Ocular hypotony is a common, unexplained feature of myotonic dystrophy. Some investigators have ascribed the decrease in intraocular pressure to unusually high outflow facility. The present study demonstrates that increased outflow facility in myotonics is often artifactitious. When corrected for ocular rigidity, outflow facility is frequently normal. The present study presents indirect evidence that ocular hypotony in myotonics results from reduced aqueous production or increased uveoscleral outflow.