The diagnosis of normal-tension glaucoma

Preoperative intraocular pressure as a predictor of selective laser trabeculoplasty efficacy

PURPOSE

To identify predictors of intraocular pressure (IOP) reduction following selective laser trabeculoplasty (SLT) in patients with high- and low-pressure primary open-angle glaucoma, who are already taking maximally tolerated IOP-lowering medication and need further IOP reduction.

METHODS

In this prospective interventional case series, 157 eyes of 157 open-angle glaucoma patients who were assigned for SLT for further IOP reduction were included. Each patient had diurnal IOP measurements taken before and on average 6 months following SLT. The mean of six IOP measurements was compared. The following parameters were analysed for their association with SLT success: age, gender, spherical equivalent, high-pressure or normal-pressure open-angle glaucoma, number and type of pressure-lowering medications, lens status, pre-SLT IOP, IOP at the time of diagnosis, duration of glaucoma, visual field stage and central corneal thickness.

RESULTS

The only parameter that was predictive for absolute and relative mean diurnal IOP reduction after SLT was the preoperative mean diurnal IOP. One hundred per cent of the patients with a mean diurnal preoperative IOP of more than 18 mmHg had an IOP reduction after SLT. With mean diurnal preoperative values of 14-18 mmHg, 83.1% of the patients, and with values below 14 mmHg only 64% of the patients, showed an IOP reduction. This difference was statistically significant (>18 compared to 14-18: p = 0.002; >18 compared to <14: p = 0.001; 14-18 compared to <14: p = 0.030).

CONCLUSIONS

The pressure-lowering effect of SLT can best be predicted by the individual IOP level before treatment. Patients with mean diurnal IOP levels below 14 mmHg might not benefit from the procedure at all.

Selective laser trabeculoplasty reduces mean IOP and IOP variation in normal tension glaucoma patients

Purpose:

To evaluate the effect of selective laser trabeculoplasty (SLT) in normal tension glaucoma (NTG) patients.

Patients and methods:

A retrospective review was performed of NTG patients who had undergone SLT at the Duke University Eye Center between 12/2002 and 7/2005. For each eye of each patient at pre-laser and post-laser time points, the IOP measurements were summarized by mean, standard deviation, and range. Then for each of these descriptive statistics, the differences between pre-laser and post-laser values were obtained. Statistical analysis was performed using a random effects model. Main outcome measures: difference in mean IOP, standard deviation of IOP, and range of IOP.

Results:

Thirty-one eyes of 18 patients were included for analysis. The average of the mean pre-operative IOP measurements was 14.3 ± 2.6 mmHg compared to 12.2 ± 1.7 mmHg (P < 0.001) post-operatively. The mean pre-operative standard deviation was 1.9 ± 0.9 mmHg compared to 1.0 ± 0.6 mmHg (P = 0.002) post-operatively while the mean IOP range prior to treatment was 4.5 ± 2.5 mmHg compared to 2.5 ± 1.9 mmHg (P = 0.017) after treatment.

Conclusion:

In this pilot study, SLT was found to lower mean IOP and intervisit IOP variation in NTG patients. Given the importance of IOP variation and its association with glaucoma progression, measurement of IOP variation following treatment with SLT may be considered.

Neuroradiologic screening in normal-pressure glaucoma: study results and literature review

PURPOSE

To determine if there was an increased prevalence of intracranial compressive lesions in patients with clinically diagnosed normal-pressure glaucoma compared with a group of patients with progressive primary open-angle glaucoma.

PATIENTS AND METHODS

In a prospective, comparative, observational case series, the authors performed cranial magnetic resonance imaging in patients with consecutively diagnosed normal-pressure glaucoma (n = 62) and progressive primary open-angle glaucoma with controlled intraocular pressures (n = 70). The prevalence of intracranial compressive lesions, demographic data, and clinical characteristics were compared between both groups.

RESULTS

Four of the 62 (6.5%) patients with normal-pressure glaucoma had clinically relevant intracranial compressive lesions involving the anterior visual pathway, compared with none of the 70 patients with primary open-angle glaucoma (P = 0.039).

CONCLUSIONS

Intracranial compressive lesions are an important diagnostic consideration in the workup of normal-pressure glaucoma.