Perimetry Results Research Articles

Frequency Doubling Technology Perimetry in Open-angle Glaucoma Eyes With Hemifield Visual Field Damage: Comparison of High-tension and Normal-tension Groups

To evaluate the performance of frequency doubling technology (FDT) perimetry in open-angle glaucoma eyes with hemifield visual field damage and to compare it between open-angle glaucoma with high pressure [high-tension glaucoma (HTG)] and those with normal pressure [normal-tension glaucoma (NTG)] groups. FDT perimetry with the N-30 full threshold protocol and standard automated perimetry (SAP) using the Humphrey Field Analyzer with the 30-2 full threshold protocol were performed in 20 eyes of 20 HTG patients and 36 eyes of 36 NTG patients with visual field damage confirmed with SAP in only one hemifield. There was no significant difference in demographics, the Heidelberg Retina Tomography indices, and the Humphrey Field Analyzer indices between HTG and NTG groups. Regarding the FDT perimetry results, mean deviation in the global field (P=0.009) and mean sensitivity in the SAP-spared (P=0.001) and SAP-impaired (P=0.011) hemifields were lower; the numbers of FDT abnormal test points (probability of abnormality <5%) in the SAP-spared hemifield were significantly greater (P=0.005) in HTG than in NTG groups. Eyes in which FDT results of the SAP-spared hemifield were judged as abnormal was more frequent in HTG groups (P=0.007). The performance of FDT perimetry to detect early or preperimetric glaucomatous functional changes should be different between HTG and NTG eyes.

Relationship between Short Wavelength Perimetry and Central Corneal Thickness Values in Ocular Hypertensive Subjects

To evaluate the results of short wavelength perimetry (SWAP) of ocular hypertensive (OHT) patients and correlate these findings with central corneal thickness (CCT) measurements. Thirty-seven OHT patients with a mean age of 50.2+/-8.2 (SD) years and 30 control subjects with a mean age of 50.3+/-8.5 (SD) years were included in this study. A questionnaire was applied to patients to evaluate the demographic risk factors that may predict glaucoma development. After a detailed ophthalmologic examination, achromatic and short wavelength perimetries and ultrasonic pachymetry were performed and the results were compared between the two groups with Student t test and Mann-Whitney U test. A p value<0.05 is considered as statistically significant. Mean CCT was higher in the OHT group (right eye; 558.13+/-28.39 microm and left eye; 558.94+/-27.30 microm) when compared with the control subjects (524.66+/-30.53 microm and 525.86+/-30.46 microm, respectively) (p<0.01). A significant positive correlation was found between CCT measurements and intraocular pressure (r=0.5, p<0.001). Four right eyes (10.8%) and five left eyes (13.5%) of OHT patients had defects in SWAP. OHT patients with SWAP abnormalities had significantly lower CCT measurements in right (527.25+/-17.34 microm) and left eye (528.80+/-13.60 microm) when compared with OHT patients without SWAP defects (561.87+/-27.29 microm and 563.65+/-25.92 microm, respectively) (p<0.05). Significant correlations were found between CCT and SWAP MD, PSD, and CPSD (p<0.05). OHT patients with SWAP abnormalities had significantly lower CCT measurements than those without. CCT is considered as a risk factor for the development of glaucomatous damage in OHT patients.

