Scotopic Conditions Research Articles

Chloroquine causes similar electroretinogram modifications, neuronal phospholipidosis and marked impairment of synaptic vesicle transport in Albino and Pigmented Rats

Retinal toxicity of chloroquine has been known for several years, but the mechanism(s) of toxicity remain controversial; some author support the idea that the binding of chloroquine to melanin pigments in the retinal pigmented epithelium (RPE) play a major toxic role by concentrating the drug in the eye. In our study, 12 albinos Sprague-Dawley (SD) and 12 pigmented Brown Norway (BN) rats were treated orally for 3 months with chloroquine to compare functional and pathological findings. On Flash electroretinograms (ERG) performed in scotopic conditions, similar and progressive (time-dependent) delayed onset and decreased amplitudes of oscillatory potentials (from Day 71) and b-waves (on Day 92) were identified in both BN and SD rats. In both strains, identical morphological changes consisted of neuronal phospholipidosis associated with UV auto-fluorescence without evidence of retinal degeneration and gliosis; the RPE did not show any morphological lesions or autofluorescence. IHC analyses demonstrated a decrease in GABA expression in the inner nuclear layer. In addition, a marked accumulation of synaptic vesicles coupled with a marked disruption of neurofilaments in the optic nerve fibers was identified.In conclusion, ERG observations were very similar to those described in humans. Comparable ERG modifications, histopathology and immunohistochemistry findings were observed in the retina of both rat strains suggesting that melanin pigment is unlikely involved. chloroquine-induced impairment of synaptic vesicle transport, likely related to disruption of neurofilaments was identified and non-previously reported. This new mechanism of toxicity may also be responsible for the burry vision described in humans chronically treated with chloroquine.

Comparative Visual Function in Predatory Fishes from the Indian River Lagoon

Visual temporal resolution and spectral sensitivity of three coastal teleost species (common snook [Centropomus undecimalis], gray snapper [Lutjanus griseus], and pinfish [Lagodon rhomboides]) were investigated by electroretinogram. Temporal resolution was quantified under photopic and scotopic conditions using response waveform dynamics and maximum critical flicker fusion frequency (CFFmax). Photopic CFFmax was significantly higher than scotopic CFFmax in all species. The snapper had the shortest photoreceptor response latency time (26.7 ms) and the highest CFFmax (47 Hz), suggesting that its eyes are adapted for a brighter photic environment. In contrast, the snook had the longest response latency time (36.8 ms) and lowest CFFmax (40 Hz), indicating that its eyes are adapted for a dimmer environment or nocturnal lifestyle. Species spectral responses ranged from 360 to 620 nm and revealed the presence of rods sensitive to dim and twilight conditions, as well as multiple cone visual pigments providing the basis for color and contrast discrimination. Collectively, our results demonstrate differences in visual function among species inhabiting the Indian River Lagoon system, representative of their unique ecology and life histories.

Negative impact of melatonin ingestion on the photopic electroretinogram of dogs

Melatonin follows a circadian rhythm entrained by the light/dark cycle and plays a role in promoting light sensitivity at night. It has been suggested that melatonin and dopamine reciprocal inhibition may contribute to the switch between day and night vision. The purpose of this study was to investigate the impact of a high dose of melatonin administration on the photopic and scotopic electroretinogram (ERG) of dogs in the daytime, when it is not thought to be present. Photopic and scotopic ERG luminance response functions were obtained from 7 anaesthetized beagle dogs (3 males and 4 females), once without melatonin (control) and once after oral administration of melatonin (90mg/dog). Vmax (maximal b-wave amplitude achieved) and logK (retinal sensitivity) were calculated from the derived luminance response function. Photopic flicker ERG was also recorded. In photopic condition, a-wave amplitude (control: −126.90μV; with melatonin: −49.64μV; p<0.001) and Vmax (control: 252.50μV; with melatonin: 115.40μV; p<0.001) were decreased. A significant reduction of the photopic flicker ERG amplitude was observed after melatonin ingestion. In scotopic condition, an overall difference was reported before and after melatonin ingestion for the a- and b-wave amplitude, but no change was significant for Vmax. Melatonin ingestion at a high dose during the day decreases the photopic amplitude of a- and b-wave, but has no impact on implicit time. This negative impact of melatonin on photopic system may serve to promote night vision.

