Ophthalmology

The Eyes
Much of the information we receive from the world around us comes through our eyes. They help us
to interact with our world. The study of the structure, disease and refractive errors associated with the
eye is termed ophthalmology. Ophthalmology is also concerned with diseases and refractive errors
associated with the eyes. Refractive errors cause our vision to be less than perfect and are commonly
treated with corrective lenses. A physician who specializes in these areas of medicine is called an
ophthalmologist. An optometrist is a licensed medical professional who specializes in the
examination of the eyes and the diagnosis and correction of refractive errors through the use of
corrective lenses.

THE STRUCTURE OF THE EYE

A bony cavity made up of portions of several cranial bones forms the orbit (eye socket), the structure
in which the bulb of the eye is located. The eye is spherical in shape and has three layers. The white
part of the eye is the sclera and forms the tough, protective outer layer of the eye. The middle layer is
the choroid, which provides the eye’s blood supply. The innermost layer is the retina. It contains the
nerve endings that receive light and, in response, transmit this information to the brain. Light enters
each eye through the pupil, the dark center of the eye. Actually, the pupil is an opening into the eye
itself. The iris, belonging to the middle layer, is the colored portion of eye surrounding the pupil.

The iris controls how much light enters through the pupil by dilating the pupil in dim light and
constructing it in light. Irises can be brown, blue, gray, hazel, green or various combinations of these
colors. The cornea is a transparent portion of sclera that extends over the pupil. It is directly in fornt
of the lens and focuses light through the lens onto the retina at the back of the eye. The lens is held in
place by special muscles called the ciliary body. As these muscles relax and contract, they make the
lens thicker to thinner. This process is referred to as accommodation and causes light rays to be
properly focused on the retina. Figure 10-1 illustrate the process of light entering the eye and being
focused on the retina.

The eye contains two major humors. Or fluids. The aqueous humor is contained in the aqueous body,
which is the part of the eye in front of the lens. The iris divides the aqueous body into an anterior
Chamber and a posterior chamber. The posterior chamber continually produces aqueous humor. This
fluid is drained into the vascular system from the eye by a duct named the canal of Schlemm, which is
located near the anterior chamber. The other major humor is the vitreous humor and is contained in
the vitreous body, the part of the eye behind the lens. Both aqueous humor and the vitreous humor,
along with lens, are capable of refracting light.

The retina has two types of visual receptors, rods and cones. Cones function in bright light and can
produce color vision. Rods work in dim light and are capable of producing only black and white
vision, including various shades of gray. Both rods and cones contain chemicals called
photopigments. These chemicals undergo a change when light strikes them, stimulating the rods and
cones and causing nerve impulses to be transmitted through the optic nerve to the brain. The brain
interprets these impulses to provide us with vision.

The eyes must work closely with the brain to provide us with sight. If either one is functioning
improperly, our vision may be impaired. As you can see in Figure 10-2, the optic nerve enters the eye
at an area called the optic disk. The centre of the optic disk is referred to as the blind spot because
there are no rods or cones in this area. Lateral to the optic disk is an oval area of the retina called the
macula that corresponds to the posterior pole of the eye. The posterior pole is the intersection point of
the retina with the optical axis of the eye. The fovea centralis is a slight depression in the centre of
the macula, where the retina is very thin. This is the area in the eye where vision is most perfect. The
eyes are protected and moisturized by the eyelids, the movable folds of skin above and below each
eyeball. The conjunctiva is a thin mucous membrane that covers the exposed part of the sclera (expert
for the cornea) and the inner surface of the eyelid. The lid’s eyelashed protect the eye from dust and
other small airborne particles. The lacrinmal glands, which are superior and slightly lateral to the
centre of the eye, procedure tears, which bathe and lubricate the eye. Lacrimal ducts transport the
tears to the superolateral portion of the conjunctiva. Most of this fluid evaporates, but some of it
collects at the medial angle of the eye, also called the medial canthus. The fluid then travels through
pinpoint openings called the lacrimal puncta into the lacrimal canals.

