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Batch-by-batch analysis of topographic changes induced by sutured and sutureless clear corneal incisions
Batch-by-batch analysis of topographic changes induced by sutured and sutureless clear corneal incisions Clemens Vass, MD, Rupert Menapace, MD, Michael Amon, MD, Ursula Hirsch, MD, Assad Yousef, MD
ABSTRACT Purpose: To evaluate the effect of a suture on surgically induced corneal topographic changes in 5.0 mm clear corneal incisions. Setting: University Eye Hospital, Vienna, Austria. Methods: Thirty-seven eyes that had cataract surgery were included in the prospective study. A 5.0 mm long and 0.3 mm deep precut was followed by preparation of a corneal tunnel. After phacoemulsification and intraocular lens implantation, the self-sealing wound was left unsutured in 19 eyes; one radial 11-0 nylon suture was applied in 18 eyes. Using a TMS-1 videokeratoscope, corneal topography was measured preoperatively and at 1 week and 1 and 3 months postoperatively. The topographic data were evaluated by statistical batch-by-batch analysis. Each topographic image was cut into 178 fields in eight concentric rings. The refractive values of these fields were stored in a database. Differences between the four readings of each patient were calculated and the mean differences of the 178 fields in each group were transformed into color-coded maps. The significance of topographical changes and group comparisons of induced changes were computed by Wilcoxon tests. Results: Both groups exhibited significant temporal flattening and vertical steepening. The unsutured eyes also displayed significant nasal flattening. Sutureless 5.0 mm clear corneal incisions induced significantly more vertical steepening and nasal flattening than sutured incisions. Conclusion: Application of one radial 11-0 nylon suture in 5.0 mm temporal clear corneal incisions significantly reduced shape changes in the nasal corneal region. J Cataract Refract Surg 1996; 22:324-330
A
lthough numerous presentations on clear corneal incisions have been made in the past few years, little has been published. 1,2 Corneal shape
From the Universitdts Augenklinik, Vienna, Austria. Presented in part at the 12th Congress ofthe European Society o/Cataract and Refractive Surgeons, Lisbon, September 1994. Authors have no commercial or proprietary interest in any a/the companies or products mentioned. Reprint requests to Clemens Vass, MD, Universitiits Augenklinik, Wiihringer GiirteI18-20, A-1090 Vienna, Austria.
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changes after cataract extraction are usually wound related and asymmetric. 3 Asymmetric flattening, which is restricted to the area adjacent to the incision, is missed by the keratometer but not by the video keratoscope. We have described a method of statistical batch-by-batch analysis of corneal topographic changes. 4 We used this method to evaluate the influence of a single 11-0 nylon sutute on surgically induced corneal shape changes after 5.0 mm temporal clear corneal incision cataract surgery.
J CATARACT REFRACT SURG-VOL 22, APRIL 1996
BATCH-BY-BATCH ANALYSIS OF CCI TOPOGRAPHY
Subjects and Methods Surgically induced corneal topographic changes after 5.0 mm temporal clear corneal incision were studied in 37 eyes 004 patients. All surgery was done by one of two surgeons (R.M., M.A.) between March and June 1993. Mter a 5.0 mm long and 0.3 mm deep limbal precut was made, a linear corneal tunnel of 2.0 mm length was constructed with a diamond lance. Capsulorhexis and phacoemulsification were performed and a poly(methyl methacrylate) intraocular lens (IOL) with a 5.0 mm optic diameter or a flexible silicone 10L (Pharmacia 809C, loptex UPB350S, ORC C41 OF, or STAAR) was implanted. In 18 eyes, Group 1, a radial 11-0 nylon suture was applied. Mean patient age of this group was 80.4 years 2: 6.3 (SD). In 19 eyes, Group 2, no suture was used. Mean patient age was 75.4 2: 12.5 years. Indomethacin and cortisone eyedrops were administered to both groups for 1 month postoperatively. No sutures were removed during the follow-up. Corneal topography was measured using the TMS-l videokeratoscope (Computed Anatomy, Inc.). Topographic readings were taken preoperatively and 1 week and 1 and 3 months postoperatively. The preoperative reading was compared with each postoperative reading. Data were analyzed by our computerized method. 4 For statistical analysis, corneal topography was divided into 178 fields in eight concentric rings. The refractive values of 178 defined points of corneal topography were allocated to the respective fields and stored in a computer database. In this process, the left eyes were reproduced as mirror images by a program. The differences between every two of the four readings of all patients were calculated. These differences in each of the 178 corneal fields of all patients of both groups were stored in separate files by group. A color-coded diagram with 178 fields was constructed to represent corneal topography. One color was allocated to each field to represent the mean difference between two examinations. In this way, we obtained color-coded maps showing the distribution of the mean differences throughout the cornea in each group. Standard deviations of the differences in each of the 178
fields were calculated for both groups and transformed into color-coded maps. For statistical evaluation of surgically induced corneal shape changes, nonparametric paired t-tests (Wilcoxon signed rank test) were performed for both groups between every two examinations. The significance levels of the paired t-tests were calculated and automatically superimposed on the color-coded difference maps. The statistical difference between the induced corneal shape changes of the two groups was evaluated by means of non parametric Wilcoxon tests that compared the corresponding difference files of both groups. The results were automatically transformed into color-coded maps with 178 fields.