Combining Structural and Functional Testing for Detection of Glaucoma

To assess whether the combined use of both structural and functional tests improves discrimination between healthy and glaucomatous eyes over either type of testing alone. Observational cross-sectional study. One hundred twenty-three eyes of 123 participants enrolled in the Diagnostic Innovations in Glaucoma Study. Because both structural and functional tests were evaluated, 2 definitions of glaucoma were used: glaucomatous visual field (VF) damage based on repeatable abnormal standard automated perimetry results (n = 43) and glaucomatous optic disc (glaucomatous optic neuropathy [GON]) based on masked assessment of optic disc stereophotographs (n = 65). Participants had scanning laser polarimetry, optical coherence tomography (OCT), and confocal scanning laser ophthalmoscopy imaging in addition to frequency-doubling technology (FDT) perimetry and short-wavelength automated perimetry (SWAP) testing completed within a 6-month interval. For each glaucoma definition, sensitivities and specificities were calculated for the best structural parameters, FDT perimetry pattern standard deviation (PSD), and SWAP PSD/glaucoma hemifield test, and then for each possible pairwise combination of one structural and one functional parameter. The best structural parameters for discriminating between glaucoma and control eyes were nerve fiber indicator for scanning laser polarimetry, inferior average retinal nerve fiber layer thickness for OCT, and Moorfields regression classification for confocal scanning laser ophthalmoscopy. Sensitivities and specificities for detecting glaucomatous VF damage for scanning laser polarimetry, OCT, confocal scanning laser ophthalmoscopy, FDT perimetry, and SWAP were 41.9% and 98.3%, 58.1% and 98.3%, 58.1% and 84.5%, 44.2% and 98.3%, and 65.1% and 86.2%, respectively. Adding FDT perimetry to each of the best structural parameters led to a significant (P<0.05) increase in sensitivity without a significant change in specificity compared with structural parameters alone. Adding SWAP to each of the best structural parameters led to a significant increase in sensitivity and also a significant decrease in specificity compared with each structural parameter alone. A combination of parameters from structural tests and functional tests can improve the sensitivity of glaucoma detection. The sensitivity and specificity desired for a particular clinical application will determine the selection of the particular diagnostic tests.

Effect of Eye Testing Order on Automated Perimetry Results Using the Swedish Interactive Threshold Algorithm Standard 24-2

To evaluate whether the order of eye testing affects the mean deviation (MD) or the test reliability of visual field testing using the Swedish Interactive Threshold Algorithm (SITA) standard 24-2. Consecutive patients with manifest or suspect glaucoma with 2 prior sets of SITA standard 24-2 test results performed on the right eye first were enrolled. A subsequent test was performed on the left eye first. For each eye, the MD and the test reliability indexes (> or = 20%) were compared among the 3 successive examinations. Forty-seven patients (29 women and 18 men; mean +/- SD age, 70.6 +/- 11.9 years) were enrolled. The MD +/- SD was -5.83 +/- 5.43 dB OD and -5.46 +/- 4.86 dB OS. There was no statistically significant difference in the MD or the test reliability among the 3 test results for either eye. Fixation loss was responsible for the unreliable fields in almost all cases. Among this cohort of patients experienced with automated perimetry in a glaucoma subspecialty practice, changing the order of eye testing using the SITA standard 24-2 did not have a significant effect on the MD or the test reliability. Intereye fatigue may not be clinically significant with this algorithm. Fixation loss remains a problem with the use of this algorithm.

Effect of Cataract on Frequency Doubling Perimetry in the Screening Mode

To determine the effect of cataract on frequency doubling perimetry in the screening mode. Frequency doubling technology perimetry in the C-20-5 screening mode was performed prospectively on 34 patients with otherwise healthy eyes before and after phacoemulsification. Cataracts were scored using the LOCS III classification, and the number of missed points (at any level of severity) on the screening field was compared before and after surgery. Nine patients missed at least one point pre-operatively and had no misses post-operatively. Those patients with posterior subcapsular (PSC) cataract were significantly more likely to miss points on the screening frequency doubling technology perimetry than those without posterior subcapsular cataracts (P < 0.001; Fisher exact test). In addition, the degree of posterior subcapsular cataract strongly correlated with the number of missed points pre-operatively (r = 0.97). The degree of nuclear sclerotic cataract did not correlate strongly with the number of missed points (r = 0.26), but the correlation was slightly stronger in the presence of cortical cataract (r = 0.36). Advanced age-related cataracts may cause false positive results on the screening frequency doubling technology, and the presence of even mild posterior subcapsular cataract may be a cause of false positive results and should be taken into consideration when interpreting the screening frequency doubling technology perimetry results.

Reliability of the First Eye and Second Eye in Frequency Doubling Technology Perimetry

To compare the reliability of the perimetry results of the first eye and the second eye with frequency doubling technology (FDT). The subjects were 328 residents who underwent the C-20-5 mode of FDT at a city in central Japan. FDT perimetry was always performed first in the right eye and then in the left eye without any time between tests. When more than 33% fixation loss or false-positive error was detected, the result was judged unreliable. Of the 328 subjects, the bilateral perimetry results were reliable in 255 subjects (77.7%), the unilateral results were reliable in 57 (17.4%), and there was not a reliable result in either eye in 16 (4.9%) subjects. Of the 57 subjects whose unilateral result was unreliable, the result of the second eye was unreliable in 50 (88%) subjects, and the result of the first eye was unreliable in 7 (12%). This difference in the reliability between the first eye and second eye was significant (P < 0.001). There were no differences in the age, sex, visual acuity, refractive error, test duration, or number of glaucoma suspects between the two groups whose unilateral result was unreliable in the first eye or the second eye. The FDT perimetry result of the second eye was less reliable than that of the first eye.

