RSS 1.0SUNY Optometry Masters Thesis Collection
Recent Submissions
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ON-OFF Pathway Function in Amblyopia"Purpose To understand the effect of amblyopia on ON and OFF pathway asymmetries. This pilot study used a novel, eye-tracking, saccadic-based perimetric test. Methods 8 eyes of 4 amblyopic subjects (mean age 24 ± 2.4 years) and one eye of 4 age-matched control subjects (mean age: 27 ± 3.6 years) were tested using a novel perimetric test. We tested 4 Michelson contrast levels ranging from 15 to 5% at 3 annular eccentricities: 5- 10, 11-20, 21-30 degrees from fixation (2.5-degree radius circle). Each contrast level was comprised of 579 trials. Each test location was repeated 3 times for both light and dark stimuli, with 6 repeats in each of two blind spot positions. Stimuli, light or dark squares which varied in size as a function of eccentricity, were presented on a binary noise background. The angular difference between the target location and eye position following a saccadic movement to the target location and reaction time were measured for every trial. Percentage of undetected targets, the angular difference between the target location and eye position following a saccadic movement to the target location, and reaction time were measured for every trial. Hardware consisted of a head mounted display equipped with an eye tracker (HTC VIVE embedded Tobii) with a refresh rate of 90 Hz, a max luminance of 110 cd/m2, and a horizontal field of view of 60 degrees. Unity (version 2017) software was used to generate the stimuli. Results At low contrasts (less than 10%), the amblyopic eyes of patients have a greater percent error rate (12.12 ± 17.56 %, p = 3.2 x 10-17, Wilcoxon tests for all statistical comparisons), detect fewer targets (6.98 ± 16.28 %, p = 8.5 x 10-8) and have longer reaction times (101.2 ± 193.8 msec, p = 1.13 x 10-11) when compared to fellow eyes. However, the fellow eyes of amblyopic subjects have greater percent error rate (8.03 ± 8.64 %, p = 0.0013), detect fewer targets (8.68 ± 7.2 %, p = 2.9 x 10-4) and have similar reaction times (29.8 ± 110.6 msec, p = 0.811) to the control subjects. At a low contrast (6%), the difference between amblyopic and fellow eyes across eccentricities was significantly larger for light than dark stimuli in percentage of errors (5.37 ± 10.43%, p = 0.031), undetected targets (4.91 ± 6.5%, p = 0.001) and reaction time (44.2 ± 96.7 msec, p=0.026). This difference was not apparent at 5% contrast due to the high rate of errors for both light and dark stimuli. Conclusion These results provide further support to previous work indicating that amblyopia affects ON more than OFF pathways. However, given our very limited sample size, further evaluation is necessary. The use of the perimetric test in this study, along with continuing advancements, may enable this work to continue in a clinical setting."
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Effects of Induced Myopia on Inner Peripapillary Retinal Layer Structures"Purpose: Myopic eye growth exerts mechanical stretching that can reshape the retinal architecture. This study investigates the longitudinal impact of induced myopia on peripapillary retinal layer structures in the common marmoset (Callithrix jacchus), a non-human primate model with close anatomical and developmental similarities to the human eye. Methods: Thirteen juvenile marmosets were reared under binocular negative lens defocus for 23 weeks to induce myopia (six controls and seven treated). Serial measurements of cycloplegic refractive error and vitreous chamber depth were conducted alongside spectral domain optical coherence tomography (SD-OCT) imaging to assess regional peripapillary retinal layer thickness. Segmentation of OCT scans were used to quantify changes in total and individual retinal layers across four quadrants. Results: Control animals exhibited age-related peripapillary thickening, particularly in the temporal quadrant of multiple inner retinal layers. In contrast, myopic eyes showed reduced thickening, and thinning at times, especially in the inferior and temporal regions. In particular, a significant thinning was observed in the inferior quadrants of the ganglion cell and inner plexiform layer in treated eyes. A regression analysis identified the inferior total retinal thickness and ganglion cell layer thickness to be the strongest predictors of vitreous chamber depth. Conclusions: Induced myopia in marmosets leads to regional thinning of inner peripapillary retinal layers, suggesting early remodeling due to asymmetric retinal expansion. These findings contribute to understanding structural biomarkers of myopic progression and support the use of the marmoset model in translational vision science research."
