OPHTALMOLOGY Flashcards
WHAT IS THE FUNCTION OF AQUEOUS HUMOR IN THE EYE?
ITS A CLEAR FLUID PRODUCED BY THE CILIARY BODY (LEAVES VIA CANAL OF SCHLEMM) AND PROVIDES ESSENTIAL METABOLIC MATERIALS AND REMOVES WASTE. BIG DETERMINANT FOR IOP.
WHAT IS THE FUNCTION OF VITREOUS HUMOR IN THE EYE?
GEL SUBSTANCE ADHERES TO THE ANTERIOR RETINA, BLOOD VESSELS, AND OPTIC NERVE. IN CENTER OF THE GLOBE. IT CAN PULL ON THE RETINA CAUSING TEARS AND DETATCMENT. CONCERNED ABOUT THIS IN OPEN EYE INJURY.
IF AQUEOUS HUMOR BUILDS UP IT CAUSES BIG PROBLEMS…WHAT ARE THEY? AND HOW DOES THIS AQUEOUS HUMOR BUILD UP?
AN INCREASE IN VENOUS PRESSURE OR A DECREASE IN THE CROSS SECTIONAL AREA OF THE EYE (PRESSURE ON THE EYE)INCREASES THE RESISTANCE TO AQUEOUS HUMOR OUTFLOW VIA THE CANAL OF SCHLEMM. THIS WILL IN TURN INCREASE INTRA OCCULAR PRESSURE. GLAUCOMA IS CAUSED BY AN OBSTRUCTION TO AQUEOUS HUMOR OUTFLOW. INCREASED IOP CAN ALSO OCCUR WITHOUT AQUEOUS HUMOR VOLUME INCREASE DUE TO MASK PRESSURE, IMPROPER POSITIONING, RETROBULBAR HEMORRHAGE.
WHAT DOES INTRAOCULAR BLOOD VOLUME DO TO INTRAOCULAR PRESSURE?
INTRAOCULAR BLOOD VOLUME IS DETERMINED BY VESSEL DILATION OR CONTRACTION IN THE SPONGY LAYERS OF THE CHOROID AND AN INCREASE IN VOLUME WILL INCREASE INTRAOCULAR PRESSURE.
HOW DOES CHOROIDAL BLOOD PRESSURE EFFECT INTRAOCULAR PRESSURE?
AS CHOROIDAL BLOOD VOLUME AND PRESSURE RISES INTRAOCULAR PRESSURE RISES.
HOW DO BLOOD PRESSURE AND INTRAOCULAR PRESSURE CORRELATE?
IF BP RISES SO DOES INTRAOCULAR PRESSURE THEREFORE KEEP PRESSURE DOWN! DONT LET THEM STRAIN, COUGH, VALSAVA.
WHAT IS NORMAL INTRAOCULAR PRESSURE?
12-20MM HG
THE SAME THINGS THAT INCREASE ICP INCREASE IOP.
HOW DOES O2 AND CO2 EFFECT IOP?
HYPOXIA CAUSES INCREASES IN CHOROIDAL VASODILATION AND INCREASED IOP. ?????
INCREASED CO2 INCREASES IOP. HYPOCARBIA DECREASES IOP BY VASOCONSTRICTION AND REDUCED CARBONIC ANHYDRASE ACTIVITY.
HOW DO ANESTHETIC AGENTS EFFECT IOP?
MOST EITHER LOWER OR HAVE NO EFFECT ON IOP. SUX INCREASES IOP NMDR REDUCES IOP VA DOSE DEPENDENT REDUCTION IN IOP BARBS, BENZOS, OPIATES ALL LOWER IOP KETAMINE INCREASES IOP
WHAT IS THE MECHANISM THAT ELICITS THE OCULOCARDIAC REFLEX?
PRESSURE ON THE EYES> SURGICAL PRESSURE ON THE GLOBE AND TRACTION ON THE EXTRAOCULAR MUSCLES, ESP THE MEDIAL RECTUS, AS WELL AS THE CONJUCTIVA OR THE ORBITAL STRUCTURES. COMMON IN PEDS. HYPERCARBIA OR HYPOXEMIA MAY INCREASE THE INCIDENCE OR SEVERITY.
HOW DO YOU TREAT OCULOCARDIAC REFLEX?
REMOVE THE SURGICAL STIMULUS. HAVE ATROPINE DRAWN UP. GIVE IV ATROPINE 3-6 MCG/KG; 4MCG/KG IN PEDS. THE SURGEON WILL INFILTRATE THE RECTUS MUSCLES WITH LOCAL. EVENTALLY THE REFLEX WILL FATIGUE ITSELF WITH REPEATED TRACTION ON THE EXTRAOCULAR MUSCLES.
DESCRIBE A RETROBULBULAR BLOCK.
INJECT LA (LIDO OR BUPIVICAINE) INTO THE MUSCLES CONE DEEP BEHIND THE GLOBE, FOLLOWED BY AN INJECTION OF THE FACIAL NERVE. HYALURONIDASE IS USED TO BREAK UP TISSUE AND INCREASE THE SPREAD OF LA.
DESCRIBE A PERIBULBAR BLOCK.
LA IS INJECTED OUTSIDE OF THE MUSCLE CONE. IT CAN BE SUPPLEMENTED IF NEEDED WITH SMALL 3CC RETROBULBAR INJ AND LID BLOCK.
WITH BOTH EYE BLOCKS WHAT IS THE TECHNIQUE?
BLUNT TIP 25 G NEEDLE PENETRATES LOWER LID AT MIDDLE AND LATERAL ONE THIRD OF THE ORBIT JUNCTION. PT STARES SUPRA NASALLY AS THE NEEDLE ADVANCES 3.5 CM TOWARD APEX OF MUSCLE CONE. ASPIRATE..NO BLOOD….INJECT 2-5 ML OF LA. ITS SUCCESSFUL IF YOU HAVE AKINESIA, ABOLISMENT OF THE OCULOCEPALIC REFLEX.
WHAT ARE IMPORTANT ANESTHETIC CONSIDERATIONS DURING THE EYE BLOCKS?
STANDARD MONITORING ON PT PRIOR TO BLOCK. INCLUDING PRECORDIAL. EXTENSION ON IV BECAUSE THE TABLE WILL BE TURNED. TOO MUCH SEDATION MAY MAKE THE PATIENT UNCOOPERATIVE. NASAL CANNULA BUT BE CAREFUL WITH O2 DURING CAUDERY. COMMUNICATE FREQUENTLY. IF DOING GA KEEP DEEP AND PARALYZED, WANT NO MOVEMENT. GIVE ANTIEMETIC-PRONE TO PONV. DEEP EXTUBATION AND NPO. HOB UP. THINK ICP STUFF.