The Groningen Longitudinal Glaucoma Study. I. Baseline sensitivity and specificity of the frequency doubling perimeter and the GDx nerve fibre analyser

To describe the baseline data of a large cohort of patients included for follow-up with perimetry using the frequency doubling technique (FDT) and with quantification of the retinal nerve fibre layer as assessed by GDx, and to calculate the sensitivity and specificity of both devices from these baseline data. Regular visitors to our glaucoma service were included. All subjects were followed for at least 4 years with FDT in full-threshold mode, GDx and conventional perimetry. Patients were classified as having either glaucoma or suspect glaucoma, according to baseline perimetry results. In addition, a group of healthy subjects was recruited outside the hospital. A total of 452 glaucoma patients, 423 glaucoma suspects and 237 healthy subjects were incorporated into the analyses. Sensitivities for both FDT and GDx were fixed at 0.90. For the group as a whole, the specificity was 0.81 for FDT, using number of depressed test-points p < 0.01 in the total deviation probability plot with a cut-off point > 1, and 0.78 for GDx, using the Number, with a cut-off point > 29. The area under the receiver operating characteristic (ROC) curve was 0.92 for FDT and 0.94 for GDx. Of the subjects with suspect glaucoma, 75% showed normal FDT test results and 52% showed normal GDx results. Unlike FDT, GDx failed to detect some moderate/severe glaucoma cases. The performances of FDT and GDx are approximately equivalent in terms of sensitivity, specificity and area under the ROC curve. In glaucoma suspects, GDx in particular yielded a rather high percentage of positive test results. The majority of these positive test results are presumably false-positive results rather than results indicating preperimetric glaucoma.

The multifocal visual evoked potential: An objective measure of visual fields?

We examined the effects of inter-modal attention and mental arithmetic on Humphrey visual field sensitivity and multifocal visual evoked potential (mfVEP) amplitude. Four normally sighted subjects (ages ranging from 24 to 58 years) participated in this study. Monocular visual field sensitivity was measured under two conditions: (1) standard testing condition and (2) while the subject performed a Paced Auditory Serial Addition Task (PASAT). Monocular mfVEPs were recorded in response to a 60-sector stimulus. The checkerboard pattern in each sector was contrast reversed according to a binary m-sequence. mfVEPs were recorded under two conditions: (1) standard testing conditions and (2) while the subject performed a PASAT. We found that, when compared to the no-task condition, all subjects had locations of significantly reduced Humphrey visual field sensitivities when performing the PASAT. In contrast, there were no significant decreases in mfVEP amplitude in any sector for any of the subjects while performing the PASAT. Our findings indicate that divided attention and ongoing mental processes did not affect the mfVEP. Therefore, the mfVEP provides an objective measure of visual field function that may be useful for some patients with unreliable automated static perimetry results.

Short-wavelength automated perimetry results are correlated with optical coherence tomography retinal nerve fiber layer thickness measurements in glaucomatous eyes

