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Background: Pseudophakic pupillary block (PPB) was rare in patients who undergo phacoemulsification and posterior chamber intraocular lens (PCIOL) implantation. Laser peripheral iridotomy was the most reported but ineffective treatment in the literature., Methods: Retrospective, interventional case series of patients who developed PPB in Taipei Veterans General Hospital from 2017 to 2021. Clinical course, diagnostic methods, treatment and outcomes were recorded and discussed., Results: Four eyes of three patients were documented. All of them had diabetes and diabetic retinopathy. Anterior segment Optical coherence tomography (OCT) of these patients showed an exudative membrane at the peripapillary area while slit lamp image could not provide a clear view due to the severely edematous corneal condition. Laser peripheral iridotomy and yttrium aluminum garnet (YAG) laser aiming to the peripapillary exudation were applied to break the PPB successfully., Conclusion: Diabetes mellitus, intravitreal injection and inflammation are crucial risk factors for PPB. Anterior segment OCT can be a useful diagnostic tool for the detection of the peripapillary exudative membrane while corneal clarity is compromised due to high intraocular pressure. In addition to peripheral laser iridotomy, an effective approach to resolve PPB may be the use of the YAG laser to break the exudative membrane., Competing Interests: Declaration of Competing Interest All authors have declared no conflict of interest., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Objective: Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in young adults. Automated infrared pupillometry (AIP) has shown promising results in predicting neural damage in aneurysmal subarachnoid hemorrhage and ischemic stroke. We aimed to explore potential uses of AIP in triaging patients with TBI. We hypothesized that a brain injury severe enough to require an intervention would show Neurologic Pupil Index (NPI) changes., Methods: We conducted a prospective pilot study at a level-1 trauma center between November 2019 and February 2020. AIP readings of consecutive patients seen in the emergency department with blunt TBI and abnormal imaging findings on computed tomography were recorded by the assessing neurosurgery resident. The relationship between NPI and surgical intervention was studied., Results: Thirty-six patients were enrolled, 9 of whom received an intervention. NPI was dichotomized into normal (≥3) versus abnormal (<3) and was predictive of intervention (Fisher exact test; P < 0.0001). Six of the 9 patients had a Glasgow Coma Scale (GCS) score ≤8 and imaging signs of increased intracranial pressure (ICP) and underwent craniectomy (n = 4) or ICP monitor placement (n = 2) and had an abnormal NPI. Three patients underwent ICP monitor placement for GCS score ≤8 in accordance with TBI guidelines despite minimal imaging findings and had a normal NPI. The GCS score of these patients improved within 24 hours, requiring ICP monitor removal. NPI was normal in all patients who did not require intervention., Conclusions: AIP could be useful in triaging comatose patients after blunt TBI. An NPI ≥3 may be reassuring in patients with no signs of mass effect or increased ICP., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Postural tachycardia syndrome (PoTS) is a poorly understood disorder characterized by excessive tachycardia in the upright position. In addition, patients with PoTS often complain of non-postural symptoms, including fatigue, gastrointestinal and vasomotor fluctuations. The present study quantitatively assessed autonomic symptom burden in PoTS patients (n=32) using the COMPASS-31, compared to that of autonomic failure/neuropathy (AF/N; n=47) and asymptomatic, healthy controls (n=32). Using AIC model selection and regression analysis, we found differences in the contribution of individual COMPASS-31 domains, depending on the autonomic disorder. In PoTS, fatigue severity, orthostatic intolerance and pupillomotor symptom domains, contributed significantly to differences in COMPASS-31 scores compared to controls. In contrast, the secretomotor, gastrointestinal, bladder and vasomotor domains, contributed significantly to the AF/N model. Our results confirm an increase in autonomic symptoms across all functional domains in PoTS compared to controls, and with similar severity to AF/N, though with differing significant domain contributions. Our findings provide additional support that PoTS is indeed a syndrome of autonomic dysfunction beyond orthostatic intolerance, but also indicates the likelihood of disease-specific contributions to symptom burden, highlighting the need for application of expanded physiological assessment beyond orthostatic challenge, as well as disease-specific symptom assessment tools for use in PoTS., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: Infants are at risk for vitamin K deficiency bleeding (VKDB) because of limited stores of vitamin K (VK) at birth and a low concentration of VK in human breast milk. Therefore, the administration of intramuscular (IM) VK at birth has been recommended since 1961 in the United States. Infants who do not receive IM VK and who are exclusively breast-fed are at increased risk for VKDB. While VKDB is rare, a common presentation of late onset VKDB is intracranial hemorrhage., Case Report: We report the case of a 4-week-old infant who presented to the emergency department with lethargy and a grossly dilated right pupil. The parents denied trauma. A computed tomography scan revealed a right-sided subdural hematoma with midline shift. The infant's international normalized ratio was >10.9 and his prothrombin time PT was >120 seconds. VK was administered and the child was transferred to a tertiary care center for emergent neurosurgery. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: The difficult part of making this critical diagnosis is considering it. Any bleeding in a newborn without trauma should prompt inquiry regarding neonatal VK administration and a serum prothrombin time level. Fortunately, once the diagnosis is made, therapy in the emergency department can be lifesaving and is familiar to emergency physicians. Treatment parallels usual care for the adult with excess anticoagulation caused by warfarin. Prompt intravenous VK is universally accepted. Studies to support fresh frozen plasma or prothrombin complex concentrate are lacking but make good clinical sense for life-threatening bleeding., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Objective: The aim of this study was to analyse retinal nerve fibre layer (RNFL), pattern-reversal visual evoked potentials (pVEPs) and relative afferent pupillary defect (RAPD) changes in multiple sclerosis (MS) patients with the consideration of past optic neuritis (ON)., Methods: Ophthalmological, neurological, OCT, RNFL and pVEP studies were conducted in 59 MS patients. RAPD tests were performed in 47 of them. Control group consisted of 28 healthy volunteers., Results: Abnormal RNFL was found in 59% of cases of eyes with ON and 28% of eyes without ON. In eyes with ON, significantly lower RNFL values were indicated in the temporal and lower quadrants. Elongation of pVEP latency was found in 83% of eyes with ON and 60% of eyes without ON. The average value of pVEP latency was larger and the amplitude was lower in the subgroup of eyes with RNFL at the borderline or below the norm. RAPD was observed only in eyes with ON and with RNFL thinning. No association was found between the RAPD and pVEP parameters., Conclusions: VEPs were more frequently abnormal than RNFL in MS patients. RNFL damage in eyes without ON may indicate neurodegenerations in CNS of MS patients; it can also be the consequence of subclinical ON., Significance: An analysis of RNFL and VEP can be useful for evaluating the optic nerve in MS patients., (Copyright © 2015. Published by Elsevier Ireland Ltd.)

Purpose: To evaluate whether a chromatic pupillometry test can be used to detect impaired function of intrinsically photosensitive retinal ganglion cells (ipRGCs) in patients with primary open-angle glaucoma (POAG) and to determine if pupillary responses correlate with optic nerve damage and visual loss., Design: Cross-sectional study., Participants: One hundred sixty-one healthy controls recruited from a community polyclinic (55 men; 151 ethnic Chinese) and 40 POAG patients recruited from a glaucoma clinic (22 men; 35 ethnic Chinese) 50 years of age or older., Methods: Subjects underwent monocular exposure to narrowband blue light (469 nm) or red light (631 nm) using a modified Ganzfeld dome. Each light stimulus was increased gradually over 2 minutes to activate sequentially the rods, cones, and ipRGCs that mediate the pupillary light reflex. Pupil diameter was recorded using an infrared pupillography system., Main Outcome Measures: Pupillary responses to blue light and red light were compared between control subjects and those with POAG by constructing dose-response curves across a wide range of corneal irradiances (7-14 log photons/cm(2) per second). In patients with POAG, pupillary responses were evaluated relative to standard automated perimetry testing (Humphrey Visual Field [HVF]; Carl Zeiss Meditec, Dublin, CA) and scanning laser ophthalmoscopy parameters (Heidelberg Retinal Tomography [HRT]; Heidelberg Engineering, Heidelberg, Germany)., Results: The pupillary light reflex was reduced in patients with POAG only at higher irradiance levels, corresponding to the range of activation of ipRGCs. Pupillary responses to high-irradiance blue light associated more strongly with disease severity compared with responses to red light, with a significant linear correlation observed between pupil diameter and HVF mean deviation (r = -0.44; P = 0.005) as well as HRT linear cup-to-disc ratio (r = 0.61; P < 0.001) and several other optic nerve head parameters., Conclusions: