Showing papers in "Documenta Ophthalmologica in 1990"

Refractive surgery for high myopia. The Worst-Fechner biconcave iris claw lens.

Abstract: Surgical correction of high myopia is indicated in a limited number of cases. Techniques include (epi)keratophakia, keratomileusis and implantation of a negative-power IOL. The iris claw lens, fixed to the midperiphery of the iris, has proved its safety in aphakic eyes. The model has been adapted by giving it a vault in order to make it suitable for implantation in high myopic phakic eyes. The implantation technique and short-term results of patients operated by Worst are presented.

On the history of deformation phosphenes and the idea of internal light generated in the eye for the purpose of vision.

Abstract: Deformation phosphenes are light sensations evoked by deformation of the eyeball in total darkness. They were first reported in Western literature by Alcmaeon of Croton in the fifth century B.C. The phenomenon of deformation phosphenes was instrumental in prompting some pre-Socratic philosophers and Plato to conceive the idea that efferent light is emitted from the eye for the purpose of vision and a ‘cone of vision’ is formed by interaction with the external light. In the theories of vision this cone of vision played an important role as a signal-transmitting structure and was also used by the Greek opticians as a geometrical construction to explain optical properties of vision.

Convergent strabismus fixus in high myopic patients.

Abstract: Patients with high myopia may develop a myopathy which frequently results in a sort of convergent strabismus fixus. Echographic and CT scan findings give evidence that a myopathic paralysis of the lateral rectus is supported by a slow pressure on this muscle squeezed between the lateral orbital wall and the enlarged eyeball.

Results of U.S. randomized clinical trial of cryotherapy for ROP (CRYO-ROP).

Abstract: Twenty-three centers collaborated in this prospectively designed study involving infants born weighing less than 1251 grams. Patients examinations began 4 to 6 weeks from birth. For entry into the study, two investigators had to agree that an eye had developed stage 3 ROP involving a threshold number of at least 5 contiguous or 8 total clock hour sectors of zone 1 or 2, and 'plus' disease to a degree specified by a standard photograph. Cryotherapy was lightly applied to the avascular zone between the ridge of ROP and the ora serrata, in an average of about 50 separate spots. Outcome was determined 3 and 12 months following randomization, by means of masked readings of fundus photographs. Preliminary results were published in the Archives of Ophthalmology, Vol. 106, pp. 471-479, 1988. In these results from 172 of the 291 study patients, 43.0% of the control eyes had an adverse outcome (defined as retinal detachment, macular fold, or retrolental mass), as compared to 21.8% adverse outcome for eyes that received cryotherapy.

Properties of visual evoked potentials to onset of movement on a television screen.

Abstract: In 80 subjects the dependence of movement-onset visual evoked potentials on some measures of stimulation was examined, and these responses were compared with pattern-reversal visual evoked potentials to verify the effectiveness of pattern movement application for visual evoked potential acquisition. Horizontally moving vertical gratings were generated on a television screen. The typical movement-onset reactions were characterized by one marked negative peak only, with a peak time between 140 and 200 ms. In all subjects the sufficient stimulus duration for acquisition of movement-onset-related visual evoked potentials was 100 ms; in some cases it was only 20 ms. Higher velocity (5.6 degree/s) produced higher amplitudes of movement-onset visual evoked potentials than did the lower velocity (2.8 degrees/s). In 80% of subjects, the more distinct reactions were found in the leads from lateral occipital areas (in 60% from the right hemisphere), with no correlation to handedness of subjects. Unlike pattern-reversal visual evoked potentials, the movement-onset responses tended to be larger to extramacular stimulation (annular target of 5 degrees-9 degrees) than to macular stimulation (circular target of 5 degrees diameter).

Oxygen-induced retinopathy in the rat: possible contribution of peroxidation reactions.

