Relationship between optic disc cupping change and intraocular pressure control in adult glaucoma 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.

The Acute Morphologic Changes That Occur at the Optic Nerve Head Induced by Medical Reduction of Intraocular Pressure

PURPOSE

The mechanical theory of glaucoma postulates that raised intraocular pressure (IOP) causes laminar distortion resulting in damage to axons at the optic nerve head. There is some evidence that the change in morphology may occur over a short time course. The aim of this paper was to detail the acute morphologic changes at the optic nerve head when IOP was lowered with medical therapy in a clinical population.

METHODS

Subjects referred to the glaucoma clinic that had a documented IOP of over 28 mm Hg, on no treatment, in one or both eyes were included. Tonometry, pachymetry, and scanning laser ophthalmoscopy were performed before and after lowering IOP with topical apraclonidine and oral acetazolamide. The significance of change in outcome variables was assessed using a paired t test allowing for dependence within subjects and, for sensitivity, with a nonparametric Wilcoxon signed-rank test.

RESULTS

Data were obtained from 38 eyes of 19 patients with a mean age of 67 years. After lowering IOP for only 1 hour, there was a significant decrease in mean cup volume (mean change in volume below surface 26.8 microm3, P< or =0.001) and mean cup depth (13.8 microm, P<0.01), there being a corresponding increase in mean rim area (37.3 microm2, P<0.034). There was no statistically significant change in central corneal thickness after administration of the IOP lowering medications.

CONCLUSIONS

In the present study, it was shown that acute and statistically significant alterations in optic disc morphology occur when IOP is lowered medically with a combination of topical apraclonidine and systemic acetazolamide. The technique, therefore, may be useful to further investigate subgroups of glaucomatous eyes and test etiologic hypotheses.

Gold standard medical therapy for glaucoma: defining the criteria identifying measures for an evidence-based analysis

BACKGROUND

Over the past decade, several new medical therapies have become available for the treatment of primary open-angle glaucoma (POAG). A systematic evidence-based approach for identifying an optimal therapeutic agent is lacking.

OBJECTIVES

The aims of this review were to critically evaluate published treatment recommendations for POAG and, based on a systematic review of the literature, to develop criteria that would define a "gold standard" medical therapy that reflects new treatment advances and established therapeutic goals.

METHODS

A MEDLINE search spanning the years 1966 to 2002 and using the search terms gold standard, drug of choice, agent of choice, benchmark, ophthalmology, eye, and glaucoma was conducted and the results reviewed by a panel of 15 experts in the field of glaucoma. Published treatment recommendations for POAG were discussed. Criteria, anchored to medical evidence, for distinguishing a standard of medical therapy for POAG were defined.

RESULTS

The terms connoting a gold standard therapy were found in only 258 of approximately 368,000 ophthalmology-related citations and 53 of almost 23,000 glaucoma citations, validating the need to define therapeutic standards. The lack of recommendations for the use of new classes of ocular hypotensive agents was acknowledged. Criteria identified to evaluate intraocular pressure (IOP)-lowering agents as gold standards included the following: efficacy in reducing IOP consistently over a 24-hour period to a level that will preserve the visual field and protect the optic nerve without inducing tachyphylaxis and tolerance, paucity of local and systemic adverse effects, promotion of patient compliance, and applicability in diverse patient populations.

CONCLUSIONS

These criteria should be employed as measures for evidence-based analyses to evaluate available and future IOP-lowering medical therapies for POAG. The conceptual framework presented may be applicable to other therapeutic areas.

Factors affecting awareness and knowledge of glaucoma among patients presenting to an urban emergency department

BACKGROUND

Until advanced, glaucoma is asymptomatic. For early diagnosis to occur, patients may need to be aware of it and seek assessment regularly. People who have risk factors for glaucoma may have a greater awareness of the disease.

