Intraocular Pressure, Alignment, Refractive Errors

Question 1

Vision Review

Answer 1

Evaluation of Ocular Function

7.   Ocular Alignment
   a.   Heterotropia (Strabismus)
   1)   Hypertropia
   2)   Hypotropia
   3)   Exotropia
   4)   Esotropia

Question 2

Ocular Alignment

Answer 2

Heterotropia (Strabismus)
Exophthalmos/Proptosis
Enophthalmos

Question 3

Heterotropia

Answer 3

Misalignment of an eye / all heterotropias can lead to double vision and possible cortical blindness

Question 4

Types of Misalignment of an eye

Answer 4

Hypertropia
Hypotropia
Exotropia
Esotropia

Question 5

Hypertropia

Answer 5

One eye elevated relative to other eye

Question 6

Hypotropia

Answer 6

one eye depressed relative to other eye

Question 7

Exotropia

Answer 7

one eye abducted relative to other eye

Question 8

Esotropia

Answer 8

One eye adducted relative to other eye

Question 9

Exophthalmos/Proptosis

Answer 9

1)  Some sources define exophthalmos as a protrusion of the globe greater
than 18 mm and proptosis as a protusion equal to or less than 18 mm.
(Epstein et al., 2003).
2)  Others define exophthalmos as protrusion secondary to endocrine
dysfunction and proptosis as any non-endocrine-mediated protrusion
(Epstein, 2003).

Question 10

Enophthalmos

Answer 10

1)  Recession of eye into orbit
2)  It may be a congenital anomaly
3)  acquired as a result of trauma
1)  such as in a blowout fracture of the orbit
4)  Horner’s Syndrome
5)  silent sinus syndrome
6)  phthisis bulbi
1)  a shrunken, non-functional eye that results from severe
ocular disease, inflammation, or injury.

Question 11

Examination of the Eye

Answer 11

Vision Loss

Question 12

Vision Loss

Answer 12

Refractive Error

Question 13

Refractive Error

Answer 13

1.  Pts with appropriate refraction called emmetropic
2.  Pts with refractive errors called ametropic
3.  Myopia
4.  Physiologic myopia
5. Pathologic myopia is a heritable condition in which the eye is
abnormally long with normal refracting apparatus
6.  Hyperopia

Question 14

3.  Myopia

Answer 14

a.  Common condition
b.  Refracting power of the eye at rest is too great in relation to the axial length of
the eye
1)  The focused image of an object at infinity (20 ft) lies anterior to the retina

Question 15

4.  Physiologic myopia

Answer 15

a.  Results from a mismatch between the refracting power of the optical elements
of the eye and the axial length of the globe when neither of these components
lies outside the normal range
b.  Refracting power of a normal human eye is ~65 diopters (D), with the cornea
and tear film contributing 45 D and the lens contributing 20D.
c.  The average axial length of the human eye is ~24 mm
d.  Ranges from 0.5 to 8.0D, where the eye appears normal otherwise
e.  Increased frequency of disorder in higher socioeconomic groups and among
those with greater academic training.
f.  Several studies indicate that prolonged accomodation, I.e, extensive reading,
may contribute to progression of physiologic myopia
1)  A reading environment that is well lit decreases this effect.
g.  Treated with glasses or soft contact lens correction or LASIK

Question 16

5. Pathologic myopia is a heritable condition in which the eye is
abnormally long with normal refracting apparatus

Answer 16

a. Refractive error in pathologic myopia is > 8.0D.
1) Peripapillary atrophy is common, where the internal scleral
surface of the elongated globe is incompletely covered by retina
and retinal pigmented epithelium, and a white or yellow
crescent or ring of bare sclera may be seen around the optic
nerve.
2) Pts with this are predisposed to retinal tears and holes, retinal
detachment, subretinal bleeding, and choroid
neovascularization.
3) Managed with glasses or contact lenses.

Question 17

6.  Hyperopia

Answer 17

1.  Ametropic condition when the refracting power of the
eye is insufficent to bring the focused image of an object
held at infinity onto the retina: the image lies posterior to
the retina.
2.  Hyperopia is normal in infants and children
3. Many pts with hyperopia can overcome their refractive deficiency by
accomodating when viewing at a distance.
1.  Accomodating involves activating parasympathetics to contract
the ciliary muscle to take the tension off the suspensory
ligament and allow lens thickening (greater refracting power)
2.  This moves the focus forward onto the retina in a hyperopic Pt.
3.  Abiity to accommodate decreases with increasing age
4.  Ametropes rely on accomodation to focus at near, and will
usually require refractive correction early 42-45 (presbyopia)
5.  Hyperopes may require refractive assistance earlier in life
because much of their accomodative power is used to offset
distance refractive error, and small decreases in accomodation
ability may be symptomatic (hyperopic presbyopia)
6.  In addition to blurred vision, hyperopia may result in
headaches in young adults because of the increased effort
required to focus at intermediate distances
7.  Managed with
a.  glasses or contact lens correction
b.  LASIX can be used to treat up to 5D of hyperopia

Question 18

Common Refractive Errors (Images in ppt)

Answer 18

Emmetropia
Myopia
Hyperopia

Question 19

Ammetropia

Answer 19

Hyperopia – image focused behind
retina, also called farsightedness.
Patient has difficulty seeing clearly up
close. Convex lens has a positive
dioptric value and brings image focus
forward to focus on retina (Images in ppt)

Myopia – image focused in front of retina,
also called nearsightedness. Patient has
difficulty seeing clearly at distance.
Concave lens has a negative dioptric value
and brings the image backwards to focus
on retina (Images in ppt)

Question 20

Hyperopia (Images in ppt)

Answer 20

• Axial hyperopia – length 
of eye is too short for 
refractive power of eye 
• Refractive hyperopia – 
refractive power of eye is 
less than normal for an 
eye of normal size

Question 21

Myopia (images in ppt)

Answer 21

• Axial	myopia	–	eye	is	too	
long	for	normal	refraction	
• Refrac9ve	myopia	–	
refractive	power	of	eye	too	
strong	for	eye	of	normal	
length