CLINICAL SCIENCES Effect of Extraction on the Visual Fields of Patients With Glaucoma

Monica M. Carrillo, MD; Paul H. Artes, PhD; Marcelo T. Nicolela, MD; Raymond P. LeBlanc, MD; Balwantray C. Chauhan, PhD

Objective: To investigate the effect of cataract extrac- the effect and control analyses was less than 0.1 dB and tion on the visual fields of patients with open-angle not statistically significant (P=.85). There was a strong glaucoma. correlation between change in foveal sensitivity and change in mean deviation in the effect analysis but not Methods: Patients in a prospective cohort study in a ter- in the control analysis (r=0.76 [PϽ.001] and r=0.30 tiary center underwent standard automated perimetry ev- [P=.08], respectively). There was no relationship be- ery 6 months. We compared the mean results of the 2 tween change in visual acuity or initial mean deviation examinations immediately before and 2 examinations im- and change in mean deviation in either analysis. Change mediately after phacoemulsification cataract extraction in pointwise total deviation was not systematically re- and intraocular implant (effect analysis) and the mean lated to the respective baseline value in either analysis; results of the first 2 and last 2 examinations from 4 con- however, the variance of the distribution of change in total secutive examinations obtained more than 1 year after deviation was significantly higher in the effect analysis the (control analysis). (PϽ.001).

Results: Our sample contained 34 of 26 patients Conclusion: While there was an improvement in best- (mean±SD age, 69.2±10.8 years). While the mean log- corrected visual acuity after cataract surgery, the changes MAR best-corrected visual acuity improved signifi- in the visual field as a group were negligible. cantly by approximately 2 Snellen lines after surgery (PϽ.001), the average change in mean deviation in both Arch Ophthalmol. 2005;123:929-932

TATIC AUTOMATED PERIMETRY seen in glaucoma is unlikely to be related is a well-established and to cataract.2,5 essential tool in the diagno- The effect of cataract surgery on the vi- sis and long-term manage- sual field has been studied previously in ment of glaucoma. The healthy subjects and glaucoma patients us- developmentS of cataract in patients with ing manual6 and automated7-10 perim- glaucoma may exacerbate the visual field etry. In studies with glaucoma patients, loss and may make it difficult to distin- there was a range of visual field damage guish between visual field changes due to and the density of cataract, and while most cataract and those due to the progression studies found an increase in visual field of glaucoma. sensitivity after cataract surgery, there is are thought to cause visual considerable variance in the results, with degradation by 3 mechanisms: image some studies showing a meaningful effect7 blur, light scattering, and decreased illu- and others showing a modest or no effect.10 mination.1 Investigation of the effect of In this study, we report the effect of cataract or light scattering (simulated cataract extraction on a group of glau- cataract) on the visual field has generally coma patients followed up in a longitudi- shown that cataract results in diffuse nal prospective study. In contrast to other reduction of sensitivity in healthy sub- studies, we computed a mean of 2 fields Author Affiliations: 2-5 Department of jects. Although the pattern of sensitiv- before and after surgery and used a paired and Visual Sciences, Dalhousie ity loss may not be entirely uniform control analysis in the same eyes to cor- University, Halifax, Nova Scotia. across the visual field, predominantly rect for any possible regression to the mean Financial Disclosure: None. localized field loss such as that frequently effect and visual field progression.

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©2005 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/24/2021 Informed consent was obtained from all subjects, and the te- A B nets of the Declaration of Helsinki were followed. 0.5 In the effect analysis, we compared the mean results of the 2 visual fields immediately before and immediately after sur- 0.4 gery. In the control analysis, the mean results of the first 2 and 0.3 last 2 field examinations from 4 consecutive examinations ob- 0.2 tained more than 1 year after surgery were compared. In this

0.1 case, the first 2 fields constituted the equivalent of the presur- gery fields and the latter 2 the postsurgery fields. Visual field 0 data were averaged by computing the mean pointwise total de-

Postsurgery Visual Acuity, logMAR Postsurgery Visual Acuity, viation (TD). The visual acuity data were averaged correspond- –0.1 0 0.1 0.2 0.3 0.4 0.5 –0.1 0 0.1 0.2 0.3 0.4 0.5 Presurgery Visual Acuity, logMAR ing to the dates of the visual field examinations. We examined pointwise and global changes in TD stratified according to the respective baseline values. The mean and standard deviation Figure 1. Change in visual acuity in the effect (A) and control (B) analyses. of TD yielded the unweighted MD and pattern standard devia- The diagonal line indicates equal values before and after surgery. tion indexes, respectively. To study the influence of visual field eccentricity on pointwise TD, the visual field was divided into 2 zones: zone 1, stimuli within 16° eccentricity; and zone 2, A B 0 stimuli outside 16° eccentricity. To study the effect of baseline pointwise TD on the change in TD in the effect and control analy- –5 ses, the data were binned across all patients in 5-dB steps cen-

