Many of us put more value to our sense of vision than to other senses like smell or taste. And the first sign of a visual disturbance triggers anxiety and stress. But vision problems are not uncommon in the modern world. Refractive errors like myopia (shortsightedness) are commonplace these days and can be easily corrected. It is unlikely to lead to serious disturbances in vision even in the long term. However, not every visual disorder is as easily treated. Sometimes blurred vision is an early symptom of a more serious eye disorder that can eventually lead to blindness.
Eyes and Vision's Articles Archives
Bell’s palsy is a sudden paralysis of one side of the face that is often mistaken for a stroke. It causes anxiety and panic for both the patient and their loved ones, but unlike a stroke the consequences of Bell’s palsy is almost never fatal. Most cases of Bell’s palsy recovers completely and even without treatment. Symptoms typically ease within a few weeks from the time it starts but sometimes can take as much as 6 months to resolve completely. In some rare cases Bell’s palsy may recur but for the vast majority of patients they never experience it again.
Visual acuity is our ability to see clearly. As humans our eyesight may not be as impressive as some other mammals but nevertheless it serves us sufficiently to conduct our daily activities. But eyesight problems have become commonplace in the modern world for a number of different reasons. It is lifestyle-related, due to genetics and even associated with some of the chronic diseases that have become common these days. The common causes of bad eyesight can vary. It may be a problem with the way light is bent, the amount of light that can enter the eye or a deterioration of the light-sensitive eye tissue.
Our body can only sustain activity for a certain period of time in a day before it needs to “recharge” with a restful sleep. One of the ways that you know that is time to rest is when the eyelids becoming “heavy”. This is a common way to describe the difficulty in keeping the eyelids open. The weight of your eyelids do not actually change. Instead the eyelid muscles become tired and experience difficulty in keeping the lids opened. However, there are times when you have no choice but to ignore this signal or continue to have heaviness of the eyelids despite having slept adequately.
Eyestrain or eye fatigue has become common place in everyday life for many of us. Most of the time it is nothing more than an annoyance but for some people it can be quite debilitating. Fortunately eyestrain does not lead to any permanent complications but the symptoms may recur on such a frequent basis that it affects a person’s life and even their ability to work. Eyestrain is often a result of ignorance rather than just being overworked. A few simple measures that will take only a few minutes can prevent eyestrain, even amidst a busy work schedule.
Fungal keratitis is an infection of the cornea caused by a fungus. Although keratitis (corneal inflammation) can occur for several reasons, a fungus is one of the more common causes of infectious keratitis. It can lead to severe damage of the eye and blindness if not diagnosed early or left untreated for long periods of time. Fungal keratitis can affect any person but it is more commonly seen among contact lens users. It has also become a significant indicator of HIV infection, particularly in Africa. Although the elderly and patients who are immunocompromised are more likely to be affected, fungal keratitis can also occur in the immunocompetent and young individuals.
Hyphema is a condition where there is a collection of blood inside the front of the eye (anterior chamber). The accumulation of the blood within the anterior chamber is usually visible. It occurs with injury to the eye, during or after surgery and in rare cases it may arise as a consequence of certain diseases. Depending on the extent of the bleeding, a hyphema may block the vision either partially or completely. The sight of blood in the front of the eye is often the most distressing symptom, along with the pain. However, the lack of visible blood does not mean that there is no bleeding as is the case with a microhyphema.
The eyes are made up of very delicate tissue, some of which are exposed to the environment. Although the thin outer lining known as the conjunctiva and the eyelids protect the eye tissue, the eyes are more prone to various forms of injury more so than any other part of the body. Naturally when one is faced with an injury to the face, it is instinct to first cover the eyes.
Being such sensitive parts of the body, it is normal for discomfort to arise in the eyes even with a little strain or slight injury. One of the common sensations that a person experiences in the eye is a burning feeling, which can sometimes be severe enough to be painful. At other times there may be the sensation of heat in the eyes without actually feeling like a burn. Both these sensations, burning and heat, can be due to a number of causes some of which are minor while others can be very serious and even permanently damage the eye. Other types of discomfort may include an aching feeling, soreness or grittiness in the eyes.
Vision Problems Definitions
What is vision?
Vision is the ability to perceive the surrounding environment by interpreting the images cast by light on the eye. This is possible through the visual apparatus the eyeball, optic nerve and brain. The eyeball is responsible for focusing a sharp image and converting the light into nerve impulses. The optic nerve then carries these signals to the cerebral cortex. The brain then decodes these impulses into images – visual perception.
What is visual acuity?
Visual acuity is the clarity or sharpness of vision. Although the ability to see clearly varies slightly from person to person to some degree, and the visual apparatus attempts to maintain clear and sharp images, there is a point of reference established which is considered the norm among humans. This is sometimes referred to as 20/20 vision.
What are vision problems?
