9 Retinal Detachment

Retinal DetachmentLast Updated: April 11, 2006

INTRODUCTION

Background:

Next to central retinal artery occlusion and chemical burns to the eye, retinal detachment is one of the most time-critical eye emergencies encountered in the ED. Retinal detachment (RD) was first recognized in the early 1700s by de Saint-Yves, but clinical diagnosis remained elusive until Helmholtz invented the ophthalmoscope in 1851.

Tragically, RDs were uniformly blinding until the 1920s when Jules Gonin, MD, pioneered the first repair of RDs in Lausanne, Switzerland. Today, with the advent of scleral buckling, intravitreal gas, microscopic, laser, and cryotherapy techniques, rapid ED diagnosis and treatment of an RD truly can be a vision-saving opportunity.

Pathophysiology:

Retinal detachment refers to separation of the inner layers of the retina from the underlying retinal pigment epithelium (RPE, choroid). The choroid is a vascular membrane containing large branched pigment cells sandwiched between the retina and sclera. Separation of the sensory retina from the underlying RPE occurs by the following 3 basic mechanisms:

A hole, tear, or break in the neuronal layer allowing fluid from the vitreous cavity to seep in between and separate sensory and RPE layers (ie, rhegmatogenous RD)

Traction from inflammatory or vascular fibrous membranes on the surface of the retina, which tether to the vitreous

Exudation of material into the subretinal space from retinal vessels such as in hypertension, central retinal venous occlusion, vasculitis, or papilledema

RDs may be associated with congenital malformations, metabolic disorders, trauma (including previous ocular surgery), vascular disease, choroidal tumors, high myopia or vitreous disease, or degeneration.

Of the 3 types of retinal detachment, rhegmatogenous RD is the most common, deriving its name from rhegma, meaning rent or break. Vitreous fluid enters the break and separates the sensory retina from the underlying RPE, resulting in detachment.

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Exudative or serous detachments occur when subretinal fluid accumulates and causes detachment without any corresponding break in the retina. The etiologic factors are often tumor growth or inflammation.

Tractional retinal detachment occurs as a result of adhesions between the vitreous gel and the retina. Centripetal mechanical forces cause the separation of the retina from the RPE without a retinal break. Advanced adhesion may result in the development of a tear or break. The most common causes of tractional RD are proliferative diabetic retinopathy, sickle cell disease, advanced retinopathy of prematurity, and penetrating trauma. Vitreoretinal traction increases with age, as the vitreous gel shrinks and collapses over time, frequently causing posterior vitreous detachments in approximately two thirds of persons older than 70 years.

Frequency:

In the US: Although 6% of the general population have retinal breaks, most of these are benign atrophic holes, which are without accompanying pathology and do not lead to retinal detachment. Incidence of retinal detachment is 1 in 15,000 population, with a prevalence of 0.3% in the US. The annual incidence is approximately one in 10,000 or about 1 in 300 over a lifetime (Haimann, 1982). Other sources suggest that the age-adjusted incidence of idiopathic retinal detachments is approximately 12.5 cases per 100,000 per year, or about 28,000 cases per year in the US. (Subramanian and Topping, 2004).

Certain groups have higher prevalence than others. Patients with high myopia (>6 diopters), a condition that is more common in males than in females have a 5% risk; individuals with aphakia (ie, cataract removal without lens implant) have a 2% risk. Cataract extraction complicated by vitreous loss during surgery has an increased detachment rate to 10%.

Internationally:

The most common worldwide etiologic factors associated with RD are myopia (ie, nearsightedness), aphakia, pseudophakia (ie, cataract removal with lens implant), and trauma. Approximately 40-50% of all patients with detachments have myopia, 30-40% have undergone cataract removal, and 10-20% have encountered direct ocular trauma. Traumatic detachments are more common in young persons, and myopic detachment occurs most commonly in persons aged 25-45 years. Although no studies are available to estimate incidence of RD related to contact sports, specific sports (eg, boxing and bungee jumping) have an increased risk of RD.

Mortality/Morbidity:



Estimates reveal that 15% of people with retinal detachments in one eye develop detachment in the other eye. Risk of bilateral detachment is increased (25-30%) in patients who have had bilateral cataract extraction.

Race:

Incidence of retinal detachment is relatively frequent in people of Jewish ethnicity and relatively low in black persons.

Sex:

No predilection exists; overall, incidence is unchanged even when corrections for the higher rate of ocular trauma in men is considered.

Of those younger than 45 years who have RD, 60% are male and 40% are female.

Age:

As the population ages, RDs are becoming more common. Retinal detachment usually occurs in persons aged 40-70 years. However, paintball injuries in young children and teens are becoming increasingly common causes of eye injuries, including traumatic retinal detachments.

CLINICAL

History:

Initial symptoms commonly include the sensation of a flashing light (photopsia) related to retinal traction and often accompanied by a shower of floaters (RPE) and vision loss.

Over time, the patient may report a shadow in the peripheral visual field, which, if ignored, may spread rapidly to involve the entire visual field in a matter of days. Vision loss may be filmy, cloudy, irregular, or curtainlike.

