Visual Field Printout Interpretation (2016) PDF

**Compiled by** **For Family Of Optometric Mentors** **July 13, 2016** **[Introduction]** Visual field testing is one of the most diagnostic procedures for pathological evaluations of the eye, especially retinal condition where visual field function needs to be measured. Evaluating visual field...

**Compiled by** **For Family Of Optometric Mentors** **July 13, 2016** **[Introduction]** Visual field testing is one of the most diagnostic procedures for pathological evaluations of the eye, especially retinal condition where visual field function needs to be measured. Evaluating visual field printout of modern day perimeters can be very daunting and confusing at times, especially when we want to cohesively link all the data together. Understanding visual fields is not black and white as most eye-care practitioners believed. It is not even shades of gray. But analyses can provide powerful information, if you can interpret them **Today, we are here to gain more knowledge and broaden our interpretation of visual field test. Knowledge they say is power. But in optometry, knowledge, to me, is sight.** **With this brief intro, I welcome you all to this ~2016\ Preconference/AGM\ FOM\ Workshop\ of\ the\ Nigerian\ Optometric\ Association~**  **APOSTILBS AND DECIBELS** **In perimetry, the luminance of test targets is measured in apostilbs. An apostilb is an absolute unit of luminance. The decibel scale is a relative scale created by the manufacturers of automated perimeters to measure the sensitivity of the island of vision.** **A Decibel is an inverted logarithmic scale and it is not standardized because the maximal luminance varies between instruments. A zero decibel (0 dB) is the brightest stimulus on all perimeters while the dimmest is 40dB on octopus and 50dB on Humphrey.** **How to read Visual Field report** [The **WANDER** scheme] To gain full knowledge and understanding of visual field printout interpretation, especially, Humphrey's field printout, a scheme has been developed. **This is called WANDER.** This scheme will provide a syst ematic approach to the interpretation of visual field report. WANDER Means: 1. **[WANDER \-\-\-\-\-\-\-\-\-- WHAT WAS DONE?]** **First of all, Check the test area and strategy used on the printout.** A. **The Test Area Used**. Is it? i. 60 degrees ii. 30 degrees iii. 24 degrees iv. 10 degrees? B. **The Strategy Used**- is it ? a. Full Threshold strategy b. Screening strategy c. Fast test strategy. i.e. -SITA FAST (Humphrey) -Top ( Octopus). **1.** **TEST AREA** **Central 30 and 24 degrees test** What is the difference between the 30 and 24 degrees test? Both are almost identical except at the peripheral ring. The distance between test point locations is 6 degrees. In 24 degrees tests, some peripheral rings tested in 30 degrees are omitted except the 2 rings at the nasal. These 2 rings are included in the test because glaucoma is known to affect this part. 30 degrees test is made up of 76 rings while 24 degrees test is made up of 54 rings. This gives a shorter time test in 24 degrees pattern. **Central 10 degrees:-** The distance between rings is 2 degrees (that is 2 degrees spacing),this gives better information while testing for central vision. Example: macula problem or in advance glaucoma. Central 10 degrees help to test so many close locations at central region and it therefore gives better resolution with better information. It is used only to investigate macular lesion or advance glaucoma.  **24 and 10 degrees Plot**  2. **STRATEGY :** - Full Threshold strategy (Also known as Standard Algorithm or FASTPAC) - FAST Threshold Strategy --e.g. SITA / TOP - Screening -- 2 zone screening or 3 zone screening. - SWAP - Flicker test/strategy A. **[FULL THRESHOLD STATEGY:]** In this strategy, 5 stimuli is presented in the same location. This mean one location is been stimulated 5 times. This demands much time to complete. A stair casing strategy known as the 4-2 db is used. This test is repetitive bracketing. It is most time consuming but most accurate and reproducible data. The differential light threshold is determined at every point in the visual field using a 4-2 staircase or bracketing algorithm. In the 4-2 algorithm, testing starts with either a suprathreshold (seen) or an infrathreshold (not seen) stimulus. For a suprathreshold stimulus, the intensity of the stimulus is decreased in 4-dB steps until the stimulus is no longer seen (threshold is crossed). The stimulus intensity is then increased in 2-dB steps until the threshold is crossed a second and the stimulus is seen again. The Humphrey perimeter uses the intensity of the last seen stimulus as threshold. B. **[FAST THRESHOLD STRATEGIES.]