eye function

How does an eye work?

 In this blog we will look at how does an eye work and what are the common diseases that affect them. We will discuss about specific diseases in subsequent blogs.
An eye works like a camera. In camera there are focusing lenses which focus light coming from an object into film of the camera.
Cornea : Similarly in the eye there are 2 focusing organs. First is cornea. It’s the transparent part of the eye which is visible to us from outside. It’s like the outer glass of a watch. It is the most powerful focusing surface of the eye. Loss of transparency because of scar caused by injury or infection leads to severe visual disability. Similarly change in shape of cornea due to certain congenital or acquired diseases can also lead to vision loss. These are generally known as ectatic corneal disorders,  Keratoconus being most common.

Iris & Pupil

Inside of that is the pupil which we can see change its shape depending on the brightness of ambient light. It becomes small in size, constricts, when the light is bright and becomes larger in size, dilated, when light is dim. A pupil is like the aperture of the camera. A pupil is the central opening in Iris. It’s the color of Iris that gives color to our eyes. In darkers races like Asians, Indians and african races the iris has a lot of pigments, hence eye color is dark while in fairer races Iris lacks pigments making them appear grey, green or blue. Certain autoimmune or infectious diseases can cause inflammation of Iris leading to redness, pain, photophobia and is known as iridocyclitis.

iris and pupil
Anterior chamber and angle of the eye


Anterior chamber and angle of the eye.

The clear area between back of the cornea and iris is known as anterior chamber. It is filled with transparent liquid known as aqueous fluid. This fluid gets circulated continuously and is important to maintain pressure inside the eyeball, known as intraocular pressure (IOP) and hence its shape.
The angle where iris and cornea meet is known as angle of the eye. It contains pores through which transparent fluid inside the eye gets drained into blood circulation.
Glaucoma is a disease where the drainage pathway at angle of the eye gets blocked, leading to rise in intraocular pressure (IOP)  which in turn damages nerve of the eye. Learn more about Glaucoma disease

The lens

The lens of the eye is behind the iris. It also helps in focusing the light onto the film of the eye, the retina. The lens is held in suspended position behind the iris by thin fibres known as zonules. It makes it possible for lens to change its shape because of these zonules,this inturn makes it possible for the eye to work as auto focus camera and focus at different distances. This autofocus mechanism is known as accommodation. Accommodation starts becoming weak after age of 40 and that’s when one requires glasses to look at near objects. This is a natural process and is known as presbyopia. In young individuals the lens of the eye is completely transparent, however as one grows older, this transparency progressively reduces and it becomes opaque. This is known as Cataract. As the cataract becomes more and more opaque patients vision progressively reduces. When it reaches a point where she is unable to do daily activities, cataract surgery with intraocular lens implantation is done. In olden days when techniques and technology for cataract surgery was primitive, doctors used to wait for Cataract to mature. However with improvements in technology and surgical techniques, surgery can be done when a patient feels the need and need not be postponed till complete blindness has developed. A patient who is homebound and has limited visual needs may choose to wait a lot longer than someone who leads an active lifestyle and even minimal visual disturbance hampers daily life.



