, it is important to correct pre-existing spherical errors by accurate biometry and intraocular lens (IOL) power calculation and to manage preoperative corneal astigmatism using measurements obtained by corneal topography .
The surgeon has a number of options for the intraoperative management of corneal astigmatism, which include the following:
- Placement of surgical wound along the steep axis of astigmatism.
- Relaxing incisions.
- Toric IOL.
- Tow-stage procedure with excimer laser ablation .
Incisions produce tissue gape, which causes corneal flattening in the meridian of the incision and steeping in the perpendicular meridian .
The astigmatic effect of clear corneal incisions (CCIs) has been put to effective use in modern cataract surgery for controlling pre-existing astigmatism. Performing an additional incision is called paired opposite clear corneal incisions (OCCIs) .
In the current study, we prospectively compared the effect of OCCIs and single CCIs in correction of pre-existing regular corneal astigmatism.
| Patients and methods|| |
This randomized prospective clinical study included 30 eyes of 30 cataract patients: 14 male and 16 female patients with topographic regular corneal astigmatism greater than 1 D.
Patients were selected from the outpatient clinics of the department of ophthalmology, Menoufia University Hospital from March 2012 to September 2013. Inclusion criteria were age greater than 30 years and topographic astigmatism more than 1 D. Patients with a history of pervious anterior segment procedures, corneal trauma or irregular astigmatism as in corneal opacities, corneal dystrophies, and corneal lesions were excluded.
The following preoperative examinations were performed on each patient:
- Full history taking.
- Uncorrected visual acuity testing (UCVA).
- Refraction and best-corrected visual acuity (BCVA).
- Anterior segment examination using slit lamp: cornea, anterior chamber, lens, and iris.
- Intraocular pressure measurement by Goldman's applanation tonometer.
- Fundus examination by both indirect ophthalmoscopy using +20 D lens and fundus biomicroscopy using +90 contact lens.
- Ophthalmic ultrasonography if the fundus was not seen by indirect ophalmoscopy.
- Corneal topography using pentcam.
The patients were randomly divided into two groups according to the technique of surgery, each group involved 15 eyes.
Group A: patients underwent corneal astigmatism correction with OCCIs along the steep axis of astigmatism.
Group (B): patients underwent corneal astigmatism correction with single CCIs along the steep axis of astigmatism.
The vertical axis (90°) was marked on the limbus before surgery with the patients in an upright position. All surgeries were performed by the same surgeon on an inpatient basis using peirbulber anesthesia and strict aseptic precautions. The most steep axis was marked using the degree marker. A self-sealing 3-mm CCI was made on the steep axis and routine phacoemulsification was performed, after a foldable IOL was inserted and irrigation/aspiration was performed. Wound closure was performed by stromal hydration. In Group A, a second CCI was made 180 degrees from the first incision, and subconjunctival injection of antibiotics and corticosteroids was given immediately after the surgery. All patients received routine postoperative topical steroid (every 6 h for 2 weeks, which was tapered and discontinued over 2 weeks later) and antibiotic eye drops for 4 weeks.
Follow-up visits were scheduled in the second, fourth, and eighth weeks, postoperatively, which included UCVA, BCVA, refraction, keratometry, and slit-lamp biomicroscopy. Corneal topography was obtained at the final follow-up for all patients.
The astigmatic change was calculated as the difference between the mean preoperative and the postoperative topographic readings. The change in surgically induced astigmatism (SIA) was calculated using the Jaffe vector analysis.
Results were collected, tabulated, and statistically analyzed using an IBM compatible personal computer with SPSS statistical package version 20.
Two types of statistically analyses were performed:
(1) Descriptive statistics were expressed as n (%), mean (X-0 ), and SD.
(2) Analytic statics
- Qualitative data were analyzed using the c2 -test.
- Normally distributed quantitative data were analyzed by the t-test (between two groups) and the analysis of variance test (for >2 groups), and the LSD test was used as a post-hoc test.
- Quantitative data that were not normally distributed were analyzed by the Mann-Whitney U-test (between two groups) and the Kruskal-Wallis test (for >2 groups), and the Tamhane test was used as a post-Hoc test.
- To compare between different measures in the same group at different time intervals, the Friedman test was used.