Expression of Pannexin1 in the outer plexiform layer of the mouse retina and physiological impact of its knockout

Pannexin1 (Panx1) belongs to a class of vertebrate proteins that exhibits sequence homology to innexins, the invertebrate gap junction proteins, and which also shares topological similarities with vertebrate gap junction proteins, the connexins. Unlike gap junctional channels, Panx1 forms single-membrane channels, whose functional role in neuronal circuits is still unsettled. We therefore investigated the subcellular distribution of Panx1 in the mouse retina of wildtype and Panx1-null mice by reverse-transcription polymerase chain reaction (RT-PCR), immunohistochemistry, and electron microscopy. Use of Panx1-deficient mice served as a model to assess the physiological role of Panx1 by electroretinographic recordings and also to ensure the specificity of the anti-Panx1 antibody labeling. Expression of Panx1 was found in type 3a OFF bipolar cells and in dendrites and axonal processes of horizontal cells. Panx1 was also found in horizontal cell dendrites representing the lateral elements of the triad synapse at cone and rod terminals. In vivo electroretinography of Panx1 knockout mice indicated an increased a- and b-wave compared to Panx1 wildtype mice under scotopic conditions. The effect on the b-wave was confirmed by in vitro electroretinograms from the inner retina. These results suggest that Panx1 channels serve as sinks for extracellular current flow making them possible candidates for the mediation of feedback from horizontal cells to photoreceptors.

Electroretinographical and histological study of mouse retina after optic nerve section: a comparison between wild‐type and retinal degeneration 1 mice

Retinal ganglion cell death underlies the pathophysiology of neurodegenerative disorders such as glaucoma or optic nerve trauma. To assess the potential influence of photoreceptor degeneration on retinal ganglion cell survival, and to evaluate functionality, we took advantage of the optic nerve section mouse model. Surviving retinal ganglion cells were double-stained by exposing both superior colliculi to fluorogold, and by applying dextran-tetramethylrhodamine to the injured optic nerve stump. To assess retinal function in wild-type animals, electroretinograms were recorded on the injured eyes and compared with the contralateral. Similar labelling experiments were carried out on retinal degeneration 1 mice. Surviving retinal ganglion cells were counted 21 days after axotomy and compared with wild-type mice. No functional experiments were performed on retinal degeneration 1 animals because they do not develop normal electroretinographical responses. A significant decrease in retinal ganglion cell density was observed 6 days after axotomy in the wild type. Functional studies revealed that, in scotopic conditions, axotomy induced a significant amplitude decrease in the positive scotopic threshold response component of the electroretinogram. Such decrease paralleled cell loss, suggesting it may be an appropriate technique to evaluate functionality. When comparing retinal ganglion cell densities in wild-type and retinal degeneration 1 mice, a significant greater survival was observed on the latter. After optic nerve section, electroretinographical recordings exhibited a progressive decrease in the amplitude of the positive scotopic threshold response wave, reflecting ganglion cell loss. Interestingly, rod degeneration seemed, at least initially, to protect from axotomy-driven damage.

Night vision in barn owls: Visual acuity and contrast sensitivity under dark adaptation

Barn owls are effective nocturnal predators. We tested their visual performance at low light levels and determined visual acuity and contrast sensitivity of three barn owls by their behavior at stimulus luminances ranging from photopic to fully scotopic levels (23.5 to 1.5 × 10⁻⁶). Contrast sensitivity and visual acuity decreased only slightly from photopic to scotopic conditions. Peak grating acuity was at mesopic (4 × 10⁻² cd/m²) conditions. Barn owls retained a quarter of their maximal acuity when luminance decreased by 5.5 log units. We argue that the visual system of barn owls is designed to yield as much visual acuity under low light conditions as possible, thereby sacrificing resolution at photopic conditions.