Purpose To determine the relationship between retinal nerve fiber layer (RNFL) thickness measured using optical coherence tomography (OCT) and short wavelength–sensitive visual function measured using short-wavelength automated perimetry (SWAP). Design Retrospective observational case series. Methods Subjects were recruited from the longitudinal University of California, San Diego, Diagnostic Innovations in Glaucoma Study and included 29 glaucoma patients with OCT imaging and reliable SWAP visual field (VF) testing within a 6-month window. Main outcome measures Correlations between deviation from normal (thinner than 97.5% of normal) RNFL measurements taken at 30° sectors (12 sectors described as clock hours) and SWAP average pattern deviation within 21 VF zones were determined. The number of OCT-measured RNFL sectors outside of normal limits and the number of VF zones outside of normal limits also were compared. Results The OCT nerve fiber layer thickness was outside of the normal limits in at least 1 sector in 26 (89.6%) patients. Twenty-eight (96.5%) patients had at least 1 SWAP VF zone outside of normal limits. Optical coherence tomography sectors 6-o'clock, 7-o'clock, and 8-o'clock (inferior and inferotemporal) and SWAP VF zones 13, 14, and 16 (superior hemifield central and arcuate areas) were the most frequently damaged. In general, the strongest R 2 associations were between inferior and inferior temporal RNFL sectors (e.g., 6-o'clock, 7-o'clock) and superior nasal/arcuate VF zones (e.g., zones 13, 14, 15) and between superior and superior temporal RNFL sectors (e.g., 12-o'clock, 11-o'clock) and inferior central and arcuate VF zones (e.g., zones 5, 6, 7) ( R 2 range = 24.3%–37.3%, all Ps ≤ 0.005). Most nonsignificant associations were found between superior RNFL sectors and superior VF zones. Conclusion Retinal nerve fiber layer thickness measured with OCT is topographically correlated with glaucomatous VF defects measured with SWAP.

Effect of age on the pupillomotor field.

To differentiate physiologic variation from visual field loss with pupillomotor perimetry, the effect of age on the normal pupillomotor field must be known. Given the absence of reported data, the authors aimed to analyze the effect of age on the pupillomotor field as measured with light stimuli of different properties. Subjects consisted of 23 healthy volunteers aged 20 to 28 years ("younger subjects") and 20 healthy volunteers aged 50 to 67 years ("older subjects"). Within a field of 20 degrees, a sequence of 25 focal light stimuli was performed repeatedly on a monitor. The pupil light reflex (PLR) was recorded to stimuli of different diameter and luminance under mesopic conditions. The mean amplitude of the PLR was calculated for each stimulus location and condition. Increasing stimulus luminance or size caused a larger PLR amplitude and a steeper decline of the PLR amplitude from the center to the periphery of the pupillomotor field. The older subjects had reduced mean PLR amplitude with a less pronounced decrease of PLR amplitude toward the field periphery. For the peripheral locations, the largest PLR amplitude was found in the temporal superior quadrants. There was considerable intra-individual test-retest variation in PLR amplitudes in younger and older subjects. The PLR is markedly reduced in older compared with younger subjects. Older subjects have a relatively less pronounced central peak of sensitivity. There are intra-individual test-retest variations in PLR amplitude and asymmetries in sensitivity within the normal pupillomotor field at any age. These findings must be considered in interpreting the results of pupillomotor perimetry.

Impact of cataract on the results of frequency-doubling technology perimetry

Purpose To determine the effect of cataract on the results of frequency-doubling technology (FDT) perimetry. Design Consecutive cohort study. Participants Forty-four patients with normal ophthalmic examinations, with the exception of cataract, scheduled to undergo phacoemulsification and posterior chamber lens implantation were prospectively identified and completed the study. Methods All subjects underwent FDT perimetry using the full-threshold C-20 strategy. Both eyes were tested within 1 month before cataract surgery and up to 3 months after surgery. The unoperated fellow eyes served as controls. Main outcome measures Changes in visual acuity (VA), mean deviation (MD), and pattern standard deviation (PSD) were evaluated. For each subject, the change in MD and PSD in the eye that underwent cataract surgery was adjusted for change in the control eye that is thought to occur due to a learning effect. Results Among the eyes that underwent cataract surgery, the median preoperative VA was 20/60 (range, 20/30–20/800) and the mean preoperative MD was −4.00±3.72 decibels (dB). Postoperatively, the median VA improved to 20/30 (range, 20/20–20/70) and the mean postoperative MD was −0.26±3.09 dB ( P<0.001). Among the control eyes, MDs were −1.74±3.71 dB preoperatively and −0.94±3.85 dB postoperatively ( P = 0.019). The adjusted improvement in MD among eyes that underwent cataract surgery was 2.94±3.44 dB ( P<0.001). There was no significant change in PSD. Preoperative VA correlated significantly with preoperative MD ( r = 0.39, P = 0.01). The improvement in VA correlated significantly with the adjusted improvement in MD ( r = 0.38, P = 0.01). Conclusions Cataract has an adverse effect on the MD but not the PSD in FDT perimetry. Among eyes with visually significant cataract, the MD correlates significantly with VA. After cataract surgery, the change in VA correlates significantly with the adjusted change in MD.