Results Mean surgically induced topographic changes in both groups at 1 week postoperatively are shown in Figure 1. Group 1 showed a mean temporal flattening of 0.5 to 2.0 diopters (D), a vertical steepening between 0 and 1.0 D, and nasal flattening between 0 and 0.5 D. Group 2 showed a mean temporal flattening of 0.5 to 2.5 D, a vertical steepening between 0 and 1.0 D, and nasal flattening between 0 and 1.0 D. The steepening and flattening axes were not orthogonal. The semimeridians of maximal steepening were not vertical but adjacent to the flattening area, forming angles of 158 degrees in Group 1 and 135 degrees in Group 2. For simplicity, we will call these slightly oblique semimeridians "vertical." One month postoperatively (Figure 2), mean surgically induced corneal shape changes in Group 1 were very similar with a temporal flattening of 0.50 to 1.75 D, a vertical steepening of 0.25 to 0.75 D, and nasal changes between +0.25 and -0.50 D. Group 2 showed a mean temporal flattening of 0.25 to 2.00 D, a vertical steepening of 0.50 to 1.00 D, and nasal flattening between 0.50 and 1.00 D. Three months postoperatively (Figure 3), Group 1 had a mean surgically induced temporal flattening of 0.25 to 1.25 D, a vertical steepening of 0.25 to 0.75 D, and nasal changes between +0.25 and -0.25 D. Group 2 had mean temporal flattening of 0.50 to 1.75 D, vertical steepening of 0.25 to 0.75 D, and nasal flattening between 0.25 and 0.75 D.
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-4 -3,51 -3,5 -3,01 -3 -2,51 -2,5 -2,01 -2 - -1,51 -1,5 -1,01 -1 -0,51 -0,5 -0,01 o - 0,49 0,5 - 0,99 1 1,49 1,5 - 1,99 2 2,49 2,5 - 2,99 3,49 3 3,5 3,99
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temporal
nasal
Figure 1. (Vass) Mean surgically induced topographic changes 1 week postoperatively. Each segment has a radial diameter of = 0.5 mm . Left: Group 1. Right: Group 2.
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o-
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0,25 0,5 0,75 1 1,25 1,5 1,75
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-1,78 -1,51 -1,28 -1,01 ·0,76 -0,51 -0,26 -0,01 0,24 0,49 0,74 0,99 1,24 1,49 1,74 1,99
Figure 2. (Vass) Mean surgically induced topographic changes 1 month postoperatively. Each segment has a radial diameter of = 0.5 mm. Left: Group 1. Right: Group 2.
-1,78 -1,51 -1,26 -1,01 -0,76 -0,51 - -0,26 25 - -0,01 o 0,24 0,25 0,49 0,5 0,74 0,75 - 0,99
1 -
'--_ _ _ _;;;;;;.;.,.....--0-.:;;;....._ _ _......"
temporal
nasal
1,25 1,5 1,75
1,24
1,49 1,74 1,99
Figure 3. (Vass) Mean surgically induced topographic changes 3 months postoperatively. Each segment has a radial diameter of = 0.5 mm. Left: Group 1. Right: Group 2.
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-2 '1.75 -1.5 -1.25 -I '0.75 -0.5 ·0.25 0 0.25 0.5 0.75 1 1.25 1.5 1.75
. .
