Fog optometry refers to the use of optical lenses to make the parallel light incident on the tested eye, and the focus or focal line is transferred to the front of the retina, so as to alleviate the adjustment tension of the eye. In clinical practice, an excessive number of positive spherical lenses are generally added on the basis of the preliminary test results to make the tested eye in an artificial myopia state and force the tested eye to relax the adjustment, This kind of examination in the relaxed adjustment state of the examined eye is called fog optometry. The purpose is to relax the adjustment of the tested eye and reduce the error caused by adjustment factors in optometry.

Standard Operation Of Fog Optometry

a. Use objective Optometry (computer optometry or Optometry) to measure the basic diopter of the measured eye, and add a lens of this diopter in front of both eyes.

b. First check the right eye and cover the left eye with black accessory lens.

c. On the basis of the objective optometry results (most of the tested eyes can reach more than 0.8. If they cannot reach 0.8, add or subtract the degree of spherical lens to make the vision of the right eye reach about 0.8. At this time, the reaction of the tested eye is close to normal), and then add an excessive positive spherical lens (generally + 0.75D ~ + 2.00d) to make the eye fog vision, and the vision after fog vision decreases to 0.2 ~ 0.5.

d. At this time, due to the formation of artificial myopia in the right eye, the adjustment will be basically relaxed, and then the added spherical lens will be gradually reduced. In order to maintain the continuity of fog vision when replacing the lens, the principle of adding first and then reducing should be paid attention to until the best corrected visual acuity with the largest positive mirror is obtained. Myopia takes the lowest degree corresponding to the best vision, and hyperopia takes the highest degree corresponding to the best vision. Through fog vision examination, the data measured by myopia or hyperopia in the relaxed adjustment state can be more accurate (excluding the influence of astigmatism).

Visual Acuity Changes During Fog Vision In Different Refractive States

a. Mild hyperopia: with the decrease of the spherical lens, the visual acuity gradually improves. When the spherical lens is reduced to a certain extent, the visual acuity reaches normal and the best. At this time, the degree of the spherical lens can be further determined through the red and green visual standard inspection.

b. Pseudomyopia: the naked eye vision is about 0.8 or lower than the normal value. Add a negative spherical lens in front of your eyes to improve your vision to normal. For example, in the state of -0.50ds, your vision reaches 1.0. After fog vision, the visual acuity decreases, gradually reduces the degree of the added positive spherical lens, and gradually improves. When the added positive spherical lens decreases to 0 degree, the visual acuity reaches normal. If the negative spherical lens is added, the visual acuity does not improve, it is preliminarily judged that the tested eye is myopia caused by excessive adjustment. In this case, teenagers should be prompted to pay attention to myopia prevention and control and maintain normal reading distance, Appropriately increase outdoor activities, etc.

c. Hyperopia Astigmatism: in the process of fog vision examination, by reducing the positive spherical lens, you can achieve better vision, but can not reach the normal value, and then reduce the positive spherical lens. At this time, the vision will not improve. Take the positive spherical lens corresponding to the higher degree and put it in front of your eyes, and then use the red and green visual mark for further measurement, and then use the projection astigmatism meter to further check whether there is astigmatism. If it is found that the lines in one direction of the astigmatism meter are obviously clear and the other lines are relatively fuzzy, the "30 times rule" is used to determine the axis position of the added negative cylinder lens, and an appropriate negative cylinder lens is added until the lines in all directions of the observed astigmatism meter have the same clarity. Fog optometry again to determine the best corrected visual acuity with maximum orthography.

d. In practical optometry, the fog method can be indirectly applied to myopia and myopic astigmatism to reduce the error caused by adjustment factors. For example, we can first conduct objective optometry and correction on the tested eye, and then conduct fog optometry on the tested eye to obtain the best corrected vision in the fog state. Then the red and green visual standards are applied to further determine the degree of the spherical lens.

Note

a. The principle of fog vision method is to make the tested eye in the "artificial myopia state". Therefore, before fog vision optometry, apply objective optometry for preliminary examination and correction to make its vision above 0.8, and then add a spherical mirror to reduce its vision to 0.2 or 0.5. At this time, it must be in the "artificial myopia state".

b. Fog vision 0.2 and 0.5 have their own advantages and disadvantages: when fog vision 0.2, its advantage is that it can fully relax and adjust, but due to poor vision, the tested eye may give up cooperation or be insensitive; When the fog vision reaches 0.5, the examined eye will better and effectively cooperate with the subjective examination, but the adjustment may not be fully relaxed.

c. In the process of fog optometry, the principle of "adding before changing" must be followed, that is, add a new fog lens first, and then remove the original fog lens to avoid losing the fog effect at intervals. It is easy to operate when using a comprehensive optometer to change the fog lens.

d. Fog optometry should run through the whole refractive examination process, especially in the physical glasses store without mydriasis, fog optometry is particularly important.