Night vision in a case of vitamin A deficiency due to malabsorption

Vitamin A deficiency retinopathy related to medical interventions in a Swiss cohort: a case series

AIMS OF THE STUDY

Vitamin A deficiency retinopathy is a potentially blinding disease. In developed countries, vitamin A deficiency due to malnutrition is rare. However, vitamin A deficiency can be caused by malabsorption resulting from bowel resection or medication. In this retrospective study, we present five cases of vitamin A deficiency retinopathy related to malabsorption secondary to medical interventions.

METHODS

Electronic charts over a ten-year period (2012-2022) were screened for vitamin A deficiency retinopathy. Only patients with vitamin A deficiency confirmed by laboratory tests were included. Symptoms, medical history, visual acuity, optical coherence tomography, fundus autofluorescence, electrophysiological examination, and vitamin A levels were reviewed.

RESULTS

Five eligible cases were identified. Median age was 44.7 years (range 22.2-88.9), median duration of ocular symptoms prior to diagnosis was 14 months, and median visual acuity was 1.0 (range 0.5-1.0, Snellen, decimal). Three patients had a history of bariatric surgery, one patient had a small bowel resection and was on octreotide treatment, and one patient suffered from cystic fibrosis and had a history of small bowel resection and severe hepatopathy. Optical coherence tomography showed various abnormalities, including a reduced interdigitation zone, subretinal drusenoid deposits, and a thinned outer nuclear layer. Electroretinogram findings ranged from abnormal oscillatory potentials to non-recordable rod responses.

CONCLUSIONS

Vitamin A deficiency retinopathy can occur following medical interventions associated with malabsorption. In cases of night blindness, vitamin A levels should be measured.

Vitamin A deficiency and the retinal "double carrot" sign with optical coherence tomography

BACKGROUND

Spectral-domain optical coherence tomography (SD-OCT) and full-field electroretinography (ERG) allow retinal assessment with vitamin A deficiency (VAD). Using SD-OCT, this study aimed to characterize and follow a novel retinal abnormality in patients with VAD and intramuscular supplementation.

METHODS

Patients with VAD were retrospectively reviewed, including SD-OCT and electroretinography.

RESULTS

Three patients had VAD following bariatric or colon surgery and varying supplementation. All had nyctalopia, extinguished scotopic rod-specific function with ERG, and decreased serum vitamin A. None demonstrated surface abnormalities. All received intramuscular vitamin A with subjective resolution of symptoms. On SD-OCT, four of six eyes exhibited homogenous foveal hyperreflectivity anterior to retinal pigment epithelium-Bruch complex, reminiscent of a "double carrot", which improved following supplementation. ERG findings demonstrated improved scotopic rod-specific function in all cases; however, photopic function remained diminished in two cases.

CONCLUSIONS

Structural improvement of the proposed "double carrot" sign occurs soon after vitamin A supplementation. While scotopic function improves rapidly following supplementation, cone function recovers more slowly. Therefore, foveal changes such as the "double carrot" sign suggest that structural recovery of cones precedes functional recovery.

Serial ERG monitoring of response to therapy in vitamin A deficiency related night blindness

Two male patients with known systemic disorders who presented with complaints of nyctalopia underwent a complete ophthalmic examination including electrophysiological evaluation and serum vitamin A (retinol) levels. A significant vitamin A deficiency was detected, supplementation started and repeat electroretinogram (ERG) testing was carried out to monitor the timeline of recovery. Restoration of rod and generalised cone function was rapid within the first week of receiving treatment and near normal recovery was seen after 1 month of supplementation. Serial monitoring of ERG changes in vitamin A deficiency (VAD) associated night blindness plays an important role to demonstrate functional recovery post-treatment. The different effects of VAD on rod and cone function, and their rate of recovery, may reflect differences in the visual cycle between the two photoreceptors. We report the serial ERG changes in VAD related night blindness secondary to intestinal lipofuscinosis and liver cirrhosis in two patients.