- A P-values of less than 0.05 was considered statistically significant.
| Results|| |
The study included 30 eyes of 30 patients with regular corneal astigmatism more than 1 D; they were divided randomly into two groups, each group containing 15 eyes. Each group included seven male (46.7%) and eight female (53.3%) patients. The mean age was 53.66 years ±11.29 (SD) and 59.33 years ± 4.45(SD) in Groups A and B, respectively. The mean intraocular pressure was 14.66 ± 2.02 and 15.80 ± 1.85 mmHg in Groups A and B, respectively. The mean axial length was 23.49 ± 0.98 mm in Group A and 24.59 ± 1.79 mm in Group B. There were no statistically significant differences in the preoperative parameters between the two groups [Table 1].
The mean values of preoperative topographic corneal astigmatism were 1.95 ± 0.83 D and 1.93 ± 0.51 D in Groups A and B, respectively. There was no statistically significant difference between both groups (P > 0.05) [Table 2].
On comparison between both groups regarding the BCVA, cylinder and spherical equivalents at the second, the fourth and the eighth weeks, we found that there was a highly significant difference between the postoperative mean values of these parameters, especially in the eighth week [Table 3].
The change in the mean values of astigmatism throughout the follow-up period were 0.85 ± 0.64, 0.67 ± 0.50, and 0.59 ± 0.47 D in Group A and 1.91 ± 0.57, 1.80 ± 0.50, and 1.53 ± 0.62 D in Group B in the second, fourth, and eighth weeks, respectively [Figure 1] and [Table 4].
The mean reduction in SIA in the eighth week postoperatively was 1.28 ± 0.11 D in Group A and 1.09 ± 0.13 D in Group B. There was a statistically significant reduction in SIA in both groups (P = 0.00) [Figure 2] and [Table 5].
|Figure 1: The change in the mean values of astigmatism preoperatively and throughout the foll ow-up period in the two groups.|
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|Figure 2: Comparison between the mean values of surgically induced astigmatism (SIA) reduction in both groups over the postoperative period.|
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|Table 4: Comparison between both groups regarding the keratometric readings throughout the postoperative period|
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|Table 5: Comparison between the mean values of surgically induced astigmatism reduction in both groups throughout|
the preoperative and the postoperative periods
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The coupling ratios (the amount of flattening or steeping along the incisional meridian divided by the amount of flattening or steepening 90° from the first meridian) were −0.91 ± 0.18 and −0.89 ± 0.21 in Groups A and B, respectively (P < 0.05).
The mean values of BCVA preoperatively and throughout the postoperative period in Group A were 0.67 ± 0.34, 0.24 ± 0.14, 0.16 ± 0.12, and 0.11 ± 0.13 and in Group B were 0.87 ± 0.29, 0.41 ± 0.17, 0.37 ± 0.20, and 0.22 ± 0.15 preoperatively, in the second, fourth, and eighth weeks and postoperatively, respectively. There was a statistically significant difference between the two groups (P = 0.00) [Table 6].
A comparison between the preoperative and the postoperative corneal topographic readings in one patient in each group shows the difference in the amount of astigmatism in the corneal map [Figure 3]a and b.
|Figure 3: Comparison between the preoperative and the postoperative corneal topographic reading s in one patient in each group.|
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|Table 6: Comparison between the mean values of best-corrected visual acuity and astigmatism preoperatively and over the|
postoperative period in each group
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| Discussion|| |
Modern cataract surgery using small incisions and foldable IOLs has led to achieving emmetropia in a significant number of patients. Modifications in the surgical technique and incisions may further improve refractive outcomes by reduction of astigmatism [6,7].
In our study, two groups of patients were operated upon by two different techniques: Group A involved OCCIs; Group B involved CCI; the incisions were made on the steepest meridian and the second incision on the meridian opposite to the first incision (180°).
The most steep axis was determined by preoperative keratometric readings and corneal topography by pentacam to all patients preoperatively.
Making the incision on the steep corneal axis is the simplest method, but it may be difficult or impossible with certain axes. Matsumoto, et al.  found that the amount of correction using this method varies but is usually reported to be less than 1 D. Their results are in agreement with the present study, as in Group B, the mean value of the amount of correction of astigmatism was 0.40 ± 0.62 D.
Akura et al. , Lindstrom et al. , and Hayashi et al.  found that astigmatism higher than 1.2 D cannot be corrected by a single clear corneal 3.2-mm incision at the limbus; therefore, a wider incision  or a second additional incision has been advocated in these cases . Our study concurs with these observations, as the mean value of the correction of astigmatism was 1.36 ± 0.36 D in patients in Group A with OCCI.
