Anatomy of the Eye | Kellogg Eye Center

• Choroid
  Layer containing blood vessels that lines the back of the eye and is located between the retina (the inner light-sensitive layer) and the sclera (the outer white eye wall).  
• Ciliary Body
  Structure containing muscle and is located behind the iris, which focuses the lens.
• Cornea
  The clear front window of the eye which transmits and focuses (i.e., sharpness or clarity) light into the eye. Corrective laser surgery reshapes the cornea, changing the focus.
• Fovea
  The center of the macula which provides the sharp vision.
• Iris
  The colored part of the eye which helps regulate the amount of light entering the eye. When there is bright light, the iris closes the pupil to let in less light. And when there is low light, the iris opens up the pupil to let in more light.
• Lens
  Focuses light rays onto the retina. The lens is transparent, and can be replaced if necessary. Our lens deteriorates as we age, resulting in the need for reading glasses. Intraocular lenses are used to replace lenses clouded by cataracts.
• Macula
  The area in the retina that contains special light-sensitive cells. In the macula these light-sensitive cells allow us to see fine details clearly in the center of our visual field. The deterioration of the macula is a common condition as we get older (age related macular degeneration or ARMD).
• Optic Nerve
  A bundle of more than a million nerve fibers carrying visual messages from the retina to the brain. (In order to see, we must have light and our eyes must be connected to the brain.) Your brain actually controls what you see, since it combines images. The retina sees images upside down but the brain turns images right side up. This reversal of the images that we see is much like a mirror in a camera. Glaucoma is one of the most common eye conditions related to optic nerve damage.
• Pupil
  The dark center opening in the middle of the iris. The pupil changes size to adjust for the amount of light available (smaller for bright light and larger for low light). This opening and closing of light into the eye is much like the aperture in most 35 mm cameras which lets in more or less light depending upon the conditions.
• Retina
  The nerve layer lining the back of the eye. The retina senses light and creates electrical impulses that are sent through the optic nerve to the brain.
• Sclera
  The white outer coat of the eye, surrounding the iris.
• Vitreous Humor
  The, clear, gelatinous substance filling the central cavity of the eye.

The five senses include sight, sound, taste, hearing and touch. Sight, like the other senses is closely related to other parts of our anatomy. The eye is connected to the brain and dependent upon the brain to interpret what we see.

How we see depends upon the transfer of light. Light passes through the front of the eye (cornea) to the lens. The cornea and the lens help to focus the light rays onto the back of the eye (retina). The cells in the retina absorb and convert the light to electrochemical impulses which are transferred along the optic nerve and then to the brain.

The eye works much the same as a camera. The shutter of a camera can close or open depending upon the amount of light needed to expose the film in the back of the camera. The eye, like the camera shutter, operates in the same way. The iris and the pupil control how much light to let into the back of the eye. When it is very dark, our pupils are very large, letting in more light. The lens of a camera is able to focus on objects far away and up close with the help of mirrors and other mechanical devices. The lens of the eye helps us to focus but sometimes needs some additional help in order to focus clearly. Glasses, contact lenses, and artificial lenses all help us to see more clearly.  

Eye Anatomy – Exeter Eye

The human eye is remarkable. Although it is small in size, the eye arguably provides us with the most important of the five senses – vision.

Vision occurs when light enters the eye through the pupil. With help from other important structures in the eye, like the iris and cornea, the appropriate amount of light is directed towards the lens.

Just like a lens in a camera sends a message to produce a film; the lens in the eye refracts incoming light onto the retina, where messages are encoded. The retina, which is made up by millions of specialised cells known as ‘rods’ and ‘cones’, transforms the image into electrical energy and this is sent to the optic disk on the retina, where it will be transferred via electrical impulses along the optic nerve to be processed by the brain.

The eyeball contains three layers:

• The outer layer, formed by the cornea and sclera
• The middle layer, holding the primary blood supply for the eye and containing the iris and pupil
• The inner layer, comprised of the retina

The eyeball also contains three chambers of fluid:

• Anterior chamber, between the cornea and iris
• Posterior chamber, between the iris and the lens
• Vitreous chamber, between the lens and the retina

The anterior and posterior chambers are filled with aqueous humour, which is a watery fluid that provides nourishment to the interior eye structures and helps to keep the eyeball inflated. The vitreous chamber is filled with a thicker fluid called vitreous humour, a transparent gel which is 99% water, which helps the eyes to stay inflated.

