“Sports Physio Eye Development, in association with IGARD Group Singapore, organised the Singapore’s first multidisciplinary workshop in Vision and Proprioception. The workshop was conducted by overseas guest Professor Orlando Alves Da Silva, an ophthalmologist famed for his work in treating proprioceptive dysfunction syndrome (PDS) and moderated by IGARD senior consultant Yap Tiong Peng. The two-day workshop was attended by nearly 50 attendees including behavioural optometrists (VTOD), occupational therapists (OT), physiotherapists (PT), educational psychologists, orthoptists and specialist educators; and the attendees were from Singapore, Taiwan, Malaysia, Philippines, Canada and Indonesia. About 20 behavioural optometrists completed the Vision Therapy Certification Course in Prescribing Active Prisms in the Treatment of Proprioceptive Dysfunctional Syndrome.”
I had come across the work of Orlando Alves da Silva, a professor of Ophthalmology from Portugal, awhile back but had forgotten about it. The IGARD post prompted a visit to Professor da Silva’s website, where provides an overview of Postural Deficiency Syndrome (PDS), also referred to as Proprioception Dysfunction Syndrome). Here is a PDF of Postural Deficiency Syndrome / Proprioception Dysfunction Syndrome (PDS): Summary of Diagnostic Protocol and Active Prisms Protocol, revised several weeks ago, from which the following grid is extracted:
In a nutshell, there are three parts to Professor da Silva’s diagnostic battery. One is a differential intermittent suppression of fusion targets in a synoptophore when the patient gazes to the left (levoversion) or right (dextroversion), which he terms a pseudoscotoma on directional scotometry. The second part of the diagnostic battery is evaluating symmetry of upward head tilt/rotation, and the third part is evaluating the effects on heel/foot support.
Professor da Silva postulates that there is a correspondence between the range of angles at which peripheral pseudoscotomas (intermittent suppressions) are observed in dextroversion and levoversion, and the dominant supporting limb. A peripheral pseudoscotoma at a lower angle in dextroversion than in levoversion corresponds to a left-hand side supporting foot; a peripheral pseudoscotoma at a lower angle in levoversion than in dextroversion corresponds to a right-hand side supporting foot. Refer to the PDF for more details.
You’ll also note from the grid in the PDF that prism is prescribed based on the responses above, either unilaterally or bilaterally, and always less than 4^. From what I gather, when the asymmetries are predominantly horizontal the prism is lateral, and when the asymmetries are referenced to the inferior obliques the prism is oriented at 125 degrees R eye and 55 degrees L eye. I like the term “prescribing active prisms” because it conveys that the prism is not a passive compensatory tool when Rxed this way, but is exerting a therapeutic effect.