** They rely on models of visual fields (both normal and abnormal) i.e. , it assumes that at central field the vision is sensitive and so it will use low threshold or stimuli while at the periphery where vision is less sensitive, it will use high threshold or stimuli. In glaucoma, vision loss is expected in the arcuate area therefore, the computer begins by throwing low stimuli on a point at the Bjerrium area, if the patient misses it, the computer will assume the next area or point to this will be low and jump it.and on and on. This is based on assumption. It saves time doing this. SITA uses artificial intelligence type of programming and rely on guesses where the threshold is. Rapid Tendency Oriented Perimeter (TOP) in octopus is done within 2 -- 4 minutes **Swedish Interactive Threshold Algorithm** This new thresholding strategy is particularly useful because it decreases test time by about half. In a given time period, Swedish Interactive Threshold Algorithm (SITA)-Standard and SITA-Fast collect twice as much information as the Humphrey Full Threshold and the FastPac respectively. Testing of each location is started at a level that is near threshold, which shortens the time spent searching for the threshold. The time interval between responses is customized to each patient\'s reaction time. SITA calculates false-positive and false-negative catch trials from the threshold measurements, eliminating the need for separate testing of the false catch trials; this accounts for 6% of the decrease in test time in comparison to the full threshold strategy. SITA uses artificial intelligence and computer modeling, incorporating probability models of normal and glaucomatous visual fields to provide more efficient testing of the visual field. Testing is interactive, using each response from a patient to help predict future responses. Information incorporated in the interactive testing includes comparison to reference fields in normal and glaucomatous eyes, normal age-corrected threshold values, patterns of glaucomatous damage, and multiple frequency of seeing curves in normal and abnormal states. At the end of the test, the threshold is recalculated based on all the available data. The time interval for each response is analyzed and those responses that were likely false are discarded. The program estimates the threshold expected at each point on a continuous basis and stops testing when the estimated error is less than a predetermined value. The confidence limit is narrower for SITA standard than SITA fast, which is why SITA standard takes longer. The lower error in the SITA standard test decreases the variability of the examination and makes SITA standard more reliable than SITA fast for future comparisons **TYPES OF SITA** -: SITA STANDARD -: SITA FAST. [SITA STANDARD]: - The programmed computer will go on to test up to 90% of the points. If the assumption goes in the same pattern in these 90% points, then the remaining 10% points will not be tested and the computer will print it out as normal. 90% good points (Tested) / 10% good points (Assumed) Print out = 100% good 90% bad points (tested) / 10% bad points. (Assumed) Print out = 100% bad It has been found that SITA standard is comparable with the full threshold strategy. The advantage of SITA or TOP is that it is done in 4-6mins. Quite faster than the full threshold ( 20 mins) In full threshold test, patient can easily lose concentration. [SITA FAST]:- The computer does same thing but just up to 80% of the points. The rest 20% is assumed once thee 80% points go in same pattern. The top of the VF printout page contains key information about patient demographics and the type of test that was performed. Always review this portion for accuracy. On the Humphrey Field Analyzer, the best threshold test is the SITA-Standard. The standard test is better for early detection, while the SITA-Fast test tends to show variable results and is less sensitive.  - SITA Standard is most accurate, most commonly used strategy and it reduces testing duration by 50%. The test time is reduced by eliminating retest trials for short-time fluctuation determination and assessing False Positive (FP) and False negative (FN) responses. - SITA FAST reliability is worse than SITA Standard **TOP (Tendency Oriented Perimetry)** SITA is used in Humphrey while TOP is used as FAST strategy in the Octopus. TOP takes advantage of the fact that the sensitivity of the retina is interrelated rather than having an individual (or isolated) value. During the test every answer at a particular point is also taken into account in the adjustment of the neighbouring locations. It takes just about 2 minutes. It is a FAST strategy. **[C. SCREENING :]** Screening tests can quickly identify abnormal visual fields and provide information about the location of defects. Multiple-level tests also provide some data about the depth of defects. Shallow, subtle defects and early generalized depression may be missed by screening tests. Here we present very strong and same intensity stimulus / threshold all over the field. The patient answers **seen** or **not seen.