Effect of cataract extraction on frequency doubling technology perimetry

Purpose To investigate the effect of cataract extraction on the results of frequency doubling technology (FDT) perimetry in healthy subjects. Design Single-center, prospective, case series. Methods We performed FDT threshold C20-1 and Humphrey Swedish Interactive Threshold Algorithm (SITA)–fast programs within 1 month before and 2 months after phacoemulsification in 52 consecutive nonglaucomatous patients. Global indexes, including mean deviation and mean sensitivity of FDT and mean deviation of SITA-fast, were compared before and after cataract surgery. Mean sensitivity of FDT at various visual field grid locations was also compared before and after cataract surgery, as were localized indexes of both FDT and SITA-fast. Results Mean deviation improved after cataract surgery in both FDT threshold (from −7.09 dB–−2.16 dB) and SITA-fast program (from −6.14 dB–−2.87 dB). The mean sensitivity at 17 grid locations when the FDT threshold program was used significantly improved postoperatively (from 19.6 dB–26.13 dB). Postoperative improvements in mean sensitivity were also significant at all different sectors, but there were no significant differences of improvement among them. Postoperative pattern standard deviations from FDT and SITA-fast did not differ significantly from their preoperative values. Conclusions Cataracts induced a generalized reduction of sensitivity in FDT threshold as well as SITA-fast perimetry. Cataract removal did not change pattern standard deviation of FDT or of SITA-fast. Caution should be taken when interpreting the results of FDT perimetry in the eyes with cataract.

Effect of cataract on the results of automated perimetry in glaucoma

Effect of cataract on the results of automated perimetry in glaucoma

Upper temporal visual field depressions in the fellow eye in posterior acute optic neuritis: ‘knee’ or no ‘knee’, Wilbrand’s concept remains clinically significant

Aim: To determine whether an upper temporal visual field defect can occur in the asymptomatic fellow eye of patients with acute optic neuritis affecting the posterior optic nerve, suggesting involvement of contralateral crossing fibres (a concept originally proposed by Wilbrand). Methods: A retrospective analysis was performed on 135 patients from two cities with acute optic neuritis. Perimetry results were reviewed to determine whether there was an upper temporal visual field defect in the contralateral healthy eyes of those patients with posterior optic nerve enhancement on gadolinium-enhanced magnetic resonance imaging. Results: Abnormal enhancement of the intracranial optic nerve immediately anterior to, but not including, the optic chiasm was seen in nine patients. Of these, two cases exhibited superior temporal visual field defects in their contralateral healthy eyes. Repeat examination 12 days later in Case one and 24 days later in Case two revealed resolution of these defects. Conclusions: An acute lesion of the posterior optic nerve in optic neuritis can occasionally give rise to an upper temporal visual field depression in the asymptomatic fellow eye in the apparent absence of chiasmal involvement. These cases could indicate the involvement of crossing fibres which are ‘junctional’ in the sense that they follow a course closely associated with the junction of the posterior optic nerve and chiasm.Whether or not such fibres cross the junction into the posterior optic nerve, as suggested by Wilbrand, but recently refuted by Horton, the localising value of such field defects remains clinically significant.

Vigabatrin-associated loss of vision: rarebit perimetry illuminates the dose-damage relationship.

The utility of vigabatrin in the treatment of epilepsy is partially offset by its retinal toxicity. The relationship between dosage and damage is obscure. This may be due to perimetric shortcomings. The new technique of rarebit ('microdot') perimetry might be more informative. Twelve patients who had been treated with vigabatrin for various durations were examined by manual, kinetic perimetry and by rarebit perimetry. Rarebit results differed significantly between patients and normal controls and rarebit deficits were directly proportional to cumulated vigabatrin doses (correlation coefficients were - 0.92 in the nasal field and - 0.82 in the temporal field). Manual perimetry results were less clearly related to dosage (r = - 0.54 and r = - 0.73, respectively). Rarebit perimetry indicates that each treated subject will develop visual loss and that visual loss will be proportional to the accumulated dose. Conventional perimetry is less well suited to detecting and quantifying vigabatrin-associated visual loss.

Examining visual field defects in the paediatric population exposed to vigabatrin.