Xerophthalmia with secondary malabsorption syndrome in a young lady

Delayed recognition and treatment of vitamin A deficiency (VAD) in adults leads to devastating complications. A 24-year-old woman presented with diarrhea, malaise, and shortness of breath. Her medical history included blunt abdominal trauma for which, she had bowel resection surgery and revision surgery within a year of the last surgery at the age of 8 years. She had difficulty in night vision and dry eyes. The best-corrected visual acuity was 6/18 in the BE. On slit-lamp examination in the both eyes (BE), the conjunctiva was thick, dry-looking with wrinkling, and the cornea had diffused superficial punctate keratitis and in the left eye, there was corneal xerosis of 1.5 × 1.5 mm. Tear film breakup time was 0-s in the BE. Schirmer's were 30 mm BE. The rest of the ocular examination was within normal limits. A clinical diagnosis of xerophthalmia secondary to malabsorption was made and treated with systemic vitamin A and intense lubrication. With time, ophthalmic conditions improved, but she died due to poor general wellbeing and repeated hospital-acquired infections. The infrequent presentation of VAD in adults and the unusual etiology in this patient make this case interesting, whereas its potentially devastating consequences highlight the importance of its early recognition, treatment, and regular follow up needed by both patient and physician in the community (general practitioner and ophthalmologists) for the prevention of VAD complications and poor prognosis.

Vitamins are Indeed Vital Amines: A Discussion of 3 Deficiencies With Neurologic Manifestations

Optimal functioning of the human nervous system depends on a constant supply of nutrients, vitamins, and minerals. In the developed world, nutritional deficiencies are relatively rare and infrequently present with neurologic manifestations. These neurologic disorders can be mistaken for inflammatory and/or autoimmune phenomena. This manuscript describes 2 pediatric cases with neurologic signs/symptoms arising from vitamin deficiencies-(1) optic neuropathy and (2) Wernicke encephalopathy associated with a Guillain-Barre-like pattern of weakness. The 2 cases and the subsequent discussion of vitamin A, B1, and B12 deficiencies underscore the value of taking a thorough dietary history and emphasize risk factors for these 3 nutritional deficiencies.

Verifying complaints of difficulties in night vision using electroretinography and dark adaptation tests

PURPOSE

To determine the electroretinographical and psychophysical parameters that can help to verify patients' complaints of reduced night vision.

METHODS

We tested 275 consecutive patients with normal appearing fundi, complaining of visual difficulties at night, using flash electroretinography (ERG) and dark adaptation (DA) test. Two ERG parameters were used to assess a scotopic retinal function: the amplitude of the response to dim blue flash (the rod response) and the b-wave ratio (measured/expected). Dark adaptation was measured with green- and red-light stimuli after exposure to a bright, bleaching light. The psychophysical parameter of night vision was defined as the threshold for detection of the blue-green stimulus that was measured after 40-45 min in complete darkness.

RESULTS

Fifty-five patients were excluded from the analysis because of a discrepancy between the two ERG parameters in assessment of scotopic retinal function. The remaining 220 patients were divided into 4 groups: (1) normal ERG and normal DA, (2) subnormal ERG and subnormal DA, (3) normal ERG and subnormal DA and (4) subnormal ERG and normal DA. The ERG and DA tests supported the complaint of visual difficulties at night in 67 patients (group 2), while 34 patients were characterized as having normal scotopic visual function (group 1). The other 119 patients (groups 3 and 4) presented a diagnostic dilemma because one test (ERG or dark adaptation) showed normal scotopic function, while the other indicated subnormal scotopic function.

CONCLUSION

Our findings indicate that ERG is an essential, but not sufficient test for verifying patient's complaint on visual difficulties in the dark. We suggest using both electroretinography and psychophysical dark adaptation to test patients complaining of reduced night vision.

REVERSIBLE NYCTALOPIA ASSOCIATED WITH VITAMIN A DEFICIENCY AFTER RESECTED MALIGNANT ILEAL CARCINOID AND PANCREATIC ADENOCARCINOMA

PURPOSE

To describe the rapid time course of visual and electroretinographic recovery from vitamin A deficiency in a patient with a history of multiple resected abdominal tumors, including ileal carcinoid and pancreatic adenocarcinoma.

METHODS

A 61-year-old white man with a history of resected malignant ileal carcinoid and Stage III pancreatic adenocarcinoma referred with complaints of 6 weeks of difficulty with night vision.

RESULTS

Initial testing showed significantly reduced scotopic rod responses in both eyes and decreased vitamin A levels and a normal cancer-associated retinopathy laboratory panel. He had complete recovery of both his symptoms and full-field electroretinography within 5 days of starting intramuscular vitamin A.

