Refractive Errors
           
Myopia (short-sightedness)

Myopia is caused by the lengthening of the eyeball, such that the focal point of the image in the eye is in front of the retina. Therefore, the image that is cast on the retina is blurry. Myopic individuals are able to read clearly without glasses. The lower the power, the further away you can read. If you have high myopic power, you will have to hold your book very closely to read.

The true cause of myopia is not known. However, we know that genetics and near work stress are closely related to the progression of myopia. Therefore, children should take 5 minutes breaks to look far away and relax their eyes, after 30 minutes of reading and close work. Myopic correction using lenses takes the form of minus or negative (-) lenses.

Hyperopia (long-sightedness)

Hyperopia is the direct opposite of myopia. In this case, the eye ball is shorter than desired, and the focal point of the light rays fall behind the retina. Young individuals below 40 years of age have flexible focusing muscles and are able to bring the focus back onto the retina by working on their focusing muscles, if the hyperopic power is not high. This may cause strain or stress on the eye.

Most hyperopic individuals are born with the hyperopia. When he/she reaches more than 38 to 40 years old, reading may become blurry and distance will slowly become slightly blurry as well. Hyperopia correction using lenses takes the form of plus (+) lenses.

Astigmatism

Astigmatism is when the light is not focused at one point, but rather at two points. This may be due to the cornea being not perfectly round, but more like a rugby ball. When one side is more curved, and the other side is less curvy, the focus at the back of the eye is diffused at two separate points.

Astigmatism can occur with myopia, hyperopia, or neither. Individuals with moderate to high amounts of uncorrected astigmatism will find that night vision is most affected, as spots of light become elongated and disturbing. Astigmatism can be corrected with eye glasses or contact lenses.

Presbyopia (middle age long-sightedness)

If you are seeing well with or without glasses for distance, and is reaching 40 years of age, you may start to find that reading gets more and more difficult. You may need to hold your book slightly further away from yourself. This may mean that you are starting to develop presbyopia. Presbyopia is also commonly called middle-age long sightedness.

Presbyopia is the result of the weakening of the eye muscles, as well as losing the flexibility of the lens inside the eye. For a person below 40 years old, he/she can use the accommodation to bring the focus back onto the retina when reading. For a person above 40 years old, the focus is at the back of the retina, as the focusing muscles cannot work well anymore. Therefore, a reading prescription will be needed to correct vision for reading.

Contact Lens Related Conditions

Papillary Conjunctivitis

The contact lens is not a natural object in the eye. Therefore, sometimes our eyes can get a bit more sensitive and develop a reaction to the contact lens. The eyes can become red, itchy, and sometimes slightly swollen. This is because the eye is creating a slow sensitive reaction to the lens. In this process, mast cells build up underneath the skin. Mast cells are responsible for releasing histamines that causes itch, redness and heat. Therefore, if contact lenses are worn for prolonged hours, little bumps will appear underneath the eyelid. These little bumps contain the mast cells. This condition is called Papillary Conjunctivitis. Papillary Conjunctivitis can be treated with mast cell stabiliser eye drops, to relief and prevent the itch and discomfort.

Infections and Inflammations

If contact lenses are over-worn, the cornea may become weak. The superficial cells of the cornea may become unhealthy. If contact lens wear persists, the eye can be prone to infections, as bacteria or other micro-organisms can get access into the cornea easier. If the eye gets infected by bacteria, the eye can become very red, and swollen. Pus may discharge out of the eye. If the eye gets infected by viruses, the eye can become pinkish red, with watery and mucus discharge. If an eye infection is not treated promptly, it can lead to ulceration, or even loss of sight.

Sometimes the eye can become red and swollen without having infected by micro-organisms. This is called inflammation. Inflammation is the eye’s response too any foreign object or reaction to the eye. The immune system will cause the eyes to become red, either the whole eye, or a section of the eye. White blood cells may move into the cornea, and cause a very small white cluster. If the inflammation is on the eye lids, the area will become red and swollen.

If you are unsure if you are having an eye infection or inflammation, you should seek your optometrist’s consult, or see an eye doctor as soon as possible.

Dry Eyes

Dry eyes are the most common condition experienced by contact lens wearers. As a contact lens contact a certain percentage of water, it may dehydrate when worn in a dry environment. When the lens is dry, it will draw water from the eye. Therefore, the wearer will feel that the eye is tired and dry. Blinking may help to alleviate the discomfort, but is not a definite solution.

By using contact lenses with lower water content may help reduce contact lens related dryness. Lower water content lenses contain less water, and therefore will not dehydrate so easily, and therefore less likely to draw water from the eye. Eye drops can help to lubricate the eyes and enhance the wetting of the eye. However, if dryness persists, your optometrist can prescribe you with special eye drops that can help the eye maintain its tears more efficiently.

