Difference of optic disc topography between a low-tension group and a high-tension group in normal-tension glaucoma patients

PURPOSE: Glaucomatous visual field loss and optic disc damage differ by intraocular pressure (IOP) levels. In this study, we compared the optic disc topography in the high-tension group and the low-tension group in normal-tension glaucoma (NTG). METHOD: We selected NTG patients with mean deviation (MD) > or = -10.00 dB and the highest recorded IOP of < 14 mmHg or > or = 17 mmHg without glaucoma treatment. We classified NTG eyes into the following two groups: 1) a low-tension group with the highest recorded IOP of < 14 mmHg, 2) a high-tension group with the highest recorded IOP of > or = 17 mmHg. The optic disc parameters in the low-tension group eyes were compared with those in the high-tension group eyes using a Heidelberg Retina Tomograph. RESULTS: Nineteen eyes of nineteen patients were selected for each group. The cup/disc area ratio in the global sector, and the rim volume in the nasal sector of the low-tension group had deteriorated more than in the high-tension group. CONCLUSIONS: The disc topography is different between the low-tension group and the high-tension group in the nasal sector, suggesting that different pathogenetic mechanisms exist in the optic disc damage in NTG.     

Comparison of visual field defects in the low-tension glaucomas with those in the high-tension glaucomas

We compared the visual fields of 79 eyes (48 patients) with low-tension glaucoma (intraocular pressure less than 21 mm Hg) to the visual fields of 106 eyes (74 patients) with high-tension glaucoma (intraocular pressure greater than 30 mm Hg). Both groups had similar amounts of total field loss as determined by computerized threshold perimetry. Scotomas in the low-tension group had a steeper slope (P less than .001), were significantly closer to fixation (P less than .001), and had greater depth (P less than .001) than those in the high-tension group. These findings suggested that more than one causative factor is important in the production of optic nerve damage in glaucoma.     

Visual field change in low-tension glaucoma over a five-year follow-up

There is some evidence that the nature and progression of disease in low-tension glaucoma may be distinct from other open-angle glaucomas. The authors assessed visual field change by retrospective case review of all patients treated for low-tension glaucoma by the Glaucoma Service, Wills Eye Hospital, for at least 5 years. Sixty-two glaucomatous eyes of 36 patients were identified. All eyes were treated medically and 40 (65%) underwent at least one surgical procedure. Twenty-eight eyes (47%) had initial field loss confined to a single hemi-field and in the remainder both hemi-fields were involved. Thirty of 57 eyes (53%) showed progression at 3 years and 38 (62%) of 57 had progressed by 5 years. A dense scotoma extending from the nasal periphery toward fixation was the most common visual field defect. The rate of field change in this population is significantly greater than in a cohort of primary open-angle glaucoma patients also seen at Wills Eye Hospital, but who had elevated intraocular pressures. Patterns of field loss and rate of progression in this low-tension glaucoma population suggest that the natural history of low-tension glaucoma differs from high-tension open-angle glaucoma.     

Comparative study of retinal nerve fiber layer damage in Japanese patients with normal- and high-tension glaucoma

PURPOSE: To look for possible differences in the pattern of retinal nerve fiber layer (RNFL) damage induced by normal- and high-tension glaucoma. METHODS: The study included randomly selected eyes from 27 patients with open-angle, high-tension glaucoma (mean age, 54.7 +/- 15.0 years; range 21-74 years) and from 19 age-matched patients with normal-tension glaucoma (mean age, 55.7 +/- 11.9 years; range 35-83 years). Eyes were examined using scanning laser polarimetry. RESULTS: The ratio between the superior and inferior quadrant thickness, or symmetry, was significantly lower in patients with high-tension glaucoma (1.00 +/- 0.22) than in patients with normal-tension glaucoma (1.18 +/- 0.32). Similarly, the ratio of the superior to the nasal quadrant thickness was significantly lower in patients with high-tension glaucoma (1.56 +/- 0.38) than in patients with normal-tension glaucoma (1.80 +/- 0.29). No statistically significant differences in the other parameters were detected between the two groups. CONCLUSION: These results show that the pattern of RNFL change is different in patients with high- and low-tension glaucoma. The thickness of the RNFL is reduced symmetrically in the superior and inferior quadrants in high-tension glaucoma, whereas a more localized defect on the inferior RNFL occurs in normal-tension glaucoma.     

