Bryan J. Winn

The multifocal electroretinogram.

The multifocal electroretinogram (mfERG) technique allows local ERG responses to be recorded simultaneously from many regions of the retina. As in the case of the full-field ERG, the ganglion cells contribute relatively little to the response, which originates largely from the outer retina. The mfERG is particularly valuable in cases in which the fundus appears normal, and it is difficult to distinguish between diseases of the outer retina and diseases of the ganglion cells and/or optic nerve. The mfERG can also help to differentiate among outer retinal diseases, to follow the progression of retinal diseases, and, with the addition of the mfVEP, to differentiate between organic and nonorganic causes of visual loss. However, because the difficulties encountered in recording and analyzing mfERG responses are greater than those involved in full-field ERG testing, mfERG testing is best left to centers with an electrophysiologist familiar with the mfERG test. Although this technique is relatively new and standards are still being developed, centers capable of recording reliable mfERG responses can be found in hundreds of locations around the world.

The multifocal visual evoked potential

With the multifocal technique, visual evoked potentials (VEPs) can be recorded simultaneously from many regions of the visual field. For the multifocal VEP (mfVEP), the patient views a display that typically contains 60 sectors, each with a checkerboard pattern. The display covers about the same retinal area as the 24-2 Humphrey visual field (HVF). However, due to the scaling of the sectors of the mfVEP display, the fields are sampled differently by the mfVEP and HVF. To assess local defects in the visual field, the mfVEP responses must be compared with normal controls. These comparisons require relatively sophisticated analyses and software. Whereas the mfVEP can be recorded relatively easily with the same equipment used to record multifocal electroretinograms (mfERGs), the software needed to perform the analysis is not yet widely available. The mfVEP is valuable for ruling out non-organic visual loss, diagnosing and following patients with optic neuritis/multiple sclerosis, evaluating patients with unreliable or questionable HVFs, and following disease progression. When combined with the mfERG, diseases of the outer retina (before the retinal ganglion cells) can be distinguished from diseases of the ganglion cells and/or optic nerve. The difficulties encountered in recording and analyzing mfVEP responses are greater than those involved in full-field VEP testing. Thus, in its current form, the mfVEP is best recorded and interpreted by ophthalmologists and electrophysiologists experienced with the technique. However, this technique is developing rapidly; advances in commercial hardware and software are expected in the near future.

Detecting glaucomatous damage with multifocal visual evoked potentials: how can a monocular test work?

PurposeTo understand and improve the detection of glaucomatous damage with multifocal visual evoked potentials (mfVEP) obtained from single eyes. Patients and MethodsMonocular mfVEP recordings were obtained from both eyes of 30 individuals with no known visual abnormalities. The 44.5°-diameter display contained 60 sectors. Probability plots, analogous to the total deviation probability plot of the Humphrey Visual Field Analyzer, were created based on tests that compared each eye (monocular test), or the ratio of the responses from the 2 eyes (interocular test), to group norms. ResultsFor the monocular test, the number of points exceeding the 5% confidence level was not distributed randomly among individuals or among field locations within an individual. Individuals with small signals (i.e., low signal-to-noise ratios [SNR]) showed too many “abnormal” points, while those with relatively large SNR values showed too few. Reasonably good specificity was obtained by defining an abnormality in terms of a cluster of significant points in the mfVEP probability plot. For the interocular test, the results were close to those expected by chance. ConclusionsBoth monocular and interocular tests will be of value when testing glaucoma patients with the mfVEP technique. The interocular test is a more sensitive indicator of glaucomatous damage when a region when healthy has a large signal (SNR) and damage is largely unilateral, whereas the monocular test will be a more sensitive test when a region when healthy has a small signal (SNR). However, the statistics underlying monocular comparisons of mfVEPs are not simple. To obtain high specificity, criteria based on clusters of points need to be used and norms obtained for every laboratory.

Interpreting the multifocal visual evoked potential: the effects of refractive errors, cataracts, and fixation errors

Aim: To understand how refractive errors, cataracts, and fixation errors affect multifocal visual evoked potential (mfVEP) responses. Methods: Monocular mfVEP responses were obtained using a pattern reversal dartboard display. For the control condition, visual acuity was corrected to ⩾20/20 and foveal fixation was maintained. The right eye was tested under the following conditions: simulated refractive error, simulated cataract, steady eccentric fixation, and unsteady fixation. Results: No subject demonstrated significant abnormalities under control conditions. For the simulated refractive error condition, significant centrally located abnormalities were seen for all subjects. For the simulated cataract condition, significant abnormalities were found for three subjects. The steady eccentric fixation condition yielded abnormalities in both eyes for all subjects while the unsteady fixation condition yielded significant central abnormalities in the tested eye. With eccentric and unsteady fixation conditions, all subjects had at least one sector with a waveform polarity reversal. Conclusions: While the mfVEP is a useful tool for identifying local optic nerve damage or ruling out non-organic aetiology of visual field defects, factors such as uncorrected refractive errors, cataract, eccentric fixation, and unsteady fixation can produce apparent field defects on the mfVEP. With care, these problems can be correctly identified.

