Though most of us might not consciously think about it, our hearing and our vision constantly are working in concert to help us communicate and navigate the world around us.
Hearing and the auditory system
Our auditory system is responsible for our hearing and can be divided into two main sections: the peripheral auditory system and the central auditory system. The peripheral auditory system consists of the outer ear, the middle ear and the cochlea (inner ear). The outer ear includes the external ear (pinna), the ear canal and the eardrum, also known as the tympanic membrane. Sound waves travel through the ear canal, striking the eardrum and causing it to move or vibrate.
The middle ear is the space behind the eardrum that contains the three smallest bones in the human body. This chain of tiny bones is connected to the eardrum at one end and to an opening to the inner ear at the other end. Vibrations from the eardrum cause the bones to move, sending the sound waves to the inner ear.
The inner ear is a fluid-filled structure called the cochlea which contains hair cells. Vibrations passed into the inner ear cause fluid movement, which then stimulates these tiny hair cells. The hair cells generate an electrical signal, which is passed along the auditory nerve into a region of the brain called the auditory cortex. The auditory cortex assigns meaning to the sound.
Approximately 95% of hearing loss in the adult population is sensorineural in nature. In this type of hearing loss, the problem is due to damage to or degeneration of the inner ear (sensory) or auditory nerve (neural). The most common causes of sensorineural hearing loss are noise exposure, age, and hereditary predisposition. Other causes include drugs toxic to the auditory system, viral illness, disturbance of inner ear fluids, and invasion of the inner ear by excessive temporal bone growth.
In about 5% of individuals, hearing loss in the adult population is conductive in nature. In this type of hearing loss, the problem is due to mechanical or structural damage to the outer and/or middle ear, resulting in reduced sound transmission to the inner ear. Common causes are impacted wax, perforated eardrum, middle ear infection, otosclerosis (stiffening of the middle ear bones), cholesteatoma, and congenital anomalies. With a conductive hearing loss, it is possible that medical intervention may result in partial or complete restoration of hearing. In these cases, an appropriate medical referral is warranted.
Mixed hearing loss is a combination of sensorineural and conductive hearing loss.
While it’s possible to treat hearing loss with hearing aids, vision problems can amplify hearing loss, reducing the effectiveness of hearing aids. How is that possible?
The visual connection
What you see influences what you hear. Visual cues, made possible thanks to good vision help you assess and monitor the environment around you. Good vision enables you to see where you are, the people you’re talking to, and the expressions on their faces. Your peripheral vision allows you to see your surroundings.
For someone who has problems hearing, visual cues, such as reading lips and facial expressions, are even more critical to understanding what someone is saying. You can see if the person is sad or happy, laughing or crying. You can see their lips move as they respond to you. Even the most sophisticated hearing aids can’t provide you with the visual input that’s vital to understanding what someone is saying.
Vision is also connected to our balance system, according to the Vestibular Disorders Association. To maintain balance and navigate space in the physical world, we must organize and integrate information from the visual (eyes), proprioceptive (information perceived through our muscles and joints to tell us where we are in space) and vestibular (inner ears sensing motion, equilibrium and spatial awareness) systems. A deficiency in any of these three vital systems can have a dramatic impact on the person’s ability to maintain good balance.
As we age, many common vision problems, such as cataracts, glaucoma and macular degeneration, can cause problems with vision, ultimately impacting the ability to communicate and understand speech, awareness of the environment around you, and your ability to maintain good balance.
To be sure your hearing, vision and balance systems are all working in harmony, have routine vision and hearing examinations to check for any changes or problems.