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Do More Data Points Reveal Clearer Trends? Power and Noise in VF Progression · Glaucoma, Vision & Longevity: Supplements & Science

• 0:00
  SPEAKER_00: Do more data points reveal clearer trends?
• 0:02
  SPEAKER_00: Power and noise in visual field progression.
• 0:05
  SPEAKER_00: Introduction.
• 0:06
  SPEAKER_00: In glaucoma, visual field testing is used to determine whether vision is stable or gradually worsening.
• 0:12
  SPEAKER_00: The challenge is that each test contains some noise attention, fatigue, learning, cataract, dry eye, fixation, and the patient's underlying level of damage can all affect the result.
• 0:23
  SPEAKER_00: Testing more often usually makes a true trend easier to recognize.
• 0:27
  SPEAKER_00: However, the benefit is not proportional.
• 0:30
  SPEAKER_00: Moving from one test per year to two often provides a meaningful gain.
• 0:35
  SPEAKER_00: Moving from two to three tests per year may help, but the additional benefit is smaller.
• 0:41
  SPEAKER_00: Testing too often can also create more apparent changes that later disappear, especially when statistical thresholds are applied repeatedly.
• 0:50
  SPEAKER_00: The practical goal is therefore not to collect the largest possible number of visual fields.
• 0:55
  SPEAKER_00: It is to collect enough high-quality tests, spaced appropriately, to detect clinically important progression without creating unnecessary burden or false alarms.
• 1:05
  SPEAKER_00: Current glaucoma guidance supports at least annual testing for established glaucoma, with more frequent testing during the first two years after diagnosis or when the risk of rapid progression is high.
• 1:17
  SPEAKER_00: Why visual field progression is difficult to detect.
• 1:21
  SPEAKER_00: A visual field test measures light sensitivity at many locations.
• 1:25
  SPEAKER_00: The result is not a direct photograph of the optic nerve.
• 1:29
  SPEAKER_00: It is a behavioral measurement that depends on the patient noticing and responding to visual stimuli.
• 1:35
  SPEAKER_00: A simple way to describe a visual field series is observed result equals true visual function plus measurement noise.
• 1:43
  SPEAKER_00: The true glaucoma signal may be a gradual decline of only a fraction of a decibel per year, while the variation between individual tests can be several decibels at some locations.
• 1:53
  SPEAKER_00: Test-retest variability tends to be greater in eyes with more advanced damage, lower sensitivity, peripheral defects, and certain defect patterns.
• 2:03
  SPEAKER_00: Mean deviation.
• 2:04
  SPEAKER_00: Mean deviation is a single summary number describing the overall visual field compared with an age-adjusted normal field.
• 2:11
  SPEAKER_00: A negative number indicates loss, a more negative number indicates greater overall loss.
• 2:17
  SPEAKER_00: Mean deviation is useful because it averages information across the field and is relatively easy to follow over time.
• 2:23
  SPEAKER_00: A clinician can plot mean deviation against time and calculate a slope, such as 0.3 decibels per year, slow change, minus 1.0 decibels per year, rapid change.
• 2:38
  SPEAKER_00: However, mean deviation can miss localized progression if the damaged area is small.
• 2:43
  SPEAKER_00: It can also be influenced by diffuse factors such as cataract or other media opacity.
• 2:49
  SPEAKER_00: Pointwise slopes.
• 2:51
  SPEAKER_00: Pointwise linear regression evaluates each test location separately.
• 2:55
  SPEAKER_00: It can show that a particular cluster of locations is worsening at, for example, minus 1.2 decibels per year.
• 3:02
  SPEAKER_00: This approach can detect localized or paracentral progression that is diluted within a whole field average.
• 3:08
  SPEAKER_00: Its disadvantages are that individual locations are noisier than the overall mean.
• 3:13
  SPEAKER_00: Many locations are tested simultaneously, and the chance of at least one apparently significant result increases as more locations and more visits are examined.
• 3:22
  SPEAKER_00: How increasing test frequency improves signal to noise.
• 3:26
  SPEAKER_00: For a trend analysis, additional tests help in two ways.
• 3:30
  SPEAKER_00: They provide more observations, reducing uncertainty about the estimated slope.
• 3:35
  SPEAKER_00: They show whether a change is persistent, rather than a single unusually poor result.
• 3:41
  SPEAKER_00: The timing of the tests also matters.
• 3:43
  SPEAKER_00: A slope is estimated more precisely when tests are distributed across a longer time span.