The lacrimal canals empty into the lacrimal sac, which actually forms the superior portion of the
nasolacrimal duct. The nasolacrimal duct empties into the nasal cavity, and this process accounts for
why crying leads to congestion. Figure 10-3 illustrates the lacrimal apparatus. Six skeletal muscles,
called extrinsic eye muscles, control the movement of each eyeball. These muscles orginate from the
posterior orbit and allow the eyeball to be rotated. The superior, inferior, medial and lateral rectus
muscles insert at the corresponding portions of the eyeball that each name indicates. The superior and
inferior oblique muscles travel at an angle to the long axis of the eyeball. By working in unison, these
two additional muscles allow the eyeball to be rotated to adjust the direction of the gaze.
EXAMINING THE EYES
When examining the eyes, an ophthalmologist inspects not only the eyeballs, but also the surrounding
tissues such as the eyelids, eyebrows, and eyelashes. The patient is asked about any pain, unusual
redness, discharge, or changes in vision. The eyelids are examined for growths, foreign bodies, and
inflammation. The sclerae are checked for discoloration. A yellowish color can indicate jaundice,
which may be symptomatic of a liver disorder. A bluish tinge can be indicative of some types of
connective tissue disorder. When the examiner palpates the eye with the lids closed, the eye should
feel firm and bouncy.

The pupils are inspected for size, equality and regularity. To test the pupils for reaction to light, the
examiner shines a bright light oblique into each pupil and observes whether the opposite eye also
constricts (referred to as direct reaction) and whether the opposite eye also constricts (referred to as
consensual reaction). The examine tests for accommodation by requesting the patient to look at a
distant object and observing whether the pupils constricts.

Extraocular movement is tested by having the patient follow a hand-held object with the eyes while
keeping the head immobile. The examiner notes whether the eyes move in unison and properly track
the moving object. Abnormalities of extraocular movement can be to an imbalance in the muscles
controlling eye movement (strabismus), an orbital disease or injury, or injury to the third, fourth, or
sixth cranial nerves. The examiner may instruct the patient to perform additional exercise such as
squinting or raising and lowering the eyebrows to check for proper neuromuscular functioning.

An ophthalmoscope is used to examine the macula, optic disk and the bold vessels in the retina. This
handheld devise supplies both magnification and illumination, allowing irregularities to be viewed.
Special drops may be used to dilate the pupil making it easier to see the eye’s posterior structures.
For the sake of brevity and clarity, many physicians specify locations on spherical structures such as
the eye by using the “o’ clock” method. As seen by the physician, the position is specified by
approximately the hour position to which the location would be closest if the patient’s eye were the
face of a clock. For example, an abrasion at the lateral border of the cornea of the right eye would be
at the 9 o’clock position. A physical examination typically includes screening for visual acuity.

Figure 10-3 Lacrimal Apparatus

A snellen eye chart (Figure 10-4) may be used and consists of lines of letters that become
progressively smaller as the reader goes down the chart. Each line is labeled with a number such as
20, 30, 40, etc. While seated 20 feet from the chart, the person being tested attempts to read the
smallest line he or she can. If the individual can read the line labelled 20, vision is said to be 20/20.
If the smallest readable line is labelled 40, the Snellen notation is 20/40. This means that the
individual must be 20 feet from an object in order to see it as well as a person with “normal” (20/20)
vision can see it from 40 feet. Near vision is usually tested by requesting the patient to read a
handheld card containing text or letters with increasingly smaller print. Two such card system are the
Jaeger eye chart and the point system eye chart.

(Figure 10-4)

Mascular degeneration is tested with an Amsler chart. An Amsler chart is a 10-cm square grid. If
defects in the central visual field exists, the grid lines appear distorted when viewed by the patient.
The visual field is the total area in which objects can be seen while the eye is focused on a central
point. A visual field test, also known as the visual fields confrontation test, is an examination of
peripheral vision.

