Complex Regional Pain Syndrome (CRPS) is a clinical condition characterized by pain that arises either without an identifiable triggering factor or with a severity disproportionate to the initiating event. Its progression is typically unpredictable, and most therapeutic interventions yield only partial efficacy. Prism Adaptation Therapy (PAT) is a sensorimotor training method traditionally employed to mitigate attentional deficits in post-stroke hemispatial neglect and has recently been explored as a treatment modality for CRPS. Preliminary non-blinded studies with small patient cohorts have demonstrated its potential to reduce pain and related symptoms. The present study aims to assess the effects of prism adaptation therapy administered during the acute phase on pain intensity and other clinical outcomes in CRPS, addressing the considerable challenges associated with managing chronic pain in this disorder.

A total of 54 patients diagnosed with Complex Regional Pain Syndrome (CRPS) type 1, in accordance with the Budapest diagnostic criteria and fulfilling the inclusion and exclusion criteria, were enrolled in this study. Utilizing the sealed-envelope method, participants were randomized into two equal groups: 27 patients assigned to the prism adaptation therapy group and 27 to the control group. The control group received standard physical therapy and rehabilitation interventions supplemented by a pointing protocol administered once daily over 20 sessions under the supervision of the same physician/physiotherapist, with the use of neutral-lens goggles. Conversely, the prism adaptation therapy group underwent the identical pointing protocol employing prismatic-lens goggles in conjunction with standard physical therapy and rehabilitation interventions.

Baseline data collection prior to randomization included demographic characteristics such as age (years), sex (female/male), marital status (married/single), occupation, educational level, living arrangement, and alcohol and tobacco consumption. Clinical and disease-related baseline variables were also recorded, comprising height (cm), body weight (kg), body mass index (kg/m²), comorbidities, and current medication regimens. The etiology or inciting event(s) were documented, including fracture, surgery, immobilization, and casting. For fracture-related cases, detailed information on fracture pattern, intra-articular involvement, casting, surgical intervention, type and duration of immobilization, and the interval from the inciting event(s) to presentation at the physical medicine and rehabilitation outpatient clinic was noted. Furthermore, CRPS-associated signs and symptoms-including pain, edema, color changes, temperature alterations or asymmetry, sweating changes, nail and hair abnormalities, involuntary movements, tremor, weakness, and limitations in hand and wrist range of motion-were assessed at baseline. Sensory evaluations encompassed hyperalgesia testing with cotton wool and allodynia assessment using a 22-gauge black-tipped needle.

All patients were evaluated at three time points: baseline prior to treatment initiation (T0), immediately following treatment completion (T1), and six weeks post-treatment (T2). Assessments included clinical parameters, standardized evaluation tests, and ultrasonographic examinations.

Inclusion Criteria

• Individuals aged between 18 and 75 years
• Patients diagnosed with CRPS Type 1 according to the IASP 2003 CRPS Budapest diagnostic criteria
• Presence of traumatic etiologies, including surgical procedures, fractures, or immobilization
• Patients who consented to participate and provided written informed consent

Exclusion Criteria

• History of inflammatory, autoimmune, hematologic, or neoplastic diseases
• Diabetes mellitus, thyroid disorders, hepatic or renal failure
• History of cranial trauma or cranial surgery within the preceding 6 months
• Use of diuretics, anti-inflammatory, antineoplastic, corticosteroid, immunosuppressive, antidepressant, or anxiolytic medications within the past 2 months
• Use of anticholinergic medications within the past 7 days
• Active ocular infection, inflammation, allergy, or recent use/exposure to ophthalmic drops
• History of lens or ocular surgery within the last 3 months
• Current or previous use of glasses or contact lenses, or diagnosis of refractive error ≥0.5 diopters
• Peripheral nerve injury in the affected hand consistent with CRPS Type 2 as per Budapest criteria
• Known progressive or non-progressive peripheral or central nervous system disorders
• CRPS Type 1 developing subsequent to central nervous system injury (e.g., stroke)
• Patients in the acute phase following primary or secondary tendon repair
• Presence of comorbid conditions likely to impair functionality and health-related quality of life, such as decompensated heart failure, chronic kidney failure, or malignancy
• Comorbid diseases affecting hand function, including rheumatoid arthritis, psoriatic arthritis, or other inflammatory disorders involving the hand
• Joint restriction and/or muscle weakness in the affected extremity that would impede movement
• History of acute upper-extremity deep vein thrombosis or arterial thrombosis
• Arterial or venous injury and/or history of arterial or venous repair surgery
• History of heavy alcohol consumption or inappropriate opioid use
• Inadequately treated psychiatric disorders or conditions, such as major depression, anxiety, or schizophrenia
• Recurrent diagnosis of CRPS Type 1, defined as patients experiencing repeated episodes

Individual participant data (IPD) will not be shared publicly due to institutional policies and ethical considerations. De-identified, aggregate results will be reported in publications.

Participants wore either prismatic-lens goggles or neutral-lens goggles during the pointing protocol. Both interventions were described as potentially beneficial.