When the lens of the eye is clouded with protein lumps, it forms a smoky screen called a cataract. A cataract tends to grow larger over time and cloud most of the eye's natural lens. Due to the cloudiness, the lens is not able to transmit clear pictures to the retina and vision is affected. Age-related cataracts are the most common type of cataracts that are observed. A nuclear cataract is formed in the center of the lens and is part of the natural aging process. A cortical cataract develops in the lens cortex and gradually extends towards the lens. This is noticed largely among patients suffering from diabetes. They are also likely to develop subcapsular cataract that forms at the back of the lens. Some babies are born with congenital cataracts. Secondary cataract develops as a result of diabetes or other diseases or medications. Cataract does not spread from one eye to the other and does not cause permanent blindness.
A person suffering from cataract will notice slightly blurred vision. Most of the symptoms of cataract depend on the type of cataract that has occurred. While a patient suffering from subcapsular cataract may not notice any symptoms, a nuclear cataract can give rise to a temporary improvement in vision followed by worsened condition. Symptoms associated with cataract are blurred vision, light sensitivity and poor night vision. The cloudiness over the lens depends on the amount of cataract and its location. If it is near the center of the lens, vision is badly affected. A patient suffering from cataract may not be able to notice colors brightly and may complain of double vision.
Cataract surgery is the only treatment for cataracts. It has a high success rate in restoring good vision to cataract patients. Ophthalmologists are of the opinion that long-term unprotected exposure to sunlight's UV rays may be a cause for formation of cataracts. Other risk factors include cigarette smoke and air pollution. Eating a diet high in antioxidants, vitamins C and E may play a role in keeping cataracts at bay.
An ophthalmoscope is used to examine the retina and vitreous. Ophthalmoscopy aids visualization of the inside of the back of the eye including the retina, optic disc, choroid and blood vessels. It is often part of a routine eye examination. A direct ophthalmoscope is used for viewing the central retina. It is hand-held and powered with a light source. The instrument has to be adjusted constantly to focus on different structures within the eye. The light can be intense and disturbing. An indirect ophthalmoscope aids in examining the entire retina. This instrument is attached to the doctor's head and allows a clear view of the retina with a special lens. The patient may feel uncomfortable due to the intense light and pressure from the instrument.
Ophthalmoscopy is useful in detecting any changes in the retina due to diseases such as eye disease, diabetes, arteriosclerosis, high blood pressure or macular degeneration. Cataracts and other eye problems can be detected with an ophthalmoscope.
The patient's eyes are dilated so as to allow a good view of the insides of the eye. Some patients develop allergic reaction, vomiting, nausea and dizziness. This test is conducted in a darkened room where the patient is asked to look ahead at a distant spot. The eyes must be held steady without blinking. The ophthalmoscopy procedure may take just about 5 - 10 minutes.
Diplopia is one of the serious disorders of the eyes, which is associated with vision impairment. In common terms it is referred to as double vision. The occurrence of diplopia is closely associated with the cranial nerves. The effects caused by this optical disorder restrict normal activities of a person such as reading, walking and driving. The causes associated with diplopia when closely examined are myogenic and neurogenic in origin leading to an optical disruption both of vision and movement of the eyes.
Clinical manifestations and classification
Diplopia can be monocular or binocular in origin. Monocular Diplopia has preexisting-associated conditions such as cataracts, luxation of the lens and keratoconus, which results in light refraction within the eye. Macular degeneration and vitreous damage also causes light refraction retention inside eye causing blurred vision.
Binocular diplopia is caused by neurogenic impairments related to Oculomotor nerve damage, which is an important nerve in facilitating the movement of eye. The muscles associated with the respective functionality are also damaged in this condition. In most cases binocular diplopia is caused because of head injuries leading to cranial damage or traumas caused to the eyes. In some cases aniseikonia (condition which results in difference in the size of images as seen by the person) is also a predominant factor leading to binocular diplopia.
Diplopia occurrence and its respective effects can be further classified as sustained and short-lived forms. Intermittent or short-lived forms are usually a postoperative sequel especially in the case of cataract surgeries. However, diplopia of both continued and short-lived forms predominantly depend upon the thyroid hormone levels and underlying medical conditions such as myasthenia gravis.
Diagnosis of diplopia is a chronological aspect consisting of various factors. A patient complaining of blurred vision has to undergo series of medical and diagnostic investigations to rule out false positive findings. Since diplopia is associated with cranial nerves predominantly the oculomotor nerve, a gaze test is administered by the optometrist to estimate the functionality of nine cardinal vision factors.
This is prior to examining the patient history thoroughly in checking for conditions such as diabetes and hyperthyroidism. Important optometric examinations such as prism test, Bilshowsky test, Stereo acuity test and visual field testing are done to evaluate the impairments existing in the muscles associated with the eye. These tests are carried out after general examinations such as tonometry, fundoscopy and slit lamp examinations.
Corrective measures are incorporated to treat the movements of the eye, which is affected drastically in this condition. Refraction errors are analyzed and corrected in order to rectify the blurred vision. Patients are given eye exercises to facilitate proper oculomotor nerve functionalities and also to prevent squint occurrence.
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Bibliography / Reference
Collection of Pages - Last revised Date: December 1, 2020