Sight problems illustrated

Many people are often confused by the different sight problems and what they mean. I have found that the best way to explain the common sight problems is via illustrations. Physicians often use these illustrations when they first begin to study about these sight problems. Normal and clear vision is shown below. Physicians use an Amsler grid, which helps to monitor central vision disturbances and distortions. People with normal vision see a perfect grid.

Macular Degeneration
Macular degeneration causes abnormal central vision and causes a central blind spot.

Cataracts
Cataract is a natural progression of the natural lens becoming more yellow and can cause glares, halos around light, and dimmer color vision.

There are three typical types of cataract found in adults:

• Nuclear sclerotic cataract – central part of the lens becoming more yellowing, which blurs the vision and can disturb the color vision.

• Cortical cataract – wedge shaped hazes present usually at the periphery of the lens surface, which causes certain parts of the vision to be blurry, and can create glare problems.

• Posterior subcapsular cataract - the back surface of the lens is cloudy, which can cause severe glare problems and significant reading difficulties.

Visual Migraine
Visual migraine is caused by disturbances of the blood flow to the visual cortex. The visual symptoms usually last from 20 to 40 minutes with or without headache. The symptoms can be perceived in several ways:

• A small blind spot appears in the central vision with a shimmering, zig-zag light inside of it. This enlarges, and moves to one side or the other of the vision, over a 20 to 30 minute period. When it is large, this crescent shaped blind spot containing this brightly flashing across the field of vision.
• Blurred vision of a field of vision lasts around 30 minutes.
• Things are either perceived smaller or larger than usual and the duration is of 30 minutes.

Peripheral visual loss
Peripheral vision loss can be caused by several mechanisms: advanced glaucoma, stroke affecting visual pathway, stroke of the optic nerves, and pituitary tumor.

Clear image with normal eye condition

Central vision is blurred and the horizontal line is cut through. This can be caused by severe glaucoma or stroke of the optic nerve.

Severe tunnel vision is caused by advanced glaucoma or retinitis pigmentosa.

Top half of the vision is affected and caused by a stroke of the optic nerve.

Right side hemi-field defect is caused by a lesion on the visual pathway within the brain.

Bilateral hemi-field defect is caused by lesion (usually a pituitary tumor) affecting the chiasm (part of the visual pathway)