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Color vision after laser in situ keratomileusis
Color vision after laser in situ keratomileusis Yi-Yu Tsai, MD, Jane-Ming Lin, MD ABSTRACT Purpose: To evaluate the effect of laser in situ keratomileusis (LASIK) on color vision. Setting: Department of Ophthalmology, China Medical College Hospital, Taichung, Taiwan. Method: This prospective study comprised consecutive patients having LASIK. Patients were eligible for inclusion if they had a best corrected visual acuity of 20/20 or better and a normal color vision test preoperatively and an uncorrected near visual acuity of 20/40 or better postoperatively. Color vision was tested using the Farnsworth-Munsell 100hue test (FM 100 test) preoperatively and 1 day, 1 week, and 1 month postoperatively. Results: Twenty-nine eyes of 15 patients having LASIK were enrolled in the study. The mean patient age was 29.2 years ⫾ 2.9 (SD). The mean preoperative spherical equivalent refractive error was ⫺5.6 ⫾ 1.8 diopters, and the mean preoperative error score of the FM 100 test was 3.79 ⫾ 1.55. After surgery, no significant change in the error score was observed at 1 day (4.30 ⫾ 1.07, P ⫽ .1039, paired t test), 1 week (3.72 ⫾ 1.25, P ⫽ .8125, paired t test), or 1 month (3.97 ⫾ 1.29, P ⫽ .6149, paired t test). Conclusion: Laser in situ keratomileusis did not affect color vision evaluated by the FM 100 test. J Cataract Refract Surg 2001; 27:697– 699 © 2001 ASCRS and ESCRS
L
aser in situ keratomileusis (LASIK) is widely used to correct myopia, and several studies have reported good efficacy and predictability after LASIK.1–3 In most series, visual acuity is the sole measure by which postLASIK vision function is assessed. Visual acuity is a measure of visual performance under optimal conditions— high contrast and high luminance. Only a few visual targets in the daily environment have such parameters. The visual world is composed of targets that vary along many dimensions: spatial frequency, contrast, temporal frequency, spatial location, and color.4 Viewing conditions also vary in luminance, as well as in the presence of glare and fog.4 Accepted for publication January 10, 2001. Reprint requests to Yi-Yu Tsai, MD, Department of Ophthalmology, National Cheng-Kung University Hospital, 138, Sheng Li Road, Tainan, Taiwan. © 2001 ASCRS and ESCRS Published by Elsevier Science Inc.
Hence, measuring only visual acuity to evaluate vision functions is insufficient. Functions other than visual acuity are being evaluated after LASIK. Reduced contrast sensitivity, halo, and glare have been noted5– 8; however, the effect of LASIK on color vision has not been evaluated. In this study, we attempted to evaluate the effect of LASIK on color vision.
Patients and Methods Consecutive patients having LASIK by the same surgeon (Y.Y.T.) in October 1999 were enrolled in this prospective study. All patients had LASIK at our hospital and were 20 years or older. They had visual acuity correctable to 20/40 or better, normal videokeratography, a normal anterior segment by slitlamp microscopy, and a normal posterior pole by dilated fundoscopy. 0886-3350/01/$–see front matter PII S0886-3350(01)00771-4
COLOR VISION AFTER LASIK
They did not have glaucoma or ocular hypertension or systemic collagen vascular disease and were not pregnant or using systemic corticosteroids. Patients were eligible for inclusion in the study if they were not using a systemic or topical drug and had a best corrected visual acuity (BCVA) of 20/20 or better and a normal color vision test preoperatively and an uncorrected near visual acuity of 20/40 or better postoperatively. All LASIK procedures were performed using the Schwind excimer laser (Keratom Multiscan) and the Moria LSK-One manual microkeratome with a 130 m ablation plate. Topical fluorometholone 0.1% (FML威) and ciprofloxacin 0.3% (Ciloxan威) were instilled 4 times daily during the first postoperative week, and fluorometholone 0.1% (FML威) was instilled 3 times a day during the second week. Color vision was tested using the Farnsworth-Munsell 100-hue test (FM 100 test) preoperatively and 1 day, 1 week, and 1 month postoperatively. The test was performed with spectacle correction preoperatively and without refractive correction postoperatively. The error scores in the FM 100 test were calculated as square roots as proposed by Kinnear.9 The mean and standard deviation of the error scores were calculated, and the paired Student t test was used for statistical analysis. In this study, normal color vision was defined as an error score of less than 7.5, as proposed by Fong and coauthors.10
Results The study comprised 29 eyes of 15 patients (6 men, 9 women). The mean patient age was 29.2 years ⫾ 2.9 (SD) (range 23 to 34 years). The mean preoperative spherical equivalent refractive error was ⫺5.6 ⫾ 1.8 diopters (D) (range ⫺2.75 to –10.00 D). The mean preoperative error score on the FM 100 test in all 29 eyes was 3.79 ⫾ 1.55. After surgery, no significant change in the error score was observed at 1 day (4.30 ⫾ 1.07, P ⫽ .1039, paired t test), 1 week (3.72 ⫾ 1.25, P ⫽ .8125, paired t test), or 1 month (3.97 ⫾ 1.29, P ⫽ .6149, paired t test).