CONCLUSION

Vitamin A deficiency-related retinopathy after abdominal surgery may be an underreported complication. This case provides a unique clinical perspective in our patient with a history of ileal carcinoid and Stage III pancreatic adenocarcinoma and confirms that rapid symptomatic and electroretinographic recovery is possible with appropriate treatment.

The morphology of human rod ERGs obtained by silent substitution stimulation

Purpose

To record transient ERGs from the light-adapted human retina using silent substitution stimuli which selectively reflect the activity of rod photoreceptors. We aim to describe the morphology of these waveforms and examine how they are affected by the use of less selective stimuli and by retinal pathology.

Methods

Rod-isolating stimuli with square-wave temporal profiles (250/250 ms onset/offset) were presented using a 4 primary LED ganzfeld stimulator. Experiment 1: ERGs were recorded using a rod-isolating stimulus (63 ph Td, rod contrast, C_rod = 0.25) from a group (n = 20) of normal trichromatic observers. Experiment 2: Rod ERGs were recorded from a group (n = 5) using a rod-isolating stimulus (C_rod = 0.25) which varied in retinal illuminance from 40 to 10,000 ph Td. Experiment 3: ERGs were elicited using 2 kinds of non-isolating stimuli; (1) broadband and (2) rod-isolating stimuli which contained varying degrees of L- and M-cone excitation. Experiment 4: Rod ERGs were recorded from two patient groups with rod monochromacy (n = 3) and CSNB (type 1; n = 2).

Results

The rod-isolated ERGs elicited from normal subjects had a waveform with a positive onset component followed by a negative offset. Response amplitude was maximal at retinal illuminances <100 ph Td and was virtually abolished at 400 ph Td. The use of non-selective stimuli altered the ERG waveform eliciting more photopic-like ERG responses. Rod ERGs recorded from rod monochromats had similar features to those recorded from normal trichromats, in contrast to those recorded from participants with CSNB which had an electronegative appearance.

Conclusions

Our results demonstrate that ERGs elicited by silent substitution stimuli can selectively reflect the operation of rod photoreceptors in the normal, light-adapted human retina.

Rod Electroretinograms Elicited by Silent Substitution Stimuli from the Light-Adapted Human Eye

PURPOSE

To demonstrate that silent substitution stimuli can be used to generate electroretinograms (ERGs) that effectively isolate rod photoreceptor function in humans without the need for dark adaptation, and that this approach constitutes a viable alternative to current clinical standard testing protocols.

METHODS

Rod-isolating and non-isolating sinusoidal flicker stimuli were generated on a 4 primary light-emitting diode (LED) Ganzfeld stimulator to elicit ERGs from participants with normal and compromised rod function who had not undergone dark-adaptation. Responses were subjected to Fourier analysis, and the amplitude and phase of the fundamental were used to examine temporal frequency and retinal illuminance response characteristics.

RESULTS

Electroretinograms elicited by rod-isolating silent substitution stimuli exhibit low-pass temporal frequency response characteristics with an upper response limit of 30 Hz. Responses are optimal between 5 and 8 Hz and between 10 and 100 photopic trolands (Td). There is a significant correlation between the response amplitudes obtained with the silent substitution method and current standard clinical protocols. Analysis of signal-to-noise ratios reveals significant differences between subjects with normal and compromised rod function.

CONCLUSIONS

Silent substitution provides an effective method for the isolation of human rod photoreceptor function in subjects with normal as well as compromised rod function when stimuli are used within appropriate parameter ranges.

TRANSLATIONAL RELEVANCE

This method of generating rod-mediated ERGs can be achieved without time-consuming periods of dark adaptation, provides improved isolation of rod- from cone-based activity, and will lead to the development of faster clinical electrophysiologic testing protocols with improved selectivity.

Treatment of vitamin A deficiency retinopathy with sublingual vitamin A palmitate

PURPOSE

To report treatment of vitamin A deficiency retinopathy with sublingual vitamin A drops.

METHODS

Case report with review of the literature.