METHODS

Patients presenting to an urban hospital emergency department were surveyed with a brief questionnaire to assess their knowledge of glaucoma. Data was collected about their gender, age, family history of glaucoma and presence of systemic hypertension, diabetes, Raynaud's phenomenon, migraines and myopia.

RESULTS

Women (Odds ratio 2.3; 95% CI 1.4-3.7; P < 0.01), people who were 40 years or older (Odds ratio 2.2; 95% CI 1.1-4.4; P < 0.05) and those who were aware of a family history of glaucoma (Odds ratio 15.7; CI 5.5-45.3; P < 0.01) knew significantly more about the disease than others. People with other risk factors did not demonstrate significantly greater knowledge despite 89% of all participants having had a previous eye examination.

CONCLUSION

This information may be useful to predict which patients may know about glaucoma when they present for an eye examination and who should be targeted in public health campaigns.

Optic disc changes following trabeculectomy: longitudinal and localisation of change

AIMS

To determine whether there were any changes in the optic disc at 2 years after trabeculectomy. To determine the factors that most influenced change and whether change was localised to any region of the optic disc.

METHODS

95 patients undergoing routine trabeculectomy as part of the ongoing Moorfields/MRC 5-fluorouracil trial were recruited into the study. Eyes were imaged preoperatively (4 (SD 3) weeks) with the Heidelberg retina tomograph (HRT, Heidelberg Engineering), and at 3 months (SD 2 weeks), 1 year (SD 1 month), and 2 years (SD 1 month) after surgery. Parameters investigated for change were rim area, rim volume, and maximum cup depth. The predefined segment analysis available on the HRT analysis software was used to determine segmental change.

RESULTS

The images of 70 patients were analysed. Intraocular pressure reduced from 22.25 (SD 3.76) mm Hg, at the time of preoperative imaging to 15.27 (SD 4.96) mm Hg at 3 months, 14.38 (SD 3.89) mm Hg at 1 year, and 13.80 (SD 3.54) mm Hg at 2 years after trabeculectomy. An increase in rim area and rim volume was present at all time points after surgery, but was only found to be statistically significant at 2 years after surgery. Maximum depth of cup reduced by month 3 and month 12, but showed a slight increase at 2 years after surgery, although this was still lower than the preoperative measure. Segmental analysis found a significant change in rim volume in the nasal, inferonasal, superonasal, and superotemporal regions at 2 years after surgery. No significant regional localisation for change was found at any other time point or in any other parameter investigated.

CONCLUSIONS

Reversal of disc cupping is present at 2 years after trabeculectomy. The factor most influencing change is reduction of intraocular pressure. Segmental analysis showed that change in rim volume was greatest in the nasal, inferonasal, superonasal and superotemporal regions at 2 years.

Age related compliance of the lamina cribrosa in human eyes

AIMS

To investigate changes in the mechanical compliance of ex vivo human lamina cribrosa with age.

METHODS

A laser scanning confocal microscope was used to image the surface of the fluorescently labelled lamina cribrosa in cadaver eyes. A method was developed to determine changes in the volume and strain of the lamina cribrosa created by increases in pressure. The ability of the lamina cribrosa to reverse its deformation on removal of pressure was also measured.

RESULTS

Volume and strain measurements both demonstrated that the lamina cribrosa increased in stiffness with age and the level of pressure applied. The ability of the lamina cribrosa to regain its original shape and size on removal of pressure appeared to decrease with age, demonstrating an age related decrease in resilience of the lamina cribrosa.

CONCLUSIONS

The mechanical compliance of the human lamina cribrosa decreased with age. Misalignment of compliant cribriform plates in a young eye may exert a lesser stress on nerve axons, than that exerted by the rigid plates of an elderly lamina cribrosa. The resilience of the lamina cribrosa also decreased with age, suggesting an increased susceptibility to plastic flow and permanent deformation. Such changes may be of importance in the explanation of age related optic neuropathy in primary open angle glaucoma.