11 .. Bruch's Membrane

recti muscles) to greater

than

1.0 mm (near

the pos-

terior pole). Abnormally

thin. blue-appearing

areas

of sclera called stophylomato

con be found

in eyes

with retinal detachments.

Narrow. radially

oriented

scleral dehiscenccs are

also

seen.

The vitreous

occupies

a volume

of approximately

4

cc tn an emmetropic

eye. It is firmly

attached

in a 2-

to 4-mm-wide

band

at the om

serrata

(the vitreous

base)

and

is

less tightly

bound

posteriorly

(at

the

optic

nerve.

the macula.

and

along

retinal

blood

vessels).

It can also form

abnormal

focal adhesions,

especially

around areas

of lattice degeneration

and

regions

of

chorioretinal

scarring. The vitreous

is a

complex

gel composed

of collagen

fibrils

and

hyaluronic

acid. As a result of degenerative

changes

(as well as trauma,

hemorrhage,

and

inflammatory

changes),

the vitreous may separate

from

the

neu-

rosensory retina

starting

posteriorly:

this

is called

a

posterior

vitreous

separation

(PVS)

or posterior

vit-

reous detachment

(PVD).

In the

normal

eye.

the

degeneration

involves

formation

of large

liquid cav-

ities within the

vitreous

body.

Contents

of the liq-

uefied

cavities

extrude

posteriorly

through

defects

in the posterior

hyaloid,

which

then separates

and

collapses anteriorly.

In

most

cases,

a PVD

should

be considered

a

normal

process

of

an

aging

eye;

present

clinically

in

up

to 65% of patients

over

65

years

of age. As

the

vitreous

separates

posteriorly,

it remains firmly

attached

to

the

retina

at the vitreous

base. This

places anteroposterior

traction

on

any focal

areas

of

vitreoretinal adhesion,

which

can

lead

to a retinal

break

as the

vitreous

is

pulled

anteriorly

(Figure

1-3). Retinal

breaks

that

are specifically

caused by

vitreous

traction

ore referred

to as retinal

(ears

(abo

called "flap" tears

or

"horseshoe"

tears

because

of

the U'-shnped defect that typically

occurs).

Ongoing

traction

on

the

anterior

edge

of a horseshoe

lear

will

Figure

1-3. r","I,'rior vitreous separation

with

focal vitreo-

retinal

~lllhc-",iull

causing.

a retinal

lear.

tend

to

open

the

tear

and encourage

accumulation

of subretinal

fluid.

If a section

of

retina

is com-

pletely

torn from

the retinal

surface,

an operculated

tear

results. The

round operculum

can

usually be

seen

hovering

over the retinal

defect. Since opercu-

luted

tears an: not

affected

by ongoing

vitreorctinal

traction. they

are in general

less

likely

10 allow

accumulation

of subrelinal

fluid once

opposed

10

the RPE. Retinal

breaks located

within

the vitreous

base

are

also not

subject

to ongoing

tractional

forces

and

are. therefore. less

likely

10 go

on to

reti-

nal detachment.

Hilton GF, Mcl.ean

JB. Brinton

DA. Retutul

Dcruch"'ent:

Principles

and Practice. 2nd ed. San Francisco:

Amer-

ican Academy

of Ophthalmology:

1995.

Jones LT, Reeh

MJ, Wirtscnafter

JD. Ophthalmic

anatomy.

In: American Academy

of Oplzl/lOlmulogy

Manual.

San

Francisco: American

Academy

of

Ophthalmology;

1970: 139-151.

Lowenstein A, Green

WR. Retinal

histology. In: Guyer

DR.

Yannuzzi

LA. Chang

S. Shields

JA. Green

WR. eds.

Rctina-Vitrcous.Munda.

Vol. 1. Philadelphia:

Saunders:

1999:3-20.

Macherncr

R. The

importance

of fluid

absorption.

traction,

intraocular

currents and chorinrclinal

scurs

in the ther-

apy of rhegmalOgenous

retinal

detachments.

Am J OJ'''·

thalmol 1984:98:681.

Ry"n SJ. ed. Retina.

Vol. 1, 2nd ed. SI. Louis,

MO: Mosby:

1994:5-123.

Schepens

CL. Retinal

Dctochment

and Allied

Diseases.

Vol.

1. Philadelphia:

Saunders:

1983:23-87.

The ocular examination

should include

a complete

general

eye examination

as

well as a detailed

fun-

dus study. The refractive

error should

be recorded.

In

eyes

with

a history

of

amblyopia,

an autorefrac-

tor

or

retinoscopic

evaluation

may determine the

true refractive

status.

The

corrected

visual

acuity

should

be recorded

for

each

eye. A confrontati.on

visual

field may

determine

the extent

of

the

retinal