The rate of progression of scotomas in glaucoma

Optic disk appearances in primary open-angle glaucoma

Primary open-angle glaucoma almost certainly develops in a multifactorial manner, with interplay between numerous risk factors affecting the disease. These risk factors, in addition to intraocular pressure, include a number of cardiovascular factors. Some of these factors may determine the appearance of the damaged glaucomatous optic nerve head. Patients with four specific optic disk appearances have been investigated, and differences have been identified in their demographic characteristics, prevalence of certain risk factors, the pattern of visual field damage, and circulatory abnormalities in their retrobulbar vessels. The findings provide evidence of the existence of subgroups of primary open-angle glaucoma with correlations between risk factor and type of optic disk. A reliable method by which the different disk appearances could be distinguished in an objective manner would be clinically valuable, and the scanning laser ophthalmoscope has shown potential promise to achieve this. The results of studies relating to various glaucomatous optic disk appearances are presented and discussed.

Retrospective analysis of risk factors for late presentation of chronic glaucoma

BACKGROUND

Why some individuals present to the ophthalmologist in the early stages of chronic glaucoma but others present with very advanced visual field loss is a question which has received little attention. This study is an attempt to identify some basic characteristics of people who present with late glaucoma.

METHODS

A retrospective case-control study by medical record review was employed. 100 cases and 100 controls were identified from the notes of patients presenting to Moorfields Eye Hospital glaucoma service between July 1993 and July 1995. Cases were defined as new patients presenting with absolute field loss within five degrees of fixation and a cup to disc ratio of greater than 0.8 in one or both eyes. Controls were new patients with no absolute field loss within 20 degrees in either eye, but otherwise typical glaucomatous field loss and a cup to disc ratio of greater than 0.5 or a difference of 0.2 or more between the discs.

RESULTS

The ethnic origin, sex, referral source, presenting IOP, and age of the subjects studied were independently associated with late presentation. An African Caribbean patient is estimated to be four and a half times more likely to attend with advanced field loss than a white patient of similar age, sex, IOP, and referral source (adj OR: 4.55, 95% CI [1.57, 13.18]). A female patient is estimated to be one third (0.34, [0.15, 0.74]) as likely to attend late than a male patient of the similar age, IOP, ethnic origin, and referral source. A patient referred via any source other than an optometrist with the correct diagnosis is estimated to be greater than four times (4.32 [1.89, 9.88]) more likely to be a late attender than a patient of the same sex, ethnicity, and similar age but referred with a diagnosis of glaucoma. There was a trend of increasing odds of late presentation with increasing age (adj OR per 10 years, baseline 40-49 years 1.68 [1.22, 2.20]). A patient whose presenting IOP is 21-25 mm Hg is estimated to be a quarter (0.24, [0.09, 0.64]) as likely to attend with advanced field loss than a patient of the same ethnic origin, sex, age, referral source, but with presenting IOP of greater than 31 mm Hg.

CONCLUSIONS

These data strongly suggest that certain subgroups of patients with glaucoma are likely to be at greater risk of presenting with advanced and irremediable field loss.

Low vision perspectives on glaucoma

INTRODUCTION: Glaucoma is one of the major causes of visual impairment, especially in the older population. The aim of this paper is to examine the demographics of patients with glaucoma-induced visual impairment. METHOD: Visual rehabilitation information was analysed for 590 visually impaired patients attending the multi-disciplinary low vision clinic at Kooyong in Melbourne. Data collected included age, subjective assessment of glare, mobility and visual needs, visual acuity (at distance and near), contrast sensitivity, visual field loss or disruption and magnifiers prescribed. An assessment was also made of the patients' psychological status and the members of the multi-disciplinary team involved in their rehabilitation was noted. RESULTS: Glaucoma was the primary cause of visual loss in 8.5 per cent of patients and was a secondary contributor to visual impairment in 5.9 per cent. The mean distance visual acuity was 6/38 and peak contrast sensitivity was 10 dB. Sixty-four per cent of glaucoma patients had magnifiers prescribed to help them achieve their visual needs, which were to read newspapers in the majority of cases. CONCLUSIONS: In the management of low vision patients, it is important to understand the eye disease causing the visual impairment and its effects. The glaucoma sufferer must be treated as a whole person. The psychological state and the need for services such as welfare and mobility training must be considered to enable him or her to enjoy an improved quality of life.

Glaucoma and vasospasm

AIMS/BACKGROUND

To study the vasoactivity of glaucoma patients with four previously described and distinct disc appearances potentially representative of primary open angle glaucoma subgroups.

