ARTICLE
Topographic Changes After Excision Surgery of Primary Pterygia and the Effect of Pterygium Size on Topograpic Restoration Ryohei Nejima,
M.D.,
Ayami Masuda,
M.D.,
Keiichiro Minami, Ph.D., Yosai Mori, and Kazunori Miyata, M.D. Ph.D.
Objective: To assess the effect of pterygium size on time-course change of corneal topography after excision surgery of primary pterygium. Methods: Retrospective case series included eyes that underwent excisions of primary pterygium. Pterygium size was graded according to the advancing edge position: less than one third of corneal diameter (grade 1), outside the pupil (grade 2), and within the pupillary area (grade 3). Time-course changes in corneal refractive power, astigmatism, and irregularity (surface regularity and asymmetry indices) in corneal topographies over 12 months postoperatively were compared between the pterygium size grades. Results: Pterygium excision was performed on 562 eyes, consisting of 119, 338, and 105 eyes with grades 1 to 3, respectively. Grade 1 did not change in corneal irregularity, and there was no difference between grades 1 and 2, except for corneal astigmatism at 6 months. Grade 3 showed significantly higher corneal refractive power and irregularity than grade 1 until 3 and 6 months, respectively, whereas corneal astigmatism was higher over 12 months. Conclusions: Topographic changes after primary pterygium excision were associated with pterygium size. Pterygium advancing over the pupillary area required 6 to 12 months for corneal topography restoration, resulting in slow recovery of visual acuity. Key Words: Pterygium—Topography—Irregular astigmatism. (Eye & Contact Lens 2015;41: 58–63)
P
terygium is a fibrovascular overgrowth of bulbar conjunctiva and Tenon membrane onto the cornea,1 and the etiology remains unknown. Advancing of pterygium toward the corneal center induces change in topographic refractive power and increases irregular astigmatism, resulting in impaired visual acuity.2–7 Pterygium excision surgery can restore corneal topography and improve visual acuity. Postoperative change in corneal astigmatism increases with the size of pterygium excised, although corneal disorder may persist.4,6,7 It has been anticipated that excision of larger pterygium results in larger residual astigmatism and slow restoration of corneal topography. However, there were no previous studies that evaluated time-course changes in postoperative corneal topography regarding different pterygium size. In addition, previous studies assessing From the Miyata Eye Hospital, Miyazaki, Japan. The authors have no funding or conflicts of interest to disclose. Presented at the ARVO Annual Meeting, Seattle, WA, 2013. Address correspondence to Ryohei Nejima, M.D., Miyata Eye Hospital, 6-3 Kurahara-cho, Miyakonojo, Miyazaki, 885-0051 Japan; e-mail: [email protected] Accepted June 10, 2014. DOI: 10.1097/ICL.0000000000000065
58
M.D.,
Yumi Hasegawa,
M.D.,
corneal topography evaluated with limited number of subjects.8–12 In-depth analysis of the size effect would require sufficient number of subjects. The purpose of this retrospective study is to evaluate time-course changes in corneal topography after primary pterygium excision and the effect of pterygium size in postoperative restoration of corneal topography.
METHODS This retrospective study reviewed medical records of eyes that underwent primary pterygium excision on the nasal side at Miyata Eye Hospital and were followed up during 12 months after the excision. Eyes with history of corneal trauma, corneal scarring, or ocular surgery were excluded. This study followed the tenets of the Declaration of Helsinki and was approved by the Institutional Review Board of Miyata Eye Hospital. Written consent for the procedure and for utilization of clinical data for scientific purposes was obtained from all patients. Subjects were divided into three groups according to the position of the advancing pterygium edge with respect to corneal diameter: extension of the edge to one third of the corneal diameter (grade 1), between one third of the corneal diameter and the pupil (grade 2), and within the pupillary area (grade 3). Representative cases are shown in Figure 1. All excision surgeries were performed using the same procedure. Pterygium was removed bluntly, subconjuctival fibrous tissue was removed, and abnormal scarring tissue on the cornea was polished. After administrating 0.04% mitomycin C (MMC) for 1 min, the bare sclera was covered by sliding adjacent superior or inferior conjunctiva. Postoperative medication until 6 months included 0.5% levofloxacin eye drop (Cravit, Santen, Osaka, Japan) 4 times per day, and 0.1% betamethasone sodium phosphate (Rinderon, Shionogi, Osaka, Japan) that was replaced with 0.1% fluorometholone (Flumetholon, Santen) shortly afterward. Recurrence was diagnosed when the extended tissue was found within the cornea. Best-corrected distance visual acuity (BCVA) and corneal topography was measured preoperatively, and 1, 3, 6, and 12 months postoperatively. Corneal topography was measured using TMS-2 Corneal Topographer (Tomey, Nagoya, Japan). Refractive power of the corneal surface was calculated based on simulated keratometry (SimK) provided by the topographer.5 Corneal refractive power was obtained by averaging SimK values at the steepest and flattest meridians, and corneal astigmatism as the difference between SimK values. Surface regularity index (SRI) and surface asymmetry index (SAI) were used to evaluate corneal irregularity. Eye & Contact Lens Volume 41, Number 1, January 2015
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Eye & Contact Lens Volume 41, Number 1, January 2015
Topographic Change After Primary Pterygium Surgery
FIG. 1. grade.
