Retinal Tears and Detachments
Eye trauma accounts for about 10-12 percent of retinal detachments and is the most frequent cause of retinal detachments in children. Retinal tears coming from trauma are usually because of retinal tears at the base of the vitreous although some tears can result from direct blunt trauma or indirect contrecoup injuries. Recognition of the types of tears possible is important in order to prevent retinal detachment.
Retinal tears due to trauma are the result of transmission of an external force to the eye with distortion of the eye. The shape of the eye can change drastically after a blow. Since the cornea and sclera of the eye are relatively inelastic, the globe cannot stretch in response to being deformed. When a force is suddenly applied to the eye, the volume of the eye must remain relatively constant since the outflow of fluid cannot increase fast enough to absorb the volume displacement. The net effect is a change in shape but not in the volume of the eye. This can produce traction on a number of structures, include the vitreous base of the eye, where the vitreous is normally firmly attached to the peripheral retina. This where the retina tears.
Two major mechanisms can lead to retinal tears after blunt trauma to the eye. The first is a result of changes in the shape of the eye with secondary tractional effects on the base of the vitreous fluid. This is what seems to result in the vast majority of retinal tears. The traction on the vitreous base is transmitted to the retina, leading to retinal tears at the anterior or posterior border of the base of the vitreous.
Retinal breaks can also occur at the site of focal vitreoretinal attachment, such as the edge of lattice degeneration or a chorioretinal scar. A second type of retinal tear stems from fragmentation and tissue death of the retina at the site of direct trauma to the sclera. These tears usually occur in the relatively unprotected temporal retina. Retinal tears associated with direct trauma to the retina are often associated with intraretinal hemorrhages and retinal edema, often producing large, irregular retinal tears.Clinical Setting
Traumatic retinal tears can occur after several different types of eye injuries. Most traumatic retinal tears and detachments occur from direct trauma to the globe. The patient may perceive that indirect trauma to the head or body has contributed to a retinal detachment but actually, this is an infrequent cause of retinal tears. Only about 40 percent of traumatic retinal detachments related to nonpenetrating eye contusion are caused by an injury at home. Thirty-five percent of retinal detachments are from sporting injuries and 8 percent are related to a work injury.
The trauma usually results in an immediate retinal tear, although the tear may be delayed if it comes from cellular proliferation on the retina or to tissue death of the traumatized retina. The interval between the eye contusion and the retinal tear or detachment may be prolonged. In one study, the interval between the injury to the eye and the discovery of a detachment was five years with a range of between 1 and 27 years. In other studies, 12-20 percent of traumatic retinal detachments were detected within twenty-four hours after the injury, 30-46 percent were found within a month, 50-60 percent within 8 months, and 80-82 percent were found within two years of the injury.
Traumatic retinal detachments tend to occur in younger individuals, with 80 percent occurring under the age of 40. There tends to be more males with retinal detachments when compared to females. Myopic eyes appear more likely to develop a retinal tear or detachment after trauma.
Trauma to the retina and vitreous base may be seen because one of several different types of retinal tears. In one study of retinal detachments, it was found that 84 percent had dialysis, 8 percent had giant retinal tears, 3 percent had horseshoe tears, and 5 percent had round holes.
Avulsion of the vitreous base from the peripheral retina is a sign of eye trauma because the vitreous base is usually firmly adherent to the peripheral retina and pars plana. Avulsion of the vitreous base usually results in no eye symptoms, although the patient may complain of floaters as a part of partial vitreous detachment. Fragments of the nonpigmented pars plana epithelium are often adherent to the avulsed vitreous base, giving the appearance of a pigmented band draped over the peripheral retina. Vitreous base avulsions alone do not have to be treated but examination must be performed for associated traumatic eye damage such as a giant retinal tear, retinal dialysis, angle recession, or subluxed crystalline lens.
