Relationship between the rate of change in lamina cribrosa depth and the rate of retinal nerve fiber layer thinning following glaucoma surgery.

PURPOSE:To assess whether lamina cribrosa depth (LCD) reduction and the rate of change in LCD over time (ΔLCD/Δt) is associated with retinal nerve fiber layer (RNFL) thickness and the rate of RNFL thinning over time (ΔRNFL/Δt) to test the hypothesis that, in a long term, RNFL thinning occurs irrespectively to the displacement of the lamina cribrosa following glaucoma surgery. METHODS:Twenty-nine primary open-angle glaucoma patients underwent glaucoma surgery. Sixteen patients underwent trabeculectomy and 13 patients undertook non-penetrating deep sclerectomy. Images of optic nerve head using spectral-domain optical coherence tomography (SD-OCT) with enhanced depth imaging technology were obtained preoperatively, at one-, three-, six-month and follow-up postoperative visit from 12 to 29 months after surgery (1pv, 3pv, 6pv, and FUpv, respectively). Correspondingly, measurements of the circumpapillary RNFL thickness were acquired. RESULTS:Intraocular pressure decreased from 24.0±8.9 to 10.9±3.9mmHg at 6pv (P<0.001) and to 12.7±4.4mmHg at FUpv (P<0.001). LCD was reduced from 465.3±136.4μm to 402.9±126.4μm at 1pv (P<0.001) and maintained similar position at 6pv (394.3±118.4μm; P = 0.170 with respect to 1pv). A significant decrease in the LCD was noted at FUpv (342.8±90.3μm, P<0.001) with respect to 6pv. RNFL thickness increased significantly to 64.9±19.8μm at 1pv (P = 0.005) and subsequently decreased to baseline level at 3pv. Further statistically significant decrease in RNFL thickness with respect to previous visit was found at 6pv and at FUpv (56.4±15.6μm and 55.0±14.0μm, P = 0.023 and P = 0.045, respectively). A thinner RNFL thickness at FUpv was not related to the LCD at FUpv (P = 0.129) but was correlated with ΔLCD/Δt at FUpv (P = 0.003). The ΔRNFL/Δt at FUpv was statistically significantly correlated with ΔLCD/Δt at FUpv (P<0.001). CONCLUSIONS:This is the first study that considers direct correlation between the rate of change in LCD with the rate of RNFL thinning over time. A thinner RNFL thickness following glaucoma surgery was associated with the rate of LCD reduction, not with position of the lamina cribrosa at the FUpv

Number of subjects, mean age and gender ratio of subjects with single and double-peak-shape in CIP signal (ODP) for the four considered groups.

<p>CIP – Corneal Indentation Pulse; ODP – ocular dicrotic pulse; CG – control group; GODA – glaucoma suspects with glaucomatous optic disc appearance; POAG – primary open angle glaucoma; PACG – primary angle closure glaucoma; GAT – Goldmann applanation tonometry.</p

Glaucomatous and Age-Related Changes in Corneal Pulsation Shape. The Ocular Dicrotism

<div><p>Purpose</p><p>To ascertain whether the incidence of ocular dicrotic pulse (ODP) increases with age, it is more pronounced in glaucomatous than in normal eyes and whether it is related to cardiovascular activity.</p><p>Methods</p><p>261 subjects aged 47 to 78 years were included in the study and classified into four groups: primary open angle glaucoma (POAG), primary angle-closure glaucoma (PACG), glaucoma suspects with glaucomatous optic disc appearance (GODA) and the controls (CG). Additionally, in each group, subjects with ODP were divided into two age subgroups around the median age. A non-contact ultrasonic method was used to measure corneal indentation pulse (CIP) synchronically with the acquisition of electrocardiography (ECG) and blood pulse signals. ODP was assessed from the acquired signals that were numerically processed in a custom written program.</p><p>Results</p><p>ODP incidence was about 78%, 66%, 66% and 84% for CG, GODA, POAG, and PACG group, respectively. With advancing age, the ODP incidence increased for all subjects (Δ = 12%), the highest being for the PACG and POAG groups (Δ = 30%). GODA group did not show an age-related increase in the incidence of ODP.</p><p>Conclusions</p><p>The ocular dicrotism, measured with non-contact ultrasonic method, was found to be a common phenomenon in elderly subjects. The increased ODP incidence in PACG and POAG group may correspond to either higher stiffness of glaucoma eyes, biochemical abnormalities in eye tissues, changes in ocular hemodynamics, may reflect the effect of medications or be a combination of all those factors. The results of GODA group suggest different mechanisms governing their ocular pulse that makes them less susceptible to generating ODP and having decreased predisposition to glaucoma.</p></div

Raw data from Ocular Response Analyzer applied for differentiation of normal and glaucoma patients

Purpose: Presented study describes new parameters calculated from the Ocular Response Analyzer (ORA) raw data. Such an approach can increase the applicability of the ORA in ophthalmic diagnosis. Among many proposed and examined by us parameters from raw data of the air pressure and applanation curves, only a few were chosen and then applied for characterizing a selected group of patients. Methods: The study included healthy subjects in a control group and patients divided into 2 groups: suspect and glaucoma. A series of four ORA measurements were taken from each subject. The raw ORA data were numerically analyzed and new parameters were calculated from the ORA curves for each measurement. Comparative analysis was carried out for the newly proposed parameters (and original parameters from the ORA device). Results: This interesting finding is that the new parameters showed a statistically significant ability to distinguish the glaucoma suspect group from healthy and glaucomatous patients. Moreover comparable or higher repeatability than for IOPg and CH was obtained. Conclusion: Raw data from the ORA enables definition and numerical analysis of new parameters, characterizing every measurement, which can be successfully used for describing an individual eye and differentiating between some specific groups of patients

The results of two way ANOVA (with the given signal parameter being the dependent variable and age and the subject group being the two independent variables).