-1.76 ·1.51 -1.26 -1.01 -0.76 -0.51 -0.26 -0.01 0.24 0.49 0.74 0.99 1.24 1.49 1.74 1.99
Figure 4. (Vass) Mean difference maps between the 3 month and 1 week postoperative topographic records. Each segment has a radial diameter of =0.5 mm. Left: Group 1. Right: Group 2.
o -
0.12 0.24 0.37 0.49 0.62 0.74 0.87 0.99 I . 1.12 1.13 . 1.24 1.25 - 1.37 1.38 . 1.49 US . 1.62 1.63 - 1.74 1.87 - - - - - -... 1.75 1.88 . 1.99 nasal 0.13 0.25 0.38 0.5 0.63 0.75 0.88
temporal
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Figure 5. (Vass) Standard deviations of surgically induced topographic changes 1 week postoperatively. Each segment has a radial diameter of = 0.5 mm. Left: Group 1. Right: Group 2.
Between 1 week and 3 months postoperatively, there was some regression of the induced topographical changes in both groups (Figure 4). Group 1 showed a regression of the mean horizontal flattening between 0 and 0.75 0; the vertical axis was stable with changes between +0.25 and -0.25 O. In the same period, Group 2 showed a regression of the mean temporal flattening and the mean vertical steepening between 0 and 0.75 O. There were no mean nasal changes (-0.25 to +0.25 D). Standard deviations of differences between 1 week postoperative and preoperative topographic records in both groups were comparable, although Group 1 showed slightly higher values, especially temporally near the incision site (Figure 5). Three months postoperatively, the standard deviations of changes in both groups were similar (Figure 6).
Standard deviations of most corneal fields ranged between 0.38 and 0.87 D. The results of the paired Wilcoxon tests, comparing the 1 week postoperative with the preoperative corneal topography, are shown in Figure 7. Corneal changes in the unhatched areas were significant (P:::; .01), while those in the hatched areas were not. In Group 1, induced temporal flattening and, at some points, vertical steepening were statistically significant. There were no significant nasal topographic changes postoperatively. In Group 2, temporal flattening was statistically significant and there were larger areas of vertical steepening 1 week postoperatively; nasal flattening was significant. Figure 8 represents the results of paired Wilcoxon tests (P :::; .01), comparing 3 month postoperative and preoperative corneal topography. In Group I, in-
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o
temporal
0,13 0,25 0,38 0,5 0,63 0,75 0,88 1 1,13 1,25 1,38 1,5 1,63 - - - - -..... 1.75 nasal 1,88
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0,12 0,24 0,37 0,49 0,62 0,74 0,87 0,99 1.12 1,24 1,37 1,49 1,62 1,74 1,87 1,99
Figure 6. (Vass) Standard deviations of surgically induced topographic changes 3 months postoperatively. Each segment has a radial diameter of ""0.5 mm. Left: Group 1. Right: Group 2.
temporal
nasal
-4 -3.51 -3,5 -3.01 -3 -2.51 -2,5 - -2.01 -2 -1.51 -1,5 -1.01 -I - -0.51 -0,5 -0,01 o 0.49 0,5 0.99 1 1.49 1,99 1,5 2 - 2.49 2,5 2.99 3 - 3.49 3,5 3,99
significant not significant Figure 7. (Vass) Results of paired Wilcoxon tests for the surgically induced topographic changes 1 week postoperatively (P :0; .01). Unhatched areas are significant. while hatched areas are not. Each segment has a radial diameter of =0.5 mm. Left: Group 1. Right: Group 2.
temporal
nasal
-1,76 -1.51 -1.26 -1.01 -0.76 -0.51 - -0.26 - -0.01 o - 0.24 0.25 - 0.49 0.5 0.74 0.75 - 0.99 1 1.24 1.25 - 1.49 1.5 - 1.74 1.75 - 1.99
significant not significant Figure 8. (Vass) Results of paired Wilcoxon tests for the surgically induced topographic changes 3 months postoperatively (P :0; .01). Unhatched areas are significant, while hatched areas are not. Each segment has a radial diameter of =0.5 mm. Left: Group 1. Right: Group 2.