**  If the patient sees it he gets the **+** or **0** mark. If the patient doesn't see it he gets the C:\\Program Files\\Microsoft Office\\MEDIA\\OFFICE14\\Bullets\\BD15133\_.gif mark. Actually threshold cannot be determined so we can only use symbol. Sometimes, you ask the program to retest the blind area again with another threshold. This will differentiate the mildly depressed and total depressed zone and the normal. Here we get 3 zones **+**  C:\\Program Files\\Microsoft Office\\MEDIA\\OFFICE14\\Bullets\\BD15133\_.gif Screening as the name implies only detect rather large changes (greater than 4-5db below normal). It can detect early glaucomatous defects. Screening is quite faster than full threshold test. A positive screening test must be followed by quantitative test. **Types of Screening Programmes** a. **Single Level Suprathreshold Test** A stimulus that is 2 to 6 db brighter (suprathreshold) than the expected hill of vision is used to test multiple locations in the visual field. Results are recorded simply as seen (normal) or not seen (defect). On the Humphrey perimeter, this is called the **threshold-related strategy**. b. **Two-Level Suprathreshold Test** These tests often are referred to as three-zone tests because the visual field is classified into three categories: normal, relative defect, and absolute defect. As in the single-level test, testing is performed initially with a mildly suprathreshold stimuli approximately 2 to 6 dB brighter than the expected threshold. Spots that are seen recorded as normal. If a spot is not seen, the brightest stimulus available for the apparatus is presented. If the brightest target is seen, a relative defect is recorded. If the brightest target is not seen, an absolute defect is recorded. Two level testing is a qualitative rather than quantitative screening test. The results give only a rough indication of the status of the visual field in terms of **"normal", "relative" or "absolute**" defect. [**D. Short-Wavelength Automated Perimetry** ] Short-wavelength automated perimetry (SWAP) is a static threshold perimetry test in which a blue stimulus (440 nm) is presented on a background of yellow illumination. The yellow background desensitizes the green and red cones, whereas the blue stimulus activates the blue cones. Overall, the blue cones and their ganglion cell connections are tested. SWAP detected glaucomatous field defects at a significantly earlier time than white-on-white perimetry and revealed a faster rate of progression. One concern is that the variability between testing sessions is greater using SWAP. It is unclear whether the success of SWAP in detecting early defects relates to identifying preferential damage to the blue/yellow cone system, or whether the testing of only a subset of the visual system enables earlier detection even if the damage is not selective. SWAP testing takes 15% longer than full threshold testing. The blue cone system is slower and patients report that the test seems different. Even experienced field takers may not do well on their first SWAP test and may exhibit a learning effect between the first and second tests. The test is greatly affected by cataract. A size V stimulus is required The gray scale is not useful in interpreting SWAP visual fields; SWAPac on the Humphrey is required to correctly interpret the data. [**E. Frequency Doubling Technology** ] Frequency doubling technology (FDT) tests the magnocellular pathway. These large diameter fibers make up about 3% to 5% of retinal ganglion cells. Full threshold FDT tests can be completed in less than 6 minutes per eye, and suprathreshold screening can be completed within 1 minute. Results are significantly correlated to testing done using the HFA In FDT perimetry, 17 regions are tested within the central 20 degrees of the visual field. Each stimulus is a series of black and white bands that flicker at 25 Hz. A normal eye perceives the illusion of twice the number of bands more closely spaced. Glaucomatous eyes have diminished contrast sensitivity as a result of preferential damage to the My cells and they thus require higher contrast to detect the frequency doubling illusion. FDT has been found to have up to 97% sensitivity and specificity for detecting glaucomatous defects **2. (WANDER )\-\-\-\-\-\-\-- ACCURACY** This will help check whether the test is reliable or not. In the print-out, check the reliability indices. Reliability indices used include: A. Fixation Loss( FL). B. False Positive(FP). C. False Negative( FN). D. Short Term Fluctuation. Any of these 3indices (A-C) should be less than 1/3 ( \< 