Eyes with pterygium recurrence during 12 months were not excluded. Results are expressed as mean6standard deviation. Timecourse changes in topography after surgery were examined with each grade using paired analysis of variance (ANOVA) and Bonferroni multiple comparison. Restoration in corneal refractive power, astigmatism, and irregularities were also compared using one-way ANOVA. Best-corrected visual acuity was compared using the Kruskal–Wallis test and the Steel–Dwass multiple comparison. P,0.05 was considered as statistically significant.
RESULTS This study included 562 eyes of 464 patients (170 men, 294 women; mean age, 66.269.1 years). Pterygia were developed in 254 right and 308 left eyes. Mean BCVA was 0.05360.219 logMAR preoperatively and 20.03060.211 logMAR 12 months postoperatively. Mean preoperative corneal refractive power and astigmatism were 43.5961.66 and 3.0062.70 diopters (D), respectively. Mean corneal irregularities were 0.90960.586 in SRI and 0.86960.881 in SAI. The numbers of eyes in each size grade were 119, 338, and 105 of grades 1 to 3, respectively. Demographic data for the three grades are shown in Table 1. Preoperative BCVA degraded with a higher size grade (P,0.0013). Corneal refractive power decreased significantly with the grade (P,0.001), whereas corneal astigmatism, SRI, and SAI increased (P,0.001). Postoperative BCVA in grade 3 was significantly worse than in grades 1 and 2 (P,0.006). There were recurrences in 22 eyes (3.9%) from 2 to 8 months (mean: 4 months).
TABLE 1. Pterygium Size N (eye) Sex, male/female (eye) Age, y Preoperative BCVA, logMAR Preoperative corneal refraction (D) Preoperative corneal astigmatism (D) Preoperative SRI Preoperative SAI Postoperative BCVA, 12 months, logMAR Recurrence rate, % Recurrence duration, mo
Representative cases of each pterygium size
Change in Corneal Refractive Power and Astigmatism Changes in corneal refractive power and astigmatism of the 3 grades are shown in Figure 2. During 12 months, grade 1 was relatively stable with 20.18% of change in the corneal refractive power and 27.70% in astigmatism, whereas there were significant differences between 1 and 12 months and 1 and 6 months, respectively. Corneal astigmatism in grade 2 did not change (27.85% of change in 12 months), although the corneal refractive power (20.40% of change) showed significant differences until 6 months. In contrast, changes in grade 3 were 20.94% and 229.2% in the corneal refractive power and astigmatism, respectively, that were approximately 2 and 4 times larger than grades 1 and 2. Continuous changes were observed during 12 months with significant differences between 1 month and 3 to 12 months in corneal refractive power and astigmatism (P#0.005). In comparison of pterygium sizes (Fig. 3), corneal refractive power in grades 2 and 3 showed a significant difference from that in grade 1 until 3 months. In corneal astigmatism, there were significant differences until 6 months in grade 2, whereas grade 3 retained higher than grade 1 over 12 months.
Change in Corneal Irregularities Figure 4 shows changes in corneal irregularities, SRI, and SAI. Changes in grade 1 during 12 months were 212.1% in SRI and 28.19% in SAI with no significant difference. In grade 2, SRI and SAI changed 226.4% and 215.1%, respectively. There were significant differences between all points except for between 3 and 6 months in the SRI, and between 1 and 6–12 months in the SAI. Change rates in grade 3 were 229.0% and 229.1%, respectively. Surface regularity index and SAI in grade 3 continued to decrease over 12 months.
Demographic Data of Each Pterygium Size Grade Grade 1
Grade 2
Grade 3
P
119 28/91 65.369.1 20.0160.19 44.5161.29 0.8260.49 0.6360.37 0.4860.30 20.0560.16 3.4 4.061.2
338 123/215 66.068.7 0.0560.22 43.5461.66 2.7562.13 0.7860.42 0.7060.42 20.0460.21 3.8 3.861.6
105 43/62 68.868.9 0.1560.20 42.7161.54 6.2062.79 1.6360.70 1.8661.50 0.0260.26 4.8 4.563.0
0.005a ,0.001b ,0.001a ,0.001a ,0.001a ,0.001a ,0.021b
The data are expressed as the mean6standard deviation. a
One-way analysis of variance.
b
Kruskal–Wallis test.