• 3:49
  SPEAKER_00: Three tests performed within a few weeks provide a better estimate of short-term repeatability, but three tests spaced over a year provide more information about long-term decline.
• 4:00
  SPEAKER_00: This is why two baseline tests close together can be useful for learning and repeatability, while later tests should usually be spread across the follow-up period.
• 4:10
  SPEAKER_00: The European Glaucoma Society emphasizes that determining an individual rate of progression generally requires at least two years and enough reliable visual fields.
• 4:20
  SPEAKER_00: Simulation evidence, the largest gains occur early high.
• 4:24
  SPEAKER_00: Mean deviation one versus two vs.
• 4:26
  SPEAKER_00: three tests per year.
• 4:28
  SPEAKER_00: Wu and colleagues used real visual field variability from 1072 eyes and reconstructed visual field series through computer simulation.
• 4:36
  SPEAKER_00: Their analysis required two baseline tests and a confirmatory test before progression was counted.
• 4:43
  SPEAKER_00: The estimated time required to detect progression in 80% of eyes was, for the full table, please open this article on visualfieldtest.com.
• 4:52
  SPEAKER_00: These results show two important principles.
• 4:55
  SPEAKER_00: Increasing testing from once to twice yearly produced a substantial improvement.
• 5:00
  SPEAKER_00: Increasing testing from twice to three times yearly produced a smaller improvement.
• 5:05
  SPEAKER_00: For a rapidly progressing eye losing minus 2.0 decibels per year, moving from annual to six-monthly testing shortened modeled detection time by approximately 0.9 years.
• 5:16
  SPEAKER_00: Moving from six-monthly to four-monthly testing shortened it by only about 0.3 years.
• 5:22
  SPEAKER_00: For a slower eye losing minus 0.5 decibels per year, even three tests per year required approximately five years to achieve 80% detection power.
• 5:31
  SPEAKER_00: More frequent testing helps, but it cannot completely overcome a very small signal or high measurement variability.
• 5:40
  SPEAKER_00: An earlier practical analysis reached a similar conclusion.
• 5:43
  SPEAKER_00: For an eye with average variability, approximately three tests per year were estimated to be needed to detect a 4-DB mean deviation decline over two years with 80% power.
• 5:54
  SPEAKER_00: The authors recommended six reliable examinations during the first two years to establish a baseline and identify unusually rapid progression.
• 6:03
  SPEAKER_00: Pointwise slopes, greater sensitivity, but more false alarms.
• 6:07
  SPEAKER_00: Gardner and Crab developed a virtual eye simulation in which a test location was either stable or deteriorating at a known rate.
• 6:15
  SPEAKER_00: When a location was truly worsening at 2 dB per year, more frequent testing allowed pointwise linear regression to identify progression sooner.
• 6:25
  SPEAKER_00: But when the simulated location was stable, increasing test frequency also increased the number of series falsely labeled as progressing during the early years.
• 6:35
  SPEAKER_00: Their conclusion was that three tests per year provided a practical compromise between sensitivity and specificity for pointwise linear regression.
• 6:44
  SPEAKER_00: This is an important qualification.
• 6:47
  SPEAKER_00: More data improve the chance of detecting ill trend, but they also create more opportunities to observe an unusual sequence of results.
• 6:55
  SPEAKER_00: Statistical methods therefore need confirmation rules and appropriate thresholds.
• 7:00
  SPEAKER_00: What real-world visual field series show?
• 7:03
  SPEAKER_00: The Advanced Glaucoma Intervention Study, Nuri Madavi and colleagues analyzed 468 eyes from the Advanced Glaucoma Intervention Study.
• 7:12
  SPEAKER_00: They compared the original, more frequent visual field series with a version in which approximately half of the later tests had been removed.
• 7:21
  SPEAKER_00: The high frequency series had a median interval of about six months, compared with approximately 11.3 months in the lower frequency series.
• 7:30
  SPEAKER_00: Progression based on mean deviation was detected in 43.6% of eyes with the more frequent series, 34.2% of eyes with the less frequent series.
• 7:40
  SPEAKER_00: Using pointwise linear regression, progression was detected in 39.5% of eyes with the more frequent series, 35.7% of eyes with the less frequent series.
• 7:52
  SPEAKER_00: The hazard of detecting mean deviation progression was 1.69 times higher with more frequent testing.
• 7:58
  SPEAKER_00: For pointwise linear regression, the hazard was 1.52 times higher.
