Practice
The Importance of Visual Field Testing in Idiopathic Intracranial Hypertension Michael Wall, MD, FAAN
ABSTRACT Idiopathic intracranial hypertension (IIH) is a disease of unknown cause typically affecting obese women in the childbearing years. Although headache is the most common symptom, the major morbidity of IIH is visual loss, with 5% to 10% of patients progressing to blindness. While about 95% of patients with IIH have visual loss documented by perimetry, only about one-third notice their visual loss because most loss occurs in the peripheral visual field. Since treatment decisions in IIH are made primarily by changes in visual field function, serial perimetry is the most critical test to obtain when following patients with IIH. This article describes the role of visual field testing in the monitoring of IIH patients in clinical practice, including its importance in communication among providers.
Address correspondence to Dr Michael Wall, University of Iowa, College of Medicine, Departments of Neurology and Ophthalmology, Iowa City Veterans Affairs Medical Center, Iowa City, IA 52242, [email protected]. Relationship Disclosure: Dr Wall’s institution receives a grant from the NIH. Unlabeled Use of Products/Investigational Use Disclosure: Dr Wall discusses the unlabeled use of acetazolamide in the treatment of idiopathic intracranial hypertension. * 2014, American Academy of Neurology.
Continuum (Minneap Minn) 2014;20(4):1067–1074.
Case A 20-year-old obese but otherwise healthy woman presented to a neurologist with a 2-month history of daily, constant, throbbing headaches and pulse synchronous tinnitus. She denied visual loss or history of tetracycline use, and she had no constitutional symptoms. On examination, she had bilateral papilledema (Practice Figure 1). Visual acuity was 20/20 in both eyes, confrontation visual field examination was normal, eye movements were full, and the remainder of her neurologic examination was normal. MRI showed an empty sella and flattened globes. Lumbar puncture revealed an opening pressure of 310 mm water with normal CSF constituents.
PRACTICE FIGURE 1
Ocular fundus examination (A, right eye; B, left eye) of the patient described in this case, a 20-year-old woman with idiopathic intracranial hypertension. Bilateral papilledema is present.
Continuum (Minneap Minn) 2014;20(4):1067–1074
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
1067
Visual Field Testing in IIH DISCUSSION It is common for neurologists to start treatment at this point, usually with acetazolamide along with counseling about a low-sodium weight-reduction diet. Practice Figure 2, however, shows a visual field example from a patient who was followed by a neurologist for 1 year with frequently documented normal visual acuities. It was not until the patient reported visual loss that this visual field examination was obtained. Perimetry shows severe visual field constriction in both eyes despite 20/25 visual acuity. Therefore, neither visual acuity nor the patient’s symptoms are reliable indicators of the presence of papilledema-related visual loss. It is important for the neurologist to know how the visual field is damaged in idiopathic intracranial hypertension (IIH). A variety of mechanisms produce visual field abnormalities. The major mechanism is nerve fiber bundle damage from intraneuronal ischemia due to compression from axoplasmic flow stasis. The arcuate bundles are most vulnerable, and glaucomatouslike visual loss ensues. Other less common mechanisms are globe flatteningYinduced hyperopia with or without choroidal folds and central visual field loss from a neurosensory detachment from fluid extending from the optic nerve head into the macula. Finally, the visual field examination itself can, at times, be difficult to interpret and can be the source of confusion.
PRACTICE FIGURE 2
1068
An example of severe visual field constriction in a different patient with idiopathic intracranial hypertension whose follow-up included confrontation fields and visual acuity testing. Severe visual field constriction has occurred.
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
August 2014
Case Continued Consultation with a neuro-ophthalmologist was obtained, and baseline and serial perimetry were performed to monitor for changes over time. Practice Figure 3 shows this patient’s baseline automated perimetry examination. (Practice Figure 4 is a normal perimetric result for comparison.)
