Ординатура / Офтальмология / Английские материалы / Basic Principles of Ophthalmic Surgery_Arnold_2006
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chapter 4 I the operating microscope and surgical loupes
Figure 4.16. The instrument should be held like a pencil with a light grip. This helps to relax the muscles in the hand and reduce tremor.
dominant hand, and practicerotating the penback and forth as gently aspossible. Keepthe rest of the hand still, and only move the thumb and two fingers in a gentlerotating motion. This mimics the required maneuversof cataract surgery,in particular the irrigation and aspiration stepduring cortical removal, and teachesthe surgeonto keepthe handsrelaxed.
Dampening Tremor With Counter Touch
One of the most effectivemeansof reducinghand tremor is to touch the instrument with the nondominant hand. For example,if a surgeonis holding an instrument in his or hcr dominant right hand, using the lcft indcx fingcr to just touch the instrument greatly reducestremor. This obviously is not po/!- sible when borh handsarebeingused,but during ont!~handt!dmant!uv@r~,the techniqueis very important and effective.The classicexampleis during thc capsulorrhexisstepof cataractsurgery,which is a one-handedmaneuverusu- ally involving forceps. Graspthe forcepslightly, like a pencil, with the thumb and first two fingers of the dominant hand.Next, take the index finger of the nondominant hand and touch the forceps just below the fingers of the dominant hand (Figure 4.17).This is a very stablehand position and candramatically reducehand tremor.
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Another commonmicroscopeproblem causedby poor hand position is excessiveside-to-sideeyemovement.This ca.nhappenat eitherthe 12:00 or temporal position. The most common causeis failure to keepthe surgical
instrument centeredin the incision. This is one of the most difficult concepts for the new surgeon.The natural tendencyis to move the instrument laterally in the incision. Eventually, the end of the incision is reachedand at that point the whole eyemovesin that direction. The proper techniqueis to keepthe instrument centeredin the incision and pivot around that point, like a fulcrum. A good visual conceptis to picture the instrument like the oar of a boat. At the wound entranceinto the eye,the instrument is locked into place,like the oarlock on the side of the boat. At this point the instrument (or oar) cannotmove laterally, it canonly pivot. Learningthis technique for intraocular surgery, especiallycataractsurgery,is essentialif the eyeis to remaincenteredin the microscopefield. This techniquealsoreducescornealstriae,which improves visualization and safetyespeciallywhen performing capsulorrhexis.
MICROSCOPE FUNCTION
Once the patient is well positioned, the surgeonis comfortable, and the hands arestabilized, attention is directed to the microscopeitself. Four key points in the proper operation of the microscopeinclude
1.Gross maneuveringof the microscopeandcentering of its axes
2.Positioning and setting the oculars
3.Adjusting the microscope during the case
4.Controlling the lighting
Gross Maneuvering of the Microscope
Modern microscopescanbe either ceilingor floor-mounted. Ceiling-mounted microscopesare useful when there is a dedicatedoperating room for microsurgery.They poselessof a physicalobstacle'within the operating room and do not haveto be repositioned with eachnewpatient. Nevertheless,floormounted microscopesare equally effective.When the surgeonis positioned
atthe 12:00position, the floor-mounted microscopeis usuallyplaced on the sideof the surgeon'snondominant hand.This allows the surgicalinstruments to be atthe ready for the surgeon'sdominant hand.Alternatively, the microscopemay alwaysbeplaced on one side or the other regardlessof the operated
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Figure 4.19. Microscope head with (A) a centering button to center the x-y axes, (8) the scale to
center the up and down axis, and (C) the positioning handles.
the microscope full excursionin all directions atthe start of the case(Figure 4.19A). The head of the microscopeis alsoequipped with large positioning handles.There aretwo or three handles,usually one on either side of the oculars and often a third on the positioning arm (Figure 4.19B).Typically, handles arefitted with slide-on coversthat canbe sterilized. A final important initial adjustment,accomplishedvia the foot pedal,is the centeringof the microscope focus in the up and down axis. Most often a scaleon the side of the microscope headshowsthe midpoint of the focus (Figure 4.19C).The microscopemay
be placed in the middle of the focus axisto slightly abovecenter.Sinceduring surgery,most of the focusingis downward, sufficient excursionin this direction must be availableat the start of the case.