BCVA, best-corrected visual acuity; SAI, surface asymmetry index; SRI, surface regularity index.
© 2014 Contact Lens Association of Ophthalmologists
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Eye & Contact Lens Volume 41, Number 1, January 2015
R. Nejima et al.
FIG. 2. Postoperative changes in corneal refractive power ( with the left axis) and astigmatism (B with the right axis) of the three pterygium size grades. P value denotes a significant difference over time.
FIG. 3. Comparison of the pterygium size regarding changes of corneal refractive power (A) and astigmatism (B). P value denotes a significant difference between grades.
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Eye & Contact Lens Volume 41, Number 1, January 2015
Topographic Change After Primary Pterygium Surgery
FIG. 4. Postoperative changes in surface regularity index ( with the left axis) and surface asymmetry index (B with the right axis) of the three pterygium size grades. P value denotes a significant difference over time.
Comparison of the pterygium size is shown in Figure 5. Surface regularity index of grade 2 reduced to the level of grade 1 until 6 months, whereas grade 3 required more than 6 months. In the SAI, grade 2 was reduced to the level of grade 1 from 1 month postoperatively; however, grade 3 was significantly higher than other grades until 6 months.
DISCUSSION Several studies that assessed topographic changes after pterygium excision reported that corneal spherical refraction increased and the corneal cylindrical refraction and irregular astigmatism decreased postoperatively.8–12 In previous studies, the number of subjects was limited to 16 to 120, whereas investigation of the recurrent rate was analyzed in hundreds of subjects.13,14 This study assessed postoperative topographic changes using over 460 subjects. Comparisons in the previous studies were performed between the preoperative and one point of postoperative visit without an observation of the time-course change. The effect of pterygium size was not examined as well. Ozdemir and Cinal9 evaluated changes at 2 weeks and 3 months postoperatively, demonstrating that major changes were induced in the early period, although a longer period required for the restoration of corneal topography coincided well with the results in this study: pterygium of grade 1 or 2 could © 2014 Contact Lens Association of Ophthalmologists
restore corneal topography in 1 to 3 months, whereas that of grade 3 required 6 to 12 months for restoration. Advanced pterygium induces decreasing corneal spherical refraction by flattening the corneal surface and increasing the corneal astigmatism,2,4,5 and excision surgery restores the corneal change because of pterygium.3,5,8,11 Eye with a large pterygium need a longer period to recover to the normal shape. Tomidokoro et al.5 revealed that the pterygium size was correlated with postoperative changes in the corneal refractive power, which was also found in this study. Furthermore, a major change in corneal refractive power was observed until 1 month postoperatively in all grades, and there was a slow change afterward in grades 2 and 3. It was speculated that large pterygium covering the pupil could induce critical changes in the corneal shape and deformation on Bowman membrane, therefore the restoration of corneal topography required more time. Comparison of the four surgical techniques found that the use of conjunctival autograft and MMC induced less corneal refractive changes postoperatively than the bare sclera technique.10 Even so, the current excision surgery for grade 3 pterygium required a longer time for the restoration of corneal topography. Best-corrected visual acuity is degraded with corneal irregularity.15,16 An SRI exceeding 1.3 would result in a BCVA of 0.0 logMAR or worse in normal and keratoconus eyes.16 Although 61
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Eye & Contact Lens Volume 41, Number 1, January 2015
R. Nejima et al.
FIG. 5. Comparison of pterygium size regarding changes of surface regularity index (A) and surface asymmetry index (B). P value denotes a significant difference between the size grades.
