Phillip Hendrickson

Longterm Visual Field Follow-up of Glaucoma Patients Treated with Beta-blockers

In a prospective, randomized, double-masked study, 44 patients with primary open-angle glaucoma were treated either with 0.5% betaxolol or 0.5% timolol in both eyes twice daily. Twenty-nine patients could be followed up for 48 months. Seventeen of these patients were treated with betaxolol and 12 with timolol. Each examination included visual field measurements with an Octopus automated perimeter 201 (Program G1), intraocular pressure measurement, funduscopy, as well as pulse and arterial blood pressure measurements. Both drugs lowered in the intraocular pressure. This reduction was slightly but not statistically significantly higher in the timolol-treated group. However, the visual fields improved more in the betaxolol group. Patients treated with betaxolol had significantly smaller averaged mean defects (p < 0.05) and higher averaged mean sensitivities (p < 0.05, Wilcoxon rank score text) than did timolol-treated patients at months 3, 6, 12, and 18. Thereafter, the difference between the two groups was not statistically significant in this relatively small sample size. For betaxolol patients the cumulative area-under-the-curve analysis for the worse eye yielded significantly larger mean sensitivities beyond month 12 (exception: month 30; p < 0.05) and significantly smaller mean defects beyond month 6 (p < 0.05).

Modulation of Heidelberg Retinal Flowmeter parameter flow at the papilla of healthy subjects: effect of carbogen, oxygen, high intraocular pressure, and beta-blockers.

The Heidelberg Retina Flowmeter (HRF) is intended to assess ocular blood flow by scanning laser doppler flowmetry. In the retina and possibly in the optic nerve head, carbogen increases blood flow, whereas pure oxygen or high intraocular pressure (IOP) decrease it. This study addresses whether at the papilla of healthy volunteers, the HRF parameter flow, is modulated by breathing 5% carbogen (5% carbon dioxide + 95% oxygen) for 7 minutes, breathing 100% oxygen for 7 minutes, increasing IOP to 50 mm Hg with a suction cup, or decreasing IOP with a single topical ocular instillation of the beta-blockers 0.5% betaxolol (betoptic) or 0.5% timolol (timoptic). At the papilla (20 degrees x 5 degrees, 256 X 64 pixels), values of HRF parameter, flow (50 X 50) pixels, increased after carbogen (N = 5, P < 0.05), but decreased after oxygen (N = 5, P < 0.05) or IOP increase (N = 5, P < 0.01). Although IOP values were significantly reduced by betaxolol (N = 9, P < 0.05) and timolol (N = 9, P < 0.01), HRF values were only significantly decreased (N = 9, P < 0.05) after timolol. In conclusion, at the papilla of healthy volunteers, a positive correlation exists between changes in values of the HRF-parameter, flow, and stimuli considered to modulate retinal and ONH blood flow. Furthermore, although of unkown clinical relevance, it appears that in contrast to betaxolol, values of the HRF parameter, flow, at the papilla of healthy volunteers are significantly decreased after a single instillation of timolol.

Effect of Carbogen, Oxygen and Intraocular Pressure on Heidelberg Retina Flowmeter Parameter ‘Flow’ Measured at the Papilla

The aim of the study was to evaluate whether the Heidelberg retina flowmeter (HRF), a new device for retinal and anterior optic nerve blood flow assessment, can gauge, at least semiquantitatively, a known effect such as an increase in optic nerve blood flow by hypercapnia or a decrease in optic nerve blood flow by hyperoxia or high intraocular pressure (IOP). Measurements with the HRF were obtained at the papilla of three groups of 5 young healthy subjects (1) at baseline and after breathing 5% carbogen, (2) at baseline and after breathing 100% oxygen and (3) at baseline and after increasing IOP to 20 and 50 mm Hg. The changes in the value of the HRF parameter ‘flow’ were analyzed by means of a paired Student’s t test. Breathing 100% oxygen for 7 min resulted in a statistically significant decrease of 34.7±2.5% (mean ± SEM) in HR parameter ‘flow’ (p < 0.01) at the papilla. Breathing 5% carbogen for 7 min resulted in a statistically significant increase of 18.3±2.6% in HRF parameter ‘flow’ (p = 0.024). Increasing IOP to 20 mm Hg did not result in a statistically significant change in HRF parameter ‘flow’ (–9.6±7.4%; p = 0.13). Increasing IOP from 20 to 50 mm Hg, however, resulted in a statistically significant decrease of 40.1±6.6% in HRF parameter ‘flow’ (p = 0.003). With the applied stimuli, the HRF parameter ‘flow’ changed in the expected direction, i.e. an increase with hypercapnia and a decrease with hyperoxia or high IOP. The simplicity of use of the HRF instrument suggests that it might be well suited for a non-invasive, at least semiquantitative, assessment of changes in blood flow at the papilla.