Facial Nerve Injury during External Dacryocystorhinostomy

OBJECTIVE To describe weakness of the orbicularis oculi muscle after external dacryocystorhinostomy (DCR) and propose an anatomic explanation for the complication. DESIGN Retrospective, observational study. PARTICIPANTS Sixteen patients (13 female, 3 male) with a mean age of 60 years (median, 61 years; range, 34-85 years). METHODS A retrospective chart review was performed of consecutive patients who had nasolacrimal duct obstruction repair by external DCR. Patients were identified who developed postoperative orbicularis oculi muscle weakness that manifested as hypometric blink or lagophthalmos with or without punctate keratopathy on the operated side. Patient parameters collected included demographic data, type of incision, incision length, use of lacrimal stent, length of follow-up, intraoperative and postoperative complications, and time to resolution of clinical findings. Statistical analysis was performed using a 2-tailed Fisher exact test with clinical significance designated at alpha = 0.05. MAIN OUTCOME MEASURES Identification of patients with orbicularis oculi muscle weakness after external DCR, documentation of incision type, clinical findings, and recovery of function. RESULTS Among 215 patients and 247 surgeries, 16 individuals (7.4%) were identified who demonstrated abnormalities of eyelid closure in the postoperative period after external DCR. Of these, 13 patients had lagophthalmos with or without hypometric blink and 3 patients had hypometric blink alone. Eleven patients underwent surgery through a nasojugal incision, 4 patients underwent surgery through a vertical incision, and 1 patient underwent surgery through an eyelid margin incision. The degree of postoperative lagophthalmos was on average 1.5 mm. Four patients developed punctate keratopathy. Follow-up ranged from 3 to 50 weeks (mean, 20 weeks). Resolution of lagophthalmos was seen on average by 14 weeks with the longest time to resolution of 32 weeks. Three individuals continued to have residual hypometric blink at the time of last follow-up. CONCLUSIONS Damage to peripheral fibers of the zygomatic and buccal branches of the facial nerve as they course through the medial canthal area to innervate the upper eyelid orbicularis oculi muscle may occur during external DCR surgery. Such injury may be responsible for orbicularis oculi muscle weakness manifesting as postoperative abnormal eyelid closure and lagophthalmos. In our cohort of patients, these findings were temporary and typically resolved in several months.

Sclerosing orbital inflammation and systemic disease.

Purpose: To determine the clinical differences between sclerosing orbital inflammation (SOI) isolated to the orbit and SOI manifesting as part of systemic inflammatory disease. Methods: For the case series, the authors identified patients with SOI from their patient database and tabulated their clinical data. For the literature review, a search for case reports of SOI in the English literature was performed. The clinical data of each were tabulated and analyzed. Results: For the case series, 13 cases of SOI were identified, 2 with multifocal fibrosclerosis (MFF) and 4 with other systemic inflammatory diseases. Of the 5 bilateral cases, 4 (80%) had some form of systemic inflammatory disease including 2 with MFF. Only 2 (25%) of the 8 unilateral cases had systemic inflammatory disease. The average ESR was 7 mm/hour for those without systemic disease and 41 mm/hour with evidence of systemic disease (p = 0.038). For the literature review, the authors identified 68 case reports of SOI not previously reported in large case series, 34 associated with MFF, 5 associated with other systemic disease, and 29 not associated with any systemic disease. Sixty-nine percent of cases with systemic disease had bilateral orbital involvement, whereas only 3.6% of those without systemic disease were bilateral (p = 1.15 × 10−8). Twenty of the cases with MFF noted ESR (83 mm/hour, mean), 95% of which were above normal. ESR was noted in only one non-MFF, nonsystemic disease case and was normal. Conclusions: SOI in the setting of MFF or other systemic inflammatory disease is often bilateral and associated with an elevated ESR.

Isolated squamous cell carcinoma of the orbital apex.

