William Eric Sponsel

PREVALENCE OF GLAUCOMA: THE BEAVER DAM EYE STUDY

PURPOSEnThe purpose of this study is to determine the prevalence of glaucoma in the population participating in the Beaver Dam Eye Study (n = 4926).nnnMETHODSnAll subjects were examined according to standard protocols, which included applanation tonometry, examination of the anterior chamber, perimetry, grading of fundus photographs of the optic disc, and a medical history interview. Visual field, cup-to-disc ratio, and intraocular pressure (IOP) criteria were used to define the presence of open-angle glaucoma. Definite open-angle glaucoma was defined by the presence of any two or all three of the following: abnormal visual field, large or asymmetric cup-to-disc ratio, high IOP.nnnRESULTSnThe overall prevalence of definite open-angle glaucoma was 2.1%. The prevalence increased with age from 0.9% in people 43 to 54 years of age to 4.7% in people 75 years of age or older. There was no significant effect of sex after adjusting for age. Of the 104 cases of definite open-angle glaucoma, 33 had IOPs less than 22 mmHg in the involved eye. Hemorrhage on the optic disc was found in 46 people; 2 of these had glaucoma. Narrow-angle glaucoma was rare, with two definite cases in the population.nnnCONCLUSIONnThe prevalence of open-angle glaucoma in Beaver Dam is similar to that in other white populations. Findings from this study re-emphasize the notion that estimates of glaucoma prevalence should be based on assessing multiple risk indicators.

Retinal Hemodynamics Using Scanning Laser Ophthalmoscopy and Hemorheology in Chronic Open-angle Glaucoma

PURPOSEnRecent studies suggest that elevated intraocular pressure is not the only causative factor for the development of visual field loss and optic nerve damage in glaucomatous eyes. The authors determine whether retinal hemodynamics or blood fluidity are alternated in eyes of patients with open-angle glaucoma compared with those of age- and sex-matched healthy subjects.nnnMETHODnHigh-quality video fluorescein angiograms were obtained from single eyes of 51 patients with chronic open-angle glaucoma. From these angiograms, the arm-retina time, mean dye velocity, and arteriovenous passage time were quantified. The data from patients were compared with those of an age- and sex-matched group of healthy subjects.nnnRESULTSnIn patients with chronic open-angle glaucoma, an 11% reduction of the mean dye velocity (P < 0.05) and a 41% prolongation of the arteriovenous passage time (P < 0.01) was observed relative to the values obtained among the control subjects. Among hematocrit values, plasma viscosity, and erythrocyte aggregation, only plasma viscosity showed a significant increase (4%; P < 0.01) in patients with chronic open-angle glaucoma.nnnCONCLUSIONnThese results indicate that a pronounced circulatory deficit exists within the retinal vasculature of glaucomatous eyes, which may coexist with, but cannot be fully attributed to, an increase in plasma viscosity.

Perifoveal microcirculation with non-insulin-dependent diabetes mellitus

Fluorescein angiograms were performed to evaluate perifoveal capillary blood velocities (v), capillary density (perifoveal intercapillary areas: PIA) and the foveal avascular zone (FAZ) by means of the scanning laser technique (SLO-101 Rodenstock). The angiograms were digitally stored and the data quantified off-line with an image analyzing system (IBAS). In the present study 46 patients with non-insulin-dependent diabetes mellitus (NIDDM) were examined and their data compared with that of 31 healthy volunteers. The perifoveal capillary flow velocity of the NIDDM subjects (v = 2.33±0.36 mm/s) was significantly (P <0.01) decreased as compared to healthy subjects (v = 2.86 ±0.41 mm/s). The perifoveal intercapillary areas in the foveal avascular zone were significantly increased in patients with NIDDM (PIA=10029 ± 3402 μm2; FAZ = 0.415 ± 0.272 mm2) as compared with healthy subjects (PIA = 3965 ± 467 μm2; FAZ=0.221 ± 0.071 mm2). These data suggest the possibility that a decrease in perifoveal capillary blood velocities in combination with decreased capillary density (enlarged PIA) and an enlargement of the foveal avascular zone may occur in patients with NIDDM. The determination of these parameters could help in monitoring the progress of diabetic retinopathy and diabetic maculopathy.