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duced temporal flattening and vertical steepening were statistically significant. There were no significant postoperative nasal topographic changes. In Group 2, there was statistically significant temporal flattening and a smaller area of vertical steepening 3 months postoperatively. There was also significant nasal flattening. Figure 9 compares the 3 month and 1 week postoperative corneal topographic records. Group 1 showed significant regression of horizontal flattening (P-S; .01). Group 2 showed significant regression of vertical steepening and temporal flattening in the 8.0 mm zone.
temporal
nasal
Mean spherical change of the 6.0 mm area was +0.16:::!: 0.370 in Group 1 and -0.09 :::!: 0.350 in Group 2. The difference between groups was not statistically significant. Figure 10 shows induced topographic changes in the groups 1 month postoperatively. Blue colors represent the deeper flattening and red colors the increased steepening in Group 2 compared with Group 1. Sutureless 5.0 mm clear corneal incisions induced significantly more vertical steepening and nasal flattening than sutured incisions. At 3 months postoperatively, the group
-2 -1.76 1,75 - -1.51 -1.5 -1.26 1.25 -1.01 -1 -0.76 0.75 -0.51 -0.5 -0.26 0.25 -0.01 o 0.24 0.25 0.49 0.74 0.5 0.75 0.99 1 1.24 1.25 1.49 1.5 1.74 1.75 1.99
significant not significant Figure 9. (Vass) Results of paired Wilcoxon tests for the differences between the 3 month and 1 week postoperative topographic records (P :5 .01). Unhatched areas are significant, while hatched areas are not. Each segment has a radial diameter of =0.5 mm. Left: Group 1. Right: Group 2.
Figure 10. (Vass) Results of comparison of induced topographic changes between Groups 1 and 2. Blue colors represents deeper flattening and red colors increased steepening of Group 2 compared with Group 1 (P :5 .05). Unhatched areas are significant, while hatched areas are not. Each segment has a radial diameter of = 0.5 mm. Left: Group 1. Right: Group 2.
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comparison showed no significant differences in vertical steepening; however, there was a significant difference between groups in the nasal corneal region, where Group 2 showed significantly more flattening than Group 1.
Discussion fu shown by the mean topographic difference maps, induced corneal shape changes are not orthogonal. The vertical semimeridians are actually adjacent to the region of temporal flattening and form an angle between 135 and 158 degrees that is larger near the center and decreases toward the periphery. Detection of such nonorthogonal changes would have been impossible with vector analysis of keratometric readings. Both patient groups developed very similar surgically induced topographic changes consisting mainly of significant temporal flattening and vertical steepening. The major difference between the groups was the significant nasal flattening in Group 2 in Wilcoxon tests 3 months postoperatively. Between the first week and the third month postoperatively, areas of significant regression of surgically induced shape changes were recorded in both groups. Group 1 had more significant horizontal flattening, while Group 2 had more significant regression of vertical steepening. These different regression patterns might be partly due to a slightly positive spherical shift in Group 1 compared with a slightly negative spherical change in Group 2. The spherical changes of
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+0.16 ± 0.37 D in Group 1 and -0.09 ± 0.35 Din Group 2 are within the expected range of focusing artifacts 5 of the video keratoscope and do not differ significantly. Results of induced corneal shape changes were very similar in both groups, with Group 1 performing a little better than Group 2. One radial 11-0 nylon suture significantly reduced surgically induced nasal flattening. We found no argument for leaving a 5.0 mm clear corneal incision unsutured because one suture increased security and limited surgically induced corneal shape changes.