Cornea Hypoxia (Lack of Oxygen)

When contact lenses are worn for long hours and many days through the week, the cornea can suffer from lack of oxygen. This lack of oxygen will cause the cells of the cornea to function inadequately and optimally. The cornea may become unhealthy and will start to become slightly cloudy. The body will then recognise that the eye is suffocating, and therefore, will induce inflammatory responses in the eye. The eye may become red.

Blood vessels will start to grow into the cornea in an attempt to supply the central cornea with oxygen. However, these new blood vessels are weak, and abnormal. Once they’ve grown into the central cornea, the cornea tissues surrounding the vessel will start to become hazy and eventually opaque. The blood vessels are also prone to leakage. When the new blood vessel growth (neovascularization) becomes very advance, blindness will ensue.

Glaucoma

Glaucoma is an eye disease whereby the retinal nerves in the eyes becomes damaged, resulting in reduced vision, and even blindness. The real cause of the glaucoma has not been found. But research points to the possibility of mechanical pressure against the nerves, thereby resulting in nerve damage. The mechanical pressure that is exerted on the retinal nerves is the intra-ocular pressure (IOP) caused by the increased fluid in the eye.

Types if Glaucoma

There are many different types of Glaucoma, some of which are related to other diseases. These are the common types of Glaucoma.

a.         Primary Open Angle Glaucoma (POAG)

This is the most common type of glaucoma, whereby there is damage in the optic nerve. The cup/disc ratio is abnormal, and there is abnormally high IOP of above 21 mmHg. There may be damage in the peripheral vision, which can be confirmed by performing a visual field analysis. The progression of POAG is slow, but with little symptoms. It is therefore important to have a Glaucoma Eye Screening annually. Glaucoma can silently damage the nerves in the eye, without the person knowing. Often, it may be already late when the disease is discovered, without significant vision already lost.

b.         Normal Tension Glaucoma (NTG)

In Normal Tension Glaucoma, the optic nerve in the eye gets damaged, manifesting abnormal cup/disc ratio and damages. Visual field anaylsis may also show some damage to peripheral vision. However in NTG, the IOP may remain within the normal range of below 21 mmHg. The cornea thickness will therefore determine if the cornea is thin, which may give a falsely low reading. If glaucoma damage does occur, treatment will be necessary with medications (eye drops) that will further reduce the IOP.

c.         Angle Closure Glaucoma (AACG)

This is a attack of drastically increased IOP. The IOP can be as high as 30 to 40 mmHg. AACG is caused by the iris protruding forward, sometimes due to cataracts, thereby obstructing outflow of fluid in the eye. This obstruction very quickly causes the build-up of fluid in the eye. This spike of IOP causes pain, redness of the eye, nausea, and blurry vision. This is considered to be an emergency and immediate treatment need to be sought. Medications will be needed to lower the IOP, and laser surgery will be required to facilitate the outflow of the fluid.
           
Diagnosis
           
The diagnosis of Glaucoma is by the damage of the optic nerve head. Damage to the optic nerve results in an abnormal depression of the central of the optic nerve head. This is called optic nerve “cupping”. The extent of the damage to the optic nerve in the eye is recorded as cup/disc ratio, and its associated damage by its appearance.

Usually, the IOP is high, and therefore the damage can be attributed to the increased IOP. An assessment of the peripheral vision will need to be performed. This is done by having the patient sit in front of a visual field analyser. The patient will need to keep his eye straight, while clicking a button whenever a light appears at other positions. Since damage of the nerve causes loss of peripheral vision, visual field analysis is an important tool to assess the extent of damage to the person’s vision.

With recent research suggesting that cornea thickness may have a role to play in the measurement of IOP, it is now important to measure the cornea thickness to aid in the diagnosis of glaucoma. Thicker cornea may cause a falsely higher IOP reading, while thinner cornea may give the impression of a falsely low IOP reading.

To treat Glaucoma, the eye doctor will prescribe medications most likely in the form of eye drops to lower the eye pressure, in the attempt to halt the progression of glaucoma damage by keeping the IOP way below the normal value of under 21 mmHg.

Age Related Macular Degeneration (ARMD)

ARMD is an eye disease that affects individuals that are above 50 years old. This disease is caused by the abnormal functioning of a particular tissue on the retina called the Retinal Pigmented Epithelium (RPE). The RPE deposits waste materials at its adjacent tissue called the Bruch membrane. This waste material that accumulates at the Bruch membrane is called drusen. The malfunctioning RPE starts to atrophy and die, which leads to reduced vision. Smoking and under-nutrition can contribute to the progression of ARMD.