The patient notes when an object, usually the examiner’s finger or pen, moving from outside the
visual field becomes viewable. If the patient exhibits deficiency during this rough kinetic testing,
quantitative perimetry may be performed. This test, along with other tests such as those for the
abnormal conditions of glaucoma and macular degeneration, are covered later in this chapter under
the heading Common Diagnostic Tests and Procedures.

CONDITIONS AFFECTING VISUAL ACUITY

The most common problem with eyes is a lack of visual acuity. This problem occurs when light rays
do not focus sharply on the retina due to ametropisa (a refractive error). Refractive errors can be
caused by an imperfectly shaped cornea or lens. In addition, the eyeball itself may be improperly
shaped. Table 10-1 defines terms associated with refractive errors.

TABLE 10-1 Refractive Errors

Conditions or Disease Desscription
ametropia Light rays do not focus sharply on the retina sue
to an error of refraction. The items listed below
in this table are examples of ametropia. It can
be caused by ab imperfectly shaped corena, lens
or eyeball.
anisometropia A significant difference between the refractive
powers of an individual’s two eyes.
astigmatism Light rays are bent unequally by an eye’s
various refractive components such that proper
focusing of light rays at a single point on the
retina is prevented. Astimatism is caused by an
equal curvature of the cornea and/or lens.
hyperopia The curvature of the cornea is too shallow or the
 eyeball is too short. When the light passes
through the cornea, it is focused behind the
retina. Also called farsightedness.
myopia The curvature of the cornea is too step or the
eyeball is too short. When light passes through
the cornea, it is focused in front of the retina.
Also called nearsightedness.
presbyopia The gradual loss of accommodation by the lens
typical of the aging process. A form of
farsightness that starts when a person is around
40 to 45 years of age.

DISASES AND CONDITIONS OF THE EYES

Disease and conditions of the eye involve not only the eyeball but also those structures surrounding it,
including the eyelids and the tear ducts. Some abnormal conditions of the eyes and surrounding tissue
are relatively minor. One of these is conjuctivits, in which in which one or both of the conjuctivae
become inflamed or infected, causing discharge and extreme itching (pruritus). In its acute
contagious form, conjunctivitis is commonly called pinkeye. Such localized problems typically
respond readily to treatment.

However, other eye conditions such as glaucoma can be serious. The term glaucoma refers to a
group of conditions in which the optic nerve has been damaged, reducing its ability to transmit images
to the brain. This damage is frequently caused by abnormally high intraocular pressure (IOP).
Glaucoma can be categorized as either open-angle or angle-closer glaucoma. In open glaucoma,
intraocular pressure is increased due to the failure of aqueous humor to properly drain from the eye
through the canal of Schlemn, This improper drainage occurs even though examination shows no
problem with the physical structures of the eye. In angle-closer glaucoma, an actual physical
obstruction is causing improper drainage. Open-angle glaucoma has no known cause and is chronic.
It accounts for about 65% of all cases of glaucoma. Angle-closure glaucoma can be chronic or acute.

In the acute from, the pressure can quickly become extremely high and the optic nerve can be
damaged within a few hours. Treatment must be immediate in order to avoid permanent damage.
The term strabismus is used when referring to any defect in eye muscles that makes the eyes unable to
focus on the dame point at the same time. Strabismus can be divided into two categories:
nonparalytic strabismus (which is caused by an imbalance in the tone of the ocular muscles) and