In glaucomatous eyes, reduced pupillary responses to high-irradiance blue light were associated with greater visual field loss and optic disc cupping. In POAG, a short chromatic pupillometry test that evaluates the function of ipRGCs can be used to estimate the degree of damage to retinal ganglion cells that mediate image-forming vision. This approach could prove useful in detecting glaucoma., (Copyright © 2015 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Objective: To assess the accuracy of using pupillary light reflex (PLR) in detecting glaucoma., Clinical Relevance: Glaucoma is a specific disease of the optic nerve and is often more severe in 1 eye. When large enough, this asymmetry in disease severity can cause a relative afferent pupillary defect (RAPD). Better detection of RAPDs may be one way to identify persons with glaucoma., Methods: We searched Medline and Embase through June 2012 and searched bibliographies for relevant studies for additional references. Two authors independently reviewed all articles and selected studies that assessed PLRs in patients with glaucoma. We analyzed data using mixed-effect bivariate summary receiver operating characteristic meta-analysis models., Results: A total of 30 studies were included in this review. An RAPD was observed in 9% to 82% of patients with glaucoma. Eleven studies with a total of 7271 participants were included in the analysis, and the pooled estimate corresponded to a sensitivity of 0.63 (95% confidence interval [CI], 0.43-0.80) and a specificity of 0.93 (95% CI, 0.85-0.97). After excluding 2 studies that used the swinging flashlight test, the sensitivity increased to 0.74 (95% CI, 0.59-0.85) with a specificity of 0.85 (95% CI, 0.77-0.90). Study designs and different pupil measurement techniques explained part of the heterogeneity between studies., Conclusions: Patients with glaucoma frequently have an abnormal PLR and comparing the responses between the 2 eyes can in part distinguish between those with glaucoma and those without the disease. Newer instruments and analytic approaches to assess pupil function may improve the performance of pupil screening., (Copyright © 2013 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Objective: To develop an objective and precise neurophysiologic method from which to identify and characterize the presence and magnitude of relative afferent pupillary defects (RAPD) in patients with MS., Methods: Binocular infrared pupillometry was performed in 40 control subjects and 32 MS patients with RAPDs, using two precisely defined sequences of alternating light flashes (right-left and left-right). We analyzed three distinct pupillary metrics in response to light stimulation. These included percent diameter change (DC), constriction curve area (CCA), which measures change in diameter over time, and the phase-plane curve area (PCA) which measures change in diameter with change in velocity. Direct and consensual response ratios (for each eye) were computed and analyzed for each metric in response to both the first flash (i.e. first phase) and second flash (i.e. second phase) of the 'swinging flashlight' test., Results: Second flash pupillary response metric asymmetry ratios yielded the highest discriminatory power for RAPD detection. Receiver operating characteristic areas under the curve for each of the pupillary metric response asymmetry ratios were as follows: diameter change: 0.97; constriction curve area: 0.96; phase-plane curve area: 0.95 (p<0.0001 for all comparisons compared to normal subjects). The sum of these three squared ratios (SSR) yielded a combined metric with the greatest discriminatory power (receiver operator characteristic area under the curve=0.99)., Conclusions: Second flash (i.e. the second phase of the swinging light test) pupillary metric response asymmetry ratios are highly sensitive and specific for the confirmation and characterization of an RAPD in patients with MS. This objective neurophysiologic method may be useful for studying the relationship between a stereotyped reflex, and nervous system architecture, with potential ramifications for detecting and monitoring neuroprotective and restorative effects of novel agents in MS treatment trials., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Purpose: To describe the clinical characteristics of and risk factors for the development of optic neuropathy after pars plana vitrectomy (PPV) for macula-sparing primary rhegmatogenous retinal detachment (RRD) repair., Design: Retrospective case-control study., Participants: Seven patients who underwent PPV for macula-sparing primary RRD with subsequent development of optic neuropathy and 42 age- and gender-matched control patients undergoing PPV for macula-sparing primary RRD., Methods: Retrospective chart review of medical and surgical records., Main Outcome Measures: Clinical features of patients who developed optic neuropathy after PPV for macula-sparing RRD and analysis of potential risk factors (age, gender, medical history, surgical technique, intraoperative ocular perfusion pressure [OPP], and operative time)., Results: At last follow-up, all 7 patients with optic neuropathy had visual acuity less than 20/200, relative afferent pupillary defects, optic nerve pallor, and visual field defects. A total of 5 of 7 patients (71%) demonstrated intraoperative reduced OPP with associated systemic hypotension compared with 7 of 42 patients (17%) in the control cohort (P = 0.01)., Conclusions: Optic neuropathy after PPV for macula-sparing primary RRD is a rare but potentially devastating complication. Although the cause is often unclear, reduced ocular perfusion due to intraoperative systemic hypotension may be a contributing risk factor in some eyes., (Copyright © 2012 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Pupil size is determined by the interaction of the parasympathetic and the sympathetic nervous system. The parasympathetic system conducts the light reaction with its major center in the dorsal midbrain. The sympathetic nervous system acts either directly on the dilator muscle (peripherally) or centrally by inhibiting the Edinger-Westphal nucleus. Psychosensory reactions are transmitted via the sympathetic system. The afferent input of the light reflex system in humans is characteristically wired, allowing a detailed analysis of a lesion of the afferent input. Even in humans a subgroup of ganglion cells containing melansopsin plays an important role as a light sensor for the pupillary system. To diagnose normal pupillary function, pupils need to be isocoric and react bilaterally equally to light. Anisocoria indicates a problem of the efferent pupillary pathway. Pupillary disorders may involve the afferent pathways (relative afferent pupillary defect) or the efferent pathways. Physiological anisocoria is a harmless condition that has to be distinguished from Horner's syndrome. In this case pharmacological testing with cocaine eye-drops is helpful. Disorders of the parasympathetic system will impair the light response. They include dorsal midbrain syndrome, third-nerve palsy, and tonic pupil. Tonic pupils are mainly idiopathic and do not need imaging. Disorders of the iris, including application of cholinergic agents, need also to be considered in impaired pupillary light reaction., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Objective: To identify clinical and pupillographic features of patients with a relative afferent pupillary defect (RAPD) without visual acuity or visual field loss caused by a lesion in the dorsal midbrain., Design: Experimental study., Participants and Controls: Four patients with a dorsal midbrain lesion who had normal visual fields and a clinically detectable RAPD., Methods: The pupil response from full-field and hemifield light stimulation over a range of light intensities was measured by computerized binocular pupillography., Main Outcome Measures: The mean of the direct and consensual pupil response to full-field and hemifield light stimulation was plotted as a function of stimulus light intensity., Results: All 4 subjects showed decreased pupillographic responses at all intensities to full-field light stimulation in the eye with the clinical RAPD. The pupillographic responses to hemifield stimulation showed a homonymous pattern of deficit on the side ipsilateral to the RAPD, similar to that observed in a previously reported patient with an optic tract lesion., Conclusions: The basis of a midbrain RAPD is the nasal-temporal asymmetry of pupillomotor input that becomes manifest when a unilateral postchiasmal lesion interrupts homonymously paired fibers traveling in the contralateral optic tract or midbrain pathway to the pupillomotor center, respectively. The pupillographic characteristics of an RAPD resulting from a dorsal midbrain lesion thus resemble those of an RAPD resulting from a unilateral optic tract lesion, but without the homonymous visual field defect., Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article., (Copyright 2010 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Pupillometry is a non-invasive technique, based on well-established neurophysiologic principles, that can be utilized to objectively characterize pathophysiologic demyelinating and neurodegenerative changes involving the pupillary reflex pathway. In animal models of human disorders, pupillometry derived reflex metrics could potentially be used to longitudinally monitor disease activity and responses to pharmacotherapies. These investigations would have important implications for translational initiatives focused on the identification and application of novel neuroprotective and restorative treatments for human diseases such as multiple sclerosis. Here, we have established normal reference values for various pupillary reflex metrics across different mouse strains. Ultimately, we anticipate that this new data will help to catalyze unique lines of inquiry using pupillometry methods.

