Why can't I hear people clearly when I take off my glasses?

People with myopia often feel that after taking off their glasses, they can not only not see things clearly, but also cannot hear others talking clearly. What is the reason for this?

01How do people see objects and hear sounds?

How do we see objects? The light emitted by objects in the external environment is refracted by the refractive system of the eyeball and then formed on the retina. It is then transmitted to the visual cortex of the brain through the optic nerve and finally analyzed and processed by the visual center so that we can "see" the object.

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How do we hear sound? The vibration of an object generates sound waves, which are collected by the auricle and enter the external auditory canal, causing the eardrum to vibrate. The eardrum is connected to three small bones (the malleus, incus, and stapes). These bones are called the ossicular chain, which amplifies the vibration of the eardrum and transmits it to the inner ear, causing the fluid in the cochlea in the inner ear to vibrate. The cochlea is a spiral tube with thousands of hair cells inside. When the hair cells are stimulated, they convert mechanical vibrations into electrical signals. The electrical signals are transmitted to the brain through the auditory nerve, which processes and interprets them, and eventually the sound can be "heard".

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Among all human sensory organs, 85% of information is obtained through vision, and 10% through hearing. The visual and auditory functions are closely related to many brain functions. In the course of human evolution, vision and hearing functions have always interacted to meet human survival and living needs.

02Why do myopic people feel their hearing deteriorates after taking off their glasses?

From a neurobiological perspective, this is because there is cross-modal and cross-modal interaction between vision and hearing. When the input of visual information is reduced or blocked, the brain's ability to process auditory information will be reduced , resulting in the feeling of "hearing loss".

From a psychological perspective, this phenomenon may be related to audiovisual integration. When humans perceive external information, the brain usually integrates the visual and auditory information received ("McGurk effect"). In 1976, Harry McGurk and John MacDonald first reported this effect: the person in the video made the syllable "ga" mouth shape, but at the same time played the audio of the syllable "ba", and the viewer felt that he heard the pronunciation of "da".

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This interesting phenomenon is because the brain integrates the information heard and seen , that is, audio-visual integration. After taking off their glasses, myopic people cannot clearly judge the other person's lip shape, which affects the accuracy of the voice they hear. In addition, due to blurred vision, they cannot clearly obtain the other person's micro-expressions, gestures, body language and other visual information. They only obtain external information through their ears, which causes hearing loss.

On the contrary, the visually impaired (blind) cannot input normal visual signals during the process of visual formation, but they have sensitive hearing and touch. Because the central nervous system of the visually impaired has undergone a series of plastic changes, the brain reconfigures the information originally used for visual perception to other sensory systems for processing , constructing a new way of perception. The neural connections projected to the visual cortex of the brain gradually form new specific sensory circuits, driving the visual cortex of the brain to process information from other non-visual channels (touch and hearing, etc.), thereby achieving cross-channel reorganization. Auditory advantage compensation can help the visually impaired better adapt to the complex and changing environment of the outside world. For example, the blind can use hearing to identify directions and use touch to read Braille.

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03Diseases that affect both vision and hearing

Both vision and hearing play a vital role in our acquisition of information and perception of the outside world, but some diseases can affect both human vision and hearing functions.

Stickler syndrome , also known as hereditary progressive arthrophthalmopathy, is an inherited connective tissue disease characterized by defects of the eyes, bones, oral and facial areas, and hearing. The prevalence in newborns is 1/7500 to 1/9000, which can lead to serious vision, hearing, and joint problems. The appearance of eye features such as high myopia, retinal detachment, cataracts at a young age, as well as the special facial features of a flat midface and short nose are the main basis for early diagnosis. It is recommended to conduct genetic testing as early as possible to confirm the diagnosis and typing. Due to the varying degrees of hearing loss, which is diverse and progressive, most children first visit the ophthalmology department and often ignore hearing problems. Therefore, it is very necessary for patients to undergo regular audiological diagnostic evaluations.

Van der Hoeve syndrome , also known as deafness-blue sclera-brittle bone syndrome, has an incidence rate of about 0.04% in the Chinese population and is characterized by a triad of blue sclera, multiple fractures, and conductive hearing loss. 50% of patients experience hearing loss in both ears around the age of 20, and may further develop accompanying symptoms such as tinnitus and dizziness around the age of 60; eye symptoms manifest as blue or gray sclera. At the same time, patients with osteogenesis imperfecta are more susceptible to eye diseases such as glaucoma and cataracts. There is no effective drug treatment for this disease. Depending on the type and degree of hearing loss, stapes surgery, hearing aids, or cochlear implants can be used to improve hearing.

Image source: Reference [5]

References

[1] Shang Yingmei. Study on auditory inhibition of return based on position and frequency for visually impaired people[D]. Northeast Normal University, 2006.

[2] Xu Zhenhui. Study on the impact of visual and auditory interaction on patients' negative emotions[D]. Donghua University, 2017.

[3] Feng Jie, Xu Juan, Wu Xinchun. The impact of visual experience loss on auditory word recognition in the blind[J]. Advances in Psychological Science, 2021, 29(12): 2131-2146.

[4] Liu Liyang, Yang Quyang, Wang Sufang, et al. A case of Stickler syndrome with hearing impairment[J]. Chinese Journal of Otolaryngology, 2023, 21(06): 925-928.

[5] Yuan Yongyi, Dai Pu. Van der Hoeve syndrome[J]. Journal of Clinical Otorhinolaryngology Head and Neck Surgery, 2018, 32(16): 1222-1225. DOI: 10.13201/j.issn.1001-1781.2018.16.004.

Author: Zheng Xiaohong, PhD candidate in biology and medicine, master of optometry, chief ophthalmologist at the optometry center of the Affiliated Eye, Ear, Nose and Throat Hospital of Fudan University; Zheng Ke, deputy director of the education department of the Affiliated Eye, Ear, Nose and Throat Hospital of Fudan University, associate chief physician

Planning: Little Dandelion

Editor: rain

Title image source: Photo Network