Quantification of Metamorphopsia in Patients with Epiretinal Membranes

Quantiﬁcation of Metamorphopsia in Patients with Epiretinal Membranes

Chota Matsumoto, Eiko Arimura, Sachiko Okuyama, Sonoko Takada, Shigeki Hashimoto, and Yoshikazu Shimomura

PURPOSE. To quantify the degree of metamorphopsia in patients In 1999, we developed a new metamorphopsia chart (M- with idiopathic epiretinal membranes (ERMs), by use of a new CHARTS; Inami) for evaluating the degree of metamorphop- metamorphopsia chart (M-CHARTS) developed by the authors. sia.9 In this study, we tried to quantify the degree of metamor- METHODS. These M-CHARTS had 19 dotted lines with dot inter- phopsia in patients with idiopathic epiretinal membrane (ERM) vals of between 0.2° (fine) and 2.0° (coarse) visual angles. As using this new metamorphopsia chart. the dot intervals were changed from fine to coarse, a decrease in the severity of metamorphopsia was noted. In this study, the minimum visual angle of the dotted lines needed to cause the METHODS metamorphopsia to disappear was measured in 51 eyes of 51 patients with ERM. The metamorphopsia scores were com- Subjects pared with the stages of ERM classified by scanning laser Forty-seven eyes of 47 normal subjects (29 women, mean age, 56.4 ophthalmoscope (SLO) images. years; range, 23–78) and 51 eyes of 51 patients with ERM (31 women, RESULTS. In patients with ERM, the metamorphopsia score mean age, 64.3 years; range, 44–80) were studied. Each subject un- increased depending on the severity of membrane proliferation derwent a complete ophthalmic examination, which included best classified by SLO images. The scores obtained from the hori- corrected visual acuity, slit lamp biomicroscopy, applanation tonome- zontal dotted lines were larger than those of the vertical lines try, dilated funduscopy, fundus photography and scanning laser oph- in advanced stages of ERM. thalmoscopy (SLO, Rodenstock). The inclusion criteria for normal CONCLUSIONS. M-CHARTS provide a very simple and useful subjects were as follows: corrected visual acuity of more than 1.0, method for evaluating the severity of metamorphopsia in pa- pupil diameter of more than 3.0 mm, intraocular pressure of less than tients with ERM. (Invest Ophthalmol Vis Sci. 2003;44: 21 mm Hg, no ocular and systemic diseases that were likely to affect 4012–4016) DOI:10.1167/iovs.03-0117 their visual functions. One randomly selected eye was examined. The inclusion criteria for ERM patients were as follows: corrected visual n cases of macula disease, metamorphopsia is one of the acuity of more than 0.1, pupil diameter of more than 3.0 mm, intraoc- Imost important symptoms for evaluating visual functions. ular pressure of less than 21 mm Hg, and no systemic diseases that Amsler charts are widely used for detecting metamorphop- were likely to affect their visual functions. If ERMs were observed in sia.1,2 However it is difficult to evaluate the degree of meta- both eyes, one randomly selected eye was examined. Informed con- morphopsia quantitatively using Amsler charts. Previous inves- sent was obtained from all normal subjects and ERM patients. All tigators have tried to evaluate the quantification of experiments were performed in accordance with the Declaration of metamorphopsia, micropsia, and macropsia.3–7 However, Helsinki for research involving human subjects. these methods used complicated procedures and could not be applied for clinical use. In 1989, we reported a method for Fundus Examination quantification of metamorphopsia using a computer display Dilated funduscopy, fundus photography and SLO images with an and our own program.8 In this method, two circles were argon blue laser beam were used for detection of ERMs. We classified shown on the fixation point and in the central 10° visual field, the severities of the membrane proliferation by SLO images and fundus respectively. The size of these circles was made to match using photographs according to the Nakajima’s classification: stage 1: water the computer mouse buttons to quantify the metamorphopsia. silk reflex and transparent membrane; stage 2, vascular tortuosity of Using this method, it was possible to quantify the metamor- mascular vessesl and transparent membrane; stage 3, opaque or dense phopsia in the cases of serious metamorphopsia. However, fine membranes.10 metamorphopsia near the fixation point was undetectable with this method. Quantification of Metamorphopsia In patients with metamorphopsia, a straight line projected onto the From the Department of Ophthalmology, Kinki University School retina is recognized as an irregular or curved line. When a dotted line of Medicine, Osaka, Japan. is used and the dot interval changes from fine to coarse, metamorphop- Supported by Grant 12671731 from the Ministry of Education of sia decreases and finally disappears. Figure 1 showed the simulation of the Japanese Government and the Osaka Medical Research Foundation the metamorphopsia on a straight line and two different kinds of for Incurable Diseases. dotted lines. Originally, these three lines were completely straight. The Submitted for publication February 4, 2003; revised March 16, same degrees of computer generated random distortion to the hori- 2003; accepted April 3, 2003. zontal direction were added to all three lines. In this simulation, it is Disclosure: C. Matsumoto (P); E. Arimura, None; S. Okuyama, clear that the dot interval changes from fine to coarse, the distortion of None; S. Takada, None; S. Hashimoto, None; Y. Shimomura, None lines decreases and finally disappears. Based on this phenomenon, we The publication costs of this article were defrayed in part by page charge payment. This article must therefore be marked “advertise- developed a new chart with 19 kinds of dotted lines with dot intervals ment” in accordance with 18 U.S.C. §1734 solely to indicate this fact. of between 0.2° to 2.0° visual angles (Fig. 2). The type (II) dotted line Corresponding author: Chota Matsumoto, Department of Ophthal- was designed for patients with central scotoma such as a macular hole. mology, Kinki University School of Medicine, Ohno-Higashi, Osaka- The minimum visual angle of the dotted line needed to cause the Sayama City, Osaka 589-8511, Japan; [email protected]. metamorphopsia to disappear was measured. At first, a vertical straight

