diease

Far Sightedness ( Hyperopia)


OVERVIEW OF Far Sightedness ( Hyperopia) :

People with Far sightedness also called as hyperopia may see the objects which are far away from them but find difficulties in seeing the objects which are closer to them.


STRUCTURE of Far Sightedness ( Hyperopia) :

Cornea:

It is the clear surface of the eye which allows the light to pass through it and it directly covers the iris and pupil providing a layer of protection.

Lens:

It is located behind the iris and it is the part of the eye which aids in focus. The lens can change the shape to alter the focal distance of the eye and focuses the light rays that pass through the retina at a right angle. In aged peoples protein gets buildup in the lens giving rise to cataract. In the treatment of cataract the physician might removes the lens and replaces it with new one.

Aqueous humour:

It is a watery fluid that the eyes constantly produces in order to maintain the good pressure in the eye and lso the aqueous humour might provides the nutrient supply to the  cornea.

Ciliary muscle:

The ciliary muscle actually changes the shape of the lens and make them focus properly. It maintains the lens in the coorect position in the eye’s middle layer and regulates the flow of aqueous humour within the eye.

Extraocular muscles:

The extraocular muscles include medial rectus, lateral rectus, superior oblique, inferior oblique, superior rectus and inferior rectus. The medial rectus is the largest of the all the six extraocular muscles. It makes the pupil to be in the median state that is towards the nose and it make sure that the eyes are aligned correctly. If there are any problems with the medial rectus it can lead to the strabismus.

Lateral rectus muscle:

It helps in the lateral movement of the eyes. If there is any problem with this muscle one might experience estropia.

Retina:

It is present at the back of the eyes. The main function of the retina is to collect the information from the lens and send it to the brain for visualization. There are 2 photoreceptors on the retina A) Rods B) Cones.  Rod are responsible for the dark and light, picking up on motion and cones are responsible for the colour vision. Problems within the retina results in loss of vision.

 

 

Iris:

It is pigmented muscular layer which is present between the cornea and lens and it controls the amount of light entering the eye.

Sclera:

It is termed as the white structure of the eyes and it supports the eyeball and cornea.

Choroid: 

This is a major blood vessel which sits between the retina and the sclera at the back of the eye. It nourishes the outer layers of the retina and keeps the eye at the right temperature. It also provides the right amount of oxygen and blood flow to the retina, helping the eye to function well.

Macula:

It is the center part of the retina .  macular regeneration might result in loss of vision.

Optic nerve:

The optic nerve is the mediator friendly which transmit the signals from the retina to the brain. It consists of million of nerve fibers and it is considered as the part of the central

nervous system. Glaucoma might cause severe damage to the optic nerve

Vitreous humour:

 The vitreous humour is a liquid in your eye with the consistency of gel, and sits behind your lens but in front of your retina. If any substances enter the vitreous humour, they are referred to as floaters.


CAUSES :

The eyeball is too short

The cornea is curved to an extent

Older age


PATHOPHYSIOLOGY :

The eye consists of two parts that helps them to focus the image.

The cornea is the clear, dome shaped front surface of the eye.

The lens is the clear structure which helps in visualization of the object.

A cornea and lens with the curvature bend all incoming light to make the sharply focused image directly on the retina at the back of the eye.

A refractive error:

If the cornea or lens is not smooth or has anyother abnormalities it makes them difficult to refract the light and makes the image blurred. Farsighteness occurs when the lens is too short than normal or the cornea is curved too little.  This effect is the opposite of nearsightedness.

Other refractive error:

Nearsightedness (myopia):

It occurs when the eyeball is longer than normal od the corneal curvature is too steeply. Instead of being focused precisely on the retina  light is focused in front of the retina, resulting in the blurry appearance for distant objects.

Astigmatism:

Lens and cornea are curved more steeply in one direction than it is in another. Uncorrected astigmatism blurs your vision.

The following is the normal mechanism of the eye:

Light enters the eye.