TABLE 10-2 Ophthalmologic Diseases and Conditions

Conditions or Disease Description
achromatopsia A sereve lack of ability to perceive colors. This conditions is typically
inherited and is more common in men than women. Also called color
blindness.
ampblyopia Poor vision in one eye leading to diminished use of the eye. In children,
this is often referred to as “lazy eye syndrome” in which vision is
weaker in one eye. The child tends to relay on the other eye for vision.
It is usually treated by placing a patch over the stronger eye.
blepharitis Inflammation of the margins of the eyelid causing them to thicken and
become red.
bullous keratopathy A condition caused by edema (swelling) of the cornea. Bullae appear on
the surface of the cornea, decreasing vision. If the bullae rupture,
infection and corneal ulcer can results.
cataract A clouding of the lens of the eye causing a painless and progressive loss
of vision. The most common cause is aging, typically beginning with
 gradual vision in middle age. However, cataracts can also be caused by
other factors including disease such as diabetes mellitus and
inflammatory conditions such as uveitis.
chalazion A small hard mass on the eyelid caused by chronic inflammation of a
sebaceous gland.
chemosis Edmea that caused swelling around the cornea.
conjunctivitis Inflammation of one or both conjuctivae. May be caused by allergies,
viruses, or bacteria. It can be caused by conditions such as ectropion,
entropion and blepharitis.
corneal ulcer Necrosis of the corneal tissue caused by bacteria, viruses, or fungal
infections. It can also be caused by invasion of Acanthamoeba, a genus
of ameba.
corneitis Inflammation of the cornea.
Cytomegalovirus Infection by the cytomegalovirus which may manifest as retinitis, fever,
infection pneumonia and hepatitis. It is most commonly seen in individuals with
AIDS.
dacryostenosis A stricture (narrowing) of a lacrimal canal or the nasolacrimal duct. It
can be congential or the result of an infection.
diplopia Double vision. It occurs when the brain fails to merge the images seen
by each of the eyes.
ectropion Eversion of the border of the eyelid. Typically results from the aging
process and may result in poor drainage of tears.
entropion Inversion of the border of the lower eyelid. Can result from the aging
process or the formation of scar tissue. Entropion causes the eyelashes
to rub against the eyeball, which can leads to corneal ulcers and scaring.
epiphora An overflowing of tears onto the cheek caused by inadequate drainage.
episclaritis Inflammation of the episclera, which is the connective tissue between
the conjunctiva and the scelra.
esotropia Medial rotation (inward turning) of an eyeball. This is a type of
strabismus.
exophthalmos Protusion of the eyeballs. It can be either congential or due to injury,
edema or other pathological conditions
floater Macroscopic mass of vitreous fibres that appear as a spot before one or
both eyes. It results from contraction of the vitreous humor which
separate from the surface of the retina. Also known as vitreous debris.
glaucoma Damage to the optic nerve frequently caused by abnormally high
intraocular pressure. It leads to partial vision loss and eventual
blindness. It can be categorized as open-angle (in which there is no
known cause) and angle-closure (in which there is a physical cause of
the improper drainage of the aqueous humor).
hemianopsia Lack of vision in half of the visual fields. This conditions occurs in
some stroke victims.
hypertropia Superior rotation of one eyeball. A type of strabismus in which one
eyeball is turned upward.
hyphema Blood in the anterior chamber of the eye, most commonly caused by
injury.
hypotropia Inferior rotation of one eyeball. A type of strabismus in which one