the SRI in grade 3 was not significantly worse than those in grades 1 and 2 at 12 months, the BCVA (0.02260.256 logMAR) was worse than the others. It was considered that other factors influence the postoperative BCVA. Fourier17 or high-order aberration analyses6,7 of corneal topography would be necessary for further investigation. Several techniques of pterygium excision surgery have been developed. The literature analysis suggested that the use of conjunctival autograft or MMC significantly reduced recurrence rate compared with bare sclera technique.13 While the bare sclera technique resulted in the least postoperative topographic irregularity in the comparison by Yilmaz et al.,12 there was no significant difference between techniques using conjunctival autograft or MMC. Therefore, the current excision surgery using intraoperative MMC and conjunctival autograft was considered as acceptable for minimizing recurrence and promoting recovery of visual impairment. Placido topographer used in this study effectively captured mires on the corneal surface. Pterygium extension might disturb the images of the mires because of high irregularity of the pterygium surface. Therefore, analysis of the central 6-mm area was not appropriate. This study measured extension of pterygia with respect to the pupil area, while mean pupil diameters in a 60-year Japanese were 2.3 and 4.1 mm under mesopic and photopic illuminations, respectively.18 In grade 3, preoperative indices that were obtained from approximately central 3-mm area15 could be affected. Although all images of the mires were confirmed, artificial feature was not reported, and the preoperative indices coincided with previous studies.8–12 Therefore, the influence of disturbance in the mires was not significant. Previous studies showed that the corneal surface after excision surgery would be within a range where the placido topographer properly measured.4,12 There were some limitations to this study. First, because of the retrospective design, demographics of each grade could not be matched between groups. Larger pterygia could be found in older 62
patients. It would be also anticipated that corneal surface restoration could be slower in older patients; however, the difference of 3.5 years was not considered as significant. Second, the pupil diameter and highorder aberration were not examined. Grade 3 was diagnosed regarding the pupil diameter; however, there was no record of the pupil diameter measurement. Third, best-corrected visual acuity impairment was also caused by increase of ocular high-order aberration.6,7 Prospective assessment is required for further assessments. In conclusion, change in corneal refractive power, astigmatism, and irregularity after excision surgery varied with pterygium size. Time for restoration should be 1 to 3 months when the pterygium did not reach the pupil; a case with a larger pterygium would require 6 to 12 months for restoration of the corneal refractive power and irregularity, and over 12 months for corneal astigmatism, which resulted in slow recovery of visual acuity impairment. The restoration duration in each pterygium size indicated about when cataract or refractive surgery should be conducted to obtain a preferable outcome. In cataract surgery, the power of an intraocular lens should be determined after the corneal refractive power and astigmatism are stable. Wavefront-guided laser in situ keratomileusis would be effective when the corneal irregularity is in a stable condition. REFERENCES 1. Hirst LW. The treatment of pterygia. Surv Ophthalmol 2003;48:145–180. 2. Lin A, Stern G. Correlation between pterygium size and induced corneal astigmatism. Cornea 1998;17:28–30. 3. Stern GA, Lin A. Effect of pterygium excision on induced corneal topographic abnormalities. Cornea 1998;17:23–27. 4. Tomidokoro A, Oshika T, Amano S, et al. Quantitative analysis of regular and irregular astigmatism induced by pterygium. Cornea 1999;18:412–415. 5. Tomidokoro A, Miyata K, Sakaguchi Y, et al. Effect of pterygium on corneal spherical power and astigmatism. Ophthalmology 2000;107: 1568–1571. 6. Gumus K, Topaktas D, Goktas A, et al. The change in ocular high-order aberrations after pterygium excision with conjunctival autograft: A 1-year prospective clinical trial. Cornea 2012;31:1428–1431. 7. Pesudovs K, Figueiredo FC. Corneal first surface wavefront aberrations before and after pterygium surgery. J Refract Surg 2006;22:921–925.
Eye & Contact Lens Volume 41, Number 1, January 2015
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Eye & Contact Lens Volume 41, Number 1, January 2015 8. Bahar I, Loya N, Weinberger D, et al. Effect of pterygium surgery on corneal topography: A prospective study. Cornea 2004;23:113–117. 9. Ozdemir M, Cinal A. Early and late effects of pterygium surgery on corneal topography. Ophthalmic Surg Lasers Imaging 2005;36:451–456. 10. Yagmur M, Ozcan AA, Sari S, et al. Visual acuity and corneal topographic changes related with pterygium surgery. J Refract Surg 2005;21:166–170. 11. Errais K, Bouden J, Mili-Boussen I, et al. Effect of pterygium surgery on corneal topography. Eur J Ophthalmol 2008;18:177–181. 12. Yilmaz S, Yuksel T, Maden A. Corneal topographic change after four types of pterygium surgery. J Refract Surg 2008;24: 160–165. 13. Kaufman SC, Jacobs DS, Lee WB, et al. Options and adjuvants in surgery for pterygium: A report by the American Academy of Ophthalmology. Ophthalmology 2013;120:201–208.
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Topographic Change After Primary Pterygium Surgery 14. Al Fayez MF. Limbal-conjunctival vs conjunctival autograft transplant for recurrent pterygia: A prospective randomized controlled trial. JAMA Ophthalmol 2013;131:11–16. 15. Wilson SE, Klyce SD. Quantitative descriptors of corneal topography. A clinical study. Arch Ophthalmol 1991;109:349–353. 16. Shiotani Y, Maeda N, Inoue T, et al. Comparison of topographic indices that correlate with visual acuity in videokeratography. Ophthalmology 2000; 107:559–564. 17. Oshika T, Sugita G, Tanabe T, et al. Regular and irregular astigmatism after superior versus temporal scleral incision cataract surgery. Ophthalmology 2000;107:2049–2053. 18. Nakamura K, Bissen-Miyajima H, Oki S, et al. Pupil sizes in different Japanese age groups and the implications for intraocular lens choice. J Cataract Refract Surg 2009;35:134–138.