RESULTS

A 69-year-old Caucasian woman with a history of small bowel resection presented with progressive symptoms of bilateral nyctalopia and decreased visual acuity. Ophthalmic examination revealed bilateral conjunctival xerosis and fine white granular deposits in the midperipheral retina suggestive of vitamin A deficiency. Full-field electroretinogram (ERG), multifocal ERG (mfERG), and two-color dark adaptometry revealed significant impairment of rod and cone photoreceptor function. Kinetic perimetry demonstrated depressed macular sensitivity with constriction of the finer isopters. After 5 months of treatment with sublingual vitamin A drops, the patient's vision, ERG, mfERG, dark adaptometry, and perimetry normalized. A review of the literature summarizing the electrophysiologic testing in vitamin A deficiency is also discussed.

CONCLUSIONS

This case highlights novel observations on the effects of sublingual vitamin A supplementation for acquired vitamin A deficiency retinopathy. Sublingual vitamin A may represent a viable and efficacious treatment modality for vitamin A deficiency.

Recurrent episodes of night blindness in a patient with short bowel syndrome

PURPOSE

To describe clinical characteristics in a patient with recurrent episodes of night blindness due to vitamin A deficiency caused by short bowel syndrome in Crohn disease.

METHODS

Retrospective analysis of best-corrected visual acuity (BCVA), kinetic perimetry, slit-lamp biomicroscopy, ophthalmoscopy, fundus photography, fundus autofluorescence (FAF), spectral domain optical coherence tomography (SD-OCT), dark adaptometry (DA) and electroretinography (ERG). Serum vitamin A level was measured.

RESULTS

A 44-year-old man with a 3-year history of night blindness suffered from a short bowel syndrome with chronic malabsorption due to ileocecal resection in Crohn disease. Both eyes had a BCVA of 0.9, Bitot's spots of the conjunctiva and no significant fundus abnormalities. SD-OCT showed no remarkable changes, whereas FAF was brighter than normal in the center of the fovea. DA showed normal cone and a lack of rod function. The dark-adapted 0.01 ERG was non-detectable, the dark-adapted 3.0 ERG severely diminished, but the light-adapted 3.0 and 30 Hz flicker ERGs were within normal limits. Serum vitamin A level was 0.11 µg/ml (normal 0.30-0.65 µg/ml). Treatment with intravenous vitamin A caused a rapid recovery of night vision and ERG. However, during the following 3 years, he had three further episodes of night blindness with loss of rod function. During each period, parenteral vitamin A substitution brought complete recovery of night vision and rod function. BCVA, fundus, FAF findings and SD-OCT remained unchanged during the course.

CONCLUSIONS

In patients with known chronic malabsorption serum vitamin A level should be regularly checked to avoid recurrent night blindness episodes. ERG might be more sensitive than serum vitamin A level and is recommended in case of night blindness but still normal vitamin A level.

Electrophysiological and microperimetry changes in vitamin A deficiency retinopathy

PURPOSE

To describe a follow-up case of vitamin A deficiency (VAD)-related retinopathy with macular involvement monitored with electroretinography and microperimetry.

METHODS

Flash (ERG), pattern (PERG), and multifocal (mfERG) electroretinography were recorded in parallel with microperimetry before and during 7-month follow-up of vitamin A treatment on a 65-year-old man presented with a 1-year history of night blindness. The patient had undergone ileostomy procedure for Crohn's disease 14 years ago. His best corrected visual acuity was 6/6 in each eye. Fundus examination revealed macular and mid-peripheral yellow-white lesions compatible with drusen.

RESULTS

Before treatment, PERG was reduced, and mfERG was reduced and delayed, worse in responses from the central rings. These results revealed evidence of bilateral macular and central cone dysfunction. The flash ERG showed reduced dark-adapted 0.01 ERG (rod response); a-wave of dark-adapted 3.0 and 10.0 ERG was normal but b-wave was reduced (negative configuration); light-adapted 3.0 ERG was slightly reduced. The flash ERG revealed evidence of bilateral generalised retinal dysfunction affecting the rod more than cone system. Microperimetry showed deep reduction in retinal sensitivity. Fixation stability was unstable with eccentric locus. During treatment, ERG and microperimetry demonstrated significant improvements. Fixation stability reached normal values after the third treatment week.

CONCLUSIONS

This case illustrates the importance of electrophysiological investigation in early VAD-related retinopathy detection correlated with microperimetry. Our findings indicate a more delayed central cone function recovery than that of generalised rod and cone function. There was a marked correlation between ERG and microperimetric changes.

