Dal Chun
Walter Reed Army Medical Center
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Featured researches published by Dal Chun.
Ophthalmology | 2008
Marcus H. Colyer; Dal Chun; Kraig S. Bower; John S.B. Dick; Eric D. Weichel
OBJECTIVE To report the injury patterns associated with perforating (through-and-through) injuries of the globe and the visual impact of these injuries on patients with combat ocular trauma (COT) seen at Walter Reed Army Medical Center (WRAMC) from March 2003 through October 2006. DESIGN Retrospective, noncomparative, interventional case series. PARTICIPANTS Sixty-five eyes of 61 United States military soldiers deployed during Operation Iraqi Freedom sustaining perforating globe injuries and treated subsequently at WRAMC. INTERVENTION Principal procedures included enucleation and 20-gauge 3-port pars plana vitrectomy with or without intraocular foreign body removal. MAIN OUTCOME MEASURES Final visual acuity and rates of proliferative vitreoretinopathy, enucleation, and endophthalmitis. RESULTS Average patient age was 29 years, with an average of 200 days of postinjury follow-up (median, 97 days; range, 4-1023 days). Nineteen patients confirmed the use of eye protection at the time of injury, whereas 25 patients did not use eye protection. The median presenting visual acuity at WRAMC was no light perception (range, no light perception to hand movements). Twenty-five patients underwent primary enucleation, 1 was eviscerated, and 12 patients underwent secondary enucleation within 2 weeks of surgery. Of 19 patients undergoing pars plana vitrectomy, median visual acuity at presentation was light perception and the median final visual acuity was counting fingers, whereas 4 eyes (21%) achieved final visual acuity of better than 20/200, and in 11 (61%) of 17, proliferative vitreoretinopathy developed over a follow-up of at least 6 months. There were no cases of endophthalmitis or sympathetic ophthalmia. Neither mechanism of injury nor timing of surgery correlated with favorable outcomes. However, entry and exit wounds localized to the anterior half of the globe were associated with favorable anatomic outcome (P<0.005, Fisher exact test, 2-tailed) and visual outcome (P = 0.041, Fisher exact test, 2-tailed). CONCLUSIONS Perforating globe injuries associated with COT generally result in poor visual and anatomic outcomes despite surgical intervention. Prophylactic measures, such as eye protection, are helpful in reducing the likelihood of perforating injuries; however, novel surgical and pharmacologic therapies will be required to improve the functional and anatomic outcomes of these devastating injuries.
American Journal of Pathology | 2013
Steven Pennock; David Y. Kim; Shizuo Mukai; Matthew Kuhnle; Dal Chun; Joanne A. Matsubara; Jing Cui; Patrick Ma; David Maberley; Arif Samad; Rob J. Van Geest; Sarit Y. Lesnik Oberstein; Reinier O. Schlingemann; Andrius Kazlauskas
Proliferative vitreoretinopathy (PVR) exemplifies a disease that is difficult to predict, lacks effective treatment options, and substantially reduces the quality of life of an individual. Surgery to correct a rhegmatogenous retinal detachment fails primarily because of PVR. Likely mediators of PVR are growth factors in vitreous, which stimulate cells within and behind the retina as an inevitable consequence of a breached retina. Three classes of growth factors [vascular endothelial growth factor A (VEGF-A), platelet-derived growth factors (PDGFs), and non-PDGFs (growth factors outside of the PDGF family)] are relevant to PVR pathogenesis because they act on PDGF receptor α, which is required for experimental PVR and is associated with this disease in humans. We discovered that ranibizumab (a clinically approved agent that neutralizes VEGF-A) reduced the bioactivity of vitreous from patients and experimental animals with PVR, and protected rabbits from developing disease. The apparent mechanism of ranibizumab action involved derepressing PDGFs, which, at the concentrations present in PVR vitreous, inhibited non-PDGF-mediated activation of PDGF receptor α. These preclinical findings suggest that available approaches to neutralize VEGF-A are prophylactic for PVR, and that anti-VEGF-based therapies may be effective for managing more than angiogenesis- and edema-driven pathological conditions.
