William Eric Sponsel

Purpose: Both pattern electroretinography (PERG) and visual evoked potentials (VEP) can be performed using low- (15%; Lc) and high- (85%; Hc) contrast gratings that may preferentially stimulate the magno- and parvocellular pathways. We observed that among glaucomatous patients showing only one VEP latency deficit per eye, there appeared to be a very strong tendency for an Hc delay in one eye and an Lc delay in the other. Methods: Diopsys NOVA-LX system was used to measure VEP Hc and Lc latency among a clinical glaucoma population to find all individuals with either a single Hc or Lc latency abnormality in each eye (group 1), or with greater than 0 and less than 4 Hc or Lc VEP latency abnormalities in the two eyes (group 2) to determine whether a significant inverse correlation existed for these values in either group. Hc and Lc PERG data were also evaluated to assess associated retinal ganglion cell responses. Results: A strong inverse correlation (P = 0.0000003) was observed between the Hc and Lc VEP latency values among the 64 eyes in group 1. Group 2 provided a comparable result (n = 143; 286 eyes; P = 0.0005). PERG (n = 81; 162 eyes) also showed strong bilateral symmetry for magnitude values (P < 0.0001 for both Lc and Hc in groups 1 and 2). Conclusions: Bilateral retention of both low-resolution/high-speed and high-resolution/low-speed function may persist with both eyes open despite symmetrically pathologic retinal ganglion cell PERG waveform asynchrony for Hc and Lc stimuli in the paired eyes. Translational Relevance: Clinical electrophysiology strongly suggests binocular compensation for dynamic dysfunction operates under central nervous system (CNS) control in glaucoma.

Sub-Saharan Africa has a population of 1 billion, with one ophthalmologist per million people. Basic ophthalmic support services are virtually absent for all but a few urban populations. Minimally invasive laser treatment may help. This study reports our initial experience using selective laser trabeculoplasty (SLT) in a mixed-racial population of adult glaucoma patients in Durban, South Africa. Institution Review Board approved the 5-year chart review. Consecutive glaucomatous adults underwent SLT (Lumenis Selecta) on one or both eyes applying 360° treatment of 120 to 140 closely spaced burns (400 urn spot size for 3 ns; range 1.1-1.4 mJ). Significance of change in intraocuar pressure (IOP) from baseline at 1, 3, 6, and 12 months was assessed by two-tailed paired t-test. Among 148 eyes of 84 patients (60 African, 21 Indian, 3 Caucasian), 69 had already undergone glaucoma therapy, and 15 untreated (de novo). Among all eyes, mean IOP was reduced by >32% with mean IOP < 15 mm Hg from baseline at all four study intervals (p < 0.0001). A 20% reduction in IOP was sustained at 12 months in 90% of African eyes but in only 50% of Indian eyes. Selective laser trabeculoplasty was effective in producing clinically significant IOP reduction among South African adults with or without prior medical or surgical anti-glaucoma therapy. Socioeconomically comparable individuals of Indian ancestry showed good therapeutic responses, but significantly less efficacious than those observed among Black subjects. Programs to provide first-line SLT management of glaucoma in Africa, where 90% of patients are unable to sustain prescribed medical therapy, appear to be a very appropriate option. Goosen E, Coleman K, Visser L, Sponsel WE. Racial Differences in Selective Laser Trabeculoplasty Efficacy. J Curr Glaucoma Pract 2017;11(1):22-27.

Objective: To assess the utility of viscoelastic injection toinduce bleb expansion and decrease intraocular pressure (IOP)in eyes with encapsulated glaucoma tube shunt blebs.Design: Case series.Subjects and participants: Forty-three glaucomatous eyes,including 13 eyes with congenital, 13 uveitic, 5 neovascular,5 open angle, 4 narrow angle and 3 traumatic glaucomas.Methods, interventions or testing: All patients underwentviscoelastic flush procedure. A pre-bent 27 or 30-gaugecannula was passed through a 25-gauge paracentesis,advanced over the iris across the anterior chamber, andinsinuated into the tube shunt lumen. Once the cannula wasfirmly lodged in position, 0.45 to 0.85 ml of viscoelastic wasinjected to hyperinflate the bleb.Main outcome measures: Paired t-tests were performedcomparing preoperative IOP and number of medications usedpreoperatively vs levels measured at 1, 6, 12, 18 and 24 months.Results: Intraocular pressure was reduced from a meanpreoperative level of 26.0 ≤ 1.2 (sem) mm Hg to 15.8 ± 1.0 at1 month, remaining stable thereafter at each 6-month intervalwith 15.1 ± 1.1 mm Hg at 24 months (p < 0.0001). Medicationuse did not vary significantly from baseline. Pressure remained. 21 mm Hg after 2 years in 85% of eyes cannulated within1 year of primary tube shunt implantation (n = 23), and in 62%of eyes cannulated more than 1 year after tube shunt placement(n = 20).Conclusion: Tube shunt expansion with bolus viscoelastic flushsuccessfully restored encapsulated bleb function, providing asubstantial (~10 mm Hg) IOP decrease into the mid-normalpressure range. This persisted in the majority of treated eyesfor the entire study period.