What makes up an eye?

• Choroid: the middle layer of the eye between the retina and the sclera. It also contains a pigment that absorbs excess light so preventing blurring of vision.

The choroid is the spongy middle layer of your eye located between the sclera and the retina. Filled with blood vessels, the choroid’s function is to nourish the outer layers of the retina.

• Ciliary body: the part of the eye that connects the choroid to the iris.

The ciliary body is located behind your iris, near the crystalline lens. This structure has two functions. The aqueous fluid that fills the front of your eye is made inside the ciliary body. Also, the ciliary body is made up of muscles that allow the eye to focus at different distances.

• Cone cells are the second type of light sensitive cells in the retina of the eye. The human retina contains between six and seven million cones; they function best in bright light and are essential for acute vision (receiving a sharp accurate image). It is thought that there are three types of cones, each sensitive to the wavelength of a different primary colour – red, yellow or blue. Other colours are seen as combinations of these primary colours.

• Cornea: the transparent circular part of the front of the eyeball. It refracts the light entering the eye onto the lens, which then focuses it onto the retina. The cornea contains no blood vessels and is extremely sensitive to pain.

The cornea is the clear front window, representing one-sixth of the outer layer of your eye. The primary function of the cornea is to focus and transmit light onto the retina.

• Conjunctiva: the thin, moist, clear membrane that covers the sclera – the white part of the eye. It is the skin that lines the eye socket and protects and lubricates the eyeball.

• Crystalline Lens: The transparent structure inside of the eye located directly behind your iris. The sole function of your lens is to focus light rays onto the retina.

• Fovea: forms a small indentation at the centre of the macula and is the area with the greatest concentration of cone cells. When the eye is directed at an object, the part of the image that is focused on the fovea is the image most accurately registered by the brain.

• Iris: regulates the amount of light that enters your eye. It forms the coloured, visible part of your eye in front of the lens. Light enters through a central opening called the pupil.

The iris is the colored portion of your eye. Located behind the cornea, and in front of the crystalline lens. This structure separates the anterior and posterior chambers of the eye. The function of the iris is to help regulate the amount of light that enters your eye.

• Lens: a transparent structure situated behind your pupil. It is enclosed in a thin transparent capsule and helps to refract incoming light and focus it onto the retina. A cataract is when the lens becomes cloudy, and a cataract operation involves the replacement of the cloudy lens with an artificial plastic lens.

• Macula: a yellow spot on the retina at the back of the eye which surrounds the fovea.

The macula is located roughly in the center of the retina. It is a small and highly sensitive part of the retina responsible for detailed central vision. The fovea is the very center of the macula. The macula allows us to appreciate detail and perform tasks that require central vision such as reading or driving a car.

• Optic disc: the visible (when the eye is examined) portion of the optic nerve, also found on the retina. The optic disc identifies the start of the optic nerve where messages from cone and rod cells leave the eye via nerve fibres to the optic centre of the brain. This area is also known as the ‘blind spot’.

• Optic nerve: leaves the eye at the optic disc and transfers all the visual information to the brain.

The optic nerve is located in the back of the eye. This structure is responsible for transmitting the images we see from the retina to the brain. The front surface of the optic nerve, which is visible on the retina, is called the optic disk. There are millions of nerve fibers that pass through the retina and converge to form the optic nerve. When light hits the retina it is converted into electrical impulses and carried along these fibers through the optic nerve and to the brain.

• Pupil: the circular opening in the centre of the iris through which light passes into the lens of the eye. The iris controls widening and narrowing (dilation and constriction) of the pupil.

The pupil is the dark center in the middle of the iris. The pupil’s function is to regulate how much light enters the eye. The pupil’s size is automatically varied to regulate the amount of light entering the eye.

• Retina: a light sensitive layer that lines the interior of the eye. It is composed of light sensitive cells known as rods and cones. The human eye contains about 125 million rods, which are necessary for seeing in dim light. Cones, on the other hand, function best in bright light. There are between six and seven million cones in the eye and they are essential for receiving a sharp accurate image and for distinguishing colours. The retina works much in the same way as film in a camera. The retina’s function is to sense light and create impulses that are sent through the optic nerve and to the brain.

