Sylvia L. Groth

Blunt eye trauma: Empirical histopathologic paintball impact thresholds in fresh mounted porcine eyes

PURPOSE Ballistic studies were conducted using gelatin-embedded abattoir-fresh porcine eyes suspended within clear acrylic orbits to discern the energy required to produce specific ocular injuries. Paintball impact provides a robust ballistic model for isolating and quantifying the role of direct blunt force in ocular trauma. METHODS Fifty-nine porcine orbital preparations received direct blows from 0.68 caliber (16-18 mm diameter/3.8 g) paintballs fired at impact velocities ranging from 26 to 97 meters per second (2-13.5 J). Five additional eyes not subjected to ballistic impact were also evaluated as controls. Impact energies were correlated with histopathologic damage. RESULTS Minimum impact energies consistently producing damage in experimental eyes unobserved in control specimens were: 2 joules--posterior lens dislocation, zonulysis, capsular rupture, and choroidal detachment; 3.5 joules--moderate angle recession; 4 joules--anterior lens dislocation; 4.8 joules--peripapillary retinal detachment; 7 joules--severe angle recession, iridodialysis, and cyclodialysis; 7.5 joules--corneal stromal distraction; 9.3 joules--choroidal segmentation; and 10 joules--globe rupture. CONCLUSIONS Impact thresholds correlating traumatic ocular pathology with impact energy followed a positive stepwise progression in severity with impact energies between 2 and 10 joules. Moderate angle recession commensurate with typical clinical traumatic glaucoma was not observed among control eyes, but occurred at relatively low impact energy of 3.5 joules among test eyes. Extensive disruption in and around the angle (iridodialysis/cyclodialysis) consistently occurred at energies >7 joules. Globe rupture required a minimum energy of 10 joules.

Small-incision insertion of artificial iris prostheses.

In this interventional case series, a flexible iris prosthesis was implanted in consecutive patients with sight-compromising iris defects. Each prosthesis was injected via a clear corneal microincision as part of a planned combined procedure. Iris insertion was accompanied by cataract removal or implanted using an intraocular lens injector during glaucoma tube shunt placement in a pseudophakic eye. All 4 patients experienced a positive outcome that was visually beneficial. These early cases suggest that with responsible patient selection and appropriate postoperative management, flexible posterior chamber iris implants can be placed successfully, with significant visual benefit, via a corneal microincision in eyes with congenital, traumatic, or uveitic iris defects.

Anatomical Manifestations of Primary Blast Ocular Trauma Observed in a Postmortem Porcine Model

PURPOSE We qualitatively describe the anatomic features of primary blast ocular injury observed using a postmortem porcine eye model. Porcine eyes were exposed to various levels of blast energy to determine the optimal conditions for future testing. METHODS We studied 53 enucleated porcine eyes: 13 controls and 40 exposed to a range of primary blast energy levels. Eyes were preassessed with B-scan and ultrasound biomicroscopy (UBM) ultrasonography, photographed, mounted in gelatin within acrylic orbits, and monitored with high-speed videography during blast-tube impulse exposure. Postimpact photography, ultrasonography, and histopathology were performed, and ocular damage was assessed. RESULTS Evidence for primary blast injury was obtained. While some of the same damage was observed in the control eyes, the incidence and severity of this damage in exposed eyes increased with impulse and peak pressure, suggesting that primary blast exacerbated these injuries. Common findings included angle recession, internal scleral delamination, cyclodialysis, peripheral chorioretinal detachments, and radial peripapillary retinal detachments. No full-thickness openings of the eyewall were observed in any of the eyes tested. Scleral damage demonstrated the strongest associative tendency for increasing likelihood of injury with increased overpressure. CONCLUSIONS These data provide evidence that primary blast alone (in the absence of particle impact) can produce clinically relevant ocular damage in a postmortem model. The blast parameters derived from this study are being used currently in an in vivo model. We also propose a new Cumulative Injury Score indicating the clinical relevance of observed injuries.