33% ) and (D) should be less than ¼ ( \< 25% ). A. **FIXATION LOSS:-** In the beginning of the test, check the fixation point and know whether it is the OD/OS. Then the blind spot location is known. The blind spot Is located 12 degrees away from the point of fixation. Measure 5 degrees x7 degrees. During the test now and then programmer will throw stimuli at the location of the blind spot. The patient should not see it. If the patient answer seeing it then the eye has been moved. This is repeated several times. Example : if Blind-spot stimuli is repeated 20 times and patient reports seeing it 3 times. The FL will be printed out as 3/20 or 3-20. For reliability, FL should be less than 33% of the number. Fixation loss check is not accurate in enlarged blind spot, because even when the patient moves his eye, he will not still see the stimulus due to enlarged blind spot. So, FL is the number of times a patient respond to a target placed in the blind spot. B. **FALSE POSITIVE** -: Visual field uses audible voice while presenting stimuli. The patient may learn to respond to this audible voice rather than the visual stimuli. To check reliability in response, the machine sometimes sends audible sound without stimulus. If the patient responds to this audible voice, we call this FALSE RESPONSE OR FALSE POSITIVE. So FP is the number of times a patient responds to the audible click of the perimeter when no target/stimulus is presented. In static Perimetry, repeated threshold measurements at a single location vary and cause fluctuation of threshold responses. A fluctuation of measured thresholds within a visual field examination is called short-term fluctuation. A fluctuation of measured thresholds between examinations is called long-term fluctuation. Short-term fluctuation is calculated by the Humphrey and Octopus thresholding programs. It is calculated from the variance of multiple readings performed at selected locations in the visual field. In a normal visual field, short-term fluctuation is between 1 and 2 dB; fluctuations greater than 2 dB may indicate poor reliability. 3. **WANDER: NORMAL OR ABNORMAL** The next question is...... Is the field normal or abnormal? The thing we should look out for is the Gray scale and the numerical values. **[The gray scale ]** This is otherwise known as the half tone. The gray scale gives us a reasonable impression about the field but we should not depend on it. It is a scale we can use to explain something to the patient but we should not depend on it. **Why is the gray scale not dependable**? The reason is simple. In visual field test, the machine only tests 76, or 54 or 68 points depending on the test area used. But the computer in its printout presents over 2000 symbolic representation. It means it fills spaces between the actual tested points. In full threshold test (76 points), when a computer test a single point, it will assume the all other points within 6 degrees circumference to the tested point are equal to the tested point. So the computer scores those points with same decibels and move on. The computer uses a symbol to fill in the space (see below). This is not completely accurate. This is why the gray scale should not be completely relied upon. It is good for first impression. This is not sufficient for following field over time. **[Numerical values]** These are numbers that represent the sensitivity of the retina. **[Total Deviation]** Normally, the sensitivity of the retina varies with age. Before we start the test, we must input the age of the patient. It is known that the sensitivity of the retinal decay by decades. That is, the visual field thresholds decline with age at a rate of 0.5 -- 1.0 dB per decade. The computer always compare the sensitivity of a patient tested with the normal for his age. For example: 1. If the sensitivity of a patient's retinal point is 26dB and the normal for his age at this same point is supposed to be 30dB. Then the difference is -4dB. This is the total deviation. 2. If the sensitivity of a patient's retinal point is 26dB and the normal for his age at this same point is supposed to be 24dB. Then the difference is +2dB. This is also the total deviation. Example 2 **[PATTERN DEVIATION: - ]** To understand this we need an example. **Section A Students (%) Section b students (%)** 95 20 94 85% location 19 92 18 90 18 90 17 88 17 86 5 85 3 84 2 Example: - Suppose in an examination of a group of students and the results of this group are quite high (as arranged in group A). Then after 2 weeks, we get another group of students and we give them an exam, but due to the difficulty, the result for this group was quite low.