Thirty-Month Visual Field Follow-up of Glaucoma Patients Treated with β-Blockers

We reported earlier on a prospective, randomized, double-masked study in which 36 patients with open-angle glaucoma were treated with either 0.5% betaxolol or 0.5% timolol in both eyes twice daily. In that previous report, we described that both drugs reduced the intraocular pressure significantly, whereby timolol had a slightly larger influence than betaxolol. However, betaxolol-treated patients had a slightly but statistically significantly better visual field survival in this 18-month period. Of these 36 patients, 29 could be followed up under the same previous treatment for an additional 12 months. Twelve of these patients were treated with timolol and 17 with betaxolol. Three of the five drop-outs in the timolol-treated group showed a clear tendency toward deterioration of the visual field, whereas the dropouts in the betaxolol-treated group had stable visual function. The present analysis is based on a 30-month period. The intraocular pressure remained stable and was slightly but not statistically significantly lower in the timolol-treated patients. The visual fields remained stable, as well. In relation to the baseline, the mean sensitivity had improved more in the betaxolol-treated patients. The difference to the timolol-treated patients was not statistically significant in this relatively small sample size.

Measurement of Intraocular Pressure with a Modern Noncontact Tonometer

Purpose: To evaluate the intraocular pressure (IOP) in a population without known glaucoma as measured by means of a noncontact tonometer (NCT). Methods: IOP values of 842 persons, measured by means of a Pulsair 2000 NCT ® (Keeler Instruments, Inc., Broomhall, Pennsylvania) by 5 investigators were evaluated. Three consecutive measurements were taken first on the right eye and then on the left eye in each subject. Topical anesthesia was not used. Results: The distribution of the measured IOP values was significantly different from a normal distribution. The median IOP was 15.0 mm Hg (lower quartile/upper quartile 12.5/17.2). There were no differences in IOP values between male and female subjects or between right and left eyes. There was no correlation between age and IOP values. Ninety percent of the subjects had an IOP within a range of 9–24 mm Hg in both eyes. Among the examined subjects, the IOP was above 24 and 21 mm Hg in 4,6 and 11%, respectively, in at least one eye. The median range of consecutive IOP measurements in one eye was 3 mm Hg (lower quartile/upper quartile 2.0/4.0). The median interocular IOP difference was 1.7 mm Hg (0.7/2.7). The median individual coefficient of variation (CV) values were 10.0% for the right eyes, –10.8% for the left eyes. Among the 5 different examiners, the IOP values, range of 3 consecutive IOP readings in one eye, interocular asymmetry and CV values were statistically comparable. Conclusion: The Pulsair 2000 NCT is very simple to use and its handling is mostly independent of the operator. The results of the present investigation might be of some value for future screening programs.

Anterior Chamber Depth and Pigment Dispersion Syndrome

Pigment dispersion syndrome is thought to be the result of iris pigment abrasion by zonular packets. This condition primarily affects young males with myopia, perhaps because of deeper anterior chambers that make such pigment abrasion more likely. Males have been described to have larger eyes and deeper anterior chambers. This constellation, however, does not explain conclusively the predominance of males who have pigment dispersion syndrome. We, therefore, studied whether anterior chambers in males are deeper than those in females, not only in absolute measures but also relative to the axial length. Our results of 60 patients disclosed that men had not only significantly deeper mean absolute anterior chambers (men, 3.22 +/- 0.42 mm; women, 2.88 +/- 0.38 mm; P = .002) but also deeper mean relative anterior chambers (men, 13.54% +/- 1.66%; women, 12.45% +/- 1.2%; P = .013). No significant differences existed between genders with regard to lens thickness, extent of ametropia, and visual acuity. Thus, normal developmental differences between genders may predispose males for deeper anterior chambers and, consequently, for pigment dispersion syndrome.

Intraocular pressure decrease after local ocular cooling is underestimated by applanation tonometry

Background: The effects of intense systemic or local cooling on aqueous humor dynamics in animals are an increased total outflow facility and a decreased aqueous flow. Few studies suggest that only vasoconstriction of arteriolar segments of the episcleral vasculature may be the cause for a decrease in intraocular pressure after local cooling in humans. Because corneal changes may have influenced such studies, the effect of local cooling was assessed in normal subjects. Methods: Intraocular pressure and corneal thickness were measured in 18 healthy human subjects before and after exposure of the right eye to both, an air stream at 20° C, and an air stream at 0° C. Results: No significant changes in IOP or corneal thickness occurred under 20° C conditions. After local cooling, the mean corneal thickness increased from 0.52 ± 0.01 mm to 0.57 ± 0.02 mm (p < 0.001). Mean intraocular pressure decreased from 13.8 ± 2.9 mmHg to 12.9 ± 3.1 mmHg (p < 0.026). The observed decrease in IOP correlated significantly but negatively (R = − 0.53; p = 0.024) with the increase in corneal thickness, indicating that the cooling effect on IOP may be rather underestimated. Conclusion: The eye is very sensitive to local cooling effects, which may, however, partially be masked by changes in corneal thickness.