Effects of acutely lowering intraocular pressure on the results of multifocal visual evoked potential testing

Improvement in structure and visual function in patients with glaucoma: the possible key to better treatment?

Glaucoma is characterized by retinal ganglion cell loss that can lead to permanent visual loss. Current clinical management practice assumes that glaucomatous visual loss is irreversible; however, there is increasing evidence that permanent vision loss and cell death are preceded by reversible functional and structural changes. We propose that these changes should be considered by glaucoma specialists when treating their patients. We discuss the neurobiological basis of this phenomenon and provide clinical evidence of reversibility in both structure and function. Specifically, we review the findings of visual field testing, contrast sensitivity, electroretinography, and imaging of the optic nerve and their correlation with functional changes. We then discuss the clinical value of these observations in helping guide approaches toward the diagnosis and treatment of patients with glaucoma.

Lack of Visual Field Improvement After Initiation of Intraocular Pressure Reducing Treatment in the Early Manifest Glaucoma Trial

Purpose

We evaluate how visual fields are affected by the initiation of IOP-reducing therapy in previously untreated glaucoma individuals.

Methods

Qualifying individuals with newly diagnosed glaucoma having normal to moderately elevated IOP were prospectively randomized either to IOP-reducing therapy or to no treatment. Before randomization, individuals underwent repeatedly Standard Automated Perimetry (SAP) testing and Goldmann tonometry. Three months after randomization, patients again underwent SAP and tonometry. Changes between baseline and the 3-month follow-up visit in the perimetric summary index, mean deviation (MD), and total deviation values at significantly depressed test points were compared between the treated and untreated groups.

Results

Of 255 individuals studied, 129 were randomized to treatment and 126 to no treatment. Intraocular pressure decreased by an average of 24% among treated and by 0.6% in the untreated patients. Mean deviation deteriorated slightly in both groups; mean change was −0.15 and −0.44 dB in the treated and untreated groups, respectively; the difference was not statistically significant, (P = 0.16). No association was seen between IOP reduction and change in MD. Sensitivities decreased slightly in significantly depressed test points, mean change was −0.45 dB in the untreated and −0.38 dB in the treated groups (P = 0.88).

Conclusions

Observed visual field changes among glaucoma patients receiving initial IOP-reducing therapy were not significantly different to changes seen in patients who received no treatment. Thus, our results did not support the idea that visual field status improves after initiation of IOP- reducing therapy in glaucoma individuals, at least not in individuals with initially normal to moderately elevated IOPs.

Optic nerve head morphology in young patients after antiglaucomatous filtering surgery

PURPOSE

To compare the optic nerve head appearance in glaucomatous eyes before and after marked reduction of intraocular pressure (IOP).

METHODS

The hospital-based observational case-series study included selected glaucoma patients for whom optic disc photographs taken before and 1 week to 5 months after surgical reduction of IOP were morphometrically examined.

RESULTS

The study included 23 eyes of 16 patients (mean age: 28.7 ± 6.0 years). Mean preoperative IOP was 31.6 ± 7.7 mmHg (22-52 mmHg), and mean IOP drop was 21.5 ± 8.4 mmHg (11-45 mmHg). The horizontal disc diameter decreased significantly (p < 0.001) after surgery, while the vertical disc diameter did not change markedly (p = 0.54). The width of the neuroretinal rim increased significantly in all disc quadrants (all p-values ≤ 0.01), optic cup depth decreased (p < 0.001), and reflectivity of the inner retinal surface increased significantly (p < 0.001). Some eyes showed a pronounced reduction in beta zone of parapapillary atrophy parallel to an increase in horizontal disc diameter, and some eyes showed an enlargement of beta zone parallel to a reduction in horizontal disc diameter.

CONCLUSIONS

After marked reduction of high IOP, some eyes of young adult patients with glaucoma can show a horizontal shrinkage of the optic nerve head, in addition to a partial restoration of the neuroretinal rim and a flattening of the optic cup. In addition, beta zone of parapapillary atrophy can decrease or increase, complementarily to changes in the horizontal disc diameter. These findings may be of interest for the biomechanics of the optic nerve head and the precision of imaging techniques.

Topographic optic disc changes after successful trabeculectomy evaluated using spectral domain optical coherence tomography

PURPOSE

To investigate topographic optic disc changes after surgical intraocular pressure (IOP) reduction in adults with open angle glaucoma (OAG).

METHODS

Optic discs of patients with advanced primary open angle or exfoliation glaucoma were imaged using optical coherence tomography within 1 week before trabeculectomy. Patients were rescanned 1 week, 1 month, and 1 year after surgery. Maximum cup depth (MCD), and average cup depth (ACD) were calculated.

RESULTS

Twenty-two eyes from 20 patients (age, 70.5 ± 10.6 years; average mean defect of visual field, -15.0 ± 9.8 dB) were followed up for 1 year. The IOP decreased from 22.1 ± 2.8 mmHg at baseline to 11.5±2.6 mmHg 1 year following surgery (P<0.001). One-week and 1-month postoperative IOPs were 11.2 ± 2.8 and 11.2 ± 3.5 mmHg, respectively (P<0.001). Compared to the baseline values (356 ± 172 μm), postoperative ACD showed a significant decrease at 1 week (312 ± 164 μm; P<0.001) and 1 month (338 ± 175 μm; P=0.007) after surgery, but not at 1 year (339 ± 176 μm; P=0.354). Similarly, MCD significantly decreased from baseline (477 ± 190 μm) 1 week (431 ± 203 μm; P=0.029) and 1 month (448 ± 198 μm; P=0.047) after the surgery, but not after 1 year (479 ± 188 μm; P=1.0).

CONCLUSIONS

Trabeculectomy reduces IOP in eyes with advanced OAG, which induces topographic optic disc changes. Such optic disc changes became less pronounced over time and were no longer detectable 1 year after surgery.