Retinal dialysis occurs when the retina separates from the border of the nonpigmented pars planus epithelium at the ora serrata. Most of these situations happen as a result of trauma, although some authors have postulated a genetic predisposition in some eyes. Many retinal dialyses are completely silent, which accounts for the delay in detecting the retinal detachment.
Patients with a retinal dialysis will complain of floaters or mild blurring of vision. They usually occur at the time of trauma but some are related to vitreoretinal traction and may not develop until weeks or months later. To check for retinal dialysis, the peripheral part of the retina must be examined by depressing on the sclera as soon as it is deemed safe to do so. Occult perforation or rupture of the globe needs to be ruled out first.
The normal serrated contour of the ora serrata will appear to deviate at the site of the dialysis with blunting of the serrations within the dialysis. Pigment may be visible at the previous line of attachment of the peripheral retina, giving the appearance of a bifurcation at the border of the dialysis and the normal or serrata. Some dialyses do not lead to retinal detachment but become surrounded by pigmentary changes with a spontaneous chorioretinal adhesion.
Most dialyses in the absence of retinal detachment should be treated with laser photocoagulation. Photocoagulation with a three-mirror contact lens is not usually possible because of the peripheral location of the lesion but a laser indirect ophthalmoscope delivery system may be used with scleral depression to surround the dialysis with laser photocoagulation. Most dialyses should be treated preventatively in order to try to prevent retinal detachment.
Retinal detachment secondary to dialyses often progress slowly and are detected incidentally months or years later. The symptoms are similar to a regular dialysis with blurring of the vision, double vision, or floaters. The symptoms of retinal detachment due to retinal dialysis may be accompanied by visual field changes when the detachment progresses to the equator or by a loss of vision if the detachment affects the macula.
One or more demarcation lines may be seen in longstanding posttraumatic retinal detachments. These lines were found to be present in 46 percent of one series of eyes with traumatic retinal detachment secondary to dialyses. A chronic detachment may cause the retina to become very thin and can be confused with retinoschisis if not examined carefully.
Retinal detachments secondary to traumatic dialyses are generally treated with cryopexy and placement of a circumferential scleral buckle to support the dialysis. Drainage of subretinal fluid can be avoided in many circumstances but may need to occur if there is bulbous detachment or vitreoretinal traction on the dialysis or if the intraocular pressure must be lowered for placement of a broad scleral buckle.
The surgical results of repair of traumatic retinal detachment secondary to detachment secondary to dialyses are usually excellent. The rate of retinal reattachment with one operation has been reported as 87-94 percent and, if more than one operation is needed, the rate of reattachment is 96-98 percent. The final visual acuity depends on whether or not the macula was detached or attached preoperatively. In one study, the visual acuity was 20/40 or better in 44 percent of cases, 20/50 to 20/100 in 24 percent of cases and 20/200 or worse in 32 percent of cases.
Traumatic retinal tears without retinal detachment due to contusion-induced retinal tissue death or traction at the site of a vitreoretinal adhesion occur less frequently than dialysis following blunt trauma. There are three basic types of retinal tears following direct trauma to the eye:
- Round holes may vary from one hole or more peripheral small round holes to larger irregular holes with apparent disintegration of the retina.
- A macular hole can result from a contrecoup injury, which exerts traction on the normal attachment of the vitreous gel to the macula.
- Tractional retinal tears typically show attachment of the vitreous to the edge of the tear, forming a horseshoe configuration or other signs of vitreoretinal traction such as an operculated hole.
It may be difficult to determine whether a tractional tear was related to trauma unless there are other signs of trauma to the eye. Traumatic retinal tears are often associated with symptoms of floaters and decreased vision. Traumatic retinal tears are generally more likely to progress to detachment when compared to dialyses.
If a traumatic retinal tear is found more than a month after the trauma and is surrounded by a chorioretinal adhesion, treatment may not be necessary. These eyes, however, must be followed very carefully because some tears will result in retinal detachment later. Most retinal tears should be treated with cryopexy or laser photocoagulation.