Mitomycin-augmented non-penetrating deep sclerectomy: preoperative gonioscopy and postoperative perimetric, tonometric and medication trends

Background/Aims Non-penetrating deep sclerectomy (NPDS) can enhance drainage of aqueous humour without disrupting the trabecular endothelial layer, reducing risks of postoperative hypotony and hyphema. This study explores associations of angle morphology with surgical efficacy in eyes with open and obstructed angles. Methods Eighty-nine consecutive eyes undergoing successful NPDS (non-implant, with 0.4 mg/ml mitomycin C and limbus-based two-layer closure) were studied in this institutional review board-approved retrospective quality assurance study. Postoperative complication frequency, intraocular pressure (IOP), glaucoma medications required and acuity were monitored (baseline vs 3, 6, 9, 12 and 18-month postoperative levels), along with 30-2 Humphrey MD and corrected pattern standard deviation (CPSD) (baseline vs 6, 12 and 18-month postoperative values). Preoperative gonioscopy was compared with the subsequent requirement for specific postoperative interventions. Results IOP at all five postoperative intervals was reduced (22±0.9 to 12±0.5 mm Hg; p<0.0001). No hyphema were observed. Postoperative hypotony (IOP < 4 mm Hg) occurred rarely (8/445; 1.8%). Mean glaucoma medication use dropped from 3.1±0.1 to 0.23±0.1 at 18 months (p<0.0001). Mean 30-2 MD improved by approximately 1.4 dB at 6, 12 and 18 months (p<0.002); CPSD remained stable. Conclusions Following NPDS, a sustained IOP decrease of 10 mm  Hg (45%) was attained, with stable acuity, increased perimetric generalised light sensitivity and 90% reduction in medical therapy requirement. Morbidity risk was associated with narrow gonioscopic angle insertion and synechia, but not with shallow approach or trabecular pigmentation.

Paintball Trauma and Mechanisms of Optic Nerve Injury: Rotational Avulsion and Rebound Evulsion

PURPOSE Ballistic impact studies and supercomputer modeling were performed to elicit the mechanisms of optic nerve rupture that may accompany blunt ocular trauma. METHODS Paintball ocular impact responses were studied with abattoir-fresh porcine eyes. Physics-based numerical code CTH was used to produce robust geometric and constitutive models of the eye and orbit, providing a comparative 3-D finite volume model to help determine the mechanisms underlying empirical ballistic observations. RESULTS Among 59 porcine eye specimens submitted to paintball impact in the 1- to 13-J range, 10 (17%) disengaged completely from the orbital mount. In each instance the paintball penetrated the orbit adjacent to the globe, producing rotation and eventual globe repulsion, dramatically evident on high-speed film images. Supercomputer modeling yielded similar globe-expulsive results when orbital constraints were in place, but not when these were removed. In these models, tangential (grazing) impact sheared the nerve flush with the globe via a strain rate effect within 260 μs, with minimal posterior displacement and just 5° of globe rotation. Midperipheral impact produced compressive globe distortion and posterior displacement, followed by rebound and tractional nerve avulsion 10 mm behind the lamina after 700 μs and 20° of globe rotation. CONCLUSIONS Constitutive modeling studies suggest at least two trajectory-dependent mechanisms for optic nerve rupture with paintball impact on the eye. Tangential glancing blows produce strain-rate rotational avulsion, abscising the optic nerve with minimal internal globe disruption, whereas off-center direct impact produces slower rotational-rebound evulsion, traumatizing the globe and breaching the nerve posteriorly. The latter mechanism would be expected to arise more commonly and would most likely be clinically masked by accompanying intraocular injury.

Comparing bevacizumab and ranibizumab for initial reduction of central macular thickness in patients with retinal vein occlusions

