Scanning laser ophthalmoscopy of the optic nerve head in exfoliation glaucoma and ocular hypertension with exfoliation syndrome

Baseline structural characteristics of the optic nerve head and retinal nerve fiber layer are associated with progressive visual field loss in patients with open-angle glaucoma

Aims

To examine the relationship between baseline structural characteristics of the optic nerve head (ONH) and retinal nerve fiber layer (RNFL) and functional disease progression in patients with open-angle glaucoma (OAG) over 5 years.

Methods

112 OAG patients were prospectively examined at baseline and every 6 months over a period of five years. Structural glaucomatous changes were examined with optical coherence tomography (OCT) and Heidelberg retinal tomography-III (HRT-III), and functional disease progression with automated perimetry (Humphrey visual fields). Cox proportional hazard models were used to assess the relationship between baseline structural measurements and functional disease progression.

Results

From baseline over a 5-year period, statistically significant increases were found in OCT disc (D) area (p<0.001), cup (C) area (p<0.001), C/D area ratio (p<0.001), C/D horizontal ratio (p<0.001), C/D vertical ratio (p = 0.018), and a decrease in superior RNFL thickness (p = 0.008). Statistically significant increases were found in HRT-III C volume (p = 0.021), C/D area ratio (p = 0.046), mean C depth (p = 0.036), C shape (p = 0.008), and height variation contour (p = 0.020). Functional disease progression was detected in 37 of the 112 patients (26 of European descent and 11 of African descent; 33%). A statistically significant shorter time to functional progression was seen in patients with larger baseline OCT D area (p = 0.008), C area (p = 0.003), thicker temporal RNFL (p = 0.003), and in patients with a larger HRT-III C area (p = 0.004), C/D area ratio (p = 0.004), linear C/D ratio (p = 0.007), C shape (p = 0.032), or smaller rim area (p = 0.039), rim volume (p = 0.005), height variation contour (p = 0.041), mean RNFL thickness (p<0.001), or RNFL cross-sectional area (p = 0.002).

Conclusion

Baseline ONH and RNFL structural characteristics were associated with a significantly shorter time to functional glaucomatous progression and visual field loss through the five-year period in OAG patients.

Structure-Function Correlation Using Confocal Laser Ophthalmoscope in Primary Open-Angle Glaucoma and Pseudoexfoliative Glaucoma

PURPOSE

To compare Heidelberg Retina Tomograph (HRT) optic disc parameters and structure-function correlation between primary open-angle glaucoma (POAG) and pseudoexfoliative glaucoma (PEXG).

DESIGN

Prospective, observation case series.

PATIENTS AND METHODS

A total of 54 POAG and 33 PEXG cases, consecutively recruited from a University Glaucoma Service, underwent a comprehensive ophthalmic examination, including HRT optic disc imaging. Glaucoma definition required the presence of both structural and functional damage. One eye per subject was included in the analysis. T test, Mann-Whitney U test, and analysis of covariance were used to compare HRT parameters between POAG and PEXG, adjusting for age, mean deviation (MD) in the visual field, intraocular pressure, and disc area. The correlation between HRT and MD was assessed in each group.

RESULTS

Cup area (P=0.048), height variation contour (P=0.016), and cup/disc area ratio (P=0.023) were higher in POAG, whereas the mean retinal nerve fiber layer thickness (P=0.048), retinal nerve fiber layer cross-section area (P=0.044), and rim area (P=0.048) were lower in POAG, compared with PEXG. The correlation of HRT parameters with MD was significant only in the POAG group.

CONCLUSIONS

At a similar level of functional damage, POAG subjects presented with more pronounced structural damage than PEXG subjects. The correlation between HRT and visual field parameters was more evident in POAG, compared with PEXG.

Comparison of the effects of dorzolamide/timolol and latanoprost/timolol fixed combinations upon intraocular pressure and progression of visual field damage in primary open-angle glaucoma

OBJECTIVE

To report the long-term effect of the dorzolamide/timolol (DTFC) and latanoprost/timolol (LTFC) fixed combinations on intraocular pressure (IOP) and visual field defects over time in naïve primary open-angle glaucoma (POAG) patients.

STUDY DESIGN AND METHODS

Prospective, 4-year, open-label, interventional study.

SETTING

high-volume outpatient clinic.

PATIENTS

178 patients were assigned to receive medical treatment with either DTFC or LTFC.