Retina-the Journal of Retinal and Vitreous Diseases | 2013
Brandon N. Phillips; Dal Chun; Marcus H. Colyer
Purpose: To describe the macular findings after closed globe ocular injuries sustained from blasts. Methods: A retrospective chart review from February 2003 to March 2010 of all soldiers with closed globe ocular injuries sustained during combat with macular findings of trauma on examination was completed. Results: There were 36 eyes that met the inclusion criteria. The mean age of the soldiers was 29.5 years and 97% were men. The average follow-up time was 18.6 months. Improvised explosive device blasts accounted for 86% of injuries. Forty-five percent of soldiers had bilateral ocular injuries. Eight of 36 eyes (22.2%) developed a macular hole. One eye had spontaneous closure and five eyes underwent surgical repair. There was a range of macular findings from retinal pigment epitheliopathy alone to retinal pigment epitheliopathy with full-thickness atrophy. Eight eyes (22.2%) had macular scarring on examination but no optical coherence tomography study. One eye (2.8%) developed phthisis bulbi. Fifteen eyes (42%) had an orbital fracture. Seven eyes (19%) sustained optic neuropathy. Conclusion: Closed globe injuries after blasts resulted in a spectrum of macular findings. The integrity of the foveal inner segment/outer segment junction was the most important retinal factor in visual outcomes. Orbital fractures were not found to be a risk factor for developing optic neuropathy and may improve visual outcomes. The rate of long-term complications is unknown, and it is important for ophthalmologists to follow these patients closely.
Ophthalmic Surgery Lasers & Imaging | 2012
Dal Chun; Marcus H. Colyer; Keith J. Wroblewski
BACKGROUND AND OBJECTIVE To examine the outcomes of vitrectomy in ocular trauma with opaque cornea. PATIENTS AND METHODS This retrospective study included 17 eyes of 16 patients who underwent vitrectomy with temporary keratoprosthesis or endoscopy at Walter Reed Army Medical Center, Washington, DC, from March 2003 to October 2010. RESULTS A temporary keratoprosthesis was used in 8 eyes (47%) and endoscopy in 9 eyes (53%). Overall, the number of eyes with visual acuity of 20/200 or better improved from 0 at baseline to 5 (29%) at 6 months. The number of eyes with retinal detachment also improved from 10 (59%) at baseline to 3 (18%) at 6 months. CONCLUSION Vitrectomy may be safely performed in ocular trauma with opaque cornea using a temporary keratoprosthesis or endoscopy with comparable outcomes. Endoscopy allows earlier diagnosis and treatment of occult pathology and requires less time and fewer procedures to implement than the temporary keratoprosthesis.
Military Medicine | 2007
Dal Chun; Robert M. Bauer; Thomas P. Ward; John S.B. Dick; Kraig S. Bower
OBJECTIVE The goal was to evaluate a digital imaging system for diagnosing and grading diabetic retinopathy (DR) and cystoid macular edema (CME). METHODS A single 45 degrees, nonmydriatic, digital color photograph was taken of 231 eyes of 120 patients with diabetes mellitus. The images were graded for DR and CME by a remote ophthalmologist, and the results were compared with dilated ophthalmoscopy performed by a retina specialist. RESULTS For DR, the level of agreement between digital image review and ophthalmoscopy was moderate (kappa = 0.44). The sensitivity and specificity of digital image review were 0.60 and 1.00, respectively. For CME, the level of agreement was moderate (kappa = 0.60). The sensitivity and specificity of digital image review were 0.60 and 0.99, respectively. CONCLUSION A single 45 degrees, nonmydriatic, digital image is not reliable as the sole modality for DR screening. However, with modifications, it may be useful where access to an experienced ophthalmologist is limited.
Retinal Cases & Brief Reports | 2014
Brandon N. Phillips; Dal Chun
Investigative Ophthalmology & Visual Science | 2002
Jeff Rabin; Kraig S. Bower; Dal Chun
Investigative Ophthalmology & Visual Science | 2017
Brett Lowell Smith; Marcus H. Colyer; Dal Chun; Bongsu Kim; Maria del Carmen Piqueras; Sanjoy K. Bhattacharya; Colleen M. Cebulla
Investigative Ophthalmology & Visual Science | 2013
Steven Pennock; David M. Kim; Shizuo Mukai; Matthew Kuhnle; Dal Chun; Joanne A. Matsubara; Jing Cui; Patrick Ma; David Maberley; Andrius Kazlauskas
Investigative Ophthalmology & Visual Science | 2011
Michael P. Smith; Marcus H. Colyer; Dal Chun; Farhad Safi; Michael J. Mines