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ANALYSIS OF GLIA CHARACTERISTICS IN THE RD10 RETINITIS PIGMENTOSA MOUSE IN COMPARISON TO THE MÜLLER GLIA DICER-CKO MOUSE, TWO MODELS OF RETINAL DEGENERATION"Purpose The retinal degeneration (RD) 10 mouse is a well-studied animal model that develops Retinitis Pigmentosa (RP) due to a mutation in rod photoreceptors. Müller glia (MG) are the predominant glia in the retina, have essential roles in the healthy retina, but become reactive in response to retinal damage and contribute to secondary neuronal loss. An in-depth characterization of MG in the RD mouse has not reported yet. Furthermore, molecular alterations in MG, i.e., the depletion of the enzyme Dicer1, results in photoreceptor loss resembling the phenotype of RP. Therefore, similarities in the molecular profile of MG in both models could suggest a putative common regulatory mechanism of glial alteration. The aim of this study was to characterize and compare MG in the central and peripheral retina in the RD10 mouse and the MG-specific Dicer1 conditional knock-out mouse. Methods To visualize MG in both degeneration models a MG-specific reporter mouse (Rlbp1-CreER:tdTomatostop flox/flox) was crossed with the RD10 or the Dicerflox/flox mouse (Dicer knock-out, referred to as cKO). Histological analysis was performed by means of immunofluorescence staining and confocal microscopy imaging. Retinal cross sections of 1-, 3-, and 6-months old mice were evaluated with regard to overall retinal histology, MG number and their glial protein expression pattern in both the center and periphery. Results The RD10 mouse displayed retinal thinning as early as one month of age with proliferating MG at the early phase and degenerating MG at later phases. These MG were glial fibrillary acidic protein (GFAP) positive and vimentin positive at all time points analyzed. The Dicer-cKO mouse displayed proliferating MG at early stages but not obvious degeneration was found at this time. At later stages, MG number declined in central retinal areas which were also significantly degenerated. GFAP and vimentin upregulation was not found in Dicer-cKO MG. Conclusion The MG reporter mouse is a very useful tool to study MG number and behavior in models of retinal degeneration including the RD10 mouse and the Dicer-cKO mouse. Moreover, it appears that the deletion of Dicer1 prevents MG from becoming reactive and initiating gliosis. This suggests that molecular manipulation of MG could be utilized to attenuate gliosis and subsequent degenerative events in retinal diseases."
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Uncorrected Myopia Affects the Visual Resolution of OFF Pathways More Than ON Pathways"Introduction: The balance between ON- and OFF-pathway responses is believed to play a significant role in the progression of myopia in children [1, 2]. In a recent study, we found that uncorrected myopic children exhibited poorer visual acuity—approximately 1.5 logMAR lines—when identifying dark optotype stimuli (primarily processed by the OFF-pathway) compared to light stimuli (processed by the ON-pathway). In this study, we examine whether this asymmetry between light and dark stimuli is associated with the severity of myopia. Methods: Cycloplegic refractive error was used to calculate the spherical equivalent (SEQ). Based on SEQ, children aged 8 to 12 years were divided into two groups: a myopic group (−0.75D to −6.00D, N=11) and a non-myopic control group (−0.38D to +1.25D, N=15). Corrected and uncorrected right eye visual acuity (VA) was assessed using E-ETDRS charts with either light or dark optotypes presented at full contrast (on dark or light backgrounds, respectively) in randomized order, repeated twice with a 30-minute interval. Light-dark asymmetry was quantified using the ON-OFF VA ratio. Results: The myopic group demonstrated significantly greater light-dark asymmetry compared to the control group (1.15 ± 0.08 vs. 1.00 ± 0.02, p < 0.001), indicating that uncorrected myopic eyes experience increased difficulty in resolving dark optotypes relative to light ones. Furthermore, a modest yet statistically significant correlation was observed between spherical equivalent (SEQ) and the ON-OFF visual acuity ratio (r = 0.38; t = −2.4, p = 0.02), suggesting that this asymmetry becomes more pronounced with increasing severity of myopia. Conclusions: These findings suggest that uncorrected myopic eyes have more difficulty perceiving dark compared to light stimuli, and that this ON-OFF pathway imbalance is associated with the degree of myopia. Further research is warranted to explore the potential of light-dark asymmetry as a biomarker for monitoring myopia progression in children."
