Binocular vision disorders and prismatic correction.
Binocular vision disorder is a disorder in which the eyes cannot work together properly to form a single image. Normally, both eyes are directed at the same object, and the brain combines the two images into one clear image. If this process is disrupted, a person may experience double vision, blurred vision, problems judging distances, or loss of spatial perception.
Causes of binocular vision impairment
1. Strabismus is a condition in which the eyes cannot focus on one object at the same time due to the displacement of one eye to the side.
2. Anisometropia is a different power of refraction in the eyes, due to which they have different focal lengths.
3. Amblyopia ("lazy eye") is a decrease in vision in one eye, in which the brain ignores the image coming from that eye.
4. Neurological and traumatic disorders — brain injuries, strokes, neurological diseases can also affect binocular vision.
5. Eye diseases - some diseases (cataract, retinal pathologies) can cause a blurred image in one eye.
Symptoms
• Double vision (diplopia)
• Loss of depth and spatial perception
The mechanism of binocular vision
Binocular vision ensures the coordinated work of both eyes, where each eye forms a slightly different image, but the brain connects them into one three-dimensional (stereoscopic) image. This allows us to feel depth and correctly estimate the distance to objects. Binocular vision impairment means that the images from each eye do not connect properly, which can lead to bifurcation (diplopia), instability of the image, or its blurring.
Types of binocular vision disorders
1. Phoria and tropia — types of strabismus:
Phorias (hidden strabismus) is manifested only when one eye is closed, and in the open state the vision remains normal.
Troopias are clear forms of strabismus, where the deviation of one of the eyes is permanent and noticeable.
2. Accommodative and non-accommodative strabismus — depending on whether the strabismus can be corrected with glasses.
3. Intermittent strabismus — occurs periodically, for example, during fatigue or stress.
4. Vergence disorders — problems with coordination of convergence and divergence (focusing the eyes on objects of different distances).
Causes of binocular vision disorders
• Genetic factors: some binocular vision disorders, such as strabismus, can be hereditary.
• Refractive abnormalities: for example, farsightedness (hypermetropia) often causes the development of accommodative strabismus.
• Oculomotor muscle dysfunction: weakness or dysfunction of the muscles that control eye movement.
• Injuries: Brain damage or eye injuries can cause binocular vision impairment.
• Diseases of the nervous system: for example, multiple sclerosis, stroke, or tumors that disrupt the work of the oculomotor nerves.
Treatment of binocular vision disorders
1. Optical correction — use of glasses or contact lenses to correct refractive errors.
2. Prismatic glasses are lenses that change the direction of light rays and help the eyes to work harmoniously.
3. Orthoptic exercises — special exercises that train the oculomotor muscles and improve the coordinated work of the eyes.
4. Occlusion therapy — temporary closure of the healthy eye to train the weaker eye (used in amblyopia).
5. Surgery — in severe cases, surgery may be required to correct the muscles that control eye movement.
6. Neuroimaging — vision restoration techniques using special brain training programs.
Prevention
• Regular eye examinations, especially in children, for early detection of disorders.
• Eye exercises and eye strain: take regular breaks while working at the computer.
• Avoiding eye and head injuries, using protective glasses during activities that pose a risk of injury.
Correct diagnosis of binocular vision impairment is possible only after a comprehensive examination by an ophthalmologist or orthoptist, who will develop an individual treatment plan.
Prismatic vision correction
Prismatic vision correction is a method of correcting binocular vision disorders, in which special prismatic lenses are used. These lenses have a wedge shape that changes the direction of light rays, helping the eyes to focus on one object. Prismatic correction is useful for people who suffer from diplopia (double vision), strabismus, some types of amblyopia, and other binocular vision disorders that cause difficulty with coordinated eye work.
Principle of operation of prismatic lenses
Prismatic lenses refract light rays so that they are directed in the right direction for each eye. This helps avoid double vision and reduces the need for the eyes to constantly compensate for deviations. The lens directs the rays so that they enter the central visual area of each eye, contributing to the formation of a clear and unified image in the brain.
Who is prismatic correction indicated?
1. People with strabismus (especially with the latent form — phorias), whose eyes naturally deviate to the side, but they compensate for this with muscle tension.
2. Patients with diplopia, a condition in which the image doubles, in particular as a result of a stroke or brain injury.
3. People with vergence disorders — difficulties with focusing the eyes on objects at different distances, which can occur with visual fatigue or asthenopia (visual overstrain).
4. With certain forms of amblyopia, when one eye is "lazy" and the brain does not perceive the image from it properly.
Types of prismatic lenses
Prismatic lenses can be made in different shapes and with different optical powers depending on the type and degree of the disorder. There are two main types:
• Fresnel prisms are overlay prismatic films that are easily attached to ordinary eyeglass lenses and can be replaced.
• Permanent prism lenses — built into the very structure of the glasses, more aesthetic, but designed for long-term use.
Advantages and disadvantages of prismatic correction
Advantages:
• Alleviation of diplopia symptoms and reduction of eye strain.
• Improvement of visual comfort.
• Normalization of spatial perception and coordination of movements.
Disadvantages:
• Prismatic lenses can distort the image, resulting in some distortion of objects.
• There may be a need for gradual adaptation as the brain needs to get used to the new visual conditions.
• High price, especially in the case of specialized or custom-made lenses.
The process of selecting a prismatic correction
Prismatic lenses are selected by an ophthalmologist or optometrist after a comprehensive examination, which includes checking binocular function, measuring eye deviations, and checking for diplopia. It is important to gradually increase the prismatic power to adapt the patient and ensure the most comfortable vision.
Prismatic vision correction can significantly improve the quality of life of patients with binocular vision disorders, helping them get rid of symptoms of discomfort and increasing visual stability.