HOMESurgical InstrumentsINNOVATIONSKDM-1 M-CHARTS TM Quantitatable metamorphopsia chart
A new metamorphopsia chart for quantifying metamorphopsia
M-CHARTS™ is a new metamorphopsia chart for quantifying metamorphopsia.
In patients with metamorphopsia, a straight line projected onto the retina is recognized as an irregular or curved line. When a dotted line is used and the dot interval changes from fine to coarse, metamorphopsia decreases and finally disappears.
Based on this phenomenon, we developed a new chart with 19 kinds of horizontal and vertical dotted lines with the dot interval between 0.2 degrees to 2.0 degrees visual angles. The minimum visual angle of the dotted line needed to detect metamorphopsia is then measured. We applied this method to patients with metamorphopsia due to epiretinal membrane, macular holes, central serous retinopathy and age-related macular degeneration. The thus obtained metamorphopsia score increased along with the severity of metamorphopsia.
This method is easy to use and promises to be of value in determining the severity of metamorphopsia in macular lesions.
The charts are designed to be used at a distance of 30cms.
The refraction of the eye in question must be exactly corrected for this distance.
The chart must be clearly and evenly lit as for a reading test.
All artificial mydriasis and any ophthalmoscopy immediately before examination should be avoided.
Before examination, occlude patient's non-tested eye with an eye patch.
At first, a vertical straight line (0 degree) on the first page of M-CHARTS™ is shown to a patient, and the patient fixates a fixation point on the center of the line. If the patient recognizes the straight line as straight, the metamorphopsia score is 0. If the patient recognizes the straight line as an irregular or curved line, then the following pages of M-CHARTS™, which have the dotted lines where interval changes from fine to coarse, are shown to the patient one after the other.
When the patient recognizes the dotted line as straight, its visual angle is considered as his or her metamorphopsia score.
Secondly, M-CHARTS™ is rotated 90 degrees and the same test is carried out using horizontal lines.
The metamorphopsia scores in both vertical and horizontal directions are recorded respectively.
E.G. MV=0.4, MH=0.8
(MV: metamorphopsia score of vertical lines, MH: metamorphopsia score of horizontal lines)
If the patient has small central scotoma such as macular hole, two-line type (Type II) is used. If the patient is not able to fixate the central fixation point, two guiding optotypes beside two lines are used. In this case it has to be explained to the patient that he or she should fixate at the center of the two guiding optotypes during the examination.
It is difficult to obtain metamorphopsia scores from those patients with visual acuities 20/100 or less. It is also difficult to evaluate metamorphopsia score in those patients with large central scotoma.
Patent No.
Europe: 1084673 (10/03/2004)
U.S.A.: 6,585,376B1 (1/7/2003)
Japan: 3320060 (21/06/2002)
Name:Chota Matsumoto, M.D.,D.Sc.
Eiko Arimura, M.D.,D.Sc.
AFFILIATIONS:
Department of Ophthalmology
Kinki University School of Medicine
REFERENCES:
1. Matsumoto C, Arimura E, Hashimoto S, Takada S, Okuyama S, Shimomura Y.
Quantification of metamorphopsia in patients with epiretinal membranes. Invest Ophothalmol Vis Sci. 2003;44:4012-4016.
2. Arimura E, Matsumoto C, Okuyama S, Takada S, Hashimoto S, Shimomura Y.
Retinal contraction and metamorphopsia scores in eyes with idiopathic epiretinal membrane. Invest Ophothalmol Vis Sci. 2005;46:2961-2966.
3. Arimura E, Matsumoto C, Okuyama S, Takada S, Hashimoto S, Shimomura Y.
Quantification of metamorphopsia in a macular hole patient using M-CHARTSTM. Acta Ophthalmol Scand. 2007;85:55-59.