Investigations into a vascular etiology for low-tension glaucoma

Increased intraocular pressure is accepted as a primary etiologic factor for the atrophy of the optic nerve head and visual field defects of high-tension glaucoma. Other factors must be present to explain these findings in low-tension glaucoma. One of the current theories is that low-tension glaucoma is the result of decreased optic nerve perfusion on the basis of vascular disease or other factors such as altered blood viscosity. This study compared the non-invasive vascular profiles, coagulation tests, and rheological profiles of 46 consecutive cases of low-tension glaucoma with 69 similarly unselected cases of high-tension glaucoma and 47 age-matched controls. Despite the multifactorial approach and the use of previously validated objective tests, no significant group differences were detected with any of the above investigations. If vascular disease is important in the etiology of low-tension glaucoma, then it must be localized or vasospastic since this study does not support the concept of a generalized vascular etiology, either of an atheromatous or hyperviscous nature, for the genesis of low-tension glaucoma.     

Biostatistical evidence for two distinct chronic open angle glaucoma populations.

Twenty-six eyes of 26 patients with low-tension glaucoma and 34 eyes of 34 patients with high-tension glaucoma were studied. Fifty-one measurements were available on each patient, including visual field indices, finger blood flow measurements, as well as haematological, coagulation, and biochemical and rheological variables. Multivariate analysis revealed two statistically distinct groups of patients, with low and high tension glaucoma cases equally distributed in both. The smaller group (15 patients) showed a suggestion of vasospastic finger blood flow measurements, and had a high positive correlation between the mean deviation (MD) index of field severity and the highest intraocular pressure (r = 0.715, p = 0.0008). The second, larger group (45 patients) showed disturbed coagulation and biochemical measurements, suggestive of vascular disease, and had no correlation between the MD index and the highest intraocular pressure.     

Diffuse visual field loss in chronic open-angle and low-tension glaucoma

We examined 37 eyes of 37 patients with chronic open-angle glaucoma and 24 eyes of 24 patients with low-tension glaucoma. All patients had a scotoma confined to the upper or lower hemifield. Eyes with open-angle glaucoma showed twice as much loss of sensitivity in the spared hemifield as compared to eyes with low-tension glaucoma. These differences were statistically significant.     

Sectorization of central 10-deg visual field in open-angle glaucoma

Purpose: To obtain an optimal clustering of the test points of the Humphrey 10-2 program in glaucoma for brief evaluation of the visual field characteristics in the central 10-deg field and to examine its clinical usefulness. Methods: We applied VARCLUS, a new clustering algorithm, to 379 visual fields obtained with the 10-2 program of the Humphey perimeter from 211 eyes of 140 normal-tension glaucoma (NTG) patients and 168 eyes of 111 primary open-angle glaucoma (POAG) patients with the mean deviation (Statpac 2) –15 dB. Based on the interpoint correlation of deviation of the measured threshold value from age-corrected normal reference (total deviation), the 68 2-deg grid points were mathematically clustered, i.e., the central 10-deg visual field was divided into sectors. Between 76 eyes of 76 POAG patients with the peak intraocular pressure (IOP) 25 mmHg (high-tension group) and 85 eyes of 85 NTG patients with the peak IOP 18 mmHg (low-tension group) which had similar mean deviation and age, the mean of total deviation in each obtained sector was compared. Results: The central 10-deg visual field in glaucoma was divided into 10 sectors. The sector pattern obtained was compatible with the projection of nerve fiber layers, with no sectors extending over the horizontal meridian, and it was not completely symmetrical around the horizontal meridian. A group of sectors in the superior arcuate area was significantly more depressed in the low-tension group, while a group of sectors in the inferior centrocecal area was significantly more depressed in the high-tension group. Conclusion: We suggest that the sector pattern obtained here is useful to provide brief evaluation of the result of the 10-2 program and that it may be used in the study of the central visual field in glaucoma.     

