Floaters, Flashes, Spots-->Posterior Vitreous Detachment

[liveonearth]

VITREOUS
clear gel in central cavity of the eye
~80% of the volume of the eyeball
formed by a network of collagen fibrils and macromolecules of hyaluronic acid
formed vitreous gel liquefies with age
eventually falls away or separates from the retina
retina = neurosensory tissue lining back of eye

PVD
a normal event occurring in most people sometime between 40–70 years of age
may occur at an earlier age in nearsighted, pts who'veundergone cataract surgery

PVDs
far more common than retinal detachments
often are not an emergency even when floaters appear suddenly
some vitreous detachments tug-->tear retina-->detachment

INCIDENCE
over 50% of people have a vitreous detachment by age 80
40% of pts with PVDs have light flashes
if light flashes then 15% change of developing retinal tear
1/7 pts with sudden floaters and flashes will have retinal tear or detachment
up to 50% of pts with retinal tear will have subsequent detachment
retinal tear or detachment-->immediate surgery to reattach or lose vision permanently

ETIO
with age vitreous becomes less gel-like-->dissolves, watery center
pieces/clumps of gel-like vitreous break loose in back of eye and float in watery part
clumps occur when the vitreous gel-->liquefy or shrink
occurs with aging

RISK FACTORS
inflam dt eye infx-->vitreous liquifies
nearsighted, eye shape elongated
nearsighted people are more likely to have PVDs at a younger age
very common following cataract surgery
common after surgical follow-up procedure called a YAG laser capsulotomy
(tx for cataract surgery complication in which cloudiness develops in the capsule underlying the artificial lens (IOL)
all eye procedures-->incr PVD

SX
shower of floaters and spots, clumps or stringy, light or dark
flashes of light (photopsia) dt mechanical stim to retina
(photopsia may occur dt blow to head, seeing stars, risk for retinal detachment)
vision loss dt hemorrhage
these sx could also indicate retinal detachment or retinal tear
so seek medical help immediately
uncommon: PVD, tear and detachment may occur w/o sx
uncommon: lots of sx without retinal breaks
if a retinal BV is broken-->vitreous hemorrhage
small amount of blood may be seen as a shower of spots
larger hemorrhages can cause large dark blobs in the visual field, or loss of vision
if loss of peripheral vision or see curtain across vision: emergency, detachment

FLOATERS
flecks or cobwebs that drift across visual field
dots, spots, or curly lines that appear suspended in front of you and move with your eye
glial tissue (fibrous tissue) pulled from optic nerve vitreous separates
they move when you try to look at them, can't focus right on them
a few floaters are common and no need for alarm
more visible when looking at clear bright sky or white screen
what you are actually seeing is the shadows on the retina

PHOTOPSIA
flashes of light may appear as jagged lines or "heat waves" in both eyes, lasting 10-20mins
this type of flashes usudt spasm of blood vessels in the brain (migraine)
headache after flashes = migraine
jagged lines or "heat waves" w/o headache = ophthalmic migraine
mb a symptom of digitalis toxicity

COMPLICATIONS: RETINAL TEARS, RETINAL DETATCHMENT
if gel is abnormally adherent to retina, or retina is weak-->retinal tear
PVD is the initiating event of most retinal detachments
only 10% of PVD’s will develop a retinal tear
if bleeding (vitreous hemorrhage) w/ PVD dt exceptional traction-->incr retinal tear/detachment
traction on retina during PVD also may-->macular holes or puckers

not all retinal breaks need to be treated
some are discovered on routine eval and w/o sx
many people have round or atrophic holes in their retina
if a retinal break is discovered in association with new symptoms of a PVD
if risk factors for detachment: FHx, very near sighted, detachment in other eye, Hx eye trauma, cataract surgery, more)
then-->treatment is indicated


DOUGHNUT FLOATER
= unusually large floater called a "Weiss ring"
a circular piece of condensed vitreous gel
intimately attached around the optic nerve
ring sometimes will fold in half-->floater in the shape of a "J" or "C."

