Changes in visual function after intraocular pressure reduction using antiglaucoma medications

Short-Term Changes in the Photopic Negative Response Following Intraocular Pressure Lowering in Glaucoma

Purpose

To evaluate the short-term changes in inner retinal function using the photopic negative response (PhNR) after intraocular pressure (IOP) reduction in glaucoma.

Methods

Forty-seven participants with glaucoma who were commencing a new or additional IOP-lowering therapy (treatment group) and 39 participants with stable glaucoma (control group) were recruited. IOP, visual field, retinal nerve fiber layer thickness, and electroretinograms (ERGs) were recorded at baseline and at a follow-up visit (3 ± 2 months). An optimized protocol developed for a portable ERG device was used to record the PhNR. The PhNR saturated amplitude (V_max), V_max ratio, semi-saturation constant (K), and slope of the Naka–Rushton function were analyzed.

Results

A significant percentage reduction in IOP was observed in the treatment group (28 ± 3%) compared to the control group (2 ± 3%; P < 0.0001). For PhNR V_max, there was no significant interaction (F_1,83 = 2.099, P = 0.15), but there was a significant difference between the two time points (F_1,83 = 5.689, P = 0.019). Post hoc analysis showed a significant difference between baseline and 3 months in the treatment group (mean difference, 1.23 µV; 95% confidence interval [CI], 0.24–2.22) but not in the control group (0.30 µV; 95% CI, 0.78–1.38). K and slope were not significantly different in either group. Improvement beyond test–retest variability was seen in 17% of participants in the treatment group compared to 3% in the control group (P = 0.007, χ² test).

Conclusions

The optimized protocol for measuring the PhNR detected short-term improvements in a proportion of participants following IOP reduction, although the majority showed no change.

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.

Evidence on the neuroprotective properties of brimonidine in glaucoma

BACKGROUND

glaucoma is the leading cause of irreversible blindness all over the world. The degree of visual field loss accounts for the severity of the disease and represents the main clinical outcome of treatment for patients affected by glaucoma. The α2 agonists, like brimonidine, emerged in the 1960s as topical ophthalmologic treatment. Their neuroprotective mechanism in glaucoma is still debated, ranging from effect on extracellular glutamate, to ocular hypotension and blood flow.

OBJECTIVES

this systematic review and meta-analysis aims at assessing the efficacy of brimonidine on visual field deterioration during glaucoma through the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) approach. Databases consulted: the literature search has been performed on PubMed, MEDLINE, ClinicalTrials.gov and Scopus up to June 10th, 2020. Study eligibility criteria, participants, and interventions: clinical trials assessing the effects of brimonidine on visual field in patients with glaucoma. Study appraisal: the eligibility of the studies has been assessed by two independent authors and the selection has followed the PRISMA flow diagram. The retrieved results have been subjected to risk of bias evaluation.

RESULTS

the search of literature has retrieved 418 papers, among which 5 are eligible for inclusion in the qualitative analysis. All the studies present high heterogeneity, therefore meta-analysis has not been possible. The results obtained suggest that brimonidine improves visual field, but the design of the clinical trials rises some concerns in terms of risk of bias.

CONCLUSIONS

the evidence of neuroprotective effect of brimonidine is inconclusive and needs stronger support. Large double-blind randomized clinical trials are necessary to strengthen this evidence.

Evaluation of Contrast Sensitivity after Four Different Treatment Modalities Using OPTEC-Functional Vision Analyzer in Primary Open-Angle Glaucoma

PURPOSE

The purpose of the study is to evaluate the changes in contrast sensitivity (CS) after using the four different types of antiglaucoma eye drops in patients with primary open-angle glaucoma (POAG) by OPTEC-functional vision analyzer (FVA).

METHODS

In this prospective study, eighty patients (80 eyes) with POAG were randomly divided into four groups. The groups were randomly received timolol maleate 0.5%, travoprost 0.004%, dorzolamide 2%, and brimonidine tartrate 0.2%. The medications were used in the eye that was randomly selected. The CS was assessed before and 15 min after the intervention by the FVA. The paired t-test was used to compare the difference between before and after the intervention. P < 0.05 was considered statistically significant.

RESULTS

Fifteen minutes after the instillation of timolol maleate (Group A), the CS in three out of twenty patients at the spatial frequencies of 1.5, and 3 cycles per degree (cpd) was significantly decreased (P = 0.015). However, using travoprost (Group B) and dorzolamide (Group C), the CS in one out of twenty patients at low spatial frequencies (1.5 and 3 cpd) was decreased in the two groups, which was not statistically significant for these medications (P > 0.05). In Group D, after applying brimonidine tartrate, the CS in two out of twenty patients at the spatial frequency of 18 cpd was significantly decreased (P = 0.042).

