Change in visual field defect is not a sufficient measure of visual impairment due to glaucoma progression, report researchers in Chile.3999/A278 In a retrospective review of 99 eyes of 71 patients, researchers measured visual field progression by change of field defect, progression of mean defect, or by glaucoma progression analysis via Humphrey perimetry. Twenty eyes demonstrated progression according to one of the criteria, 28 eyes progressed according to two, and one eye met all three criteria for progression. Nearly 32.4% (23 eyes) were fast progressors—these eyes were thought to be well controlled, but apparently were not. Measuring the progression of visual field defect or GPA, however, were more successful—these effects correlated and led to more effective care.
But, which intraocular pressure parameter correlates most closely with visual field progression in treated glaucoma patients? Researchers examined the charts of all patients seen at one referral practice between the years of 1999 and 2009.3496 They found that eyes that progressed demonstrated thinner corneas, higher mean IOP, higher peak IOP and greater IOP fluctuation than non-progressing eyes. Peak IOP proved to correlate most with field progression, so it should be minimized in eyes that demonstrate progression in hopes of slowing it, suggest researchers.
Can Heidelberg Retina Tomograph imaging of the optic nerve head predict glaucoma progression? Researchers in New York set out to answer this question, and they found that HRT can identify eyes at increased risk for glaucoma progression, especially when longitudinal data are available.4006/A285 Of 220 eyes, 69 (31%) progressed while 151 (69%) remained stable. Many HRT factors correlate with progression outcome in univariate analysis, but in multivariate logistic regression of all significant parameters, only the percent change of mean cup depth and height variation contour remained significant. Researchers were able to correctly classify almost 72% of patients in the study.
The presence of optic disc (Drance) hemorrhage in glaucoma has been well established. But is it more than just a sign of glaucoma? The location of optic disc hemorrhage may indicate progression of glaucomatous changes—specifically, laminar and marginal hemorrhages may reflect more rapid glaucomatous progression.4005/A284 Researchers followed 71 patients and monitored for laminar, marginal, rim or peripapillary disc hemorrhage. Patients’ first hemorrhages were most likely rim (56.3%), marginal (26.8%) or laminar (5.6%). But, laminar and marginal were more frequently observed (33.3% and 50.0%, respectively) in repeat hemorrhages, and optic disc deterioration was significantly greater in these patients than in those with other hemorrhages.
Are Professional Guidelines Enough?
Researchers in North Carolina and Alabama set out to understand the
baseline content of care of community-based O.D.s for patients with
glaucoma according to the guidelines set by the American Optometric
Association.180/A403 Researchers questioned 42 optometrists and
analyzed their content of care in patient evaluations. During the
initial history-taking, respondents performed anywhere from 13% to 75%
of recommended items—95% inquired about family glaucoma history, but
none assessed the impact of vision on daily activities. During the
exam, respondents performed 37% to 92% of the recommended elements—100%
obtained a visual field, and more than 90% imaged the optic nerve head.
Researchers note that, similarly to ophthalmologists, optometrists vary
significantly in their conformity to professional guidelines.
Hot Topics in Glaucoma
The Rho-kinase inhibitor AR-12286 provides clinically and statistically
significant ocular hypotensive efficacy in patients with ocular
hypertension and glaucoma.1633 One of three concentrations of AR-12286
or vehicle was given to patients for a dosing regimen of q.d. a.m. for
seven days, then q.d. p.m. for seven days, then b.i.d. for seven days.
All three concentrations of AR-12286 reduced mean IOP—reduction was
dose dependent, however, and peak effects occurred between two and four
hours after dosing. A concentration of 0.25% demonstrated the longest
duration effect, but also had side effects of trace to moderate
conjunctival hyperemia that typically lasted four hours or less.