Abstract: Albino rats were maintained in 60% atmospheric oxygen from birth through 14 days of age. Age-matched controls were simultaneously raised in room air. Some rats were perfused with India ink before sacrifice and retinal dissection in order to study the effect of oxygen-rearing on the retinal vasculature. By this method it was found that oxygen-reared animals sustained a 36% loss of retinal blood vessels. Other animals' retinas were removed immediately after sacrifice and examined for evidence of lipid peroxidation by one of three means: 1) a determination of the presence of products of lipid peroxidation, 2) a measure of the loss of polyunsaturated fatty acids, and 3) a determination of retinal vitamin E level. Each of these determinations indicated that peroxidation reactions had occurred in the retinas of oxygenreared rats. Retinal vitamin E was supplemented in the young rats through the diet of the mothers. This treatment resulted in a two-fold increase of retinal vitamin E over levels in pups of mothers fed rat chow. Oxygen-reared vitamin E-supplemented rats sustained significantly less obliteration of blood vessels than non-supplemented oxygen-reared animals.

Focal ischaemic normal pressure glaucoma versus high pressure glaucoma.

Abstract: In a total group of 130 patients with Normal Pressure Glaucoma (NPG) twenty-six were classified as Focal Ischaemic NPG (FINPG). This subgroup has a typical defect at the disc with a comparable visual field defect in the corresponding half of the visual field. Visual field defects are more often seen in the upper than the lower half of the visual field. The defects in the upper half are on the average larger (stage 1.6) than those in the lower half (stage 0.9). Abnormalities of the chamber angle were observed in 12% of these patients, the same percentage as in the normal population. Hypertension and/or cardiovascular disorders were found significantly more frequently in FINPG patients (65.4%) than in a control group of High Pressure Glaucoma (HPG) patients (22.2%). Of the local vascular risk factors, papillary haemorrhages (46%) and choroidal sclerosis (30%) were seen significantly more frequently in FINPG than in HPG (11% and 0% respectively). The total amount of peripapillary atrophy (PPA) in FINPG and HPG is the same, but the distribution is clearly different: in FINPG there is more PPA on the side of the papillary defect. Wide veins were observed in a high percentage of cases in both groups. FINPGs were found to be more frequently progressive (38.5%) than had been thought at first. Recognition of subgroups in NPG, and of risk factors, has already made it possible to make a better prognosis in some types of NPG.

Oxygen-induced retinopathy in the rat model.

Abstract: Identification of a suitable animal model is essential for the continued study of retinopathy of prematurity (ROP). Since 1984 we have used the newborn rat for the study of oxygen-induced retinopathy (OIR). The rat retina is highly immature at birth. Like those of humans, the retinal vessels arise from mesenchymal precursors, but contrary to that which occurs in humans, canalization of the rats inner retinal vessels is not related to the presence of cystoid spaces. In addition, only immature Stage I photoreceptors are present around the optic disk at birth. This extreme immaturity makes the rat retina highly susceptible to direct damage from oxygen. Oxygen-induced retinopathy can be produced by exposing the newborn rat to 80% oxygen for the first 7–10 days of life. We have demonstrated that OIR does not develop when oxygen is administered under conditions of moderate hyperbarism (+ 1.8 atm). It is possible that hyperbarism exerts a protective effect on the immature retinal vessels by inducing a vasoconstrictive response which reduces the amount of oxygen transported from the choroid to the inner retina during hypoxia. I recently hypothesized that this vasoconstriction might also affect the ciliary body, thus reducing the quantity of aqueous produced, and we are currently studying the relationship between development of the immature retinal vessels in the rat and production and drainage of the aqueous. The question we are attempting to answer is whether a condition of relatively increased intraocular pressure is capable of promoting the development of OIR.

Blue-yellow perimetry in the detection of early glaucomatous damage.