Loss of CRB2 in the mouse retina mimics human retinitis pigmentosa due to mutations in the CRB1 gene

In humans, the Crumbs homolog-1 (CRB1) gene is mutated in progressive types of autosomal recessive retinitis pigmentosa and Leber congenital amaurosis. However, there is no clear genotype-phenotype correlation for CRB1 mutations, which suggests that other components of the CRB complex may influence the severity of retinal disease. Therefore, to understand the physiological role of the Crumbs complex proteins, we generated and analysed conditional knockout mice lacking CRB2 in the developing retina. Progressive disorganization was detected during late retinal development. Progressive thinning of the photoreceptor layer and sites of cellular mislocalization was detected throughout the CRB2-deficient retina by confocal scanning laser ophthalmoscopy and spectral domain optical coherence tomography. Under scotopic conditions using electroretinography, the attenuation of the a-wave was relatively stronger than that of the b-wave, suggesting progressive degeneration of photoreceptors in adult animals. Histological analysis of newborn mice showed abnormal lamination of immature rod photoreceptors and disruption of adherens junctions between photoreceptors, Müller glia and progenitor cells. The number of late-born progenitor cells, rod photoreceptors and Müller glia cells was increased, concomitant with programmed cell death of rod photoreceptors. The data suggest an essential role for CRB2 in proper lamination of the photoreceptor layer and suppression of proliferation of late-born retinal progenitor cells.

Gβ3Is Required for Normal Light ON Responses and Synaptic Maintenance

Heterotrimeric G-proteins, comprising Gα and Gβγ subunits, couple metabotropic receptors to various downstream effectors and contribute to assembling and trafficking receptor-based signaling complexes. A G-protein β subunit, Gβ(3), plays a critical role in several physiological processes, as a polymorphism in its gene is associated with a risk factor for several disorders. Retinal ON bipolar cells express Gβ(3), and they provide an excellent system to study its role. In the ON bipolar cells, mGluR6 inverts the photoreceptor's signal via a cascade in which glutamate released from photoreceptors closes the TRPM1 channel. This cascade is essential for vision since deficiencies in its proteins lead to complete congenital stationary night blindness. Here we report that Gβ(3) participates in the G-protein heterotrimer that couples mGluR6 to TRPM1. Gβ(3) deletion in mouse greatly reduces the light response under both scotopic and photopic conditions, but it does not eliminate it. In addition, Gβ(3) deletion causes mislocalization and downregulation of most cascade elements and modulators. Furthermore, Gβ(3) may play a role in synaptic maintenance since in its absence, the number of invaginating rod bipolar dendrites is greatly reduced, a deficit that was not observed at 3 weeks, the end of the developmental period.

Safranal, a Saffron Constituent, Attenuates Retinal Degeneration in P23H Rats

Saffron, an extract from Crocus sativus, has been largely used in traditional medicine for its antiapoptotic and anticarcinogenic properties. In this work, we investigate the effects of safranal, a component of saffron stigmas, in attenuating retinal degeneration in the P23H rat model of autosomal dominant retinitis pigmentosa. We demonstrate that administration of safranal to homozygous P23H line-3 rats preserves both photoreceptor morphology and number. Electroretinographic recordings showed higher a- and b-wave amplitudes under both photopic and scotopic conditions in safranal-treated versus non-treated animals. Furthermore, the capillary network in safranal-treated animals was preserved, unlike that found in untreated animals. Our findings indicate that dietary supplementation with safranal slows photoreceptor cell degeneration and ameliorates the loss of retinal function and vascular network disruption in P23H rats. This work also suggests that safranal could be potentially useful to retard retinal degeneration in patients with retinitis pigmentosa.