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Topographic Changes After Excision Surgery of Primary Pterygia and the Effect of Pterygium Size on Topograpic Restoration Ryohei Nejima,
M.D.,
Ayami Masuda,
M.D.,
Keiichiro Minami, Ph.D., Yosai Mori, and Kazunori Miyata, M.D. Ph.D.
Objective: To assess the effect of pterygium size on time-course change of corneal topography after excision surgery of primary pterygium. Methods: Retrospective case series included eyes that underwent excisions of primary pterygium. Pterygium size was graded according to the advancing edge position: less than one third of corneal diameter (grade 1), outside the pupil (grade 2), and within the pupillary area (grade 3). Time-course changes in corneal refractive power, astigmatism, and irregularity (surface regularity and asymmetry indices) in corneal topographies over 12 months postoperatively were compared between the pterygium size grades. Results: Pterygium excision was performed on 562 eyes, consisting of 119, 338, and 105 eyes with grades 1 to 3, respectively. Grade 1 did not change in corneal irregularity, and there was no difference between grades 1 and 2, except for corneal astigmatism at 6 months. Grade 3 showed significantly higher corneal refractive power and irregularity than grade 1 until 3 and 6 months, respectively, whereas corneal astigmatism was higher over 12 months. Conclusions: Topographic changes after primary pterygium excision were associated with pterygium size. Pterygium advancing over the pupillary area required 6 to 12 months for corneal topography restoration, resulting in slow recovery of visual acuity. Key Words: Pterygium—Topography—Irregular astigmatism. (Eye & Contact Lens 2015;41: 58–63)
P
terygium is a fibrovascular overgrowth of bulbar conjunctiva and Tenon membrane onto the cornea,1 and the etiology remains unknown. Advancing of pterygium toward the corneal center induces change in topographic refractive power and increases irregular astigmatism, resulting in impaired visual acuity.2–7 Pterygium excision surgery can restore corneal topography and improve visual acuity. Postoperative change in corneal astigmatism increases with the size of pterygium excised, although corneal disorder may persist.4,6,7 It has been anticipated that excision of larger pterygium results in larger residual astigmatism and slow restoration of corneal topography. However, there were no previous studies that evaluated time-course changes in postoperative corneal topography regarding different pterygium size. In addition, previous studies assessing From the Miyata Eye Hospital, Miyazaki, Japan. The authors have no funding or conflicts of interest to disclose. Presented at the ARVO Annual Meeting, Seattle, WA, 2013. Address correspondence to Ryohei Nejima, M.D., Miyata Eye Hospital, 6-3 Kurahara-cho, Miyakonojo, Miyazaki, 885-0051 Japan; e-mail: [email protected] Accepted June 10, 2014. DOI: 10.1097/ICL.0000000000000065
58
M.D.,
Yumi Hasegawa,
M.D.,
corneal topography evaluated with limited number of subjects.8–12 In-depth analysis of the size effect would require sufficient number of subjects. The purpose of this retrospective study is to evaluate time-course changes in corneal topography after primary pterygium excision and the effect of pterygium size in postoperative restoration of corneal topography.
METHODS This retrospective study reviewed medical records of eyes that underwent primary pterygium excision on the nasal side at Miyata Eye Hospital and were followed up during 12 months after the excision. Eyes with history of corneal trauma, corneal scarring, or ocular surgery were excluded. This study followed the tenets of the Declaration of Helsinki and was approved by the Institutional Review Board of Miyata Eye Hospital. Written consent for the procedure and for utilization of clinical data for scientific purposes was obtained from all patients. Subjects were divided into three groups according to the position of the advancing pterygium edge with respect to corneal diameter: extension of the edge to one third of the corneal diameter (grade 1), between one third of the corneal diameter and the pupil (grade 2), and within the pupillary area (grade 3). Representative cases are shown in Figure 1. All excision surgeries were performed using the same procedure. Pterygium was removed bluntly, subconjuctival fibrous tissue was removed, and abnormal scarring tissue on the cornea was polished. After administrating 0.04% mitomycin C (MMC) for 1 min, the bare sclera was covered by sliding adjacent superior or inferior conjunctiva. Postoperative medication until 6 months included 0.5% levofloxacin eye drop (Cravit, Santen, Osaka, Japan) 4 times per day, and 0.1% betamethasone sodium phosphate (Rinderon, Shionogi, Osaka, Japan) that was replaced with 0.1% fluorometholone (Flumetholon, Santen) shortly afterward. Recurrence was diagnosed when the extended tissue was found within the cornea. Best-corrected distance visual acuity (BCVA) and corneal topography was measured preoperatively, and 1, 3, 6, and 12 months postoperatively. Corneal topography was measured using TMS-2 Corneal Topographer (Tomey, Nagoya, Japan). Refractive power of the corneal surface was calculated based on simulated keratometry (SimK) provided by the topographer.5 Corneal refractive power was obtained by averaging SimK values at the steepest and flattest meridians, and corneal astigmatism as the difference between SimK values. Surface regularity index (SRI) and surface asymmetry index (SAI) were used to evaluate corneal irregularity. Eye & Contact Lens Volume 41, Number 1, January 2015
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Eye & Contact Lens Volume 41, Number 1, January 2015
Topographic Change After Primary Pterygium Surgery
FIG. 1. grade.