• 8:03
  SPEAKER_00: The benefit was particularly evident with global mean deviation analysis.
• 8:08
  SPEAKER_00: This real-world analysis supports the simulation findings.
• 8:11
  SPEAKER_00: Six-monthly testing generally detects progression earlier than approximately annual testing, but the gain is larger for mean deviation than for pointwise slopes.
• 8:21
  SPEAKER_00: Real-world testing in the United States.
• 8:24
  SPEAKER_00: A more recent study used real-world visual field variability from the Duke glaucoma registry and simulated progression at testing frequencies observed in a large United States insured population.
• 8:35
  SPEAKER_00: For modeled progression rates of middled 0.5 or 1.0 decibels per year, the time required to detect progression in 80% of eyes was estimated as follows.
• 8:47
  SPEAKER_00: For the full table, please open this article on visualfieldtest.com.
• 8:52
  SPEAKER_00: These numbers are modeled estimates, not a prediction for every patient.
• 8:56
  SPEAKER_00: They nevertheless demonstrate how infrequent testing can delay recognition of progression for many years.
• 9:02
  SPEAKER_00: The study also found that more than three-quarters of patients in the underlying nationwide cohort received fewer than one visual field test per year.
• 9:12
  SPEAKER_00: Frontloading tests.
• 9:14
  SPEAKER_00: A 2024 simulation study used progression rates and baseline characteristics from Swedish and Canadian glaucoma cohorts.
• 9:22
  SPEAKER_00: It compared one visual field test per visit with a front loaded strategy involving two tests per visit.
• 9:28
  SPEAKER_00: When visits occurred every six months, frontloading detected progression approximately one to one and a half years earlier in many scenarios.
• 9:37
  SPEAKER_00: At four years, it increased the proportion of detected progressors by roughly 27% to 32%, depending on the amount of missing data.
• 9:46
  SPEAKER_00: The simulated eyes also had less visual field loss when progression was detected.
• 9:52
  SPEAKER_00: Front loading may be useful when a clinician needs to establish a reliable baseline quickly or suspects that progression may be rapid.
• 9:59
  SPEAKER_00: However, two tests performed close together should not be treated as fully equivalent to two independent tests separated by several months.
• 10:08
  SPEAKER_00: Repeated testing in one session mainly improves knowledge of the current level and repeatability.
• 10:13
  SPEAKER_00: It provides less temporal information about the long-term slope.
• 10:17
  SPEAKER_00: Event-based versus trend-based analysis.
• 10:20
  SPEAKER_00: How the methods differ.
• 10:22
  SPEAKER_00: For the full table, please open this article on VisualFieldtest.com.
• 10:27
  SPEAKER_00: Event-based methods compare later tests with one or more baseline tests.
• 10:32
  SPEAKER_00: For example, the guided progression analysis on some instruments looks for repeated worsening at the same test locations.
• 10:40
  SPEAKER_00: A change seen on one test may be labeled possible progression, while repetition on subsequent tests may be labeled likely progression.
• 10:48
  SPEAKER_00: Trend-based methods use the relationship between test results and time.
• 10:53
  SPEAKER_00: They can estimate the rate of decline, which is important for deciding whether a patient is likely to develop meaningful disability during the expected lifetime.
• 11:02
  SPEAKER_00: Because the methods answer different questions, they should generally be viewed as complementary rather than competing.
• 11:09
  SPEAKER_00: What happens at different testing frequencies?
• 11:12
  SPEAKER_00: Approximately once per year.
• 11:15
  SPEAKER_00: When visual fields are obtained only annually, event-based methods may provide the first warning because they are designed to recognize repeated focal change from baseline.
• 11:26
  SPEAKER_00: Trend-based methods have relatively few observations and may lack statistical power, particularly for slow progression.
• 11:34
  SPEAKER_00: This does not mean event analysis is always more accurate.
• 11:37
  SPEAKER_00: It means that with sparse data, a threshold-based method may declare a change before a slope becomes statistically convincing.
• 11:45
  SPEAKER_00: This interpretation is consistent with clinical reviews and comparative studies.
• 11:51
  SPEAKER_00: Approximately every six months, six-monthly testing is often a useful middle ground.
• 11:56
  SPEAKER_00: It supplies enough points for a meaningful mean deviation trend while allowing event-based analysis to confirm focal changes within a reasonable time.
• 12:05
  SPEAKER_00: In the advanced glaucoma intervention study series, moving from approximately annual to six-monthly testing improves detection for both mean deviation and pointwise linear regression with a larger effect for mean deviation.
