Ophthalmic Surgery Lab
Anatomy of the Eye
Conjunctiva – coverlet like thin transparent membrane that lies over the cornea extending onto the
inner lids both upper and lower
Three Layers called “Tunics”
1. Fibrous tunic
Cornea = anterior 1/3rd of eye
Sclera = posterior 2/3rds of eye
On the outer surface of the sclera are the 6 extrinsic (outside) muscles also called EOM (extraocular muscles) which are what control globe/eye movement:
Superior oblique (SO), inferior oblique (IO), lateral rectus (LR), medial rectus (MR), inferior
rectus (IR), superior rectus (SR)
EOM are controlled by three of the twelve total cranial nerves:
LR6 (SO4) 3
The lateral rectus (LR) is controlled by the IV cranial nerve called the abduscens
The superior oblique (SO) is controlled by the fourth cranial nerve called the trochlear
All other EOM are controlled by the third cranial nerve called the occulomotor
Cranial Nerve Review from class:
I.
Olfactory –smell (think of the old paper factory in Canton that stinks!)
II.
Optic – vision
III.
Occulomotor
IV.
Trochlear
V.
Abduscens
2. Vascular Tunic
Contains two intrinsic (inside) muscles:
Iris – because it is a circular muscle composed of smooth muscle, it can be controlled by
medications that allow it to dilate the pupil or contract the pupil
Ciliary muscle – controlled the shape of the lens which is what allows you to achieve the
function of “accommodation” which is simply put to “focus”
3. Nervous tunic
Retina
Ophthalmic Surgery Lab
Two Cavities in Eye
1. Anterior Cavity
Contains aqueous humor – body continues to reproduce and normally your body maintains this
through drainage into the Canal of Schlemm (where cornea meets sclera inside the fibrous
tunic) so that you do not overproduce it which can lead to increased intra-ocular pressure)
Contains two chambers:
Anterior chamber = iris to front of cornea
Posterior chamber= lens to iris
Cavities separated by normally intact lining/capsule behind/surrounding the lens
2. Posterior Cavity also called Vitreous chamber
Contains retina and vitreous humor (vitreous body)
Vitreous humor –what you have at birth is all you will ever have
Provides shape to the globe and keeps retina in place
Ophthalmic Medication Classifications
Majority are in a liquid/eye drop (gtt) form. Some are in ointment (ung) form.
1.
2.
3.
4.
5.
6.
Topical antibiotics
Dyes
Topical anesthetics
Anti-inflammatories
Mydriatics – dilate iris hence the pupil to allow visibility into the eye
Miotics – constrict the iris making pupil smaller used to maintain a new lens in place postphacoemulsification or extracapsular lens extraction
7. Viscoelastic agents
8. Irrigants
Examples of frequently used ophthalmic medications:
1. Topical antibiotics - neosporin, erythromycin, gentamycin, neomycin, tobramycin
Often combined with anti-inflammatories
2. Dyes – rose Bengal, fluorescein
3. Topical anesthetics –cocaine, lidocaine, tetracaine, bupivacaine, proparacaine
4. Anti-inflammatories – dexamethasone, prednisolone (Pred-forte)
Often combined with antibiotics
5. Mydriatics – atropine sulfate
6. Miotics – Pilocarpine
7. Viscoelastic agents –Healon, Amvisc
8. Irrigant – BSS (balanced salt solution)
Ophthalmic Surgery Lab
Common Eye Pathologies
Chalazion – benign tumor that is the result of an inflamed swollen oil gland on the eye lid
Corrective surgery called chalazion excision
Pterygium – overgrowth of conjunctiva from inner canthus of eye that can extend into the iris
Corrective surgery called pterygium excision
Cataracts – opacity or clouding of the lens
Corrective surgery called phacoemulcification (soft lens seen in younger patients) or extracapsular lens
excision (hard lens seen in older patients)
Strabismus – misalignment of the eye(s) due to EOM tone issues
Corrective surgery called Recession Resection (R & R). Patient may only need one or the other or both.
Surgical Considerations:
Careful steady movements when working around MD and microscope; don’t bump either!
Use BSS to keep cornea moist intra-operatively (slow drops periodically out of MD line of sight)
Lint-free towels or drapes
No sponges!
Use Weck Cells (spears)
Preservative-free ophthalmic medications
Never use water in the eye
Powder-free gloves
Careful slow transport if moving to a stretcher or bed post-operatively
Patients are awake so watch your conversations in that they are not inappropriate or loud