Contralateral effect of topical beta-adrenergic antagonists in initial one-eyed trials in the ocular hypertension treatment study

The monocular trial controversy: a critical review

PURPOSE OF REVIEW

The utility of the monocular trial to determine the response to topical ocular hypotensive medications has been recently debated. This review provides a critical evaluation of recent studies and discusses factors that affect the accurate determination of medication response.

RECENT FINDINGS

Recent concerns about the validity of the monocular trial arise from studies reporting a low-to-moderate correlation of intraocular pressure (IOP) response between the first and second eyes to the same topical ocular hypotensive medication. Few studies, however, have addressed the classic monocular trial that adjusts IOP in the trial eye based on IOP change in the fellow eye. Conflicting results from prior studies are due to differences in study question, study design, and method of analysis. Factors such as variability of IOP, diurnal variation, and regression to the mean further complicate the understanding of whether monocular trials or binocular simultaneous trials (i.e. testing each eye separately) are better for determining medication effect.

SUMMARY

The issue of whether or not to use the monocular trial remains controversial. A more clear understanding of factors such as nontherapeutic variability of IOP within the same eye and between eyes may elucidate the answer to this question. Further studies of monocular and binocular trials are needed to clarify which method better estimates medication response.

A pilot study of topical treatment with an alpha2-agonist in patients with retinal dystrophies

PURPOSE

The aim of this study was to assess the neuroprotective effect of a topical alpha2-agonist in patients with retinal dystrophies.

METHODS

This study was a prospective, placebo-controlled, double-masked, randomized clinical trial. A total of 26 patients with retinal dystrophies were included. One (1) randomly selected eye was treated with brimonidine tartrate 0.2% twice-daily, while the fellow eye received artificial tears. Disease progression parameters tested at 6-8-month intervals throughout the study included Goldmann visual fields, contrast sensitivity, color vision, and fullfield electroretinography.

RESULTS

Seventeen (17) of the 26 recruited patients completed the study. Except for 1 patient with an 18-month follow-up, all patients were followed up for 24-36 months (mean, 29). At the conclusion of the study, there were no differences detected in visual acuity, color vision, and contrast sensitivity between the treated and control eyes. There was a trend, however, toward a lesser degree of visual field loss in the brimonidine-treated eyes. There was also a delay in the time required to reach a 25% visual field loss in the treated eyes. These differences were more pronounced in a subgroup of patients diagnosed as retinitis pigmentosa and with visual fields of 5 cm2 or more at baseline.

CONCLUSIONS

The findings of this pilot study suggest a trend for slower progression in the eyes of patients with retinal dystrophy when treated with brimonidine, according to one of the parameters that was studied (visual field loss). Further studies that include a larger number of patients and a longer follow-up period are needed to clarify and confirm the potential neuroprotective effect of alpha2-agonists in human retinal dystrophies.

Interpretation of uniocular and binocular trials of glaucoma medications: an observational case series

Background

To predict the effectiveness of topical glaucoma medications based on initial uniocular and binocular treatment. To test a traditional hypothesis that effectiveness following a uniocular trial is associated with the change in IOP in the initially treated eye minus the change in the initially untreated eye. To determine whether uniocular or binocular treatment trials are superior.

Methods

Based on a review of medical records, we identified 168 instances in 154 patients with bilateral primary open angle glaucoma of initial uniocular use of a topical glaucoma medication with well-documented intraocular pressure (IOP) readings at baseline (IOP_A), during the trial (IOP_B), and at follow-up (IOP_C). Abstracted data included demographic data, IOP, and medication use. Predictors of the IOP following the trial (IOP_C) in each eye were identified by multivariable linear regression. In 70 cases, the predictive ability of initial uniocular and binocular treatment could be directly compared.

Results

In a multivariable analysis, the follow-up pressure in the initially treated eye (IOP_1C) was directly correlated with treated eye IOP during initial uniocular use (IOP_1B, p < 0.001). In a multivariable analysis, the follow-up pressure in the initially untreated eye (IOP_2C) was directly correlated with its baseline IOP_2A (p < 0.001), and also tended to be associated with treated IOP_1B (p = 0.07). The multivariable regression coefficient (b) for the IOP change in the initially untreated eye was generally not close to the value of -1 expected by the classic teaching (for eye 1, b = 0.04, p = 0.35; for eye 2, b = 0.07, p = 0.50). In 70 cases, the uniocular and binocular trials predicted a similar fraction of the variance in follow-up IOP_1C (r² = 0.56 and 0.57, respectively) and IOP_2C (r² = 0.39 and 0.38, respectively).