Incidence of low vitamin A levels and ocular symptoms after Roux-en-Y gastric bypass

BACKGROUND

Previous reports have demonstrated a significant incidence of fat-soluble vitamin deficiency after bariatric surgery. The purpose of the present study was to determine the incidence of vitamin A deficiency after Roux-en-Y gastric bypass and to correlate the laboratory findings with ocular symptoms potentially related to vitamin A deficiency.

METHODS

All patients who had undergone Roux-en-Y gastric bypass were invited to participate in a nutritional screening. The patients completed a detailed survey concerning ocular symptoms and had their vitamin A level evaluated.

RESULTS

A low vitamin A level was identified in 7 (11%) of 64 RYBG patients. Ocular xerosis was present in 18 patients (27%), with night vision changes reported in 45 (68%). Visual disturbances were present in 7 patients (11%) found to have low vitamin A levels, with hypovitaminosis A present in 22% of patients with xerosis (P <.05).

CONCLUSION

Low vitamin A levels and frequent ocular complaints that might be associated with decreased vitamin A are common findings in the post-RYBG patient population. Additional study is needed to assess the role of routine vitamin A screening and replacement in the postbariatric surgery patient.

ERGs in children with pancreatic enzyme insufficient and pancreatic enzyme sufficient cystic fibrosis

OBJECTIVES

We recorded scotopic and photopic flash electroretinograms (ERGs) in pediatric subjects with cystic fibrosis, aged 4 to 18 years, who were either pancreatic insufficient (PI) or pancreatic sufficient (PS). The aim of the study was to determine whether vitamin supplementation in the PI group allowed comparable retinal function in these two groups.

METHODS

ERGs were recorded from a mixed-gender group of 41 children and adolescents (4 to 17 years of age) with cystic fibrosis. The subjects were grouped according to pancreatic function into PI (n = 29) and PS (n = 12). Full-field flash ERGs were recorded from one eye using a DTL fiber. The pupil was dilated prior to recording using two drops of 0.5% tropicamide. ISCEV photopic and scotopic stimuli and recording conditions were used. Serum levels of vitamin A, beta carotene and retinol binding protein (RBP) were measured on the day of ERG recording.

RESULTS

There was no significant difference in ERG amplitudes or implicit times between PI and PS groups. Vitamin A, beta carotene, and RBP levels were not significantly different across the two groups and were not correlated with implicit times or amplitudes of any of the ERG types recorded here.

CONCLUSION

Similarity of ERGs across the PI and PS cystic fibrosis patient populations tested here suggests that the supplementation protocol applied to these populations allows similar levels of retinal function (as indicated by flash ERG parameters) in the two groups.

Macular and serum carotenoid concentrations in patients with malabsorption syndromes

The carotenoids lutein and zeaxanthin are believed to protect the human macula by absorbing blue light and quenching free radicals. Intestinal malabsorption syndromes such as celiac and Crohn’s disease are known to cause deficiencies of lipid-soluble nutrients. We hypothesized that subjects with nutrient malabsorption syndromes will demonstrate lower carotenoid levels in the macula and blood, and that these lower levels may correlate with early-onset maculopathy. Resonance Raman spectrographic (RRS) measurements of macular carotenoid levels were collected from subjects with and without a history of malabsorption syndromes. Carotenoids were extracted from serum and analyzed by high performance liquid chromatography (HPLC). Subjects with malabsorption (n = 22) had 37% lower levels of macular carotenoids on average versus controls (n = 25, P < 0.001). Malabsorption was not associated with decreased serum carotenoid levels. Convincing signs of early maculopathy were not observed. We conclude that intestinal malabsorption results in lower macular carotenoid levels.

Vitamin and mineral deficiencies in the developed world and their effect on the eye and vision

Vitamin and mineral deficiencies are common in developing countries, but also occur in developed countries. We review micronutrient deficiencies for the major vitamins A, cobalamin (B(12)), biotin (vitamin H), vitamins C and E, as well as the minerals iron, and zinc, in the developed world, in terms of their relationship to systemic health and any resulting ocular disease and/or visual dysfunction. A knowledge of these effects is important as individuals with consequent poor ocular health and reduced visual function may present for ophthalmic care.

Clinical disorders affecting mesopic vision

Vision in the mesopic range is affected by a number of inherited and acquired clinical disorders. We review these conditions and summarize the historical background, describing the clinical characteristics alongside the genetic basis and molecular biological mechanisms giving rise to rod and cone dysfunction relevant to twilight vision. The current diagnostic gold standards for each disease are discussed and curative and symptomatic treatment strategies are summarized.