Objective: To estimate the magnitude and causes of visual impairment (VI) in people aged > or = 50 years in Kunming using the Rapid Assessment for Avoidable Blindness methodology, and to assess the prevalence of a pupillary defect in participants diagnosed as cataract visually impaired., Design: Population-based cross-sectional survey., Participants: We enrolled 2760 residents of Kunming prefecture in southwest China, >50 years of age., Methods: Forty-six clusters of 60 people were selected based on population proportional to size. Households from each cluster were selected using compact segment sampling (CSS) or quota sampling when CSS was not feasible. Visual acuity (VA) was assessed using a tumbling E chart. Lens status and cause of VI were determined by ophthalmologists using direct ophthalmoscopy through a dilated pupil where necessary. The pupillary reaction was assessed on undilated pupils when VI was detected., Main Outcome Measures: Prevalence of blindness (VA<3/60), severe VI (SVI) (VA<6/60), and VI (VA<6/18) using presenting VA (PVA). The causes of blindness and VI and prevalence of a pupillary defect in the cataract visually impaired were also assessed., Results: Of 2760 enumerated residents, 2588 were examined. The sample prevalence of bilateral blindness was 3.7% (95% confidence interval [CI], 2.8-4.6%). The prevalence of SVI was 3.0% (95% CI, 2.2-3.8%), and of VI was 9.1% (95% CI, 7.5-10.7%). The main cause of blindness was cataract (63.2% of blindness), followed by nontrachomatous corneal scar (14.7%), glaucoma (7.4%), and other posterior segment disease/neurologic disorders (4.2%). A pupillary defect was detected in 16% of those diagnosed with cataract VI. The cataract surgical coverage in the bilaterally blind was 58.9%, and 45% of operated eyes had good outcome with available correction (VA>6/18). The main barrier to cataract surgery was cost., Conclusions: Cataract remains the most important cause of preventable blindness in this poor region of China, and affordable provision of surgery would help to address this problem. Some cases of cataract blindness may not be preventable owing to preexisting comorbidity, as detected by the presence of a pupillary defect.

Background: The neuroimaging evaluation of isolated third nerve palsy in adults remains controversial. We aim to define diagnostic yield for neuroimaging of third nerve palsy (TNP) by degree of internal and external dysfunction using previously published imaging guidelines., Methods: All cases of TNP evaluated at a tertiary care center between 1990 and April 2004 were reviewed. Inclusion criteria were neurologically isolated TNP in adults with adequate documentation of the ocular examination, neuroimaging, and follow-up. Exclusion criteria were neurologically non-isolated TNP, TNP occurring in children, and TNP secondary to a known etiology; lack of adequate follow-up; and insufficient documentation of the ocular exam. Published imaging guidelines based on degree of external and internal dysfunction were applied to our cohort to determine compliance with and the diagnostic yield of neuroimaging recommendations., Results: One hundred and eight cases were reviewed. Of the 91 excluded cases, there were 14 cases of aneurysm or subarachnoid hemorrhage. Of the 17 included cases, presumed ischemia (10), aneurysm (2), and ocular myasthenia (3) were the most common causes of isolated TNP. Neuroimaging was performed in 16 cases (94.1%). The neuroimaging strategy was concordant with neuroimaging recommendations in 7 cases (41.2% concordance). Failure to perform noninvasive angiography accounted for 7 cases (70.0%) of nonconcordance. The diagnostic yield of all neuroimaging studies performed was 68.8%; diagnostic yield in cases concordant with published neuroimaging recommendations was 100%., Interpretation: The degree of external and internal dysfunction can direct the type of neuroimaging performed in TNP.

Although diabetic autonomic neuropathy involves most organs, diagnosis is largely based on cardiovascular tests. Light reflex pupillography (LRP) non-invasively evaluates pupillary autonomic function. We tested whether LRP demonstrates autonomic pupillary dysfunction in diabetics independently from cardiac autonomic neuropathy (CAN) or peripheral neuropathy (PN). In 36 type-II diabetics (39-84 years) and 36 controls (35-78 years), we performed LRP. We determined diameter (PD), early and late re-dilation velocities (DV) as sympathetic parameters and reflex amplitude (RA) and constriction velocity (CV) as parasympathetic pupillary indices. We assessed the frequency of CAN using heart rate variability tests and evaluated the frequency of PN using neurological examination, nerve conduction studies, thermal and vibratory threshold determination. Twenty-eight (77.8%) patients had abnormal pupillography results, but only 20 patients (56%) had signs of PN or CAN. In nine patients with PN, only pupillography identified autonomic neuropathy. Four patients had pupillary dysfunction but no CAN or PN. In comparison to controls, patients had reduced PD, late DV, RA and CV indicating sympathetic and parasympathetic dysfunction. The incidence and severity of pupillary abnormalities did not differ between patients with and without CAN or PN. LRP demonstrates sympathetic and parasympathetic pupillary dysfunction independently from PN or CAN and thus refines the diagnosis of autonomic neuropathy in type-II diabetics.

