A 39-year-old man presented with a left corneal perforation secondary to fungal keratitis. He underwent an emergency keratoplasty of the left eye under general anesthesia. His medical history included uncontrolled diabetes and a history of tuberculosis treatment. On examination, his left eye had mucopurulent discharge and hyperemic conjunctiva. For the surgery, he was given general anesthesia with an LMA to prevent increases in intraocular pressure that can occur with direct laryngoscopy and emergence. Prophylaxis for postoperative nausea and vomiting was also given due to the importance of preventing coughing and bucking in ocular surgery.

1. Eye Surgery
Cassandra Lao
2nd Year Resident

2. Case of R.B., 39/M, 65kg, BMI 23
Diagnosis: corneal perforation, left eye, secondary to fungal
keratitis
Procedure: emergency keratoplasty, left eye under GA at
11am
CC: foreign body sensation, left eye
1 month PTC, foreign body sensation after being hit by
“palay.”

3. PMHx
+ DM, uncontrolled. Stat CBG upon admission was 449
+ History of PTB 2021, s/p 6 months Tx
No HTN. GFC
No COPD, asthma, COVID
No hx of MI, paralysis, stroke
No previous surgery
Smoker, 10 pack years, last smoke in March 2023
Not an alcoholic

4. PE
BP 120/80 HR 90 RR 19
Conscious, coherent,
ambulatory, GCS 15
Mallampati 2
Adequate thyromental distance,
mandibular length
Inadequate? mouth opening,
Good neck mobility
Complete dentition
Left eye matted, with
mucopurulent discharge,
hyperemic conjunctiva
Right eye, pink palp conjunctiva
Symmetrical chest expansion
Clear breath sounds
Adynamic precordium, no
murmurs
Abdomen soft nontender
Full and equal pulses
No pedal edema

5. Ancillaries
CBG 182-206
Hgb 149
Hct 0.44
Plt 297
WBC 7
Crea 0.53
Na 135
K 3.65
12L ECG: NSR
CXR
consider PTB, B upper lobes
with cicatricial atelectasis, L

6. Orbit
• Two symmetrical bony enclosures in the front of the skull, each
containing an eyeball (or globe) and its associated structures
• The cavity of each orbit is a truncated pyramid, with a flattened
apex posteriorly and a trapezoidal base facing anterolaterally.
• Volume of each adult orbit is approximately 30 mL

7. Orbit: diagrammatic superior view

8. Globe
• Suspended in the anterosuperior part of the orbit
• Wall of the orbit is comprised of:
• Sclera - fibrous outer layer
• Uveal Tract – middle layer; vascular; composed of the iris, ciliary body, and choroid
body, and choroid
• Retina - neurosensory membrane composed of 10 layers that convert light impulses
convert light impulses into neural impulses
• The volume of the globe is approximately 7 mL.

9. Globe
The globe has a large posterior segment
• comprising the vitreous humor, the retina, the macula, and the root of the optic
nerve
and a small convex anterior segment comprising two chambers
• The anterior chamber immediately behind the cornea is filled with aqueous
humor produced by the ciliary body.
• The posterior chamber contains the lens.

10. Globe

11. Muscles of the Eye
• four rectus and two oblique muscles

12. Blood supply and drainage
• Blood supply to the eye and orbit is by means of branches of the
internal and external carotid arteries.
• Venous drainage of the orbit is accomplished through the multiple
anastomoses of the superior and inferior ophthalmic veins. Venous
drainage of the eye is achieved mainly through the central retinal
vein. All these veins empty directly into the cavernous sinus.

13. Intraocular Pressure
• Between 10 and 21.7 mmHg and is considered abnormal above 22
mmHg
• If IOP is too high, it may produce opacities by interfering with normal
corneal metabolism.
• During anesthesia, a rise in IOP can produce permanent visual loss. If
the IOP is already elevated, a further increase can trigger acute
glaucoma.
• Rupture of a blood vessel with subsequent hemorrhage may
transpire.