Retinal tissue is stimulated by light but also responds to mechanical disturbances. Flashing lights usually are caused by separation of the posterior vitreous. As the vitreous gel separates from the retina, it stimulates the retinal tissue mechanically, resulting in the release of phosphenes and the sensation of light.

Pathologic stimulation of the retina and production of phosphenes cause photopsia.



Patients often may note decreased visual acuity and a wavy distortion of objects (metamorphopsia). If a RD involves the macula, acuity is severely reduced.

Posterior vitreous detachment is usually a benign process; however, 12% of symptomatic detachments reveal a peripheral tear in the retina. The location of the light sensation in the patient's visual field has no correlation to the location of a retinal tear.

Floaters are a very common visual symptom in the population; thus, distinguishing their etiology requires eliciting a detailed history. o The sudden onset of one large floater in the center of the visual axis

indicates posterior vitreous detachment (PVD). The patient observes a circular floater when the vitreous detaches from its annular ring surrounding the optic nerve.

o Numerous curvilinear opacities indicate vitreous degeneration, which is considered a normal aspect of a mature eye. More ominous and concerning is the description of hundreds of tiny black specks appearing before the eye. This is pathognomonic for vitreous hemorrhage, resulting from disruption of a retinal vessel caused by a retinal tear or mechanical traction of a vitreoretinal adhesion.

o A few hours after the initial shower of black spots, the patient can note cobwebs that result from blood forming irregular clots.

o Generally, the new onset of floaters associated with flashing lights indicates a retinal tear until proven otherwise.

Visual field defects are a late symptom of retinal detachment.

While symptoms of photopsia and floaters are not helpful in locating the position of the retinal tear or detachment, the visual field defect is very specific for locating the detachment.

Detachments anterior to the equator of the eye cannot be detected with visual field testing.

Detachment posterior to the equator can be isolated with visual field testing, but the patient usually is unaware of a defect until it involves the posterior pole and macula.

Patients are less aware of a superior field defect (indicating an inferior detachment) than an inferior field defect (indicating a superior retinal detachment).

Inferior retinal detachment can be a long-standing condition that progresses without symptoms until the detachment reaches the fovea.



Bullous (ie, large ballooning) detachments produce dense visual field defects (ie, blackness), and flat detachments produce relative field defects (ie, grayness).

When a patient has an extensive detachment, inquiring about the initial symptoms of the visual field loss is helpful to assist in localization of the tear.

Onset of decreased visual acuity dates the duration of fovea involvement of the detachment, which correlates with the prognosis for recovery of the central vision.

Metamorphopsia is a macular fluid-based distortion of a visual image and is commonly described by patients as waviness.

Inquire about history of trauma, including whether it occurred several months before the symptoms or coincided with the onset of symptoms. Documentation of head or ocular trauma may be subject to legal investigation, especially in children.

Note previous surgery, including cataract extraction, intraocular foreign body removal, and retinal procedures.

Question the patient about previous conditions, such as uveitis, vitreous hemorrhage, amblyopia, glaucoma, and diabetic retinopathy. Query about family history of eye disease because, although RDs usually are sporadic events, certain pedigrees may be prone to detachment. Systemic diseases associated with retinal detachment include the following:

o Diabetes o Tumors (eg, breast cancer, melanoma) o Angiomatosis of the CNS o Sickle cell disease o Leukemia o Eclampsia o Prematurity

Physical:

Check visual acuity, correcting for refractive error.

Conduct an external examination for signs of trauma, checking the visual field (usually a confrontation field examination is adequate). Visual fields can help isolate the location of the RD.



Check pupil reaction (a fixed dilated pupil may indicate previous trauma; a positive Marcus-Gunn pupil can occur with any disturbance of the afferent pupillomotor pathway, including RD).

Administer slit-lamp biomicroscopy (the anterior segment is usually normal).

Examine the vitreous for signs of pigment or tobacco dust (ie, Shafer sign), which is pathognomonic for a retinal tear in 70% of cases with no previous eye disease or surgery.

Check intraocular pressure measurement in both eyes (hypotony of >4-5 mm Hg less than the fellow eye is common).

Conduct a fundus examination with ophthalmoscopy (pupils must be dilated or a panoptic may be used).

o Indirect ophthalmoscopy is the definitive means of diagnosing RD with the use of scleral depression in order to see the anterior retina and definitively identify the location of the tear or hole.

o Direct funduscopy may detect vitreous hemorrhage and large detachment of the posterior pole, but it is inadequate for complete examination because of the lower magnification and illumination, lack of stereopsis, and limited view of the peripheral retina.

o A 3-mirror contact lens examination with a slit-lamp may accomplish adequate examination without scleral depression.

o Obvious detachment is observed as marked elevation of the retina, which appears gray with dark blood vessels that may lie in folds.

o The detached retina may undulate and appear out of focus. Shallow detachments are much more difficult to detect; thus, comparing the suspected area with an adjacent normal quadrant is helpful to detect any change in retinal transparency. Binocular vision is needed to do this well.

o A pigmented or nonpigmented line may demarcate the limit of a detachment, and the retinal surface may have an orange-peel appearance.



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9 Retinal Detachment