Eyes with pterygium recurrence during 12 months were not excluded. Results are expressed as mean6standard deviation. Timecourse changes in topography after surgery were examined with each grade using paired analysis of variance (ANOVA) and Bonferroni multiple comparison. Restoration in corneal refractive power, astigmatism, and irregularities were also compared using one-way ANOVA. Best-corrected visual acuity was compared using the Kruskal–Wallis test and the Steel–Dwass multiple comparison. P,0.05 was considered as statistically significant.
RESULTS This study included 562 eyes of 464 patients (170 men, 294 women; mean age, 66.269.1 years). Pterygia were developed in 254 right and 308 left eyes. Mean BCVA was 0.05360.219 logMAR preoperatively and 20.03060.211 logMAR 12 months postoperatively. Mean preoperative corneal refractive power and astigmatism were 43.5961.66 and 3.0062.70 diopters (D), respectively. Mean corneal irregularities were 0.90960.586 in SRI and 0.86960.881 in SAI. The numbers of eyes in each size grade were 119, 338, and 105 of grades 1 to 3, respectively. Demographic data for the three grades are shown in Table 1. Preoperative BCVA degraded with a higher size grade (P,0.0013). Corneal refractive power decreased significantly with the grade (P,0.001), whereas corneal astigmatism, SRI, and SAI increased (P,0.001). Postoperative BCVA in grade 3 was significantly worse than in grades 1 and 2 (P,0.006). There were recurrences in 22 eyes (3.9%) from 2 to 8 months (mean: 4 months).
TABLE 1. Pterygium Size N (eye) Sex, male/female (eye) Age, y Preoperative BCVA, logMAR Preoperative corneal refraction (D) Preoperative corneal astigmatism (D) Preoperative SRI Preoperative SAI Postoperative BCVA, 12 months, logMAR Recurrence rate, % Recurrence duration, mo
Representative cases of each pterygium size
Change in Corneal Refractive Power and Astigmatism Changes in corneal refractive power and astigmatism of the 3 grades are shown in Figure 2. During 12 months, grade 1 was relatively stable with 20.18% of change in the corneal refractive power and 27.70% in astigmatism, whereas there were significant differences between 1 and 12 months and 1 and 6 months, respectively. Corneal astigmatism in grade 2 did not change (27.85% of change in 12 months), although the corneal refractive power (20.40% of change) showed significant differences until 6 months. In contrast, changes in grade 3 were 20.94% and 229.2% in the corneal refractive power and astigmatism, respectively, that were approximately 2 and 4 times larger than grades 1 and 2. Continuous changes were observed during 12 months with significant differences between 1 month and 3 to 12 months in corneal refractive power and astigmatism (P#0.005). In comparison of pterygium sizes (Fig. 3), corneal refractive power in grades 2 and 3 showed a significant difference from that in grade 1 until 3 months. In corneal astigmatism, there were significant differences until 6 months in grade 2, whereas grade 3 retained higher than grade 1 over 12 months.
Change in Corneal Irregularities Figure 4 shows changes in corneal irregularities, SRI, and SAI. Changes in grade 1 during 12 months were 212.1% in SRI and 28.19% in SAI with no significant difference. In grade 2, SRI and SAI changed 226.4% and 215.1%, respectively. There were significant differences between all points except for between 3 and 6 months in the SRI, and between 1 and 6–12 months in the SAI. Change rates in grade 3 were 229.0% and 229.1%, respectively. Surface regularity index and SAI in grade 3 continued to decrease over 12 months.
Demographic Data of Each Pterygium Size Grade Grade 1
Grade 2
Grade 3
P
119 28/91 65.369.1 20.0160.19 44.5161.29 0.8260.49 0.6360.37 0.4860.30 20.0560.16 3.4 4.061.2
338 123/215 66.068.7 0.0560.22 43.5461.66 2.7562.13 0.7860.42 0.7060.42 20.0460.21 3.8 3.861.6
105 43/62 68.868.9 0.1560.20 42.7161.54 6.2062.79 1.6360.70 1.8661.50 0.0260.26 4.8 4.563.0
0.005a ,0.001b ,0.001a ,0.001a ,0.001a ,0.001a ,0.021b
The data are expressed as the mean6standard deviation. a
One-way analysis of variance.
b
Kruskal–Wallis test.