14. Three main factors that influence IOP
(1) External pressure on the eye by the contraction of the orbicularis
oculi muscle and the tone of the extraocular muscles, venous
congestion of orbital veins (as may occur with vomiting and
coughing), and conditions such as orbital tumor
(2) Scleral rigidity
(3) Changes in intraocular contents that are semisolid (lens, vitreous,
or intraocular tumor) or fluid (blood and aqueous humor)

15. Factors influencing IOP
• Intraocular blood volume, determined primarily by vessel dilation or
contraction in the spongy layers of the choroid, contributes
importantly to IOP.
• Excursions in arterial pressure have much less importance than do
venous fluctuations.
• if venous return from the eye is disturbed at any point from Schlemm
canal to the right atrium, IOP increases substantially. Trendelenburg
position, a cervical collar, and even a tight necktie can produce
increased intraocular blood volume and distention of orbital vessels
as well as attenuated aqueous drainage.

16. Factors influencing IOP
• Straining, vomiting, or coughing greatly increases venous pressure
and raises IOP as much as 40 mmHg or more.
• Laryngoscopy and tracheal intubation may also elevate IOP, even
without any visible reaction to intubation, but especially when the
patient coughs.
• If the coughing or straining occurs during ocular surgery when the eye
is open, as in penetrating keratoplasty, the result may be a disastrous
expulsive hemorrhage, at worst, or a disconcerting loss of vitreous,
at best.

17. Effects of CNS depressants on IOP
• All volatile anesthetics decrease IOP
• Barbiturates, neuroleptics, opioids, tranquilizers, and hypnotics, such
as etomidate and propofol—lower IOP in both normal and
glaucomatous eyes.
• Etomidate-induced myoclonus may be hazardous in the setting of a
ruptured globe.
• Ketamine does not increase IOP but its inclination to cause nystagmus
and blepharospasm makes it a less-than-optimal agent

18. Effects of Ventilation and Temperature on IOP
• Increases IOP
• Asphyxia
• administration of carbon dioxide
• Hypoventilation
• Decreases IOP
• Hyperventilation
• Hypothermia

19. Effects of Adjuvant Drugs on IOP
• Hypertonic solutions such as dextran, urea, mannitol, and sorbitol
elevates plasma osmotic pressure, thereby decreasing aqueous humor
formation and reducing IOP.
• Acetazolamide inactivates carbonic anhydrase and interferes with the
sodium pump. The resultant decrease in aqueous humor formation lowers
IOP.
• Equipotent paralyzing doses of all the nondepolarizing drugs directly lower
IOP by relaxing the extraocular muscles.
• Succinylcholine increases IOP by about 8-10 mmHg
• IOP increases with reversal of NDMR with neostigmine and atropine but
unchanged with sugammadex

20. Other causes of Increased IOP
• Most significant rise in IOP occurs during direct laryngoscopy and
emergence
• Insertion of LMA results in little or no increase in IOP
• Poorly placed anesthesia mask leads to pressure on the eye
• Ocular blocks increase IOP by 5-10mmHg but this value falls to below
baseline values within 5 mins
• Supine, prone, Trendelenburg positions
• Normal blink increases IOP by 10 mmHg
• Forceful lid squeeze can increase IOP to more than 70 mmHg

21. Indications for Endotracheal intubation
• Penetrating Keratoplasty
• Deep anterior lamellar keratoplasty
• Combined corneal transplantation and vitrectomy
• Vitreoretinal procedures

22. • Prevention of coughing and bucking during emergence is important in
ophthalmic surgery
• Prevention of PONV is important

23. Case of R.B., 39/M, 65kg, corneal perforation
• Anesthetic Technique: GA-LMA
• Maintained with sevoflurane, atracurium
• PONV Prophylaxis with dexamethasone and ondansetron
• Deep extubation
• Adequate gentle suctioning

24. Thank you!