The antiepileptic drug, vigabatrin, has been linked to a specific pattern of visual field loss. The majority of studies have not included the paediatric population due to difficulties assessing visual field function. This is a particular problem as vigabatrin is effective against infantile spasms. A field-specific visual evoked potential was developed which consisted of a central stimulus (0-5 degrees radius) and a peripheral stimulus (30-60 degrees radius). Both stimuli consist of black and white checks which increase in size with eccentricity. Responses are recorded from occipital electrodes O2 and O1 referred to frontal electrode Fz. Electroretinograms and perimetry was performed were possible as a comparison. Thirty-nine children with epilepsy treated with vigabatrin aged from 3 to 15 years were included in the study; 35/39 children complied with the field-specific VEP, 26/39 complied with the ERG and 11/39 performed perimetry. Of these results, 18 children had normal ERG responses and eight had abnormal response. Visual field testing revealed four children had abnormal and seven had abnormal visual field results. The Field-specific VEP identified three of four abnormal perimetry results and six of seven normal perimetry results, giving a sensitivity of 75% and a specificity of 85.7%. When comparing perimetry results with the ERG parameters only the 30-Hz flicker amplitude, with a cut-off amplitude below 70 microV, gave a useful sensitivity of 75% and a specificity of 71%. The field-specific VEP is a useful alternative method that is both well tolerated by young children and gives a reliable indication of likely peripheral visual field loss associated with vigabatrin. The defect appears to have a similar prevalence in children as it does in adults.

The influence of visual field defects and other clinical parameters on reading performance: A retrospective study in a low vision population

Purpose: To examine the influence of visual field defects and other parameters, such as age, diagnosis, visual acuity, and magnification need, on reading performance in a low vision population. Methods: A total of 223 low vision patients were fitted with the best visual aid for reading according to their magnification need. Reading performance was related to distance visual acuity, magnification need, diagnosis, and visual field status. The results of kinetic Tuebingen manual perimetry were categorized according to the location, size, shape, and density of the scotoma. The fixation locus during perimetry was determined by the location of the blind spot. The outcome variable was reading performance of newspaper print according to the following categories: 1, fluent; 2, struggling; and 3, no reading ability. Results: A total of 71% of the patients were fluent, 25% were struggling, and 4% were non-readers. The affiliation to a reading category was related to visual acuity, magnification need, and diagnosis, but not to age and type of field defect alone. In patients with absolute central scotoma, it was related to fixation stability, but not to fixation locus alone. In absolute central scotoma, stable and eccentric fixation were favorable. Conclusions: The categorization of visual field defects, which considers the two main visual preconditions for reading (resolution and size of the reading visual field), helps to understand reading difficulties and improves the judgement for rehabilitation in the individual patient. An integrative view of visual acuity, magnification need, and visual field status allows the determination of the preconditions necessary to improve the individual patient’s reading performance.

Visual Acuity and 10 ° Automated Static Perimetry in Eyes with Retinitis Pigmentosa

Purpose: In a previous study we demonstrated that the progression of the disease retinitis pigmentosa (RP) can be readily monitored by the mean deviation (MD) measured by Humphrey central 10-2 perimetry, which assesses the sensitivity distribution in the macular area in eyes affected by RP. In the present study, we investigated whether the 10° perimetric results could predict the time of declining visual acuity in eyes with RP in a cross-sectional study. Methods: Humphrey 10-2 perimetry results and visual acuity were studied in the right eyes of 69 patients with typical RP. Patients whose eyes had cataract, glaucoma, cystoid macular edema, or other complications affecting vision were excluded. Results: Eyes with an MD of −15 dB or greater had almost normal visual acuity. Various degrees of visual acuity loss were observed in eyes with an MD of less than −15 dB. In the 35 eyes with an MD of less than −15 dB, visual acuity correlated well with the corrected pattern standard deviation (CPSD), which is the measure of the degree to which the shape of the measured field departs from the age-corrected normal reference field. Conclusion: In the absence of complications, many eyes with RP may experience acuity loss after the field constriction reaches an MD of less than −15 dB. The CPSD may be used as an indicator of acuity because eyes showing a lower CPSD tend to have greater loss of acuity among eyes with an equivalent MD value.