ARMD exists in two form, Atropic and Exudative.

a.         In Atrophic, sections of the RPE die and cause an area of missing retinal cells. In this case, the amount of reduced vision depends on the severity of the atrophy.

b.         In Exudative, abnormal blood vessels starts to grow from underneath the Bruch membrane to supply oxygen to the diseased cells. However the blood vessels are weak and may start to leak. Leaking of blood into the internal eye can cause internal scarring and ultimately blindness. Prompt laser treatment is required to prevent the new blood vessels from leaking.

Diagnosis
           
ARMD can be screened by viewing an Amsler chart, to check if there is any distortion of vision that is being caused by damaged retina. The distortion is then recorded. By taking a photo of the macula, the progression (if any) of ARMD can be monitored. The progression of ARMD is slow, and hard to prevent. If leaky blood vessels develop, laser surgery is the only treatment to prevent the worsening of ARMD.

It is important to note that supplementary antioxidants of Vitamin C, E and Beta-carotene, zinc and lutein may help protect eyes with high risk drusen from developing ARMD.

Diabetes is a disease that is causes the body to not recognise the sugar intake through eating. The body therefore does not covert the sugar in the blood into glycogen for storage in the muscles and other parts of the body. While excessive sugar remains in the blood, this can cause the wall lining of the blood vessels to weaken and deteriorate. There are two types of diabetes.

Type 1 Diabetes is diagnosed earlier in life, in the early teens to twenties. It is caused by the body not being able to recognise the sugar in the body, as the cells that should recognise it has been damaged by the body’s own immune system. Therefore, the body does not produce insulin for the purpose of this conversion, and these individuals will need to inject insulin, to convert the sugar into glycogen for storage in the body.

Type 2 Diabetes is diagnosed later in life and is associated with systemic health problems such as obesity. In this case, the body grows less sensitive to the insulin that has been produced in the body, and very slowly, the body becomes immune to its own insulin. Therefore, blood sugar cannot be converted for storage, and remains in the blood stream.

The retina is the only tissue in the body to have exposed blood vessels that are viewable by the naked eye with the help of a special microscope. Therefore, the eye is the best place to monitor the extent of diabetes, as well as the damage caused by it. Since diabetes weakens the blood vessel walls, these blood vessels are prone to leaking. Thus, this causes diabetic retinopathy.

Diabetic eye disease is a group of diseases in the eye that is caused by diabetes. Abnormal changes in the eye can occur such as cataracts, glaucoma and diabetic retinopathy. Since the fluid in the body as well as the eye is imbalanced due to the abnormal sugar level, the cataracts can occur from this fluid imbalance. Glaucoma can also occur, as abnormal blood vessels can grow in areas when fluid drainage occurs.

Diabetic retinopathy has two categories. In Non-Proliferative Diabetic Retinopathy, the retinal blood vessels leak, and cause damage to surrounding retina tissues. The retina tissues suffer from lack of nutrients and oxygen supply due to the malfunctioning blood vessels. The retina therefore became unhealthy, and loss of vision may ensue.

When the condition becomes more serious, new blood vessels will grow in the retina. These new blood vessels are leaky and abnormal. This is called Proliferative Diabetic Retinopathy. The new blood vessels leak easily and cause serious haemorrhage inside the eye. Scarring can follow, and serious conditions such as glaucoma and retina detachment can also follow.

Hypertension and the Eye

Hypertension is also commonly known as high blood pressure. In this condition, there is resistance to the blood flowing in the blood vessels. The resistance is caused by fatty or calcium deposits that have attached onto the wall of the blood vessels. The passage in which blood flows through where deposits have formed up causes resistance to build up.

The heart senses that the blood supply at the end of the line is insufficient, as resistance has build up on some portion of the blood vessels. Therefore, the heart pumps harder in the attempt to push more blood through the vessels that have deposits on them. This vicious cycle leads to increasing blood pressure if deposits on the blood vessels continue to build up.

As the retina is the only place in the human body where blood vessels can be viewed directly without obstruction, the progression of hypertension can be viewed through the eye. In an eye with hypertension, the blood vessels will appear to be straighter than usual, shimmering, and pressing hard against other vessels.

Other changes can occur in the retina when the blood vessels do not perform optimally. When there is enough hypertensive change in the retina, oxygen supply is reduced, resulting in suffocation of the retina around it. The nerve fibre layer will thus become swollen and appear white. When the blood vessels start to weaken, drops of blood may leak out of the blood vessels and smudge onto the nerve fibres. They will appear to be like a “flame-shaped” haemorrhage.

Hypertension affects the retina, and causes it to become unhealthy. Therefore, vision can be affected. Severe hypertensive individuals may lose their sight due to the severe damage of the blood vessels and the retina. It is therefore important to check your eyes annually for any damage due to hypertension or other diseases. The extent and severity of hypertension can also be monitored through the eye.

