Treating ocular hypertension to reduce glaucoma risk: when to treat?

The evaluation of juvenile ocular hypertension by optical coherence tomography angiography

Background

Vessel density (VD) of the elderly ocular hypertension patients measured by optical coherence tomography angiography (OCTA) have been reported. However, the studies of VD in juvenile ocular hypertension (JOHT) are limited. We wished to evaluate VD changes using OCTA in JOHT. We also investigated the potential risk parameters of intraocular pressure (IOP) and vertical cup/disc ratio (CDR) with OCTA for observing the development of JOHT.

Methods

We examined 86 eyes in 45 control (Ctrl) subjects and 65 eyes in 34 patients with JOHT using OCTA at the glaucoma clinic of the Eye, Ear, Nose, and Throat Hospital of Fudan University. The VD of radial peripapillary capillaries (RPC) and the perifoveal superficial vascular plexus (SVP) was compared between the Ctrl and JOHT groups. Other basic study factors such as age, sex, blood pressure, best-corrected visual acuity, central corneal thickness, IOP, CDR, the thickness of the retinal nerve fiber layer, ganglion cell complex, visual field mean deviation, and pattern standard deviation were also recorded.

Results

Bare difference was found in the nasal-inferior and temporal RPC-VD between the Ctrl and JOHT groups (P = 0.042 and P = 0.033, respectively) while SVP-VD was not (all P > 0.05). In the mixed linear regression model analysis, temporal RPC-VD was marginally negatively associated with high IOP (r = − 1.379, P = 0.043). Five additional sections of nasal, inferior-nasal, inferior-temporal, superior-temporal, and superior-nasal RPC-VD showed positive correlation with large CDR (all P <  0.05). SVP-VD in the superior and nasal regions was marginally negatively correlated with high IOP (r = − 1.877, P = 0.023; r = − 1.693, P = 0.049). No other regions were found statistical different of relationship between IOP, CDR and VD.

Conclusions

Nasal-inferior and temporal peripapillary VD was marginally lower in JOHT subjects. Regarding parameters of IOP and CDR, peripapillary temporal VD had a borderline level of negative correlation with IOP more than 21 mmHg while additional five regions were strongly positively correlated with large CDR. Some macular regions only found marginal positive correlation with parameter of high IOP. We conclude that OCTA can be used as a potential technique to evaluate the VD in JOHT and peripapillary scans should be analyzed individually based on different levels of CDR.

Frequency doubling technology, optical coherence technology and pattern electroretinogram in ocular hypertension

BACKGROUND

To assess which of three methods, namely, optical coherence tomography (OCT), pattern electroretinogram (PERG) or frequency-doubling technology (FDT), is the most sensitive and specific for detecting early glaucomatous damage in ocular hypertension (OH).

METHODS

Fifty-two patients with OH (24 men and 28 women, mean age of 56 ± 9.6 years) with an intraocular pressure (IOP) > 21 mm Hg and fifty-two control patients (25 men and 27 women, mean age of 54.8 ± 10.4 years) with IOP < 21 mm Hg, were assessed. All the patients had normal visual acuity, normal optic disk and normal perimetric indices.All subjects underwent OCT, FDT and PERG. Data were analyzed with unpaired t-tests, Chi-square test and Receiver Operating Characteristic (ROC) curve analyses.

RESULTS

In patients with OH, OCT showed retinal nerve fiber layer (RNFL) thinner than in control group in the superior quadrant (130.16 ± 10.02 vs 135.18 ± 9.27 μm, respectively; p < 0.011) and inferior quadrant (120.14 ± 11.0 vs 132.68 ± 8.03 μm; p < 0.001). FDT showed a significantly higher pattern standard deviation (PSD) (3.46  ± 1.48 vs 1.89 ± 0.7 dB; p < 0.001). With respect to PERG, only the amplitude showed significant differences (p < 0.044) between the two groups. ROC curve analysis revealed a sensitivity and specificity of 92% and 86%, respectively, for FDT-PSD (with an area under the ROC curve of 0.940), whereas with OCT, a sensitivity of 82% and a specificity of 74% was recorded in the inferior RNFL quadrant (with an area under the ROC curve of 0.806) finally with PERG amplitude we found a sensitivity of 52% and specificity of 77% (with an area under the ROC curve of 0.595).

CONCLUSIONS

FDT is the most sensitive and specific method for detecting early glaucomatous damage in eyes with OH, and together with OCT, can be useful in identifying those patients who may develop glaucoma.

TRIAL REGISTRATION

ISRCT number: ISRCTN70295497.

[Arguments against pressure-lowering treatment of ocular hypertension. Prophylactic treatment is unnecessary]

The main argument against a pressure-lowering treatment for patients with ocular hypertension (OHT) is the principle of "first do no harm". The imprecision of intraocular pressure (IOP) measurements and the fact that increased IOP is only a risk factor for glaucoma raise major doubts on a clinical definition of OHT. The use of IOP-lowering treatment in the absence of functional or morphological glaucomatous changes should only be initiated if the IOP is very high (>32 mmHg). If the IOP is between 21 and 32 mmHg the glaucoma conversion risk of the individual patient should be estimated. The risk factors as proven in major prospective trials (OHTS/EGPS) should be assessed using the risk calculator. Only patients with a high risk (>13%) of conversion profit from prophylactic IOP-lowering treatment. For all patients with intermediate or low risk of conversion the potential side-effects (local and systemic) of the treatment outweigh the possible benefit, so that the principle of "watchful waiting" is the best for patients with OHT. If morphological or functional progression is observed IOP-lowering treatment should be started immediately.

Meta-analysis of randomized controlled trials comparing timolol with brimonidine in the treatment of glaucoma

This paper aims to compare the efficacy and tolerability of timolol versus brimonidine in the treatment of glaucoma. Comprehensive searches were performed using Medline, Embase and the Cochrane Controlled Trials Register for randomized controlled trials comparing timolol and brimonidine. Two reviewers independently assessed trials for eligibility and quality and extracted data. A random effects model was used to combine studies. Outcome was defined as the absolute mean intraocular pressure (IOP) reduction from baseline to end-point for efficacy, and relative risk (RR) for adverse events. Subgroup analysis and meta-regression were used to explore heterogeneity according to trial design and quality. Ten publications reporting on eight trials with 2387 participants were included in the meta-analysis. Two further trials were commented on qualitatively. IOP reduction was not significantly different between timolol and brimonidine. Weighted mean difference (WMD) of IOP reduction was 0.24 mmHg (favouring brimonidine) with a 95% confidence interval of -0.57 to 1.04 mmHg. There was significant heterogeneity between studies (chi(2) (13) = 73.75, P < 0.00001, I(2) = 91%). Subgroup analysis showed no significant WMD for studies where data were analysed from end-points >/=6 months or <6 months. Meta-regression analysis showed increased WMD IOP reduction in favour of brimonidine with increased trial quality (t(3) = -4.58, P = 0.01), but no significant association with trial duration (t(3) = 0.73, P = 0.51) or size (t(3) = -0.59, P = 0.57). The RR of ocular allergy was much lower with timolol than brimonidine (RR = 0.08, 95% confidence interval 0.01 to 0.47). Publication bias was not evident on a funnel plot, although the number of studies was small. The conclusion is that both drugs are equally effective in lowering IOP. Brimonidine is associated with a higher rate of allergy.