• Rod cells are one of the two types of light-sensitive cells in the retina of the eye. There are about 125 million rods, which are necessary for seeing in dim light.

• Sclera: the white part of the eye, a tough covering with which the cornea forms the external protective coat of the eye.

The sclera is the white portion of your eye, making up the back five-sixth’s of the eyes outer layer. The function of the sclera is to provide protection for your eye, and to serve as the attachment for the extra ocular muscles which move the eye.

• Tear Layer: Understanding the structure of tears is important in order to understand how the tears and tear film provide the eye with a number of specialized functions.

Our tears are formed by tiny glands that surround the eye. Tears are comprised of three layers: oil, water, and mucous. The lower mucous layer serves as an anchor for the tear film and helps it adhere to the cornea. The middle layer is comprised of water and the outer layer seals the tear film and prevents evaporation. The tear film serves several purposes. It keeps the eye moist, creates a smooth surface for light to pass through the eye, nourishes the front of the eye, and provides protection from injury and infection. When we blink, the eyelids smooth and spread the tear film so that it is uniform across the surface of the cornea. Excess tears flow out of the eye into two tiny ducts, which then drain into the nasal passage.

• Vitreous Body: A clear, jelly-like substance that fills the center of the eye.

It is composed mainly of water and comprises about two thirds of the eye’s volume. The vitreous helps the eye maintain a round shape and is attached to the retina at various points, including the macula and the optic nerve.

• Zonules: a series of fine fibers that connect the crystalline lens to the ciliary body. The function of your zonules is to hold the lens in place in the eye.

If you are worried about the health of your eyes, take a look at the range of symptoms you may experience, call us on 01392 699969, arrange a call back or get in touch online.

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Sparks in the eyes | Articles

Small sparkling dots before the eyes – sparks – are familiar to many. This symptom indicates a violation in the work of the retina. Doctors refer to this phenomenon as photopsy – false light perceptions.

Sparks before the eyes are also spoken of in cases where dots of white, yellow or golden color appear in the field of view. They are especially noticeable in sunny weather, in bright light. If you look at a white surface (for example, a wall) on a sunny day, it will be covered with bright “sparks”. In some cases, patients complain of manifestations that occur with their eyes closed.

Why do sparks appear in the eyes?

• Destruction of the vitreous body. This pathology is the most common cause of the appearance of sparks before the eyes. Their occurrence is accompanied by the appearance of floating spots, various in shape and size.
• Vitreous detachment. In people older than 50 years, wrinkling of the vitreous body is often diagnosed – the most complex pathology of the vitreous body. This deformation leads to severe tension at the attachment points to the retina of the vitreous body. As a result, when the eye moves, sparks appear. They are especially noticeable with closed eyes.
• Vascular anomalies. Often the appearance of sparks before the eyes accompanies hypertension, diabetes mellitus and other diseases associated with vascular damage. Spasms occur in the eyes, which cause the appearance of foreign objects.
• Retinal breaks. In some cases, the appearance of sparks is associated with damage to the retina. Against the background of its rupture, a rupture of the vessel may occur. As a result, blood enters the eye cavity and hemophthalmos occurs. This condition is accompanied by the appearance of a veil over the entire field of vision and a decrease in the visual acuity of the world. Retinal tear can cause retinal detachment. This is fraught with serious consequences for vision. If sparks occur, you should immediately seek help from an ophthalmologist.
• Retinal detachment. This disease is one of the most dangerous in ophthalmology, as it can lead to complete and irreversible loss of vision. With retinal detachment, sparks of red and purple colors, as well as dark shades, appear before the eyes. The intensity of objects increases over time. All this is accompanied by an active deterioration of vision.
• Eye injuries. Sparks occur directly at the moment of injury – impact or other mechanical impact. If the contusion was mild, over time, all unpleasant symptoms disappear.
• Head injury. Visual centers are located in the occipital part of the brain. A blow to this area may be accompanied by a sensation of sparks “falling” from the eyes.
• Pressure on the eye. With gentle pressure, a light spot may appear in the field of view. This phenomenon is called mechanophosphene. When the pressure stops, it disappears, so this condition is not a pathology.
• Tumors inside the eyes. If a tumor develops inside the organs of vision, over time it can lead to the appearance of sparks. This is due to the fact that in the process of growth, it begins to put pressure on the surrounding tissues.

