SYNOPTOPHORE / MAJOR AMBLYOSCOPE The synoptophore is a reflecting and refracting stereoscope. The optics are such that the instrument measures at infinity. It is used to assess binocular single vision (BSV) or the potential to have BSV. It assesses the 3 levels of BSV 1 simultaneous perception: red bound slides 2 fusion: green bound slides 3 stereopsis: yellow bound slides. Different size targets are used depending on the patient’s level of vision, foveal, macular, paramacular and peripheral. The smallest one compatible with the visual acuity should be used. SIMULATANEOUS PERCEPTION(SP) The angle of deviation in measured subjectively and objectively. If SP is not present the subjective angle cannot be accurately measured. The slides are designed so that the patient puts something into something eg a lion in a cage. Objective measurement. The slide with the fixation target is place in front of the fixing eye. Alternate cover test is performed using the light of the tubes and the other target is moved until there is no movement as the eye fixates. Horizontal, vertical and torsional deviation can be measured in this way but usually it is not possible to measure torsion objectively. This can be repeated fixing either eye. Subjective measurement. The instrument is set up in the same way but the patient moves the tube for horizontal alignment to put the lion in the cage and the operator moves for vertical and torsional alignment on the patient’s instruction. Suppression may warrant the use of larger targets so the image falls out of the suppression area. FUSION These consist of targets which are mainly the same but each has a different control on it eg a bear, one sitting on a cushion and the other with a honey pot on its head so the patient has to join it into one with both controls present. The patient is asked to join the slides and the operator must ensure that both controls are there and one is not suppressed. The tubes are then converged or diverged until the images separate into 2 or one control disappears. This gives the fusion range. Sensory fusion is present if the objects join but cannot be maintained over a range, motor fusion is shown by the range. STEREOPSIS These have slightly disparate targets so that when fusion occurs the image is seen in depth. The patient is asked to join the objects and then asked whether they are nearer to them or to the operator. Measurements can be taken in 9 positions of gaze or specific, relevant directions eg elevation and depression for and A or V pattern. Suppression area can be plotted. The AC:A ratio can also be measured see AC:A ratio handout. On certain models there is an adaptation for after image assessment for macular function.
Posted on: Thu, 06 Mar 2014 10:44:19 +0000