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Sight Difficulties





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Myopia is an optical condition where the converging point of refracted parallel rays of light is placed in front of the retina and hence the image isn't focused on the retina. Instead, the retina receives the rays that exit the converging point, making the image appear blurry. This makes it easier to understand why individuals affected by myopia squint their eyes; doing so brings the parallel rays closer, which in turn brings their convergence point closer to the retina, making the image clearer.
Myopia may manifest in 3 degrees:
1. Low - up to 3D
2. Moderate - up to 6D
3. High (sometimes called high-progressive) - over 6D (may rise to 20D-30D)

Clinical signs
Affected individuals are unable to see from afar, so they tend to keep objects close to their eyes, thus keeping the inner straight muscles strained. Over time, this causes muscular asthenopia, which is a typical clinical picture and causes mild headache and blurred vision. For stretched periods of time, the headache may become severe and other symptoms may show up like nausea and dizziness.
Generally speaking, the myopic eye is bigger, with a deeper anterior chamber and more bulging outwards than it would normally be and has dilated pupils, while high myopia has a more specific clinical picture:
1. The first sign of high myopia is the manifestation of myopic cone in the optic papilla.
2. Enlargement of the eye on the posterior pole (staphyloma posticum) which causes degradation of choroid which in turn causes hemorrhaging in this area.
3. After the drainage of the hemorrhages, a hyperpigmented stain remains in the macular region (Fuchs' dystrophy).
4. The intertwining of blood vessels in the choroid is clearly visible.
5. Retinal degradation is detected in peripheral retina which causes retinal detachment.
6. Degenerative by-products and hemorrhaging causes lens opacification.
Myopia is treated with the following methods:
1. Glasses (concave lenses).
2. Contact lens (concave lenses).
3. Laser surgery (keratotomy or refractive keratotomy is executed by reducing the corneal curvature).
Hypermetropia is a refractive anomaly where the image is focused behind the retina. It may result from diseases originating from behind the eye which cause the lens to shift forward (orbital tumors, central serous retinopathy, tumors inside the eye, etc.). The hypermetropic eye focuses the image through the continuous process of accommodation. Accommodation in hypermetropia starts from seeing objects from afar and reaches its maximum with nearby objects.
Clinical signs
Generally speaking, the eye is smaller, the cornea is flatter, the anterior chamber is shallower and the pupil is more constricted than a normal eye. The blood vessels' reflection is also more visible and the optic papilla looks smaller, sometimes with an opaque outline (pseudoedema). If the eyes are strained for a long time, accommodative asthenopia manifests, which is caused by straining the ciliary muscle. Other symptoms are blurred vision and headache which gradually increases in severity.
Hypermetropia may manifest in 3 degrees:
1. Low - up to 3D
2. Moderate - up to 6D
3. High - over 6D
Hypermetropia can be treated by wearing glasses with convex lenses until the accommodation of eye fully compensates the anomaly. Until then, depending on the severity of this condition, glasses may have to be kept on at all times or only when the eyes are strained and the aforementioned symptoms manifest. Contact lenses, with the same indications, may be used and laser surgery (especially in cases with high hypermetropia) may be performed.
Astigmatism is a refractive condition of the eye where the refractive index is not the same throughout the corneal meridians. Therefore the image doesn't focus on a single point (stigma) in the retina as it would in a healthy eye; rather, the image focuses on different points.
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