Vitamin A deficiency in patients with a remote history of intestinal surgery

BACKGROUND/AIMS

Vitamin A deficiency, often presenting with nyctalopia, has been described in a number of patients with malabsorption as a result of intestinal bypass surgery and, more recently, bariatric surgery. In these reports vitamin A deficiency developed within several years of gastric or intestinal surgery. Three patients who developed decreased vision from vitamin A deficiency more than 18 years after their intestinal surgery are reported.

METHODS

A retrospective review of the clinical findings of all patients diagnosed with vitamin A deficiency, as confirmed by serological testing, over the past year in a single neuro-ophthalmic practice.

RESULTS

Four patients with vitamin A deficiency were seen, three of whom had intestinal surgery more than 18 years before the development of visual symptoms.

CONCLUSION

The authors suggest that vitamin A deficiency should be suspected in patients with unexplained decreased vision and a history of intestinal surgery, regardless of the timing of the surgical procedure.

Functional observations in vitamin A deficiency: diagnosis and time course of recovery

AIMS

To describe the effects of vitamin A deficiency (VAD) on retinal function and the subsequent recovery following treatment in three patients with systemic conditions (two with Crohn disease; one secondary to IgE syndrome).

METHODS

Electrophysiological testing (including pattern electroretinogram, PERG; electroretinogram, ERG; visual-evoked potential) established the diagnosis of VAD. Repeat testing was carried out in two patients to monitor the time course of recovery following intramuscular vitamin A injection. The third patient had repeat recordings following 13 months of oral supplementation.

RESULTS

All three patients initially displayed a characteristic absence of rod function associated with VAD. In addition, delayed and reduced amplitude cone ERGs, loss of short wavelength cone (S-cone) function and subnormal macular function were observed in two patients. Restoration of rod and generalised cone function was rapid in the two patients who received intramuscular injection, with normalisation of some electrophysiological responses after only 3 days. Normal S-cone amplitudes and cone latencies were reached within 12 days of vitamin A injection. Macular function returned to within normal limits by 12 days postinjection in one patient, but remained mildly subnormal in the second patient. Full recovery was present after 13 months oral supplementation in the third patient.

CONCLUSIONS

Novel observations regarding dark-adapted cone function, S-cone function, and PERG are presented. The differences between the effects of VAD on rod and cone function, and their rate of recovery, may reflect differences in the visual cycle between the two photoreceptor classes. The importance of rapidly and accurately diagnosing VAD, a treatable condition, is noted.

Role of electroretinography in the assessment of retinal function as an indicator of vitamin A status

Hypovitaminosis A is associated with exocrine pancreatic insufficiency in cystic fibrosis. Peripheral retinal dysfunction is an early finding of vitamin A deficiency. We evaluated serum retinol and zinc as well as visual adaptation in 41 patients with cystic fibrosis, receiving generous pancreatic enzyme and micronutrient supplementation. Forty-one normal individuals matched for age and sex served as controls. Peripheral retinal function was measured by clinical electroretinography using an Electrophysiologic Personal Interfaced Computer and applying a standard protocol. Serum retinol in cystic fibrosis was significantly lower than that of the control group (0.30+/-0.01 versus 0.39+/-0.02 mg/l, p<0.001). Serum zinc concentrations were normal in the cystic fibrosis group (1.21+/-0.03 mg/l) and significantly higher than that of the control group (1.02+/-0.01 mg/l, p<0.001). The overall visual adaptation, however, was found to be normal and comparable in the two groups. It is concluded that, in cystic fibrosis, despite appropriate vitamin A supplementation, retinol serum concentration may be low. As serum retinol does not reflect vitamin A status, evaluation of visual adaptation may be a more appropriate way to monitor for vitamin A deficiency in cystic fibrosis.