Photopic and scotopic multifocal pupillographic responses in age-related macular degeneration

We compared photopic and scotopic multifocal pupillographic stimuli in age-related macular degeneration (AMD). Both eyes of 18 normal and 14 AMD subjects were tested with four stimulus variants presented at photopic and 126 times lower luminances. The multifocal stimuli presented 24 test regions/eye to the central 60°. The stimulus variants had two different check sizes, and when presented either flickered (15Hz) for 266ms, or were steady for 133ms. Mean differences from normal of 5 to 7dB were observed in the central visual field for both photopic and scotopic stimuli (all p<0.00002). The best areas under receiver operating characteristic plots for exudative AMD in the photopic and scotopic conditions were 92.9±8.0 and 90.3±5.7% respectively, and in less severely affected eyes 83.8±9.7% and 76.9±8.2%. Damage recorded at photopic levels was possibly more diffusely distributed across the visual field. Sensitivity and specificity was similar at photopic and scotopic levels.

Relationship between visual acuity and other optical parameters in no presbyopic eyes

AbstractPurpose To study the relationship between visual acuity (VA) and fluctuation of accommodation and aberrometric data in a population of no presbyopic eyes.Methods Forty‐two no presbyopic eyes with natural pupil and scotopic lighting conditions were involved in the study. Subjects were studied with an autorefractor to determine the refraction and accommodation fluctuations, a ray tracing aberrometer to measure the refraction as well as aberrometric data, and a system to generate charts and determine the subjective refraction and the AV. The equipments were calibrated with an artificial eye before the tests were done. The subjects were divided in several subgroups of 1) subjective refraction (≥|‐0.50|D or &lt;|‐0.50|D); 2) fluctuation of accommodation (≤0.1D or &gt;0.1D) and 3) RMS of different high order (HO) aberrations: 3a) RMS of HO total (≤0.25µm or &gt;0.25µm), 3b) RMS of spherical aberration (≤0.15µm or &gt;0.15µm), 3c) RMS of coma (≤0.15µm or &gt;0.15µm) and 2d) RMS of trefoil (≤0.15µm or &gt;0.15µm)Results The mean value for VA was 1.28 and 0.16 D for fluctuations of accommodation. No significant differences among fluctuations of accommodation and VA were found in any group. We found normal values about RMS of HO (0.34 μm), RMS of coma (0.19 μm), RMS of trefoil (0.17 μm) and spherical aberration (0.11 μm). No differences between RMS and VA were found in any group. A moderate correlation (R2=0.19) between the VA and the spherical aberration was observed.Conclusion The values of fluctuation of accommodation and aberrometric data were within normal ranges reported in the literature. Differences between VA and other optical parameters were not found.

Light-Induced Plasticity of Synaptic AMPA Receptor Composition in Retinal Ganglion Cells

Light-evoked responses of all three major classes of retinal ganglion cells (RGCs) are mediated by NMDA receptors (NMDARs) and AMPA receptors (AMPARs). Although synaptic activity at RGC synapses is highly dynamic, synaptic plasticity has not been observed in adult RGCs. Here, using patch-clamp recordings in dark-adapted mouse retina, we report a retina-specific form of AMPAR plasticity. Both chemical and light activation of NMDARs caused the selective endocytosis of GluA2-containing, Ca(2+)-impermeable AMPARs on RGCs and replacement with GluA2-lacking, Ca(2+)-permeable AMPARs. The plasticity was expressed in ON but not OFF RGCs and was restricted solely to the ON responses in ON-OFF RGCs. Finally, the plasticity resulted in a shift in the light responsiveness of ON RGCs. Thus, physiologically relevant light stimuli can induce a change in synaptic receptor composition of ON RGCs, providing a mechanism by which the sensitivity of RGC responses may be modified under scotopic conditions.