Treatment

Sparks in the eyes are not a disease, but only a symptom of a pathology. Eliminating the cause often leads to instant relief from this manifestation. If sparks appear before the eyes, the nature of which is not completely clear or is caused by physical overstrain or severe stress, it is necessary to seek help from a specialist. The ophthalmologist will conduct an examination, assess the condition of the organs of vision and exclude (or confirm) serious eye pathologies. Examination is important, as many ophthalmic diseases are irreversible. Remember: the occurrence of sparks can be associated with retinal detachment, which leads to blindness.

In the Center for Vision Restoration, the examination is carried out using modern diagnostic equipment. Based on the results, you will receive a comprehensive consultation of an experienced ophthalmologist. We work for you every day from 8:00 to 20:00, we accept patients of any age. Our doctors will identify the objective cause of eye pathology and prescribe competent treatment. Thousands of patients come to us every year. We give them all healthy vision!

Are you interested in the cost of diagnostics and treatment at the Vision Restoration Center? Do you want to make an appointment?

Read also:

Laser cataract removal at the best price.

SHASHORINA Svetlana Alexandrovna
Ophthalmologist, candidate of medical sciences. Oculist.

Veil before the eyes – causes and treatment

However, some deviations, not very significant at first glance, indicate the beginning of a very formidable disease.

The veil before the eyes can be such an alarming sign. Usually, such a visual disorder is characteristic of a complete or partial detachment of the retina, which is responsible for the projection of visible images and their conversion into nerve impulses sent to the human brain.

Therefore, any deformation of the retina can be associated with a significant decrease in visual acuity and even complete blindness. The short-term or long-term presence of a veil in front of the eyes, associated with clouding of visual images, the occurrence of short flashes or sparks, is often evidence of the process of retinal detachment that has already begun, when its tissues are still alive and can be saved.

However, if such a symptom is not taken seriously, then the exfoliated tissues will die, and vision will no longer be restored.

Causes

In some cases, such a visual impairment is accompanied by pain in the eye, as well as nausea and vomiting, which may indicate an attack of glaucoma – a rather serious disease that often causes loss of vision.

When blurred vision occurs due to a severe bruise or head injury, this indicates a concussion. Sudden fogging or fuzziness of the image may also indicate a pressure surge. But especially often, the cause of this phenomenon is the beginning of the process of retinal detachment.

The reasons for the appearance of a veil before the eyes, as a sign of detachment and death of the retina, are quite diverse. Among them, there is a mechanical injury to the eye, and a tendency to hypertension, and the presence of some general diseases, such as arthritis, rheumatism, diabetes mellitus, adrenal dysfunction, and thyroid disease. Sometimes, some congenital pathologies associated with degeneration of this part of the eye become the cause of retinal detachment.

Sometimes the reasons for the appearance of a veil before the eyes lie in the breakdown of metabolic processes. In addition, the launch of such pathological changes can provoke the existing myopia of a strong and moderate degree. This fact is due to the fact that with the development of myopia, the eyeball is deformed, changing its shape and the retina gradually becomes thinner.

At the same time, in places of thinning, small gaps appear, where blood or vitreous substance gets. Such moisture penetrates under the surface of the retina, gradually lifting it, which contributes to detachment.

Due to the fact that this destructive process does not initially have pronounced signs, all patients at risk of developing retinal detachment should have regular vision examinations by an ophthalmologist every six months.

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Treatment

To treat the veil before the eyes, it is necessary to eliminate the causes that led to this condition.

Today, the method of repairing retinal detachment by biological welding is especially popular. This manipulation is absolutely painless and consists in welding exfoliated tissues to the fundus using a laser beam. This simple operation lasts about an hour, and the fluid that has accumulated under the retina during the disease is successfully absorbed by the end of the rehabilitation period. The procedure does not require hospitalization and is performed on an outpatient basis, on a one-day basis.

The effectiveness of the treatment of retinal detachment largely depends on the preliminary diagnosis. After all, it is very important to detect and return to its previous state and exfoliated retinal tissue, and eliminate even the smallest gap that allowed the fluid to seep under the retina. Because when even a small crack remains unwelded, the destructive process repeats itself. As a rule, with timely treatment, it is possible to return up to 98% of lost vision.

In the same case, when the veil before the eyes is not associated with retinal pathology, it often disappears spontaneously, after the elimination of the causes that provoked it.