Electrophysiology in the investigation of acquired retinal disorders

Electrophysiological research on acquired retinal disorders, both common and rare, is reviewed. Age is a major factor influencing electroretinogram (ERG) and electro-oculogram (EOG) findings. Bipolar or Müller cell death in the aging retina could account for much of the amplitude decline that is observed with age. In diabetic retinopathy, the oscillatory potentials can monitor the progression of the disease and indicate neuronal alterations rather than diabetic angiopathy of the retina. Human ERG studies on glaucoma concentrated on ERG measures that are dominated by inner retinal contributions. It has been shown that the pattern ERG can serve as a predictor of ocular hypertension's progression to glaucoma. In retinal disorders caused by endogenous intoxication, such as hepatic retinopathy, or exogenous intoxication from chronic lead exposure, ERG changes give an objective measure of the damage and allow to study the pathophysiological mechanisms that are involved. Inflammations of the choroid and the retina affect the standard ERG when they are diffuse. In central serous chorioretinopathy, functional disturbances can be revealed not only in the photoreceptors but also in the middle and inner retinal layers with the use of focal stimuli. Choroidal melanoma leads to large reductions of the EOG light peak-to-dark trough ratio through its influence on the transepithelial potential of the retinal pigment epithelium (RPE). In cancer-associated retinopathy, both the rod and cone ERGs are reduced. However, selective cone dysfunction has been described. In melanoma-associated retinopathy, the long flash ERG may reveal a specific pathophysiological mechanism, namely the affection of the ON-pathway with preservation of the OFF-pathway. ERG measurements can reveal vitamin A deficiency and are altered in cases with a mutation in the gene for the retinol binding protein in which other organs are not affected. Photochemical damage to the retina from light emission by the operating microscope can be assessed by electrophysiological methods.

Through a shade darkly

A 43-year-old man complained of difficulty seeing in dim light (nyctalopia). A prolonged photostress test and abnormal electroretinogram confirmed retinal rather than optic nerve dysfunction. Vitamin A deficiency secondary to remote ileal-jejunal bypass was diagnosed, and his visual symptoms and signs reversed with oral vitamin A supplementation.

Vitamin A deficiency and xerophthalmia in the United Kingdom

Images

Surgical therapy for obesity can induce a vitamin A deficiency syndrome

New possible causes and unexplored aspects of the electroretinogram were evaluated in a case of vitamin A deficiency secondary to surgical therapy for morbid obesity. The Naka-Rushton equation, applied to the scotopic b-wave, demonstrated the quantal catch reduction caused by the loss of rhodopsin in the outer segment of photoreceptors. Study of the Fourier analysis of the photopic 20-Hz response suggested a primary involvement of the external retinal layers, with an indirect alteration of the inner layer. The electroretinogram oscillatory potentials showed alterations explained by the involvement of their generators related to the primary photoreceptor lesion.

Clinical and subclinical ophthalmic findings with retinol deficiency

BACKGROUND

Patients at risk for retinol deficiency in developed countries include those with hepatic dysfunction and malabsorption states. Symptoms of retinol deficiency may go unrecognized or unreported.

METHODS

The authors describe 15 patients with hepatic dysfunction, two of whom had procedures that would predispose to malabsorption and were ophthalmologically symptomatic of retinol depletion. The other 13 patients were ophthalmologically asymptomatic liver transplant candidates examined prospectively for subclinical evidence of retinol deficiency. Combined laboratory analysis, Schirmer's testing, conjunctival impression cytology, and electroretinography were performed.

RESULTS

Twelve of 15 patients had serum retinol levels below the lower limit of normal. Aqueous tear production was reduced in 7 of 14 patients. Abnormal conjunctival morphology was noted in 6 of 12 patients. Electroretinograms were abnormal in the two patients who were visually symptomatic and in seven of nine patients who were ophthalmologically asymptomatic.

CONCLUSION

Subclinical, physiologically significant retinol deficiency may be a frequent and unrecognized problem among patients with hepatic dysfunction.

Electro-oculogram in vitamin A deficiency associated with cystic fibrosis. Short communication

Electro-oculograms (EOGs) were recorded in a patient with cystic fibrosis and vitamin A deficiency before and during vitamin A supplementation (25,000 IU/day). Before vitamin A supplementation the EOG Arden light/dark ratio was 1.27. After seven months of vitamin A supplementation the Arden ratio increased to 3.0. These results reveal that vitamin A deficiency can cause an abnormal EOG.

