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OVER VIEW OF
OCCULAR PHYSIOLOGY
&
BIOCHEMISTRY
Shamsun N. Khan, Ph.D,
Postdoc Harvard, USA
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The Eye
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Human Eye – cross section 1

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Sclera:
• White portion of the eye, outermost layer
• Continuous with the cornea anteriorly
• Firm fibrous membrane
• Gives attachment to the extra ocular
• Muscles of the eye
Cornea (Transparent):
• Continuation of the sclera anteriorly
• Convex, epithelial membrane
• Light rays pass through the cornea to retina
• Convexity refracts the light rays (bends)
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Structure
• Three layers in the wall
• Outer fibrous layer: sclera and cornea
• Middle vascular layer: choroid, ciliary
body and iris
• The inner nervous tissue layer: retina
• The structures inside the eyeball are the
lens, aqueous fluid (humour) and
vitreous body
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Choroid
• Lining of the posterior five sixths of the
inner surface of the sclera
• Rich in blood vessels
• Deep chocolate brown in color
Ciliary body
• Anterior continuation of the choroid
• Consists of smooth muscle fibers (ciliary
muscle)
• Secretory cells – aqueous fluid into the
anterior segment

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• Suspensory ligament is attached to it
• The suspensory ligament is attached to the
capsule of the lens at the other end.
• Contraction or relaxation of the ciliary
muscle changes the thickness of the lens accommodation
• The ciliary body is supplied by
parasympathetic branches of the oculomotor
nerve.

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Use of Anesthetics in Ophthalmic
Procedures
Topical anesthetic agents used clinically in
ophthalmology include cocaine,
proparacaine and tetracaine drops and
lidocaine gel
Proparacaine and tetracaine are used
topically
• to perform tonometry, to remove foreign
bodies on the conjunctiva and cornea, to
perform superficial corneal surgery.
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• and to manipulate the nasolacrimal
canalicular system.
• to anesthetize the ocular surface for
refractive surgery using either the excimer
laser or placement of intrastromal corneal
rings.
Cocaine
• for cannulating the nasolacrimal system.
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Lidocaine and bupivacaine:
• are used for infiltration and retrobulbar
block anesthesia for surgery.
• Potential complications and risks relate to
allergic reactions, globe perforation,
hemorrhage, and vascular and subdural
injections.

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• Preservative-free lidocaine (1%): which
is introduced into the anterior chamber,
and
• lidocaine jelly (2%): which is placed on
the ocular surface during preoperative
patient preparation, are used for
• cataract surgery performed under topical
anesthesia.

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Dacryoadenitis
• an infection of the lacrimal gland, common in
children and young adults
It may be bacterial:
• typically Staphylococcus aureus, Streptococcus
species) Or
viral (most commonly):
• mumps, infectious mononucleosis, influenza,
and herpes zoster.
• In infants and children,
• the disease usually is unilateral and secondary to
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an obstruction of the nasolacrimal duct.


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• In adults, dacryocystitis and canalicular
infections may be caused by:
• S. aureus, Streptococcus species,
• Diphtheroids, Candida species, and
Actinomyces israelii.
• Any discharge from the lacrimal sac
should be sent for smears and cultures.
• Systemic antibiotics typically are
indicated.
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Infectious processes of the eyelids include

hordeolum and blepharitis.
Hordeolum (stye)
• A hordeolum, or stye, is an infection of the
meibomian, Zeis, or Moll glands at the
eyelid margins.
Bacteria Involved:
S. aureus, and the usual treatment consists of
warm compresses and topical antibiotic
ointment.
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Blepharitis
• Blepharitis is a common bilateral
inflammatory process of the eyelids:
• Iritation and burning
• Staphylococcus species:
• Local hygiene is the mainstay of therapy;
topical antibiotics frequently are used,
usually in ointment form,
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Keratitis is a condition in which the eye's cornea, the
front part of the eye, becomes inflamed. The condition
is often marked by moderate to intense pain and
usually involves impaired eyesight. May cause feelings
of scratching each time individual blinks eye.

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Treatment: Blepharitis with
conjunctivitis and keratitis
• Systemic tetracycline, doxycycline,
• minocycline, and erythromycin
• often are effective in reducing
severe eyelid inflammation,
• but must be used for weeks to
months.
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Conjunctivitis
Conjunctivitis is an inflammatory process of
the conjunctiva that varies in severity from
mild hyperemia to severe purulent discharge.
Common causes:
• Viruses, allergies, environmental irritants,
contact lenses, and chemicals.
• Less common causes include other infectious
pathogens, immune-mediated reactions,
associated systemic diseases, and tumors of
the conjunctiva.
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CHLORAMPHENICOL:
• (AK-CHLOR, 0.5% solution, H, BD
Conjunctivitis, keratitis

CHLOROMYCETIN, CHLOROPTIC:
• 1% ointment

Ciprofloxacin hydrochloride:
• 0.3% solution, H, D-RCD Conjunctivitis,
keratitis
• (CILOXAN)
• 0.3% ointment
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Erythromycin (ILOTYCIN) 0.5% ointment H
Blepharitis, conjunctivitis

Gatifloxacin (ZYMAR) 0.3% solution H
Conjunctivitis

Gentamicin sulfate (GARAMYCIN, 0.3%
solution, H Conjunctivitis, blepharitis,
GENOPTIC, GENT-AK, GENTACIDIN) 0.3%
ointment keratitis
Levofloxacin (QUIXIN) 0.5% solution H
Conjunctivitis
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• Levofloxacin (IQUIX) 1.5% solution H
Conjunctivitis, keratitis
• Moxifloxacin (VIGAMOX) 0.5% solution H
Conjunctivitis
• Ofloxacin (OCUFLOX) 0.3% solution H
Conjunctivitis, keratitis
• Sulfacetamide sodium 10, 15, 30% solution,
H, BD Conjunctivitis, keratitis

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ANTIVIRAL AGENTS
• The primary indications for antiviral
drugs in ophthalmology are

• viral keratitis
• herpes zoster ophthalmicus,
• retinitis
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