Light refracts as it passes through two parts. First comes the cornea, the covering at the front of the eye. Then comes the lens, a clear piece that focuses the light deeper into the eye.

The light forms a focused point onto the retina, a thin layer of tissue at the back of the eye

The retina sends information to the brain.

The brain translates the messages into images.


COMMON CLINICAL SIGNS AND SYMPTOMS :

Symptoms:

Inability to focus on nearby objects

Headaches

Blurry vision

Eye strains

Fatigue or tiredness after reading closely.


DIAGNOSTIC :

Physical examination:

         Acuity is measured when the patient stands 6m away from the snellens chart.If this could not be measured the chart can be held at 36 cm away from the site. Each eye is tested separately by closing one with an solid object or finger tightly. If the patient  cannot see within 6m then 3 m is tested with the help of chart.

       If the patient finds difficult to see the chart then the ophthalmologist prefer by keeping different numbers in finger and ask those persons to count them.

       The examiner uses this to check whether the patient is able to perceive the finger or else he tends to reflects the light in the patient’s eye to look for perception of reflection.

       Then the visual acuity is checked. The acuity is checked with or without the use of glasses. If the acuity is checked with glasses and it is correctable then it accounts for refractive error.

     If patients do not have their glasses, a pinhole refractor is used. If a commercial pinhole refractor is unavailable, one can be made at the bedside by poking holes through a piece of cardboard using an 18-gauge needle and varying the diameter of each hole slightly. Patients choose the hole that corrects vision the most.

     If acuity corrects with pinhole refraction, the problem is a refractive error. Pinhole refraction is a rapid, efficient way to diagnose refractive errors, which are the most common cause of blurred vision. However, with pinhole refraction, best correction is usually to only about 20/30, not 20/20.

 

Eye examination:

The eye is checked  for pupillary reflex by flashlight. The cornea is tested for opacification. This is used for accommodation reflex.

Assess the macular function with Amsler grid- this examines the central vision.The amsler grid contains many squares and this test is used to access the corners,rows and columns of the square.

Extra ocular movements should be checked.

Retinoscopy:

 The main aim of the test is to diagnose farsightedness or near sightedness by observing the reflection of light off the patient’s retina.  The retinoscope is used to shine the light in the eye.

An instrument called phoropter measure the exact level of the refractive error.

 


TREATMENT AND PROGNOSIS :

Treatment:

The main aim of the treatment is to focus the light on the retina through the corrective lenses or refractive surgery.

Prescription lenses:

Eyeglasses: lenses is wide and it ilcudes single vision, bifocals, trifocals and progressive multifocals.

This is the easiest way to sharpen the vision caused by farsightedness. The variety of eyeglass

Contact lenses: these lenses are worn on the eyes.

Refractive surgeries:

Laser assisted in situ Keratomileusis (LASIK):

In this procedure the ophthalmologist incise the cornea and make a thin flap. Then the physician might uses a laser to adjust the curves of the cornea that corrects the farsightedness. The recovery from LASIK is comfortable when compared to other procedures.

Laser assisted subepithelial keratectomy(LASEK):

The surgeon makes ultra thin flap in the cornea’s outer protective cover. Then the physician uses the laser to reshape the cornea’s outer layers, changing the curve and then replaces the epithelium.

Photorefractive keratectomy(PRK):

In this procedure the surgeon completely removes the surface epithelium then uses the laser to reshape the cornea.

 


PROGNOSIS :

 The prognosis is good with the contact lenses or eyeglasses. If any severity arises then surgery is indicated


PREVENTION :

Life style changes:

Avoiding focusing eye on monitor for prolonged time and diet modifications.

Vitamin and hormone regulating substances

Take healthy foods and vitamin enriched foods

Working on computer foe many hours might result is xeropthalmia(dry eyes)

If your are an diabetic person check and inspect for the blood glucose level and take the proper medications

Incase of hypertensive it is best to always have routine checkups since it might leads to glaucoma

Blinking fast and continuously help to wear off the tear flim that resides in your retina.