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Differences between ON and OFF cortical function in patients with amblyopia"Purpose: Evidence from psychophysical studies indicate that amblyopia affects ON more than OFF visual pathways. This prospective study aims to directly measure the effect of amblyopia on cortical responses driven by ON and OFF pathways with visual evoked potentials (VEPs). Methods: Adults (18-65 years) with amblyopia (strabismic, anisometropic, mixed, or deprivational) and control subjects with binocularly normal-corrected vision were recruited. All subjects were screened with ATS-EDTRS best-corrected visual acuity (BCVA) and Randot Preschool stereoacuity. To be eligible, amblyopes must have an interocular difference of ≥2 logMAR (logarithmic minimum angle of resolution) lines, and controls must have BCVA within 1 logMAR line in both eyes and a stereoacuity of ≤100 arcsec. VEP was recorded with a portable lightweight headset (Wearable Sensing Inc.) that sampled the visual cortex with 9 dry electrodes. The visual stimuli presented were checkerboards with half checks equal to the background and half darker or lighter than the background (100% and 50% contrast, viewed through right eye, left eye, or both eyes, 900 trials). Eye fixation was monitored with an eye tracker (Eyelink 1000). The reliability of cortical responses was quantified with a correlation index that selected the 20 stimulus trials generating the strongest responses and measured the average of all possible correlations between trial pairs. Results: We tested eight amblyopic subjects and two controls. The average amplitude of the cortical responses was marginally stronger for the AE than FE, but the difference was not statistically significant (23.00 ± 4.65 vs. 22.68 ± 5.62 microV, p > 0.05, Wilcoxon test). Differences in response amplitude between FE and AE were weaker for light than dark stimuli but also did not reach significance (-0.38 ± 4.81 vs. -0.26 ± 7.22 microV, p > 0.05, Wilcoxon test). The mean correlation index was larger in the FE than the AE, but this difference was not statistically significant (0.43 ± 0.20 vs. 0.40 ± 0.22, p > 0.05, Wilcoxon test). The FE-AE differences in mean correlation index were larger for light than dark stimuli, but again, the differences did not reach significance (0.09 ± 0.20 vs. -0.03 ± 0.22, p > 0.05, Wilcoxon Test). Within-subject comparisons in select individuals revealed variable VEP patterns. Control subjects showed no interocular or ON/OFF differences, while amblyopic participants displayed mixed results. Some were consistent with the hypothesis of reduced ON pathway strength in the AE, whereas others showed the opposite or no difference at all. Conclusion: While some amblyopes may show ON/OFF pathway asymmetries, these effects are not consistently observable across all cases. Variability is inherent with VEP and may limit the ability to detect ON/OFF pathway differences at the group level, emphasizing the need for individualized analysis in amblyopia research."
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The Effect of Biofeedback Training on Accommodation During MFCL Wear in Young Adults"Purpose: Myopia currently affects 22.9% of the global population and it is estimated that 50% of the world population will be myopia by 2050. Multifocal contact lenses (MFCLs) are effective in reducing myopia progression, but with variable efficacies. One potential reason could be reduced accommodation through the MFCLs. This is due to the near add in the MFCLs superimposing peripheral myopic defocus or reducing peripheral hyperopic defocus, which then leads to a relaxation of accommodation. The drawback, however, is that if myopes reduce accommodation when reading through the MFCLs, it may reduce peripheral myopic defocus and ultimately, reduce the treatment effect of MFCLs. Recent studies show that auditory biofeedback training can help improve accommodation through the MFCLs in young myopes both immediately after the training and one week later, which may ultimately improve the efficacy of MFCLs. In this study, we evaluated, in young adults, the time course of biofeedback training in increasing accommodative response during MFCL wear and if weekly repetition of the biofeedback training and increased training duration could lead to longer lasting results. Methods: This was a prospective study with 4 weekly visits. Twenty-seven young myopes with normal accommodation and binocularity were fit with Biofinity single vision (SV) and MF (+2.00 Add center distance) CLs over both eyes and randomized to 3 groups: (1) Group 1 – single training, (2) Group 2 – regular repeated training, and (3) Group 3 – extended repeated training. During Visit 1 for all 3 groups, accommodation was measured first through the SVCLs, then through the MFCLs before and after an auditory biofeedback training at four different dioptric distances: 2.5D, 3D, and 4D. During Visits 2 and 3 for group 1, accommodation through the MFCLs was measured without the biofeedback training. During Visits 2 and 3 for group 2, accommodation was measured before and after auditory biofeedback training. During Visits 2 and 3 for group 3, accommodation was measured before and after an extended auditory biofeedback training (twice the duration). Visit 4 for all groups consisted of measuring accommodation through the MFCLs without auditory biofeedback training. Results: Analysis of the data confirmed that accommodative responses were reduced in MFCLs compared to SVCLs. One session of auditory biofeedback training was also shown to increase the accommodative responses in MFCLs at the 2.5 D, 3 D, and 4D distances and the effect of the training lasted for at least one week as supported from the data pooled together of all subjects. In subjects who received the training in the first session, effects of the training lasted for the entire month. However, increasing the number of trainings (as performed for Group 2 subjects) or the duration of the training (as performed for Group 3 subjects) did not significantly further increase the efficacy of the biofeedback training. Conclusion: Biofeedback training could potentially be used as an adjunct treatment for slowing down myopia progression when coupled with MFCL wear. Since one training of auditory biofeedback training showed success in increasing accommodative responses, it may be worthwhile to determine what changes can be made in the execution of the training to yield the best results. While this study was performed on young adults, future directions may include performing a similar study design on myopic children due to the greater accommodative capabilities of children in comparison to adults. "
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Investigating a Link Between Visual Function and Menstruation"Throughout the course of a normal menstrual cycle, a woman’s hormone levels vary greatly and these changes cause the body to react in a multitude of ways. However, there is little previous research remarking on the link between visual function and the menstrual hormones. The objective of this study was to determine how visual function is impacted at different stages in the menstrual cycle. Specifically, tests of high and low contrast visual acuity, lag of accommodation, color vision, and critical flicker fusion frequency were recorded in order to examine changes in visual function over a normal menstrual cycle. This study recruited all subjects from the SUNY College of Optometry as well as the areas surrounding the school between the ages of 18-30 years old. 12 female subjects not currently pregnant or on birth control medication as well as 3 male control subjects will participate. Subjects performed the required clinical measurements 5 days a week for 5 weeks (25 total days) to encompass the entire menstrual cycle. In addition, female subjects also reported the day of their last menstrual cycle and any other perceived changes in visual function throughout the month. No significant difference was found between the female and male groups or within the female group throughout the month for any parameter tested. Further parameters should be measured in the future in order to gain a clear image of how menstruation impacts the whole ocular system."