The absence of Complexin 3 and Complexin 4 differentially impacts the ON and OFF pathways in mouse retina

Complexins (Cplxs) regulate the speed and Ca(2+)-sensitivity of synaptic vesicle fusion. It has been shown that all four known Cplxs are present at mouse retinal synapses--at conventional amacrine cell synapses (Cplx 1 to Cplx 3) and at photoreceptor and bipolar cell ribbon synapses (Cplx 3 and Cplx 4) [K. Reim et al. (2005) J. Cell Biol., 169, 669-680]. Electroretinographic recordings in Cplx 3/Cplx 4 double-knockout (DKO) mice showed perturbed transmission in the outer plexiform layer, and possible changes in the inner plexiform layer [K. Reim et al. (2009) J. Cell Sci., 122, 1352-1361]. In the present study, we examined the effects of the absence of Cplx 3 and Cplx 4 on ganglion cell responses. We report that the lack of Cplx 3 and Cplx 4 differentially impacts the ON and OFF pathways. Under photopic conditions, the responses in the cone OFF pathway are largely unaffected, whereas the responses in the cone ON pathway are diminished in Cplx 3/Cplx 4 DKO mice. Under scotopic conditions, both ON and OFF response rates are reduced and high-sensitivity OFF responses are missing in Cplx 3/Cplx 4 DKO mice. The electrophysiological findings are corroborated by new immunocytochemical findings. We now show that rod spherules contain only Cplx 4. However, both Cplx 3 and Cplx 4 co-localize in cone pedicles. In the inner plexiform layer, Cplx 3 is present in rod bipolar cell terminals and in amacrine cell processes. Most importantly, Cplx 3 is localized in the lobular appendages of AII amacrine cells, the sites of signal transmission from the primary rod pathway into the OFF pathway in the inner plexiform layer.

Mechanistic modeling of vertebrate spatial contrast sensitivity and acuity at low luminance

The validity of the Barten theoretical model for describing the vertebrate spatial contrast sensitivity function (CSF) and acuity at scotopic light levels has been examined. Although this model (which has its basis in signal modulation transfer theory) can successfully describe vertebrate CSF, and its relation to underlying visual neurophysiology at photopic light levels, significant discrepancies between theory and experimental data have been found at scotopic levels. It is shown that in order to describe scotopic CSF, the theory must be modified to account for important mechanistic changes, which occur as cone vision switches to rod vision. These changes are divided into photon management factors [changes in optical performance (for a dilated pupil), quantum efficiency, receptor sampling] and neural factors (changes in spatial integration area, neural noise, and lateral inhibition in the retina). Predictions of both scotopic CSF and acuity obtained from the modified theory were found to be in good agreement with experimental values obtained from the human, macaque, cat, and owl monkey. The last two species have rod densities particularly suited for scotopic conditions.

Restoration of vision after transplantation of photoreceptors

Cell transplantation is a potential strategy for treating blindness caused by the loss of photoreceptors. Although transplanted rod-precursor cells are able to migrate into the adult retina and differentiate to acquire the specialized morphological features of mature photoreceptor cells, the fundamental question remains whether transplantation of photoreceptor cells can actually improve vision. Here we provide evidence of functional rod-mediated vision after photoreceptor transplantation in adult Gnat1−/− mice, which lack rod function and are a model of congenital stationary night blindness. We show that transplanted rod precursors form classic triad synaptic connections with second-order bipolar and horizontal cells in the recipient retina. The newly integrated photoreceptor cells are light-responsive with dim-flash kinetics similar to adult wild-type photoreceptors. By using intrinsic imaging under scotopic conditions we demonstrate that visual signals generated by transplanted rods are projected to higher visual areas, including V1. Moreover, these cells are capable of driving optokinetic head tracking and visually guided behaviour in the Gnat1−/− mouse under scotopic conditions. Together, these results demonstrate the feasibility of photoreceptor transplantation as a therapeutic strategy for restoring vision after retinal degeneration.

Comparison of wavefront aberrations under cycloplegic, scotopic and photopic conditions using WaveScan