Abstract: A perimetric method using blue stimuli on a yellow background was compared with perimetry using white stimulion on a white background as a method of detecting glaucomatous damage. Meridian perimetry was used with an adapted Tubinger perimeter. The difference between the blue-on-yellow meridian and the white-on-white meridian was subdivided into two parts: the general blue sensitivity loss (GBSL), probably due to optical factors, and the corrected blue sensitivity loss (CBSL), probably due to glaucoma. Nine normals, fourteen primary open angle glaucoma (POAG) patients and nine ocular hypertensives (OHT) were tested. All POAG patients and some of the OHT group showed higher CBSL values than the controls. The blue-yellow meridian showed broader and deeper defects than the white-white meridian in all of the POAG group; some of the OHT group had defects in the blue-yellow meridian that were not present in the white-white meridian.In conclusion, blue on yellow perimetry shows promise as a method for more sensitive detection of early glaucomatous damage.

Macular oscillatory potentials in humans. Macular OPs.

Abstract: Studies of the focal macular electroretinogram (ERG) have been made with special reference to oscillatory potentials (OPs) by using a fundus monitoring system in humans. Human macular OPs consist of 3 to 4 wavelets (mean peak interval, approximately 6.5 msec). The distribution of OPs in relation to those in a- and b-waves was studied. The amplitudes of a-waves, b-waves, and OPs of the upper macula were significantly larger than those of the lower macula. The distribution of OPs is relatively sparse in the fovea, becoming more dense than the a- and b-waves from the fovea toward the parafovea, and differing even more toward the perifovea. There was no statistical difference of amplitude in a- and b-waves between nasal and temporal macula. The amplitude of OPs in the temporal macula, however, was significantly larger than in the nasal macula. In some macular diseases, such as diabetic maculopathy, cystoid macular edema, or the convalescent stage of central serous chorioretinopathy, macular OPs were selectively reduced, leaving the a- and b-waves intact. Macular OPs can provide a new aspect of macular function and can be a sensitive indicator to assess that function in macular diseases.

The effects of levodopa and haloperidol on flash and pattern ERGs and VEPs in normal humans.

Abstract: We investigated the effects of single doses of the dopamine agonist levodopa and the dopamine antagonist haloperidol on pattern and flash electroretinograms (ERGs) and visual evoked potentials (VEPs) in normal subjects. A placebo and two treatment regimens were administered in a randomized double-masked design. No significant intertreatment differences in the pattern ERGs and VEPs were noted. Although not statistically significant, a clearly discernible tendency was found for increased flash ERG b-wave amplitudes after levodopa administration compared with placebo. In comparison with placebo and levodopa, haloperidol was associated with significantly prolonged flash ERG b-wave implicit times, including each oscillatory potential, which also showed increased duration, particularly in the O1-O3 interpeak implicit time. The failure of pattern ERGs and VEPs to show changes after haloperidol may have been related to the timing of the recordings, which took place during the presumed phase of rising blood levels and before the flash ERG and VEP recordings. Our findings further demonstrated the reliability of the flash ERG in revealing changes in dopaminergic status in the visual system and suggest that steady-state (flicker) ERGs, cone ERGs, and oscillatory potentials have particular use in this regard.

The mouse model of oxygen-induced retinopathy: a suitable animal model for angiogenesis research.

Abstract: Newborn mice exposed to high (>98%) ambient oxygen during the newborn period and subsequently removed to room air will develop a proliferative retinopathy which mimics the neovascular component of acute retinopathy of prematurity In this paper, we report preliminary ultrastructural findings on the vitreous new vessels in the mouse model of oxygen-induced retinopathy, and argue that the model is appropriate for research on non surgical treatments for ROP in particular and angiogenesis in general

The human motion onset VEP as a function of stimulation area for foveal and peripheral vision.

