Comparison of color perception after tinted blue light–filtering and clear ultraviolet-filtering intraocular lens implantation

ARTICLE

Comparison of color pe

intraocular lens implantationSudarshan Kumar Khokhar, MD, Animesh Jindal, MB BS, Tushar Agarwal, MD, Anita Panda, MD

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PURPOSE: To compare color perception after implantation of clear and yellow-tinted intraocularlenses (IOLs).

SETTING: Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of MedicalSciences, New Delhi, India.

DESIGN: Comparative case series.

METHODS: This study evaluated eyes that had implantation of an Acrysof IQ SN60WF yellow-tintedIOL or an Acrysof SA60AT clear IOL. All eyes were evaluated postoperatively at 1 month and 3months. The uncorrected distance visual acuity, intraocular pressure, and color vision (Ishiharapseudoisochromatic test, Edridge-Green lantern test, Heidelberg anomaloscope, and Farnsworth-Munsell (FM) 100-hue test) were evaluated.

RESULTS: Both IOL groups comprised 50 eyes. There were no significant differences between the 2groups in color vision on any of the 4 tests (PR.05). Plotting the error scores on the polarity graphof the FM 100-hue test showed that eyes with a yellow-tinted IOL did not have a specific axis ofconfusion.

CONCLUSION: There was no difference in color perception between the 2 IOLs irrespective of thecolor vision test used.

Financial Disclosure: No author has a financial or proprietary interest in any material or methodmentioned.

J Cataract Refract Surg 2011; 37:1598–1604 Q 2011 ASCRS and ESCRS

The human crystalline lens, as it yellows with age, hasa protective effect on the retina against the short wave-length of light. However, after cataract extraction, theocular transmission of light energy is significantly in-creased in pseudophakic eyes and in aphakic eyes.1

Exposure to ultraviolet-A (315 to 400 nm) andblue light (400 to 480 nm) increases the risk for thedevelopment or progression of age-related macular

ruary 21, 2011.ubmitted: March 5, 2011.ch 8, 2011.

ajendra Prasad Centre For Ophthalmic Sciences, Allf Medical Sciences, Ansari Nagar, New Delhi, India.

author: Sudarshan Kumar Khokhar, MD, Rajendraor Ophthalmic Sciences, All India Institute of Medicalelhi 110029, India. E-mail: [email protected].

SCRS and ESCRS

by Elsevier Inc.

degeneration (AMD).2–5 Conventional clear intraocu-lar lenses (IOLs) were designed to block ultraviolet(UV) rays with wavelengths less than 400 nm; how-ever, blue light (400 to 480 nm) is not blocked.1

Yellow-tinted IOLs, which have a blue light–filteringchromophore, were designed to block blue light andprotect the retina from the potential damage causedby the short wavelength of light. However, there isconcern that the blue light–absorbing polymer con-tained in yellow IOLs affects color perception; this ef-fect has been reported in some cases, especially when 1eye has a yellow IOL and other eye has a clear IOL.6,7

Color is a purely subjective sensation. Only thephysical stimuli producing the sensation are objectiveand amenable to definition. Normal human color vi-sion is trichromatic and requires 3 types of photorecep-tor cells called cones, each of which contains differentphotopigments. If 1 or more pigments are missing,color deficiency results.8–12 Different professions use

0886-3350/$ - see front matter

doi:10.1016/j.jcrs.2011.03.044

Table 1. Characteristics of the IOLs.

Characteristic AcrySof IQ SN60WF AcrySof SA60AT

Optic material Hydrophobiccopolymer acrylate

methacrylate

Hydrophobiccopolymer acrylate

methacrylateOptic design Biconvex; posterior

aspheric opticBiconvex

Optic diameter (mm) 6.0 6.0Length (mm) 13.0 13.0Haptic material Same as optic

materialSame as optic

materialHaptic angulation (�) 0 0Ultraviolet filter Yes (blue-light filter) YesACD (mm) 5.37 5.2A constant 118.7 118.4

ACD Z anterior chamber depth

Figure 1. Edridge-Green lantern.

1599COLOR PERCEPTION AFTER BLUE LIGHT–FILTERTING AND UV-FILTERING IOLS

different color vision tests to establish eligibility for thejob. In India, the lantern test is used to establish eligi-bility for defense personnel and railway workers. Toour knowledge, there are no previous studies compar-ing color perception after implantation of a yellow-tinted IOL and a clear IOL using the lantern test. Wecompared a yellow-tinted IOL and a clear IOL usingthe lantern test and 3 other color vision tests.