PRACTICE FIGURE 3
Standard automated perimetry of the patient described in this case. The left eye is on the left side of the figure, and the right eye is on the right side of the figure. Generalized loss is present, especially in the inferonasal fields and areas around the blind spot.
Continued on page 1070 Continuum (Minneap Minn) 2014;20(4):1067–1074
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
1069
Visual Field Testing in IIH
Continued from page 1069
PRACTICE FIGURE 4
Standard automated perimetry of the right eye of a different patient that is within normal limits.
VISUAL FIELD TESTING A discussion of perimetry and the interpretation of the visual field examination follows. Two types of visual field testing are available: manual perimetry and automated perimetry.
1070
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
August 2014
Manual Perimetry Manual perimetry is most commonly performed using the Goldmann bowl perimeter. Screening for defects should be performed with the I-4-e, I-2-e, and I-1-e isopters. Practice Figure 2 is an example of perimetry performed using a Goldmann bowl. The advantages of manual perimetry mostly revolve around the fact that it is conducted by a technician (known as a perimetrist). These advantages include patient interaction with the perimetrist (important for subjects with attention difficulties and fatigue); custom test point locations, which refers to the fact that the test is done by hand and the test locations are chosen by the perimetrist (as opposed to standard automated perimetry where test locations are fixed on a 6-degree spaced grid); and improvisation of testing strategies based on concurrent findings, which provide more accurate mapping of defect shape. However, manual perimetry is less sensitive than standard automated perimetry. Its most severe limitation is that few perimetrists are adequately trained.1 Automated Perimetry Standard automated perimetry presents a small fixed-sized stimulus on a 6-degree spaced grid within the central 21 to 27 degrees of the visual field. The test continues until the dimmest light at each of the preselected test locations is found. The computer processes the data, and summary statistics are calculated. Subjects may find standard automated perimetry to be boring and have difficulty maintaining attention. Clues to poor perimetry performance are excessive false-positive and false-negative catch trials. False-positive trials occur when no stimulus is shown and subjects press the response button as if they saw a stimulus, or when they respond in a time window that is not physiologically possible. False-negative responses are very important to note and are tabulated as follows: The test software projects substantially brighter stimuli in an area where a subject previously responded to having seen a dimmer stimulus, and if the subject misses the stimulus, the trial is counted as a false-negative response. If the number of false-negative trials occurring in a session is more than 15%, the subject may no longer be paying attention to the test, and the results should be ignored or discounted. Automated perimetry is also susceptible to artifacts or areas of visual loss due to external factors such as malpositioned corrective lenses that cause the rim of the lens to block stimuli. Eyelid ptosis or tilting the head forward can cause obstruction to viewing the upper part of the visual field with resultant visual field defects. Refractive scotoma, visual field defects due to lack of appropriate refraction, can also occur. Contracted Visual Field Various cognitive factors and interactions with the perimetrist can cause a contracted visual field, which can occur with either manual or automated perimetry. These include improper testing instructions, inability to understand the test, lack of motivation, poor attention span, and distractions such as headache. These factors need to be identified since the end-stage visual field in IIH has a similar contracted pattern (Practice Figure 52). Continuum (Minneap Minn) 2014;20(4):1067–1074
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
1071
Visual Field Testing in IIH
PRACTICE FIGURE 5
Grades of visual loss in idiopathic intracranial hypertension, from mild to severe. Reprinted with permission from Wall M, Kugler Publications.2 B 1991 Imaging and Perimetry Society.
Case Continued Results of the patient’s baseline automated perimetry examination showed no evidence of artifacts, and the false-negative and false-positive catch trials were in an acceptable range. The lower left of the total deviation probability map printout showed many test locations were flagged as abnormal (the test point falls outside the P=.05 level of an age-matched control’s test point).