References 1. Langerman DW. Architectural design of a self-sealing corneal tunnel, single-hinge incision. J Cataract Refract Surg 1994; 20:84-88 2. Davis PL. PMMA implants via temporal clear corneal incisions: concern replaces confidence. Eur J Implant Refract Surg 1994; 6:205-210 3. Martin RG, Sanders DR, Miller JD, et al. Effect of cataract wound incision size on acute changes in corneal topography. J Cataract Refract Surg 1993; 19: 170 -177 4. Vass C, Menapace R. Computerized statistical analysis of corneal topography for the evaluation of changes in corneal shape after surgery. Am J Ophthalmol 1994; 118: 177-184 5. Legeais J-M, Ren Q, Simon G, Parel J-M. Computerassisted corneal topography: accuracy and reproducibility of the Topographic Modeling System. Refract Corneal Surg 1993; 9:347-357
J CATARACT REFRACT SURG-VOL 22, APRIL 1996
ABSTRACT Purpose: To evaluate the effect of a suture on surgically induced corneal topographic changes in 5.0 mm clear corneal incisions. Setting: University Eye Hospital, Vienna, Austria. Methods: Thirty-seven eyes that had cataract surgery were included in the prospective study. A 5.0 mm long and 0.3 mm deep precut was followed by preparation of a corneal tunnel. After phacoemulsification and intraocular lens implantation, the self-sealing wound was left unsutured in 19 eyes; one radial 11-0 nylon suture was applied in 18 eyes. Using a TMS-1 videokeratoscope, corneal topography was measured preoperatively and at 1 week and 1 and 3 months postoperatively. The topographic data were evaluated by statistical batch-by-batch analysis. Each topographic image was cut into 178 fields in eight concentric rings. The refractive values of these fields were stored in a database. Differences between the four readings of each patient were calculated and the mean differences of the 178 fields in each group were transformed into color-coded maps. The significance of topographical changes and group comparisons of induced changes were computed by Wilcoxon tests. Results: Both groups exhibited significant temporal flattening and vertical steepening. The unsutured eyes also displayed significant nasal flattening. Sutureless 5.0 mm clear corneal incisions induced significantly more vertical steepening and nasal flattening than sutured incisions. Conclusion: Application of one radial 11-0 nylon suture in 5.0 mm temporal clear corneal incisions significantly reduced shape changes in the nasal corneal region. J Cataract Refract Surg 1996; 22:324-330
A
lthough numerous presentations on clear corneal incisions have been made in the past few years, little has been published. 1,2 Corneal shape
From the Universitdts Augenklinik, Vienna, Austria. Presented in part at the 12th Congress ofthe European Society o/Cataract and Refractive Surgeons, Lisbon, September 1994. Authors have no commercial or proprietary interest in any a/the companies or products mentioned. Reprint requests to Clemens Vass, MD, Universitiits Augenklinik, Wiihringer GiirteI18-20, A-1090 Vienna, Austria.
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changes after cataract extraction are usually wound related and asymmetric. 3 Asymmetric flattening, which is restricted to the area adjacent to the incision, is missed by the keratometer but not by the video keratoscope. We have described a method of statistical batch-by-batch analysis of corneal topographic changes. 4 We used this method to evaluate the influence of a single 11-0 nylon sutute on surgically induced corneal shape changes after 5.0 mm temporal clear corneal incision cataract surgery.
J CATARACT REFRACT SURG-VOL 22, APRIL 1996
BATCH-BY-BATCH ANALYSIS OF CCI TOPOGRAPHY
Subjects and Methods Surgically induced corneal topographic changes after 5.0 mm temporal clear corneal incision were studied in 37 eyes 004 patients. All surgery was done by one of two surgeons (R.M., M.A.) between March and June 1993. Mter a 5.0 mm long and 0.3 mm deep limbal precut was made, a linear corneal tunnel of 2.0 mm length was constructed with a diamond lance. Capsulorhexis and phacoemulsification were performed and a poly(methyl methacrylate) intraocular lens (IOL) with a 5.0 mm optic diameter or a flexible silicone 10L (Pharmacia 809C, loptex UPB350S, ORC C41 OF, or STAAR) was implanted. In 18 eyes, Group 1, a radial 11-0 nylon suture was applied. Mean patient age of this group was 80.4 years 2: 6.3 (SD). In 19 eyes, Group 2, no suture was used. Mean patient age was 75.4 2: 12.5 years. Indomethacin and cortisone eyedrops were administered to both groups for 1 month postoperatively. No sutures were removed during the follow-up. Corneal topography was measured using the TMS-l videokeratoscope (Computed Anatomy, Inc.). Topographic readings were taken preoperatively and 1 week and 1 and 3 months postoperatively. The preoperative reading was compared with each postoperative reading. Data were analyzed by our computerized method. 4 For statistical analysis, corneal topography was divided into 178 fields in eight concentric rings. The refractive values of 178 defined points of corneal topography were allocated to the respective fields and stored in a computer database. In this process, the left eyes were reproduced as mirror images by a program. The differences between every two of the four readings of all patients were calculated. These differences in each of the 178 corneal fields of all patients of both groups were stored in separate files by group. A color-coded diagram with 178 fields was constructed to represent corneal topography. One color was allocated to each field to represent the mean difference between two examinations. In this way, we obtained color-coded maps showing the distribution of the mean differences throughout the cornea in each group. Standard deviations of the differences in each of the 178
fields were calculated for both groups and transformed into color-coded maps. For statistical evaluation of surgically induced corneal shape changes, nonparametric paired t-tests (Wilcoxon signed rank test) were performed for both groups between every two examinations. The significance levels of the paired t-tests were calculated and automatically superimposed on the color-coded difference maps. The statistical difference between the induced corneal shape changes of the two groups was evaluated by means of non parametric Wilcoxon tests that compared the corresponding difference files of both groups. The results were automatically transformed into color-coded maps with 178 fields.