BCVA, best-corrected visual acuity; SAI, surface asymmetry index; SRI, surface regularity index.
© 2014 Contact Lens Association of Ophthalmologists
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Eye & Contact Lens Volume 41, Number 1, January 2015
R. Nejima et al.
FIG. 2. Postoperative changes in corneal refractive power ( with the left axis) and astigmatism (B with the right axis) of the three pterygium size grades. P value denotes a significant difference over time.
FIG. 3. Comparison of the pterygium size regarding changes of corneal refractive power (A) and astigmatism (B). P value denotes a significant difference between grades.
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Eye & Contact Lens Volume 41, Number 1, January 2015
Topographic Change After Primary Pterygium Surgery
FIG. 4. Postoperative changes in surface regularity index ( with the left axis) and surface asymmetry index (B with the right axis) of the three pterygium size grades. P value denotes a significant difference over time.
Comparison of the pterygium size is shown in Figure 5. Surface regularity index of grade 2 reduced to the level of grade 1 until 6 months, whereas grade 3 required more than 6 months. In the SAI, grade 2 was reduced to the level of grade 1 from 1 month postoperatively; however, grade 3 was significantly higher than other grades until 6 months.
DISCUSSION Several studies that assessed topographic changes after pterygium excision reported that corneal spherical refraction increased and the corneal cylindrical refraction and irregular astigmatism decreased postoperatively.8–12 In previous studies, the number of subjects was limited to 16 to 120, whereas investigation of the recurrent rate was analyzed in hundreds of subjects.13,14 This study assessed postoperative topographic changes using over 460 subjects. Comparisons in the previous studies were performed between the preoperative and one point of postoperative visit without an observation of the time-course change. The effect of pterygium size was not examined as well. Ozdemir and Cinal9 evaluated changes at 2 weeks and 3 months postoperatively, demonstrating that major changes were induced in the early period, although a longer period required for the restoration of corneal topography coincided well with the results in this study: pterygium of grade 1 or 2 could © 2014 Contact Lens Association of Ophthalmologists
restore corneal topography in 1 to 3 months, whereas that of grade 3 required 6 to 12 months for restoration. Advanced pterygium induces decreasing corneal spherical refraction by flattening the corneal surface and increasing the corneal astigmatism,2,4,5 and excision surgery restores the corneal change because of pterygium.3,5,8,11 Eye with a large pterygium need a longer period to recover to the normal shape. Tomidokoro et al.5 revealed that the pterygium size was correlated with postoperative changes in the corneal refractive power, which was also found in this study. Furthermore, a major change in corneal refractive power was observed until 1 month postoperatively in all grades, and there was a slow change afterward in grades 2 and 3. It was speculated that large pterygium covering the pupil could induce critical changes in the corneal shape and deformation on Bowman membrane, therefore the restoration of corneal topography required more time. Comparison of the four surgical techniques found that the use of conjunctival autograft and MMC induced less corneal refractive changes postoperatively than the bare sclera technique.10 Even so, the current excision surgery for grade 3 pterygium required a longer time for the restoration of corneal topography. Best-corrected visual acuity is degraded with corneal irregularity.15,16 An SRI exceeding 1.3 would result in a BCVA of 0.0 logMAR or worse in normal and keratoconus eyes.16 Although 61
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Eye & Contact Lens Volume 41, Number 1, January 2015
R. Nejima et al.
FIG. 5. Comparison of pterygium size regarding changes of surface regularity index (A) and surface asymmetry index (B). P value denotes a significant difference between the size grades.