eyeball is turned downward.
keratitis An inflammation of the cornea. It has many causes including
conjunctivitis, blepharitis, trachoma and excessive exposure to
ultraviolet light.
keratoconus A thinning of the cornea that is typically discovered between ages 10
and 20. It leads to visual distortion and usually requires surgery.
macular degeneration Damage to the macula resulting in loss of central visual acuity. Tested
 with an Amsler chart. It is the most common cause of visual
impairment in individuals over age 65.
nyctlophia A decrease in the ability to see in limited light. Also called night
blindness.
nystagmus Involuntary movements of the eyeballs.
ocular hypertension Excessively high intraocular pressure.
optic neuritis Inflammation of the optic nerve.
orbital cellulities Inflammation of the tissue of the orbit. It may be caused by an infection
in a nearby structure such as the teeth or nasal sinuses or by infection
resulting from a trauma.
papilledema Swelling of the optic disk that is usually caused by abnormally high
intracranial pressure.
papillitis Inflammation or reduction of blood agioussupply to the optic disk. It
can cause chronic glaucoma. Viewable by an ophthalmoscope.
photophobia An ususual inability to tolerate light.
pinkeye Contagious conjunctivitis.
pterygium A triangular fleshy growth of the conjunctiva onto the cornea. It is most
commonly seen in hot, dry climates. Also called web dry.
ptosis A sagging, or prolapase, of an upper eyelid. This term can be used to
describe the sagging of any body part.retini
retinal detachment A separation of the neurosensory part of the retina (the part containing
the rods and cones) from the epithelial layer (the part containing blood
vessels).
retinitis Inflammation of the retina. Cytomegaloviruss is its most common
cause.
retinitis pigmentosa A chronic progressive disease that cause the retina to degenerate and the
optic nerves to atrophy, leading first to night blindness and losts of
peripheral vision and eventually to complete blindness.
retinopathy Any noninflammatory degenerative disorder of the retina. Causes
include hypertension, diabetes mellitus and reduction of blood flow to
the retina.
Rhegmatogenous retinal Retinal detachment caused by small rips and tears of the retina. It is
detachment most.
scleritis A sever inflammation of the sclera which can lead to blindness if left
untreated.
scotoma A small area to irregular size and shape in the eye’s visual field where
vision is absent or abnormal. A negative scotoma cause a blind spot.
Negative scotomas may be caused by retinal haemorrhage, swelling,
detachment or by improper functioning of the optic nerve. A positive
scotoma is seen as a light spot or flashes of light and may be caused by
migraines.
strabismus A defected in eye muscles that makes the eyes unable to focus on the
same point at the same time. The visual axis of one eye is not parallel
to the visual axis of the other eye.
stye(or sty) An acute, pus-forming infection of the eyelid most commonly caused by
the bacteria Staphylococcus aureus. Styes are often associated with
blepharitis and may be recurrent. Also called a hardeloum.
trachoma An infection disease caused by the organism Chlamydia trachomatics.
It is a type of conjunctivitis that worsens over several weeks and can
eventually lead to blindness. It is the world’s leading cause of blindness
and is common in North Africa, India, Southeast Asia and the Middle
age
uveal melanoma Carcinoma of the uvea, the part of the eye containing the iris, choroid
and ciliary body.
uveitis An inflammation of the iris, ciliry body or choroid.
xanthopsia A condition in which everything seen appears to be yellow. Can be
caused by jaundice or certain types of poisoning.