Purpose To examine short-term effects of ranibizumab versus bevacizumab on reduction of optical coherence tomography (OCT) central macular thickness (CMT) in patients with macular edema secondary to retinal vein occlusions (RVOs). Methods This is a retrospective analysis in which patients with RVOs were injected with either bevacizumab or ranibizumab. At 2 weeks, all patients were injected with a dexamethasone intravitreal implant (Ozurdex®). CMT on OCT and best-corrected visual acuity were obtained at baseline, at 2 weeks (just prior to the dexamethasone intravitreal implant), and 6 weeks. Results Sixty-four patients received injections (32 bevacizumab; 32 ranibizumab). At 2 weeks, bevacizumab group had a mean (±standard error of mean [SEM]) CMT reduction of 26.2% ± 3.4% versus 47% ± 3.5% reduction with ranibizumab (P < 0.0001). At 6 weeks, there was a 31.6% ± 3.2% CMT reduction with bevacizumab versus 52% ± 3.2% with ranibizumab (P < 0.0001). At 2 weeks, 15 (9%) of bevacizumab patients versus 25 (78.1%) ranibizumab patients achieved OCT CMT < 300 μm (P = 0.0192). At 6 weeks, 18 (56.3%) of bevacizumab compared to 30 (93.8%) of ranibizumab patients achieved CMT < 300 μm (P = 0.0010). Visual acuity was not significantly different at each time interval between the groups. Conclusion Ranibizumab appears to have a greater effect in the short-term of decreasing macular edema on OCT when compared to bevacizumab in patients with RVOs.

Retinal nerve fiber layer thickness using spectral-domain optical coherence tomography in patients with no light perception secondary to optic atrophy

Background:Optical coherence tomography (OCT) provides useful structural information that can augment functional data. Newer spectral-domain technology provides faster and higher resolution images than time-domain machines. Although each measures the same structures, the values systematically differ. We evaluated eyes with longstanding no light perception (NLP) visual acuity secondary to optic atrophy using spectral-domain OCT to determine minimum retinal nerve fiber layer (RNFL) thickness. Methods:The authors conducted a retrospective, cross-sectional chart review study to identify patients with NLP acuity for 8 months or more and having a good quality Spectralis OCT (Heidelberg Engineering, Heidelberg, Germany) to measure the RNFL thickness. An unpaired t test compared the eyes with a previously published data set measured with time-domain OCT. Results:Eleven eyes from 10 patients were examined with the Spectralis OCT. The mean duration of documented NLP acuity was 3.72 ± 1.20 years. The mean RNFL thickness was 34.18 ± 2.66 &mgr;m (95% confidence interval, 28.26–40.11 &mgr;m). Mean RNFL thickness was significantly thinner on this spectral-domain OCT than previously published values on time-domain OCT (34.18 vs 45.42 &mgr;m, P = 0.004). Conclusion:Using the Spectralis OCT, mean RNFL thickness for NLP eyes due to optic atrophy is 28–40 &mgr;m. This provides clinicians useful information when considering how aggressively to manage patients with optic nerve disease.

Low-Level Primary Blast Causes Acute Ocular Trauma in Rabbits

The objective of this study was to determine whether clinically significant ocular trauma can be induced by a survivable isolated primary blast using a live animal model. Both eyes of 18 Dutch Belted rabbits were exposed to various survivable low-level blast overpressures in a large-scale shock tube simulating a primary blast similar to an improvised explosive device. Eyes of the blast-exposed rabbits (as well as five control rabbits) were thoroughly examined before and after blast to detect changes. Clinically significant changes in corneal thickness arose immediately after blast and were sustained through 48 h, suggesting possible disruption of endothelial function. Retinal thickness (RT) increased with increasing specific impulse immediately after exposure. Intraocular pressure (IOP) was inversely correlated with the specific impulse of the blast wave. These findings clearly indicate that survivable primary blast causes ocular injuries with likely visual functional sequelae of clinical and military relevance.

Association Of Oct Angle Recess Width With Iop Response After Intravitreal Triamcinolone Injection