Gene research yields better information each year; we’re seeing significant improvements in genetic testing as a viable tool for the diagnosis and treatment of many diseases. The gene in the GLC1F family responsible for POAG has been identified as the mutation T270T.1629 The gene was expressed in the trabecular meshwork, heart and skeletal muscles in at least two spliced forms. It was also expressed in the juxtacanalicular region, as well as the inner and outer walls of Schlemm’s canal. This gene is responsible for 6.6% of all cases of POAG, note researchers.
Clinical Science of IOP
Intraocular pressure remains the most significant component of the evaluation and treatment for glaucoma. Researchers at ARVO this year explored how variables from body mass index to differences in physical position affect results and repeatability—what is the significance of these factors?
Elevated body mass index (BMI) is associated with increased IOP while sitting, found researchers in Texas.3494 Researchers set out to clarify the known relationship between intra-abdominal pressure and IOP and to determine the role that BMI plays. Applanation tonometry was used to measure IOP in patients’ eyes while reclining and while seated. Researchers found that, beginning with a BMI of 21.4kg/m2, each one-unit increase in BMI was associated with a 0.07mm Hg increase in IOP while seated. Likewise, although not statistically significant, every 1cm increase in abdominal circumference was associated with a 0.02mm Hg increase in IOP.
Researchers in Greece measured the differences in IOP when taken in the sitting, supine and Trendelenburg (30º inverted) positions for both glaucomatous patients and normal controls.986/A343 They found that IOP increases when supine and in the Trendelenburg position in both normal and glaucomatous patients; however, glaucoma patients tended to show a larger increase than normal patients did.
How stable and reliable is successive applanation tonometry in a glaucomatous eye?554/A350 In this prospective study, 67 glaucoma patients underwent four successive IOP measurements via Goldmann-type applanation tonometry. Researchers found a significant decrease between the first and second measurements, and likewise, between the first and all subsequent measurements. But, the control group demonstrated no significant decrease in IOP.
Can the asymmetry of IOP be used diagnostically?585/A381 Researchers found a direct relationship between the amount of IOP asymmetry between eyes and the likelihood of having glaucoma. A difference of 3mm Hg correlates with a 10% chance of having glaucoma; a 6mm Hg difference correlates to a 50% chance; and any greater difference is associated with a 100% probability of having glaucoma. The unadjusted odds ratio indicates that, with a rise of every 1mm Hg in IOP asymmetry, the patient’s risk of glaucoma doubles—a very significant observation. Conversely, IOP symmetry is associated with only a 0.5% probability of having glaucoma.
Mozart and Visual Fields?
The Mozart Effect does not enhance the reliability of the visual field
test to a statistically significant degree, report researchers from
Philadelphia and Spain.5521/A576 In the study, 160 glaucoma patients
were randomized into one of three groups: noise-cancellation
headphones; music (Mozart’s Sonata for Two Pianos in D Major); or
control. Median values for fixation losses did not differ significantly
among the three groups. Likewise, there were no significant differences
among the rate of false positives or negatives. And, there were no
improvements seen in fixation loss during Humphrey visual field testing.
Glaucoma Patients’ Risk of Car Accident
Patients with severe POAG and hemi-visual field defects are at higher
risk for a car accident than non-glaucomatous patients, found
researchers in Japan.189/A412 Researchers interviewed 121 patients with
POAG and found that 5.7% of glaucoma patients had been in an accident
vs. only 3.4% of control patients. Aside from best-corrected visual
acuity, researchers found no other significant difference between the
groups.
Risk Factors for Glaucoma
The identification of risk factors contributes to our ability to better predict a patient’s likelihood of having glaucoma or progression.
Many vascular risk factors are involved in and interrelated with the pathogenesis of normal-tension glaucoma, report researchers in Italy.2683/D672 Notably, altered capillaroscopy was more frequent in NTG patients, and endothelin-1 values were higher. Diastolic ocular perfusion pressure and nitrate levels were lower in NTG patients. Several other factors, such as plasma values and retrobulbar hemodynamics were also measured and demonstrated differences between normal and normal-tension glaucomatous patients. But, researchers note that, “Inappropriate retrobulbar vasoconstriction in response to low diastolic ocular perfusion pressure seemed to be a main determinant of optic nerve damage in vasospastic subjects with normal-tension glaucoma.”
