Print this page

ACCOMODATION AND VERGENCE (also covers vision therapy concepts)

• A simple definition of the AC/A ratio
• AC/A defined = a change in vergence during accommodation
• Example = AC/A of 4/1 means for every 1.00D in accommodation, you will converge 4 prism diopters
• You can remember low and high AC/A in relation to excess or insufficiency (e.g. convergence insufficiency, etc.)
• Insufficiency always has a low AC/A e.g. CI, DI (think “insufficient = low”)
• Excess always has a high AC/A e.g. CE, DE (think “excess = high”)
• High and low AC/A also has an importance in treatment of vergence dysfunction
• High AC/A = Excess (CE, DE) = lenses are Effective in treatment
• Normal AC/A = (Basic Eso, Basic Exo) sometimes effective
• Low AC/A = Insufficiency (CI, DI) = lenses are Ineffective in treatment
• A quick way to remember that plus lenses induces exo
• The plus sign (+) looks like an rotated X
• Remember, plus lenses relaxes accommodation, which results in decreased convergence (increased divergence)
• How to figure out what prism stimulates what type of vergence
• Mnemonic = “BIM BOP” – keep in mind of that general “rule” that the apex points towards where the eyes will move
• BI stimulates Negative Fusional Vergence
• Negative implies Minus in “BIM”
• The apexes point temporally, causing divergence
• BO stimulates Positive Fusional Vergence
• Positive implies Plus in “BOP”
• The apexes point nasally, causing convergence
• How to know what type of demand to use during vergence therapy
• Mnemonic = “BOCIDE-X, BIDICE-E” (prevent confusion by remembering BOCIDE as a “poison” and BIDICE as “two dice”)
• Use BO prism demand for training CI, DE, and Exo patients
• Use BI prism demand for training DI, CE, and Eso patients