the SRI in grade 3 was not significantly worse than those in grades 1 and 2 at 12 months, the BCVA (0.02260.256 logMAR) was worse than the others. It was considered that other factors influence the postoperative BCVA. Fourier17 or high-order aberration analyses6,7 of corneal topography would be necessary for further investigation. Several techniques of pterygium excision surgery have been developed. The literature analysis suggested that the use of conjunctival autograft or MMC significantly reduced recurrence rate compared with bare sclera technique.13 While the bare sclera technique resulted in the least postoperative topographic irregularity in the comparison by Yilmaz et al.,12 there was no significant difference between techniques using conjunctival autograft or MMC. Therefore, the current excision surgery using intraoperative MMC and conjunctival autograft was considered as acceptable for minimizing recurrence and promoting recovery of visual impairment. Placido topographer used in this study effectively captured mires on the corneal surface. Pterygium extension might disturb the images of the mires because of high irregularity of the pterygium surface. Therefore, analysis of the central 6-mm area was not appropriate. This study measured extension of pterygia with respect to the pupil area, while mean pupil diameters in a 60-year Japanese were 2.3 and 4.1 mm under mesopic and photopic illuminations, respectively.18 In grade 3, preoperative indices that were obtained from approximately central 3-mm area15 could be affected. Although all images of the mires were confirmed, artificial feature was not reported, and the preoperative indices coincided with previous studies.8–12 Therefore, the influence of disturbance in the mires was not significant. Previous studies showed that the corneal surface after excision surgery would be within a range where the placido topographer properly measured.4,12 There were some limitations to this study. First, because of the retrospective design, demographics of each grade could not be matched between groups. Larger pterygia could be found in older 62
patients. It would be also anticipated that corneal surface restoration could be slower in older patients; however, the difference of 3.5 years was not considered as significant. Second, the pupil diameter and highorder aberration were not examined. Grade 3 was diagnosed regarding the pupil diameter; however, there was no record of the pupil diameter measurement. Third, best-corrected visual acuity impairment was also caused by increase of ocular high-order aberration.6,7 Prospective assessment is required for further assessments. In conclusion, change in corneal refractive power, astigmatism, and irregularity after excision surgery varied with pterygium size. Time for restoration should be 1 to 3 months when the pterygium did not reach the pupil; a case with a larger pterygium would require 6 to 12 months for restoration of the corneal refractive power and irregularity, and over 12 months for corneal astigmatism, which resulted in slow recovery of visual acuity impairment. The restoration duration in each pterygium size indicated about when cataract or refractive surgery should be conducted to obtain a preferable outcome. In cataract surgery, the power of an intraocular lens should be determined after the corneal refractive power and astigmatism are stable. Wavefront-guided laser in situ keratomileusis would be effective when the corneal irregularity is in a stable condition. REFERENCES 1. Hirst LW. The treatment of pterygia. Surv Ophthalmol 2003;48:145–180. 2. Lin A, Stern G. Correlation between pterygium size and induced corneal astigmatism. Cornea 1998;17:28–30. 3. Stern GA, Lin A. Effect of pterygium excision on induced corneal topographic abnormalities. Cornea 1998;17:23–27. 4. Tomidokoro A, Oshika T, Amano S, et al. Quantitative analysis of regular and irregular astigmatism induced by pterygium. Cornea 1999;18:412–415. 5. Tomidokoro A, Miyata K, Sakaguchi Y, et al. Effect of pterygium on corneal spherical power and astigmatism. Ophthalmology 2000;107: 1568–1571. 6. Gumus K, Topaktas D, Goktas A, et al. The change in ocular high-order aberrations after pterygium excision with conjunctival autograft: A 1-year prospective clinical trial. Cornea 2012;31:1428–1431. 7. Pesudovs K, Figueiredo FC. Corneal first surface wavefront aberrations before and after pterygium surgery. J Refract Surg 2006;22:921–925.
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Eye & Contact Lens Volume 41, Number 1, January 2015 8. Bahar I, Loya N, Weinberger D, et al. Effect of pterygium surgery on corneal topography: A prospective study. Cornea 2004;23:113–117. 9. Ozdemir M, Cinal A. Early and late effects of pterygium surgery on corneal topography. Ophthalmic Surg Lasers Imaging 2005;36:451–456. 10. Yagmur M, Ozcan AA, Sari S, et al. Visual acuity and corneal topographic changes related with pterygium surgery. J Refract Surg 2005;21:166–170. 11. Errais K, Bouden J, Mili-Boussen I, et al. Effect of pterygium surgery on corneal topography. Eur J Ophthalmol 2008;18:177–181. 12. Yilmaz S, Yuksel T, Maden A. Corneal topographic change after four types of pterygium surgery. J Refract Surg 2008;24: 160–165. 13. Kaufman SC, Jacobs DS, Lee WB, et al. Options and adjuvants in surgery for pterygium: A report by the American Academy of Ophthalmology. Ophthalmology 2013;120:201–208.
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Topographic Change After Primary Pterygium Surgery 14. Al Fayez MF. Limbal-conjunctival vs conjunctival autograft transplant for recurrent pterygia: A prospective randomized controlled trial. JAMA Ophthalmol 2013;131:11–16. 15. Wilson SE, Klyce SD. Quantitative descriptors of corneal topography. A clinical study. Arch Ophthalmol 1991;109:349–353. 16. Shiotani Y, Maeda N, Inoue T, et al. Comparison of topographic indices that correlate with visual acuity in videokeratography. Ophthalmology 2000; 107:559–564. 17. Oshika T, Sugita G, Tanabe T, et al. Regular and irregular astigmatism after superior versus temporal scleral incision cataract surgery. Ophthalmology 2000;107:2049–2053. 18. Nakamura K, Bissen-Miyajima H, Oki S, et al. Pupil sizes in different Japanese age groups and the implications for intraocular lens choice. J Cataract Refract Surg 2009;35:134–138.
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