Abstract: We studied amplitude of the wave N200 of the motion-onset VEP by varying the side length of a square stimulation field between 0.5 and 7 degrees. A significant increase in amplitude was obtained between 0.5 and 1 degree of side length in central stimulation and between 0.5 and 5 degrees in 10-degree peripheral stimulation. Variations of spatial frequency between 0.34 and 6.8 c/deg did not modify the amplitude size, ie, no tuning effect could be found. The results of simultaneous and separate stimulation of foveal and parafoveal regions support the observation that the stimulation field size is a minor influence. Features of motion-sensitive cortical neurons, such as those found in monkeys, could account for this behavior.

Fundus changes in chronic membranoproliferative glomerulonephritis type II.

Abstract: Chronic membranoproliferative glomerulonephritis type II (dense deposit disease) is a renal disease characterized by dense deposits in the glomerular and tubular basement membranes. We report a retinopathy with diffuse retinal pigment alterations in 11 out of 12 patients with this disease. Four of the eleven patients also presented disciform macular detachment and choroidal neovascularisation. The lesions were observed at the earliest 1 year after the diagnosis of the renal disease. In a control group of 17 patients with chronic membranoproliferative glomerulonephritis type I none of the patients presented similar fundus lesions.

Electrooculographic and electroretinographic study in the chicken after dopamine and haloperidol.

Abstract: The implication of dopamine in the modulation of the standing potential of the eye was tested in the chicken through an indirect electrooculographic method and direct current electroretinogram (ERG) recording after haloperidol, a mixed D1-D2 antagonist. The standing potential of the eye was reduced within 15 min after intravitreal injection of the antagonist (150 μg). This effect is rapidly reversed by an application of dopamine. The fast oscillation was preserved but the light peak was either strongly reduced or abolished. The dark trough showed an apparently normal time course. The intensity-voltage function was studied for the various ERG components. After haloperidol the b-wave and the c-wave were strongly reduced, whereas the a-wave was little affected. Together with previous data obtained with intraocular injections of dopamine, our data suggest the involvement of dopamine in the modulation of the standing potential. They also support the hypothesis that the light peak, which is generated by a photoreceptor-pigment epithelium interaction, is influenced by dopamine or by a related substance. The modulatory effect could also be due to a balance between several neurotransmitter systems.

The gonioseton, a surgical-treatment for chronic glaucoma

Abstract: A new and simple technique for glaucoma filtering surgery is presented. It is based on the introduction of a stainless steel microspiral or gonioseton into a goniopuncture by way of an ab interno procedure, minimising surgical trauma to the filtration area. Preliminary results are presented.

Critical mass retinopathy of prematurity: what is it and what can you do about it?

Abstract: This paper presents a summary of my experience with treatment of 41 patients with retinopathy of prematurity. From November, 1976, to June, 1988, 76 eyes with Stage 3b, 3c, and Stage 4 ROP had treatment to the ridge-EFP complex, the avascular retina, or both locations. Cryotherapy was used in all eyes, with two having Argon laser photocoagulation as well. These studies have shown that: 7.9% of all treated eyes had Grade III to V RLF; the optimal timing of intervention is recommended during progression of Stage 3b+ ROP; the optimal location of treatment appears to be the avascular retina with the ridge-EFP perhaps as effective but the treatment of both areas simultaneously is to be avoided due to an increased occurrence of grade II RLF and macular pigment epitheliopathy in those eyes so treated. A comparison of results of four major studies indicate that the U.S. Cryo-ROP Study has three times the rate of Grade III to V RLF, probably because of intervention after the accumulation of excessive quantities of Stage 3b and/or 3c ROP.

Steady-state pattern electroretinogram following long term unilateral administration of timolol to ocular hypertensive subjects.