• 12:19
  SPEAKER_00: Approximately every four months, three tests per year provide more support for pointwise slopes.
• 12:26
  SPEAKER_00: This may be particularly helpful during the first two years after diagnosis, after a treatment change, or when there are risk factors for rapid loss.
• 12:35
  SPEAKER_00: However, pointwise analyses become more vulnerable to false positive findings as the number of tests and opportunities for statistical significance increase.
• 12:44
  SPEAKER_00: In a large 2026 series of 2,133 eyes with 12 consecutive visual fields, 21.4% had at least one apparent mean deviation progression event at a probability threshold of less than 0.05 that later reverted.
• 13:00
  SPEAKER_00: Stricter thresholds reduced the proportion of such reversions.
• 13:04
  SPEAKER_00: Head-to-head comparison.
• 13:06
  SPEAKER_00: In a computer simulation based on 367 glaucoma eyes followed for approximately 10 years, event-based and global trend-based methods had similar performance when their specificities were carefully matched.
• 13:19
  SPEAKER_00: After five years, progression was detected in 27.7% of eyes using a stricter event-based likely progression.
• 13:27
  SPEAKER_00: Criterion 24.6% using mean deviation trend analysis, 23.8% using visual field index trend analysis.
• 13:36
  SPEAKER_00: The less stringent event-based possible progression criterion had a five-year false positive rate of 34% compared with 7% for likely progression.
• 13:46
  SPEAKER_00: This illustrates why an initial alert should usually prompt confirmation rather than immediate treatment escalation.
• 13:52
  SPEAKER_00: The diminishing returns threshold.
• 13:54
  SPEAKER_00: The evidence suggests a practical threshold rather than a universal rule.
• 13:58
  SPEAKER_00: For global mean deviation trends, the major efficiency gain is usually achieved by moving from annual to six-monthly testing.
• 14:06
  SPEAKER_00: For pointwise slopes, approximately three tests per year can provide a reasonable sensitivity specificity balance.
• 14:13
  SPEAKER_00: Testing more often than three times per year is generally most useful for selected situations rather than routine monitoring of every patient.
• 14:22
  SPEAKER_00: The precise threshold depends on the true rate of visual field decline, test-retest variability, baseline visual field severity, age, and expected remaining lifetime, whether central or paracentral vision is threatened, intraocular pressure control, reliability of the patient's test performance, whether treatment has recently changed.
• 14:45
  SPEAKER_00: The European Glaucoma Society's 6th edition recommends that newly diagnosed glaucoma patients may be tested three times per year during the first two years.
• 14:53
  SPEAKER_00: After the initial period, testing can often be reduced and tailored to the observed rate of progression and disease stage.
• 15:01
  SPEAKER_00: How should tests be spaced across a year?
• 15:04
  SPEAKER_00: A practical schedule.
• 15:05
  SPEAKER_00: For the full table, please open this article on visualfieldtest.com.
• 15:10
  SPEAKER_00: The annual schedule should be thought of as a minimum for many patients with established glaucoma, not as an ideal schedule for someone newly diagnosed or at high risk.
• 15:20
  SPEAKER_00: The American Academy of Ophthalmology recommends at least yearly visual field evaluation and notes that three fields per year during the first two years can identify rapid progression earlier.
• 15:31
  SPEAKER_00: Fixed versus adaptive spacing.
• 15:34
  SPEAKER_00: A fixed schedule is simple.
• 15:36
  SPEAKER_00: Test every three, six, or twelve months.
• 15:39
  SPEAKER_00: An adaptive schedule changes the interval according to the most recent results.
• 15:43
  SPEAKER_00: In simulation work, testing every 12 months while the field appeared stable, followed by prompt confirmation when progression was suspected, produced higher specificity than fixed three-month testing and detected progression earlier than fixed six-month testing.
• 15:58
  SPEAKER_00: It also required fewer tests overall.
• 16:02
  SPEAKER_00: An adaptive approach may therefore be efficient.
• 16:05
  SPEAKER_00: Test more intensively while establishing the baseline.
• 16:09
  SPEAKER_00: Continue at six or 12-month intervals when the field is convincingly stable.
• 16:14
  SPEAKER_00: Bring testing forward when event analysis, mean deviation, pointwise slopes, optic nerve appearance, or optical coherence tomography suggests change.
• 16:23
  SPEAKER_00: Confirm the finding before making a major treatment decision.
• 16:27
  SPEAKER_00: Guidance for clinicians balancing burden with power.
