Eyes and Vision Archives - Healthhype

Glaucoma (High Eye Pressure) Types, Causes, Symptoms

Dr. Chris — Fri, 10 Jun 2011 00:20:19 +0000

The eye has two main areas which are filled with different substances. The anterior segment (front) which constitutes about 20% of the area is filled with a clear watery fluid know as the aqueous humor. It lies between the cornea and the front surface of the lens. The posterior segment (back) which accounts for the remaining 80% of the internal area of the eye is filled with a clear gelatinous substance known as the vitreous humor. It lies between the back surface of the lens and the retina. Normal Eye Pressure The pressure within the eye is known as the intraocular pressure (IOP). It varies between 12 mmHg and 20 mmHg with an average pressure of 15 mmHg. The fluid that constitutes the aqueous humor is constantly being produced and drained in the eye. The ciliary body secretes this fluid into the posterior chamber of the anterior segment of the eye, between the front of the lens and back of the iris as explained under the human eye. The fluid then flows through the pupil to the anterior chamber where it is drained by the trabecular meshwork and then the Schlemm’s canal. This is a small drainage point that lies [...]

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Vitreous Floaters in the Eye (Seeing Floating Spots and Objects)

Dr. Chris — Sat, 11 Jun 2011 21:47:30 +0000

The path of light through the eye needs to be uninhibited in order to form a clear image on the retina. The light-sensitive receptors then elicit impulses which are sent to the central nervous system for processing. In order to achieve this, the tissues of the eye has several specialized properties to ensure that it is transparent. During it course, light will pass through the cornea, aqueous humor, lens and vitreous humor. As it travels through these substances, it is bent to varying degrees (refraction) to form a focused although inverted image on the retina. If any of these media are tainted, it will distort the sense of vision to varying degrees and particles within the eye may be perceived as a superimposed image. What are eye floaters? Vitreous floaters or simply eye floaters are translucent spots and streaks that are within the visual field without any corresponding source in the external environment. This simply means that a person can see a spot, streak or object that does not exist. Vitreous floaters are not imaginary but arise due to changes within the vitreous humor, the jelly-like substance that occupies most of the area within the eyeball. The vitreous humor gives [...]

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Common Vision Problems Causes, Types, Symptoms, Treatment

Dr. Chris — Sat, 19 Nov 2011 00:31:13 +0000

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 [...]

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Cornea Transplant Surgery (Corneal Graft, Keratoplasty)

Dr. Chris — Sat, 12 Nov 2011 16:30:49 +0000

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. Cornea Anatomy The cornea is the transparent layer of tissue that covers the front of the eye. It is responsible for refraction of light passing through it, thus enabling proper vision. Damage to any part of the cornea may interfere with vision. The cornea does not contain any blood vessels. It is nourished by tears and by the aqueous humor in the anterior chamber of the eye just behind the cornea. The function of the cornea is to protect [...]

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Scratched Cornea (Corneal Abrasion)

Dr. Chris — Tue, 01 Nov 2011 18:43:53 +0000

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 eye has several mechanisms to protect the delicate tissue of the eyeball like the eyelashes and eyelids, conjunctiva [...]

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Eyelid Inflammation (Blepharitis)

Dr. Chris — Sun, 30 Oct 2011 21:14:41 +0000

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. What is blepharitis? Blepharitis is the term for inflammation of the eyelids. It is a common condition and most of the time blepharitis affects the edge of the eyelids. Inflammation may occur on the outer front part of the eyelid in which case it is known as anterior blepharitis. Alternatively it may be present on the inner back side of the eyelid which is in [...]

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Refractive Eye Surgery for Nearsight, Farsight and Astigmatism

Dr. Chris — Tue, 25 Oct 2011 16:35:23 +0000

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. Most surgeries involve the cornea but some may also involve the lens. The most important surgical procedures currently employed in surgical correction of refractory errors are : Laser-assisted in situ keratomileusis (LASIK), laser assisted sub-epithelium keratomileusis (LASEK), photorefractive keratectomy (PRK) and laser thermal keratoplasty (LTK) have been discussed under laser eye correction. LASIK [...]

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Conjunctivitis (Pink Eye) Causes, Symptoms, Pictures, Treatment

Dr. Chris — Mon, 17 Oct 2011 19:13:58 +0000

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. What is conjunctivitis? Conjunctivitis is the inflammation of the thin clear mucous membrane lining the outer eyeball and inner eyelid. Depending on the cause of the inflammation, conjunctivitis may be categorized as infectious or non-infectious. The most common causes of infectious conjunctivitis are viral or bacterial infections while most non-infectious cases are allergic or due to irritants. If the inflammation also involves the cornea then it is known as keratoconjunctivitis and if it also involves the eyelid then it is [...]

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Astigmatic Eye and Different Types of Astigmatism

Dr. Chris — Tue, 11 Oct 2011 20:53:08 +0000

The cornea on the outer part of the eye and the lens within the eyeball are responsible for bending light (refraction) so that it focuses on the most sensitive part of the retina. The sharper the image cast on this area, the clearer of vision. The more common vision problems are associated with refractive errors – this means that the light is not bent optimally to cast a sharp image on the eye. Most people are well versed with two common refractive errors that causes myopia (nearsightedness) and hyperopia (farsightedness). Astigmatism is another refractive eye disorder that is less well understood by many yet it is one of the more common refractive errors. What is astigmatism? Astigmatism is a refractive error due to an uneven curvature (roundness) of the cornea thereby leading to a number of visual problems. Almost 9 out of 10 people have astigmatism, however, it is to such a slight degree that it usually does not create a major vision problem. Astigmatism is a bit more complex refractive error that myopia and hyperopia both in the mechanism causing the visual disturbance and the nature of the vision problem. This can vary from blurred vision to problems viewing [...]

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Hyperopic Vision (Long Sighted) and Hyperopia with Age

Dr. Chris — Wed, 05 Oct 2011 23:03:36 +0000

Light entering the eye has to be refracted (bent) so that a sharp image can be focused on the retina of the eye. The retina is the photosensitive inner layer of the eye that converts the light into nerve impulses. Via the optic nerve, these impulses are relayed to the brain and is perceived as the sense of vision. The cornea on the outer part of the eyeball and the lens within the eye are primarily responsible for this refraction of light. Common visual problems in humans are mainly due to refractive errors. This means that the light is refracted in a manner that casts a sharp image short of the retina or just past it. These refractive errors are known as myopia (short sight) or hyperopia (far sight) respectively. What is hyperopia? Hyperopia or hypermetropia is the inability to see near objects although far vision may be normal. It is also commonly known as farsightedness or long sight. With minor hyperopia the near vision is not compromised to a significant degree or sometimes not at all. The only symptoms in these cases are eyestrain and headaches and corrective lenses are not needed. With mild and severe hyperopia, the visual [...]

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