COMMON DIAGNOSTIC TESTS AND PROCEDURES

Many of the diagnostic tests discussed in this section are performed because abnormilites were found
during a routine vision examination. For example, if the patient does poorly on a visual field tests,
quantitative perimetry may be performed to more accurately diagnose any abnormality. Quantitative
perimetry plots the limits of the visual field using a globelike device called a perimeter.

For individuals who performed below normal on a general visual acuity test, a refraction test helps in
diagnosing refractive errors and in determining the strength and type of corrective lenses that can best
correct them. Typically, the individual looks through a device called a Phoropter at a Snellan eye
chart that is 20 feet away. The phoropter contains different strengths of lenses that can be switched by
the examiner until 20/20 vision is achieved. This information provides a prescription for the
necessary corrective lenses.

Eye structure such as the iris and cornea may be examined using a slitlamp. The slitlamp (also called
a biomicroscope) combines a magnifying device with a high-intensity light beam that can be focused
so that it is projected as a narrow slit. The slitlamp has two eyepieces through which the patient
looks. Both the magnification and the intense light beam help in identifying any problems with eye
structures. The size and shape of the pupils are checked along with their ability to accommodation
and react to light. A special orange-colored dye called abnormalities such as corneal abrasions.

If cataracts are presented their extent location can also be assessed during this exam. The dye is
naturally washed out of the eye by tears. Ordinarily, the examiner can only see the anterior part of the
eyeball. However, special drops can be used to dilate the pupils, allowing the interior posterior
surface of the eyeball, the fundus, to be examined. Tonometry is the measurement of intraocular
pressure and is important because high intraocular pressure can be indicate of glaucoma. Two
commonly used methods as Schiotz tonometry and Goldmann applanation tonometry. Table 10-3
summarizes common diagnostic tests and procedures associated with the eyes.

TABLE 10-3 Common Diagnostic and Procedures in Ophthalmology

Test Description
Amsler chart test Use of the Amsler eye chart to detect central field abnormalities due to
macular disease.
bacterial culture The propagation of samples of purulent tissue in or on laboratory media
and observation to verify of bacteria are present. If so, the type of bacteria
is deremined. Ised to diagnose bacterial conjunctivitis.
Electonystagmograp Recording and testing for nystagmus (involuntary eye movements) using
hy skin electrodes and an electric current.
fluorescein staining Application of a chemical dye to the surface of the eye, which, when
viewed under ultraviolet light, will indicate corneal abrasions.
gonioscopy An examination to determine whether glaucoma is open angle or angle
closure using a sliptlamp and a special prism contact lens or a gonioscope.
ophthalmoscopy Examination of the fundus, including the optic disk, the macula, the fovea
centralis and fundal blood vessels using an ophthalmoscope. Also referred
to as funduscopy.
perimetry Measurement and plotting of the limits of the visual field. A perimeter is
the instrument used.
pupiloscopy Examination to measure the distance between the centres of the pupils.
The instrument used in pupilostatometer.
retinoscopy Examination for refractive errors determined by using a light (a
retinoscope) to illuminate the retina and then observing how the light rays
emerge from the eye.
tonometry Measurement of the pressure of the fluid inside the eye (intraocular
pressure). This information is useful in diagnosing glaucoma. A
tonometer is the instrument used.
ultrasonography Recording of the location of retinal tumors, detachments of the retina and
vitreous hemorrhages ultrasound equipments.
visual acuity test Examination to determine how an individual’s vision varies from a
standardized norm. Snellan charts and handheld charts are commonly
used.
visual fields test, Examination to determine the total area in which objects can be seen while
visual fields by the eye is focused on a central point.
confrontation test

PHARMACOLOGY
Most ophthalmic drugs fall into the classifications shown in Table 10-4. Topical anesthetics are used
to reduce the discomfort of eye examination and sensitive procedures such as removing small foreign
objects from the eye. Mydriatics are used to dilate the pupils, making it easier to examine the interior
of the eyes. Anti-inflammatory drugs are used to treat the inflammation resulting from trauma,
allergies or surgery. Drugs used to treat glaucoma fall into several categories. Miotics cause the pupil
to constrict, allowing the aqueous humor to flow more freely. Carbonic anhydrase inhibitors, beta
blockers and similar drugs work by reducing the amount of aqueous humor that is produced. Table
10-5 list many of the commonly used ophthalmologic drugs.

TABLE 10-4 Classifications of Ophthalmologic Drugs

Classifications Usage Examples
anti-inflammatory Topical treatment of inflammation diclofenac, ketorolac
resulting from trauma, allergic or surgery.
antiviral Treatment of conditions such as herpes vidarabine, cidofovir,
simplex and cytomegalovirus infections by cytomegalovirus
inhibiting the reproducing of viruses. immunoglobulin, foscarnet,
ganciclovir
corticosteroid Tropical treatment of inflammation and dexamethasone,
edema resulting from trauma, allergic, prednisolone
surgery or conjunctivitis. Also used for
inflammatory conditions such as scleritis
and episcleritis and some types of
papillitis.
mydriatic Temporary dilation of pupils to aid in atropine, cyclopentolate,
examination the interior of the eye. homatropine, phenylephrine,
scopolamine