Oxygen saturation levels in the juxta-papillary retina in eyes with glaucoma

Oxygen saturation (OS) levels in the juxta-papillary retina particularly inferotemporal retina were investigated in open-angle glaucoma (OAG) patients as well as normal subjects. Fifty-six eyes of 56 OAG Japanese patients and 20 eyes of 20 age-matched normal subjects were recruited for the study. OAG eyes (56) were subdivided into two groups: 15 eyes of low-tension (LT) subgroup and 41 eyes of high-tension (HT) subgroup. The average of age of the LT, HT subgroup and normal group were 60.5, 55.9 and 52.6 years, respectively. OS levels in the retina were measured using a Fourier transform-based spectral retinal imaging (SRI) system (Retinal Cube; ASI Co. Migdal Hemak, Israel), with which OS levels in the fundus could be computed at every pixel point of a 35 degrees fundus image. We calculated OS levels at five points in the retina near the optic disc and retinal arteries and veins in all eyes. The OS levels were also compared with the results analyzed using Humphrey visual field Analyzer with the program 30-2 SITA. At the superior and nasal juxta-papillary retinal points, OS level of the LT subgroup showed significant decrease as compared with the HT subgroup and the normal group (p=0.048-0.009). The LT and the HT subgroups were significantly lower than the normal group at the inferotemporal and the average of the retinal points (p=0.047-0.001). There were no statistically significant differences among the three groups in regards to the OS in the retinal artery. There was a statistical significant correlation between the mean of total deviation of the 17 points in the upper arcuate area and OS of the inferotemporal point (p=0.018), and between mean deviation and the average of OS of the inferotemporal and the superotemporal point (p=0.037) in the HT subgroup. However, there was no significant correlation in the LT subgroup. OS levels in the retina were especially decreased in the low-tension glaucoma subtype. There was a correlation between the visual field defect and OS in the HT eyes in the inferotemporal region. OS measurement may be a novel adjunct to study glaucoma patients.     

Glaucoma without ocular hypertension. A clinical study

One hundred eighty-four glaucomatous eyes (125 patients) with visual field defects of Stage I and II in the central visual field were examined with the Octopus perimeter 201, Program 31 or 33, and were divided into 3 groups according to maximum intraocular pressures: (1) low-tension glaucoma (21 mm Hg), (2) glaucoma simplex (22-29 mm Hg), (3) glaucoma simplex (30-39 mm Hg). In these three groups of glaucomatous eyes the cupping of the optic disk, vision and blood pressure were examined and a further check for cardiovascular risk factors was carried out by the internist. All three groups proved to have an equally high incidence of cardiac insufficiency, abnormal EKG changes and diabetes. However, a low systolic blood pressure was found to be the risk factor more often in patients with low-tension glaucoma than with glaucoma simplex. Furthermore, intraocular pressures in the low-tension glaucoma group were higher than those in the normal population. The occurrence of cupping of the optic disk, which is not present with purely vascular optic nerve diseases, and the location of visual field defects in low-tension glaucoma, which is similar to that in glaucoma simplex but different from vascular diseases, as well as the increased diurnal tension variations of diurnal tension curves compared to the normal population are all factors which indicate that low-tension glaucoma is not a purely vascular optic nerve disease, and that pressure-lowering therapy is necessary.(ABSTRACT TRUNCATED AT 250 WORDS)     

