Diplopia by Laura Taylor

DIPLOPIA DIPLOPIA DIPLOPIA

Diplopia

Double vision is where the eyes see two images but of a one single object either on top of the other, side by side or sometimes even a mixture of both. The image above has been created by layering together sheets of tracing paper to represent this double vision misalignment. The photographs within this newspaper are personal to me - showing my mother and aunty who are both twins - showing a double meaning when it comes to visions.

Diplopia

VISION DOUBLE VISION DOUBLE Double vision, also medically known as Diplopia, is where you

see two images of a single object. The two images may be one on top of the other, side by side or a mix of both. The underlying cause of double vision depends on whether your double vision is coming from one eye or both eyes. Each eye creates its own, yet slightly different image and this is because the two eyes are physically located in different positions. However, you usually only see one image. This is because the brain is able to control the eye muscles so that both eyes are pointing accurately at the object you are focusing on. The brain joins the images produced by each eye together into a single image, in a process known as fusion. If the eye muscles or nerves are damaged, the muscles may not be able to control the eyes properly and this can lead to double vision. Double vision in one eye is known as monocular double vision. With this, you should be able to see normally if the affected eye is covered. In cases of monocular double vision, the two images are often only slightly separated. This can sometimes be referred to as ‘ghosting’. Double vision in both eyes is known as binocular double vision. It happens when both eyes fail to work together properly. If you have binocular double vision, your vision will usually return to normal if either eye is covered.

Diplopia

BINOCULAR DIPLOPIA BINOCULAR Binocular diplopia is a type of double vision that arises as

a result of the misalignment of the two eyes which are relative to each other. In cases where the fovea of one eye is directed at a particular object, the fovea of the other is directed elsewhere. The brain calculates the visual direction of an object based upon the position of its image relative to the fovea. Images falling on the fovea are seen as being directly ahead, whilst those falling on the retina outside of the fovea, may be seen as above, below, right, left or straight ahead. This depends upon the area of retina stimulated. However, when the eyes are misaligned, the brain will perceive two images of one target object, therefore producing double vision. The brain naturally guards against double vision. In an attempt to avoid double vision, the brain can sometimes ignore the image from one eye; a process known as suppression. The ability to suppress is found particularly in childhood when the brain is still developing. While this ability to suppress might seem an entirely positive adaptation to binocular diplopia, in the developing child this can prevent the proper development of vision in the affected eye resulting in amblyopia, also known as lazy eye. Some adults are also able to suppress their diplopia, but their suppression is rarely as deep or as effective and this takes longer to establish. In some cases, diplopia disappears without any medical intervention, but in other cases, the cause of double vision may still be present.

DIPLOPIA

Diplopia

Binocular diplopia is a result of the misalignment of the two eyes which are relative to each other. The eyes can often be found directed in different directions - above, below, right, left or straight ahead. The photograph above has been made to show this particular condition whereby the brain can perceive two images of one target image. The example has been layered together digitally to create an offset double vision effect.

Diplopia

Even when you only see one image, each eye creates its own, slightly different version and this is because of the location of the two eyes. The brain is able to control the eye muscles so that both eyes are pointing accurately at the object. The brain joins the images together in a process called fusion. However this isnâ&#x20AC;&#x2122;t always the case, which can cause problems for particular individuals, namely binocular, monocular, physiological diplopia and megalopia.

Diplopia

Monocular diplopia is a rare condition whereby two images of a single object are perceived within one eye only. In cases where the patient perceives more than two images, it is referred to as monocular polyopia. This can be down to a variety of conditions including the corneal surface, subluxation of the lens or structural defects within the eye itself.

Diplopia

MONOCULAR DIPLOPIA MONOCULAR DIPLOPIA MONOCULAR DIPLOPIA Monocular diplopia is the perception by one eye of two

images of a single object. This type of diplopia may occur when there are abnormalities in a cornea that is distorted or scarred, multiple openings in the iris, cataract or subluxation of the natural lens. It is also known as uniocular diplopia. Monocular diplopia needs to be distinguished from a condition known as Metamorphopsia. This is also a type of distorted vision, however it gives the illusion that objects appear to be misshapen. A refractive error is probably one of the most common causes of monocular diplopia, and looking through a pinhole should abolish the double vision. This is a strong indication that the patient needs refractive correction with spectacles. A developing cataract can cause monocular diplopia because areas of differing refractive index within the lens result in disruption of the light reaching the retina, and diplopia results. As the cataract becomes denser and less light gets through, the diplopia improves or resolves. Corneal scarring can have a similar effect. Issues with the cornea can often cause diplopia in one eye. Scarring can lead to unequal visual images. The abnormal surface of the eye distorts incoming light, which causes double vision, however, covering the affected eye makes this go away.

Diplopia

Monocular diplopia occurs in one eye only, yet two images of a single object are perceived. The photographs above have been printed on acetate and scanned to recreate a grainy effect to represent this rare condition. The left hand side image has been doubled and blurred to show how it can affect the patient - in one eye only.

Diplopia

DIPLOPIA PHYSIOLOGICAL DIPLOPIA PHYSIOLOGICAL Physiological diplopia is a normal phenomenon whereby

objects not within the area of fixation are seen as double. This is most common with background objects, for example, where they appear doubled. It is not an abnormal condition, it is just a sign that the eyes are working correctly. This vision problem usually goes unnoticed because the patient’s brain can usually compensate for this type of double vision. However, children who complain of having diplopia sometimes have physiological double vision. When someone with normal vision focuses on an object, everything in front of the object appears double, and everything behind the object appears double. This usually goes unnoticed by most people, unless their attention is brought to it. Physiological diplopia differs from pathological diplopia. Pathological diplopia is a condition that results from an abnormality in the visual system, such as strabismus. When someone with strabismus complains of double vision, it’s generally because their eyes are misaligned and pointing in different directions. If you have strabismus, then you don’t have physiological diplopia. It takes two eyes pointing at the same object whilst not suppressing to get physiological diplopia. For strabismic, developing the ability to achieve and notice physiological diplopia is a great thing. Why? Because physiological diplopia is an excellent way to determine if the patient is using both eyes, as well as seeing if they are both pointing in the same direction.

Diplopia

Physiological diplopia is a common diagnosis as it involves objects not within the area of fixation - mainly background objects to appear as double, mostly like that of a day dreaming state. As it goes unnoticed, the background of this photograph has been given a double vision effect to show how subtle the change can be.

Diplopia

Megalopia is a visual defect in which objects appear larger than their actual size, leaving the original subject feeling smaller than it actually is. The image above has been duplicated and re-scaled to represent this defect.

Diplopia

MEGALOPIA MEGALOPIA

Megalopia, also known as Macropsia, is a neurological

condition which affects human visual perception whereby the visual field appears larger than normal. This then causes the subject to feel smaller than it actually is. Megalopia can be caused by a number of factors which can include prescription and illicit drugs, migraines, to epilepsy and different retinal conditions, such as epiretinal membrane. Physiologically, retinal macropsia results from the compression of cones in the eye. It is the compression of receptor distribution that results in greater stimulation, therefore a larger perceived image of a particular object. A person suffering macropsia may experience a broad range of psychological and emotional effects. One theory had stated that macropsia may even be a psychological pathological phenomenon without any definite cause. It has been said that psychological conditions can often arise from macropsia, however the general consensus is that they do not cause macropsia. Those affected by this, may experience anxiety both during and after episodes as a results of the overwhelming nature of his or her distorted visual field. Those who suffer from the condition and have previously suffered from an episode, hesitate to recount the episode, however can retain the ability to do so, this is due to the fear and anxiety associated with the condition.