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ON-Pathway Visual Acuity Deficits in 8-12 Years Old Children with Unilateral Amblyopia"Purpose: Conventional recognition visual acuity (VA) tests, using black optotypes on white background, do not detect ON-pathway amblyopia deficits. This pilot study tests the hypothesis that VA testing with white optotypes on black background is more sensitive in detecting amblyopia than with black optotypes on white background. Methods: Two groups of children aged 8-12 were enrolled. The amblyopic group (N=13) had a best-corrected VA of 20/32 or worse in the amblyopic eye and an interocular VA difference of ≥0.2 logMAR. The control group (N=16) had best-corrected VA equal to or better than 20/25 and had an interocular VA difference of ≤0.1 logMAR. Participants’ VA were tested monocularly with an ETDRS program using the Amblyopia Treatment Study protocol and reported as a Score. Two optotype polarities were randomized, and tests were repeated after 30 minutes. VA in Scores were compared between amblyopic, fellow, and control eyes for both polarities. Results: For amblyopic eyes, the mean VA Score was significantly lower for white than for black optotypes (57.85±10.72 vs 61.46±10.10, p<0.001), indicating that amblyopic eyes had more difficulty seeing white than black optotypes. For fellow eyes, the mean Score was marginally significantly lower for white than for black optotypes (85.77±3.23 vs 87.73±4.61, p=0.03). No significant differences were found in control eyes (87.70±3.38 vs 88.02±4.03, p=0.63). Conclusions: VA in amblyopic eyes is 3.6 letters (~0.07 logMAR) worse when measured with white optotypes than black optotypes, indicating that white optotypes have higher sensitivity in detecting amblyopia ON-pathway deficit."
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The effects of glare, luminance and contrast on visual acuity (VA)"Purpose: Clinical measurements of VA are typically obtained under optimal conditions using high contrast optotypes. However, these conditions are not representative of real-life environments where observers are frequently faced with low contrast, low luminance targets accompanied by significant degrees of glare. Accordingly, the aim of the present study was to measure VA under both optimal and suboptimal conditions in younger and older adults. Method: The study was performed on 30 older (ages 50-71 years) and 30 younger (21-28 years) subjects. High (0.0 log unit) and low (1.05 log unit) contrast VAs were tested using the Adhikari Carter Feigl Zele logMAR chart. VA was measured both with and without a 0.3 neutral density (ND) filter to create low luminance conditions, as well as both with and without an LED glare source being directed into the eye. Results: The average change in VA under the low contrast and low luminance conditions were 1.22 logMAR (p < 0.001) and 0.94 (p < 0.001), respectively. Average VA changed by -0.77 in the presence of glare (p < 0.001). There were no significant age effects noted between the two groups (p=0.25). Interaction effects were significant between luminance and contrast (p < 0.001) as well as between luminance, contrast and the presence of glare (p < 0.001) in both age groups. Conclusions: The results demonstrate that reducing contrast and luminance produced a significant decline in VA in younger and older adults. This finding has considerable clinical significance, for example when driving at night, where a subject with excellent VA in the examination room might exhibit very poor VA under degraded conditions. Clinical measurements should include assessment of visual performance under sub-optimal conditions. "
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Digital eye strain and pupillary response to blue light"Purpose: Digital eye strain (DES), a multifactorial condition affecting millions worldwide, often implicates blue light as a contributing factor. While blue light blocking filters are marketed to alleviate DES symptoms, evidence supporting their efficacy remains limited. Intrinsically photosensitive retinal ganglion cells (ipRGCs), exhibiting peak sensitivity to blue light, are involved in regulating pupil constriction and circadian rhythms. Notably, blue light elicits varying ipRGC-mediated pupil responses between individuals. This study investigated a potential association between self-reported DES symptoms and individuals' ipRGC-mediated pupil responses. Method: Twenty-five visually normal subjects, 18-30 years of age, participated in the experiment. They began by reading random words on a tablet computer for 20 minutes. Before and after the reading task, participants completed a symptom survey to assess DES severity. Subsequently, they were exposed to a blue background light of varying intensities within the dome of a pupilometer. The pupil light reflex was recorded for each intensity and analyzed. Results: The pupil diameter's EC50 value in response to blue light exhibited a statistically significant correlation with the total symptom score (p=0.0003), extrinsic symptom score (p=0.006) and intrinsic symptom score (p=0.0003). Similarly, the LogEC50 value also demonstrated a statistically significant correlation with total symptom score (p=0.002), extrinsic symptom score (p=0.02), and intrinsic symptom score (p=0.001). Conclusion: Subjects with greater DES scores exhibited reduced sensitivity when adapting to blue light, indicating a potential link between ipRGC function and DES symptoms. "