<p>Statistically significant differences satisfying the criterion of equality of variances are marked in bold font.</p><p>CG – control group; GODA – glaucoma suspects with glaucomatous optic disc appearance; POAG – primary open angle glaucoma; PACG – primary angle closure glaucoma; <i>τ</i>(ECG, BPL) – time delay between R wave peak of ECG and systolic BPL peak; <i>τ</i>(ECG, maxODP₁) – time delay between R wave peak of ECG and the first major ODP maximum; <i>τ</i>(ECG, maxODP₂) – time delay between R wave peak of ECG and the second major ODP maximum; <i>τ</i>(BPL, maxODP₁) – time delay between systolic BPL peak and the first major ODP maximum; <i>τ</i>(BPL, maxODP₂) – time delay between systolic BPL peak and the second major ODP maximum; <i>pre</i>CT – preliminary crest time - time taken from minimum to the first major maximum of ODP shape; CT – crest time - time taken from minimum to maximum of ODP shape; HCT – time duration of heart cycle, taken from R peak to the next R peak of ECG shape; <i>pre</i>RCT = <i>pre</i>CT/HCT*100% – preliminary relative crest time; RCT = CT/HCT*100% – relative crest time and HR – the heart rate.</p

Incidence of ODP in the two age subgroups.

<p>ODP – ocular dicrotic pulse; CG – control group; GODA – glaucoma suspects with glaucomatous optic disc appearance; POAG – primary open angle glaucoma; PACG – primary angle closure glaucoma.</p

Illustration of typical averaged shapes of ODP, BPL and ECG signals for patient with PACG.

<p>The shapes of presented signals were averaged for one heart cycle and the considered signal parameters are following: <i>τ</i>(ECG, BPL) – time delay between R wave peak of ECG and systolic BPL peak; <i>τ</i>(ECG, maxODP₁) – time delay between R wave peak of ECG and the first major ODP maximum; <i>τ</i>(ECG, maxODP₂) – time delay between R wave peak of ECG and the second major ODP maximum; <i>τ</i>(BPL, maxODP₁) – time delay between systolic BPL peak and the first major ODP maximum; <i>τ</i>(BPL, maxODP₂) – time delay between systolic BPL peak and the second major ODP maximum; <i>pre</i>CT – preliminary crest time - time taken from minimum to the first major maximum of ODP shape; CT – crest time - time taken from minimum to maximum of ODP shape; HCT – time duration of heart cycle, taken from R peak to the next R peak of ECG shape.</p

Influence of eye biometrics and corneal micro-structure on noncontact tonometry

<div><p>Purpose</p><p>Tonometry is widely used as the main screening tool supporting glaucoma diagnosis. Still, its accuracy could be improved if full knowledge about the variation of the corneal biomechanical properties was available. In this study, Optical Coherence Tomography (OCT) speckle statistics are used to infer the organisation of the corneal micro-structure and hence, to analyse its influence on intraocular pressure (IOP) measurements.</p><p>Methods</p><p>Fifty-six subjects were recruited for this prospective study. Macro and micro-structural corneal parameters as well as subject age were considered. Macro-structural analysis included the parameters that are associated with the ocular anatomy, such as central corneal thickness (CCT), corneal radius, axial length, anterior chamber depth and white-to-white corneal diameter. Micro-structural parameters which included OCT speckle statistics were related to the internal organisation of the corneal tissue and its physiological changes during lifetime. The corneal speckle obtained from OCT was modelled with the Generalised Gamma (GG) distribution that is characterised with a scale parameter and two shape parameters.</p><p>Results</p><p>In macro-structure analysis, only CCT showed a statistically significant correlation with IOP (R² = 0.25, <i>p</i><0.001). The scale parameter and the ratio of the shape parameters of GG distribution showed statistically significant correlation with IOP (R² = 0.19, <i>p</i><0.001 and R² = 0.17, <i>p</i><0.001, respectively). For the studied group, a weak, although significant correlation was found between age and IOP (R² = 0.053, <i>p</i> = 0.04). Forward stepwise regression showed that CCT and the scale parameter of the Generalised Gamma distribution can be combined in a regression model (R² = 0.39, <i>p</i><0.001) to study the role of the corneal structure on IOP.</p><p>Conclusions</p><p>We show, for the first time, that corneal micro-structure influences the IOP measurements obtained from noncontact tonometry. OCT speckle statistics can be employed to learn about the corneal micro-structure and hence, to further calibrate the IOP measurements.</p></div