Study Determines Predictors for Globe Survival After Ocular Trauma

Lexa W. Lee

November 19, 2007

November 19, 2007 (New Orleans) — Patients with metallic intraocular foreign body (IOFB) injury are more likely to have globe loss if they are younger, have an afferent pupillary defect, and/or have a pellet gun injury, among other predictors, according to a study presented here at the American Academy of Ophthalmology 2007 Annual Meeting.

Trauma to the eye is a major cause of vision loss, and IOFBs are sometimes associated with severe ocular injuries. The purpose of this study was to assess metallic IOFB injury characteristics that were associated with globe survival and visual outcome, according to Justis Ehlers, MD, an ophthalmic resident at the Wills Eye Institute in Philadelphia, Pennsylvania.

The researchers retrospectively evaluated 1182 open-globe injuries and identified 96 eyes with metallic IOFBs. The patients ranged in age from 8 to 84 years; 94% were men. Variables in the study included injury characteristics, visual acuity, IOFB characteristics, procedures performed, complications, and globe survival. The data were evaluated by univariate statistical analysis to identify factors associated with visual outcome and globe survival.

Mechanisms of injury consisted of hammering (mostly nail related), 58%; BB/pellet gun, 8%; drilling, 7%; chiseling, 6%; fish hooks, 3%; other tools, 10%; and other/unknown, 8%. IOFB size ranged from 0.9 to 38 mm; IOFB locations were vitreous, 47%; retina, 27%; anterior chamber, 7%; iris, 7%; cornea, 5%; pars plana, 5%; lens, 3%; and not available, 5% (some injuries occurred in more than 1 location).

As to the prognostic factors associated with globe outcome, 100% of patients who had globe loss had an afferent pupillary defect vs 7% of those who kept their eye ( P = .0001), a BB/pellet injury was present in 56% of those patients who had globe loss vs 3% of those who kept their eye ( P = .0001), light perception or no light perception was present in 89% of those who lost their eye vs 8% of those who kept their eye ( P = .0001). IOFB involved the retina in 67% of those who suffered globe loss vs 23% of those who kept their eyes ( P = .02), and uveal prolapse was present in 44% of those who had globe loss vs 12% of those who kept their eye ( P = .02). The mean age of those who suffered globe loss was 21 years; the mean age for those who did not have globe loss was 34 years ( P = .007).

A final vision outcome of 20/50 or better resulted in 88% of those whose presenting vision was better than 20/200 vs 40% of those whose presenting vision was worse ( P = .001); a final outcome of vision worse than 20/200 resulted in 70% of those whose presenting vision was worse than 20/200 vs 34% of those whose presenting vision was better ( P = .001).

The researchers concluded that patients with metallic IOFBs are more likely to be young men with a history of metal-on-metal tool use. Approximately one third of the study group maintained vision of at least 20/50. Most prognostic factors associated with visual outcome and globe survival can be identified at the time of presentation and are independent of intervention.

"We looked at the prognostic factors related to globe survival, which was not in the literature," said Dr. Ehlers in an interview with Medscape Ophthalmology. "We found that BB gun and pellet injuries were highly predictive for loss of the eye, and that the location of the injury and a younger age at presentation predicted a worse outcome for globe survival; in general, the severity of injury and its characteristics probably predicted outcome. We would like to do multivariate analysis to get more information."

Richard Bensinger, MD, an ophthalmologist from Seattle, commented to Medscape Ophthalmology, "This has tremendous relevance; IOFBs are a significant source of risk to the eyes of the military in Iraq. [Improvised explosive devices] launch hundreds of tiny fragments, which frequently cause penetrating injuries to the eyes and other structures of the face and other parts of the body not protected by kevlar."

Dr. Bensinger also noted that the eye "is a very tough piece of tissue. The surface is fragile and easily injured but can rapidly recover. But anything that penetrates the outer coats — cornea or sclera — carries a terrific amount of energy, which is absorbed by the tissues penetrated or hit. Larger objects cause more damage; if they have enough energy to penetrate deeper, they will cause even more damage."

He continued, "The reason anterior segment fragments have a better prognosis is that they lose energy in penetration and never make it to the back of the eye. Larger or more energetic pieces enter the back of the eye and can disrupt the more delicate tissues there. A devastating blow can cause an 'afferent pupillary defect,' a paradoxical pupil reaction indicating a very damaged retina or optic nerve. If that finding is present, the prognosis is very poor."

In most cases, he said, "The amount of initial damage is most certainly correlated with the vision at presentation, and that is a strong prognostic finding.

"Another severe type of injury is from a BB gun," Dr. Bensinger said. "The BB pellet is very heavy, and there are usually 2 globe injuries from a BB. The first is a glancing hit, in which the BB strikes but does not penetrate. The eyes commonly will do well after a period of misery. The other is when the BB penetrates. This usually will destroy the eye, as the energy conveyed is tremendous. Note also that paint balls can do their share of damage, as can squash balls, golf balls, and badminton birdies. Larger balls usually do little direct eye damage, as they mostly hit the bones around the eye, [which] absorb most of the energy."

Dr. Ehler and Dr. Bensinger have disclosed no relevant financial relationships.

American Academy of Ophthalmology 2007 Annual Meeting: Scientific Poster PO 0467. Presented November 12, 2007.

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