Binocular Vision Dysfunction

Binocular Vision Dysfunction is a group of eye conditions that is characterised by the inability of the eyes to function comfortably to maintain good vision. It is often under-diagnosed, as most people who suffer from BV dysfunction are still able to lead a relatively normal life. Individuals who suffer symptoms will often not know that they are actually having BV dysfunctions, unless they undergo a thorough eye check.

Binocular Vision Dysfunction can be categorised into two main groups, that is Vergence, and Accommodation. Vergence is associated to the ability of the eyes to maintain alignment, as well as to move together in order to maintain single comfortable vision. Accommodation is the ability of the internal eye muscle to contract, and cause a change in the focusing of the crystalline lens, thereby achieving clear vision while reading.

Vergence Related Problems

If the muscles in one of the eyes are not strong enough, it may cause that eye to deviate outwards (towards the ear) or inwards (towards the nose) when that eye is tired, or when it is covered. An outward deviation while the eye is at rest is called exophoria. An inward deviation while the eye is at rest is called esophoria.

Generally, a lot of people have small amounts of either exophoria or esophoria. However, they do not suffer from any symptoms, and their eyes maintain straight and correct positions most, if not all of the time. A small group of people may suffer from headaches, blurry or double vision, tiredness after reading for a short period of time, and even nausea. This small group of people may not have enough muscle tone to maintain the eye’s correct alignment for very long.

If the muscle tone is not strong enough, and nothing is done to build up the muscle tone, one of the eyes may eventually turn away from its correct position, resulting in a condition called a tropia, or a squint. Vision therapy can help to build up the muscle tone, and help relief the symptoms and prevent the development of a tropia.

A person who just develops a squint may suffer from double vision, confusion, heachaches, eye fatigue, and nausea. A person who suffers from a squint since young do not suffer from most of the symptoms mentioned, as the brain has learnt to suppress (turn off) the image from the deviated eye. An outward constant deviation of one eye is called exoptropia, while an inward constant deviation of one eye is called esotropia. Treating tropias involve vision therapy, special prism glasses, or surgery.

Accommodation Related Problems

When the ciliary muscles inside the eyes do not function normally, poor focusing of the crystalline lens can result. For an individual below 40 years of age, the ciliary muscles will contract and the crystalline lens changes shape to focus the light back onto the retina. Conditions that affect the focusing of the crystalline lens include accommodative excess, accommodative infacility and accommodative insufficiency.

Accommodative Excess

This is a condition whereby the muscles are constantly in a exerted stated. This can be due to excessive near work causing over-exertion of the muscles, or the over-flexibility of the muscles. Therefore, the person may have trouble relaxing the eye. This can also result in a falsely higher short-sighted power. Only special medication eye drops can totally relax the muscles of the eye.

A person suffering from accommodative excess may find that the power varies from different eye checks, and frequent changing of spectacles. He/she may also suffer from blurry near vision and nausea. Although eye drops can relax the eye muscles, the eyes may sometimes still return to the over-exerted state after the effects wear off. Special exercises can help to train the eyes to learn relax and better control the eye muscles.

Accommodative Infacility

When the ciliary muscles inside the eye is not flexible enough to change shape quickly to accommodate from distance to near vision, a person may suffer from accommodative infacility. He/she may feel that after near reading, the transition towards distance vision takes a long time. It may be several seconds before the distance vision becomes clear, while it only takes a split second for a normal person to focus his vision from near to distance or vice versa.

A person who suffers from accommodative infacility may have difficulty performing copying tasks from a white board or projector. He/she may also suffer accommodative symptoms which include intermittent blurry vision, headaches and nausea. Vision therapy with exercises that trains the eye muscles to relax and accommodate, which will gradually aid the eyes to regain normal focusing flexibility.

Accommodative Insufficiency or Ill-Sustained Accommodation

For a person below 40 years of age, reading should not be a problem even with glasses. However, if the muscles inside the eye are not functioning optimally, and cannot exert to bring about accommodation to focus the light rays on the retina, the person may be suffering from accommodative insufficiency.

Individuals above 40 years old suffers from reading problem due to age related loss of flexibility of the muscles and crystalline lens in the eye. This is considered to be normal, and reading glasses will alleviate the problem. For younger individuals, accommodative insufficiency is abnormal as they should still have adequate flexibility of the muscles and the lens.

For a person who finds it hard to keep focus during reading, where the vision fades in and out from between clear and blurry vision. This happens when the muscles are unable to maintain its tone to stay fixed at the position of focus, thereby resulting in difficulty in maintaining focus.