Discussion Visual performance after LASIK is commonly evaluated by uncorrected visual acuity (UCVA), 698
BCVA, and the number of Snellen acuity lines gained or lost.1–3 However, when patients report their satisfaction with LASIK, they are considering the quality of their vision, not just the Snellen acuity measured in the office. Good visual quality means, among other things, sufficient visual field and resolution of space, brightness, and color to meet patients’ visual needs.11 After LASIK, UCVA is usually improved1–3 and contrast sensitivity is reduced temporarily6,7 or longer than 6 months8; color vision has not been studied. Using the FM 100 test, this study assessed the effect of LASIK on color vision. It found no statistically significant difference between preoperative measurements and postoperative measurements at 1 day, 1 week, and 1 month. To our knowledge, this is the first study to evaluate color vision after LASIK. There is 1 published report of color vision after refractive surgery. McDonald and coauthors12 examined 16 patients who had radial keratotomy and detected no defects in color vision in any patient. There are reports of the deviation effect of LASIK on ophthalmic measurements, such as intraocular pressure measurements by conventional methods13 and retinal nerve fiber layer thickness measurements by scanning laser polarimetry.14 Based on our study, LASIK has no such effect on the FM 100 test, so a color vision test is still valuable in evaluating many retinal and optic nerve diseases after LASIK, such as optic neuritis, drug-induced retinopathy,15 glaucoma,16 and diabetic retinopathy.10 In summary, our results showed that LASIK did not affect color vision evaluated by the FM 100 test and that the FM 100 test was still usable after LASIK.
References 1. Carr JD, Stulting RD, Sano Y, et al. Prospective comparison of single-zone and multizone laser in situ keratomileusis for the correction of low myopia. Ophthalmology 1998; 105:1504 –1511 2. Salah T, Waring GO III, el Maghraby A, et al. Excimer laser in situ keratomileusis under a corneal flap for myopia of 2 to 20 diopters. Am J Ophthalmol 1996; 121: 143–155 3. Pallikaris IG, Siganos DS. Laser in situ keratomileusis to treat myopia: early experience. J Cataract Refract Surg 1997; 23:39 – 49 4. Haegerstrom-Portnoy G, Schneck ME, Brabyn JA. See-
J CATARACT REFRACT SURG—VOL 27, MAY 2001
COLOR VISION AFTER LASIK
5.
6.
7.
8.
9. 10.
11.
ing into old age: vision function beyond acuity. Optom Vis Sci 1999; 76:141–158 Pop M, Payette Y. Photorefractive keratectomy versus laser in situ keratomileusis; a control-matched study. Ophthalmology 2000; 107:251–257 Pe´rez-Santonja JJ, Sakla HF, Alio´ JL. Contrast sensitivity after laser in situ keratomileusis. J Cataract Refract Surg 1998; 24:183–189 Mutyala S, McDonald MB, Scheinblum KA, et al. Contrast sensitivity evaluation after laser in situ keratomileusis. Ophthalmology 2000; 107:1864 –1867 Holladay JT, Dudeja DR, Chang J. Functional vision and corneal changes after laser in situ keratomileusis determined by contrast sensitivity, glare testing, and corneal topography. J Cataract Refract Surg 1999; 25:663– 669 Kinnear PR. Proposals for scoring and assessing the 100hue test. Vis Res 1970; 10:423– 433 Fong DS, Barton FB, Bresnick GH. Impaired color vision associated with diabetic retinopathy: Early Treatment Diabetic Retinopathy Study Report no.15. Am J Ophthalmol 1999; 128:612– 617 Lawless MA. Refining visual quality assessment in refractive surgery (editorial). J Cataract Refract Surg 1999; 25: 1031–1032
12. McDonald MB, Haik M, Kaufman HE. Color vision and contrast sensitivity testing after radial keratotomy. Am J Ophthalmol 1987; 103:468 13. Emara B, Probst LE, Tingey DP, et al. Correlation of intraocular pressure and central corneal thickness in normal myopic eyes and after laser in situ keratomileusis. J Cataract Refract Surg 1998; 24:1320 –1325 ¨ zden R, Pons ME, Barbieri C, et al. Scanning 14. Gu¨rses-O laser polarimetry measurements after laser-assisted in situ keratomileusis. Am J Ophthalmol 2000; 129:461– 464 15. Bayer AU, Thiel HJ, Zrenner E, et al. Color vision tests for early detection of antiepileptic drug toxicity. Neurology 1997; 48:1394 –1397 16. Pacheco-Cutillas M, Sahraie A, Edgar DF. Acquired colour vision defects in glaucoma—their detection and clinical significance. Br J Ophthalmol 1999; 83:1396 – 1402 From the Departments of Ophthalmology, China Medical College Hospital, Taichung (Tsai, Lin), and National Cheng-Kung University Hospital, Tainan (Tsai), Taiwan. Neither author has a proprietary or financial interest in any product mentioned.