DISCUSSION CONTINUED Visual field loss occurs in almost all cases of IIH. In a prospective study of IIH, visual loss in at least one eye (other than enlargement of the physiologic blind spot) was found in 96% of patients with Goldmann perimetry using a disease-specific strategy, and in 92% of patients with automated perimetry.3,4 About one-third of this visual loss is mild and unlikely to be noticed by the patient, but it serves as a marker with which to guide therapy.4 Most patients with IIH have visual loss, and the standard of care is to obtain perimetry to monitor this loss. The earliest visual field defect in IIH, other than an enlarged blind spot, is often an inferior nasal step defect followed by peripheral nasal loss. Arcuate defects, nerve fiber bundle defects that arc around the central 10 degrees, may appear next, followed by a gradual depression of the entire field, most pronounced peripherally. The stages of visual loss are shown in Practice Figure 5.2 The most common defects in IIH are enlargement of the physiologic blind spot and loss of inferonasal portions of the visual field along with constriction of isopters. Constriction of isopters is a pattern of contraction of the threshold to a moving stimulus due to a generalized
1072
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
August 2014
reduction in visual sensitivity. Central defects are distinctly uncommon and warrant a search for another diagnosis unless a large serous retinal detachment from high-grade optic disc edema is present and spreading toward the macula. The loss of visual field may be progressive and severe, leading to blindness in about 5% of cases. The time course of visual loss is usually gradual; however, acute severe visual loss can occur. Blind spot enlargement is ubiquitous in IIH. Since refraction often eliminates this defect,5 blind spot enlargement should not be considered significant visual loss unless it encroaches on fixation. Also, since blind spot size is dependent on refraction, it should not be used to follow the course of therapy. With treatment, significant perimetric improvement occurs in about 50% of patients.4 A study that evaluated a subgroup of patients with worsening of their vision showed recent weight gain was the only factor significantly associated with decline in vision.4 Other groups at risk for severe visual loss are black men, patients with glaucoma, and patients who are rapidly tapering off corticosteroids. The course of IIH is often chronic with recurrences especially during periods of weight gain.6 Pitfalls to Avoid Corbett and Thompson have pointed out that many physicians follow patients with IIH with the wrong tests.7 Snellen acuity and visual evoked potentials are insensitive methods to detect the visual loss of IIH. Repeated measurements of CSF pressure can be misleading as CSF pressure fluctuates throughout the day and does not correlate well with the clinical state. Papilledema as measured by the Frise´n scale, ocular fundus photography, or optical coherence tomography are much better surrogates for average CSF pressure. Patients with IIH should be followed with perimetry and serial stereo fundus photos or optic disc grading using ´n scale.8 Automated perimetry is used for attentive and motivated the Frise subjects; in others, manual perimetry gives more reproducible results. Automated perimetry such as that done by the Humphrey Field Analyzer or Octopus perimeter usually gives reproducible results in patients with minimal visual loss. Since variability increases logarithmically with increasing visual system damage, determining whether a visual field has changed can be very problematic.9,10 Most experts require a series of at least five visual field examinations in these patients to be confident of calling visual field change, and even in the case where multiple perimetric examinations are performed, it is wise to require confirmation of worsening with at least one additional examination. Pediatric Idiopathic Intracranial Hypertension Excellent reviews of IIH in children can be found.11Y13 Some interesting differences occur between IIH in the pediatric age group and adults. In IIH from childhood through puberty, the incidence in girls and boys is the same.14 Obesity does not appear important in the pathogenesis of IIH in prepubertal children. The reported etiologies limited to children are nutritional restoration after malnutrition and thyroid replacement therapy in hypothyroid children.15 The effect of papilledema on vision is the same in children as in adults. Formal perimetry can be performed in most children older than 6 years. SUMMARY IIH is characterized by elevated CSF pressure of unknown cause. It is predominantly a disease of obese women in the childbearing years. Diagnosis should adhere to the Continuum (Minneap Minn) 2014;20(4):1067–1074