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Upregulation of Gap Junction Connexins in GlaucomaGlaucoma is a leading cause of irreversible blindness, which is characterized by a progressive degeneration of the optic nerve and loss of retinal ganglion cells (RGCs). Glaucoma currently affects 3.5% of individuals aged 40 to 80 years, and the incidence of glaucoma is increasing together with life expectancies (Wagner et al., 2022). There is strong evidence that intercellular communication via gap junctions (GJs) facilitates secondary cell death, by means of the so-called “bystander effect” is which dying cells releases toxins that lead to the death of neighboring cells to which they are coupled (Akopian et al., 2014; 2017). Pharmacological blockade of GJs or genetic deletion of GJ subunit connexins Cx36 (Akopian et al., 2017) or Cx43 (Batsuuri et al., 2023) showed an increase in neuronal survivability by greater than 70% in glaucomatous retinas providing clear evidence that GJs can mediate secondary cell death, which can account for loss of most retinal neurons. Since Cx36 is expressed by GJs between retinal neurons and Cx43 is expressed between glial astrocytes, there are potentially two separate pathways that may underlie cell loss in glaucoma. This raises the important question of whether these pathways are independent mechanisms for cell death or are interdependent. Interestingly, both Cx36 and Cx43 are upregulated in glaucomatous retinas (Akopian et al., 2017; Batsuuri et al., 2023). Therefore, to assay the interdependence of bystander death mediated by Cx36- and Cx43-expressing GJs in glaucoma, we determined if their upregulation were interconnected. Understanding the potential interdependence of these two GJ-mediated bystander cell death pathways would help define potential targets for neuroprotection in glaucoma.
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Diurnal Variations in Scotopic and Photopic Flash Electroretinogram"Purpose: To determine the pattern of the diurnal variations in retinal responses measured with the full-field scotopic and photopic electroretinogram (ERG). Methods: Full-field flash ERGs were recorded with DTL electrodes after pupil dilation from 6 normal healthy subjects at 3AM, 9AM, 3PM and 9PM (one subject at 6AM, 12PM, 6PM, 12AM) on four separate days using a desktop ganzfeld ERG recording system (Diagnosys LLC). The test scotopic ERG test protocol consisted of 40 minutes of dark-adaptation followed by recordings with brief (<4ms) blue (440nm) test flashes in the range of 1x10-6 to 20 scot cd.s/m2. The photopic ERG test protocol consisted of 15 minutes of light-adaptation to 8 scot cd/m2 blue background followed recordings with brief red (690nm) test flashes in the range of 6x10-2 to 6.4 phot cd.s/m2 on the adapting background. The Scotopic Threshold Response (STR), scotopic and photopic b-waves and the Photopic Negative Response (PhNR) amplitudes were plotted as a function of test flash intensity and fit with the Naka-Rushton equation to extract the saturated amplitude (Vmax), slope (n) and semisaturation constant (K) parameters for each ERG measures. The fit parameters were plotted as a function of the time of the day when the recordings were performed to examine their diurnal variation. Saliva samples were collected and salivary melatonin was assayed (Salimetrics LLC) at 8 different time points during the day from each subject on one separate occasion and prior, during and after each ERG session. Results: The Vmax of the ERG measures demonstrated statistically significant systematic diurnal variation. The Vmax of the Scotopic b-wave and the STR did not change appreciably from 3AM to 9AM but thereafter gradually increased to reach a maximum value at 9PM. The difference in the mean value of the Vmax between the 3AM and 9PM recordings was statistically significant for the scotopic b-wave (173uv and 338uv, p=0.0013) and the STR (15uv and 22uv, p=0.03). with the halfway point for this amplitude increase being 11AM. The Vmax of the photopic b-wave and PhNR showed a steep increase from 3AM to 9AM and thereafter a more gradual increase at 3PM to slightly reduce again by 9PM. The difference in the mean value of the Vmax between the 3AM and 3PM recordings was statistically significant for the photopic b-wave (60uv and 92uv, p=0.04) and the PhNR (36uv and 61uv, p=0.019) with the halfway point for this amplitude increase being 6AM. Salivary metalonin concentration on average started to show an increase around 9AM from daytime baseline value of 1 pg/ml to a peak of 16 pg/ml around 3AM and then reduced to 4 pg/ml by 9AM. Conclusions: The maximal amplitude of the scotopic ERG parameters are achieved later during the day compared to the photopic ERG parameters that achieve maximal amplitudes at earlier times. The saturated amplitude of scotopic and photopic ERG measures have their lowest values around 3AM when salivary melatonin concentration is maximal. The relationship between the diurnal rhythms of melatonin and retinal function as measured by the ERG warrants further investigation. "