CONCLUSION

Our study showed that CS values at low and high spatial frequencies after applying timolol and brimonidine eye drops are temporarily reduced in patients with POAG.

A control experiment for studies that show improved visual sensitivity with intraocular pressure lowering in glaucoma

PURPOSE

Contrast sensitivity sometimes increases in patients with open-angle glaucoma when intraocular pressure (IOP) is decreased. Although often interpreted as demonstrating reversible glaucoma-induced dysfunction, this result, if true, could simply reflect a general relationship between sensitivity and IOP in visual mechanisms unaffected by glaucoma. To investigate this relationship, we test the hypothesis that reducing IOP in eyes without glaucoma (ocular hypertension) does not increase perimetric contrast sensitivity.

DESIGN

Comparative case series.

PARTICIPANTS

A total of 692 participants drawn from the Ocular Hypertension Treatment Study (OHTS) (22 clinical centers).

METHODS

Commercially available topical ocular hypotensive medications.

MAIN OUTCOME MEASURES

Post hoc analysis of IOP and perimetric contrast sensitivity (mean deviation [MD] and pattern standard deviation [PSD]) both at baseline (0 months, immediately before ocular antihypertensive therapy) and at 6-month review. An additional 618 control eyes from OHTS that did not receive treatment were examined over the same period. Data from the second phase of OHTS also were examined, and control eyes then received treatment.

RESULTS

Treated eyes had a decrease in IOP at 6 months (5.1 mmHg, P<0.001) but no significant change in MD (0.04 decibels [dB], P = 0.59) or PSD (0.03 dB, P = 0.19), relative to controls. A similar decrease in IOP was found for eyes that began treatment in the second phase of OHTS, but no significant change in MD or PSD.

CONCLUSIONS

Despite using a large sample size, we found no relationship between perimetric contrast sensitivity and IOP reduction in ocular hypertension, which suggests that previous sensitivity changes seen in patients with glaucoma, if true, are indicative of reversible glaucoma-induced dysfunction rather than a general relationship between sensitivity and IOP in visual mechanisms unaffected by glaucoma.

Glaucoma 2.0: neuroprotection, neuroregeneration, neuroenhancement

Glaucoma is a progressive neurodegenerative disease of retinal ganglion cells (RGCs) associated with characteristic axon degeneration in the optic nerve. Clinically, our only method of slowing glaucomatous loss of vision is to reduce intraocular pressure (IOP), but lowering IOP is only partially effective and does not address the underlying susceptibility of RGCs to degeneration. We review the recent steps forward in our understanding of the pathophysiology of glaucoma and discuss how this understanding has given us a next generation of therapeutic targets by which to maintain RGC survival, protect or rebuild RGC connections in the retina and brain, and enhance RGC function.

Corneal viscoelasticity differences between diabetic and nondiabetic glaucomatous patients

PURPOSE

To investigate corneal viscoelasticity in primary open-angle glaucoma patients with and without diabetes mellitus, and to correlate corneal hysteresis (CH) with central corneal thickness (CCT).

METHODS

In this cross-sectional study, 44 primary open-angle glaucoma patients [19 with diabetes (34 eyes) and 25 without diabetes (40 eyes)] underwent a complete ophthalmic examination. Data collected by masked investigators included CH and CCT using the Ocular Response Analyzer. The mean of 3 measurements was considered for each test. We analyzed the difference between the mean CH in both groups using a general linear model. Partial correlation coefficient between CH and CCT was also calculated.

RESULTS

Mean+/-SD age in diabetic and nondiabetic groups was 67.1+/-8.7 and 65.9+/-15.1, respectively (P=0.77). There was no significant difference regarding mean CCT between diabetic (531.7+/-31.3 mum) and nondiabetic (546.6+/-37.3 mum) groups (P=0.21). Patients with diabetes presented significantly higher CH values than patients without diabetes (9.1+/-1.9 mm Hg vs. 7.8+/-1.7 mm Hg, P=0.04). There was a significant and positive correlation between CH and CCT for all patients (r=0.407, P<0.001).

CONCLUSIONS

Primary open-angle glaucoma patients with diabetes have significantly higher CH values than those without diabetes. CH and CCT results were positively correlated. These findings merit further investigation to assess the role of different CH values on glaucoma evaluation and susceptibility.