Conclusion

1) For uniocular trials, the IOP change in the untreated eye should not be subtracted from that in the treated eye. 2) Uniocular and binocular trials have similar predictive value when interpreted correctly. Either may be selected based on clinical circumstances.

Concordance of diurnal intraocular pressure between fellow eyes in primary open-angle glaucoma

PURPOSE

To study the concordance of diurnal intraocular pressure (IOP) between fellow eyes in primary open-angle glaucoma (POAG).

DESIGN

Retrospective chart review.

PARTICIPANTS

Ninety-three POAG patients.

METHODS

Patients who met the definition of POAG and underwent diurnal curve measurement were included. Subjects were excluded if there was a history of surgery, trauma, ocular vascular disease, incomplete diurnal curve, or asymmetric ocular medication use. Patients on symmetric ocular medication were included and analyzed separately. Goldmann applanation tonometry was performed at 10 am, 1 pm, 4 pm, 7 pm, 10 pm, and 7 am (the next day). The following statistical analyses were performed: (1) average Pearson correlation coefficient (r) from individual correlations of right and left eye IOP over the 6 time points for each subject; (2) linear mixed model analysis for repeated measures, with eye (right and left) and time as the within-subject fixed effects, and (3) absolute difference in change in IOP between fellow eyes over each time interval and probability that the difference was within 2 or 3 mmHg.

MAIN OUTCOME MEASURE

The concordance of the IOP between fellow eyes as measured by absolute difference in change in IOP between fellow eyes and probability of the difference being within 2 or 3 mmHg.

RESULTS

Thirty-seven patients were untreated and 56 were treated on symmetric IOP-lowering medications. The diurnal curves of fellow eyes exhibited parallel profiles according to the linear mixed model. The average difference in the change of IOP between fellow eyes over given time intervals ranged from 1.6 to 2.0 mmHg. The estimated probability that the absolute change in IOP between fellow eyes was within 2 mmHg was 68% to 90%, and within 3 mmHg was 78% to 95% for all time intervals.

CONCLUSION

The diurnal variation of IOP in POAG is largely concordant between fellow eyes. For any given time interval, the fellow eye IOPs may fluctuate asymmetrically a minority of the time. Clinicians who utilize the uniocular trial should be aware of the limit of the IOP concordance.

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

When to treat the patient who presents with ocular hypertension has been a question that has 'stumped' the ophthalmic community for decades. Population-based studies and intervention trials have provided the basis for understanding why we consider treating such patients. Although the EGPS (European Glaucoma Prevention Study) did not demonstrate that reducing intraocular pressure (IOP) with dorzolamide prevented the onset of glaucoma compared with individuals receiving a placebo, the investigators of the OHTS (Ocular Hypertension Treatment Study) found that the treatment of ocular hypertension can be delayed with topical medication when treated patients were compared with an observation group. There are differences in inclusion criteria, study design and retention rates between the EGPS and the OHTS, which may have led to the discrepancies in outcomes between these two studies. These differences provide a basis for understanding the relevance of the findings of both trials to clinical practice. The clinician should consider key risk factors such as age, thin corneal thickness measurements, large cup-to-disc ratio and mean IOP when determining who should be treated. However, the ultimate decision of when to treat will be determined by other issues such as life expectancy, the general health of the patient and the number of risk factors. Clearly, the treatment of only high-risk patients with ocular hypertension should be considered.

Long-term follow-up of initial trabeculectomy with mitomycin C for primary open-angle glaucoma in Japanese patients

PURPOSE

To determine the long-term intraocular pressure (IOP) control and postoperative complications after initial trabeculectomy with use of mitomycin C (MMC) in patients with primary open-angle glaucoma (POAG).

PATIENTS AND METHODS

A retrospective review was conducted of a consecutive series of 123 eyes (87 patients) with POAG who underwent initial trabeculectomy with MMC and had at least 4 years of follow-up. All patients underwent standard trabeculectomy with 0.04% MMC applied intraoperatively for 3 minutes. The long-term outcomes (IOP control and bleb leak, long-standing hypotony, bleb-related infections) were analyzed with the Kaplan-Meier life-table method on the basis of three definitions of successful IOP control (defined as IOP <18 mmHg (definition 1), IOP <16 mmHg (definition 2), and IOP decrease of by > or =30% and <21 mmHg (definition 3)).