Physiological perturbation of ocular and cerebral blood flow as measured by scanning laser ophthalmoscopy and color doppler imaging

Retinal blood flow regulation in health remains poorly described. We hypothesized that retinal perfusion is controlled to provide constant O2 delivery to that tissue, and that changes in retinal blood flow in response to chemical stimuli parallel changes in carotid and retrobulbar perfusion. Accordingly, in 11 young adults with normal eye examinations, we measured retinal blood flow indices (via scanning laser ophthalmoscopy [SLO] during fluorescein angiography) and carotid, ophthalmic, and central retinal arterial blood flow indices (via Doppler imaging [CDI]) under control, hypoxic (alveolar PO2 = 55 +/- 3 mmHg) and hyperoxic (alveolar PO2 = 655 +/- 18 mmHg) conditions. The three conditions were counterbalanced in order and isocapnia was maintained in each. Retinal arterial mean dye velocity and arteriovenous passage time, as measured by SLO, were slowed by hyperoxia and accelerated by hypoxia, in rough proportion to the changes in arterial O2 content (+/- 10%; p < 0.05). In the seven subjects in which relative measurements of retinal arterial diameters were obtained, neither hypoxia nor hyperoxia significantly altered vessel diameter. At the same time, mean retinal capillary transit velocity was independent of PO2, suggesting that, in health, retinal capillaries may be recruited as PO2 falls. O2-induced changes in carotid, ophthalmic, or central retinal arterial blood flow velocities (via CDI) were not found, though a wide coefficient of variation (30% for CDI vs. 14% for SLO) may have contributed to this failure. We conclude that, under isocapnic conditions, retinal perfusion may be regulated to provide constant O2 delivery.(ABSTRACT TRUNCATED AT 250 WORDS)

Macular capillary particle velocities: a blue field and scanning laser comparison

Abstract• Background: Two different techniques are available for measurement of macular capillary particle velocities. The psychophysical blue field simulation technique gives data on macular leukocyte flow velocities, while the scanning laser technique provides information on capillary blood velocities of hypofluorescent segments in the macular network. Published velocity data differ considerably between the two methods. The current study was undertaken to compare the two measuring techniques in a group of healthy volunteers. • Methods: Thirty-two healthy subjects (12 man, 20 women, mean age 27 years) participated in this study. All subjects underwent entoptic leukocyte visualization by means of blue field simulation followed by fluorescein angiography using scanning laser ophthalmoscopy. • Results: The capillary blood velocities measured using the scanning laser technique were significantly higher (P < 0.01) than the flow velocities estimated with the blue field simulation technique (2.68 ± 0.3 mm/s vs 0.89 ±0.2 mm/s). No significant correlation between the flow velocities was found (r = −0.22). • Conclusion: The differences may be related to different measuring locations and/or measurements of different phenomena. The blue field technique estimates average leukocyte flow in the macular network, whereas the scanning laser technique quantifies the velocity of erythrocyte aggregates in the capillary lumen of the para- and perifoveal network. A combination of both techniques may be helpful in interpreting physiological responsiveness and altered velocity pattern in diseased eyes.

A comparison of postoperative complications from pressure-ridge Molteno implants versus Molteno implants with suture ligation.

BACKGROUND AND OBJECTIVESnThe pressure-ridge Molteno implant incorporates a ridge on the proximal episcleral plate to limit aqueous outflow during the immediate postoperative period. This modification is intended to decrease the high incidence of postoperative hypotony and flat anterior chambers following Molteno tube implantation, while avoiding the pressure spikes that can occur with suture ligation of the Molteno tube. This study was devised to compare postoperative intraocular pressure control and complications associated with pressure-ridge Molteno implantation versus a standard Molteno implantation with suture ligation of the tube.nnnPATIENTS AND METHODSnThirty eyes were prospectively randomized to receive either a pressure-ridge, double-plate Molteno implant or a standard, double-plate Molteno Molteno implant with suture ligation of the tube.nnnRESULTSnPostoperative intraocular pressure was significantly higher at day 1 and week 2 in the suture-ligation implant group, although the final pressure at 12 weeks was not different between the two groups. Six of 15 eyes from the pressure-ridge implant group experienced shallow or flat anterior chambers with hypotony, whereas 5 of 15 eyes from the suture-ligation implant group had significant postoperative pressure spikes.nnnCONCLUSIONnBecause the ridge effect is unpredictable, further modifications are necessary to prevent postoperative hypotony.

