[Quantification and progression of the visual field defect in glaucoma without hypertension, glaucoma simplex and pigmentary glaucoma. A clinical study with the Delta Program of the 201 Octopus perimeter]

Comparison of retinal ganglion cell-related layer asymmetry between early glaucoma eyes with superior and inferior hemiretina damage

Aim

To compare retinal ganglion cell (RGC)-related layer thickness asymmetry between early open-angle glaucoma (EG) eyes with superior and inferior hemiretina damage.

Methods

This was a retrospective study including 95 EG eyes (mean deviation >−2 dB, including 43 preperimetric glaucoma eyes) with photographically determined glaucomatous retinal nerve fibre layer defect and disc change confined to one hemiretina, and 93 age, sex and refraction matched normal subjects as controls. Ganglion cell complex, ganglion cell layer+inner plexiform layer and circumpapillary retinal nerve fibre layer thickness measured by spectral domain optical coherence imaging were compared between the affected and unaffected hemiretinae within each glaucoma eye as well as to those of the corresponding hemiretina of normal control eyes.

Results

Intraeye comparison revealed that there was no significant difference in all parameters between the affected and unaffected hemiretinae in eyes with superior hemiretina damage (p=0.110~0.343) while all parameters were thinner in the affected inferior hemiretina compared with the unaffected superior hemiretina in eyes with inferior hemiretina damage (p<0.001). The affected hemiretina of both groups were thinner compared with normal controls (p<0.001). All parameters of the unaffected hemiretina of eyes with superior hemiretina damage were thinner than normal controls (p<0.001), while eyes with inferior hemiretina damage showed no significant difference compared with those of their corresponding hemiretina of normal eyes (p=0.086~0.924).

Conclusion

The pattern of RGC damage in early stage glaucoma may differ depending on which horizontal hemiretina is affected first.

Update on Normal Tension Glaucoma

Normal tension glaucoma (NTG) is labelled when typical glaucomatous disc changes, visual field defects and open anterior chamber angles are associated with intraocular pressure (IOP) constantly below 21 mmHg. Chronic low vascular perfusion, Raynaud's phenomenon, migraine, nocturnal systemic hypotension and over-treated systemic hypertension are the main causes of normal tension glaucoma. Goldmann applanation tonometry, gonioscopy, slit lamp biomicroscopy, optical coherence tomography and visual field analysis are the main tools of investigation for the diagnosis of NTG. Management follows the same principles of treatment for other chronic glaucomas: To reduce IOP by a substantial amount, sufficient to prevent disabling visual loss. Treatment is generally aimed to lower IOP by 30% from pre-existing levels to 12-14 mmHg. Betaxolol, brimonidine, prostaglandin analogues, trabeculectomy (in refractory cases), systemic calcium channel blockers (such as nifedipine) and 24-hour monitoring of blood pressure are considered in the management of NTG. The present review summarises risk factors, causes, pathogenesis, diagnosis and management of NTG.

Systems for staging the amount of optic nerve damage in glaucoma: a critical review and new material

The evaluation of the appearance of the optic disk is central to the diagnosis and management of patients with glaucoma. Grouping patients into categories, monitoring change, and quantitating the rate of change all require some type of quantitative staging of the amount of damage. Though the scientific literature regarding the appearance of the optic disk in glaucoma is extensive, there is remarkably little about quantitative staging of the amount of damage. We have identified eight systems, including the cup/disk ratio system of Armaly. Most of the earlier systems suffer from a failure to take into account the importance of the size of the optic disk. Furthermore, only one system includes early amounts of damage. This review is a critical appraisal of the known methods for staging optic disk damage in glaucoma, including the recent Disk Damage Likelihood Scale, which appears to offer substantial advantages over the other systems.

A new classification of glaucoma including focal glaucoma

This report suggests a new method of classifying glaucoma based upon the appearance of the optic nerve. One subdivision of this classification, focal glaucoma, is discussed in some detail. As is true for all classifications, the system proposed will not be a permanent one. Nor is it intended to be all inclusive. Its purpose is not to replace the system which at present is based on the mechanism for intraocular pressure elevation, i.e., angle-closure glaucoma, open-angle glaucoma, etc., but rather to provide a means by which various subtypes of glaucoma can be better differentiated.

Current concepts in pigmentary glaucoma

Since its initial description over 50 years ago as a rare clinical entity, pigmentary glaucoma has become recognized as one of the most common forms of secondary open-angle glaucoma. Pigmentary glaucoma affects a much younger patient population than most other forms of open-angle glaucoma, and has a predilection for Caucasian males with myopia. Hallmarks of this disease include midperipheral iris transillumination defects, Krukenberg spindles and a heavily pigmented trabecular meshwork. The mechanism of pigment dispersion appears to be a rubbing between iris pigment epithelium and packets of lens zonules, possibly associated with an inherent abnormality of the pigment epithelium, and the mechanism of aqueous outflow obstruction is believed to involve accumulation of the pigment granules in the trabecular meshwork, followed by denudation, collapse, and sclerosis of the trabecular beams. Current management includes standard antiglaucoma drugs, laser trabeculoplasty, and filtering surgery, although research suggests the possibility of earlier intervention with medication or surgery to arrest the pigment dispersion and reverse or prevent the secondary glaucoma.

Graphical analysis of topographical trends (GATT) in automated perimetry

The assessment of change in analysis of visual fields is one of the most difficult tasks in automated perimetry. A new, computerized method shows the original fields and the topographic trends in one easy graphic display. This new way of analysis the 'GATT' superimposes the grayscale maps of two fields with a simple logic, producing the following patterns: all stable, unchanged areas are displayed normally; in changed areas, the grayscale of the first and the second field are mixed in the form of stripes. The contrast between the stripes indicates the amount of change. The orientation of the stripes depends on the direction of change: horizontal stripes mean deterioration, vertical stripes mean improvement. The GATT is also able to compare 4 fields, using the same patterns. In addition, a scatterboard without stripes indicates areas of high fluctuation, but without a significant change in the course of the 4 fields. The GATT enables a quick, quantitative judgement of the trends of visual fields.

Long-term studies of visual field changes by means of computerized perimetry (Octopus 201) in eyes with glaucomatous field defects after normalization of the intra-ocular pressure

126 eyes with open-angle glaucoma and defects of the visual field were studied over five years (+/-1.3) by repeated perimetries with Octopus Perimeter, Program 31, after the IOP had been normalized from 26.49 mm Hg to 19 mm Hg. All patients had suffered visual field defects in the period with increased pressure preceding our study and had many perimetric examinations before. The aim of the study was to check the behaviour of the visual field defects after pressure normalization. For evaluation of the visual fields, the upper most line of the test-points and the 6 test-points surrounding the blind spot were disregarded. The evaluation of each field and the comparison with preceding fields (no change, better, or worse) were done by the symmetry test of Bowker instead of the Delta Program, taking into account each of the 61 test-points with a significance level of 5%. In each patient the eye with the heavier field loss was evaluated.

RESULTS

67% of all eyes had no change during the observation time, 12% became better, and 21% worse. Improvement of the visual fields occurred even in old age: 10% became better in the age-group over 70 years. The total loss decreased in the 15 eyes which improved by 269 dB. In eyes which deteriorated, the total loss increased by 282 dB. The good news of this study is that normalization of IOP can stop the further decay of the visual-field in 67% and an improvement of the field loss is possible even in old age of with heavy field loss.(ABSTRACT TRUNCATED AT 250 WORDS)