METHODS

Patients with pure examples of four glaucomatous optic disc types--focal ischaemic, myopic glaucomatous, senile sclerotic, and those with generalised cup enlargement, were selected. A detailed ophthalmic, systemic, drug, and smoking history was taken from the patients who, in addition, underwent assessment of peripheral vasospasm with a laser Doppler flowmeter. Differences between the groups were evaluated using an analysis of variance, Student's t test, Pearson's chi 2 test, Fisher's exact test together with Spearman's and Pearson's correlation tests.

RESULTS

38 patients with focal ischaemic, 37 with myopic glaucomatous, 24 with senile sclerotic, and 24 with discs characterised by generalised cup enlargement met the selection criteria. The group of patients with focal ischaemic discs contained more women (66% versus 32%-50% in the other three groups; p = 0.01) and had a higher prevalence of vasospasm (63% versus 25%-49%; p = 0.01), migraine (32% versus 8%-19%; p = 0.02), and cold extremities (66% versus 17%-30%; p = 0.00003). The group of patients with senile sclerotic discs had a higher prevalence of systemic cardiovascular disease (58% versus 21%-30% in the other three groups; p = 0.01) and thyroid disease (21% cf 0%-8%; p = 0.01) and although their mean age was greater (76 years cf 55-65 years; p < 0.00001) the findings were independent of age. Smoking was unrelated to optic disc type.

CONCLUSION

Vasospasm, previously associated with normal tension glaucoma, and generalised cardiovascular disease both appear to be specific risk factors for the development of particular subgroups of glaucoma and may be independent of absolute intraocular pressure levels exerting effects in patients with both "normal" or "raised" intraocular pressure. The simple assessment as to whether a glaucoma patient suffers from colder extremities than average appeared to be better at distinguishing the focal ischaemic type of glaucoma than the more complex determination of vasospasm using the laser Doppler flowmeter.

Comparison of methods to detect visual field progression in glaucoma

OBJECTIVE

The purpose of the study is to develop alternative statistical approaches for evaluating the trend of visual field series over time and to compare the results to human observers.

DESIGN

Retrospective analysis of visual field results.

PARTICIPANTS

Eighty-three eyes of 83 patients (phakic or pseudophakic) with open-angle glaucoma and 5 or more eligible fields were included in the study.

INTERVENTION

Three experienced observers independently reviewed the field series to determine stability or progression.

MAIN OUTCOME MEASURES

The following additional methods to determine progression of visual field loss were used: (1) pointwise univariate regression analysis and a glaucoma change analysis; (2) univariate regression analysis on visual field indices mean deviation, corrected loss variance, and glaucoma pattern index; (3) pointwise multivariate regression analysis with fixed effects on panel data; and (4) clusterwise multivariate regression analysis with fixed effects on panel data. The results of different statistical methods were compared by determining the pairwise agreement (Cohen's weighted kappa) between each technique and three experienced observers.

RESULTS

Patients were observed for a mean (+/-standard deviation) of 5.6 (+/-1.4) years. The visual fields of 27 (33%) and 56 (67%) eyes were considered to have progressed or remained stable, respectively, based on agreement of at least 2 of 3 observers. Univariate regression analysis on visual field indices was not useful for detection of visual field progression. Pointwise and clusterwise regression analyses with fixed effects on panel data performed as well as pointwise univariate regression analysis compared with human observers (kappa = 0.52, 0.53, and 0.55, respectively). Both methods showed better agreement with human observers than with glaucoma change analysis (kappa = 0.41).

CONCLUSIONS

A new statistical model, multivariate regression analyses with fixed effects on panel data, is an appropriate method to evaluate the course of visual field series over time and shows reasonable agreement with experienced observers and pointwise univariate regression analysis.

Pointwise univariate linear regression of perimetric sensitivity against follow-up time in glaucoma

PURPOSE

The authors compared pointwise univariate linear regression (ULR) of sensitivity against follow-up as an indicator of visual field progression with that of the corresponding ULR of mean deviation (MD) and with the Glaucoma Change Probability (GCP) analysis. The authors determined the influence of the number and sequence of prior examinations on the slope of the pointwise function.

METHODS

Univariate linear regression was undertaken at each stimulus location on the arbitrarily assigned left eyes of 38 patients with glaucoma examined with the Humphrey Field Analyzer Programs 30-2 or 24-2 (stimulus size III, Humphrey Instruments Inc, San Leandro, CA). The mean age was 59.0 years (standard deviation [SD] = 12.9), the mean number of fields per patients was 12.0 (SD = 2.8), and the mean duration of follow-up was 6.0 years (SD = 1.6).

