Prism Glasses in Detail
Diplopia, or double vision, is an ocular problem that causes significant difficulties in seeing clearly. Indeed, two images of the same object are transmitted to the brain, which cannot assemble them correctly. This occurs when the transmission of light to the retina is poorly ensured. Cataracts, corneal disorders, or astigmatism can, among other things, be the cause of this double vision. To remedy this, one can treat the cause or wear prism glasses.
Glasses that correct the problem
As with myopia or astigmatism, a pair of glasses can correct certain vision problems. In cases of double vision, prisms are then recommended.
These glasses are equipped with one or two lenses with a prism, a flat shape that plays a major role in deflecting light. The image sent to the brain will thus be normalized, allowing the brain to correctly associate the two sources to create a single image. This type of lens corrects vision divergences by helping the eyes work together, thus facilitating the integration of images by the brain.
The function of the prismatic lens
The prism is a major ally for seeing "normally" in cases of double vision and for correcting position and convergence problems. By modifying the entry of light into the eye, the lens reduces diplopia and allows the brain to correctly assemble the images sent simultaneously by each eye.
The prismatic lens therefore forces the brain to receive common information from both eyes, even if one or both pull to one side (up, down, left, right). This eliminates the impression of a double image.
In very damaged cases, surgery may be necessary to repair the ocular muscles.
The prism is made from two intersecting faces forming a specific angle that deflects light so that the image "falls" correctly on the retina. Double vision disappears because the message received by the brain is clear.
Other uses of prismatic lenses
In addition to correcting diplopia, these lenses are used to treat hemianopsia (partial blindness of the visual field) and quadrantanopia (quarter-field deficit). They also help nystagmus patients with slight torticollis by effectively blocking their eye tremors.
More recently, low-power prism glasses help dyslexic children suffering from stomatognathic dysperception syndrome by correcting ocular proprioception and improving spatial perception.
Glasses adapted to every need
The prescribed prism comes with numbers corresponding to the eye deviation and the necessary power.Prismatic correction is recommended when double vision has been stable for more than 6 months.
The ophthalmologist measures the deviation of the eyes during primary gaze (straight ahead) to determine the correction.
When these glasses are removed, double vision reappears, but wearing them is essential to reduce visual distortion.
How are prism glasses made?
After prescription, you will visit an optician who will create your prism glasses based on the measurements.The prism is placed or cut into the lens, at the targeted point depending on whether the deviation is horizontal, vertical, or mixed.
Low corrections are often placed on a single lens, while strong corrections are distributed over both eyes.
For correction for both distance and near vision, two specific lenses will be necessary to replace multifocals.
For high degrees of deviation, a Fresnel prism is used: two adhesive strips applied to the lenses, particularly useful after surgery to evaluate or compensate for temporary double vision.
Jampolski flexible prisms, which are more fragile, are used for short durations.
Which frame to choose for prism glasses?
These glasses require very precise adjustment. Monobloc metal frames are often recommended for their solidity and hold.
Highly curved frames are ideal for optimizing prismatic correction but may be less aesthetic. Indeed, the stronger the prism, the thicker the lens will be locally, hence the importance of a suitable frame to lighten the appearance.
Despite the precision of the prescription, several adjustments are necessary to optimize wear: dominant eye balancing, ocular paralyses, vertical components, etc.
It is essential to regularly check the prismatic compensation to reduce its power when the correction is effective and the brain receives light correctly.
Constraints and wearing follow-up
Wearing prism lenses requires regular follow-up, as the frames must remain well-adjusted to maintain correction and comfort.It is recommended to check tightness and centering at least every two weeks initially, then at least once a month.
These glasses must be worn continuously, from waking to sleeping, for optimal effect.
Professional advice
The choice of frame is crucial to maximize the utility of prismatic lenses.Do not hesitate to consult the healthcare professionals who follow you to choose a model adapted to the power and type of prism required.