Purpose: A circumferential pretrabecular anatomical structure, the angle recess (AR), can be imaged with anterior segment ocular coherence tomography. ARs utility to predict ocular hypertension after intravitreal triamcinolone injection was assessed. Methods: All intravitreal triamcinolone injection recipients from 2002 to 2005 with high-resolution anterior segment ocular coherence tomography images had AR width (between the anteriormost prominence of the iris root and posterior cornea) measured by masked physicians using the caliper function of Stratus ocular coherence tomography. Intraocular pressures (IOPs) from 1 month before to 6 months after the injection were compiled for IOP rise (&Dgr;) and maximal IOP (max), categorized as “minimal” (IOPmax < 21 mmHg and/or IOP&Dgr; ⩽ 5 mmHg), “moderate” (IOPmax 21–29 mmHg and/or IOP&Dgr; 6–14 mmHg), or “severe” (IOPmax ≥ 30 mmHg and/or IOP&Dgr; ≥ 15 mmHg). Linear regression and analyses of variance were applied. Results: Twenty-six eyes satisfied the entry criteria, with 11 (42%) eyes demonstrating minimal, 11 (42%) moderate, and 4 (15%) severe IOP responses. The corresponding (mean ± SEM) AR widths were: 326 ± 31.5 &mgr;m, 281 ± 22.0 &mgr;m, and 138 ± 20.3 &mgr;m, respectively. Highly significant AR width differences existed between moderate and severe responders and between minimal and severe responders (both P < 0.004); 5 of 6 patients with IOP ≥ 29 mmHg had AR < 200 &mgr;m. Conclusion: These findings indicate that a potentially clinically useful relationship exists between AR width and IOP elevation accompanying intravitreal triamcinolone injection. Anterior segment screening could become a beneficial extension of ocular coherence tomography for retinal practices.

Optic neuropathy secondary to spontaneous intracranial hypotension (SIH) as related to experimental primate model

We read with great interest the recent article by Yang et al. regarding their primate model investigating optic neuropathy resulting from reduced cerebrospinal fluid pressure. The authors conducted a thorough case-control study looking at the effects of intracranial hypotension from insertion of a lumbar-peritoneal shunt in four rhesus monkeys, adding five control monkeys with lumbar-peritoneal shunt inserted but immediately occluded. This is an innovative study, giving some vital information about the structural damage to the optic nerve that can ensue from decreased intracranial pressures. This study is of particular interest to us given a clinical case we recently encountered. In brief, a 74-year-old man developed slowly progressive vision loss over 9 to 12 months. He had a history of nonpostural headache. On examination, the visual acuities (VA) were 20/125, right eye and 20/20, left eye. The remainder of his examination was significant for a 2þ right relative afferent pupillary defect, right eye dyschromatopsia, and obvious optic atrophy in the right eye with 3þpallor. Visual field testing showed a temporal defect respecting the vertical meridian in the right eye, and superior and inferior constriction in the left eye (Figs. 1A, 1B). Magnetic resonance imaging (MRI) revealed diffuse dural thickening and enhancement in the vicinity of the optic canals bilaterally (Fig. 2A). A lumbar puncture demonstrated an opening pressure of 80 mm H20 and an elevated cerebrospinal fluid (CSF) protein of 88 mg/dL. Cytology was negative. Five days after the lumbar puncture, the patient noted a slowly progressive decline in vision, now also involving the left eye. The visual acuities were 9/200 in the right eye and 20/30 in the left eye. Visual field testing showed worsening (Figs. 1C, 1D). The patient then underwent a lumbar epidural blood patch procedure. Subsequently, the visual loss ceased and the visual fields remained stable in the right eye, and gradually improved in the left eye, over the next 6 months (Figs. 1E, 1F). Repeat neuroimaging demonstrated significantly improved meningeal thickening and decreased enhancement in the region of the optic canals (Fig. 2B). Our presumption is that the visual loss was a consequence of intracranial hypotension, supported by the fact that the progressive loss ceased on the right and function was restored on the left once the blood patch was done. Our MRI of this patient showed dural thickening with noticeable overall morphologic improvement after the patch was placed. This also supports spontaneous intracranial hypotension (SIH) as a probable etiology. Spontaneous intracranial hypotension is an uncommon disorder that is often missed or misdiagnosed due to its variable clinical manifestations, especially in the absence of postural headache. A case series by Horton and Fishman described two patients with visual field loss in the setting of SIH. After blood patch, the perimetry normalized in both subjects. The authors postulated that the visual field defects were likely related to compression or vascular congestion of the intracranial portions of the optic nerve. In SIH, the CSF opening pressure is typically low, but a significant minority of the patients with a documented active CSF leak and typical clinical and imaging manifestations of the FIGURE 1. Visual field at presentation shows a superior and inferior constriction in the left eye (A), and a temporal defect respecting the vertical meridian in the right eye (B). Visual fields worsened in both eyes over the next 2 weeks ([C] left eye, [D] right eye) then after the blood patch gradually improved in the left eye (E) and remained stable in the right eye (F) over the next 6 months.