RESULTS

Four patients showed statistically significant MD slopes. Of the 34 patients exhibiting a nonsignificant MD slope, 15 exhibited clusters of at least two contiguous progressing locations. Less than half of these locations were designated as progressing by GCP. The GCP detected less than one third of the locations considered progressing by ULR for the last six fields in the series: this was attributed to the nonlinear nature of the decline in sensitivity.

CONCLUSIONS

The degree of agreement between the outcomes of ULR and GCP was dependent on the quality of the collected data, the magnitude of the baseline sensitivity, the extent and type of the subsequent visual field progression, and the position of the fields within the examination series. Good agreement was illustrated at those locations where the deterioration fell outside the limits of expected variability in stable glaucoma.

Rate of progression in open-angle glaucoma estimated from cross-sectional prevalence of visual field damage

PURPOSE

To estimate the rate of visual field loss in persons with open-angle glaucoma.

METHODS

The visual field data obtained by Goldmann perimetry from 151 persons with open-angle glaucoma from the Baltimore Eye Survey were graded on a nine-level severity scale. Approximately one half of these persons had previously diagnosed glaucoma and were being treated. Using regression analysis, their scores were compared to other features, including age, vertical cup/disk ratio, treatment status, gender, race, and intraocular pressure. These data were used to estimate the average rate of progressive field loss and blindness in glaucoma.

RESULTS

Among 112 black subjects, the severity of visual field damage was significantly associated with age (P < .02), history of glaucoma treatment (P < .04), and intraocular pressure (P < .0001). Using the relationship between age and damage, we estimated that the rate of deterioration of black glaucoma subjects was two grading levels per decade, which is consistent with previous reports. For 39 white subjects, the inclusion of age improved the model relationship between damage score and other variables. The best estimate of individual damage rate for whites was similar to that in blacks. However, the statistical association of age and damage in whites was less strong than in blacks, possibly because of fewer white subjects in the sample.

CONCLUSIONS

While glaucoma is a frequent cause of visual disability, rate of progressive visual field loss is not sufficient to lead to bilateral blindness in the majority of those affected. Aggressiveness of glaucoma therapy should be related to the rate of visual field loss stressing confirmation of field progression.

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

BACKGROUND

Until recently, there has been a paucity of quantitative evidence for intraocular pressure (IOP)-dependent optic disc cupping change in adult glaucoma patients. Therefore, we investigated the relationship between optic disc cupping change and IOP control.

METHODS

The study involved 78 eyes of 78 randomly selected adult patients with early to moderate chronic open-angle glaucoma (CO-AG), treated on various therapeutic regimens, who had had two consecutive successful optic disc analyses with the Rodenstock Optic Nerve Head Analyzer 15.8 +/- 14.8 weeks apart.

RESULTS

The mean initial IOP of 27 eyes (34%) with cupping reversal did not differ from that of 17 eyes (22%) demonstrating progressive deterioration (29.2 +/- 8.8 vs 26.2 +/- 6.1 mmHg, P > 0.5), but the reversal group did have a significantly greater mean IOP decrease than the progression group (-10.8 +/- 7.9 vs-1.0 +/- 7.7 mmHg, P < 0.001) and significantly lower mean final IOP (18.3 +/- 6.1 vs 25.2 +/- 7.9 mmHg, P < 0.003).

CONCLUSION

A decrease of optic disc cupping is more likely with a greater IOP reduction and a lower final IOP, and an increase of cupping is more likely with less or no IOP reduction and a higher final IOP.

Delayed functional loss in glaucoma. LII Edward Jackson Memorial Lecture

PURPOSE

This study is a systematic exploration of why some patients with glaucoma continue to lose visual field long after therapeutic normalization of their increased intraocular pressures.

METHODS

Three cases of glaucoma are described that had increased intraocular pressures and good initial visual fields.

RESULTS

The following four hypotheses are offered to explain delayed functional loss in these patients: (1) A process independent of intraocular pressure is killing ganglion cells. (2) Unmeasured increases of pressure are killing ganglion cells. (3) The ganglion cells have a genetically determined hypersensitivity to intraocular pressure. (4) The ganglion cells have been rendered hypersensitive to intraocular pressure by irreversible damaging effects of previously increased intraocular pressures

CONCLUSION

The current state of knowledge does not permit the elimination of any of the four hypotheses. An additional hypothesis is that the final stage of ganglion cell death is mediated by apoptosis. If so, a potential new treatment for glaucoma would be to inhibit the apoptotic pathway.