小梁切除术后低眼压性浅前房原因探讨与诊治体会

目的:探讨青光眼小梁切除术后浅前房的原因,寻求有效的诊治方法。方法:回顾总结2003-06/2007-06间285例(303眼)抗青光眼小梁切除术及术后发生低眼压性浅前房的原因、程度及诊疗过程。结果:本组发生术后低眼压性浅前房58例89眼(29.4%)。其中,结膜切口漏6眼(6.7%),滤过过强46眼(51.6%)脉络膜、睫状体脱离37眼(41.6%。)结论:抗青光眼小梁切除术后低眼压性浅前房原因复杂,其中,除滤过过强外,脉络膜、睫状体脱离是很重要的一个原因。     

Correlation between intraocular pressure level and optic disc changes in high-tension glaucoma suspects

PURPOSE: To assess the correlation between intraocular pressure (IOP) and future optic disc changes in eyes of patients suspected of having high-tension glaucoma and to determine the target pressure in eyes of patients suspected of having high-tension glaucoma. DESIGN: Prospective, comparative, observational case series. PARTICIPANTS: Fifty-seven eyes of 57 patients suspected of having high-tension glaucoma selected from 226 consecutive patients with glaucoma or suspected glaucoma. INTERVENTION: The status of the optic disc and visual fields was evaluated during an initial examination by confocal laser ophthalmoscopy and automatic perimetry, respectively. Fifty-seven eyes were followed up for at least 2.5 years and then underwent a final examination. IOP was measured every 3 months. MAIN OUTCOME MEASURES: The correlation between changes in optic disc status and IOP control during follow-up was determined. Changes in the optic disc were evaluated by using the percentage change in total contour area, neuroretinal rim area, and cup-to-disc ratio. The control IOPs were evaluated on the basis of the percentage of time during which IOP was <18 mmHg (%<18 mmHg control) and <21 mmHg (%<21 mmHg control) during follow-up in each eye. The correlation between visual field changes and IOP control was also analyzed. RESULTS: Results from 48 (84.2%) of 57 participants were included. Patients were followed up for a mean 4.4 years. The %<21 mmHg control was significantly correlated with changes in neuroretinal rim area (r = 0.40; P = 0.0055) and in cup-to-disc ratio (r = -0.40; P = 0.0051) by linear regression analysis. The correlations were also significant if the difference in the length of follow-up was adjusted by multivariate regression analysis. There was no significant correlation between %<18 mmHg control and changes in disc parameters. Seven (14.6%) of 48 eyes had glaucomatous visual field defects at the final examination. The %<21 mmHg control was significantly lower in eyes with visual field changes compared with eyes with no changes (P = 0.0153; unpaired t test). In contrast, %<18 mmHg control was not significantly different between eyes with and without visual field changes (P = 0.3886). CONCLUSIONS: The IOP level correlates with topographic changes in the optic disc in eyes of patients suspected of having high-tension glaucoma. The target pressure for such eyes may need to be between 18 and 21 mmHg, and <18 mmHg is a safe target level in the treatment of patients suspected of having high-tension glaucoma to delay topographic optic disc changes.     