–10 tered on −30 dB, −25 dB, and so on. The presurgery and postsurgery data were compared using –15 either a paired t test or a Wilcoxon matched-pairs signed rank test. PϽ.05 was considered statistically significant. –20 Mean Deviation After Surgery, dB Mean Deviation After Surgery, –25 –20 –15 –10 –5 0 –25 –20 –15 –10 –5 0 RESULTS Mean Deviation Before Surgery, dB

Figure 2. Change in mean deviation in the effect (A) and control (B) Thirty-four eyes of 26 patients (mean±SD age, 69.2±10.8 analyses. The diagonal line indicates equal values before and after surgery. years) were included in the study. In the effect analysis, the mean±SD time between the first visual field exami- nation before surgery and the last visual field examina- METHODS tion after surgery was 19.9±6.8 months, while that in the control analysis was 17.3±6.6 months. Data for this study were obtained from a longitudinal prospec- Thirty (88%) of the 34 eyes underwent phacoemul- tive study that began in September 1991, in which various psy- sification cataract surgery with implan- chophysical tests and scanning laser tomography were per- tation, while 4 (12%) underwent combined phacoemul- formed in a group of patients with open-angle glaucoma. Patients sification cataract surgery with intraocular lens were recruited consecutively from the practice of one of us (R.P.L.) and the Glaucoma Clinic of the Care Centre of the implantation and . Queen Elizabeth II Health Science Centre, Halifax. The mean logMAR best-corrected visual acuity Inclusion criteria were as follows: (1) best-corrected visual improved significantly (PϽ.001) from a mean of 0.24 acuity of at least 6/12; (2) diagnosis of open-angle glaucoma (range, 0.00-0.48) to 0.07 (range, 0.00-0.33), or with glaucomatous optic disc damage, such as notching or pro- approximately 2 Snellen lines of visual acuity, after sur- gressive thinning of the neuroretinal rim and visual field dam- gery (Figure 1A). Two (6%) of the eyes had a poorer age with an initial mean deviation (MD) between −2 and −10 postsurgical visual acuity. One of these eyes developed dB; (3) open angles by ; and (4) willingness to par- cystoid macular edema after surgery, which subse- ticipate in the study and to give informed consent. Exclusion quently resolved. In the control analysis, the change in criteria were as follows: (1) concomitant chronic ocular dis- visual acuity was not statistically significant (from 0.06 ease, (2) refractive error exceeding 5 diopters (D) spherical equivalent or3Dofastigmatism, (3) aphakia, (4) systemic dis- [range, −0.06 to 0.30] to 0.09 [range, −0.06 to 0.33], ease or systemic medication known to affect the visual field or P=.08) (Figure 1B). ability to participate in the study, (5) chronic ocular medica- In the effect analysis, there was no significant change tion other than for glaucoma, and (6) contact lens wear. All in MD (mean±SD from −6.74±3.75 to −6.68±3.96 dB, eyes included in this study underwent phacoemulsification cata- P=.85) (Figure 2A). In the control analysis, the change ract extraction and intraocular lens implantation alone or in in MD was almost identical (mean±SD from −6.46±4.15 combination with trabeculectomy, and had at least 2 visual field to −6.38±4.19 dB, P=.67) (Figure 2B). There were also results available within 1 year before surgery and at least 6 vi- no significant changes in pattern standard deviation in sual field results available after surgery. Visual field examina- either the effect or control analyses (mean±SD from tions were performed with static automated perimetry using 4.40±2.52 to 4.52±2.51 dB [P=.42] and from 4.43±2.58 either the 30-2 or 24-2 full-threshold algorithm (Humphrey Field Analyzer; Carl Zeiss Meditech, Dublin, Calif) every 6 months to 4.57±2.51 dB [P=.24], respectively). with the appropriate refractive correction. For a given patient, There was a strong positive correlation between change the same test (ie, 30-2 or 24-2) was used throughout the follow- in foveal sensitivity and MD in the effect analysis (r=0.76, up. The study protocol was approved by the Research Ethics PϽ.001) (Figure 3A), while that in the control analy- Committee of the Queen Elizabeth II Health Sciences Centre. sis was much weaker (r=0.30, P=.08) (Figure 3B). No