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
1073
Visual Field Testing in IIH
Modified Dandy Criteria, and other causes of intracranial hypertension should be sought. Since loss of visual function is common in IIH and, if left untreated, patients may progress to blindness, it is critical that the neurologist understand the importance of visual monitoring beyond visual acuity testing. Information obtained through serial perimetry is key for selecting proper therapy to prevent or reverse visual loss. This article should serve to provide the neurologist with a common language when discussing visual loss and treatment decisions with the neuroophthalmologist or the ophthalmologist. Results from the Idiopathic Intracranial Hypertension Treatment Trial now give evidence-based treatment strategies for IIH, since in patients with IIH and mild visual loss, acetazolamide plus diet resulted in significant improvement in visual field function, papilledema grade, quality-of-life measures, and CSF pressure.16 REFERENCES 1. Trobe JD, Acosta PC, Shuster JJ, Krischer JP. An evaluation of the accuracy of community-based perimetry. Am J Ophthalmol 1980;90(5):654Y660. 2. Wall M. The morphology of visual field damage in idiopathic intracranial hypertension: an anatomic region analysis. In: Mills RP, Heijl A, eds. Perimetry update 1990/1991 Amsterdam: Kugler Publications, 1991:20Y27. 3. Wall M, George D. Visual loss in pseudotumor cerebri. Incidence and defects related to visual field strategy. Arch Neurol 1987;44(2):170Y175. 4. Wall M, George D. Idiopathic intracranial hypertension. A prospective study of 50 patients. Brain 1991;114(pt 11A):155Y180. 5. Corbett JJ, Jacobson DM, Mauer RC, Thompson HS. Enlargement of the blind spot caused by papilledema. Am J Ophthalmol 1988;105(3):261Y265. 6. Shah VA, Kardon RH, Lee AG, et al. Long-term follow-up of idiopathic intracranial hypertension: the Iowa experience. Neurology 2008;70(8):634Y640. 7. Corbett JJ, Thompson HS. The rational management of idiopathic intracranial hypertension. Arch Neurol 1989;46(10):1049Y1051. 8. Frise´n L. Swelling of the optic nerve head: a staging scheme. J Neurol Neurosurg Psychiatr 1982;45(1):13Y18. 9. Wall M, Johnson CA, Kutzko KS, et al. Long- and short-term variability of automated perimetry results in patients with optic neuritis and healthy subjects. Arch Ophthalmol 1998;116(1):53Y61. 10. Wall M, Woodward KR, Doyle CK, Artes PH. Repeatability of automated perimetry: a comparison between standard automated perimetry with stimulus size III and V, matrix, and motion perimetry. Invest Ophthalmol Vis Sci 2009;50(2):974Y979. 11. Cinciripini GS, Donahue S, Borchert MS. Idiopathic intracranial hypertension in prepubertal pediatric patients: characteristics, treatment, and outcome. Am J Ophthalmol 1999;127(2): 178Y182. 12. Lessell S. Pediatric pseudotumor cerebri (idiopathic intracranial hypertension). Surv Ophthalmol 1992;37(3):155Y166. 13. Babikian P, Corbett J, Bell W. Idiopathic intracranial hypertension in children: the Iowa experience. J Child Neurol 1994;9(2):144Y149. 14. Balcer LJ, Liu GT, Forman S, et al. Idiopathic intracranial hypertension: relation of age and obesity in children. Neurology 1999;52(4):870Y872. 15. Van Dop C, Conte FA, Koch TK, et al. Pseudotumor cerebri associated with initiation of levothyroxine therapy for juvenile hypothyroidism. N Engl J Med 1983;308(18):1076Y1080. 16. Wall M, McDermott MP, Kieburtz KD, et al. Effect of acetazolamide on visual function in patients with idiopathic intracranial hypertension and mild visual loss: the idiopathic intracranial hypertension treatment trial. JAMA 2014;1641Y1651.