Results Mean surgically induced topographic changes in both groups at 1 week postoperatively are shown in Figure 1. Group 1 showed a mean temporal flattening of 0.5 to 2.0 diopters (D), a vertical steepening between 0 and 1.0 D, and nasal flattening between 0 and 0.5 D. Group 2 showed a mean temporal flattening of 0.5 to 2.5 D, a vertical steepening between 0 and 1.0 D, and nasal flattening between 0 and 1.0 D. The steepening and flattening axes were not orthogonal. The semimeridians of maximal steepening were not vertical but adjacent to the flattening area, forming angles of 158 degrees in Group 1 and 135 degrees in Group 2. For simplicity, we will call these slightly oblique semimeridians "vertical." One month postoperatively (Figure 2), mean surgically induced corneal shape changes in Group 1 were very similar with a temporal flattening of 0.50 to 1.75 D, a vertical steepening of 0.25 to 0.75 D, and nasal changes between +0.25 and -0.50 D. Group 2 showed a mean temporal flattening of 0.25 to 2.00 D, a vertical steepening of 0.50 to 1.00 D, and nasal flattening between 0.50 and 1.00 D. Three months postoperatively (Figure 3), Group 1 had a mean surgically induced temporal flattening of 0.25 to 1.25 D, a vertical steepening of 0.25 to 0.75 D, and nasal changes between +0.25 and -0.25 D. Group 2 had mean temporal flattening of 0.50 to 1.75 D, vertical steepening of 0.25 to 0.75 D, and nasal flattening between 0.25 and 0.75 D.
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-4 -3,51 -3,5 -3,01 -3 -2,51 -2,5 -2,01 -2 - -1,51 -1,5 -1,01 -1 -0,51 -0,5 -0,01 o - 0,49 0,5 - 0,99 1 1,49 1,5 - 1,99 2 2,49 2,5 - 2,99 3,49 3 3,5 3,99
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temporal
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Figure 1. (Vass) Mean surgically induced topographic changes 1 week postoperatively. Each segment has a radial diameter of = 0.5 mm . Left: Group 1. Right: Group 2.
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o-
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nasal
0,25 0,5 0,75 1 1,25 1,5 1,75
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-1,78 -1,51 -1,28 -1,01 ·0,76 -0,51 -0,26 -0,01 0,24 0,49 0,74 0,99 1,24 1,49 1,74 1,99
Figure 2. (Vass) Mean surgically induced topographic changes 1 month postoperatively. Each segment has a radial diameter of = 0.5 mm. Left: Group 1. Right: Group 2.
-1,78 -1,51 -1,26 -1,01 -0,76 -0,51 - -0,26 25 - -0,01 o 0,24 0,25 0,49 0,5 0,74 0,75 - 0,99
1 -
'--_ _ _ _;;;;;;.;.,.....--0-.:;;;....._ _ _......"
temporal
nasal
1,25 1,5 1,75
1,24
1,49 1,74 1,99
Figure 3. (Vass) Mean surgically induced topographic changes 3 months postoperatively. Each segment has a radial diameter of = 0.5 mm. Left: Group 1. Right: Group 2.
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-2 '1.75 -1.5 -1.25 -I '0.75 -0.5 ·0.25 0 0.25 0.5 0.75 1 1.25 1.5 1.75
. .