Vision problems or eyesight problems is a broad term used to describe any defect in the ability to see. It can refer to short sight, long sight, blurred vision, cloudy vision, double vision and other defects in the visual field like floaters, shadows, halos or flashing lights.
What are the common vision problems?
The most common vision problems are nearsightedness (myopia), farsightedness (hyperopia), astigmatism and presbyopia. These problems are due to an error in refraction – the way light is bent as it passes through the eyeball in order to cast a sharp image.
Corneal transplantation, also known as corneal graft or keratoplasty, is usually done when there is loss of vision in one eye due to damage to the cornea as a result of disease or injury. The cornea is the transparent layer of tissue in front of the eye. When the cornea becomes cloudy, light cannot enter the eye sufficiently well, thus causing poor vision or blindness. Corneal transplant is one of the most commonly performed transplant surgeries where the damaged cornea is replaced by corneal tissue obtained from another human eye. The corneal tissue for transplant should be taken soon after death of the donor. Overall, a corneal transplant usually has a good outcome but graft rejection may be an undesirable complication.
The outer curved part of the eyeball is known as the cornea. It is transparent and overlies the colored iris and the middle aperture known as the pupil (“black of the eye”). The fluid-filled space between the cornea and iris is known as the anterior chamber. Light entering the eye through the cornea is bent (refracted) passes through the pupil to the lens where it is refracted further and then focused on the most sensitive part of the retina.
The cornea is composed of 5 layers – corneal epithelium (outer), bowman layer, corneal stroma, descemet membrane and corneal endothelium (inner). It lacks blood vessels but receives nutrients from the tears at the front and the aqueous humor at the back. An extensive nerve supply mainly from the opthalmic division of the trigeminal nerve (CN V) makes it one the most sensitive tissues in the body. The cornea, particularly the outer layer, is constantly replenishing itself – old cells are shed and passed out with the tear drainage while new cells move centrally from surrounding epithelium and frontwards from the underlying layers.
The eyelids are protective flaps that shield the eyes. It also helps to spread out tears over the eye. The eyelids are delicate yet effective shielding structures and is made up of several layers. It is covered by skin with the inside lined by a continuation of the conjunctiva known as the palpebral conjunctiva. Underneath the skin is a subcutaneous layer that overlies the orbicularis oris muscle, palpebral ligament and a thickened connective tissue plate known as the tarsal plate. The upper eyelid (palpebra superior) is larger than the lower eyelid (palpebra inferior). A specialized sebaceous gland in the rim of the eyelid secretes an oily substance known as meibum. Hairs extending from the borders of the eyelids (eyelashes) serves to further protect the eye from dust and debris that can injure the eye tissue.
Tears are a clear fluid that serve to moisturize the outer parts of the eye, prevent invasion of the eye tissue by any microorganisms, wash away any dirt and debris that can irritate the eye and provide lubrication for the movement of the eyeball against the eyelid. It is composed of the secretions of three different glands associated with the eye and forms a thin film over the exposed area of the eye. The quantity of tears is balanced by sufficient yet not excessive tear production and secretion and adequate drainage of the secreted tears. However, any disruption in secretion or drainage can lead to an excess or deficiency of tears leading to watery eyes or dry eyes respectively.
Refractive eye surgery includes a number of procedures aimed at altering the parts of the eye that bend light, namely the cornea on the outside and lens in the eyeball. It is these errors in refraction that cause the most common vision problems – myopia (nearsightedness), hyperopia (farsightedness) and astigmatism. This has reduced the need for and inconveniences associated with the use of eyeglasses and contact lenses to correct these refractive errors. However, it has not totally removed the need for these other corrective measures as some persons may still require eyeglasses and contact lens for optimal visual acuity. Refractive eye surgery was drastically improved with the advent of the excimer laser that allowed for laser-based procedures such as LASIK, LASEK and PRT which are now more commonly done. Nevertheless there are several other, non-laser procedures that can be done to correct refractive errors of the eye.
Refractive eye surgery was revolutionized with the introduction of excimer laser-based procedures. Overall, laser-based procedures dramatically improved the outcome, cost effectiveness and popularity of refractive surgeries thereby making it a viable choice for correcting these common vision problems. A number of surgical procedures are currently in use for correcting myopia (nearsightedness), hyperopia (farsightedness) and astigmatism. However the surgical correction of presbyopia is still not well developed.
The conjunctiva is the a thin transparent mucous membrane that covers the outer part of the eye and continues to line the inner eyelid. It helps with lubrication by producing small quantities of tear-like fluid although most of the lubrication comes from the lacrimal glands (tear glands).
The conjunctiva is similar to normal skin in that it is made up of squamous epithelium although it is non-keratinized. It also serves as a barrier between the delicate eye tissue and the environment and plays an important role in immune responses. The conjunctiva is bombarded daily with dust, chemicals, microbes and other irritants and when injured it becomes inflamed. This causes it to appear red and is commonly referred to as conjunctivitis.
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