1074
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
August 2014
The Importance of Visual Field Testing in Idiopathic Intracranial Hypertension Michael Wall, MD, FAAN
ABSTRACT Idiopathic intracranial hypertension (IIH) is a disease of unknown cause typically affecting obese women in the childbearing years. Although headache is the most common symptom, the major morbidity of IIH is visual loss, with 5% to 10% of patients progressing to blindness. While about 95% of patients with IIH have visual loss documented by perimetry, only about one-third notice their visual loss because most loss occurs in the peripheral visual field. Since treatment decisions in IIH are made primarily by changes in visual field function, serial perimetry is the most critical test to obtain when following patients with IIH. This article describes the role of visual field testing in the monitoring of IIH patients in clinical practice, including its importance in communication among providers.
Address correspondence to Dr Michael Wall, University of Iowa, College of Medicine, Departments of Neurology and Ophthalmology, Iowa City Veterans Affairs Medical Center, Iowa City, IA 52242, [email protected]. Relationship Disclosure: Dr Wall’s institution receives a grant from the NIH. Unlabeled Use of Products/Investigational Use Disclosure: Dr Wall discusses the unlabeled use of acetazolamide in the treatment of idiopathic intracranial hypertension. * 2014, American Academy of Neurology.
Continuum (Minneap Minn) 2014;20(4):1067–1074.
Case A 20-year-old obese but otherwise healthy woman presented to a neurologist with a 2-month history of daily, constant, throbbing headaches and pulse synchronous tinnitus. She denied visual loss or history of tetracycline use, and she had no constitutional symptoms. On examination, she had bilateral papilledema (Practice Figure 1). Visual acuity was 20/20 in both eyes, confrontation visual field examination was normal, eye movements were full, and the remainder of her neurologic examination was normal. MRI showed an empty sella and flattened globes. Lumbar puncture revealed an opening pressure of 310 mm water with normal CSF constituents.
PRACTICE FIGURE 1
Ocular fundus examination (A, right eye; B, left eye) of the patient described in this case, a 20-year-old woman with idiopathic intracranial hypertension. Bilateral papilledema is present.
Continuum (Minneap Minn) 2014;20(4):1067–1074
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
1067
Visual Field Testing in IIH DISCUSSION It is common for neurologists to start treatment at this point, usually with acetazolamide along with counseling about a low-sodium weight-reduction diet. Practice Figure 2, however, shows a visual field example from a patient who was followed by a neurologist for 1 year with frequently documented normal visual acuities. It was not until the patient reported visual loss that this visual field examination was obtained. Perimetry shows severe visual field constriction in both eyes despite 20/25 visual acuity. Therefore, neither visual acuity nor the patient’s symptoms are reliable indicators of the presence of papilledema-related visual loss. It is important for the neurologist to know how the visual field is damaged in idiopathic intracranial hypertension (IIH). A variety of mechanisms produce visual field abnormalities. The major mechanism is nerve fiber bundle damage from intraneuronal ischemia due to compression from axoplasmic flow stasis. The arcuate bundles are most vulnerable, and glaucomatouslike visual loss ensues. Other less common mechanisms are globe flatteningYinduced hyperopia with or without choroidal folds and central visual field loss from a neurosensory detachment from fluid extending from the optic nerve head into the macula. Finally, the visual field examination itself can, at times, be difficult to interpret and can be the source of confusion.
PRACTICE FIGURE 2
1068
An example of severe visual field constriction in a different patient with idiopathic intracranial hypertension whose follow-up included confrontation fields and visual acuity testing. Severe visual field constriction has occurred.
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
August 2014
Case Continued Consultation with a neuro-ophthalmologist was obtained, and baseline and serial perimetry were performed to monitor for changes over time. Practice Figure 3 shows this patient’s baseline automated perimetry examination. (Practice Figure 4 is a normal perimetric result for comparison.)
