Retinal Detachment
In the normal eye, the retina lies in apposition to the underlying tissues
through a combination of osmotic forces and a weak extracellular matrix adhesion
between the photoreceptor outer segments and the microvilli of the retinal
pigment epithelium. Maintenance of the precise extracellular composition
requires integrity of the vasculature of the choriocapillaris (tight junctions
making up the "blood-ocular barrier").
Detachments
of the retina are categorized as either those associated with a retinal tear (rhegmatogenous)
or those which are serous or exudative (non-rhegmatogenous). Both forms can be
caused by many conditions including systemic diseases as well as those limited
to the eye.
Causes of Retinal Detachment
| Rhegmatogenous |
| Trauma |
| Vitreal hemorrhage |
| Inflammation-induced vitreal traction bands |
| Peripheral cystic retinal degeneration |
| Non-rhegmatogenous (exudative) |
| Systemic hypertension |
| Exudative choroiditis |
| Systemic infections |
| fungal |
| viral (FeLV, FIV, FIP) |
| toxoplasmosis |
| Erlichia |
| Borrelia |
| bacterial |
| Neoplasia |
| primary ocular |
| secondary (multiple myeloma, lymphosarcoma) |
| Immune-mediated |
| Vogt-Koyanagi-Harada syndrome |
| vasculitis |
| hyperviscosity syndrome |
Retinal detachment demonstrated by ultrasonography
A traumatic chorioretinal tear (arrows) in a Chihuahua. The white area within the tear is sclera. The adjacent choroid is normal but minimally pigmented and the vasculature can be seen.
In some cases, the diagnosis of retinal detachment is made by direct
visualization of the retina. In other cases, opacities (cataract, hemorrhage)
may prevent direct visualization and ultrasonography may be necessary.
Treatment is directed at 1) medical therapy to promote resorption of the
subretinal fluid and 2) mechanical attachment of the retina (retinopexy).
Accurate diagnosis of a primary condition, if any, allows for specific medical
therapy. Systemic hypertension is the most common cause of serous retinal
detachment in cats (Hypertensive retinopathy). Management of high blood pressure
through diet and anti-hypertensive medications often results in retinal
re-attachment and restoration of vision in these cases. Retinal detachments
caused by idiopathic or immune-mediated conditions require the use of
non-specific medical therapy. systemic corticosteroids and diuretics are of
value in promoting resorption of the subretinal fluid. These medications are of
little value, however, in cases where a retinal tear exists as there is
continued fluid seepage from the vitreous compartment into the open subretinal
space. In such cases, particular when the tear is located superiorly, gravity
will encourage progression of the detachment.
Appearance following laser retinopexy
in the Chihuahua pictured above.
Arrows indicate laser burns
Retinal detachment can be seen as one of the most frustrating complication of surgical cataract extraction. Although they occur rarely, these detachments are often associated with retinal tears, making them refractory to medical management. many of the breeds in which inherited cataracts are seen are also at greater risk for progressive vitreal degeneration which can weaken the retinal/RPE attachment, predisposing to retinal detachment. The most notable example of this is the Shih Tzu, where spontaneous retinal detachment occurs as a sequella to vitreal degeneration.
Surgical extraction of a luxated lens often also requires removal of some of the vitreous which can predispose to retinal detachment. Lens-induced uveitis, which is often seen in eyes where cataract surgery is contemplated, is also considered a risk factor for retinal detachment. Because the density of the lens opacity may prevent direct visualization of the retina, ocular ultrasonography is used to detect a pre-existing retinal detachment prior to surgery.
This diagram illustrates the positioning
of the retinopexy probe when used for
prophylactic peripheral retinopexy.
Veterinary Vision acknowledges the support of Iridex Iris Medical, Inc. in providing the equipment and technical support which has made possible the development of many of the techniques described in this article.