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Retinal Ganglion Cell Function in Diabetes Mellitus"Purpose: To evaluate retinal ganglion cell function in diabetic patients with no retinopathy. Methods: The full-field photopic flash electroretinogram (ERG) was recorded from 11 diabetics patients (55.75 ± 14.77) and 11 age-matched controls (50.17 ± 15.18) with a ColorBurst TM handheld stimulator (Diagnosys LLC). The visual stimuli consisted of 40 ms duration red (640 nm) test stimuli of strengths ranging from 0.25 cd/m2 to 1500 cd/m2 delivered on and constant rod-saturating blue (470 nm) background of 7cd/m2. The Intensity response function of the PhNR and the b-wave amplitudes plotted as a function of stimulus strength were fitted with a generalized Naka-Rushton equation of the form V(I)/Vmax = In /(In +Kn ) and the fit parameters of K, n and Vmax were compared between the diabetic patients and control subjects. Visual field sensitivity was measured by behavioral perimetry using the Humphrey Visual Field Analyzer 10-2 and 24-2 SITA-standard tests. Structural parameters of the retina, namely area of the foveal avascular zone (FAZ), superficial vascular plexus density (SVD), deep vascular plexus density (DVD)and Retinal Nerve Fiber Layer (RNFL) thickness were measured with the Heidelberg OCTA. Linear regression analysis was used to study the correlation between affected ERG fit parameters and aspects of visual field sensitivity and retinal structural parameters. Results: The mean ages were not significantly different between the diabetic patients and control subjects. The average value of the PhNR semi-saturation constant for the diabetic patients and control subjects were 83.64+39.96 and 32.21+20 and the difference was statistically significant (p=0.0054). The average value of the PhNR slope for the diabetic patients and control subjects were 0.83+0.19 and 1.39+0.17 and the difference was statistically significant (p=0.0000018). PhNR Vmax was not statistically significantly different between the diabetic patients (30+7.12) and controls (30.18+6.45). The parameters of the Naka-Rushton fits to the b-wave responses were not significantly different between the two groups. A positive correlation was seen between the semi-saturation constant of the PhNR in diabetics and self-reported HbA1c% (r=0.72, m=22.8, p=0.029) and a negative correlation was observed between the semi-saturation constant of the PhNR and 10-2 mean sensitivity (r=0.67, m=-0.03, p=0.02). A positive correlation between the semi-saturation constant and SVD (r=0.66) and DVD (r=0.67) were seen in control subjects, whereas negative correlation was seen in diabetics eyes (r=0.5 and r=0.4). Conclusion: Retinal ganglion cell sensitivity is compromised in diabetic patients with no retinopathy as indicated by an increase in the value of the full-field PhNR semi-saturation constant while responses of their input neurons, namely bipolar cells, as reflected by the b-waves is relatively normal. Compromise of retinal ganglion cell function may underlie the earliest visual sensitivity changes diabetic patients. Further longitudinal studies are warranted to determine whether changes in ganglion cell function precedes changes in superficial and deep vessel density. "
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Development of a Pediatric Digital Eye Strain Questionnaire"Objectives: The aim of the present study was to create a valid and reliable method of determining to what extent children experience symptoms of digital eye strain (DES). Methods: The initial version of the pediatric digital eye strain questionnaire was developed using a literature review, consultation with experts and a pretest performed on 6-8-year-olds. A pilot test using a revised version of the questionnaire was performed on 70 6-12-year-old participants. Content validity was established by discussion with an expert. Construct validity was evaluated by performance of the pediatric DES questionnaire and the Computer Vision Syndrome Questionnaire (CVS-Q) by optometry students. Test-retest repeatability was tested using Bland Altman analysis and a significant cutoff score was established using the linear regression equation to determine the value equivalent to the previously assigned cutoff for the CVS-Q of 6. Results: The questionnaire evaluated 12 DES symptoms’ frequency in a simple, self-administrable method. The mean total score of the pilot test was 7. 45% of the participants in the pilot test had a significant score for DES. The questionnaire had excellent test-retest repeatability and construct validity r=0.81 (p<0.001). No significant correlation was found between the reported total number of hours of screen time per week and the total symptom score (r = 0.30, p = 0.47). Conclusions: This study indicates that almost half of children may be experiencing adverse ocular symptoms associated with screen use. The questionnaire provides a valid and reliable method for identification of DES symptoms in children ages 6-12 years. Optometrists, pediatricians and parents alike may find use for this questionnaire to evaluate for digital eye strain in children. "