GET IMMEDIATE EYE EXAM (SPECIALIST)
if new/acute symptoms of a PVD
-->get prompt and thorough examination of the retina to search for any retinal breaks
if retinal break is discovered before detachment
-->can tx with laser to seal the break
not easy to visualize a retinal break
requires very complete examination of the retinal periphery
pupil must be dilated
proper exam: incl indirect ophthalmoscopy with scleral depression
(ophthalmologist wears light source on head, examines retina with hand–held lens
while pushing in on edge of the eyeball through lids with scleral depressor
this brings the periphery of the retina into view
can use special contact lens for viewing the retinal periphery
ultrasonography mb useful to assess vitreous and loc of retinal break

IF ANY NEW SX
get reexamined
esp if within 1-2 weeks of 1st PVD occurrence

DDX
Age–Related Macular Degeneration
Diabetic Retinopathy
Retinal Venous Occlusion
Central Serous Chorioretinoapathy
Macular Hole
Macular Pucker
Retinal Tears and Detachment

TX FOR PVDs
usu no tx is given
only surgical option: vitrectomy:
to "clear" the vitreous: remove the vitreous and replace with saline

RETINAL TEARS AND DETACHMENT

THE RETINA
center of the retina is called the macula, capable of fine detailed vision
peripheral retina for side vision, over 95% of retinal, no detail vision here

DETACHMENT
retina separates from the back wall of the eye
is removed from its blood supply and nutrition
retina will degenerate and lose its ability to function if it remains detached
central vision will be lost if the macula remains detached

ETIOLOGY OF DETACHMENT IN 3 CATEGORIES
causes of retinal detachment can be divided into three main categories:

1. Rhegmatogenous Retinal Detachment
dt retinal break or tear, liquid vitreous passes behind retina, this is most common
1st sx mb loss of peripheral vision bcs tears usu occur in peripheral retina
then curtain or dark shadow across visual field which enlarges
lose central vision if macula detaches
without surgical repair vision will be lost, usu laser
laser makes series of burns aruond break-->scar and seal retina to tissue underneath
if laser cannot be used, retinal cryoprobe is used: freeze-->scar and seal
after detachment is complete it is too late to reattach, so get help quick if PVD

2. Exudative Retinal Detachment
dt exudate from under retina, mbdt tumors or inflam.

3. Traction Retinal Detachments
dt fibrovascular tissue inside vitreous cavity pulling on retina
a common cause is proliferative diabetic retinopathy


TREATMENT OF RETINAL BREAKS
TX w/ laser or cryoprobe is very successful
retinal detachment can usu be avoided if the retinal breaks are identified and treated
sometimes a retinal tear progresses rapidly-->detachment or mb no sx

Repair Of Rhegmatogenous Retinal Detachment

Fortunately, over 90% of retinal detachments can be repaired with a single procedure. Currently, there are 3 different surgical approaches to repairing a detachment: scleral buckle procedure, vitrectomy and pneumatic retinopexy.

1. Scleral Buckle
This surgical procedure has been in use for more than 40 years, and, until approximately 25 years ago, was the only procedure available. It is still commonly used for rhegmatogenous retinal detachments, especially when there are no complicating factors. The procedure involves localizing the position of all the retinal breaks, treating all retinal breaks with the cryoprobe and supporting all the retinal breaks with a scleral buckle. The buckle is usually a piece of silicone sponge or solid silicone. The type and shape of the buckle varies depending on the location and number of retinal breaks. The buckle is sewn onto the outer wall of the eyeball (sclera) to create an indentation or buckle effect inside the eye. The buckle is positioned so that it pushes in on the retinal break and effectively closes the break. Once the break is closed, the fluid under the retina (subretinal fluid) will usually spontaneously resolve over 1–2 days. Sometimes the surgeon elects to drain the subretinal fluid at the time of surgery. Most often, a scleral buckle procedure can be done with local anesthesia and as same day surgery (in and out of the hospital on the same day). Postoperatively, there are usually no positioning requirements and one can resume most activities within several days (except for anything that would jar the head).
2. Vitrectomy
Usually referred to as a Trans Pars Plana Vitrectomy (TPPV), this procedure was first used ˜25 years ago and has been continuously refined and improved since then. Over the last 5–10 years a TPPV procedure has become the initial surgery of choice for repair of many retinal detachments. The procedure involves making small incisions into the wall of the eye to allow the introduction of instruments into the vitreous cavity (the middle of the eyeball). The first part of the procedure usually is the removal of the vitreous using a vitreous cutter. Then, depending on the type and cause of the detachment, a variety of instruments (scissors, forceps, pics, lasers, etc…) and techniques (excision of tractional bands, air–fluid exchange, silicone oil fill, etc…) are used to reattach the retina. A TPPV can also usually be done as same day surgery and with local anesthesia. It is sometimes important to maintain a specific head position after surgery to keep the retina attached. More information regarding vitrectomy surgery can be found on the vitrectomy page.
3. Pneumatic Retinopexy
Since the 1980’s this has been a popular way to repair a straight–forward rhegmatogenous retinal detachment, especially if there is a single break located in the superior portion of the retina. This procedure involves injecting a gas bubble into the middle part of the eye (vitreous cavity). It is then critical to position oneself so that the gas bubble covers the retinal break. If the break can be covered by the bubble, the subretinal fluid will usually resolve within 1–2 days. The retinal tear is either treated with cryopexy before the bubble is injected or with laser after the retina has flattened. The main advantages of this approach are that it can be done in the office, thus avoiding hospitalization and that it avoids some of the complications of scleral buckling surgery, although it has its own set of complications. The main disadvantages are the requirement for precise head positioning for up to 7–10 days following the procedure and a slightly lower initial success rate as compared to a scleral buckle or TPPV. If the retina is not reattached by a pneumatic retinopexy procedure, a scleral buckle and/or TPPV can be done at that point.

