Evaluation and Management

76 I: Principles

Figure 4–1. Rhegmatogenous retinal detachment is a diagnosis generally made by clinical examination alone, but sometimes ancillary tests are helpful. (Every effort has been made to secure permission to reproduce this image.)

vitreous separates from the retinal surface, the retina is disturbed mechanically, stimulating a sensation of light. This perception is more marked if there are focal vitreoretinal adhesions. Generally, vitreous separation is benign and may almost be regarded as normal in the senescent eye. In approximately 12% of symptomatic posterior vitreous detachments, however, a careful search of the periphery reveals a tear of the retina.

If the flashes are associated with floaters, it is wise to assume that a retinal tear exists, until proved otherwise. These symptoms demand a prompt and careful examination of the periphery with binocular indirect ophthalmoscopy and scleral indentation. The patient’s localization of the photopsia is of little value in predicting the location of the vitreoretinal pathology. If no breaks are evident in the first examination after symptomatic vitreous detachment, they rarely appear at a later date.

If there is no associated hemorrhage or other pathologic condition, the patient needs counseling only. However, if pigment or blood is detected in the vitreous, a follow-up examination is often required. It is prudent to forewarn patients about the symptoms of retinal detachment. Flashes alone or floaters alone are less significant than if they occur together, in which case they are more likely to be associated with a retinal break.

The light scintillations of an ocular migraine are correctly identified by the typical history. However, ophthalmoscopic examination may be required to rule out a retinal cause.

Floaters

While a few floaters (muscae volitantes) are experienced almost universally by the general population, the acute onset of new floaters requires careful examination. A patient describing hundreds of tiny black specks is virtually pathognomonic of vitreous hemorrhage. The sudden appearance of one large floater near the visual axis is ordinarily caused by posterior vitreous separation in which the glial annulus

(Weiss’ ring) of the posterior vitreous has pulled loose from its peripapillary location. The appearance of numerous curvilinear opacities within the visual field generally indicates vitreous degeneration. Small vitreous collagen fibrils resulting from degeneration coalesce into large, coarse fibers, which cast curvilinear shadows on the retina.

The most significant cause of floaters is vitreous hemorrhage, and the characteristic numerous tiny black dots may be followed in a few hours by “cobwebs” as the blood forms irregular clots. The cause of acute vitreous hemorrhage must be assumed to be a retinal tear, until proved otherwise. There is a direct relationship between the amount of vitreous hemorrhage and the likelihood of a retinal tear being present.

If the superior fundus cannot be adequately visualized, bilateral patching should be considered. The patient should be provided with patches for both eyes and told to apply them with tape when going to bed. They should not be removed until the patient returns for reevaluation the following morning, so a caregiver must be involved in this process. The eye should then be promptly dilated, and the patch should be immediately reapplied after the drops are instilled. Examination is carried out following adequate dilatation. This practice will usually allow blood to sufficiently settle so that the superior half of the retina can be adequately observed; this is where the great majority of breaks occur.

Although examination by ultrasonography is frequently recommended in this situation, detection of a retinal tear without detachment is a genuine art not perfected by most. If a retinal detachment is discovered in an eye with a poor view that prevents discovery of a retinal tear, the eye should be managed with vitrectomy. Otherwise, continued patching should be considered, but if this is unsuccessful after another 24 hours, serial ultrasound studies can be considered.

Visual field defects

Awareness by the patient of a visual field defect or shadow is often the first symptom of post-equatorial retinal detachment. Detachments anterior to the equator have no effect on the visual field and cannot be demonstrated with confrontation visual fields or perimetry. Detachments posterior to the equator can usually be so demonstrated, but patients rarely notice a field defect until the detachment encroaches on the posterior pole. Patients tend to be less aware of superior than inferior field defects, and those patients with inferior retinal detachments may be totally unaware of superior field loss until the fovea is involved. High bullous detachments cause dense field defects; flat detachments produce relative field defects.

Visual field examination is highly specific for localizing retinal detachments. When a patient with extensive retinal detachment is being examined, it is frequently helpful to inquire about the position of the field defect when first seen, as a clue to the location of the primary retinal break. For instance, if a patient with a total retinal detachment has a history of an inferior nasal field defect that later enlarged to involve the total field, the finding of a retinal break in the superior temporal periphery is likely.

