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Editor,—Ocular ball bullet (BB) injuries are vision threatening and more than 1200 people every year are reported to sustain these injuries in the United States.1 Fewer cases with BB injuries have been reported in Japan.2-4Ultrasound biomicroscopy (UBM) is useful in the morphological evaluation of the anterior segment of the eye.5 We report a 13 year old boy who sustained cyclodialysis from a BB injury, which was not revealed by gonioscopy but was by UBM. To our knowledge, this is the first report describing detection of cyclodialysis from BB injury by UBM.
A 13 year old boy sustained an ocular BB injury in his left eye and visited us the following day. The boy was accidentally shot by his elder brother. The BB was made of plastic. His best corrected visual acuity was right eye, 1.2 and left eye, 0.06. Intraocular pressure was right eye, 17 mm Hg and left eye, 11 mm Hg. Slit lamp examination revealed corneal oedema and Descemet’s folds in his left eye. The anterior chamber was of normal depth and showed moderate inflammation with aqueous cells (1+), flare (1+), and faint fibrinous exudate. Gonioscopy revealed an angle recession inferonasally with a trace hyphaema. The lens, vitreous body, and fundus of the eye were normal. Penetration of the globe was not identified. The patient was treated with atropine 1% three times daily and fluorometholone 0.1% six times daily. The next day, although corneal oedema decreased, the depth of the anterior chamber became shallower than that of the first examination and intraocular pressure decreased to 8 mm Hg. Funduscopy revealed chorioretinal folds in the posterior pole. We performed UBM, which demonstrated a small cyclodialysis in the 5 to 7 o’clock position (Fig 1), which was not apparent gonioscopically. Six days after the injury, the cornea became clearer and no inflammation in the anterior chamber was noted. Even though the depth of the anterior chamber had increased, ciliochoroidal fluid became evident (Fig 2). Intraocular pressure was 7 mm Hg. Ten days after the injury, intraocular pressure increased to 17 mm Hg. Chorioretinal folds gradually disappeared and best corrected visual acuity returned to 1.0 six weeks after the incident.
Ocular BB injuries are vision threatening and more than a few of them result in eventual enucleation.1 6-8 However, the patients without open globe injuries have better prognoses.1 6 8 Our patient, who sustained closed globe injury, also regained visual acuity of 1.0. The usual muzzle velocity of a BB gun manufactured in the USA is 350 feet per second and its weight is 0.346 g.1 Therefore, its kinetic energy is calculated at approximately 2.0 J. In our case, the weight and kinetic energy were 0.2 g and 0.4 J, respectively. We speculate that our patient’s good visual prognosis may be associated with the relatively low kinetic energy generated by the BB gun. Airgun manufacturers’ cooperation in Japan regulates their products to generate kinetic energy of 0.4 J or less. Takashimaet al 3 reviewed 50 Japanese patients with ocular BB injury in the literature and described that none of the 50 patients sustained open globe injury and all but one patient had final visual acuity of 0.7 or better. In contrast with the good visual prognoses in Japan, Schein et alreported that 78 of 140 (56%) victims of ocular BB injury in the USA sustained open globe injury and only 31 of 140 (22%) achieved visual acuity of 20/40 or better.6
Cyclodialysis is the disinsertion of the ciliary body from the scleral spur and one of its main causes is blunt trauma. Sternberget al 1 examined globes enucleated as a result of ocular BB injuries and elucidated frequent damage to the ciliary body histopathologically. The damage included tears into the ciliary body and haemorrhagic necrosis, often accompanied by choroidal haemorrhage and detachment. In the clinical setting, however, it is common that disrupted ocular tissue prevents us from assessing damage to the ciliary body. Additionally, cyclodialysis cleft is often not apparent gonioscopically, even if disruption of the ocular tissue is minimal and the anterior segment is clearly visible. This is because the iris is against the scleral spur, and the cleft is not open9 as in this particular case. In the series of 140 ocular airgun injuries, the mean age of the victims was 13 years.6 UBM might be well tolerated by even younger ages because of its non-invasive character. Therefore, the method seems to be useful to evaluate the anterior segment of the patients with closed globe injuries from BB guns.