Sudden squint
It can happen in adolescence or adults that suddenly a form of squint associated with double vision (diplopia) develops. “The phenomenon of double vision – explains Andrea Piantanida, eye surgeon, Centro Oculistico Lariano, Cernobbio-Como and member of the scientific committee of Salmoiraghi & Viganò Foundation – is the main clinical condition that requires the use of prisms on glasses. The prism in fact superimposes the two images eliminating the double vision “. Prismatic lenses are not free from side effects, especially if they are of high diopters: sometimes it is necessary to use adhesive prisms of plastic material, instead of glass, especially for very large squint angles in order to reduce the thickness and weight of the prismatic glasses and make the use of these lenses more tolerable. “The use of adhesive prisms, continues Piantanida, is limited in time: in fact, these lenses are generally used pending the definitive prescription or surgery, aimed at eliminating double vision”.
When the squint is latent
But squint is not always evident when observing the patient. Sometimes it can be present if stimulated by certain situations of everyday life. “For example, – explains Piantanida – some forms of squint can occur in case of visual fatigue due to prolonged use of videos or due to glare phenomena, for example with the light present on strong sunny days, or even due to a visual commitment of maximum concentration as happens to those who work on microcircuits. Such patients sometimes report a true double vision which makes it impossible to work “. “The use of prisms – continues the ophthalmologist – allows you to restore single binocular vision, relieve symptoms and follow the patient over time until the clinical picture is stabilized”.
The position of the head
As people who, not seeing clearly from a distance, get as close as possible to the object to be observed are well aware, the abnormal positions of the head represent the compensation mechanisms that the patient puts in place to eliminate double vision. “In adults they are almost always an expression of ocular paralysis, while in the pediatric age they are often associated with particular clinical situations, first of all congenital nystagmus”, continues the ophthalmologist. In both situations, the prismatic lenses have the purpose of restoring single binocular vision to allow the patient the correct position of the head without deviations. After a period of adaptation to the prismatic correction, the patient will be re-examined, to evaluate the surgical possibilities to definitively restore the correct posture. “Prismatic lenses, concludes Piantanida, must therefore be interpreted as aids to temporarily resolve double vision or postural abnormalities of the patient’s head while waiting for surgery”.