PATIENTS AND METHODS

This prospective comparative study was performed atDr. Rajendra Prasad Centre for Ophthalmic Sciences,New Delhi, India. Inclusion criteria were senile cataract anda postoperative uncorrected distance visual acuity (UDVA)of 6/9 or better. Exclusion criteria were known hereditarycolor-vision defects, use of medication that might affect color

Figure 2.View from the eyepiece of the anomaloscope.A: Upper half of thared and lower half of sodium yellow. C: Endpoint of mixing the red and t

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vision (eg, ethambutol, antiepileptics, amiodarone, digitalis),a history of diabetes, ocular pathology other than cataract,and surgical complications (eg, posterior capsule rupture).

The eligible patients were divided into 2 groups. Onegroup received the Acrysof IQ SN60WF, which is a yellow-tinted IOL, and the other group received an AcrysofSA60AT, which is a clear IOL (both IOLs, Alcon Laborato-ries). Table 1 shows the characteristics of the IOLs.

Surgical Technique

The same surgeon (S.K.K.) performed all the cataract ex-tractions using a standard procedure under local or topicalanesthesia. The technique included a temporal clear cornealincision, phacoemulsification, and IOL implantation in thecapsular bag. All patients received moxifloxacin and pred-nisolone eyedrops for 4 weeks and tropicamide eyedropsfor 2 weeks postoperatively.

llium green and lower half of sodium yellow. B: Upper half of lithiumhe green lights.

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Table 2. Ranges for the anomaly quotient.

Diagnosis Anomaly Quotient Range

Normal 0.74, 1.40Deuteranomaly 1.70, 2.00Extreme deuteranomaly 1.00, NProtanomaly �0.60, 0.11Extreme protanomaly �1.00, 0.00

1600 COLOR PERCEPTION AFTER BLUE LIGHT–FILTERTING AND UV-FILTERING IOLS

Postoperative Evaluation

Patients were examined postoperatively at 1 month and 3months. Every visit included evaluation of the anterior andposterior segments, intraocular pressure (IOP), UDVA,corrected near visual acuity (CNVA), and color perception.Color perception was tested with the Ishihara pseudoiso-chromatic test, Edridge-Green lantern test, Heidelberganomaloscope, and Farnsworth-Munsell (FM) 100-hue test.

The 10th edition of the Ishihara pseudoisochromatic test,which consists of 38 plates, was used. The plates were held75 cm perpendicular to the patient’s line of sight under day-light illumination. Viewing time was 3 seconds per plate forall patients. If 17 or more of the first 21 plates were read cor-rectly, color sense was considered normal. If 13 or fewerplates were read correctly, the patient was considered tohave a red–green defect. Plate numbers 26 to 38 were usedwhen the patient was illiterate.13–16

The lantern test (Figure 1) was performed in a dark roomat 6 m. Sets of filters showing red, yellow, green, and bluewere shown, with each color being shown twice throughan aperture of 13.0mmand 1.3mm.9,16 A patient was consid-ered to have a color defect if he or she identified red as green;green as red; white as green or red or vice versa; or red,green, or white as black.

The Heidelberg anomaloscope test was administered in asemi-dark room.16,17 The anomaloscope consists of a white-

Figure 3. The FM100-hue test.A: Front of the colored caps.B: Back ofthe colored caps.

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light source that is split into its spectral colors by a prism. Itis designed to present a circular split field (Figure 2). In thelower half, a spectral yellow (sodium line) appears. The up-per half of the screen is filled with a mixture of spectral yel-low–green (thallium line) and spectral red (lithium line).The patient was asked to achieve a good color match be-tween the 2 halves of the field by adjusting the red andgreen. The anomaly quotient was then calculated. Table 2shows the ranges for the anomaly quotient. Anomalyquotients for normal trichromats, deuteranomaly, extremedeuteranomaly, protanomaly, extreme protanomaly, andprotanopia (very bright yellow around scale value 30) arematched to a green endpoint, and very dark yellow(around scale value 5) is matched to the red endpoint. Deu-teranopia (ie, both endpoints) is matched to a brightnessvalue around 15.