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©2005 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/24/2021 A B A B 6 6

4 4

2 2

0 0

–2 –2

–4 –4 Change in Mean Deviation, dB Change in Mean Deviation, dB –6 –6 –4 –2 0 2 4 6 8 –6 –4 –2 0 2 4 6 8 –25 –20 –15 –10 –5 0 –25 –20 –15 –10 –5 0 Change in Foveal Sensitivity, dB Baseline Mean Deviation, dB

Figure 3. Relationship between change in mean deviation and change in Figure 5. Relationship between change in mean deviation and baseline mean foveal sensitivity in the effect (A) and control (B) analyses. deviation in the effect (A) and control (B) analyses.

A B A B 10 64 47 54 107 64 6 43 357 118 49 4 5 303 1172 413 1104 534 2 0 0

–2 –5

–4 Deviation, dB Change in Total –10 Change in Mean Deviation, dB –6 –30 –25 –20 –15 –10 –5 0 –30 –25 –20 –15 –10 –5 0 –0.5 –0.4 –0.3 –0.2 –0.1 0 0.1 0.2 0.3 –0.5 –0.4 –0.3 –0.2 –0.1 0 0.1 0.2 0.3 Baseline Total Deviation, dB Change in Visual Acuity, logMAR Figure 6. Box plots showing the change in pointwise total deviation as a Figure 4. Relationship between change in mean deviation and change in function of baseline total deviation binned in 5-dB steps in the effect (A) and visual acuity in the effect (A) and control (B) analyses. control (B) analyses. Boxes represent the 75th, 50th, and 25th percentiles, while tails represent the 90th and 10th percentiles. Data indicate the number of observations. correlations were found between change in visual acu- ity or baseline MD and change in MD (r=−0.42 [P=.41] research study and who at baseline had early to moderate and r=−0.13 [P=.46] in the effect and control analyses, visual field damage. We elected to compare the mean re- respectively [Figure 4] and r =−0.20 [P =.26] and sults of 2 visual fields presurgery and 2 visual fields post- r=0.001 [P=.99] in the effect and control analyses, re- surgery rather than use single test results to decrease the spectively [Figure 5]). impact of variability and any possible regression to the mean The distributions of the change in pointwise TD in the effect. We also performed an identical control analysis af- effect and control analyses were significantly different, ter the surgery to correct for potential visual field progres- with the variance in the effect analysis being signifi- sion during the time elapsing between visual field results cantly higher compared with the control analysis (3.51 before and after surgery. Our results indicate that there and 2.90 dB, respectively; PϽ.001, Levene test). These was a significant increase in visual acuity after cataract sur- differences persisted when the analysis was stratified ac- gery. The effect of surgery on the visual field in the group cording to visual field eccentricity (3.33 and 2.60 dB, re- as a whole was negligible, although there was consider- spectively, in zone 1, and 3.60 and 3.05 dB in zone 2, able individual variation. respectively; PϽ.001). Many reasons can guide the decision to perform cata- There seemed to be no systematic dependence of the ract surgery, among them a decline in visual acuity and/or change in pointwise TD on the baseline pointwise TD in contrast sensitivity, glare, diplopia, and factors related either the effect or control analysis (Figure 6). There to patient lifestyle. Specifically in glaucoma patients, the were no significant differences between the 2 analyses desire to better monitor the disease is a significant fac- except when the baseline TD centered at −20 dB, where tor. The fact that the mean presurgery logMAR best- the improvement in TD seemed to be better in the con- corrected visual acuity was 0.24 (between 20/30 and 20/ trol analysis (PϽ.03), and when it centered at −10 dB, 40) and the MD was −6.7 dB indicates that in contrast where the improvement in TD seemed to be better in the with most studies previously published in this area, our effect analysis (PϽ.001). patients had cataracts with lesser impact on high- contrast acuity and milder visual field damage. COMMENT Our results indicate that the variability of the change in the visual field using global and pointwise analysis was Changes in the visual field due to cataract are thought to higher in the effect analysis compared with the control confound those due to glaucoma. We performed this analy- analysis. This finding suggests that the presence of cata- sis on a group of patients followed up prospectively in a ract increases visual field variability and further that the

