Eye-sight problems

What are eye-sight problems?

“Eye-sight problems” is a collective term for a group of problems that impact the vision of an individual. They are common in but not restricted to elderly people. The patient may experience a range of problems starting from unclear vision to a complete loss of vision. Many of these problems can be fixed by lenses or optical surgeries. But many of the eye-sight problems which are not diagnosed or treated on time may aggravate and lead to permanent blindness. The World Health Organisation (WHO) has estimated that around 36 million people all over the world are blind and 253 million have poor vision. The statistics of WHO have also shown that India has the highest blind population in the world. Eye-sight problems of any degree can lead to a loss of performance and productivity in school-going children and the working professionals.

This article will discuss the different types of eye-sight problems, alongside their causes, types and symptoms.

Macular degeneration

Macular degeneration (MD) is the slow and painless breakdown of the eye’s macula. The macula is the central part of the retina and is predominantly made of cone cells which are the visual cells. Degeneration of the macula occurs due to loss of visual cells, cone cells, and rods cells, and thus, causes blurry vision or eventual blindness. In some rare cases, blindness can be abrupt. Since the macula degenerates with age, the disease is termed as Age-Related Macular Degeneration. If the disease is found to have a genetic linkage, it is known as Juvenile Macular Degeneration or Congenital Macular Degeneration. In the latter case, macular degeneration is an autosomal recessive eye disease.

What causes Macular Degeneration?

Macular degeneration is precipitated by a number of catalyzing factors. These are listed below-

• Age: The risk of being affected by AMD increases with age.
• Smoking: Smokers have to endure severe vision loss when compared to non-smokers.
• Heredity: People with close relatives affected by AMD are likely to develop AMD with age.
• Sunlight: Laboratory studies show that exposure to sunlight can affect the retinas.
• Diet: Obesity, intake of artificial fats and high cholesterol can increase the risk of being diagnosed with AMD.
• Race: AMD is largely observed in whites but it can affect other races as well.
• Drugs: Certain drugs namely, Aralen and phenothiazine can cause macular degeneration.
• Gender: Women are more likely to be affected by AMD.

Other general factors include-

• Inheritance of a faulty gene (usually dominant) from one parent
• Inheritance of a defective gene (usually recessive) from both parents
• Death of macular cells
• Abnormal growth and rupture of blood vessels within the macula

What are the signs and symptoms?

The common symptoms of macular degeneration are as follows-

• Partial or complete loss of central vision
• Gradual loss of color vision
• Photosensitivity (aversion to extremely bright light)
• Loss of night vision
• Difficulty reading the blackboard in school
• Defective perception of straight lines as curved or bent
• The appearance of dark spots in the central field of vision
• Problems in distinguishing minute details
• Difficulty performing tasks such as threading a needle, reading very small prints or reading street signs

What are the types of macular degeneration?

There are two main types-

• Dry MD: This is caused by thinning of the RPE, Retinal Pigment Epithelial Cells.
• Wet MD: This is caused by thickening of the membrane underlying the retina which eventually breaks.

Glaucoma

Glaucoma is a type of eye disease that occurs due to damage and death of the optic nerve. In the majority of the cases, glaucoma results from an abnormal elevation in the intraocular pressure. Faulty drainage within the eye chambers also contributes to glaucoma in many patients. Serious cases of glaucoma lead to vision disturbance and blindness.

Causes of glaucoma

• Blockage of the drainage channels of the eye, which obstructs the drainage of the intraocular fluid
• Increase in intraocular pressure due to build up of fluids inside the eye
• Damage of the sensory optic nerve due to high pressure
• Gradual hollowing of the optic disc that forces the sensitive optic nerve fibers into a curved shape

What are the types of glaucoma?

Two primary types of glaucoma have been identified so far. These are-

• Open-angle glaucoma: It occurs due to progressive clogging of the drainage paths in the eye chamber, which leads to an increased intraocular pressure.
• Closed-angle glaucoma: Here, the gap between the cornea and the iris is shortened, which causes an obstruction in fluid flow.

Warning signs

• Partial or complete loss of peripheral vision
• Loss of central vision (in the late stage)
• The appearance of multicolored (typically rainbow colored) circles around bright lights
• Pain in the head and eyes
• Blurred vision
• Nausea and vomiting
• Dizziness

Cataract

Cataract is defined as a type of vision impairment characterized by the unusual blurriness of the eye lens causing gradual opacity of lenses and loss of clear vision.