( as in group B). Now, let's say the teachers realized that it was their mistake to have made the exam difficult for the second group and they decided to improve the result of group B by raising their marks to make them pass. They decided to create a system. This same system, they agreed, if they have this same situation in future, they can apply it. Now in this system, they agreed to arrange the student's marks from Highest to Lowest (both group A and B). After this arrangement, they decided to pick the 85% location, to see the difference between the two groups (A and B). In table above, at 85% position or location, the best in group A is 94% and the Bad group B is 19%. Now we find the difference between this location which is 85 %( i.e. 94-19 =75). This value of 75 will be used to raise the marks of the bad results of group B. thus as follows. **TABLE 2; (improved results)** **Section A Students (%) Section B Students (%)** 95 95 (20+75) 94 94 (19+75) 92 93 (18+75) 90 93 (18+75) 90 92 (17+75) 88 92 (17+75) 86 80 (5+75) 85 78 (3+75) 84 77 (2+75) This is an assumption. It is an adjusted value to make the bad students pass the exam. Any student who could not pass after this adjustment is regarded as very very poor student. This poor student has deviated from the normal. This is what applies in pattern deviation in visual field. In the Visual Field machine, threshold patterns have been created for normal range within age range population. This is known as standard threshold. It is expected every normal eye with normal visual filed (in an age population) should exhibit this standard. If this is not so, such individual has deviated from that normal. (Total deviation). In the table below, the patient Visual Field sensitivity as tested is shown to the right while the computer standard threshold for age group of patient stored in the memory is shown on he left. **Computer Standard Threshold(dB) Patient Threshold (dB)** 26 22 26 22 25 85% location 22 (25 -- 22 = 3dB) 24 21 24 21 22 18 22 18 20 16 18 14 16 14 To get the pattern deviation of this patient, the computer takes the 85% position on the standard and compares it to the 85% position of the patent's threshold. (I.e. 25-22 =3). The difference is 3db. So the computer program will add +3 to all the patient thresholds. The result is the adjusted values. That is the computer raised the value. See table below. EXAMPLE TABLE:- **Computer Standard Threshold(dB) Adjusted Patient Threshold (dB)** 26 25 (22+3) 26 25 (22+3) 25 85% location 25 (22+3) (25 -- 22 = 3dB) 24 24 (21+3) 24 24 22 21 22 21 20 19 18 17 16 17 Now, after raising these values to get the adjusted threshold, the computer again compares these adjusted values to the normal values expected of the age group of the patient. Difference is now regarded as pattern deviation. Then the probability plot of this new pattern will be drawn. This plot is called Pattern Deviation Probability plot (PDP) PATTERN DEVIATION: - is derived from the Total deviation via adjustment of the measure thresholds upward or downwards by an amount which reflects any generalized change in the threshold of the least damaged portion. PATTERN DEVIATION therefore, is the difference between the adjusted threshold of each individual test location and the age-corrected normal value for that location. **Computer pattern deviation table** +-----------------+-----------------+-----------------+-----------------+ | **Stored | **Numerical | **Difference at | **Pattern | | standard for | value of | 85% threshold | Deviation** | | age** | patient** | is -1dB** | | | | | | (Adjusted | | | | **(Adjusted | patient | | | | patient | threshold minus | | | | threshold)** | Computer stored | | | | | standard for | | | | | age) | +=================+=================+=================+=================+ | 37 | 38 | 37 (38 + (-1) = | 0 | | | | 37 | | +-----------------+-----------------+-----------------+-----------------+ | 37 | 38 | 37 | 0 | +-----------------+-----------------+-----------------+-----------------+ | 37 | 38 | 37 | 0 | +-----------------+-----------------+-----------------+-----------------+ | 37 | 38 | 37 | 0 | +-----------------+-----------------+-----------------+-----------------+ | 37 | 38 | 37 | 0 | +-----------------+-----------------+-----------------+-----------------+ | 37 | 38 (37 -- 38) = | 37 | 0 | | | -1 | | | +-----------------+-----------------+-----------------+-----------------+ | 36 | 36 | 35 | -1 | +-----------------+-----------------+-----------------+-----------------+ | 36 | 36 | 35 | -1 | +-----------------+-----------------+-----------------+-----------------+ | 36 | 36 | 35 | -1 | +-----------------+-----------------+-----------------+-----------------+ | 36 | 36 | 35 | -1 | +-----------------+-----------------+-----------------+-----------------+ | 36 | 35 | 34 | -2 | +-----------------+-----------------+-----------------+-----------------+ | 36 | 35 | 34 | -2 | +-----------------+-----------------+-----------------+-----------------+ | 30 | 32 | 31 | -2 | +-----------------+-----------------+-----------------+-----------------+ | 30 | 32 | 31 | +1 | +-----------------+-----------------+-----------------+-----------------+ | 30 | 32 | 31 | +1 | +-----------------+-----------------+-----------------+-----------------+ | 30 | 32 | 31 | +1 | +-----------------+-----------------+-----------------+-----------------+ | 30 | 29 | 28 | -2 | +-----------------+-----------------+-----------------+-----------------+ | 30 | 28 | 27 | -3 | +-----------------+-----------------+-----------------+-----------------+ | 30 | 28 | 27 | -3 | +-----------------+-----------------+-----------------+-----------------+ | 30 | 28 | 27 | -3 | +-----------------+-----------------+-----------------+-----------------+ | 30 | 27 | 26 | -4 | +-----------------+-----------------+-----------------+-----------------+ | 30 | 27 | 26 | -4 | +-----------------+-----------------+-----------------+-----------------+ | 28 | 27 | 26 | -2 | +-----------------+-----------------+-----------------+-----------------+ | 28 | 27 | 26 | -2 | +-----------------+-----------------+-----------------+-----------------+ | 28 | 26 | 25 | -3 | +-----------------+-----------------+-----------------+-----------------+ | 28 | 26 | 25 | -3 | +-----------------+-----------------+-----------------+-----------------+ | 28 | 25 | 24 | -4 | +-----------------+-----------------+-----------------+-----------------+ | 28 | 24 | 23 | -5 | +-----------------+-----------------+-----------------+-----------------+ | | | | | +-----------------+-----------------+-----------------+-----------------+ | **Dr. Felix | | | | | Olafisoye | | | | | model** | | | | +-----------------+-----------------+-----------------+-----------------+ **[GLOBAL INDICES:]** To help or aid the clinician in interpreting the numerical data generated by threshold test, field indices have been developed by perimeter manufactures. This is called the GLOBAL INDICES. These include:- 1. Mean Deviation (MD). 2. Pattern Standard Deviation (PSD) 3. Corrected Pattern Standard deviation (CPSD) 4. Short Term Fluctuation (SF). Group A (Normal height) 150 160 165 175 180 ------------------------- ----- ----- ----- ----- ----- Group B (Short height) 140 155 160 165 175 Group A (Normal height) 150 160 165 175 180 ------------------------- -------- ------- ------- -------- ------- Group B (Short height) 140 155 160 165 175 **Deviation** **10** **5** **5** **10** **5** 0 - 6 Mild Generalized Depression -------- --------------------------------- 6 - 12 Moderate Generalized depression \> 12 Severe generalized depression **PATTERN STANDARD DEVIATION** Normally the pattern standard deviation should be less than 4 in the normal field. Remember that the mean deviation gives us the normal impression on the HEIGHT of the field while the pattern standard deviation gives us impression of the SHAPE of the field. **HEIGHT OF FIELD** **SHAPE OF FIELD** Check the table below, what impression do you get? **MD** **PSD** **IMPRESSION (Visual field possibility)** ---------- ---------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------- Normal Normal Normal field Abnormal Normal The whole field is depressed homogenously. Diffuse depression or generalized depression. Normal Abnormal The whole field is high generally but there is localized depression. One point is defective or depressed. A small purely localized defect or artifact present. Abnormal Abnormal The whole field is depressed and there are many areas more depressed than other. It means a large defect is present with a significant localized defect. **GLAUCOMA HEMIFIELD TEST (GHT):-** It is the mirror image analysis of each of 5 pairs of zones. It is designated only for glaucoma. GHT is at least as accurate as other methods for the classification of single visual fields. 1 outside normal limits. 2 borderlines 3 Generalized reduction in sensitivity 4 Abnormally high sensitivity 5 Within normal. Note: don't rely much on GHT. It is just the computer's comparison of upper field with lower field (in values). **WANDER: DEFECT PATTERN** The next is to decide whether the Pattern of the defect. Here we try to find out whether the pattern of the field goes with any particular disease. 1. Is it a neurological defect? 2. Is it a retinal defect? E.g. in glaucoma Note that neurological defect respect the vertical meridian while glaucoma defects respects the horizontal meridian. **GLAUCOMA VF DEFECTS:** 1. Paracentral Scotoma -- An island of defect in the central 10 degree 2. Arcuate Scotoma- It occurs 10 -- 20 within the arcuate bundle. 3. Nasal Step- An affection close to the horizontal meridian and affects more of the upper than the lower or the reverse. This is discontinuity or depression along the horizontal raphe. It may combine with paracentral or Bjerium. 