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Cognitive Demand, Concurrent Viewing Distance, and Digital Eye StrainPurpose: Digital devices are now ubiquitous in modern daily life. Reports of digital eye strain (DES) symptoms are occurring frequently, particularly since the recent COVID-19 pandemic. Despite its prevalence, the mechanisms underlying DES have not been fully elucidated and there is currently no clinically proven treatment. Given that both mental effort and the accommodative and vergence demand have been associated with DES, the purpose of this study was to evaluate the relationship between the cognitive demand of the task, mode of presentation, working distance and symptoms of DES. Method: The study was performed on 30 young, normally-sighted individuals. Each participant completed four trials, each of which included a 30-minute reading task. The four conditions entailed: (1) a cognitively demanding task performed on a digital device (tablet) and (2) a less cognitively demanding task performed on the same digital device. Trials (3) and (4) were identical to (1) and (2) except that the tasks were performed on printed paper. Both prior to and immediately following each 30-minute task, subjects completed a 10 question DES symptom survey. For all four conditions, subjects wore a Clouclip, a spectacle-mounted device which uses infrared technology to monitor the working distance objectively every 5 seconds. Results: While all four 30-minute reading tasks induced symptoms of DES, the increase in symptoms was greater for the cognitively demanding tasks (p= <0.0001). However, there was no significant difference in symptoms between performing the tasks on paper versus the tablet computer (p=0.83). With regard to working distance, there was no difference between the four testing conditions (p=0.11). However, all tasks showed a similar significant reduction in working distance (p=0.001), on average from 32 to 30cm, over the first ten minutes of the task, with the working distance remaining relatively stable after this initial period. Conclusion: These results suggest that cognitive demand plays a greater role in DES than the mode of presentation. In addition, we found no evidence that working distance varies with cognitive demand or the method of presentation. However, it did decrease during the first 10 minutes of each trial. Further work is needed to explain the role of cognitive demand in DES.
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Effects of Test Flash Duration on the Photopic Negative Response (PhNR) of the Flash ElectroretinogramPurpose: The Photopic Negative Response (PhNR) of the cone mediated electroretinogram (ERG) is a slow potential with negative polarity that appears after the b-wave. The PhNR originates from the electrical activity of retinal ganglion cells (RGCS) and has clinical utility. The PhNR is typically recorded to a brief (<4ms) test flash, we explored the effect of increasing the stimulus duration on the PhNR amplitude of normal subjects in an ongoing attempt to optimize the stimulus conditions for its clinical use. Methods: ERGs were recorded with DTL electrodes from normal subjects (N=10) in the age range 23-53 years using the ColorBurst handheld ganzfeld stimulator and hardware from Diagnosys (Lowell, MA). The stimuli consisted of red test flashes on constant blue background (8 phot cd.s/m.sq). The test flashes were either brief stimuli (<4 ms duration) in the range of 0.00625 - 6.4 phot cd.s/m.sq or longer duration (20-80 ms) in the range of 0.125-1500 cd/m.sq. A new algorithm in the Espion software with objective sweep selection based on various noise and artifact identification criteria was used to average repeated responses at each test flash intensity. The PhNR amplitude of the averaged waveform was plotted as a function of test flash intensity and fitted with the standard Naka-Rushton equation. The saturated amplitude (Vmax), slope (n) and semisaturation constant (K) derived from the fits were analyzed. The student t-test was performed to compare the fit parameters across different test flash durations with correction for multiple comparisons using the Holm’s method. Results: Vmax for the brief stimulus was 20+7 microvolts and increased to 23+2 microvolts for 20 ms duration stimuli. With further increase in stimulus duration the PhNR Vmax was 34+8 v, 42+10 v and 37+10 v for 40 ms, 50 ms and 60ms duration stimuli and thereafter reduced to 29+7 v for an 80 ms stimulus duration. The Vmax amplitude differences between the brief and longer duration stimuli were statistically significant only for the 40 ms (p=0.04), 50 ms (p=0.001) and 60 ms (p=0.01) after correcting for multiple comparisons. Responses to stimulus durations up to 60 ms demonstrated a single PhNR trough and for longer duration stimuli two PhNR troughs were observed one following light onset after the b-wave and another following light offset. Conclusions: The saturated PhNR amplitude is larger for longer duration stimuli and is maximal in the range of 40-80 ms duration. The larger PhNR amplitude at the intermediate test flashes likely reflect the summation of the PhNR to stimulus onset and offset and could potentially have more value in assessing retinal ganglion cell function in patients with disease affecting the optic nerve and/or inner-retinal neurons.