78 I: Principles

Decreased central acuity

Although the duration of retinal detachment symptoms is estimated from the time of the onset of the visual field defect, the duration of foveal involvement dates from the time of decreased central acuity. The prognosis for recovery of central vision is approximately correlated with the duration of foveal detachment. Even a brief detachment of the fovea will usually permanently reduce the best corrected visual acuity after successful reattachment to the level of about 20/50 (6/15). Therefore, a retinal detachment threatening imminent detachment of the fovea should either be treated urgently, or the patient should be bilaterally patched until surgery can be scheduled. Unfortunately, peripheral field loss may escape a patient’s notice, so that medical help is frequently not sought until central vision is lost.

Trauma

The patient should be queried about a history of trauma, either accidental or surgical. The examiner should carefully record the details of trauma in the patient’s chart, remembering that it is a legal document that might later be reviewed. The time, place, and nature of the accident should be entered. Direct trauma to the globe should be clearly differentiated from any indirect trauma to the head or elsewhere in the body. Details of previous surgery should be noted, particularly cataract extraction, Nd:YAG capsulotomy, intraocular foreign body removal, and retinal procedures. Frequently, a patient denies any trauma during the initial examination but recalls some remote trauma a few weeks later. The denial and recollection should be recorded under the date that each is reported by the patient.

Ocular diseases

The history must include questions regarding previous ocular diseases, such as uveitis, vitreous hemorrhage, amblyopia, glaucoma, or diabetic retinopathy. Any symptom of retinal detachment can be mimicked by other disease processes. Light flashes might be due to posterior vitreous detachment, floaters might be due to age-related vitreous degeneration or uveitis, and visual field defects might be due to vascular occlusion or vitreous hemorrhage.

Systemic diseases

A careful history of the patient’s general health includes specific questions about systemic disorders that are sometimes associated with retinal detachment, including diabetes, tumors, angiomatosis of the central nervous system, sickle cell disease, leukemia, and eclampsia.

Family history

Although most retinal detachments occur as sporadic events, certain families are susceptible to retinal detachment. A family history of retinal detachment is a clue to prognosis and frequently indicates the need for examination of other family members. The history influences decisions regarding prophylactic treatment of retinal breaks.

GENERAL OCULAR EXAMINATION

Visual acuity

The best corrected visual acuity should be recorded for each eye. Generally, the patient’s current eyeglasses or contact lenses suffice, but if there is any doubt, a refraction should be performed. Visual acuity is usually measured with the Snellen test. Low vision may be recorded with a decreasing numerator of the Snellen fraction, such as 5/200 or 2/200. Because the examiner’s fingers are grossly equivalent to the 20/200 letter, counting fingers at a distance of 5 feet is approximately equivalent to 5/200. The visual acuity of illiterate or non-English-speaking patients or of preliterate children can be measured with the E chart.

Decreased visual acuity always accompanies extension of the retinal detachment into the fovea, but it does not necessarily mean detachment of the fovea. Poor central vision may also be due to antecedent disease of the macula, opacities of the media, optic nerve disease, or amblyopia.

External examination

The examiner should record the status of the brows, lashes, and lids. Accurate recording of the preoperative state of these structures is a requisite base for postoperative evaluation of the external anatomy. The early postoperative period may be characterized by pseudoptosis, lid edema, chemosis, and, rarely, permanent ptosis.

Ocular motility

Retinal reattachment surgery is occasionally accompanied by temporary changes in the function of the extraocular muscles, and in rare cases the alterations are permanent. Therefore, a preoperative record of the state of ocular motility is important. Although there are many tests of motility, the cover test and versions usually suffice. But when the vision of one or both eyes is poor, the cover test is not reliable. In such a case, the examiner should simply note the position of the light reflection of the flashlight with reference to the visual axis of each cornea (Hirschberg test). Each millimeter deviation of the corneal light reflex from the visual axis is equivalent to approximately 12 prism diopters (∆). This test can be refined by selection of the appropriate prism to restore the light reflex to the normal visual axis (Krimsky test).

Pupillary reactions

Pupillary reactions should be noted, and the size of the maximally dilated pupil recorded. Subtle differences in the direct light reflex might not be apparent unless a comparison is made between the two eyes with a swinging flashlight (Marcus Gunn test), by which the direct pupillary reflex is studied in comparison to the consensual reflex. A test result is positive when the pupil dilates as the light is directed into it, indicating that the direct reflex is weaker than the consensual. A defect in the afferent pupillomotor system, including retinal detachment, resulting in a positive test result is referred to as an afferent pupillary defect.