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FIGURE 3. Method of detecting metamorphopsia using M-CHARTS. The minimum visual angle of the dotted lines needed to cause the metamorphopsia to disappear was measured.

RESULTS FIGURE 1. Simulation of metamorphopsia. Computer generated ran- The case was a 64-year-old woman with ERM in her right dom distortion to the horizontal direction were added to all three lines. As the dot interval was changed from fine to coarse, there was noted eye. Her right corrected vision was 0.4. Figure 4 shows an a decrease in the severity of metamorphopsia. SLO image of his right eye. The fine metamorphopsia was detected by Amsler charts of her right eye (Fig. 5). The metamorphopsia was also detected by the horizontal line on line (0°)onthefirst page of M-CHARTS is shown to patients, and the the M-CHARTS. However, the dot interval changed from patients fixated on a fixation point on the center of the line. If the “fine” to “coarse,” and there was a noted decrease in the patients recognized the straight line as straight, the metamorphopsia severity of metamorphopsia. When a dotted line of which score is 0. If the patients recognize the straight line as an irregular or the dot interval was a 0.6° visual angle was used, her meta- curved line, then the following pages of M-CHARTS that have the morphopsia completely disappeared (Fig. 6). Therefore, her metamorphopsia score with the horizontal line was deter- dotted lines where interval changes from fine to coarse are shown to mined to be 0.6. The vertical lines of the M-CHARTS was also the patients one after another (Fig. 3). When the patients recognized a tested in a similar way. The metamorphopsia score with the dot line as straight, its visual angle is considered as their metamorphop- vertical line was 0.4. sia score. Also, the M-CHARTS are rotated 90° and the same test is The intraindividual variation of the metamorphopsia score performed using horizontal lines. In this study, the examinations were was within one line (Ϯ0.1 score) in all subjects with ERM. The repeated three times for each subject to evaluate the reproducibility of metamorphopsia scores were 0 in all normal subjects. The the test. The patient’s fundus information was completely masked from sensitivity of this method for detecting metamorphopsia was the examiner during the examination. 97.3% and specificity was 100% using the result of the Amslar charts as a standard. The stages of the ERM patients were as follow; 12 eyes with stage 1 (mean age, 68.08 Ϯ 9.0 years), 13 eyes of stage 2 (mean age, 67.5 Ϯ 6.2 years) and 26 eyes of stage 3 (mean age, 61.0 Ϯ 7.5 years). Figure 7 shows the relationship

FIGURE 2. Design and examination conditions of M-CHARTS. The dot interval of the example dotted lines is 0.4. FIGURE 4. SLO image of ERM using argon blue laser beam.

