A. G. Boehm

Use of the retinal vessel analyzer in ocular blood flow research

Acta Ophthalmol. 2010: 88: 717–722

Effect of diabetes mellitus on corneal biomechanics and measurement of intraocular pressure

Purpose:  To determine whether corneal hysteresis (CH) and corneal resistance factor (CRF) are altered in diabetes and whether these parameters are related to HbA1c.

Enhanced pressure in the central retinal vein decreases the perfusion pressure in the prelaminar region of the optic nerve head.

PURPOSE The pressure in the central retinal vein (CRVP) has been shown to be higher in glaucoma patients than in controls. Until now, these measurements have been performed in arbitrary units or in units of ophthalmodynamometric force. In our study, a contact lens dynamometer, calibrated in mm Hg, was used to calculate the retinal perfusion pressure. METHODS A total of 27 patients with primary open angle glaucoma (POAG) and 27 healthy control subjects were included in the study. The IOP measurement included Goldmann applanation tonometry, whereas the pressure enhancement measurement consisted of contact lens dynamometry. results: the pressures are given in mm hg, and are expressed as the mean ± SD for the control subjects versus the POAG patients: IOP 14.4 ± 2.7 vs. 15.4 ± 2.9, systolic blood pressure 141 ± 20.1 vs. 153 ± 16.5 (P = 0.013), central retinal vein threshold pressure (CRVTP) 11.9 ± 3.8 vs. 16.8 ± 5.0, CRVP 15.0 ± 2.7 vs. 17.9 ± 4.2, and retinal perfusion pressure (PPret) standard 84 ± 12.2 vs. 94 ± 9.1 and new 83 ± 12.2 vs. 91 ± 9.6. The differences in PPret between using the new versus the standard method are 0.55 ± 1.33 vs. -2.5 ± 3.89 (P = 0.041 and P = 0.002, respectively). The PPret was at least 5.0 mm Hg lower in 5 of the 27 POAG patients when the new calculation method was used. CONCLUSIONS The perfusion pressure in the retina and prelaminar region of the optic nerve head (ONH) may be lower than expected because the CRVP may be higher. The pressure measurement in the central retinal vein may be a step toward a better understanding of ONH pathophysiology.

The Effect of Education on the Assessment of Optic Nerve Head Photographs for the Glaucoma Diagnosis

BackgroundTo evaluate the effect of one lesson of continuing medical education (CME) of subjective assessment of optic nerve head appearance on sensitivity and specificity for the diagnosis of glaucoma.MethodsOphthalmologists and residents in ophthalmology attending an international glaucoma meeting arranged at Malmö University Hospital, Malmö, Sweden, were asked to grade optic nerve head (ONH) photographs of healthy and glaucomatous subjects at two sessions separated by a lecture on glaucoma diagnosis by ONH assessment. Each grader had access to an individual portfolio of 50 ONH photographs randomly selected from a web-based data bank including ONH photographs of 73 glaucoma patients and 123 healthy subjects. The individual portfolio of photographs was graded before and after the lecture, but in different randomized order.ResultsNinety-six doctors, 91% of all attending the meeting, completed both assessment sessions. The number of correct classifications increased from 69 to 72% on the average. Diagnostic sensitivity increased significantly (p < 0.0001) from 70% to 80%, and the number of photographs classified as uncertain decreased significantly (p < 0.0001) from 22% to 13%. Specificity remained at 68%, and intra-grader agreement decreased.ConclusionCME had only a small effect on the assessment of ONH for the glaucoma diagnosis. Sensitivity increased and the amount of uncertain classifications decreased, while specificity was unchanged.

Comparison of the effects of bimatoprost and a fixed combination of latanoprost and timolol on 24-hour blood and ocular perfusion pressures: the results of a randomized trial

BackgroundTo compare the effect of bimatoprost and the fixed combination latanoprost-timolol (LTFC) on 24-hour systolic (SBP) and diastolic (DBP) blood pressure and on 24-hour ocular perfusion pressure (OPP).Methods200 patients with glaucoma or ocular hypertension, controlled on the unfixed combination of latanoprost and timolol or eligible for dual therapy being not being fully controlled on monotherapy were enrolled in a randomized, double-masked, placebo-controlled, multicentre clinical trial. They were randomized to LTFC (8 a.m.) or bimatoprost (8 p.m.) and received 24-hour IOP curve at baseline, 6 and 12 weeks (supine and sitting position IOPs were recorded at 8 p.m., midnight, 5 a.m., 8a.m., noon and 4 p.m.). Holter 24-hour blood pressure curve was obtained between weeks 2 and 12. SBP, DBP, OPP were calculated and compared with ANOVA. Rates of diastolic OPP (DPP) ≤50, ≤40, ≤30 mmHg in the 2 groups were calculated and compared using Fisher’s test.ResultsMean baseline SBP and DBP were 136.5 ± 18.3 vs 134.2 ± 20.1 mmHg (p = 0.1) and 79.1 ± 10.2 vs 78.2 ± 10.1 mmHg (p = 0.4) in the bimatoprost and LTFC groups respectively. Holter SBP was significantly higher for bimatoprost (135.1 mmHg vs 128.1 mmHg, p = 0.04), while no statistically significant difference in DBP was found. DPP was similar in the 2 groups, and proportions of patients with at least one value of the 24-hour curve ≤50, ≤40, ≤30 mmHg were 94%, 86%, 41% respectively.ConclusionsBimatoprost and LTFC had similar DBPs and OPPs; SBP was significantly lower with LTFC. In this study, the percentage of “dippers” was considerably higher than the one described in previous studies on the role of perfusion pressure in glaucoma.Trial registrationNCT02154217, May 21, 2014.