TREATING REFRACTIVE ERRORS

Prescribing corrective lenses commonly treats errors in refraction. These lenses may be placed in
eyeglasses or they may be incorporated into contact lenses. Contact lenses can be made of either rigid
(hard) or soft plastic material. They are placed onto the eyeball itself over the cornea. Surgery may
also be used to correct many of the defects that cause refractive errors. This surgery can be performed
with a blade or with a laser. Table 10-6 contains a listing of surgical procedures used to correct
refractive errors.
TABLE 10-6 Surgical Procedures for Refractive Errors
Conditions or Disease Description
astigmatic keratotomy Making microscopic incisions in the eye to correct a
misshapen cornea. Used to correct or reduce astigmation.
LASIK (laser in situ Using an Excimer laser to permanently correct myopia,
keratomileusis) astigmatism or hyperopia. A flap of corneal tissue is
elevated and the laser in used to change the shape of the
cornea under the flap. The flap is then replaced.
photorefractive keratectomy (PRK) Using an Excimer laser to permanently correct the vision of
individuals with a low to moderate degree of myopia. The
laser is used to remove and flatten part of the central cornea.
radial keratotomy (RK) Making a series of microscopic incisions in a spokelike
pattern to flatten the cornea and cause light to focus more
precisely on the retina. RK is used with individuals having a
low to moderate degree of myopia.

THERAPEUTIC PROCEDURES
A procedure that has become relatively common is cataract removal. In the early stages of cataract
development, the patient typically requires changes in lens prescriptions. Once vision is impaired to
the point that it interferes with normal activities, the cataracts. One method id intracapsular
extraction. A cryoprobe (a metal probe cooled to an extremely low temperature) is placed on the
cataract, causing it to bond to the probe so that the cataract and lens can be removal in one piece. This
method is rarely used today. Extracapsular extraction removes the cataract and lens, but leaves the
part of the lens capsule closest to the eye.

A third method is phacoemulsification, in which ultrasonic vibrationic vibrations ate used to fragment
the lens capsule. As with extracapsular extraction, this procedure leaves the posterior lens capsule.
The lens is usually replaced with a plastic intraocular lens. Corneal transplants are used when the
cornea becomes opaque or is scarred. This may occur in conditions such as bullous keratopathy.
Keratoconus and keratitis. These transplants are successful because the cornea does not contain blood
vessels or antibodies that might reject foregin tissue.

In most instance, drugs treat glaucoma. However, when pharmaceutical treatment is inadequate,
surgical intervention may be required. There are a number of surgeries used to alleviate the
intraocular pressure typically associated with glaucoma. Table 10-7 lists some of them along with
other procedures used in ophthalmology.