PRACTICE FIGURE 3
Standard automated perimetry of the patient described in this case. The left eye is on the left side of the figure, and the right eye is on the right side of the figure. Generalized loss is present, especially in the inferonasal fields and areas around the blind spot.
Continued on page 1070 Continuum (Minneap Minn) 2014;20(4):1067–1074
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
1069
Visual Field Testing in IIH
Continued from page 1069
PRACTICE FIGURE 4
Standard automated perimetry of the right eye of a different patient that is within normal limits.
VISUAL FIELD TESTING A discussion of perimetry and the interpretation of the visual field examination follows. Two types of visual field testing are available: manual perimetry and automated perimetry.
1070
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
August 2014
Manual Perimetry Manual perimetry is most commonly performed using the Goldmann bowl perimeter. Screening for defects should be performed with the I-4-e, I-2-e, and I-1-e isopters. Practice Figure 2 is an example of perimetry performed using a Goldmann bowl. The advantages of manual perimetry mostly revolve around the fact that it is conducted by a technician (known as a perimetrist). These advantages include patient interaction with the perimetrist (important for subjects with attention difficulties and fatigue); custom test point locations, which refers to the fact that the test is done by hand and the test locations are chosen by the perimetrist (as opposed to standard automated perimetry where test locations are fixed on a 6-degree spaced grid); and improvisation of testing strategies based on concurrent findings, which provide more accurate mapping of defect shape. However, manual perimetry is less sensitive than standard automated perimetry. Its most severe limitation is that few perimetrists are adequately trained.1 Automated Perimetry Standard automated perimetry presents a small fixed-sized stimulus on a 6-degree spaced grid within the central 21 to 27 degrees of the visual field. The test continues until the dimmest light at each of the preselected test locations is found. The computer processes the data, and summary statistics are calculated. Subjects may find standard automated perimetry to be boring and have difficulty maintaining attention. Clues to poor perimetry performance are excessive false-positive and false-negative catch trials. False-positive trials occur when no stimulus is shown and subjects press the response button as if they saw a stimulus, or when they respond in a time window that is not physiologically possible. False-negative responses are very important to note and are tabulated as follows: The test software projects substantially brighter stimuli in an area where a subject previously responded to having seen a dimmer stimulus, and if the subject misses the stimulus, the trial is counted as a false-negative response. If the number of false-negative trials occurring in a session is more than 15%, the subject may no longer be paying attention to the test, and the results should be ignored or discounted. Automated perimetry is also susceptible to artifacts or areas of visual loss due to external factors such as malpositioned corrective lenses that cause the rim of the lens to block stimuli. Eyelid ptosis or tilting the head forward can cause obstruction to viewing the upper part of the visual field with resultant visual field defects. Refractive scotoma, visual field defects due to lack of appropriate refraction, can also occur. Contracted Visual Field Various cognitive factors and interactions with the perimetrist can cause a contracted visual field, which can occur with either manual or automated perimetry. These include improper testing instructions, inability to understand the test, lack of motivation, poor attention span, and distractions such as headache. These factors need to be identified since the end-stage visual field in IIH has a similar contracted pattern (Practice Figure 52). Continuum (Minneap Minn) 2014;20(4):1067–1074
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
1071
Visual Field Testing in IIH
PRACTICE FIGURE 5
Grades of visual loss in idiopathic intracranial hypertension, from mild to severe. Reprinted with permission from Wall M, Kugler Publications.2 B 1991 Imaging and Perimetry Society.
Case Continued Results of the patient’s baseline automated perimetry examination showed no evidence of artifacts, and the false-negative and false-positive catch trials were in an acceptable range. The lower left of the total deviation probability map printout showed many test locations were flagged as abnormal (the test point falls outside the P=.05 level of an age-matched control’s test point).
