Anterior-segment morphology and corneal biomechanical characteristics in pigmentary glaucoma

Interocular Asymmetry of Visual Field Loss, Intraocular Pressure and Corneal Parameters in Primary Open-angle Glaucoma

OBJECTIVES

To assess the association between the corneal biomechanical parameters and visual field (VF) loss in patients with asymmetric primary open-angle glaucoma (POAG).

METHODS

A total of 89 POAG patients (50 males, 56.2%) with asymmetric VF loss, aged 65.2 ± 13.3 years old, were enrolled in this study. Asymmetric VF loss was defined as an interocular difference of the global index mean deviation (MD) >2dB. Intraocular pressure (IOP), central corneal thickness (CCT) and corneal biomechanical parameters such as maximum amplitude at the apex of highest concavity (Def ampl HC) were measured. The worse eye was defined as the eye with a smaller MD.

RESULTS

The worse eyes had lower MD (-11.9 ± 6.7 dB vs. -5.3 ± 5.0 dB; P<0.001) and higher IOP (14.6 ± 3.3 vs.13.9 ± 2.6 mmHg, P=0.04) than the better eyes. There was no significant difference between the two groups for CCT. The interocular difference of MD (IDMD) was negatively correlated with the interocular difference of IOP (r=-0.22, P=0.04), while positively correlated with the interocular difference of Def ampl HC (r=0.27, P=0.01). In patients with moderate asymmetric VF loss (IDMD ≥6 dB), the Def ampl HC of the worse eyes group (1.07 ± 0.12 mm) were significantly lower than the better eyes group (1.10 ± 0.11 mm, p=0.02).

CONCLUSION

Asymmetric POAG was associated with asymmetry in IOP and corneal biomechanical parameters but not in CCT. Lower deflection amplitude and higher IOP was found in eyes with more severe visual field damage in POAG patients.

An Iconic Case of Pigmentary Glaucoma: Brief Review of the Literature

Pigment dispersion syndrome and pigmentary glaucoma are two conditions characterized by pigment dispersion originating from the posterior part of the iris and its accumulation on the trabecular meshwork, corneal endothelium, and anterior surface of the lens. The pigment on the trabecular meshwork can cause chronic inflammation with a secondary reduction of its function and an increase in intraocular pressure. The case presented represents a typical example of pigmentary glaucoma in a myopic patient in which all the signs, symptoms, and complications typical of these pathologies were present. We report and describe an 8-year-long follow-up period with clinical and instrumental examinations.

[Biomechanical properties of the cornea as predictors of the effectiveness of selective laser trabeculoplasty]

PURPOSE

To study the changes in central corneal thickness (CCT) and corneal hysteresis (CH) after selective laser trabeculoplasty (SLT) in primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG) after laser peripheral iridotomy (LPI) and to determine their effect on the prognosis of the surgery.

MATERIAL AND METHODS

The prospective study involved 68 eyes with initial PACG after LPI and 74 eyes with initial POAG observed for 6 months. Corneal-compensated IOP (IOPcc), corneal resistance factor (CRF), CH and CCT were studied as the predictors of SLT, which was considered successful when IOPcc decreased by 20% or more from the baseline without additional hypotensive therapy and/or repeated SLT.

RESULTS

In both forms of glaucoma, CCT increased within the first hour after SLT: 567±24.08 µm (p=0.001) in POAG, and 572±21.41 µm (p=0.000) - persisting for over a month - in PACG. CCT correlated with laser energy at all stages of the examination both in POAG and PACG patients. The following predictors of SLT failure were determined: CH (p=0.000 in PACG and p=0.001 in POAG), as well as initial IOP (p=0.010 in PACG and p=0.016 in POAG) and CRF (p=0.003 in PACG and p=0.005 in POAG) and CCT (p=0.023 in PACG and p=0.026 in POAG). The value of anterior chamber angle (ACA) was a predictor only for PACG (p=0.011).

CONCLUSION

SLT leads to an increase in CCT, which lasts longer in PACG after LPI than in POAG and correlates with the level of laser energy. Lower CH and initially higher IOP are the common predictors of SLT failure in the long term for both forms of glaucoma. Smaller ACA have a negative prognostic sign in POAG.

Pigment dispersion syndrome and pigmentary glaucoma: a review and update

INTRODUCTION

Pigment dispersion syndrome (PDS) is a condition where anomalous iridozonular contact leads to pigment dispersion throughout the anterior segment and the released pigment is abnormally deposited on various ocular structures.