-1.76 ·1.51 -1.26 -1.01 -0.76 -0.51 -0.26 -0.01 0.24 0.49 0.74 0.99 1.24 1.49 1.74 1.99
Figure 4. (Vass) Mean difference maps between the 3 month and 1 week postoperative topographic records. Each segment has a radial diameter of =0.5 mm. Left: Group 1. Right: Group 2.
o -
0.12 0.24 0.37 0.49 0.62 0.74 0.87 0.99 I . 1.12 1.13 . 1.24 1.25 - 1.37 1.38 . 1.49 US . 1.62 1.63 - 1.74 1.87 - - - - - -... 1.75 1.88 . 1.99 nasal 0.13 0.25 0.38 0.5 0.63 0.75 0.88
temporal
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Figure 5. (Vass) Standard deviations of surgically induced topographic changes 1 week postoperatively. Each segment has a radial diameter of = 0.5 mm. Left: Group 1. Right: Group 2.
Between 1 week and 3 months postoperatively, there was some regression of the induced topographical changes in both groups (Figure 4). Group 1 showed a regression of the mean horizontal flattening between 0 and 0.75 0; the vertical axis was stable with changes between +0.25 and -0.25 O. In the same period, Group 2 showed a regression of the mean temporal flattening and the mean vertical steepening between 0 and 0.75 O. There were no mean nasal changes (-0.25 to +0.25 D). Standard deviations of differences between 1 week postoperative and preoperative topographic records in both groups were comparable, although Group 1 showed slightly higher values, especially temporally near the incision site (Figure 5). Three months postoperatively, the standard deviations of changes in both groups were similar (Figure 6).
Standard deviations of most corneal fields ranged between 0.38 and 0.87 D. The results of the paired Wilcoxon tests, comparing the 1 week postoperative with the preoperative corneal topography, are shown in Figure 7. Corneal changes in the unhatched areas were significant (P:::; .01), while those in the hatched areas were not. In Group 1, induced temporal flattening and, at some points, vertical steepening were statistically significant. There were no significant nasal topographic changes postoperatively. In Group 2, temporal flattening was statistically significant and there were larger areas of vertical steepening 1 week postoperatively; nasal flattening was significant. Figure 8 represents the results of paired Wilcoxon tests (P :::; .01), comparing 3 month postoperative and preoperative corneal topography. In Group I, in-
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o
temporal
0,13 0,25 0,38 0,5 0,63 0,75 0,88 1 1,13 1,25 1,38 1,5 1,63 - - - - -..... 1.75 nasal 1,88
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0,12 0,24 0,37 0,49 0,62 0,74 0,87 0,99 1.12 1,24 1,37 1,49 1,62 1,74 1,87 1,99
Figure 6. (Vass) Standard deviations of surgically induced topographic changes 3 months postoperatively. Each segment has a radial diameter of ""0.5 mm. Left: Group 1. Right: Group 2.
temporal
nasal
-4 -3.51 -3,5 -3.01 -3 -2.51 -2,5 - -2.01 -2 -1.51 -1,5 -1.01 -I - -0.51 -0,5 -0,01 o 0.49 0,5 0.99 1 1.49 1,99 1,5 2 - 2.49 2,5 2.99 3 - 3.49 3,5 3,99
significant not significant Figure 7. (Vass) Results of paired Wilcoxon tests for the surgically induced topographic changes 1 week postoperatively (P :0; .01). Unhatched areas are significant. while hatched areas are not. Each segment has a radial diameter of =0.5 mm. Left: Group 1. Right: Group 2.
temporal
nasal
-1,76 -1.51 -1.26 -1.01 -0.76 -0.51 - -0.26 - -0.01 o - 0.24 0.25 - 0.49 0.5 0.74 0.75 - 0.99 1 1.24 1.25 - 1.49 1.5 - 1.74 1.75 - 1.99
significant not significant Figure 8. (Vass) Results of paired Wilcoxon tests for the surgically induced topographic changes 3 months postoperatively (P :0; .01). Unhatched areas are significant, while hatched areas are not. Each segment has a radial diameter of =0.5 mm. Left: Group 1. Right: Group 2.