DISCUSSION CONTINUED Visual field loss occurs in almost all cases of IIH. In a prospective study of IIH, visual loss in at least one eye (other than enlargement of the physiologic blind spot) was found in 96% of patients with Goldmann perimetry using a disease-specific strategy, and in 92% of patients with automated perimetry.3,4 About one-third of this visual loss is mild and unlikely to be noticed by the patient, but it serves as a marker with which to guide therapy.4 Most patients with IIH have visual loss, and the standard of care is to obtain perimetry to monitor this loss. The earliest visual field defect in IIH, other than an enlarged blind spot, is often an inferior nasal step defect followed by peripheral nasal loss. Arcuate defects, nerve fiber bundle defects that arc around the central 10 degrees, may appear next, followed by a gradual depression of the entire field, most pronounced peripherally. The stages of visual loss are shown in Practice Figure 5.2 The most common defects in IIH are enlargement of the physiologic blind spot and loss of inferonasal portions of the visual field along with constriction of isopters. Constriction of isopters is a pattern of contraction of the threshold to a moving stimulus due to a generalized
1072
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
August 2014
reduction in visual sensitivity. Central defects are distinctly uncommon and warrant a search for another diagnosis unless a large serous retinal detachment from high-grade optic disc edema is present and spreading toward the macula. The loss of visual field may be progressive and severe, leading to blindness in about 5% of cases. The time course of visual loss is usually gradual; however, acute severe visual loss can occur. Blind spot enlargement is ubiquitous in IIH. Since refraction often eliminates this defect,5 blind spot enlargement should not be considered significant visual loss unless it encroaches on fixation. Also, since blind spot size is dependent on refraction, it should not be used to follow the course of therapy. With treatment, significant perimetric improvement occurs in about 50% of patients.4 A study that evaluated a subgroup of patients with worsening of their vision showed recent weight gain was the only factor significantly associated with decline in vision.4 Other groups at risk for severe visual loss are black men, patients with glaucoma, and patients who are rapidly tapering off corticosteroids. The course of IIH is often chronic with recurrences especially during periods of weight gain.6 Pitfalls to Avoid Corbett and Thompson have pointed out that many physicians follow patients with IIH with the wrong tests.7 Snellen acuity and visual evoked potentials are insensitive methods to detect the visual loss of IIH. Repeated measurements of CSF pressure can be misleading as CSF pressure fluctuates throughout the day and does not correlate well with the clinical state. Papilledema as measured by the Frise´n scale, ocular fundus photography, or optical coherence tomography are much better surrogates for average CSF pressure. Patients with IIH should be followed with perimetry and serial stereo fundus photos or optic disc grading using ´n scale.8 Automated perimetry is used for attentive and motivated the Frise subjects; in others, manual perimetry gives more reproducible results. Automated perimetry such as that done by the Humphrey Field Analyzer or Octopus perimeter usually gives reproducible results in patients with minimal visual loss. Since variability increases logarithmically with increasing visual system damage, determining whether a visual field has changed can be very problematic.9,10 Most experts require a series of at least five visual field examinations in these patients to be confident of calling visual field change, and even in the case where multiple perimetric examinations are performed, it is wise to require confirmation of worsening with at least one additional examination. Pediatric Idiopathic Intracranial Hypertension Excellent reviews of IIH in children can be found.11Y13 Some interesting differences occur between IIH in the pediatric age group and adults. In IIH from childhood through puberty, the incidence in girls and boys is the same.14 Obesity does not appear important in the pathogenesis of IIH in prepubertal children. The reported etiologies limited to children are nutritional restoration after malnutrition and thyroid replacement therapy in hypothyroid children.15 The effect of papilledema on vision is the same in children as in adults. Formal perimetry can be performed in most children older than 6 years. SUMMARY IIH is characterized by elevated CSF pressure of unknown cause. It is predominantly a disease of obese women in the childbearing years. Diagnosis should adhere to the Continuum (Minneap Minn) 2014;20(4):1067–1074