• 16:31
  SPEAKER_00: Establish a clean baseline.
• 16:33
  SPEAKER_00: Obtain at least two reliable baseline fields when possible.
• 16:36
  SPEAKER_00: Early tests may improve as the patient becomes familiar with the procedure.
• 16:40
  SPEAKER_00: Use the same instrument, test pattern, stimulus size, and threshold strategy so that changes are not caused by switching methods.
• 16:48
  SPEAKER_00: Use a six-month schedule when a single default is needed.
• 16:52
  SPEAKER_00: For many patients with established glaucoma, two high-quality visuals per year is a reasonable compromise between detection speed and burden.
• 17:01
  SPEAKER_00: The evidence suggests that this captures much of the benefit of more frequent testing without requiring three or more tests every year for everyone.
• 17:10
  SPEAKER_00: Use three tests per year selectively.
• 17:13
  SPEAKER_00: Consider approximately four-monthly testing during the first two years after diagnosis in advanced disease when the intraocular pressure is above target, after a treatment change, when the fellow eye has progressed quickly, or when test variability is high.
• 17:28
  SPEAKER_00: Do not cluster every test.
• 17:31
  SPEAKER_00: If the goal is to estimate a yearly slope, tests should be distributed across the year.
• 17:36
  SPEAKER_00: A schedule such as approximately 0, 4, and 8 months, or 4, 8, and 12 months provides better temporal coverage than placing all three tests close together.
• 17:47
  SPEAKER_00: A repeated test during the same visit can still be valuable for confirming an unexpected result or improving baseline reliability, but it should not be assumed to provide the same statistical information as a test separated by several months.
• 18:02
  SPEAKER_00: Review event and trend information together.
• 18:05
  SPEAKER_00: A new pointwise event may be important even when mean deviation remains stable.
• 18:10
  SPEAKER_00: Conversely, a worsening mean deviation slope may represent diffuse change, cataract, or another non-glaucomatous factor rather than focal glaucoma progression.
• 18:20
  SPEAKER_00: The most reliable interpretation combines the raw visual field plots, event-based progression analysis, mean deviation trend, pointwise or regional slopes, optic nerve examination and photographs, optical coherence tomography, intraocular pressure and treatment history.
• 18:38
  SPEAKER_00: Confirm unexpected progression.
• 18:40
  SPEAKER_00: A single poor visual field should rarely be treated as definitive evidence of irreversible glaucoma progression.
• 18:46
  SPEAKER_00: Confirmation is especially important when the result is inconsistent with the optic nerve, optical coherence tomography, prior fields, or the patient's clinical history.
• 18:57
  SPEAKER_00: The danger is two-sided.
• 18:59
  SPEAKER_00: Testing too infrequently delays treatment, while reacting to every isolated statistical alert can lead to unnecessary treatment changes and anxiety.
• 19:07
  SPEAKER_00: Conclusion: more visual field data usually reveal progression more clearly, but the benefit has limits.
• 19:14
  SPEAKER_00: The greatest gain commonly comes from moving from annual to six-monthly testing.
• 19:19
  SPEAKER_00: Three tests per year can provide additional sensitivity, especially for newly diagnosed or high-risk patients, and for point-wise slope analysis, but the improvement over two tests per year is smaller.
• 19:30
  SPEAKER_00: For many patients, the most efficient strategy is establish two reliable baseline fields.
• 19:37
  SPEAKER_00: Use approximately six-monthly testing for routine glaucoma monitoring.
• 19:41
  SPEAKER_00: Use approximately four-monthly testing during the first two years or when rapid progression is a concern.
• 19:48
  SPEAKER_00: Space tests across the year rather than clustering them unnecessarily.
• 19:52
  SPEAKER_00: Use event-based and trend-based analyses together.
• 19:55
  SPEAKER_00: Confirm suspicious findings before making major decisions.
• 19:59
  SPEAKER_00: Reduce or increase frequency according to the measured rate of progression, disease stage, life expectancy, and test quality.
• 20:07
  SPEAKER_00: The goal is not simply more data, it is better timed, reliable data interpreted with the right statistical method.
• 20:14
  SPEAKER_00: All links to sources are available in the text version of this article.
• 20:18
  SPEAKER_00: You can find the full article at visualfieldtest.com.
• 20:21
  SPEAKER_00: Thanks for listening.
• 20:23
  SPEAKER_00: To check your visual field, click the link at the bottom of this article or visit visualfieldtest.com.