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duced temporal flattening and vertical steepening were statistically significant. There were no significant postoperative nasal topographic changes. In Group 2, there was statistically significant temporal flattening and a smaller area of vertical steepening 3 months postoperatively. There was also significant nasal flattening. Figure 9 compares the 3 month and 1 week postoperative corneal topographic records. Group 1 showed significant regression of horizontal flattening (P-S; .01). Group 2 showed significant regression of vertical steepening and temporal flattening in the 8.0 mm zone.
temporal
nasal
Mean spherical change of the 6.0 mm area was +0.16:::!: 0.370 in Group 1 and -0.09 :::!: 0.350 in Group 2. The difference between groups was not statistically significant. Figure 10 shows induced topographic changes in the groups 1 month postoperatively. Blue colors represent the deeper flattening and red colors the increased steepening in Group 2 compared with Group 1. Sutureless 5.0 mm clear corneal incisions induced significantly more vertical steepening and nasal flattening than sutured incisions. At 3 months postoperatively, the group
-2 -1.76 1,75 - -1.51 -1.5 -1.26 1.25 -1.01 -1 -0.76 0.75 -0.51 -0.5 -0.26 0.25 -0.01 o 0.24 0.25 0.49 0.74 0.5 0.75 0.99 1 1.24 1.25 1.49 1.5 1.74 1.75 1.99
significant not significant Figure 9. (Vass) Results of paired Wilcoxon tests for the differences between the 3 month and 1 week postoperative topographic records (P :5 .01). Unhatched areas are significant, while hatched areas are not. Each segment has a radial diameter of =0.5 mm. Left: Group 1. Right: Group 2.
Figure 10. (Vass) Results of comparison of induced topographic changes between Groups 1 and 2. Blue colors represents deeper flattening and red colors increased steepening of Group 2 compared with Group 1 (P :5 .05). Unhatched areas are significant, while hatched areas are not. Each segment has a radial diameter of = 0.5 mm. Left: Group 1. Right: Group 2.
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BATCH-BY-BATCH ANALYSIS OF CCI TOPOGRAPHY
comparison showed no significant differences in vertical steepening; however, there was a significant difference between groups in the nasal corneal region, where Group 2 showed significantly more flattening than Group 1.
Discussion fu shown by the mean topographic difference maps, induced corneal shape changes are not orthogonal. The vertical semimeridians are actually adjacent to the region of temporal flattening and form an angle between 135 and 158 degrees that is larger near the center and decreases toward the periphery. Detection of such nonorthogonal changes would have been impossible with vector analysis of keratometric readings. Both patient groups developed very similar surgically induced topographic changes consisting mainly of significant temporal flattening and vertical steepening. The major difference between the groups was the significant nasal flattening in Group 2 in Wilcoxon tests 3 months postoperatively. Between the first week and the third month postoperatively, areas of significant regression of surgically induced shape changes were recorded in both groups. Group 1 had more significant horizontal flattening, while Group 2 had more significant regression of vertical steepening. These different regression patterns might be partly due to a slightly positive spherical shift in Group 1 compared with a slightly negative spherical change in Group 2. The spherical changes of
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+0.16 ± 0.37 D in Group 1 and -0.09 ± 0.35 Din Group 2 are within the expected range of focusing artifacts 5 of the video keratoscope and do not differ significantly. Results of induced corneal shape changes were very similar in both groups, with Group 1 performing a little better than Group 2. One radial 11-0 nylon suture significantly reduced surgically induced nasal flattening. We found no argument for leaving a 5.0 mm clear corneal incision unsutured because one suture increased security and limited surgically induced corneal shape changes.
References 1. Langerman DW. Architectural design of a self-sealing corneal tunnel, single-hinge incision. J Cataract Refract Surg 1994; 20:84-88 2. Davis PL. PMMA implants via temporal clear corneal incisions: concern replaces confidence. Eur J Implant Refract Surg 1994; 6:205-210 3. Martin RG, Sanders DR, Miller JD, et al. Effect of cataract wound incision size on acute changes in corneal topography. J Cataract Refract Surg 1993; 19: 170 -177 4. Vass C, Menapace R. Computerized statistical analysis of corneal topography for the evaluation of changes in corneal shape after surgery. Am J Ophthalmol 1994; 118: 177-184 5. Legeais J-M, Ren Q, Simon G, Parel J-M. Computerassisted corneal topography: accuracy and reproducibility of the Topographic Modeling System. Refract Corneal Surg 1993; 9:347-357
J CATARACT REFRACT SURG-VOL 22, APRIL 1996