To evaluate the differences of wavefront aberrations under cycloplegic, scotopic and photopic conditions. A total of 174 eyes of 105 patients were measured using the wavefront sensor (WaveScan® 3.62) under different pupil conditions: cycloplegic 8.58 ± 0.54 mm (6.4 mm - 9.5 mm), scotopic 7.53 ± 0.69 mm (5.7 mm - 9.1 mm) and photopic 6.08 ± 1.14 mm (4.1 mm - 8.8 mm). The pupil diameter, standard Zernike coefficients, root mean square of higher-order aberrations and dominant aberrations were compared between cycloplegic and scotopic conditions, and between scotopic and photopic conditions. The pupil diameter was 7.53 ± 0.69 mm under the scotopic condition, which reached the requirement of about 6.5 mm optical zone design in the wavefront-guided surgery and prevented measurement error due to the pupil centroid shift caused by mydriatics. Pharmacological pupil dilation induced increase of standard Zernike coefficients Z(3)(-3), Z(4)(0) and Z(5)(-5). The higher-order aberrations, third-order aberration, fourth-order aberration, fifth-order aberration, sixth-order aberration, and spherical aberration increased statistically significantly, compared to the scotopic condition (P<0.010). When the scotopic condition shifted to the photopic condition, the standard Zernike coefficients Z(4)(0), Z(4)(2), Z(6)(-4), Z(6)(-2), Z(6)(2) decreased and all the higher-order aberrations decreased statistically significantly (P<0.010), demonstrating that accommodative miosis can significantly improve vision under the photopic condition. Under the three conditions, the vertical coma aberration appears the most frequently within the dominant aberrations without significant effect by pupil size variance, and the proportion of spherical aberrations decreased with the decrease of the pupil size. The wavefront aberrations are significantly different under cycloplegic, scotopic and photopic conditions. Using the wavefront sensor (VISX WaveScan) to measure scotopic wavefront aberrations is feasible for the wavefront-guided refractive surgery.

Interocular differences in visual quality due to ocular aberrations and scattering in a patient with post-traumatic anisocoria: A case report

A 41-year-old patient with visual disturbances after an ocular trauma in right eye three years before was carefully analyzed and discussed. No corneal or intraocular sequelae were present. Only a significant anisocoria could be observed. Right eye (RE) achieved a best spectacle-corrected visual acuity (BSCVA) of 0.05 LogMAR with a refraction of +0.50 sphere and −1.25 cylinder. Left eye (LE) achieved a BSCVA of 0.0 LogMAR with a refraction of +0.75 sphere and −1.00 cylinder. In photopic conditions pupil diameter was 4.96mm for RE and 3.02mm for LE whereas in scotopic conditions, these values were 7.45mm and 6.71mm, respectively. More significant levels of higher-order corneal and ocular aberrations were found in RE for the same pupil size. In addition, the scattering index (OSI) was 3.8 in RE and 1.0 in LE (4-mm pupil). In conclusion, anisocoria can lead to relevant visual disturbances if significant interocular differences in ocular aberrations and scattering are present.

Therapeutic Benefit of Radial Optic Neurotomy in a Rat Model of Glaucoma

Radial optic neurotomy (RON) has been proposed as a surgical treatment to alleviate the neurovascular compression and to improve the venous outflow in patients with central retinal vein occlusion. Glaucoma is characterized by specific visual field defects due to the loss of retinal ganglion cells and damage to the optic nerve head (ONH). One of the clinical hallmarks of glaucomatous neuropathy is the excavation of the ONH. The aim of this work was to analyze the effect of RON in an experimental model of glaucoma in rats induced by intracameral injections of chondroitin sulfate (CS). For this purpose, Wistar rats were bilaterally injected with vehicle or CS in the eye anterior chamber, once a week, for 10 weeks. At 3 or 6 weeks of a treatment with vehicle or CS, RON was performed by a single incision in the edge of the neuro-retinal ring at the nasal hemisphere of the optic disk in one eye, while the contralateral eye was submitted to a sham procedure. Electroretinograms (ERGs) were registered under scotopic conditions and visual evoked potentials (VEPs) were registered with skull-implanted electrodes. Retinal and optic nerve morphology was examined by optical microscopy. RON did not affect the ocular hypertension induced by CS. In eyes injected with CS, a significant decrease of retinal (ERG a- and b-wave amplitude) and visual pathway (VEP N2-P2 component amplitude) function was observed, whereas RON reduced these functional alterations in hypertensive eyes. Moreover, a significant loss of cells in the ganglion cell layer, and Thy-1-, NeuN- and Brn3a- positive cells was observed in eyes injected with CS, whereas RON significantly preserved these parameters. In addition, RON preserved the optic nerve structure in eyes with chronic ocular hypertension. These results indicate that RON reduces functional and histological alterations induced by experimental chronic ocular hypertension.

