two-color test

The two-color method test is a method for judging the degree of correction of the test lens when the lens is examined after the optometry. Cover your eyes. The right eye and the left eye are sequentially performed. Let it look at the red and green bi-color optotypes, look at the green optotype first, then look at the red, then look at the green, ask which visual target is clearer or as clear as the two visual targets. Basic Information Specialist Category: Ophthalmic Examination Category: Applicable gender: whether men and women apply fasting: not fasting Tips: Maintain a normal diet and schedule. Normal value Due to the different wavelengths of light, various color sensations can be produced. White light, such as daylight, can be dissipated into seven different colors of light after passing through the lens. This phenomenon is called "dispersion." This shows that the white light is a mixture of seven different shades of light. Different colors of light travel in the same speed in vacuum, but the speed is different when entering a dense medium. The red light has a long wavelength, a small refractive index, and the fastest speed; while the purple light has a short wavelength, a large refractive index, and the slowest speed, so it is respectively focused on different points on the optical axis, the red light focus is the farthest, and the blue light focus is the closest. The positional difference of imaging on the axis is called axial chromatic aberration. Clinical significance Abnormal results: There are also coloring aberrations in the human eye refractive system. The chromatic aberration when facing the eye is such that the yellow light focus falls on the retina, the green light focus is in front of the retina, and the red light focus is behind the retina. In myopia, the axial length is long, and the yellow light focus falls in front of the retina; in the hyperopic, the axial length is short, and the yellow focus falls behind the retina. Patients who need to be examined for myopia or hyperopia. Precautions Contraindications before inspection: Illumination is at least 200lx and remains constant. Requirements for inspection: cover one eye. The right eye and the left eye are sequentially performed. Inspection process 1. Let the patient wear a test lens that is corrected to the best vision. 2. Cover your eyes. The right eye and the left eye are sequentially performed. 3. Let them look at the red and green bi-color optotypes, first look at the green optotype, then look at the red, then look at the green, ask which visual target is clearer or as clear as the two visual targets. 4. If the red visual target is clear, add a -0.25D concave spherical lens, or remove the +0.25D convex spherical lens; if the green visual standard is clear, remove the -0.25D concave spherical lens or add +0.25 The convex spherical lens of D is gradually increased or decreased with a gradient of 0.25D until the red-green visual target looks equally clear. 5. If there is no red and green bi-color optotype, it can also be replaced by red and green filters. The method of judging and fine-tuning the spherical mirror is the same as above. Not suitable for the crowd Inappropriate people: patients with abnormal color vision should be used with caution.