Surgical Results

Approximately 90% of rhegmatogenous detachments can be initially repaired with one or a combination of these procedures. Sometimes, a scleral buckle is combined with a TPPV. If the retina does not reattach or detaches again after initial reattachment, it is usually due to the development of scar tissue on the surface of the retina and tractional forces within the vitreous cavity. If this happens following a scleral buckle procedure, it is often necessary to do a TPPV to repair the detachment. Sometimes, an intraocular gas bubble can be injected and the retina reattached following positioning. If a TPPV was done initially, it is often necessary to go back and do another TPPV to remove the new scar tissue and/or perform a scleral buckle. If a pneumatic retinopexy was the initial procedure, another pneumatic can be done or a scleral buckle or TPPV can be performed. As one can tell, there is no set way to repair a detachment and all the available procedures can be used in different combinations and sequences depending on the specific situation.
Visual Results

The visual prognosis depends mainly on the pre-existing status of the retina before it detached. If the macula has not detached, the pre–existing vision will usually be retained following successful repair. However if the macula is detached and central vision is impaired by the detachment, there may be permanent loss of central vision even if the retina is successfully repaired. The longer the macula is detached, the more likely there will be loss of vision due to irreversible damage to the photoreceptor cells. In general, if the center of the macula is detached for more than 4–5 days, there may be significant loss of central vision following surgical reattachment.
Exudative Retinal Detachment

Exudative detachments are due to leakage of fluid from the tissue layers under the retina rather than leakage of fluid vitreous from the middle of the eye through a retinal break. The most important factor in dealing with an exudative detachment is determining its cause. Many conditions can cause an exudative detachment including tumors, inflammatory disorders, connective tissue diseases and macular degenerative conditions. The evaluation of an exudative detachment will usually consist of a complete ophthalmologic examination including angiography and ultrasonography, and a complete medical work–up. The treatment will of course depend on the particular cause of the detachment. The visual prognosis also depends on the underlying etiology.
Traction Retinal Detachments

If a retinal detachment is primarily due to traction, it is termed a traction retinal detachment. The traction is usually due to proliferative fibro–vascular tissue within the vitreous cavity that pulls the retina away from the back wall of the eye. Proliferative diabetic retinopathy is a common cause of traction retinal detachments. In proliferative diabetic retinopathy, abnormal vessels (neovascularization) grow from the retinal surface onto the back surface of the vitreous. This fibrovascular tissue can then pull the retina away from the back wall of the eye, thus creating a traction retinal detachment. Another common cause is Proliferative Vitreoretinopathy (PVR). PVR is the most common cause of failure of a scleral buckle procedure for a rhegmatogenous retinal detachment and occurs ˜10% of the time. It is due to proliferation of cellular membranes (essentially scar tissue) in the vitreous cavity and on the surface of the retina. These membranes can contract and detach the retina.

A traction retinal detachment will usually need to be surgically repaired if it involves the macula. A TPPV is almost always required (see discussion of TPPV under Repair of Rhegmatogenous Retinal Detachments). Sometimes a scleral buckle is performed in conjunction with the TPPV, especially if there is a combined rhegmatogenous–traction detachment. A combined detachment usually occurs when the fibrovascular proliferation causing a traction detacment also pulls or rips a tear in the retina. Some traction detachments that involve the peripheral retinal and are not threatening the macula can be observed without surgery.

The success rate and visual outcome of surgery for traction detachments depends mainly on the underlying cause of the detachment and the extent and location of involvement. Some traction detachments can be relatively easy to repair and others can be impossible to fix even with all the advanced surgical techniques that are available today.

SOURCES
http://www.allaboutvision.com/conditions/spotsfloats.htm
http://www.vrmny.com/pe/pvd.html
http://www.vrmny.com/pe/rtrd.html