J CATARACT REFRACT SURG—VOL 27, MAY 2001
699
L
aser in situ keratomileusis (LASIK) is widely used to correct myopia, and several studies have reported good efficacy and predictability after LASIK.1–3 In most series, visual acuity is the sole measure by which postLASIK vision function is assessed. Visual acuity is a measure of visual performance under optimal conditions— high contrast and high luminance. Only a few visual targets in the daily environment have such parameters. The visual world is composed of targets that vary along many dimensions: spatial frequency, contrast, temporal frequency, spatial location, and color.4 Viewing conditions also vary in luminance, as well as in the presence of glare and fog.4 Accepted for publication January 10, 2001. Reprint requests to Yi-Yu Tsai, MD, Department of Ophthalmology, National Cheng-Kung University Hospital, 138, Sheng Li Road, Tainan, Taiwan. © 2001 ASCRS and ESCRS Published by Elsevier Science Inc.
Hence, measuring only visual acuity to evaluate vision functions is insufficient. Functions other than visual acuity are being evaluated after LASIK. Reduced contrast sensitivity, halo, and glare have been noted5– 8; however, the effect of LASIK on color vision has not been evaluated. In this study, we attempted to evaluate the effect of LASIK on color vision.
Patients and Methods Consecutive patients having LASIK by the same surgeon (Y.Y.T.) in October 1999 were enrolled in this prospective study. All patients had LASIK at our hospital and were 20 years or older. They had visual acuity correctable to 20/40 or better, normal videokeratography, a normal anterior segment by slitlamp microscopy, and a normal posterior pole by dilated fundoscopy. 0886-3350/01/$–see front matter PII S0886-3350(01)00771-4
COLOR VISION AFTER LASIK
They did not have glaucoma or ocular hypertension or systemic collagen vascular disease and were not pregnant or using systemic corticosteroids. Patients were eligible for inclusion in the study if they were not using a systemic or topical drug and had a best corrected visual acuity (BCVA) of 20/20 or better and a normal color vision test preoperatively and an uncorrected near visual acuity of 20/40 or better postoperatively. All LASIK procedures were performed using the Schwind excimer laser (Keratom Multiscan) and the Moria LSK-One manual microkeratome with a 130 m ablation plate. Topical fluorometholone 0.1% (FML威) and ciprofloxacin 0.3% (Ciloxan威) were instilled 4 times daily during the first postoperative week, and fluorometholone 0.1% (FML威) was instilled 3 times a day during the second week. Color vision was tested using the Farnsworth-Munsell 100-hue test (FM 100 test) preoperatively and 1 day, 1 week, and 1 month postoperatively. The test was performed with spectacle correction preoperatively and without refractive correction postoperatively. The error scores in the FM 100 test were calculated as square roots as proposed by Kinnear.9 The mean and standard deviation of the error scores were calculated, and the paired Student t test was used for statistical analysis. In this study, normal color vision was defined as an error score of less than 7.5, as proposed by Fong and coauthors.10
Results The study comprised 29 eyes of 15 patients (6 men, 9 women). The mean patient age was 29.2 years ⫾ 2.9 (SD) (range 23 to 34 years). The mean preoperative spherical equivalent refractive error was ⫺5.6 ⫾ 1.8 diopters (D) (range ⫺2.75 to –10.00 D). The mean preoperative error score on the FM 100 test in all 29 eyes was 3.79 ⫾ 1.55. After surgery, no significant change in the error score was observed at 1 day (4.30 ⫾ 1.07, P ⫽ .1039, paired t test), 1 week (3.72 ⫾ 1.25, P ⫽ .8125, paired t test), or 1 month (3.97 ⫾ 1.29, P ⫽ .6149, paired t test).