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©2005 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/24/2021 changes in visual field caused by cataract removal may revealed that heterogeneity of cataracts limits the corre- have been blunted by increased variability. Our deci- lation between staging of cataracts by experienced clini- sion to compute mean results of 2 examinations was an cians5 or by light scatter measurement11 and visual field attempt to offset the effects of variability but may have loss. reduced the impact of cataract surgery on visual field In summary, the present study demonstrates that while change. In addition, it is possible that comparison of the there was an improvement in best-corrected visual acu- visual field and visual acuity in examinations immedi- ity after cataract surgery, the changes in the visual field ately before and after surgery may have shown a larger in the group as a whole were negligible. There was, how- effect. While our study did not show a meaningful effect ever, interindividual variation in visual field change af- of cataract extraction on the group as a whole, in clini- ter cataract surgery, implicating the exacerbating effects cal practice it is probably still prudent to reestablish the of cataract on visual field variability. Further prospec- baseline after surgery because the effect of surgery in in- tive controlled studies with a clearly defined and stan- dividual patients was somewhat variable. dardized grading system for cataract are necessary to de- Several investigators have studied the effect of cata- termine and more clearly interpret the effect of the ract on static automated perimetry. Guthauser and Flam- different types of cataract on the visual field in the whole mer2 and Lam et al5 found a diffuse effect of cataract on spectrum of glaucoma patients. the visual field in a group of glaucoma and nonglau- coma patients. Chen and Budenz7 found that the im- provement in MD after cataract surgery depended on the level of glaucomatous field loss, with patients with more Submitted for Publication: April 19, 2004; final revi- severe loss showing more modest improvement. Differ- sion received September 23, 2004; accepted November ences between their findings and ours may relate to the 17, 2004. more advanced level of visual field loss in their series Correspondence: Balwantray C. Chauhan, PhD, Depart- (mean±SD baseline MD, −14.5±5.4 dB vs −6.7±6.1 dB ment of Ophthalmology and Visual Sciences, Dalhousie in the present study). Hayashi et al8 and Smith et al9 found University, Centennial Building, Second Floor, 1278 improvements in MD, even in subjects with dense sco- Tower Rd, Halifax, Nova Scotia, Canada B3H 2Y9 (bal tomata. Their studies included patients with more ad- @dal.ca). vanced glaucoma presurgery as well (mean±SD MD, Funding/Support: This study was supported by grant −17±7.81 dB in 78% of patients in the former study and MOP-11357 from the Canadian Institutes of Health Re- −14.19±6.9 dB in the latter study). Similar to our re- search, Ottawa, Ontario. sults, Stewart and associates10 found no appreciable change in either MD or pattern standard deviation after cataract REFERENCES surgery. They attributed their results to the generally ad- vanced level of visual field loss (63% of eyes had MD worse 1. Zuckerman JL, Miller D, Dyes W, Keller M. Degradation of vision through a simu- than −17.0 dB). Apparently, no causal relation between lated cataract. Invest Ophthalmol. 1973;12:213-224. 2. Guthauser U, Flammer J. Quantifying visual field damage caused by cataract. 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Bigger JF, Becker B. Cataracts and open-angle glaucoma: the effect of cataract 5 extraction on visual fields. Am J Ophthalmol. 1971;1:335-340. Lam et al found a significant effect of cataract surgery 7. Chen PP, Budenz DL. The effects of cataract extraction on the visual field of eyes in the central region, contrasting with a relatively minor with chronic open-angle glaucoma. Am J Ophthalmol. 1998;125:325-333. effect in the periphery by dividing the visual field into 4 8. Hayashi K, Hayashi H, Nakao F, Hayashi F. Influence of cataract surgery on au- concentric zones for analysis. Similar results were found tomated perimetry in patients with glaucoma. Am J Ophthalmol. 2001;132: by other researchers.2,7 Chen and Budenz7 calculated the 41-46. 9. Smith SD, Katz J, Quigley HA. Effect of cataract extraction on the results of au- percentage of change of the foveal sensitivity and MD by tomated perimetry in glaucoma. Arch Ophthalmol. 1997;115:1515-1519. expressing the absolute change in decibels as a fraction 10. Stewart WC, Rogers GM, Crinkley CM, Carlson AN. Effect of cataract extraction of the original value of the variable. In our study, we were on automated fields in chronic open-angle glaucoma. Arch Ophthalmol. 1995; unable to demonstrate zone-specific differences in TD af- 113:875-879. 11. Yao K, Flammer J. Relationship cataract density and visual field damage. Eur J ter cataract surgery. Ophthalmol. 1993;3:1-5. A potential weakness of our study was the lack of clini- 12. Crichton A, Mikelberg F, Douglas GR, et al. Lens opacity as a predictor of visual cal grading of cataracts. However, some studies5,11,12 have field impairment due to cataract. Can J Ophthalmol. 1990;25:287-289.

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