The FM 100-hue test consists of 85 movable caps arrangedin 4 panels (Figure 3). Each patient was instructed to arrangethe caps according to their color. Scoring was calculated foreach chip by adding the absolute value of the difference insequence number for each of the adjoining chips. A chipthat was properly placed between the 2 adjoining chips re-ceived a score of 2. A chip that was placed between 2 incor-rectly placed chips received a score higher than 2. Thesescores were plotted on a graph (Figure 4). The total errorscores were obtained by summing the error scores of allthe chips. A higher score indicates greater inaccuracy in plac-ing chips in the correct order. The diagnosis was based on thetotal error score calculated (Table 3) and the axis of confusioncentered on particular caps.9,16,18–20

Statistical Analysis

Statistical analysis was performed using SPSS software(version 15.0, SPSS, Inc.) The independent t test was usedto compare 2 means, the Mann-Whitney test was used tocompare nonparametric continuous data, and the Pearsonchi-square and Yates corrected chi-square tests were usedto compare nonparametric categorical data. A result wasconsidered statistically significant if the P value was lessthan 0.05 (95% confidence interval).

RESULTS

The study enrolled 100 eyes of 100 patients, with 50 ineach IOL group. 48 women and 52 men were equallydistributed between the 2 groups. Table 4 shows thepatients’ characteristics. There were no statisticallysignificant differences between the 2 groups in age,corrected distance visual acuity, or IOP. All patientshad a CNVA of N6.

Ishihara Plates

All patients in both groups were able to read at least17plates correctly. Therewasno statistically significantdifference between the 2 IOL groups 1 month and 3months postoperatively (PO.05, c2 test) (Table 5).

Anomaloscope

Table 6 shows the mean anomaly quotient 1 monthand 3 months postoperatively. There was no

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Figure 4. Graph plotting the error scoreson the FM-100 hue test.

1601COLOR PERCEPTION AFTER BLUE LIGHT–FILTERTING AND UV-FILTERING IOLS

statistically significant difference in the quotient be-tween the 2 IOL groups (PO.05).

Farnsworth-Munsell 100-Hue Test

Table 7 shows the between-group comparison ofcolor perception by the FM 100-hue test total errorscore. There were no statistically significant differ-ences between the 2 IOL groups 1 month or 3 monthspostoperatively.

No axis of confusion was noted on the polaritygraph in any patient in either group. Most patients inboth groups had average color discrimination(Figure 5). Three patients in the yellow-tinted groupand 4 patients in the clear group had superior colordiscrimination.

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Lantern Test

All patients in both groups were able to identify all 4colored lights correctly.

DISCUSSION

The theoretical benefits of a blue light–filtering IOLmust not be outweighed by potentially detrimental as-pects. There has been a debate since the introduction oflight–filtering IOLs on how much blue light theyshould filter.21,22 At present, there is no clinicalevidence that patients are at a disadvantage if theyreceive blue light–filtering IOLs.23

In our study, we did not find differences in colorperception with the blue light–filtering IOL. The colorvision test results were statistically comparable in bothgroups. Overall color perception results, described by

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Table 3. Total error score ranges.

Color Discrimination Total Error Score Range

Superior 0, 20Average 20, 100Low O100

Table 4. Between-group of age, UDVA, and IOP.

Parameter

Mean G SD

P ValueYellow-TintedIOL Group Clear IOL Group

Age (y) 60.88 G 6.32 61.0 G 6.81 .927UDVA (logMAR) 0.089 G 0.098 0.094 G 0.099 .788IOP (mm Hg) 13.28 G 1.97 14.04 G 2.08 .064

IOL Z intraocular lens; IOP Z intraocular pressure; UDVA Z uncor-rected distance visual acuity

1602 COLOR PERCEPTION AFTER BLUE LIGHT–FILTERTING AND UV-FILTERING IOLS

the total error scores on the FM 100-hue test, showedno significant differences between the yellow-tintedIOL group and the clear IOL group. This result agreeswith the findings of Rodríguez-Galietero,24 who usedthe FM 100-hue test to evaluate photopic color dis-crimination in eyes with a conventional blue light–fil-tering IOL and an IOL with UV filtering only. Theresults were similar to those in other studies.25–30

We also did not find a specific axis of confusion afterplotting the error scores on the polarity graph, indicat-ing that there was no change in color perception, evenin the blue region under standard testing conditions,similar to findings of Vuori and M€antyj€arvi.31 Aoet al.32 report similar results under photopic condi-tions. Under mesopic conditions, Ao et al. found statis-tically significant differences in partial error scores inthe green to blue–green band (color caps 36 to 46)and the blue–green to blue band (color caps 46 to 54);however, the mean total error scores were the sameunder mesopic conditions as well.