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usually observed in early stages of ERM is detected by fine dotted lines; however, it is not detected by coarse dotted lines. In advance stages of ERM, the large amplitude and low frequency components of metamorphopsia increase, so it is easy to detect by all kinds of lines, including coarse dotted lines. In this study, we chose only a vertical line and a horizontal line which included a fixation point for quantifying the metamorphopsia. Metamorphopsia is commonly qualita- tively detected in the central 10° visual field using Amsler Charts. However, if we try to quantify the metamorphopsia on the peripheral line, it will be a very difficult task for patient and the results will be more inaccurate. Further- more, metamorphopsia is most remarkable around the fixation area, so we chose a vertical and horizontal center line for this method. There was no significant relationship between the metamorphopsia score and the visual acuity in our ERM patients. The metamorphopsia scores varied within the same visual acuity group. This suggests that the metamorphopsia score may show us new clinical information that is different from the visual acuity. In some patients, whose visual acuities were 0.1 or less, it was difficult to obtain metamorphopsia scores using the M-CHARTS because these patients could not recognize the dotted lines. It was also difficult to eval- FIGURE 5. The result of Amsler charts described by the patient. The fine metamorphopsia was detected in her right eye. uate metamorphopsia scores in some patients with a large central scotoma. Therefore, we excluded these low visual acuity subjects in this study. Further study is needed to between the metamorphopsia score and the stages of ERM. investigate the relationship between the degree of metamor- Metamorphopsia scores obtained from horizontal lines were phopsia and the visual acuity especially in the lower visual significantly large in subjects with stage 2 and stage 3 ERMs acuity patients. (stage 2: P Ͻ 0.05; stage 3: P Ͻ 0.002; Mann-Whitney test; The difference in the metamorphopsia between horizon- Fig. 7A). Metamorphopsia scores obtained from vertical tal lines and vertical lines has already been reported by lines were also significantly large in stage 3 ERM subjects Amsler in 1953.2 We also reported that there are similar (P Ͻ 0.02; Mann-Whitney test; Fig. 7B). Figure 8 shows the cases which have a difference in the metamorphopsia be- relationship between the metamorphopsia score of the hor- tween the horizontal and vertical lines.8 In this study, our izontal lines and that of the vertical lines in 3 stages of ERM results using the M-CHARTS clearly show that the metamor- patients. The horizontal axis shows the metamorphopsia phopsia scores obtained from the horizontal dotted lines score of horizontal lines. The vertical axis shows the meta- were larger than those of the vertical lines in advanced morphopsia score of the horizontal lines. The scores ob- stages of ERM. Increase in the severity of metamorphopsia tained from the horizontal dotted lines were significantly for horizontal lines means that the vertical contraction in- larger than those of the vertical lines in advanced stages of creases on the retina. One of the possible explanations of ERM (all stages: P Ͻ 0.003; stage 2: P Ͻ 0.05; stage 3: P Ͻ 0.005; Wilcoxon rank-sum test). The corrected vision of the subjects with ERM was as follows: 5 eyes were in the more than 0.1 to 0.2, 6 eyes were in the more than 0.2 to 0.4, 10 eyes were in the more than 0.4 to 0.6, 12 eyes were in the more than 0.6 to 0.8, 18 eyes were in the more than 0.8 to1.5. There was no significant relationship between the corrected vision and the metamorphopsia score in patients with ERM (Fig. 9).

DISCUSSION To evaluate the metamorphopsia using Amsler Charts, we have to ask to our patient carefully about their metamorphopsia and try to have them draw their image of distortion by themselves. However, this has been a difficult task for patients and also inaccurately quantified the degree of metamorphopsia. The advantage of the M-CHARTS is its simple task that the patients only have to answer if the line is distorted or not. Metamorphopsia is not a sim- FIGURE 6. The results of M-CHARTS. As the dot interval of ple symptom and it contains several kinds of compo- the M-CHARTS changed from fine to coarse, there was a noted nents. Especially, there are several kinds of frequency decrease in the severity of metamorphopsia. When a 0.6 dot- components of distortion in metamorphopsia. The fine ted line was used, the metamorphopsia completely disap- high frequency component of metamorphopsia which is peared.

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FIGURE 7. (A) The relationship between the metamorphopsia score for horizontal line and the stages of ERM. Metamorphopsia scores obtained from horizontal lines were signiﬁcantly large in subjects with stage 2 or 3 ERMs (stage 2: P Ͻ 0.05, stage 3: P Ͻ 0.002; Mann-Whitney test). (B) The relationship between the metamorphopsia score for the vertical line and the stages of ERM. Metamorphopsia scores obtained from vertical lines were signiﬁcantly large in stage 3 ERM subjects (P Ͻ 0.02; Mann-Whitney test).

this result is that the vertical contraction on the retina is We conclude that the M-CHARTS is a very simple and larger than horizontal contraction in ERM patients. The useful method for quantifying the severity of metamorphop- existence of the optic disc may resist the horizontal contrac- sia in patients with ERM. In addition, the M-CHARTS provide tion of the retina in advance stage of ERM. Another possible us more detailed information of metamorphopsia before and explanation of this result is the difference of human visual after macular surgery in patients with ERM or other macular sensitivities between horizontal and vertical visual ﬁelds. diseases such as a macula hole and age-related macula de- Some authors have reported that the ability of recognition is generation. more sensitive in horizontally than vertically in the human visual system.11,12

FIGURE 8. The relationship between the metamorphopsia score for the horizontal lines and that of the vertical lines in three stages of ERM FIGURE 9. The relationship between the metamorphopsia score patients. The scores obtained from the horizontal dotted lines were and the visual acuity in three stages of ERM patients. There was no significantly larger than those of the vertical lines in advanced stages of significant relationship between the corrected vision and the meta- ERM (all stages: P Ͻ 0.003, stage 2: P Ͻ 0.05, stage 3: P Ͻ 0.005; morphopsia score (P ϭ 0.15, Spearman’s rank correlation coeffi- Wilcoxon rank-sum test). cient).

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