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
1073
Visual Field Testing in IIH
Modified Dandy Criteria, and other causes of intracranial hypertension should be sought. Since loss of visual function is common in IIH and, if left untreated, patients may progress to blindness, it is critical that the neurologist understand the importance of visual monitoring beyond visual acuity testing. Information obtained through serial perimetry is key for selecting proper therapy to prevent or reverse visual loss. This article should serve to provide the neurologist with a common language when discussing visual loss and treatment decisions with the neuroophthalmologist or the ophthalmologist. Results from the Idiopathic Intracranial Hypertension Treatment Trial now give evidence-based treatment strategies for IIH, since in patients with IIH and mild visual loss, acetazolamide plus diet resulted in significant improvement in visual field function, papilledema grade, quality-of-life measures, and CSF pressure.16 REFERENCES 1. Trobe JD, Acosta PC, Shuster JJ, Krischer JP. An evaluation of the accuracy of community-based perimetry. Am J Ophthalmol 1980;90(5):654Y660. 2. Wall M. The morphology of visual field damage in idiopathic intracranial hypertension: an anatomic region analysis. In: Mills RP, Heijl A, eds. Perimetry update 1990/1991 Amsterdam: Kugler Publications, 1991:20Y27. 3. Wall M, George D. Visual loss in pseudotumor cerebri. Incidence and defects related to visual field strategy. Arch Neurol 1987;44(2):170Y175. 4. Wall M, George D. Idiopathic intracranial hypertension. A prospective study of 50 patients. Brain 1991;114(pt 11A):155Y180. 5. Corbett JJ, Jacobson DM, Mauer RC, Thompson HS. Enlargement of the blind spot caused by papilledema. Am J Ophthalmol 1988;105(3):261Y265. 6. Shah VA, Kardon RH, Lee AG, et al. Long-term follow-up of idiopathic intracranial hypertension: the Iowa experience. Neurology 2008;70(8):634Y640. 7. Corbett JJ, Thompson HS. The rational management of idiopathic intracranial hypertension. Arch Neurol 1989;46(10):1049Y1051. 8. Frise´n L. Swelling of the optic nerve head: a staging scheme. J Neurol Neurosurg Psychiatr 1982;45(1):13Y18. 9. Wall M, Johnson CA, Kutzko KS, et al. Long- and short-term variability of automated perimetry results in patients with optic neuritis and healthy subjects. Arch Ophthalmol 1998;116(1):53Y61. 10. Wall M, Woodward KR, Doyle CK, Artes PH. Repeatability of automated perimetry: a comparison between standard automated perimetry with stimulus size III and V, matrix, and motion perimetry. Invest Ophthalmol Vis Sci 2009;50(2):974Y979. 11. Cinciripini GS, Donahue S, Borchert MS. Idiopathic intracranial hypertension in prepubertal pediatric patients: characteristics, treatment, and outcome. Am J Ophthalmol 1999;127(2): 178Y182. 12. Lessell S. Pediatric pseudotumor cerebri (idiopathic intracranial hypertension). Surv Ophthalmol 1992;37(3):155Y166. 13. Babikian P, Corbett J, Bell W. Idiopathic intracranial hypertension in children: the Iowa experience. J Child Neurol 1994;9(2):144Y149. 14. Balcer LJ, Liu GT, Forman S, et al. Idiopathic intracranial hypertension: relation of age and obesity in children. Neurology 1999;52(4):870Y872. 15. Van Dop C, Conte FA, Koch TK, et al. Pseudotumor cerebri associated with initiation of levothyroxine therapy for juvenile hypothyroidism. N Engl J Med 1983;308(18):1076Y1080. 16. Wall M, McDermott MP, Kieburtz KD, et al. Effect of acetazolamide on visual function in patients with idiopathic intracranial hypertension and mild visual loss: the idiopathic intracranial hypertension treatment trial. JAMA 2014;1641Y1651.
1074
www.ContinuumJournal.com
Copyright © American Academy of Neurology. Unauthorized reproduction of this article is prohibited.
August 2014