Central corneal thickness in low-tension glaucoma

BACKGROUND: It is possible that the intraocular pressure (IOP) is underestimated in eyes whose central cornea is thinner than normal. The objective of this study was to determine and establish the significance of central corneal thickness in patients with low-tension (normal-tension) glaucoma compared with those with chronic open-angle glaucoma (COAG) or ocular hypertension and healthy eyes. METHODS: The study was carried out from February 1998 to May 1999. Central corneal thickness was measured by ultrasonic pachymetry and IOP was measured by Goldmann applanation tonometry in 25 patients with low-tension glaucoma (untreated IOP less than 21 mm Hg with evidence of optic nerve head damage and corresponding visual field loss on automated perimetry), 80 patients with COAG (untreated IOP 21 mm Hg or greater with evidence of optic nerve head damage and corresponding visual field loss on automated perimetry), 16 patients with ocular hypertension (untreated IOP 21 mm Hg or greater, with normal optic nerve head and no history of glaucoma or elevated IOP, and normal visual field on automated perimetry) and 50 control subjects (untreated IOP less than 21 mm Hg with normal optic nerve head and no history of glaucoma or elevated IOP). Analysis with Pearson's product-moment correlation was performed to determine the correlation of IOP and central corneal thickness, and one-way analysis of variance was used to compare corneal thickness between groups. RESULTS: The central cornea was significantly thinner in the low-tension glaucoma group (mean 513.2 mu [standard deviation (SD) 26.1 mu]) than in the COAG group (mean 548.2 mu [SD 35.0 mu]) and the control group (mean 556.7 mu [SD 35.9 mu]) (p < 0.001). No significant difference in corneal thickness was found between the COAG and control groups. The ocular hypertension group had significantly thicker corneas (mean 597.5 mu [SD 23.6 mu]) than the three other groups (p < 0.001). INTERPRETATION: Patients with low-tension glaucoma may have thinner corneas than patients with COAG and healthy subjects. This results in underestimation of their IOP. Corneal thickness should be taken into account when managing these patients to avoid undertreatment.     

Glaucomatous damage in normotensive fellow eyes of patients with unilateral hypertensive pseudoexfoliation glaucoma: normotensive pseudoexfoliation glaucoma?

BACKGROUND: The objective of the study was to investigate the prevalence of glaucomatous damage in normotensive fellow eyes of patients with unilateral high-tension pseudoexfoliation (PX) glaucoma. METHODS: Initial examination records of 111 patients with unilateral PX glaucoma with intraocular pressure (IOP) > or = 22 mmHg in the hypertensive eye and IOP < or = 21 mmHg in the normotensive fellow eye without any prior antiglaucomatous treatment were retrospectively studied. Visual field and optic disc examination results were evaluated for glaucomatous damage in the normotensive eyes. RESULTS: Glaucomatous changes were detected in 45 of the 111 fellow eyes (40%). The damage was mild in 25 eyes (22%), moderate in 18 eyes (16%), and severe in 2 (2%). The factors significantly associated with glaucomatous findings in the normotensive eyes were clinical detection of PX, higher age (> or =70 years), higher maximal IOP (> or =18 mmHg) and wider IOP fluctuation (> or =6 mmHg) in the univariate analyses. In the multivariate analysis, associated factors remained as higher maximal IOP (odds ratio = 7.92, confidence interval = 2.82-22.23, P < 0.001) and wider IOP fluctuation (odds ratio = 5.67, confidence interval = 2.05-15.74, P = 0.001). CONCLUSION: Normotensive fellow eyes of patients with unilateral high-tension PX glaucoma are under significant risk of glaucomatous damage, related with the level and the fluctuation range of IOP.     

Systemic factors in patients with low-tension glaucoma.

Nineteen patients (38 eyes) with low-tension glaucoma were compared with 53 subjects (106 eyes) with ocular hypertension. Comparable for age and sex, the 2 groups were assessed with respect to haematological and biochemical criteria, physical activity, and medical history. Statistical analyses of the differences between the 2 groups highlighted the importance of diastolic ophthalmodynamometry levels, prediagnosis exercise habits, cardiovascular disease status, and possibly systolic blood pressure. Patients with low-tension glaucoma suffered a higher prevalence of multiple abnormalities of these systemic factors than did their ocular hypertensive counterparts. There were no significant differences between the 2 groups with respect to the many other factors examined.     

