[Prism correction in heterophoria].

Area of Science:

• Ophthalmology
• Neuroscience
• Vision Science

Context:

• Heterophoria, or latent strabismus, is a common condition affecting 70-80% of the population.
• It represents a deviation from the orthovergence position, often a reaction to sensory-motor feedback disruption.
• Unlike manifest strabismus (heterotropia), heterophoria is not a primary condition but a compensatory response.

Purpose:

• To differentiate heterophoria from manifest strabismus and other conditions causing asthenopic complaints.
• To critically evaluate diagnostic methodologies like the "measuring and correcting methodology after H.-J. Haase" (MKH).
• To assess the efficacy of prism spectacles in managing heterophoria-induced symptoms.

Summary:

• Heterophoria necessitates sensory-motor fusion, which can lead to asthenopia (e.g., headaches), especially during prolonged visual tasks.
• Differential diagnosis is essential to rule out other causes of similar symptoms before attributing them to heterophoria.
• Prism trials in free space, including placebo controls, are recommended before considering prism spectacles or surgery.
• The MKH methodology's reliance on subjective fixation disparity tests may be misleading, as objective recordings show eyes can be aligned despite perceived disparity.
• A Dutch trial found no significant advantage of MKH-determined prism spectacles over conventional ones for asthenopic complaints.

Impact:

• Highlights the importance of accurate diagnosis and appropriate treatment strategies for heterophoria.
• Questions the diagnostic validity of certain subjective tests used in vision assessment.
• Provides evidence-based insights into the limited efficacy of prism spectacles determined by specific methodologies for asthenopic complaints.