Yes blind people can cry. The eye may look like a ridiculously small garlic shaped structure situated between two bony sockets. But the intrinsic mechanism and fine details of the structures from the lid down to the nerves of the optic nerve are something that is a wonder in itself. For understanding the concept of blind people and their crying mechanism it is first important to have an idea about both of them.
Lets learn in detail.
What is blindness?
In simple words, blindness is lack of vision. The medical community has a more apt name for it in the form of ‘Visual impairment’. Visual impairment has been described as a complete or decreased ability to see objects that in turn impacts the day to day activities of the individual. Visual impairment can be either reversible when the lost vision is recoverable through surgery or treatment measures. It is irreversible when the damage cannot be reversed back.
Lets talk about visual impairment
Your visual impairment is classified as low visual acuity or moderate visual impairment when your best corrected vision is between 20/70-20/400 with a restricted visual field if 20°. It is considered blindness when the visual acuity is 20/400 or less with a field of 10⁰ with a separate term Legal Blindness used in US for worse than 20/400 vision but a visual field of 20°. Simply put, blindness is a measure of the extent of damaged vision. Nowhere in the above mentioned figures and statistics is any mention made about lacrimal passage, the main structure behind the formation of tears that are shed during crying.
What is the mechanism of crying?
Crying is induced by a range physical, emotional or chemical induced trigger in the form of pain, emotions or a combination of both. This trigger sets off the Globus sensation or in simple terms ‘the lump in the throat’. The stress hormones are set off to help relax the body and mind. These stress hormones activate the tear glands and switch on the water fountain mechanism of the brain. The limbic system and the lacrimal system signal the ‘message center of the brain’ ( pons) to produce tears in an effort to regulate the stress caused by the triggers.
What happens to the body when you cry?
It has been postulated by researchers that the tears contain high amounts of prolactin, leu-enkephalin and adrenocorticotropic hormone that are important for regulating the body and bringing it back to normal self or homeostatic levels. Now the tears produced are too high to be contained in the eye. There needs to be an outlet for them to escape and there is one called ‘lacrimal apparatus’. The lacrimal gland is an exocrine gland located above the eyeball in the anterior part of orbit. It’s draining tubes or passages are connected through the main gland and end in lacrimal sac positioned in the lower portion of the eye. The excess tears are drained out through the lacrimal caruncle located near the sac. The lacrimal cavity being connected to the nasal cavity, the nose acts as a drainage outlet as well. The end result being teary eyes and a runny nose when we do cry.
Do emotions affect tears?
Turns out we don’t. There are 3 types of tears secreted by the lacrimal glands. Basal tears, reflex tears and emotional tears. Emotional tears as discussed above are secreted in a bid to stabilize the body. Basal tears are meant to lubricate your eye and protect it from bacterial infection. Reflex tears are the eyes response to external and internal irritants. Mostly made of water these tears are secreted in a bid to wash away the supposed irritant. Smoke, onions, certain perfumes and even contact lens wearing can result in reflex tears emission from the lacrimal passage.
Does the lacrimal gland protect the eye?
Having established about the type of tears and role of the lacrimal passage in tears, there is one thing that is clear. Nowhere is it mentioned that blindness and the lacrimal passage are connected. Blindness is a result of disturbances in vision and visual field. Lacrimal passage is concerned with protection and lubrication. Vision is a multi-step process that starts with light rays falling on the eye and ends with the image being processed by the retina. The retina in turn sends the visual images to the brain through the optic nerve. This is interpreted to us in the form of a multitude of images termed ‘vision’. Blindness or visual impairment is a result of serious damages to these structures.
Causes of vision loss
Conjunctiva- Conjunctiva is a transparent membrane constituting the outermost portion of the eye. Conjunctival problems cannot result in permanent vision damage but a severely inflamed Infectious conjunctiva can severely impair your vision temporarily
Cornea- Also called the refractive medium of eye, the cornea is a transparent structure through which light rays enter the eye to pass into the retina. Corneal clouding or scarring is one of the the leading causes of blindness. Ulcers, edema and degenerations all are problems resulting in varying degrees of blindness.
Lens- the lens plays a role in focusing of light rays. Opacity of lens either congenital or acquired through trauma or infectious conditions can shut out light rays outside and prevent them from falling on the retina, giving rise to vision impairment. If untreated since childhood, it can result in lazy eye induced impairment of low vision.
Aqueous and Vitreous humor – the aqueous and Vitreous humor maintain shape of the eye and maintain eye pressure. They also act as a clear medium for light to pass through them before reaching the retina. Damage to any of them through glaucomatous changes or hemorrhages can result in severe vision impairments and permanent blindness.
Retina and Choroid – Retinal degenerations, dystrophy , inflammation or genetic induced defects in them can lead to severe vision impairment and subsequently blindness. Similarly choroidal tumors and traumatic changes are some other factors causing permanent blindness. Sometimes these choroidal tumors lead to the complete surgical removal of the eye as a preventive measure affecting the vision of the eye.
Blind people and Aqueous tear-deficiency
A blind man has the ability to cry despite his condition. A person with normal vision can suffer from a condition called ‘aqueous tear deficient dry eye’. If a blind man suffers from aqueous deficiency or from keratoconjunctivital sicca, his tear production can be severely impacted. This will cause less tears production. Additionally if his/ her blindness is a result of severe ocular burn that has permanently damaged the lacrimal system, he will not be able to shed years. If none of these conditions exist and the lacrimal passage is intact, there will be tears either for his emotional, protective or physical causes.
Take home factor
Blind people can cry as long as they are stimulated by external stimulation to shed the tears. Not just cry, some people can actually perceive light around them on the basis of the the extent of visual impairments. As long as the lacrimal passage operates and his nerves are active and alert, his crying due to any reason will produce tears from his passage and provide his body the required external coping mechanisms.