Objective: To report a case of bilateral optic neuropathy after bilateral laser-assisted in situ keratomileusis (LASIK) surgery., Design: Observational case report., Methods: Complete eye examination with detailed evaluation of the optic nerve, detailed medical history, stereo disc photographs, GDx Nerve Fiber Analyzer testing, Humphrey 24-2 SITA visual field testing, diurnal intraocular pressure measurement, serologic evaluation, and magnetic resonance imaging of the brain and orbits., Main Outcome Measures: Optic nerve status, visual field status, and visual acuity., Results: A subject with previously healthy optic nerves had bilateral optic neuropathy develop after LASIK surgery. This neuropathy manifested with a subjective decrease in visual field, normal visual acuity, normal color vision, relative afferent pupillary defect, increased cupping of the optic nerve with focal neuroretinal rim defects, decreased nerve fiber layer thickness, and nerve fiber bundle-type visual field defects. The subject had no other risk factors for optic neuropathy. No other cause of neuropathy was identified., Conclusions: Optic neuropathy is a potential vision-threatening complication of LASIK surgery. This complication may be due to barotrauma or ischemia related to extreme elevation of intraocular pressure by the suction ring. Careful examination of the optic nerve before and after LASIK surgery is warranted.

Objective: To investigate the ability of a portable, personal computer-driven, pupillometer to record the pupillary response curve during the swinging flashlight test. Also, to determine whether these response curves can be used to identify and quantify relative asymmetry in the pupillary light reflex between eyes in healthy volunteers with simulated afferent pupil defects (APDs) and patients with optic neuropathies., Design: Comparative, observational case series and instrument validation., Participants: Healthy volunteers with no known ocular disease and patients (n = 20) with various optic neuropathies noted to have relative APDs on examination., Methods: Pupillary response curves of the right eye were recorded with a portable, electronic, infrared pupillometer from healthy volunteers (with and without simulated APDs) and patients with APDs while the light stimulus alternated between eyes, simulating the swinging flashlight test. Simulated APDs in healthy volunteers were created with increasingly dense neutral density filters in front of the left eye., Main Outcome Measures: Differences in constriction amplitude, latency, and constriction velocity of the pupillary response with right eye stimulation versus left eye stimulation in both groups of subjects., Results: A significant correlation between neutral density filter strength and intereye differences was seen for all measurement parameters in volunteers with simulated APDs. Depending on the measurement parameter and stimulus intensity, simulated APDs of 0.6 log units or more could be distinguished from normal responses. Clinically graded true APDs had intereye differences similar to simulated APDs of the same density. Those with real and simulated APDs of 0.9 log units or more could be distinguished from healthy volunteers with 80% sensitivity and 92% specificity. Responses from those with real and simulated small APDs of 0.3 to 0.6 log units could not be distinguished reliably., Conclusions: Portable, personal-computer driven, electronic, infrared pupillography can record the swinging flashlight test accurately and identify large afferent pupillary defects. An affordable, portable, reliable device for identifying relative APDs would be useful in the identification and follow-up of patients with neurogenic vision loss.

Objective: The authors compared two methods, the Marcus Gunn test and the alternating light test, for detecting a relative afferent pupillary defect., Design: A randomized, prospective clinical trial., Participants: Fourteen patients with unilateral optic neuropathy., Intervention: The Marcus Gunn and alternating light tests were performed on each patient., Main Outcome Measures: The results of the Marcus Gunn and altemating light tests for detecting a relative afferent pupillary defect on the affected side., Results: The Marcus Gunn test was able to identify the affected eye in only 8 of 14 patients, whereas the alternating light test correctly identified the affected eye in 13 of 14 patients. Results of the Marcus Gunn test were indeterminate in 4 of 14 patients and were incorrect in 2 of 14 patients. Results of the alternating light test were indeterminate in one patient and never incorrectly identified the affected eye., Conclusion: The alternating light test is superior to the Marcus Gunn test for detecting relative afferent pupillary defects.