Abstract: To determine whether long-term reduction of intraocular pressure leads to a corresponding preservation of the pattern electroretinogram (PERG), PERGs were studied in 21 patients with ocular hypertension who had received unilateral timolol therapy for a minimum of 6 years. The mean difference in intraocular pressure (IOP) between the placebo-treated and the timolol-treated eyes (over 6 years) was 2.4 mm Hg. Steady-state PERGs (16.0 rps) were obtained simultaneously in both eyes of each patient, with four check sizes (0.25, 0.5, 1.0 and 2.0 degrees). Significant (p less than 0.05) steady-state PERG deficits (i.e., amplitude more than two standard deviations below the mean value of age-matched controls) were observed in 16 eyes of 12 patients (10 placebo-treated and 6 timolol-treated eyes). The mean PERG amplitude did not differ significantly between the placebo-treated and timolol-treated eyes. However, a significant correlation (r = -0.423) in the IOP differences between the placebo-treated and timolol-treated eyes and the corresponding PERG amplitude differences was noted in three of the four test conditions (i.e. 0.25, 0.5, and 1.0 degrees). These results suggest that reducing IOP may preserve ganglion cell function in some patients with ocular hypertension.

Visual field behavior after intra-ocular surgery in glaucoma patients with advanced defects.

Abstract: Fifty advanced glaucoma patients with central visual field islands were evaluated before and after intra-ocular surgery with respect to visual acuity and visual field behavior. Thirteen patients underwent a cataract extraction, and 37 a filtering procedure. Visual acuity generally improved to a certain extent after lens extraction, and deteriorated after filtering surgery. For both groups the visual field island became somewhat larger with respect to the surface area, but the foveal value was usually lower after the operation. There was no clear relationship between visual acuity and foveal values or the surface area of the central island. One patient suffered unexplained loss of central vision.

The effect of 2-amino-4-phosphonobutyric acid on the oscillatory potentials of the electroretinogram.

Abstract: Previous reports have shown that an intravitreal injection of 2-amino-4-phosphonobutyric acid, a glutamate analogue that selectively blocks the photoreceptors' input to the on-bipolar cells, produces a rapid decrease in the amplitude of the electroretinographic b-wave. To our knowledge, the effect of this glutamate analogue has not been examined on the oscillatory potentials. We therefore conducted such a study. A needle electrode was inserted into the anterior chamber of the eyes of seven anesthetized and paralyzed rabbits to record simultaneously the electroretinogram and the oscillatory potentials. These responses were evoked by flashes of white light delivered in mesopic conditions. As expected, an injection of 2-amino-4-phosphonobutyric acid, produced a rapid decrease in the amplitude of the b-wave, while the a-wave was relatively spared. The amplitude of the oscillatory potentials also decreased rapidly. At maximal effect, the electroretinogram essentially consisted of a normal a-wave followed by small oscillations and no evidence of a b-wave. The 100–1000 Hz recording confirmed that the oscillations seen on the postinjection electroretinograms were remnants of the original oscillatory potentials.

19th century mechanical models of eye movements, Donders' law, Listing's law and Helmholtz' direction circles.

Abstract: Donders, Ruete, von Graefe, von Helmholtz, Listing, Volkmann and many others have provided the broad outline of an answer to the question how the eye rotates during eye movements. Many mechanical models of eye movements, ophthalmotropes, have been constructed and studied in the nineteenth century. These models have primarily served to explain Donders’ and Listing’s Laws on the nature of eye movements. As both Donders’ Law and Listing’s Law are easier to understand when seen against the background of the coordinate systems used to describe eye movements, all of the coordinate systems currently in use in the diagnosis and treatment of strabismus are described. In addition, the reader is introduced to a coordinate system based on von Helmholtz’ direction circles, circles describing the direction of the horizontal and vertical retinal meridians in all positions of gaze.

Periorbital necrotising fasciitis due to Cryptococcus neoformans in a healthy young man.

Abstract: A case report is presented of a healthy 25-year-old man who developed a periorbital necrotising fasciitis after a trivial trauma with a wooden splinter. Necrotising fasciitis of the eyelids occurs rarely. Cryptococcus neoformans is not described as a causative factor of necrotizing fasciitis. Cryptococcus neoformans usually infects patients with immunodeficiencies, diabetes mellitus or steroid therapy. This patient was healthy and developed a periorbital necrotising fasciitis due to Cryptococcus neoformans.