RESULTS

The mean follow-up time was 6.8+/-1.4 (mean+/-SD) years. The cumulative survival rates were 67.0+/-4.6%, 44.5+/-5.4%, and 74.1+/-4.2%, respectively, based on definitions 1, 2, and 3, 8 years postoperatively by life-table analysis. At 8 years, bleb leak occurred in 7.9+/-2.6% of eyes, long-standing hypotony in 8.3+/-2.5%, and bleb-related infections in 5.9+/-2.4%.

CONCLUSION

Long-term outcome after initial trabeculectomy with MMC in Japanese POAG patients is comparable with that reported in other populations and with that after trabeculectomy with 5-fluorouracil.

[Results of the "Ocular hypertension treatment study"]

Ocular hypertension (OHT) is defined as intraocular pressure (IOP) elevated above normal levels which occurs without detectable damage to the papilla or visual field. It is considered to be the most important risk factor for developing primary open-angle glaucoma (POAG). The "Ocular hypertension treatment study" (OHTS) addresses the issue of whether lowering IOC before damage to the papilla or visual field occurs can hinder their development and whether OHT can be treated categorically. This randomized, prospective, nonmasked and non-placebo-controlled, multicenter study documents the protective effect of prophylactic lowering of IOC and identifies and explains the risk factors for developing POAG. These include advancing age, reduced corneal thickness, increased pattern standard deviations in white-on-white perimetry, and elevated vertical or horizontal cup to disc ratio. Due to the large individual differences in risk distribution and the very high costs of treating OHT, the question of whether OHT should be treated on principle remains open in the OHTS. This decision must be made on an individual basis after each patient's risk has been assessed.

Five-year follow up of selective laser trabeculoplasty in Chinese eyes

PURPOSE

To study the effectiveness and safety of selective laser trabeculoplasty (SLT) on primary open-angle glaucoma and ocular hypertension in Chinese eyes.

METHODS

This was a prospective randomized controlled clinical study in which 58 eyes of 29 patients with primary open-angle glaucoma or ocular hypertension were included. One eye of each patient was randomized to receive SLT (Group 1) and the fellow eyes received medical treatment (Group 2). Patients were evaluated after laser treatment at 2 h, 1 day, 1 week, 2 weeks, 1 month, 3 months, 6 months, and then yearly.

RESULTS

All patients (13 male, 16 female) were Chinese. The mean age was 51.9 +/- 14.7 years. The mean baseline intraocular pressure was 26.8 +/- 5.6 mmHg in group 1 and 26.2 +/- 4.2 mmHg in group 2 (P = 0.62). The failure rate, defined as intraocular pressure >21 mmHg with maximal medications, was 17.2% in group 1 and 27.6% in group 2 at 5-year follow-up (P = 0.53). Eight eyes (27.6%) in group 1 required medications to control the intraocular pressure to below 21 mmHg. There was no statistically significant difference in the intraocular pressure reductions between the two groups at all time intervals (P > 0.05). The mean number of antiglaucoma medications was significantly lower in the SLT than the medical treatment group up to 5 years of follow up (P < 0.001). Transient post-SLT intraocular pressure spike >5 mmHg was observed in three eyes (10.3%).

CONCLUSION

With fewer medications, SLT gives similar intraocular pressure reduction to medical therapy alone in Chinese patients with primary open-angle glaucoma or ocular hypertension.

Drug delivery to the posterior segment from drops

The published evidence that instilled drugs can affect the blood supply to the retina and optic nerve head in humans is examined. As a background, seven techniques that have been used to measure flow are briefly described and criticized. For timolol, the corresponding measurements, obtained by a number of investigators are evaluated. The outcome is very erratic and does not allow any conclusion as to the effect of this drug on flow. Consideration is then given to the possible mechanism whereby a drug could affect blood flow; directly, by diffusion to receptors on the vessels, or indirectly, through more anterior receptors. The question is raised whether the small changes in circulation induced by drugs would not be swamped by those resulting from natural alterations in the ambient light level. The literature was analyzed in the hope of identifying discrete entry pathways, for example, through the lens or the suprachoroidal space, that are sufficiently permeable to allow a significant quantity of drug to pass. There was an indication that a drug might diffuse through the lens cortex in sufficient quantity to cause a measurable rise in its concentration in the vitreous. In general, however, there was insufficient quantitative data to allow any meaningful predictions to be made. Stimulated by recent evidence, it is suggested that drug penetration from the tear fluid takes place by direct diffusion across the conjunctiva into the sclera and orbit when the head is supine.