INTERVENTION

over 4 years, tri-monthly IOP and yearly visual field assessment (Octopus 101, Program G2). outcomes: effect of treatment on IOP, visual field indices mean defect (MD), and visual field indices variance loss (VL) over time.

RESULTS

DTFC and LTFC significantly (p < or = 0.001) reduced mean IOP over time (from 22.6 +/- 3.0 to 13.8 +/- 1.9 mmHg and from 22.3 +/- 4.0 to 14.7 +/- 1.9 mmHg, respectively). In all, 56 patients (70.9%) and 14 (17.9%) showed a significant MD improvement in the DTFC- and LTFC-treated groups, respectively, p = 0.0001. DTFC progressively and significantly decreased mean VL (from 30.21 +/- 23.88 to 8.11 +/- 8.50 dB). Mean sensitivity slopes during follow-up were 1.14 dB/year and -0.34 dB/year for DTFC and LTFC treatment groups, respectively; p = 0.028.

CONCLUSION

Both treatments significantly reduced IOP as compared with baseline. Additionally, treatment with dorzolamide/timolol fixed combination seem to be effective in preventing glaucomatous visual field progression. This study has some limitations that should be noted, among them its open-label design.

Optic disc morphology--rethinking shape

Morphometrics, a branch of morphology, represents the study of size and shape components of biological form and their variation in the population. Assessment of optic disc morphology is essential in the diagnosis and management of many ophthalmic disorders. Much work has been performed to characterize size-related parameters of the optic disc; however, limited information is available on shape variation in the general population. In contrast to optic disc or cup sizes, which are conceptually meaningful variables with a defined unit of measurement, there are few metric constructs by which to quantify, visualize and interpret variation in optic disc or cup shape. This has significance in ophthalmic diseases with a genetic basis as recent evidence has suggested that optic disc shape may be heritable. Conventional optic disc shape measures of 'ovality' and 'form-factor' reduce a complex structure to a single number and eliminate information of potential diagnostic relevance from further analyses. The recent advent of 'geometric morphometrics', a branch of statistics that incorporates tools from geometry, biometrics and computer graphics in the quantitative analysis of biological forms, has enabled spatial relationships in shape data to be retained during analysis. The analytical methods employed in geometric morphometrics can be separated into two distinct groups: landmark-based (e.g. Procrustes analysis, thin-plate splines) and boundary outline techniques (e.g. Fourier analysis). In this review, we summarize current approaches to the study of optic disc morphology, discuss the underlying theory of geometric morphometrics within the context of analytical techniques and then explore the contemporary relevance of the subject matter to several biological fields. Finally we illustrate the potential application of geometric morphometrics to the specific problem of optic disc shape and glaucoma assessment.

Frequency Doubling Technology and Scanning Laser Tomography in Eyes With Generalized Enlargement of Optic Disc Cupping

PURPOSE

To characterize functional and structural changes in eyes with generalized enlargement of optic disc cupping (vertical cup/disc ratio > or = 0.8), normal intraocular pressure, normal standard achromatic automated perimetry (SAP) results, and no other ophthalmoscopic findings suggesting glaucoma (large C/D eyes) using frequency doubling technology (FDT) and the Heidelberg Retina Tomograph (HRT).

METHODS

This comparative observational case series included 30 large C/D eyes (30 subjects), 17 eyes (17 patients) with early-stage normal tension glaucoma with generalized enlargement of optic disc cupping (NTG eyes), and 25 eyes from 25 normal subjects (normal eyes). Results with Humphrey 30-2, FDT N-30 threshold programs, and HRT were compared among these groups. Large C/D eyes were subdivided into FDT-normal and -abnormal eyes according to the predetermined criteria and HRT parameters were compared among them.

RESULTS

No significant difference was seen in HRT parameters between the large C/D and NTG eyes. In the large C/D eyes, FDT mean deviation was lower than in the normal eyes and higher than in the NTG eyes, whereas FDT pattern standard deviation was smaller than in the NTG eyes (P = 0.02-0.03). Among HRT parameters, only cup shape measure (CSM) showed significant negative correlation with FDT mean deviation in the large C/D eyes. Between FDT-normal and -abnormal subgroups, only CSM showed significant difference (P < 0.01).

CONCLUSION

Frequency doubling technology showed abnormalities in large C/D eyes. Only CSM showed significant correlation with FDT result and difference between those with normal and abnormal FDT results. In management of large C/D eyes, FDT and CSM will be useful to detect functional and structural change.