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CLE 162.3 Optometric Procedures Notetaker: Kyle Reuter Date: 3/20/12 1st Hour Page 1 Ocular Dominance - Visual input from one eye versus the other is preferred Make small triangle with hands and put letter on Snellen chart o If you close 1 eye it will disappear with the eye that is not dominant o Eye that still sees target is the dominant eye Binocular Balance - Goal: Eliminate accommodative imbalance between 2 eyes in the final Rx. Candidates for BB: o Patients that are not absolute presbyopes i.e. people with no accommodation left o Patients that have VA that differ by 1 line between both eyes Ex. If right eye is best corrected at 20/20 and left eye is best corrected at 20/40 If you give target 2 lines better than BCVA, the brain will always prefer the clearer eye Binocular Balance Through Prism - - - Isolate distant line 2 above BCVA On JCC lens, select prism setting Tell patient, “I’m going to add lenses, it might become blurry” Add +0.50DS to each eye Place 3∆ BD OD and 3∆ BD in OS via Risley Prism o Confirm that the patient is seeing 2 targets (lines) that are separated vertically o May need to add more than 3∆ to each eye to disrupt fusion Tell patient to ignore the brightness of the screen and report which set of letters is most clear o Top image correlates to BD and bottom image refers to the BU Add +0.25DS to the more clear eye and repeat until lines look equal o Goal is to make them both look the same If you cannot make them the same, leave the dominant eye with less plus power o I.e. Leave the dominant eye with the more clear image Add another +0.50DS OU and remove the Risley Prism Check VA o Should be reduced from before because of the added plus power Slowly begin adding minus BINOCULARLY in -0.25D increments until patient reports that the letters are clear and comfortable o Monitor VA and visual efficiency so that you do not overminus the patient Once the patient reports that the letters are clear, check the VA for each eye Binocular Balance Through Alternate Occlusion - Basically the same process as BB through Prism except that you occlude one eye CLE 162.3 Optometric Procedures Notetaker: Kyle Reuter - - Date: 3/20/12 1st Hour Page 2 Occlude one eye and have them look at target, then occlude other eye and have them view the same target with the other eye o Ask them if one image appeared to be more clear, and add +0.25DS to the eye that appeared most clear You still add the +0.50DS OU before you begin and the +0.50DS OU after Usually done if the patient has a intermittent strabismus or very high exophoria Troubleshooting - - - - How can I tell if my patient is suppressing an eye during prism dissociation? o The patient should tell you they only see ONE line of letters Why we confirm that they see 2 o If suppressing, the patient may report that they see the single line moving when doing prism dissociation If suppressing OS, the image will appear to move further “up” due to the addition of BD to OD Vice versa if suppressing OD After BB, the patient has slightly worse vision in one eye than after step 4 of manifest refraction. How can this be right? o During the BB step, you equalized the amount each eye accommodates Remember: eyes are lazy and will only accommodate to the lesser amount required o It is OK if one eye sees slightly less (one VA line) than before When patient is viewing target with both eyes, this difference will be eliminated o If the vision is worse by multiple lines, repeat the test for accuracy After finishing BB, the result was more minus sphere in one/both eyes compared to the step 4 result. Did I screw up? o BB results generally have the same/more plus than the monocular findings. o More minus may mean that one/both eyes have been overminused o Should not happen – Go back and make sure that they earn the 20/20 Why didn’t balancing my amblyopic patient work? o First, the patient must be “binocular” so it should not work for a strabismic amblyope o Second, if the VA difference between the 2 eyes is more than one line, the target of the clearer line with ALWAYS appear more clear Hence, not balancing accommodation, but balancing VA’s will result in over-minusing the worse eye when minus power is added binocularly o Amblyopes have a disruption to the development of one of the visual tracts that causes imbalance in their ocular dominance CLE 162.3 Optometric Procedures Notetaker: Kyle Reuter Date: 3/20/12 1st Hour Page 3 Meaning, one eye cannot be best corrected to the VA of their other eye Typically, it’s about a difference of 1 line Chromatic Aberration - - Use Red/Green screen to test for chromatic aberration If your manifest refraction is perfect, then the patient will see the brightness of the red/green as equal o If you have over-minused someone, the green side will appear clearer o If you have over-plused someone, the red side will appear clearer Different wavelengths of light are bent to different extents Longer wavelengths are bent less (Red) o i.e. require minus power to bring to equal Shorter wavelengths are bent more (Green) o i.e. require plus power to bring to equal Duochrome or Bi-Chrome Test - - Choose during which step you will introduce this test o Can be introduced at any time that you are adjusting sphere power i.e. Step 1, Step 4, Binocular Sphere Adjustment (after BB) Isolate a line at least 2 lines above BCVA Apply the Red/Green filter Completely darken exam room o So that no other wavelengths of light interfere Add +0.50 DS to non-occluded eye(s) Ask patient which side of chart looks more clear o Expecting red side because you have added plus o If the patient says the green side is clearer, add more plus because you have over-minused the patient o **If adding additional plus does not result in the red side becoming more clear/dark, but instead blurs the target – Discontinue the procedure** o If patient says that the red side is more clear/darker, add -0.25DS increments until the patient reports that the red and green letters appear equally clear/dark **If working in an exam room that is less than 20ft in length, the appropriate endpoint is the first -0.25DS increment that leaves the green side more clear/dark**