TABLE 10-7 Therapeutic Procedures Used in Ophthalmology

Procedures Description
blepharectomy Excising a growth on the eyelid.
cataract removal There are several methods of cataract removal. In intracapsular extraction,
the entire lens is removal as a single unit. In extracapsular extraction, the
hard central part of the lens is removed and the soft outer part is then
removed in pieces by aspiration or phacoemulsification.
Phacoemulsification uses ultrasound along with aspiration and irrigation to
break up and remove the lens. In both extracapsular extraction and
phacoemulsification, the posterior capsule of the lens is not removal.
corneal transplant The diseased part of the cornea is removed. It is replaced with a healthy
cornea from a donor. The replacement cornea should be similar in size and
shape to the recipient’s damaged cornea. This procedure is used when vision
is diminished because of cataracts, corneal scarring, etc.
cyclodialysis Surgically creating an opening between the anterior chamber and the space
above the choroid to drain the aqueous humor and reduce intraocular
 pressure. Used in the treatment of glaucoma.
dilation of the Using a series of successively larger probes to enlarge the lacrimal canal to
lacrimal canal allow proper drainage of tears.
enucleation Surgically removing an eye. This term can also refer to the surgical removal
of a tumor.
evisceration Surgically removing the contents of the eye, but leaving the sclera and
possibly the cornea.
goniopuncture Surgically puncturing the peripheral iris to allow for drainage of aqueous
humor. Used for congential glaucoma.
implantation of After the removal of a damaged lens, such as with cataracts, inserting an
intraocular lens intraocular lens made of plastic.
iridodialysis Separating the iris from its attachments at the origination of the ciliary
muscle fibres. This procedure may be used to reduce intraocular pressure.
keratocentesis Surgically puncturing the cornea, used to drain aqueous humor.
keratoplasty Surgically reshaping the cornea. This term os often used when referring to
corneal transpants.
laser peripheral Using a laser to excise a small portion of the iris. This procedure is used in
iridectomy angle-closer glaucoma to reduce intraocular pressure.
laser peripheral Using a laser to cut a small opening in the periphery of the iris. It is used for
iridotomy two purposes: To increase drainage of aqueous humor in glaucoma and to
create a new pupil to improve visual acuity in cases where the lens had
become opaque, for example, in the presence of cataracts.
laser Using a laser to excise a small portion of the eye’s filtering (trabecular)
trabeculectomy meshwork to reduce pressure in severe glaucoma.
laser Using a low-frequently ultrasonic needle to emulsify and aspirate a cataract.
trabeculoplasty The posterior capsule of the lens is not removed.
phacoemulsification Using a low- frequently ultrasonic needle to emulsify and aspirate a cataract.
The posterior capsule of the lens is not removed.
repair of a detached Reattaching the retina to the choroid. Several techniques are used including
retina diathermy coagulation, which uses a high-frequently current and
cryosurgery, which uses extreme cold.
sclerostomy Surgically creating an opening in the sclera. This process is sometimes used
to relieve excessive intraocular pressure.
seton procedure Placing a tube in the anterior chamber to decreases intraocular pressure by
draining fluid.
sphincterotomy Cutting the sphincter muscle in the iris to allow the pupil enlarge.

Abbreviations
Abbreviation Meaning
ACC, accom accomadation
D dioptre (a unit of refracting power in an eyeglass prescription)
Em emmetropia
ENG electronystagmography
EOM extraocular movements
IOL intraocular pressure
L&A light and accommodation
LASIK laser in situ keratomileusis
myop myopia
OD oculur dexter (Latin) meaning right eye. Also doctor of optometry.
OS oculur sinister (Latin) meaning left eye.
OU oculur uterque (Latin) meaning each eye or both eyes.
PAM potential acuity meter
PERRLA pupil are equal, round and regular and react to light and accommodation
PRK photorefractive keratectomy
REM rapid eye movement
RK radial keratotomy
ST esotropia
VA visual acuity
VF visual field
XT exotropia

Combining Form for Terms Used in Ophthalmology

Form Meaning Example(s)
ambly/o dim; dull (eye condition) amblyopia
blephar/o eyelid blepharitis, blepharectomy
chororis/o choroid (layer of the eye) choroid
conjuctive/o conjunctiva conjunctiva, conjunctivitis
corne/o cornea corneitis, cornea, corneal
dacry/o tears (see also lacrim/o) dacryostenosis
glauc/o gray glaucoma
irid/o iris iridodialysis, iridectomy
kerat/o hard; horny tissue; cornea keratopathy, lacrimation
lacrim/o tears (see also dacry/o) lacrimal, lacrimation
ocul/o eye (see also ocul/o, optic/o, ophthalm/o) ocular, extraocular
ophthalm/o eye (see also ocul/o, opt/o, optic/o) ophthalmology,
ophthalmologist
opt/o eye; vision (see also ocul/o, ophthalm/o, optometrist, dioptre
optic/o)
optic/o eye; vision (see also ocul/o, ophthalm/o, opticopupilllary, optic nerve
opt/o)
phot/o light photopigments, photoreactive
pupil/o pupil pupillometer, pupilloscopy
retin/o retina retinitis, retinopathy
scler/o hardness scleritis