Field-specific visual evoked potentials. Identifying field defects in vigabatrin-treated children. Harding GFA, Spencer EL, Wild JM, Conway M, Bohn RL. Neurosurgery 2002;58:1261–1265.

Previous studies have linked vigabatrin, an antiepileptic drug, to a specific pattern of visual field loss from retinal toxicity. The visual field defect typically consists of bilateral concentric constriction with a binasal annular defect within the central 30 degrees and relative temporal sparing. Few studies have included the pediatric population because of difficulties in assessing the visual field by perimetry earlier than the age of 9 years, despite the fact that several of the most important indications for the use of vigabatrin are in children. A field-specific visual-evoked potential (VEP) was designed to identify visual field defects in children with epilepsy treated with vigabatrin, especially those unable to perform perimetry. This VEP was created with central (0–5-degree radius) and peripheral (30–60-degree radius) stimuli. Stimuli consisted of black-and-white checks that increased in size with eccentricity. Checks reversed at different rates, allowing separate central and peripheral responses to be recorded. Five vigabatrin-treated young adults with field defects were identified using this stimulus. Electroretinograms (ERG) were recorded to examine the effects of vigabatrin on retinal function. Thirty-nine children aged 3 to 15 years were included in the study. Twelve patients were examined by both the field-specific stimulus test and perimetry. Thirty-five of 39 children complied with the field-specific stimulus, 26 of 39 complied with the ERG, and 12 of 39 complied with perimetry. Using the summed amplitude of the peripheral response from O2 and O1, responses below 10 μV were deemed abnormal. The field-specific stimulus identified three of four abnormal perimetry results and seven of eight normal perimetry results, giving a sensitivity of 75% and a specificity of 87.5%. When comparing perimetry results with the ERG parameters, only the 30-Hz flicker amplitude, with a cutoff below 70 μV, gave a useful indication of visual field loss. The authors conclude that field-specific VEPs are well tolerated by children older than 2 years of age and are sensitive and specific in identifying vigabatrin-associated peripheral field defects.—Nancy J. Newman

Short wavelength automated perimetry, frequency doubling technology perimetry, and pattern electroretinography for prediction of progressive glaucomatous standard visual field defects

Purpose To evaluate the clinical use of a test battery of short wavelength automated perimetry (SWAP), frequency doubling technology perimetry (FDT), and pattern electroretinography (PERG) in predicting progressive glaucomatous visual field defects on standard automated perimetry (SAP). Study design A prospective, longitudinal, observational case series. Participants One hundred and fifty-two patients with primary open-angle glaucoma (POAG) with bilateral glaucomatous visual field defects on SAP were followed at 6-month intervals over a period of 30 months. Main outcome measures Short wavelength automated perimetry, FDT, and PERG results were compared between POAG eyes with and without progressive field loss on SAP. These two groups were used to evaluate whether PERG, SWAP, and/or FDT is predictive of future progression of field loss on SAP. Results Using the criteria of progressive field loss on SAP defined by the Collaborative Normal Tension Glaucoma Study, 54 eyes (study group) of 54 POAG patients showed progressive defects, whereas 84 eyes (control group) of 84 POAG patients showed no progression. Only 11.1% (6 of 54) of the eyes with a progression of field loss on SAP showed no increase of deficits on the three functional tests before progression. Short wavelength automated perimetry detected early progressive defects on SAP in 43 of the 54 eyes (79.6%). Of these 54 POAG eyes, FDT showed progressive deficits in 40 eyes (74.1%), whereas PERG amplitude P1N2 showed progressive deficits in 35 eyes (64.8%) before progression of field loss on SAP. A test battery consisting of SWAP and PERG P1N2-amplitude was able to detect 88.9% of eyes before a prediction of field loss on SAP. When comparing the results of the two functional tests, SWAP and FDT in the 84 eyes without progression of field loss on SAP between baseline and at 30 months, SWAP and FDT showed progressive deficits in 34.5% and 35.7%, respectively. Conclusions All three tests (SWAP, FDT, and PERG) have been successful in detecting glaucoma eyes with a future progression of standard visual field defects. A test battery of SWAP and PERG P1N2-amplitude improved the power to predict these progressive defects on SAP. It remains to be seen whether the long-term follow-up in POAG eyes will improve the false-positive rate of SWAP and FDT.