[en] Phoria adaptation is a central tonal mechanism that stabilises binocular alignment to orthophoria in response to prolonged fixation and constant visual demand. Phoria adaptation has the optometric purpose of measuring ocular muscle balance and the ability of the visual system to maintain alignment. This mechanism alleviates visual fatigue, headaches and various ocular symptomatology. In the measured study, adaptation to phoria is estimated to take about 7 minutes using sustained binocular vision. The measurement is made with a 6 Δ prism superimposed on one of the two eyes, using binocular fixation, initially with a nasal base and then with a temporal base. The aim of the study is to predict whether subjects adapt to prism-induced heterophoria by reducing the adaptation period from 7 to 3 minutes, in adult patients. Such patients, with normal binocular vision, are used to adapt quickly. The study was conducted in a total of 32 adult participants, excluding binocular vision abnormalities; age range 18-24 years. The ocular adaptation coefficients of convergence (BT) and divergence (BN) were compared. The sample of participants was divided into those who showed a change of more than 1Δ/min during the 3-minute test and those who did not changed. Based on the results obtained at the end of the study, it can be concluded that 3 minutes are sufficient to guarantee phoria adaptation, provided that there is no pathology or binocular problem and, therefore, the expected results can be obtained. This test can be considered valid to conclude a diagnosis during daily optometric practice with adult patients with stable binocular vision.

[es] La adaptación de foria es un mecanismo tonal central que estabiliza el alineamiento binocular hacia la ortoforia como respuesta a una fijación prolongada o una constante demanda visual. La adaptación de fória tiene como propósito optométrico medir el equilibrio muscular ocular y la capacidad del sistema visual para mantener la alineación. Con este mecanismo se aligera la fatiga visual, las cefaleas y diversa sintomatología ocular. En el estudio, se estima una adaptación a la foria de 7 minutos con visión binocular sostenida y la medida se realiza con un prisma de 6 Δ sobrepuesto en uno de los dos ojos, con fijación binocular, inicialmente con base nasal y después con base temporal. El objetivo del estudio es predecir si los sujetos se adaptan a las heteroforias inducidas por el prisma reduciendo el periodo de adaptación de 7 a 3 minutos, en pacientes adultos. Tales pacientes, con visión binocular normal, acostumbran a adaptarse rápidamente. El estudio se realizó en una totalidad de 32 participantes adultos, descartando anomalías de visión binocular; con rango de edad entre 18 y 24 años. Se compararon ratios de adaptación de foria en convergencia (BT) y divergencia (BN). La muestra de participantes se dividió entre los que mostraron un cambio más elevado en 1Δ/min, durante los 3 minutos de la prueba, y los que no cambiaron. Si nos basamos en los resultados obtenidos al final del estudio, concluimos que 3 minutos son suficientes para garantizar la adaptación de foria, siempre que no exista patología o problemática binocular y, por tanto, poder obtener los resultados esperados. Se puede considerar esta prueba válida para obtener diagnóstico durante la práctica optométrica diaria con pacientes adultos y visión binocular estable.