Information on the most common
visual defects and eye conditions.


When all parts of the visual system are working normally, the eyes can move together, adapt to light and dark, perceive colour and delineate shapes and objects and the distances between them. Of course, not all eyes are the same, and there is a range of conditions that can affect them.

This is a refractive defect of the eye in which the eyeball is either too long or the cornea and crystalline lens power are too strong, causing light rays to focus in front of the retina. This can be corrected with concave, diverging or minus (-) lenses.

This is a refractive defect of the eye in which the eyeball is too short or the cornea and crystalline lens power is too weak, causing light rays to focus beyond the retina. This can be corrected with convex, converging or plus (+) lenses.

It occurs when the front of the eye, the cornea, has an uneven curvature. Instead of being spherical, it is egg-shaped. When light hits an irregularly curved cornea, the light is not focused correctly onto the retina. Instead, the incorrect focus blurs the image, resulting in blurred vision.This defect can be corrected with a cylindrical lens with two powers positioned at 90 degrees to each other. This lens allows the light to correctly focus on the retina. In many cases of astigmatism the eye can also be myopic, hyperopic or presbyopic.

This is a visual condition in which the crystalline lens of the eye becomes stiffer and loses its ability to focus on close objects. The condition usually becomes noticeable in the early to mid-forties and it is a part of the normal ageing process of the eye. Presbyopia is not a disease and it cannot be prevented, but it can be corrected with reading spectacles, bifocals or progressive lenses.


A cataract is a clouding of the natural lens in the human eye. Typically, it occurs as a result of the normal ageing process of the eye. However, on occasion, it can occur in the younger person in association with another medical condition such as inflammation in the eye or diabetes. The presence of a cataract is not harmful, and treatment may not be needed early on. However, as a cataract progresses it may affect the quality of your vision. In this instance, we would refer you on to an eye specialist (Ophthalmologist). If needed, cataracts can be treated surgically, under local anaesthetic and as a day case procedure. Your ophthalmologist will advise if this is required.

Glaucoma is a term that describes a number of conditions that cause damage of the optic nerve and affect vision. It is typically seen in people over the age of 45. It occurs when the fluid in the eye builds up and adds increased pressure on the optic nerve. Over time, this causes damage to the nerve at the back of the eye and as a result affects the eye’s visual field. Glaucoma can also occur because of a weakness of the optic nerve itself, due to a poor blood supply, or because of some other type of weakness of the nerve. The condition can present itself in two ways. In the acute form (which is rare), it is manifested as a painful, red eye with reduced vision, but in the more common, chronic from, a patient may not be aware that they have the condition. In this instance, the presence of glaucoma may only be detected during a routine eye examination, by examining the optic nerve, by measuring intraocular pressure and through the analysis of the visual field test. All of these tests are routinely performed and analysed during an eye examination at Mallon+Taub.

The chronic form of glaucoma is slowly progressive causing irreversible damage to the visual field. However, if detected early many cases of glaucoma are treatable under the care of an eye specialist. Eye drops are commonly used to lower the eye pressure. They are generally very effective in reducing the eye pressure and keeping it stable. There are many types of eye drops available and your ophthalmologist will be able to help you choose the right type of drops for you. Once the pressure is controlled, further damage to the eye and visual field is usually prevented. In a small number of cases, a routine laser surgery may be needed to control the glaucoma.

Diabetes is a common medical condition affecting over 2.3 million people in the UK. Diabetes, if poorly controlled, can cause damage to the delicate blood vessels that supply the lining at the back of the eye (the retina). However, if detected early, diabetic eye changes can be monitored and treated by an eye specialist thereby reducing the damage caused to the retina and preserving vision. Having regular eye examinations is the best way to detect early signs of diabetic eye. At Mallon+Taub our Optomap Retinal Imaging System can help detect early signs of diabetes. If necessary, our optometrist will refer you to your GP or an eye specialist for further examination and treatment.

Age-related macular degeneration (AMD) is a common condition that affects many people, particularly over the age of 65. AMD is a condition that affects the macula area, a small part of the retina at the back of the eye. This area contains specialised cells important in the processing of light. Damage to these cells causes distortion of central vision and in some cases can cause a painless loss of central vision. There are two main types of AMD: “dry” and “wet”.

Dry AMD is the more common type. It develops very slowly and causes a gradual change in central vision. In more severe cases, dry AMD causes a blank patch in the centre of your vision in both eyes. It doesn’t affect the peripheral vision and it does not lead to complete blindness.

Wet AMD develops more rapidly, so it impacts central vision in a shorter time. Neither type of AMD will cause the loss of peripheral vision and blindness.

During a routine eye examination at Mallon+Taub, the optometrist will thoroughly examine your macula. If any changes are detected, we will refer you to the appropriate eye specialist who will give you further advice and treatment.

Many studies suggest that exposure to high levels of UV light in sunlight throughout your life could increase your risk of developing AMD. Protecting eyes from sunlight by wearing sunglasses is recommended for everyone throughout their life. At Mallon+Taub we specialize in prescription and non-prescription sunglasses.

Blepharitis is an inflammation of the eyelid margins. Many patients do not display symptoms of eyelid inflammation, but instead experience irritation, foreign body sensation and burning of the eyes. Typically, symptoms are worse in the morning, but can occur at any time of the day.

It is a common condition but harmless to vision. It is often characterised by redness, crusting and itching of the eyelid margin. The inflammation of the lid margin may affect the numerous oil glands that line the eyelid margin. This can result in distortion of the tear film and dry eye. It can also sometimes result in the formation of cysts on the eyelid margin. Blepharitis is treated symptomatically. Drops can be given to help lubricate the ocular surface and treat the dry eye symptom. However, eyelid-cleaning techniques are often advised to help keep crusts and inflammation to a minimum.

Dry eye is normally treated with a particular type of eye drops known as “artificial tears”. They supplement natural tears and make the eyes feel more comfortable. This type of eye drops does not contain any drugs and it can generally be used as frequently and for as long as needed. At Mallon+Taub we have a selection of eye drops and eyelid hygiene wipes for blepharitis and dry eye.


There are two 24-hour NHS eye emergency services in London. Contact details are given below.

The Western Eye Hospital
153-173 Marylebone Road
London NW1 5QH
Telephone: 020 3312 6666
Nearest underground station: Marylebone or Baker Street

Moorfields Eye Hospital
162 City Road
London EC1V 2PD
Telephone: 020 7253 3411
Nearest underground station: Old Street