Variability of the steady-state visually evoked potential: interindividual variance and intraindividual reproducibility of spatial frequency tuning.

Abstract: At low contrast levels there is good agreement between the psychophysical contrast sensitivity function and the tuning curve of the visually evoked potential (i.e., VEP amplitude vs spatial frequency). At high contrast, however, some researchers have found bimodal VEP tuning curves whereas others have not. We studied the VEP in 22 subjects in a short-term cross-sectional study and in 13 subjects in a longitudinal study over 8 sessions covering 28 days. Grating stimuli with 60% contrast were square-wave modulated in time (7.8 reversals/s) and space (0.06–16 cycles/degree). We found large interindividual variance in the shape of the tuning curves; about half of the subjects showed a unimodal shape, while the other half showed a bimodal one (with a ‘notch’ between 1 and 2 cycles/degree). These features turned out to be stable in the longitudinal study, where variability could mainly be ascribed to a multiplicative influence common to all spatial frequencies. The marked interindividual differences in the shape of the tuning curve, which seem to be intraindividually stable, may explain previous discrepancies. It is not yet clear why the notch exists in about half of our subjects.

Laboratory tests in uveitis. New developments in the analysis of local antibody production.

Abstract: Analysis of local intraocular antibody production is a valuable tool with which to confirm a suspected clinical diagnosis in uveitis. We have analysed paired serum and aqueous samples for the presence of specific antibodies against toxoplasma, cytomegalovirus, herpes simplex virus and varicella zoster virus. Of the patients retrospectively diagnosed as having toxoplasma chorioretinitis 75% had a positive antibody coefficient indicating specific antibody production in the eye. Local antibody production in the eye directed against CMV confirmed the suspected diagnosis of CMV retinitis in 50% of the AIDS patients investigated. So far we have not been able to demonstrate local antibody production against herpes simplex virus (26 samples tested). Two of three patients with acute retinal necrosis had a positive antibody coefficient against varicella zoster virus. Both of these patients had an even higher titer in the aqueous than in serum. Since the choice of therapy, in infectious uveitis, depends on the causative organisms, it is very important to confirm a suspected clinical diagnosis by means of aqueous humor analysis.

Light and the developing retina

Abstract: Retinopathy of prematurity (ROP) has increased in the United States in the past decade. Its resurgence has been attributed to advances in medical care which have increased the survival of infants less than 1000g. Retinal immaturity and exposure to supplementary oxygen are generally accepted as the principal factors associated with ROP, however precocious exposure of the immature retina to light may also contribute. The preterm infant is routinely exposed for the duration of hospital stay to bright continuous light at levels which produce retinal damage in animals. A recent study has provided evidence implicating light in ROP. Preterm infants for whom the light levels were reduced had a lower incidence of ROP, compared to a similar group of preterms exposed to standard levels of nursery light. Given the problems of a non-randomized design, the results must be considered preliminary; however the findings are substantiated by parallel results in both hospitals studied and by an effect of exposure to light within the treatment group. Speculations regarding the mechanisms of light as a contributor to ROP include: alterations of retinal metabolism, cellular damage by phototoxicity, and the generation of free radicals. Mechanisms of phototoxicity are compatible with theories of oxygen toxicity. Light may not be necessary for ROP to occur, but it may increase the risk.

Long-term results of corneal wedge resections for the correction of high astigmatism.

