Myopia (also known as near-/ short-sightedness) is most commonly caused by the length of the eyeball (i.e. visual axis) being longer than it should. As a result, the visual image is formed in front of the retina and causes blurry distant vision. Myopia can be corrected by using appropriate concave lenses to help the image focus back onto the retina.

Hyperopia (also known as far-/ long-sightedness) commonly occurs when the length of the eyeball being too short. Thus, the visual image would be formed behind the retina. If the hyperopic prescription is not too strong, our eyes can accommodate and focus the image on the retina without causing any blur. It is normal for children to have a mild degree of hyperopia, and as they grow, the eyeball will lengthen and the far-sightedness would gradually decrease. For children with over +3.00D of hyperopia, glasses are often required to relieve their stress when performing near tasks (e.g. reading, drawing, computer, etc).

Astigmatism is a condition caused by the uneven curvature of the cornea (i.e. the curvature is not spherical). Therefore, the image formed on the retina is blur and elongated. The blurriness would affect both distant and near vision, some may even experience double vision or headache. Astigmatism can occur in combination with hyperopia or myopia, and it can be treated with cylindrical lenses.

Near blur is a common symptom for people over the age of 40. Presbyopia is caused by the loss of elasticity of the crystalline lens and the loss of power of the ciliary muscles which apply forces on the lens. The deterioration generally stabilizes after the age of 60. Presbyopia can be corrected with single vision near point lenses, bifocal lenses or progressive addition lenses.

Amblyopia (also known as lazy eye) is characterized by poor sight clarity even with the aid of glasses. It normally affects one eye only and children with anisometropia (significant difference in refractive errors between the two eyes), strabismus or some congenital eye diseases are more likely to suffer from amblyopia. During visual development, if either eye cannot receive a clear retinal image or the image is being suppressed by the brain, the neural connection between that particular eye with the brain would be severely hindered. If detected early, amblyopia can be treated with appropriate prescription, eye patching and vision training.

Strabismus (squint) is caused by the misalignment of the two eyes. When one eye fixates on a target and the other eye turns inward, it is the internal/ convergent squint. On the other hand, when the eye turns outward, it would be the external/ divergent squint. The condition is often associated with refractive errors, congenital eye disease or unco-ordination of the extra-ocular muscles of the eyes. Depending on the nature of the squint, it can be treated with spectacles, vision therapy or surgery.

Color vision deficiencies are usually congenital disorders characterized by the inability to differentiate certain colors (most commonly, red and green confusion). This hereditary condition mainly affects male and there is no cure. Most of the affected group can name colors correctly, but the colors that they perceived are different from normal. When children are diagnosed with color vision defects, their teachers should be informed so that their educational instruction would not be color-coded. In addition, they should be aware that certain occupations are not suitable for them (e.g. pilot).

Glaucoma is a disease caused by the damage of retinal ganglion cells and the optic nerve. It results in vision loss and constriction of visual field. Although elderly people and those with high myopia are at higher risk, people of any age are susceptible to developing glaucoma. Glaucoma leads to the constriction of visual field from peripheral towards the central field, while an entire loss of visual field and blindness would be resulted eventually if untreated. Since symptoms are not noticeable to patients in the early stage of glaucoma, it is also nicknamed “sneak thief of sight”. For that reason, regular eye check-ups are essential for early detection and timely treatment.

Cataract is a condition which the intra-ocular lens turns hazy and reduced in transparency. The most common cause of cataract is due to ageing and the lens become cloudy and hardened. There are other causes including, trauma, drug induced, excessive exposure to ultra violet, general health problem or congenital causes. Blurry vision is the most prominent symptom of cataract. It also causes reduced contrast sensitivity (further reduction of sight clarity in dim area), change in color tone perceived and experience glare when viewing light sources. Individuals would experience different levels of symptoms depending on the type and nature of the cataract.

Macula is the central part of the retina with high density of photoreceptors. It is responsible for central and high acuity vision. The macula plays an important role in our daily activities such as reading, color discrimination, face recognition, writing, driving, cooking, etc. Age related macular degeneration begins with pigment changes around the macular region. For the more severe macula degeneration, it may involve abnormal growth of blood vessels, leakage of blood, scarring and edema. Early changes could have no obvious symptoms but as the condition progresses, it will cause blurry and distorted central vision and complete loss of central vision eventually if left untreated.

Retinal detachment is a disorder in which the retina is “pulled away” from its normal position. It is often caused by the thinning and degeneration of peripheral retina and as a result creating breaks, tears or holes on the retina. This results in loss of functions of the photoreceptor cells. People with high myopia (elongated eyeball), eye trauma, diabetes, tumor or inflammation are more prone to have retinal detachment. Common symptoms include increased number of floaters, light flashes and the loss of visual field. If there is a sudden dramatic increase of floaters, flashes of light, shimmering, or if the visual field appeared slanted/ distorted, patients should consult a specialist immediately. Retinal detachment can permanently damage patients’ visual functions. Prompt consultation and treatment are therefore necessary in order to prevent vision loss or blindness.

Dry eye syndrome refers to a series of problems caused by inadequate tear production or unstable tear film. Tears are produced by the lacrimal gland and have diverse functions such as retaining moisture, maintaining optical function of the eyes, providing oxygen to the cornea, washing out dust and debris from the eyes, as well as preventing infections. Patients may suffer from dry eye syndrome if they experience symptoms such as dryness, fatigue, redness, itchiness, burning, irritation, discomfort, difficulty in opening eyes, watery eyes, blurred vision, sensitivity to bright light, wind and smoke, etc. Delayed diagnosis may result in damage to the cornea or even irreversible vision impairment.

Conjunctivitis (also known as pink eye) refers to the inflammation of the conjunctiva. Conjunctiva is the mucous membrane covering the white part of the eyes and the inner surface of the eyelids. There are several causes of conjunctivitis (including bacteria, virus, allergy, etc) and the treatment will depend upon the cause. Symptoms of conjunctivitis include redness, swelling, burning and itchy sensation, increased discharge and watery eyes.

Computer Vision Syndrome refers to the eye and physical problems associated with the use of computers. Symptoms of Computer Vision Syndrome include eye tiredness and dryness, blurred vision, progression of refractive errors, diminishing ability to differentiate colors, eye redness, double vision, photophobia (sensitive to light), difficulty to sustain/ change focus, headache, sore neck and back pain, etc.