The general causes of cataracts 

• Prolonged and unprotected exposure to Ultraviolet radiation
• Trauma due to past incidents of eye-infection or eye injury
• Certain drugs such as corticosteroids and diuretics
• After-effects of previous diseases like diabetes, eczema (skin disorder), uveitis (eye inflammation), high blood pressure, glaucoma (disease of the eye)
• Continuous exposure to toxic chemicals present in the environment
• Addictive habits like smoking and alcohol consumption
• Prolonged use of vitamin supplements (hypervitaminosis symptoms)
• Diet rich in fat and deficient in anti-oxidant vitamins

What are the main signs and symptoms of cataracts?

The warning signs of cataracts are as follows-

• Impaired vision accompanied by cloudiness or fogginess
• A gradual opacity of the pupil causing loss of clear vision
• Hypersensitivity to bright light (increased glare)
• Short-sightedness (Myopia) characterized by difficulties in distance-vision
• Double vision conditions where multiple images are perceived in one eye (diplopia)
• Difficulty recognizing color (can lead to color-blindness)
• Poor vision in bright sunlight
• Poor night vision, occasionally leading to permanent night-blindness
• Frequent change in prescriptions related to eye-glasses
• Trouble performing mundane activities like reading, recognizing people or objects, driving, watching television and walking

What are the different types of cataracts?

According to morphology, cataracts are of three types-

• Nuclear Sclerotic Cataracts
• Cortical cataracts
• Posterior sub-capsular cataracts

According to etiology, cataracts are of four types-

• Degenerative cataract
• Congenital cataract
• Traumatic cataract
• Secondary cataracts

Astigmatism

Astigmatism is a refractive error in which an even distribution of light does not occur over the retina. It arises due to the imperfect curvature of the cornea. The disease is often attributed to genetic factors. It is characterized by an extreme blurry vision.

Main types Astigmatism

Based on the axis of the principal meridian, Astigmatism is of two types-

Regular astigmatism: The principal meridians are perpendicular. It has three subtypes-

• With-the-rule astigmatism
• Against-the-rule astigmatism
• Oblique astigmatism

Irregular astigmatism: Here the principal meridians are not perpendicular.Based on the focus of the principal meridian, three types are identified-

• Simple astigmatism: It is of two types- simple hyperopic astigmatism and simple myopic astigmatism.
• Compound astigmatism: It has two subtypes- hyperopic and myopic.
• Mixed astigmatism: Here the focal lines are on both sides of the retina.

Myopia

Myopia is defined as the refractive error of the eye where a person can see the nearby objects but not the ones located at a distance. The causes of myopia are usually presented as hypotheses-

• Near-work hypothesis: Myopia may develop due to overstraining the eyes in near works.
• Visual stimuli hypothesis: This attributes Myopia to working in dimly lit environments for long hours on a regular basis.

What are the different types of Myopia?

Based on the etiology, Myopia is of the following types-

• Axial Myopia: An increase in the axial length of the eye occurs in this case.
• Refractive Myopia: It is associated with the refractive conditions of the eye. It is of two types- curvature myopia and index myopia.

Diagnosis, treatment, & treatment of eye-sight problems

The diagnostic tests for the age-related eye diseases are as follows-

• Visual acuity test
• Visual field test
• Dilated eye exam
• Tonometry
• Pachymetry

The tests for the refractive eye diseases include-

• Keratometer test
• Retinoscopy
• Distance chart
• Phoropter

Refractive errors such as nearsightedness, farsightedness, astigmatism, and presbyopia can be rectified with the help of eyeglasses, contact lens or surgery. Underlying conditions such as diabetes (diabetic neuropathy), sarcoidosis (ocular sarcoidosis), sickle cell disease etc. should be taken care of.

Retinal diseases can be treated by treatment options such as lasers, cryopexy (freezing), shrinking of abnormal blood vessels, injecting medicines into the eye, retinal implants etc. Strabismus and nystagmus can be treated by vision therapy which helps to make the eyes stronger. Based on the condition, surgery might also be considered as a treatment option.

Dry eyes can be treated by using artificial tears, placing computer screens below eye level (so that the eye is not open wide), taking breaks during work, blinking the eyes more often, preventing blowing air directly into the eye and other such measures. Cataracts that affect vision are usually treated by means of a surgery.

Prevention of eye problems is mainly by protecting it from external irritants such as harmful UV radiations, hot and dry air, allergens, chemicals, insects, dust etc. A diet rich in vitamin A is advised to maintain the health of the eye. Regular eye checkups can also help in diagnosing the condition (if any) at an early stage and prevention of its progression.

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