CLINICAL PRESENTATION

The clinical presentation of PDS is defined by the presence of pigmented cells on the corneal endothelium, an increase of pigmentation of the trabecular meshwork, and mid-periphery transillumination defects of the iris. This syndrome, more common in myopes, is usually bilateral and can be associated with ocular hypertension or glaucoma. Secondary open-angle pigmentary glaucoma (PG) can develop due to reduction of the outflow of aqueous humour and consequent increase in intraocular pressure leading to glaucomatous optic neuropathy. Diagnosis of PG is commonly between 40 and 50 years of age, occurring more frequently in men. The advent of ultrasound biomicroscopy and anterior segment optical coherence tomography has contributed to enhancing our knowledge on the condition. Typical alterations of the anterior segment are the posterior insertion of the iris and iris concavity. Treatment of PG should be initiated early to hinder disease progression, glaucomatous damage, and vision loss. Management is based on medical therapy, laser iridotomy, selective laser trabeculoplasty, and filtration procedures.

CONCLUSIONS

The differential diagnosis of PDS with other disorders can be challenging and awareness of the condition together with meticulous ophthalmologic examination allows early diagnosis followed by appropriate management strategies. The present review is a comprehensive report on the clinical characteristics, pathogenesis, current management, and status quo of PDS and PG.

Corneal biomechanical data and biometric parameters measured with Scheimpflug-based devices on normal corneas

AIM

To analyze the correlations between ocular biomechanical and biometric data of the eye, measured by Scheimpflug-based devices on healthy subjects.

METHODS

Three consecutive measurements were carried out using the corneal visualization Scheimpflug technology (CorVis ST) device on healthy eyes and the 10 device-specific parameters were recorded. Pentacam HR-derived parameters (corneal curvature radii on the anterior and posterior surfaces; apical pachymetry; corneal volume; corneal aberration data; depth, volume and angle of the anterior chamber) and axial length (AL) from IOLMaster were correlated with the 10 specific CorVis ST parameters.

RESULTS

Measurements were conducted in 43 eyes of 43 volunteers (age 61.24±15.72y). The 10 specific CorVis ST data showed significant relationships with corneal curvature radii both on the anterior and posterior surface, pachymetric data, root mean square (RMS) data of lower-order aberrations, and posterior RMS of higher-order aberrations and spherical aberration of the posterior cornea. Anterior chamber depth showed a significant relationship, but there were no significant correlations between corneal volume, anterior chamber volume, mean chamber angle or AL and the 10 specific CorVis ST parameters.

CONCLUSIONS

CorVis ST-generated parameters are influenced by corneal curvature radii, some corneal RMS data, but corneal volume, anterior chamber volume, chamber angle and AL have no correlation with the biomechanical parameters. The parameters measured by CorVis ST seem to refer mostly to corneal properties of the eye.

Corneal biomechanics in asymmetrical normal-tension glaucoma

Purpose

We aimed to assess corneal biomechanics using the ocular response analyzer in patients with normal-tension glaucoma (NTG), and to evaluate the relationship between corneal biomechanics and visual field loss.

Methods

This was a prospective observational case series including patients with bilateral asymmetric NTG. For all patients, corneal hysteresis (CH), corneal resistance factor (CRF), CH − CRF difference, and central corneal thickness values were matched against the mean deviation (MD) of the visual field and the cup/disc ratio. For paired-eye comparison in each patient, both eyes were categorized into a better-eyes group and a worse-eyes group according to lower and higher corneal-compensated intraocular pressure readings, respectively. Statistical analysis was carried out with the independent-samples Student’s t-test, and the level of statistical significance was set at 0.05. Correlation was assessed using Pearson’s correlation coefficient.

Results

The study included 240 eyes of 120 patients. CH was inversely proportional to the MD in the visual field (P=0.01). CRF in both eyes was inversely proportional to the MD of the visual field (P=0.01). CH − CRF difference was directly proportional to the MD of the visual field (P=0.01). For paired-eye comparison, lower corneal-compensated intraocular pressure was associated with higher CH, higher CRF, smaller cup/disc ratio, and less deterioration of MD of visual field.

Conclusion

CH, CRF, and CH − CRF are more powerful predictors of NTG progression than central corneal thickness.