The_Ophthalmology_Examinations_Review (WONG)

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What Every Eye Doctor Needs to Know About Low Vision

Review_Questions_in_Ophthalmology for Resedints

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Differentiating Glaucoma from Other Optic Neuropathies

Management of Suprachoroidal Hemorrhage

ppv(internal limiting mem. peeling for macular hole )

How to Avoid Missing an Open Globe

Conjunctivitis, Acute and Chronic

when to operate ?-which operation?

OCULAR ANATOMY AND HISTOLOGY

- Concepts for Diagnosis

Examination Techniques for the Beginner

The Glaucoma

Glaucoma :

is a disease of the optic nerve most
likely due to a compromised blood supply.
The nerve can be damaged even more by elevated
intraocular pressure pushing on the
blood vessels supplying the nerve and causing
a further reduction in blood flow.
Intraocular pressure is maintained by a balance
between aqueous inflow and outflow. The
aqueous produced by the ciliary body passes
from the posterior chamber (the space behind
the iris) through the pupil into the anterior
chamber . It drains through the trabecular
meshwork and out of the eye through
the venous canal of Schlemm.

Glaucoma vs. glaucoma suspect :

Normal intraocular pressure is 10–20 mmHg
and should be measured at different times of
day as there is a diurnal rhythm. Pressure
greater than 28 mmHg should be treated to
prevent loss of vision. Treat pressures of 20–27
mmHg when there is loss of vision, damage to
the optic nerve, or a family history of glaucoma.
Patients with pressures of 20–27 mmHg
without these findings are called glaucoma
suspects and are followed, but not treated.
Infrequently, the optic nerve could be damaged
even when the pressure is less than 20
mmHg (normal tension glaucoma) and must
be further reduced to the low teens.
Several instruments can be used to indirectly
measure intraocular pressure by indenting
the cornea.
A Goldmann applanation tonometer is the most accurate. It is used in conjunction
with a slit lamp, and requires the use of anesthetic
drops and fluorescein dye.
A Schiötz tonometer is a portable instrument that indents the anesthetized
cornea and is used for bedside measurements.

The air-puff tonometer tests the pressure by
blowing a puff of air at the eye. It is used by
technicians since it does not require eye drops
or corneal contact.
With all three instruments, the tonometric
pressure reading is only an estimate of the
real pressure. A thick cornea requires extra
force to indent and, therefore, gives a falsely
elevated reading, and the opposite is true
with thin corneas. To better approximate
the real pressure—especially in glaucoma
suspects where exactitude is important—an
ultrasonic pachymeter is used to measure
corneal thicknessA conversion factor for
corneal thickness then adjusts the tonometric reading upward or downward.

THE ORBIT

THE ORBIT   
The orbit is a cone-shaped vault . At its apex are three orifices through
which pass the nerves, arteries, and veins supplying
the eye.

Clues that may indicate disease
of the orbit :

A. Proptosis (exophthalmos)—forward bulging
of the eye.
B. Enophthalmos—sunken eye.

C. Swollen lids (sometimes totally shut);
redness and engorgement of conjunctival
vessels; clear fluid under conjunctiva (chemosis).

D. Loss of eye movement (ophthalmoplegia)
due to involvement of cranial nerves III, IV,
and VI or local damage to extraocular muscles.
Orbital cellulitis causes the lids to be swollen
shut (Fig. 154). The globe may not move (ophthalmoplegia)
and there is chemosis, fever,
adenopathy, and exophthalmos. It is most
often due to sinusitis, but also occurs with
tooth, facial or lid infections.
An orbital septum connecting the lid tarsal
plates to the orbital rim  acts as
a barrier protecting the orbit from lid infections.
Beware of the rare breakthrough.
Orbital cellulitis can spread to the cavernous
sinus through the superior and inferior ophthalmic
veins that drain the orbit and part of
the face. This could cause thrombosis and
death. Rx: hospitalize the patient and treat
with systemic antibiotics.
Orbital fat may migrate under the conjunctiva or herniate through the septum
under the skin. This is only a cosmetic
problem.

Strabismus

Strabismus
refers to the nonalignment of the
eyes such that an object in space is not visualized
simultaneously by the fovea of each
eye. Phoria refers to the potential for an eye
to turn. Once it turns it is called a tropia.

Causes of strabismus

1 Paralytic strabismus is due to cranial nerve
(III, IV, or VI) disease or eye-muscle weakness
from thyroid disease, traumatic contusions,
myasthenia gravis, or orbital floor fractures.
2 Nonparalytic strabismus is due to a malfunction
of a center in the brain. It is often
inherited and begins in childhood.

Complications of strabismus:

1. Amblyopia
Also called lazy eye, amblyopia is decreased
vision due to improper use of an eye in childhood.
The two common causes are an eye turn
(strabismic  amblyopia) or a refractive error
(refractive amblyopia), uncorrected before age 8. In strabismus, children unconsciously
suppress the deviated eye to avoid diplopia.
Strabismic amblyopia is treated by patching
the good eye , thereby forcing the
child to use his amblyopic eye. The better eye
is patched full time—one week for each year
of age. It is repeated until there is no
improvement on two consecutive visits.
Refractive amblyopia is treated by correcting
the refractive error with glasses and patching
the better eye. Both types must be treated in
early childhood because after age 5, it is difficult
to improve vision. After age 8, improvement
is almost impossible, but should be
tried.

2. Poor cosmetic appearance
Tropias that cannot be corrected with spectacles
may be cosmetically unacceptable and
the patient may desire surgery.

3. Loss of fusion
Fusion occurs when the images from both
eyes are perceived as one object, with resulting
stereopsis (three-dimensional vision).
Many patients with tropias never gain the
ability to fuse. Finer grades of fusion are
assessed by using the Wirt stereopsis test.

Examinations Techniqes (ultra sound)

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Central retinal vein occlusion

Clinical picture. There is usually blurring of vision coming on over a period
of some hours. The loss of acuity is usually severe (less than 6/60) but it
depends on the degree of occlusion of the vein and whether the resulting
haemorrhages and oedema affect the macula. On ophthalmoscopy it can be
seen that the retinal veins are engorged and there is oedema in the affected
area with scattered haemorrhages and sometimes retinal infarcts (cotton wool
spots). The disc is usually swollen.

Examination of the Cornea

The cornea is examined with a point light source and a loupe. The
cornea is smooth, clear, and reflective. The reflection is distorted in the presence
of corneal disorders. Epithelial defects, which are also very painful, will
take on an intense green color after application of fluorescein dye; corneal
infiltrates and scars are grayish white. Evaluating corneal sensitivity is also
important. Sensitivity is evaluated bilaterally to detect possible differences in
the reaction of both eyes. The patient looks straight ahead during the examination.
The examiner holds the upper eyelid to prevent reflexive closing and
touches the cornea anteriorly. Decreased sensitivity can provide
information about trigeminal or facial neuropathy, or may be a sign of a viral
infection of the cornea.