The lantern test is the most physiologic test andforms the basis of eligibility criteria for various profes-sions (eg, navy, air force, railways). In our study, therewas no difference in the perception of colored lightswith the yellow-tinted IOL. No study has taken thistest into account for comparing color perception withyellow-tinted IOLs.

The Ishihara plates are a good screening method toidentify color deficiency. However, they check onlyred and green deficiency and the expected differencein color perception with yellow-tinted IOLs, if any, isin the blue–yellow axis. In our study, there was no

Table 5. Comparison of color perception by Ishihara plates.

Plates ReadCorrectly (n)

Patients, n (%)

P Value*Yellow-TintedIOL Group Clear IOL Group

17 50 (100) 50 (100) d

18 49 (98) 50 (100) .47719 47 (94) 48 (96) 0.74520 43 (86) 45 (90) 0.38421 40 (80) 39 (78) 0.728

IOL Z intraocular lens*Chi-square test

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difference in results of the Ishihara plates betweenthe yellow-tinted IOL group and the clear IOL group.

Some studies show an association between cataractsurgery and AMD. Pollack et al.33 report that the rateof progression from dry to wet AMD was more than4 times greater in the first year after cataract surgeryin patients older than 65 years. The Beaver Dam EyeStudy34 reported an increased risk for progression ofAMD and the incidence of late AMD, defined as exu-dative macular degeneration or pure geographic atro-phy. Wang et al.35 pooled data from the Beaver Damand Blue Mountain Eye studies to obtain a combinedcohort of more than 6000 patients followed overa 5-year period and concluded that the 5-year riskfor developing late-stage AMD after cataract surgerywas 2 to 5 times greater in phakic subjects of similarage, sex, and smoking behavior. Although the reasonsfor these associations are not understood, the role ofexposure to short-wavelength or blue light has beengiven consideration.

Studies report that the incidence of photophobiaand cyanopsia was lower in patients with yellow-tinted IOLs than in those with clear IOLs. Yuanet al.36 suggest 2 reasons for the improved visual out-comes with yellow-tinted IOLs. First, according to theRayleigh law, the intensity of scatter radiation is

Table 6. Between-group comparison of color perception by theanomaloscope 1 month and 3 months postoeratively.

Follow-up andAnomaly Quotient

Mean G SD

P Value*Yellow-TintedIOL Group Clear IOL Group

1 monthAQ mininum 0.868 G 0.069 0.859 G 0.058 .494AQ maximum 1.192 G 0.075 1.177 G 0.075 .330

3 monthsAQ mininum 0.867 G 0.073 0.889 G 0.085 .172AQ maximum 1.215 G 0.086 1.212 G 0.106 .885

AQ Z anomaly quotient; IOL Z intraocular lens*Independent t test

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Table 7. Between-group comparison of color perception by theFM 100-hue test total error score.

Error Score

Mean G SD

P Value*Yellow-TintedIOL Group Clear IOL Group

1 month postop 52.3 G 21.5 52.94 G 19.58 .6173 months postop 50.42 G 20.94 53.38 G 18.89 .403

IOL Z intraocular lens*Mann-Whitney test

Figure 5. Comparison of color discrimination grades on FM 100-huetest (FM Z Farnsworth-Munsell; IOL Z intraocular lens).

1603COLOR PERCEPTION AFTER BLUE LIGHT–FILTERTING AND UV-FILTERING IOLS

inversely proportional to the fourth power of thewavelength.37 Hence, by blocking 400 to 500 nm lightin addition to UV light, the yellow-tinted IOLs limitscatter, thereby reducing glare and improving contrastsensitivity. Second, by blocking blue light, yellow-tinted lenses have been shown to improve reactiontime by strengthening the physiologic reaction of thephotoreceptors.38 Therefore, by reducing glare,yellow-tinted blue-filtering IOLs can increase contrastsensitivity and may decrease the risk for photophobiaand cyanopsia postoperatively.

In conclusion, given the possibility of increased risksfor AMD after cataract extraction and the possible ben-efits of implanting a short-wavelength filtering IOL,we suggest the benefits outweigh the minimum to in-significant effects the IOL may have on dark-adaptedspectral sensitivity and hue discrimination.

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First author:Sudarshan Kumar Khokhar, MD

Dr. Rajendra Prasad Centrefor Ophthalmic Sciences,All India Institute of Medical Sciences,Ansari Nagar, New Delhi, India