The Retina

Retina is the film of the eye. It is present in the back of the eyeball and is at a distance of   almost 17-18mm from the back of the lens. The retina is made of sensitive cells known as photoreceptors. The nerve fibres of these photoreceptors pass through the optic nerve and take vision to the brain. Depending upon the position of cell bodies and nerve fibres, 10 different layers of retina can be distinguished!!
There are 2 types of photoreceptors, cones & rods. The cones are highly sensitive and are responsible for fine vision like color of objects, intricate details, reading vision etc. Cones are mainly present in the central portion of retina known as Macula. Center of the macula is a very tiny area, known as fovea. Fovea is almost as small as a pinhead. But it is responsible for fine vision almost entirely.  Rods are more sensitive in dim light conditions and help one see in low contrast conditions like dusk time. However rods are unable to distinguish fine details. They are more in numbers in Peripheral retina.
There is a small blood vessel which carries blood supply to the retina known as central retinal artery. It bifurcates into many smaller branches after entry into the eye. Similarly many tiny blood vessels carry impurities from cells of the retina and merge into larger branches till it forms a single vein known as central retinal vein. Central retinal artery and central retinal vein share common entry/ exit point on the optic nerve head. There are no blood vessels in the Fovea which is necessary for fine visual capability, it is known as the Foveal Avascular Zone (FAZ).
Retina can be affected by many systemic diseases like diabetes or hypertension. Swelling or detachment of retina can lead to serious visual morbidity and often needs prolonged treatment. Other diseases like age related macular degeneration (ARMD/AMD) can hamper reading/ writing vision significantly. Visit the best Retina Specialist in Nashik at Bapaye Eye Hospital.
KNOW MORE ABOUT EYE HEALTH
Vitreous cavity: The area between the back of the lens and retinal surface is filled with jelly like material known as Vitreous. Vitreous is densely adherent to retina in certain points like around optic nerve, Fovea and around blood vessels. In young individuals vitreous is more dense, while as a person’s age increases it becomes more liquified. This often leads to feeling of small black spots moving inside the eye known as floaters. Liquified vitreous can get separated from retina known as posterior vitreous detachment (PVD) In some individuals this process can be more sudden and leads to bleeding inside the eye &/or retinal tear formation. If retinal tears are detected in time, laser treatment can be done to avoid retinal detachment. However if retinal detachment does develop, it needs surgical treatment.
The choroid: A layer of blood vessels known as choroid lies behind the retina. It supplies oxygen and nutrients to outer layers of retina. There is a tight barrier between retina and choroid which keeps the choroidal blood vessels from growing into the retina. When this barrier breaks down, it leads to seepage of fluid and blood into the retina followed by growth of abnormal blood vessels under retinal surface, known as age related macular degeneration (ARMD/AMD). Iris is an extension of choroid in front part of the eye.
The sclera: Sclera is the outermost covering of the eye. It is white in color and opaque. It is rigid and helps to maintain shape of the eye and avoid injury to inner more sensitive organs. Various autoimmune diseases linked to arthritis may affect sclera causing it’s inflammation, scleritis.
Eyelids: Eyelids are the skin folds which cover the eyeballs. They protect the eye from injury as well as getting dryness. Every time one blinks the tears are spread over the surface of the eye to maintain the health of the cornea. Various diseases can develop because of change in position of the lids like ptosis, entropion, ectropion etc. These problems need surgical treatment.
The Conjuctiva: The conjunctiva is a thin layer of tissue which covers sclera and inside of lids, thus making blinking easier and also acts as first protective layer for the eye. Conjuctivitis is a common cause of redness eye. It is usually associated with watering &/or discharge from the eye.
Orbits: The eye is placed inside the skull in a bony cavity known as Orbits. An orbit is pear shaped, tapering from outside to inwards. The orbit has 4 walls, roof, floor, outer and inner wall. They tapers into a cone towards back known as apex of the orbit. Apex of the orbit is exit point for optic nerve into brain. It also houses muscles which move the eyes, known as extraocular muscles. Two orbits are placed on either side of nose. Two eyes on either sides of nose give us ability to have wider field of view and greater depth of focus. Depth of focus makes it possible to differentiate distances of various objects relative to each other.
Extraocular muscles : There are 6 extraocular muscles which move the eyes in various direction. Muscles of both eyes move in co-ordinate fashion thus avoiding double vision. They also help to keep eyes in straight direction and not allow eye to drift outwards. Diseases causing changes in direction of eyeballs are known as squint and surgical treatment is done on extraocular muscles to correct these problems.
The lacrimal system : The lacrimal system is concerned about tears. The tears are produced by lacrimal gland which is present in outer extent of roof of the orbit. They are drained into the nose through small holes known as punctum in upper and lower lids close to nose. A punctum is opening of a small canal in each lid, the canalicus. These canalicula open into a small pear shaped bag made of muscles, the lacrimal sac. They are then drained into the nose via small tube like structure called as nasolacrimal duct. Diseases causing reduction of tear production by lacrimal glands leads to dryness of the eye while blockage of drainage system causes watering of eyes. Most of cases where drainage is blocked can be treated by surgery to create additional drainage channel. This surgery is known as dacryocystorhinostomy.

Health of eyes is important for our vision. Even though cataract is most commonly known problem that affects the eye, there many other diseases which can endanger our eyesight. Some of these diseases can be present from birth and start in early childhood while many other diseases are develop as age of person increases.
A detailed eye examination on annual basis  from early age till old age group is absolutely necessary. A detailed eye examination should involve checking spectacle number, intraocular pressure check up and detailed retinal examination with pupilary dilatation. A day spent in one whole year in eye specialist clinic may go a long way in saving your eyesight

eye specialist in nashik
EYE HOSPITAL IN NASHIK


Contact us


Call us

094239 71283


Visit us anytime

Old Agra Rd, Behind NDCC Bank, Shalimar, Nashik, Maharashtra 422001


Send us an email

eyehospitalnashik@gmail.com



Subscribe

Sign up for our newsletter to receive all the news offers and discounts from Bapaye Eye Clinic.




Social networks

Facebook

https://www.facebook.com/bapayeeyehospital/



Contact us

Call us

+91 94239 71283


Visit us anytime

Old Agra Rd, Behind NDCC Bank, Shalimar, Nashik, Maharashtra 422001


Send us an email

eyehospitalnashik@gmail.com



Subscribe

Sign up for our newsletter to receive all the news.




Social networks

Facebook

https://www.facebook.com/bapayeeyehospital




© Designed & Promoted by Creative Graphics Managed by 1 Stop Hospital Sol. Pvt Ltd



Copyright by Creative Graphics – Mumbai  In association with One Stop Hospital Sol.