Abstract: We retrospectively evaluated 41 corneal wedge resections, performed for the correction of high astigmatism in 40 patients who were spectacle and contact lens intolerant. Keratometric astigmatism decreased from an average of 11.7 diopters (range 5 to 22.5 D) preoperatively to 3.5 diopters (range 0 to 10 D) postoperatively, representing a mean reduction of 8.2 D (range 0 to 16.5), or 70%. The length of follow-up averaged 11 months. Twenty-five, 15 and 9 cases had a follow-up of at least 3, 5 and 10 years, respectively. In 16 cases the keratometry readings remained stable over the years. However, in 1 case of Fuchs' endothelial dystrophy (follow-up 13 years) and 5 cases of keratoconus (follow-up 3, 4, 12, 13 and 14 years) the astigmatism gradually increased during the various follow-up periods. In 3 other cases the astigmatism gradually decreased over the years. Corneal wedge resection is an effective technique for managing high corneal astigmatism. The results remain stable over the years except in some patients with keratoconus.

Dermolipoma: characteristic CT appearance.

Abstract: Dermolipomas are choristomas usually located at the external canthus. Clinically they can be confused with dermoid cysts. Preoperative diagnosis of a dermolipoma is important because the surgical approach is less aggressive than for dermoid cysts. We describe the clinical aspects of ten patients with a dermolipoma and demonstrate the posterior extension of these lesions by CT.

Effect of light on oxygen-induced retinopathy in the rat model. Light and OIR in the rat.

Abstract: The purpose of this study was to establish whether exposure to intense lighting favors the development or aggravates experimental oxygen-induced retinopathy in the new-born rat. Five groups of Wistar rats were studied. The control group was maintained for the first 14 days of life under conditions of cyclical (12L∶12D) lighting at 12 Lx in room air. Two other groups were subjected, for the same amount of time, to semi-darkness (2 Lx; 12L∶12D), one with room air and the other with supplemental 80% oxygen. The final two groups were exposed to the same room air and hyperoxic treatments under intense lighting conditions (600 Lx; 12L∶12D).

The human motion VEP as a function of size and eccentricity of the stimulation field.

Abstract: A 'motion onset VEP' was elicited by the onset of a pattern drift. The amplitude of the most distinct wave (AN200) was determined on the following stimulation conditions: eccentricity, 0 to 23 deg; velocity. 1.5 to 16 deg/s; spatial frequency, 0.19 to 2.1 c/deg; and stimulation field size, 0.2 to 160 deg2, AN200 remained constant at any degree of eccentricity if stimulation field size, velocity, and spatial frequency were M-scaled according to Rovamo-Virsu's M-equations. AN200 decreased as a function of eccentricity if field size and velocity were kept constant (spatial frequency had minimal effect). The size of the cortical representation field (Sc) in this case varied with change in eccentricity (stimulation field size constant). In another experiment, it varied by change in stimulation field size (eccentricity constant). For both conditions, AN200 was proportional to log Sc.

Oscillatory potentials as predictors to amplitude and peak time of the photopic b-wave of the human electroretinogram

Abstract: The oscillatory potentials are viewed by many as small oscillations of a high-frequency domain that ride on the b-wave of the electroretinogram. A study of electroretinograms and oscillatory potentials performed in 25 normal subjects was undertaken to substantiate my claim that oscillatory potentials are fast retinal potentials that are integrated to form the b-wave. The prominence of the OPs on the ascending limb of the b-wave was found to be only weakly correlated (r = -0.37) to the amplitude of the oscillatory potentials (measured in the 100-1000 Hz recordings). There was, however, a high correlation (r = 0.78) between the prominence of the oscillatory potentials and their frequency domain as determined by the peak-to-peak timing. Furthermore, the peak-to-peak timing of the oscillatory potentials was highly correlated with the b-wave peak time (r = 0.86) as well as with the 'a-wave trough to b-wave peak' time (r = 0.90), while the amplitude of the oscillatory potentials was correlated to the amplitude of the b-wave (r = 0.78). Interestingly, when combining the amplitude of the oscillatory potentials with the time interval between oscillatory potentials 2 and 3 and 3 and 4, a higher correlation (r = 0.88) was found with the b-wave amplitude. The latter finding would support my claim that the b-wave represents an integration (amplitude as a function of time) of the oscillatory potentials.