Glycosylated hemoglobin (HbA1c) significantly affects both short- and long-term fluctuations of IOP in healthy patients, report researchers in Turkey.2674/D663 In this retrospective clinical trial of 112 eyes, researchers measured IOP five times each for five days, and they performed blood work-ups on each patient as well. Results showed a significant correlation between HbA1c and mean short- and long-term IOP fluctuation.
What role does internal carotid artery (ICA) stenosis play in ocular pulse amplitude (OPA)? There’s a significant negative correlation, according to researchers.2697/D686 In this prospective study, ICA was measured by color duplex ultrasound, and OPA was determined by dynamic contour tonometry. The results: the difference of the OPA measurements between both eyes of an individual showed a significant negative correlation with the difference between the ICA measurements. Researchers note that the OPA could be valuable as a non-invasive screening parameter for asymptomatic internal carotid artery stenosis.
Relative afferent pupillary defect (RAPD) can be an effective diagnostic tool for glaucoma in phakic patients, found researchers in California.183/A406 The odds ratio was 9.71 for glaucomatous disease if an RAPD was present, with a sensitivity of 66.7% and specificity of 82.5%, they found. A subanalysis of phakic patients revealed an odds ratio of 17.05 for glaucomatous disease in the presence of an RAPD, with a sensitivity of 68.8% and specificity of 88.6%.
New Insights Into Glaucomatous Disease
If glaucomatous damage is initially detected thanks to either disc progression or visual field abnormality, the patient is more likely to develop reproducible damage regarding the other, report researchers in the Ocular Hypertension Treatment Study.2047 Researchers took visual fields every six months and stereoscopic optic disc photographs every 12 months. Median follow-up duration with patients after an initial diagnosis of POAG, based on either disc progression or visual field abnormality, was 7.9 years. Those who were diagnosed due to a visual field abnormality were more likely to develop disc deterioration (49%) than the other way around (38%), but researchers noted that developing the second endpoint was still a very significant likelihood for patients.
Further results from the African Descent and Glaucoma Evaluation Study (ADAGES) suggest that early disease presentation signifies ancestry-related differences.2052 Researchers had previously reported that people of African descent had slightly worse visual function than those of European descent. But, further analysis revealed no significant differences regarding age, high blood pressure, heart disease and family history of glaucoma. However, more African-descent patients had diabetes than European-descent patients, and a significantly larger portion of African-descent patients showed normal results at baseline and abnormal results at follow-up than European-descent patients did.
An ancillary study to OHTS found that the rate of structural change of the optic disc is roughly five times faster in eyes that have developed POAG vs. those that have not.2048 Researchers used HRT optic disc parameters to measure the discs of 439 patients (866 eyes) in the Confocal Scanning Laser Ophthalmoscopy Ancillary Study to the OHTS. Fifty patients developed POAG. The rate of rim area loss was significantly faster in eyes that developed POAG, as well as the rate of change of cup volume and rim disc ratio. Researchers note that accurate measurement of structural change can provide information for patients’ clinical management.
Can an alarm remind patients to take their drops?181/A404 Researchers in Germany found that a simple visual and aural device could improve dose adherence by 17% in this study of 18 patients, who each were on a regimen of one drop, five times daily. The number of missed doses decreased by 56%—a very significant reduction, the researchers note. They suggest that such reminder systems could very effectively reduce non-adherence.
Long-term latanoprost use can decrease central corneal thickness in patients with normal-tension glaucoma, found researchers in Korea.179/A402 In a retrospective study of 166 newly-diagnosed patients who took only latanoprost for a period of at least two years, researchers found a mean CCT of 535.5±37.9µm in the latanoprost group vs. 543.1±40.2 in the control group. Researchers note that clinicians must pay attention to longitudinal CCT variations during follow-up so as to properly target IOP. The results of this study and others points out the importance of repeat measurement of central corneal thickness.