Electroretinographic (ERG) responses in pediatric patients using vigabatrin

The antiepileptic drug vigabatrin is known to cause retinal and visual dysfunction, particularly visual field defects, in some patients. Electroretinography (ERG) is used in an attempt to identify adverse effects of vigabatrin (VGB) in patients who are not candidates for conventional perimetry. We report data from 114 pediatric patients taking VGB referred for clinical evaluation; median age at test was 22.9 (2.4 to 266.1) months, and median duration of VGB use was 9.7 (0.3 to 140.7) months. Twenty-seven of them were tested longitudinally (3 to 12 ERG tests). ERG responses to full-field stimuli were recorded in scotopic and photopic conditions, and results were compared to responses from healthy control subjects. We found that abnormalities of photoreceptor and post-receptor ERG responses are frequent in these young patients. The most frequently abnormal scotopic parameter was post-receptor sensitivity, log σ, derived from the b-wave stimulus-response function; the most frequently abnormal photopic parameter was the implicit time of the OFF response (d-wave) to a long (150 ms) flash. Abnormal 30-Hz flicker response amplitude, previously reported to be a predictor of visual field loss, occurred infrequently. For the group as a whole, none of the ERG parameters changed significantly with increasing duration of VGB use. Four of the 27 patients tested longitudinally showed systematic worsening of log σ with duration of VGB use. In a subset of patients who underwent perimetry (N = 39), there was no significant association of any ERG parameter with visual field defects. We cannot determine whether the ERG abnormalities we found were due solely to the effects of VGB. We caution against over-reliance on the ERG to monitor pediatric patients for VGB toxicity and recommend further development of a reliable test of peripheral vision to supplant ERG testing.

Emetropların ve Miyopların Pupil Çaplarının Fotopik, Mezopik ve Skotopik Koşullarda Schwind Sirius Çok Amaçlı Tanı Aracı ile Entegre İnfrared Pupillometre Kullanılarak Değerlendirilmesi

Objective: To assess the pupil diameters of emmetropes and myopes in photopic, mesopic and scotopic conditions. Material and Methods: Pupil diameters of 49 emmetropic subjects [spherical equivalent (SE) values ±0.25 diopter (D) with a mean age of 31.0±10.5 years (range 17 to 58 years)], and 61 age-matched (mean age 31.3±8.9 years, range 17 to 52 years) myopic subjects (SE values ?-1D) were measured with the infrared pupillometer integrated within Schwind Sirius Multifunctional diagnostic device (Eye-tech-solutions, Kleinostheim, Germany) in photopic (40 lux) condition simulating the day-time, in mesopic (4 lux) condition and in scotopic (0.04 lux) condition simulating the level of light encountered at night. All statistical analyses were performed according to two-sided hypothesis tests and a p-value of less than 0.05 was considered statistically significant. Results: The mean photopic pupil diameter was 3.62±0.73 mm (range 2.49 to 5.83) in the emmetropic group and 3.86±0.85 mm (range 2.06 to 6.67) in the myopic group. The mean mesopic pupil diameters were 4.68±0.78 mm (range 3.19 to 6.45) and 5.16±0.91 mm (range 3.23 to 7.46) and the mean scotopic pupil diameters were 5.63±0.70 mm (range 4.28 to 7.14) and 6.08±0.86 mm (range 4.30 to 7.95) in emmetropes and myopes, respectively. The mean pupil diameters of myopes were larger than emmetropes in all three light conditions (p<0.001). There was no interaction between patient group and light condition (p>0.05). Conclusion: The mean pupil diameters of myopic subjects were larger than the pupil diameter of emmetropes. Pupil diameter should be measured objectively under standardized illumination levels in order to minimize the risk of post-operative glare and halo formation in refractive surgery patients.