4. Altitudinal Defect -- when a defect affects all the upper field only or lower field only. That is, near complete loss of the one hemisphere visual field 5. Temporal Island /wedge: A small visual field defect that is temporal to the blind spot. 6. Generalized depression ----------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- **Mild Severe** **Nasal step**  Limited field loss adjacent to the nasal horizontal meridian with at least one abnormal point (p \< 5%) at or outside 15 degrees on the meridian. Cannot include more than two significant points (on either plot) in the nerve fiber bundle region on the temporal side. Partial Arcuate Visual field loss in the nerve fiber bundle region that extends incompletely from the blind spot to the nasal meridian. The defect is generally contiguous with either the blind spot or the nasal meridian and must include at least one abnormal location in the temporal visual field. Arcuate  Significant visual field loss in the nerve fiber bundle region, extending across contiguous abnormal points from the blind spot to at least one point outside 15 degrees adjacent to the nasal meridian. Paracentra A relatively small visual field abnormality (a cluster or a single point) in the nerve fiber bundle region that is generally not contiguous with the blind spot or the nasal meridian. In particular, it does not involve points outside 15 degrees that are adjacent to the nasal meridian. Temporal Wedge  A small visual field defect that is temporal to the blind spot. ----------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- **WANDER: EVALUATE** After understanding the defect pattern, the next thing is to evaluate the disease. Is there a field defect? Is it due to glaucoma or neurology? Or is it cataract or other artefact? Can you accept the test result as valid? **WANDER REFLECT** Do you need to repeat examination? Reflect on the test done. Then interpret. **Never make a diagnosis based on the visual field alone. Always correlate with clinical findings.** This topic will cover how to use the optic disc and the visual field changes to determine glaucoma damage. This is important when you are using a target IOP for your patient. Now, the very big question is: Should we depend on Optic disc or Visual field or both? I will explain this using the 3 suggested systems by scholars. You can use one of them in your practice. 1. **[It postulated we look at the MEAN DEVIATION (MD). ]** MD (0 -- 6) = MILD GLAUCOMA MD (6 -- 12) = MODERATE GLAUCOMA MD \> 12 = SEVERE GLAUCOMA 2. **[It postulated we look at the PATTERN DEVIATION (PSD) ]** We use the probability 5% and the 1%. (i.e. \ a. If the probability \ 3. It also postulated we look at the central 5 degree of fixation to check for sensitivity of the retina. a. If you find \< 15dB point in the central 10 degrees either in the upper or lower hemisphere, this is MODERATE glaucoma. b. But If within central 10 degrees, you find one point lower than 15dB in the upper hemisphere and another point lower than 15dB in the lower hemisphere. This is SEVERE glaucoma. c. If you find just one point in the central 10 degrees with sensitivity 0dB. Then it also SEVERE glaucoma 4. We can also use DDLS to determine glaucoma (Disc Damage Likelihood scale) +-----------------------------------+-----------------------------------+ | **EARLY GLAUCOMA** | **Early field loss** | | | | | | **CD less than 0.7** | +===================================+===================================+ | | | +-----------------------------------+-----------------------------------+ | **MODERATE GLAUCOMA** | **Significant visual field loss | | | not within the central 10°.** | | | | | | **CD 0.7 -- 0.85** | +-----------------------------------+-----------------------------------+ | | | +-----------------------------------+-----------------------------------+ | **SEVERE GLAUCOMA** | **Visual field loss within | | | central 10°.** | | | | | | **CD more than 0.85** | +-----------------------------------+-----------------------------------+ **Proposed system 3: The American Guidelines** This considers change in optic disc with visual field. **[Optic disc anomalies considered with:]** ----------------------- ---------------------------------------------------------------------------------------------------- **EARLY GLAUCOMA** **Glaucoma normal W/W field of vision but with Optic disc abnormality.** **MODERATE GLAUCOMA** **Optic disc abnormality + field abnormalities in one hemisphere but not within the central 10°.** **SEVERE GLAUCOMA** **Optic disc abnormality + field abnormalities in both hemispheres or within the central 10°.** **(W/W = white on white)** **[Appendix]**    This note is written by Dr Felix Olafisoye in a simplified language for easy understanding. My deep appreciation goes to Dr. Elsie Nwosu for typing out this manuscript.