Discussion Visual performance after LASIK is commonly evaluated by uncorrected visual acuity (UCVA), 698
BCVA, and the number of Snellen acuity lines gained or lost.1–3 However, when patients report their satisfaction with LASIK, they are considering the quality of their vision, not just the Snellen acuity measured in the office. Good visual quality means, among other things, sufficient visual field and resolution of space, brightness, and color to meet patients’ visual needs.11 After LASIK, UCVA is usually improved1–3 and contrast sensitivity is reduced temporarily6,7 or longer than 6 months8; color vision has not been studied. Using the FM 100 test, this study assessed the effect of LASIK on color vision. It found no statistically significant difference between preoperative measurements and postoperative measurements at 1 day, 1 week, and 1 month. To our knowledge, this is the first study to evaluate color vision after LASIK. There is 1 published report of color vision after refractive surgery. McDonald and coauthors12 examined 16 patients who had radial keratotomy and detected no defects in color vision in any patient. There are reports of the deviation effect of LASIK on ophthalmic measurements, such as intraocular pressure measurements by conventional methods13 and retinal nerve fiber layer thickness measurements by scanning laser polarimetry.14 Based on our study, LASIK has no such effect on the FM 100 test, so a color vision test is still valuable in evaluating many retinal and optic nerve diseases after LASIK, such as optic neuritis, drug-induced retinopathy,15 glaucoma,16 and diabetic retinopathy.10 In summary, our results showed that LASIK did not affect color vision evaluated by the FM 100 test and that the FM 100 test was still usable after LASIK.
References 1. Carr JD, Stulting RD, Sano Y, et al. Prospective comparison of single-zone and multizone laser in situ keratomileusis for the correction of low myopia. Ophthalmology 1998; 105:1504 –1511 2. Salah T, Waring GO III, el Maghraby A, et al. Excimer laser in situ keratomileusis under a corneal flap for myopia of 2 to 20 diopters. Am J Ophthalmol 1996; 121: 143–155 3. Pallikaris IG, Siganos DS. Laser in situ keratomileusis to treat myopia: early experience. J Cataract Refract Surg 1997; 23:39 – 49 4. Haegerstrom-Portnoy G, Schneck ME, Brabyn JA. See-
J CATARACT REFRACT SURG—VOL 27, MAY 2001
COLOR VISION AFTER LASIK
5.
6.
7.
8.
9. 10.
11.
ing into old age: vision function beyond acuity. Optom Vis Sci 1999; 76:141–158 Pop M, Payette Y. Photorefractive keratectomy versus laser in situ keratomileusis; a control-matched study. Ophthalmology 2000; 107:251–257 Pe´rez-Santonja JJ, Sakla HF, Alio´ JL. Contrast sensitivity after laser in situ keratomileusis. J Cataract Refract Surg 1998; 24:183–189 Mutyala S, McDonald MB, Scheinblum KA, et al. Contrast sensitivity evaluation after laser in situ keratomileusis. Ophthalmology 2000; 107:1864 –1867 Holladay JT, Dudeja DR, Chang J. Functional vision and corneal changes after laser in situ keratomileusis determined by contrast sensitivity, glare testing, and corneal topography. J Cataract Refract Surg 1999; 25:663– 669 Kinnear PR. Proposals for scoring and assessing the 100hue test. Vis Res 1970; 10:423– 433 Fong DS, Barton FB, Bresnick GH. Impaired color vision associated with diabetic retinopathy: Early Treatment Diabetic Retinopathy Study Report no.15. Am J Ophthalmol 1999; 128:612– 617 Lawless MA. Refining visual quality assessment in refractive surgery (editorial). J Cataract Refract Surg 1999; 25: 1031–1032
12. McDonald MB, Haik M, Kaufman HE. Color vision and contrast sensitivity testing after radial keratotomy. Am J Ophthalmol 1987; 103:468 13. Emara B, Probst LE, Tingey DP, et al. Correlation of intraocular pressure and central corneal thickness in normal myopic eyes and after laser in situ keratomileusis. J Cataract Refract Surg 1998; 24:1320 –1325 ¨ zden R, Pons ME, Barbieri C, et al. Scanning 14. Gu¨rses-O laser polarimetry measurements after laser-assisted in situ keratomileusis. Am J Ophthalmol 2000; 129:461– 464 15. Bayer AU, Thiel HJ, Zrenner E, et al. Color vision tests for early detection of antiepileptic drug toxicity. Neurology 1997; 48:1394 –1397 16. Pacheco-Cutillas M, Sahraie A, Edgar DF. Acquired colour vision defects in glaucoma—their detection and clinical significance. Br J Ophthalmol 1999; 83:1396 – 1402 From the Departments of Ophthalmology, China Medical College Hospital, Taichung (Tsai, Lin), and National Cheng-Kung University Hospital, Tainan (Tsai), Taiwan. Neither author has a proprietary or financial interest in any product mentioned.
J CATARACT REFRACT SURG—VOL 27, MAY 2001
699