Lever and Dahan  found that an identical OCCI the first incision on the steep axis enhances the flattening on the cornea. They observed that OCCI are self-sealing, pose no added risk, require no extra surgical equipment, and are effective in treating pre-existing astigmatism .
In this study, the mean values of BCVA at the final follow-up visit were 0.11 ± 0.13 and 0.22 ± 0.15 in Groups A and B, respectively. These results are in agreement with the results reported by Sudarshan et al.  on visual improvement in the eighth week postoperatively.
In our study, we found no significant difference between the mean values of the mean K in the two groups throughout the postoperative period. These results agree with the results reported by Sudarshan et al. . They found that the mean values of the mean K in the OCCI group and the CCI group in the first, fourth, and 12th weeks, respectively, also showed no statistically significant difference between the two groups, reflecting the postoperative refractive stability .
BenSimon and Desatnik  compared OCCIs with a single CCI for the correction of astigmatism, and they found an enhanced effect of astigmatic correction of OCCIs on keratometric data analysis. The corneal topographic change analysis in our study concurs with their findings.
In our study, we found that the mean values of cylinder were 0.92 ± 0.59, 0.67 ± 0.50, and 0.58 ± 0.47 D in Group A and 1.95 ± 0.53, 1.81 ± 0.50, and 1.60 ± 0.65 D in Group B in the second, fourth, and eighth weeks, respectively, with a highly statistically significant difference between the data of both groups in the second, fourth, and eighth weeks postoperatively. The presence of this statistically significant difference in the cylinder was also reported by Sudarshan et al. , who found that the mean postoperative cylinder was 0.91 ± 0.54 D in Group A (OCCIs) and 1.57 ± 0.70 in Group B (CCI) at the final follow-up (P = 0.00).
In earlier studies of OCCI [13,14], the mean reduction in corneal astigmatism ranged from 0.50 to 2.06 D. Lever and Dahan  reported that 3.5-mm opposite clear cornea incisions straddling the steep axis decreased pre-existing astigmatism by a mean value of 2 D. Corresponding figures using this method have been reported to be 1.75 D by Tadros et al. , 1.66 D by BenSimon and Desatink , and 2.10 D by Qammar and Mullaney . In our study, the mean value of reduction of astigmatism was 1.72 D in Group A at the final follow-up.
In our study, there was a highly statistically significant difference between the mean values of the reduction of SIA in the two groups in the second, fourth, and eighth weeks, respectively.
In a previous study , the mean value of reduction of SIA was 1.66 ± 0.50 D in the OCCI group and 0.58 ± 0.57 D in the CCI group. Noushin et al.  observed that the mean values of reduction of SIA were statistically significant in OCCI (P = 0.009).
Sudarshan et al.  observed that the coupling ratio was −0.96 in the OCCI group and −0.87 in the CCI group. These values concur with our findings; the coupling ratio was −0.91 ± 0.18 in Group A and 0.89 ± 0.12 in Group B.
BenSimon and Desatnik  found that the change in the spherical equivalent between the two groups was nonsignificant, but in our study, we found that there was a statistically significant difference between the two groups. The values of the mean of the spherical equivalent were 0.99 ± 0.65, 0.77 ± 0.63, and 0.71 ± 0.60 in Group A, and 1.74 ± 0.47, 1.45 ± 0.5, and 1.61 ± 1.25 in Group B in the second, fourth, and eighth weeks, respectively (P < 0.05).
In this study, we compared the mean values of the BCVA preoperatively and throughout the postoperative follow-up period in the same group; this comparison showed that there is a highly statistically significant difference between the values at different times in the same group; this indicated that there is visual improvement in both groups, but more in Group A than in Group B.
The same 3-mm knife used by most surgeons for routine phacoemulsification cataract surgery was used for making both incisions, and therefore, no additional cost was entailed. This method is effective for the correction of mild to moderate corneal astigmatism, but in eyes with higher degrees of astigmatism, it is recommended to use an alternative method or a combination of two or more methods .
Some studies have reported that young patients heal differently from older patients; we found the effect of OCCIs to be uniform in all age groups [13, 15, 16].
| Conclusion|| |
Paired opposite CCIs on the steep axis are more effective than a single CCI on the steep axis in the correction of mild to moderate pre-existing regular astigmatism during phacoemulsification. The use of this technique during routine phacoemulsification using a 3-mm incision does not require additional instruments, and therefore can be performed without altering the surgical setting.
| Acknowledgements|| |
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]