Surgery for normal tension glaucoma

The long term follow up of surgery in normal tension glaucoma is presented. One eye of 18 patients with bilateral progressive disease underwent fistulising surgery. Over follow up periods ranging from 2 to 7 years (50% > or = 5 years) the operated eye showed on average a 30% reduction in intraocular pressure (IOP). This was associated with a marked difference in the rate and number of retinal locations showing a progressive decline in retinal function, suggesting some protective function for lowering IOP in patients with normal tension glaucoma.

The primary treatment trial: changes in the visual field analysis by computer-assisted perimetry

Computer-assisted perimetry was performed 6-monthly on patients entered into the Primary Treatment Trial using the 30-2 program. Those patients with a minimum of five visual fields had pointwise linear regression analysis (Progressor) carried out. Two consecutive slopes significant at the 0.05 level were taken as evidence for change, either improvement or worsening. Forty-eight patients in the surgery group, 40 in the medical group and 20 in the laser group were suitable for analysis. A comparison of the eyes showing 'improvement' or 'worsening' in the surgery and medicine groups showed no difference between them. This lack occurred despite a significant difference in intraocular pressure between the two groups. The reasons for this lack of difference are discussed.

The rate of visual field loss in untreated primary open angle glaucoma

The mean rate of visual field loss in untreated primary open angle glaucoma was estimated by comparing the mean age at presentation of patients with early relative visual field loss with the mean age of those who presented with absolute field loss within five degrees of fixation. Analysis of the records of 177 patients indicated that the rate of field loss was related to the level of untreated intraocular pressure. For pressures of 21 to 25 mm Hg, untreated disease is likely to progress from early field changes to end stage in an average of 14.4 years. The same interval for pressures of 25 to 30 mm Hg was 6.5 years and for pressures over 30 mm Hg, 2.9 years. For untreated disease at pressures over 25 mm Hg the interval is estimated at 3.6 years and this is much shorter than the estimated period of 10 years under imperfect treatment and 38 years under optimum treatment identified in a prospective clinical trial of early trabeculectomy in patients with similar intraocular pressures at diagnosis.

Eye care by primary care physicians. A survey of internists and family practitioners in the Sacramento, California, area

To assess the status of eye care as provided by primary care physicians, 193 internists or family practitioners were asked to complete a survey that focused on screening methods and referral patterns. In screening adult patients for glaucoma, 14% of 74 respondents await visual complaints before evaluation and/or referral. Eighteen percent of respondents first refer type II diabetic patients only after personally noting typical funduscopic changes in the undilated fundus. Other ophthalmic care issues are addressed. Results of the survey suggest that greater effort in ophthalmic education of primary care physicians could result in improved ophthalmic care.

Intraocular pressure and the rate of visual field loss in chronic open-angle glaucoma

We measured the rate of change of visual field threshold values over time (mean follow-up, 44.9 +/- 17.4 months) by trend analysis in 40 eyes of 40 patients with chronic open-angle glaucoma. Twenty-eight eyes had stable visual fields, and two eyes had significant visual field improvement. Ten eyes had significant visual field deterioration and showed a correlation between indices of intraocular pressure (standard error of the mean, P = .02; standard deviation, P = .04; and range, P = .05) and the rate of visual field loss in the superonasal region of the visual field, such that the greater the variation of intraocular pressure the greater the rate of loss. The group losing visual fields had a higher mean visual field threshold value and significantly less optic disk pallor and cupping at the start of the study than the stable visual field group. Thus, a significant rate of visual field loss occurred at an earlier stage of the disease and showed a correlation with intraocular pressure in this stage.

Some observations on the relation between intraocular pressure reduction and the progression of glaucomatous visual loss

A quantitative measure of visual field loss associated with kinetic perimetry in chronic open-angle glaucoma (COAG) is discussed. With this new technique an analysis of covariance is applied to a retrospective study of 41 COAG patients. It suggests that reduction of intraocular pressure may not be uniformly effective in controlling the progression of the disease.

A study of the value of the central and peripheral isoptres in assessing visual field progression in the presence of paracentral scotoma measurements

The visual field records of 45 eyes of 45 patients were evaluated to determine whether examination of the peripheral field of vision in patients with glaucoma and field defects adds useful information about the progression of visual field damage. The central scotoma mass, foveal sensitivity, and the central and peripheral mass of the visual field were quantified from measurements on the Tübinger perimeter. Most of the information on visual field progression was contained in the scotoma mass. When both scotoma mass and foveal sensitivity were known, central or peripheral isoptres did not add statistically significant information on progression. Evaluation of scotomas and assessment of central isoptres or of foveal sensitivity made perimetry of the peripheral isoptres redundant. The appearance of fresh peripheral scotomas or the quantification of changes in peripheral scotomas was not examined in the current study, and they would of course be important when they occurred.