Optic disc hemorrhage in low-tension glaucoma

The prevalence of optic disc hemorrhage (DH) was determined in groups consisting of 192 primary open-angle glaucoma, 113 primary angle-closure glaucoma, 78 low-tension glaucoma, and 473 normal patients. The DH was mot prevalent (20.5%) among low tension glaucoma patients (chi 2; P less than 0.001). The epidemiological features of DH were studied in 58 low-tension glaucoma patients by examining them every one to four weeks from 6 to 32 months. All the DHs but one took place within a seven-month follow-up and the incidence of DH varies from 0 to 10% during the 32-month follow-up period. The overall incidence of DH was 24.8% during that period of time. Recurrences were seen in 64% of the eyes and 92% of these occurred within 28 weeks following the previous hemorrhages. Ninety-two percent of all DHs were present for at least four weeks. Low-tension glaucoma eyes seem to consist of two different groups; one which develops recurrent DH and one which is very unlikely to bleed through its entire course.     

Surgical treatment of low pressure glaucoma]

Eyes with non-controlled--in spite of a conservative treatment--bilateral low-tension glaucoma with a decreased facility of outflow (10 patients, 20 eyes) were subjected to antiglaucoma operations. Trabeculectomy was performed in one eye, a filtering operation in the second one. During the observation period of 1.5 years it showed that in the low-tension glaucoma the visual function undergoes more frequently stabilization after a more radical glaucomatous procedure (of filtration type) when the postoperative fall in the intraocular pressure exceeds 20% and its daily oscillations are considerably reduced.     

Pattern of visual field defects in normal-tension and high-tension glaucoma

There are probably two major types of causative factors in open-angle glaucoma: pressure-dependent and pressure-independent. If clinical features such as the pattern of visual field defects differ between normal-tension and high-tension glaucoma, the differences may provide an insight for discriminating between the pressure-dependent and the pressure-independent damage in open-angle glaucoma. This article gives a brief review of the most recent studies including reports wherein progression or pattern of visual field defects in normal-tension and high-tension glaucoma or primary open-angle glaucoma are addressed. Further deterioration of the visual field in 5 years is expected in about 50% of eyes with normal-tension glaucoma in which intraocular pressure is one of the contributing factors. This figure may be greater than that seen in eyes with primary open-angle glaucoma where intraocular pressure is controlled with surgery in the middle teens. When eyes with normal-tension glaucoma and high-tension glaucoma or primary open-angle glaucoma were matched for extent of overall visual field loss, many studies noted a difference in the pattern of visual field defects between the two groups. Visual field defects in normal-tension glaucoma are relatively more localized and closer to fixation, especially in the nasal superior quadrant and may be more predominant in the lower hemifield. Results of other psychophysical tests also appear to support the above findings.     

Unequal intraocular pressure and its relation to asymmetric visual field defects in low-tension glaucoma

Fifty-nine low-tension glaucoma patients were reviewed with respect to asymmetry of intraocular pressure (IOP) and visual field defects. In the presence of unequal IOP the visual field damage is almost always greater on the side with higher mean IOP. However, only 13 of 47 patients with asymmetric visual field defects had a mean IOP difference between the two eyes of greater than or equal to 1 mmHg. Although in the case of IOP asymmetry visual field damage is greater in the eye with higher mean IOP, other factors must also play an important role in the development of visual field defects in low-tension glaucoma.     

Optic disk and visual field correlations in primary open-angle and low-tension glaucoma

If the amount of visual field loss is less than expected from the amount of optic disk cupping in low-tension glaucoma compared with primary open-angle glaucoma, it might imply a difference between the two conditions in the type of optic nerve lesion produced. To test this hypothesis, three observers independently examined, in a masked fashion, optic disk stereoscopic photographs of 127 eyes with primary open-angle glaucoma and 71 eyes with low-tension glaucoma. For each stereoscopic photograph the observer predicted whether the visual field loss would be mild, moderate, or severe. The visual field were then classified, according to the number of sectors defective on the Goldmann perimeter chart, as having mild (1 to 15 sectors), moderate (16 to 30 sectors), or severe (more than 30 sectors) visual field loss. For no observer did the frequency of underpredictions or overpredictions in the two conditions differ significantly. The results of this study, thus, did not support the theory that the optic disk damage in primary open-angle glaucoma differs from that in low-tension glaucoma.