Purpose:: Refined analysis of frequency doubling perimetric data was performed to assess binocular visual field conservation in patients with comparable degrees of bilateral glaucomatous damage, to determine whether unilateral visual field loss is random, anatomically symmetric, or non-random in relation to the fellow eye. Methods:: Case control study of 41 consecutive patients with bilaterally mild to severe glaucoma; each right eye visual field locus was paired with randomly-selected co-isopteric left eye loci, performing 690,000 (10,000 complete sets of 69 loci) such iterations per subject. The potential role of anatomic symmetry in bilateral visual field conservation was also assessed by pairing mirror-image loci of the right- and left-eye fields. The mean values of the random co-isopteric and the symmetric mirror pairings were compared with natural point-for-point pairings of the two eyes by paired t-test. Results:: Mean unilateral Matrix threshold across the entire 30-degree visual field were 17.0 dB left and 18.4 dB right (average 17.7). The better of the naturally paired concomitant loci yielded binocular equivalent mean bilateral Matrix threshold of 20.9 dB, 1.6 dB higher than the population mean of the 690,000 coisopteric pairings (t = −10.4; P < 10^-12). Thus, a remarkable natural tendency for conservation of the binocular Matrix visual field was confirmed, far stronger than explicable by random chance. Symmetric pairings of precise mirror-image loci also produced values higher than random co-isopteric pairings (Δ 1.1 dB; t = −4.0; P = 0.0004). Conclusions:: Refined data analysis of paired Matrix visual fields confirms the existence of a natural optimization of binocular visual function in severe bilateral glaucoma via interlocking fields that could only be created by CNS involvement. The disparity of paired Matrix threshold values at mirror-image loci was also highly nonrandom and quantitatively inverse from the expected if anatomic symmetry factors were merely passively contributing systematically to the compensatory binocular Matrix effect. Translational Relevance:: The paired eyes and brain are reaffirmed to function as a unified system in the progressive age-related neurodegenerative condition chronic open angle glaucoma, maximizing the binocular visual field. Given the extensive homology of this disorder with other age-related neurodegenerations, it is reasonable to assume that the brain will similarly resist simultaneous bilateral loss of paired functional zones in both hemispheres in diseases like Alzheimer's and Parkinson's disease. Glaucomatous eyes at all stages of the disease appear to provide a highly accessible paired-organ study model for developing therapeutics to optimize conservation of function in neurodegenerative disorders.

Refined data analysis was performed to assess binocular visual field conservation in patients with bilateral glaucomatous damage to determine whether unilateral visual field loss is random, anatomically symmetric, or nonrandom in relation to the fellow eye. This was a case–control study of 47 consecutive patients with bilaterally severe glaucoma; each right eye visual field locus was paired with randomly selected coisopteric left eye loci, with 760,000 (10,000 complete sets of 76 loci) such iterations performed per subject. The potential role of anatomic symmetry in bilateral visual field conservation was also assessed by pairing mirror-image loci of the paired fields. The mean values of the random coisopteric and the symmetric mirror pairings were compared with natural point-for-point pairings of the two eyes by paired t-test. Mean unilateral thresholds across the entire visual field were 18.9 dB left and 19.9 dB right (average 19.4), 4 dB lower than the better of the naturally paired concomitant loci of 23.4 dB (P < 10−15). A remarkable natural tendency for conservation of the binocular visual field was confirmed, far stronger than explicable by random chance or anatomic symmetry (P < 0.0001), and reaffirmed by subsequent prospective simultaneous binocular visual field retesting of an arbitrary subset (n = 16) of the study population (P < 0.0001). Refined data analysis of paired visual fields confirms the existence of a natural optimization of binocular visual function in severe bilateral glaucoma via interlocking fields that could be created only by central nervous system (CNS) involvement. Integrated bilateral visual field analysis should better define actual visual disability and more accurately reflect the functional efficacy of current ocular and future CNS-oriented therapeutic approaches to the treatment of glaucoma. Glaucomatous eyes provide a highly accessible paired-organ study model for developing therapeutics to optimize conservation of function in neurodegenerative disorders.

A circumferential pretrabecular anatomical structure, the angle recess (AR), can be imaged with anterior segment ocular coherence tomography. AR's utility to predict ocular hypertension after intravitreal triamcinolone injection was assessed. 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 (Δ) and maximal IOP (max), categorized as “minimal” (IOPmax < 21 mmHg and/or IOPΔ ≤ 5 mmHg), “moderate” (IOPmax 21–29 mmHg and/or IOPΔ 6–14 mmHg), or “severe” (IOPmax ≥ 30 mmHg and/or IOPΔ ≥ 15 mmHg). Linear regression and analyses of variance were applied. 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 μm, 281 ± 22.0 μm, and 138 ± 20.3 μm, 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 μm. 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.

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; pConclusions 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.

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.

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.