The gold foil electrode in pattern electroretinography

A recent study found that the gold foil electrode produces large pattern electroretinogram amplitudes, but the test-retest reliability was low. In a three-center study, we observed that 90% of 29 patients who were tested with gold foil electrodes used three times appeared to have markedly lower amplitudes than when tested with new electrodes during the same session. Across study centers, the mean of the new electrode recordings was 3.78 µV (standard deviation, 1.13 µV), versus 2.93 µV (1.29 µV) for used electrodes. This 0.85-µV reduction (22%) was statistically significant (F = 7.10 p = 0.01). Electrodes used three times demonstrated an average change in the coefficient of variation of 14% (standard deviation/mean = coefficient of variation; new, 1.13/3.78 = 30%; used, 1.29/2.93 = 44%). Two of the study sites (Houston/Indianapolis) conducted test-retest pattern electroretinograms on a total of 18 patients and found the mean evoked potential to be 3.55 µV with new electrodes and 2.82 µV with used electrodes. The coefficient of variation for the test-retest data was 30% and 47% for new and used electrodes, respectively. Light microscopy showed small cracks on the surface of the electrode, with the number and configuration of the cracks varying in each electrode. The presence of cracks is further complicated by their proximity to the tear film. These sources of variation can result in significantly different impedances. We propose that constant flexion, as a result of patient blinking, causes cracks in the thin gold surface of the electrode. Used electrodes will produce lower pattern electroretinogram amplitudes and poor test-retest reliability. To minimize these problems, the gold foil electrode should only be used a single time.

Measurement of superficial optic nerve head capillary blood velocities by scanning laser fluorescein angiography.

Scanning laser ophthalmoscopy is capable of producing video fluorescein angiograms with high spatial and temporal resolution. Digital image analysis of these angiograms has been used to produce measures of capillary flow velocities in perimacular capillaries. We have recently utilized the same technique to measure flow velocities in the superficial capillary layers of the optic nerve head. We performed video fluorescein angiograms using the Ro-denstock (Germany) scanning laser ophthalmoscope. The passage of hyperflu-orescent particles through optic nerve head capillaries was imaged in five healthy subjects (two men and three women). The flow velocity for each of eight to 10 capillaries in each subject was measured three to five times. The mean capillary blood flow velocity for all subjects was 2.71 mm/s. These results are similar to those obtained in perifoveal capillaries. We have demonstrated that scanning laser fluorescein angiography can be adapted for measuring superficial optic disk capillary flow velocities. The possibility remains for the imaging of capillaries in deeper portions of the optic nerve head by using the confocol abilities of the scanning laser ophthalmoscope. Future use of this technique may aid our understanding of the pathophysiology of optic neuropathy.

Quantification and monitoring of visual field defects and prospective, randomized comparison of pilocarpine and timolol using computerized perimetry (17).

OBJECTIVESnA prospective, randomized comparison of timolol and pilocarpine was carried out in patients with newly diagnosed glaucoma to determine the effects of medication on visual function as determined by computerized perimetry.

Utility of Operative Glaucoma Tube Shunt Viscoelastic Bolus Flush

ABSTRACT Objective: To assess the utility of viscoelastic injection to induce 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 underwent viscoelastic flush procedure. A pre-bent 27 or 30-gauge cannula was passed through a 25-gauge paracentesis, advanced over the iris across the anterior chamber, and insinuated into the tube shunt lumen. Once the cannula was firmly lodged in position, 0.45 to 0.85 ml of viscoelastic was injected to hyperinflate the bleb. Main outcome measures: Paired t-tests were performed comparing preoperative IOP and number of medications used preoperatively vs levels measured at 1, 6, 12, 18 and 24 months. Results: Intraocular pressure was reduced from a mean preoperative level of 26.0 ± 1.2 (sem) mm Hg to 15.8 ± 1.0 at 1 month, remaining stable thereafter at each 6-month interval with 15.1 ± 1.1 mm Hg at 24 months (p < 0.0001). Medication use did not vary significantly from baseline. Pressure remained < 21 mm Hg after 2 years in 85% of eyes cannulated within 1 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 flush successfully restored encapsulated bleb function, providing a substantial (~10 mm Hg) IOP decrease into the mid-normal pressure range. This persisted in the majority of treated eyes for the entire study period. How to cite this article: Groth SL, Greider KL, Sponsel WE. Utility of Operative Glaucoma Tube Shunt Viscoelastic Bolus Flush. J Curr Glaucoma Pract 2015;9(3):73-76.