. Refraction and muscular imbalance, as simplified through the use of the ski-optometer. rther explanation of the phorometers prin-ciple and construction, when two five-degreeprisms are placed together so that their basesare directly opposite, they naturally neutral-ize; when their bases are together, theirstrength is doubled. Thus while the prisms ofthe phorometer are rotating, they give prismvalues from piano to ten degrees, the same be-ing indicated by the pointer on the phoro-meters scale of measurments. As a guide in dark-room testing, it shouldbe noted that the handle of the phorometerin
. Refraction and muscular imbalance, as simplified through the use of the ski-optometer. rther explanation of the phorometers prin-ciple and construction, when two five-degreeprisms are placed together so that their basesare directly opposite, they naturally neutral-ize; when their bases are together, theirstrength is doubled. Thus while the prisms ofthe phorometer are rotating, they give prismvalues from piano to ten degrees, the same be-ing indicated by the pointer on the phoro-meters scale of measurments. As a guide in dark-room testing, it shouldbe noted that the handle of the phorometerin a vertical position is an indication that thevertical muscles are being tested; if hori-zontal, the horizontal muscles are undergoingthe test. The Maddox RodThe Maddox rod (Fig. 14) consists ofa number of red or white rods, which causea corresponding colored streak to be seenby the patient. This rod is placed mostconveniently on the instrument, being pro- [44] Refraction and Muscular Imbalance vided with independent stops for accuratelysetting the rods at 90 or 180 degree Fig. 1-1—The Maddox Rod, a valuable aid in makingmuscular tests. The Maddox rod has proven of valuable as-sistance in detecting muscular defects, par-ticularly when used in conjunction with thephorometer. Thus employed, it enables thepatient to determine when the streak seen withone eye crosses through the muscle-testingspot-light observable by the other eye, as here-after described. Procedure for Making the Muscle TestThe Ski-optometer should be equipped withtwo Maddox rods, one red and one combined use is of the utmost import-ance since they assist in accurately determin-ing cyclophoria and its degree of tortion as [45] Refraction and Muscular Imbalance designated on the degree scale, and fully de-scribed in a later chapter. When the Maddox rods are placed in avertical position, it is an indication that thevertical muscles are being tested; when placedhorizontally, the horizontal m
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