A long term follow up of ocular siderosis: quantitative assessment of the electroretinogram

Siderosis oculi is a severe sequel of retained, iron made, intraocular foreign body. Iron atoms or ions, dissolved from the foreign body, may diffuse to the retina and produce irreversible cellular damage. Therefore, early extraction of an iron foreign body is recommended. When the risks of surgical intervention outweigh the danger of siderosis, the patient is periodically examined in order to detect the initial signs of siderosis. The most commonly used test for quantitative and objective assessment of retinal function is the electroretinogram (ERG). We report here a long term ERG follow-up (about 8 years) of a patient suffering from a unilateral iron intraocular foreign body. The development of siderosis was detected by any of the ERG responses; cone-dominated, rod-dominated or mixed cone-rod responses. However, the degree of the assessed damage varied and strongly depended upon the flash intensity used to elicit the ERG response and upon the ERG wave chosen to assess retinal function. The relationship between the ERG b- and a-waves showed a profound deterioration reflecting a reduction in signal transmission from the photoreceptors to the inner nuclear layer. These findings suggested that iron toxicity produced more damage to the inner retina than to the outer retina.

The electroretinogram in preterm infants

With the hope that the electroretinogram (ERG) in preterm infants could help clarify their vitamin A requirements, a technique for recording the full-field ERG in the neonate is described. One hundred seventy-seven ERGs were performed in 59 preterm and 52 term infants. An ERG was recorded as soon as 7 hours after birth and as early as 30 weeks after conception. In preterm infants the a-wave latency was longer and the amplitude less than in term infants of the same age. The amplitude of the ERG in preterm infants increased with the duration of light exposure. Longitudinal data on 15 preterm infants showed a reduction in a-wave latency. None of the ERG findings correlated with postconceptional age, which suggests that the duration of light exposure is a major determinant of the ERG pattern in preterm infants. Despite low circulating levels of retinol, no correlations with any of the ERG values were found.

Attempts to define the minimal serum level of vitamin A required for normal visual function in a patient with severe fat malabsorption

A case with severe malabsorption of fat soluble vitamins is described. The malabsorption developed after an intestinal bypass operation due to morbid obesity. Night blindness occurred as the first symptom of vitamin A deficiency. The cone visual sensory threshold was elevated about one log unit and the rod threshold abot two and a half log units. No changes of the a- and b-waves of the electroretinogram (ERG) was observed. However, during the initial phase of very low serum reninol level (0.21 mumol/l) the summed amplitudes of the oscillatory potentials (OPs) were lower. After parenteral therapy with vitamin A the night blindness disappeared and the dark-adapted rod and cone threshold sensitivity recovered to normal. However, the time-course of rod adaptation first reached normal levels after 5 months. The amplitudes of the OPs of the ERG response returned to normal when the serum retinol level had increased close to normal. Serum retinol levels of 0.7 mumol/l or higher were always associated with normal or close to normal dark-adapted rod sensitivity. However, a normal serum retinol level (> 0.95 mumol/l) and a normal dark-adapted rod threshold sensitivity were not always associated with a normal time-course of the rod adaptation. It is concluded, that the maintenance dosage of vitamin A must be individualized and that patients who have undergone jejuno-ilea bypass surgery must be carefully monitored for vitamin A deficiency by both serum levels and dark adaptation measurements.

Visual function and rhodopsin levels in humans with vitamin A deficiency

Details of rod and cone dysfunction in vitamin A deficiency have been studied in two subjects with primary biliary cirrhosis and one with Crohn's disease, all of whom presented with symptoms of night blindness. Visual function in the mid-peripheral retina was monitored with two-color adaptometry and rhodopsin levels were measured by fundus reflectometry. Initially all three subjects had no measurable rod function and delayed cone adaptation. In one case the dark-adapted cone threshold was also elevated. Oral supplementation with vitamin A restored visual function to normal within 8 days in all subjects. During supplementation, cone function was restored more rapidly than that of rods, though the pattern of recovery was similar for each receptor type. Final thresholds improved first, though the rates at which they were reached were abnormally slow. As recovery continued, adaptation kinetics returned to normal. When rod adaptation was delayed, the regeneration of rhodopsin was also abnormally slow. When rod final threshold was 2 log units higher than normal, rhodopsin regeneration was incomplete, reaching about 70% of the normal level. The initial stages of visual dysfunction during onset of vitamin A deficiency were studied in one subject, and were found to mirror the pattern seen during recovery: rod adaptation was initially slower than normal, but reached completion. Cone adaptation remained normal until rod function was almost absent.