A 43-year-old woman (Case 1), 63-year-old man (Case 2), and a 67-year-old man (Case 3) presented with diplopia (Cases 1, 2, and 3) and upper-eyelid ptosis (Cases 1 and 3). The cases had preceding cranial nerve V1 disturbances ranging from 3 months to 8 years. Each demonstrated complete internal ophthalmoplegia and external ophthalmoplegia. No case had a cutaneous squamous cell carcinoma (SCC) on presentation or by history. Imaging revealed isolated orbital apex masses. Tumor biopsies revealed SCCs of various differentiations. Systemic workup revealed no extraorbital malignancy. All received radiation therapy, and 2 patients underwent adjuvant chemotherapy. One patient is alive since diagnosis (49 months). In Case 2, SCC developed in the contralateral orbit, and the patient died 19 months after diagnosis; and Case 3 died 12 months after diagnosis. These isolated cases of orbital SCC may have arisen from orbital choristomatous squamous epithelium, may represent de novo or metastatic tumors, or may be manifestations of occult perineural spread.

Measurement of Eyebrow Position From Inferior Corneal Limbus to Brow: A New Technique

Purpose: To develop a standard measure of eyebrow position for evaluation of eyebrow ptosis and to provide normative measurements for eyebrow position using this easily reproducible measure. Methods: A noncomparative interventional case series was performed. Measurements of eyebrow position were made on 213 subjects without cosmetic or functional complaints who presented to the eye clinic for routine eye examination during a 1-year period. Measurements were taken in the primary position of gaze. Central eyebrow height was measured as the distance from the central inferior corneal limbus to the first row of mature brow hairs (ILB) under loupe magnification. Additional measurements included the distance from the upper eyelid margin to brow, margin reflex distance-1, and palpebral fissure width. Results: Of the 213 subjects, 56 (26.5%) were male and 157 (73.5%) were female. Ages ranged from 5 to 80 years. Mean ILB height was 19.4 mm for males and 19.7 mm for females. The ILB was not associated with measures of eyelid height such as palpebral fissure width. There was no statistically significant difference in ILB height between males and females. However, increased ILB height was associated with increased age. African Americans had statistically significant increased mean ILB measurements compared with whites. Conclusions: Measurement of ILB height provides an accurate and easily reproducible measure of eyebrow height that may be useful in the diagnosis and treatment of conditions affecting the middle and upper face. Race, but not sex, seems to be an important consideration in proper central eyebrow position.

Laterality of Brain and Ocular Lesions in Aicardi Syndrome

This study reports a large case series of children with Aicardi syndrome. A new severity scoring system is established to assess sidedness of ocular and brain lesions. Thirty-five children were recruited from Aicardi syndrome family conferences. All children received dilated ophthalmologic examinations, and brain magnetic resonance images (MRIs) were reviewed. Ocular and brain MRI Aicardi lesion severity scores were devised. A linear mixed model was used to compare each side for the ocular and brain MRI severity scores of Aicardi-associated disease. Twenty-six children met the inclusion criteria for the study. All subjects were female, ages 3 months to 19 years. Rates per child of optic nerve coloboma, severe lacunae, and microphthalmos in one or both eyes (among those with complete fundus examinations available) were 10/24 (42%), 8/22 (36%), and 7/26 (27%), respectively. Ocular and brain MRI asymmetry was found in 18% (4/22) and 58% (15/26) of subjects, respectively, with more right-sided brain lesions than left-sided ones (V = 52, P = 0.028). A significant correlation between sidedness of brain disease and microphthalmos was noted (T = 2.54, P = 0.02). This study substantiates the range and severity of Aicardi syndrome-associated ophthalmologic and brain MRI lesions from prior smaller case series.

Multifocal visual evoked potentials to cone specific stimuli in patients with retinitis pigmentosa

Our aim was to determine whether patients with retinitis pigmentosa show differences in L- and M-cone multifocal visual evoked potential (mfVEP) responses that are eccentricity dependent, as has been shown for control subjects. Second, we compared the losses for mfVEPs to losses on achromatic visual field and multifocal electroretinogram (mfERG) measures in the patients. Monocular mfVEPs were recorded to a pattern reversing display that modulated only the L- or M-cones. Also, standard automated achromatic visual fields and mfERGs were obtained. For the control subjects, the ratio of L-cone to M-cone mfVEP amplitudes increased as a function of retinal eccentricity. For the patients, the ratio did not vary with eccentricity. For all measures, responses were least affected for the first ring (central 2.4 degrees ) and most affected for the third ring (11.6 degrees - 44.4 degrees ). For the first ring, mfERG amplitudes were more impaired than were the mfVEPs or the visual field thresholds. For most of the patients, there was local response correspondence among our measures of visual function.