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Accommodation over Time in Children Wearing Multifocal Soft Contact Lenses for Myopia ControlIntroduction The prevalence of myopia and its ocular complications increases each year worldwide and the complications of myopia are predicted to become the leading cause of blindness by 2050 (Holden Ophthamology 2016). Common therapies for myopia management include low-dose atropine, bifocals or Progressive Addition Lenses (PALs), orthokeratology (OK), and multifocal contact lenses (MFCL). One potential mechanism for OK and MFCLs to reduce myopia progression is by imposing peripheral myopic defocus on the retina. MFCL wear can reduce accommodation compared with single vision contact lenses (SVCL), potentially reducing peripheral myopic defocus and causing variable efficacies of MFCLs (Gong OVS 2017). The change in accommodation with MFCL use varies between MFCL designs. Auditory biofeedback training can decrease the accommodative lag during MFCL wear in young adults (Wagner Sci Rep 2020). We assessed: Differences in accommodative lag between children using low-dose atropine, OK, and MFCLs compared to a single vision spectacle control. Differences in accommodation between different MFCL designs. Differences in accommodation between viewing through SVCLs and MFCLs. The effect of biofeedback training on accommodation in children during MFCL wear. Methods Myopic children habitually using low-dose atropine, OK, or MFCLs as well as myopic children not undergoing myopia management (spectacle control) (19 male/ 24 female) were recruited from the Pediatric and Myopia Management Clinics at the University Eye Center, SUNY College of Optometry. Low dose atropine (n = 11), OK (n = 5), and spectacle control (n = 11) subjects’ accommodative lag was measured using an infrared (IR) photorefractor, using a stimulus at 0, 2.5, 3, and 4D. For the MFCL subjects (n = 17), accommodation through SVCLs and their habitual MFCLs before, after, and 1 week following biofeedback training were measured identically to the other subjects at the same distances. Differences in accommodative lag were measured using mixed effects multiple linear regression adjusting for accommodative stimuli. Results There was no significant difference between accommodation in the low-dose atropine (p = 0.8), OK (p = 0.3), and MFCL (p = 0.3) groups compared to the spectacle control. Eyes wearing MFCLs exhibited significantly increased lag of accommodation compared with SVCLs prior to the biofeedback training (SV vs. MFCL, p < 0.05). Specifically, eyes viewing through Biofinity MFCLs showed a significantly greater lag than MiSight (p < 0.05). Biofeedback training showed a tendency to decrease lag immediately following biofeedback training (p = 0.2) and significantly decreased lag 1 week later (p < 0.01). Both immediately and one week later, subjects that showed lower pretreatment accommodation had significantly greater decreases in lag following biofeedback training (p < 0.05). Conclusions Our findings show that pediatric subjects wearing MFCLs for myopia management show an increased accommodative lag compared to wearing SVCLs. The lag of accommodation while viewing with MFCLs differs between MFCL designs. Biofeedback training can significantly decrease lag in children during MFCL wear one week later, similar to previous findings (Wagner Sci Rep 2020). Subjects who displayed the greatest accommodative lag prior to the train showed the biggest improvements in accommodation before the biofeedback training, suggesting individuals with low accommodation while viewing through MFCLs use may yield the greatest benefit from biofeedback training. Biofeedback training may be effective in increasing the amount of peripheral myopic defocus during MFCL wear and thus increase the efficacy of MFCL wear for myopia management in children.
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Regional Differences in the Relationship Between Retinal Structure and ON-OFF Pathway Function in Myopic PatientsPurpose: The purpose of this study was to measure the effect of myopia on ON and OFF pathway asymmetries displayed between 5˚ to 30˚ of eccentricity and examine the structure-function relationship between retinal thickness and visibility of light and dark stimuli in eccentric quadrants of myopic eyes. Methods: Eighteen eyes were randomly selected from human subjects and all myopic subjects underwent testing with habitual soft contact lens correction. Subjects underwent ON-OFF perimetric testing in the test eye. The complete procedure is referenced and discussed in the body of the manuscript. Stimuli were presented at various contrasts across 30-degrees of the visual field and stimuli increased in size as a function of eccentricity. Structural and functional testing, including ultra-wide field macular optical coherence tomography (OCT), 30-2 static automated perimetry (SAP) mean sensitivity, peripheral autorefractive (AR) measurements, and axial length (AL), were also measured. All testing, except axial length measurements, were taken with subjects fully corrected in soft contact lenses. Results: There was a statistically significant positive correlation between AL and combined light and dark errors across the entire testing area of 5-30° (p=0.0019) as well as each eccentric range (5-10° p=0.0389; 11-20° p=0.0015; 21-30° p =0.0008). There was a statistically significant positive correlation between errors to light stimuli as a function of AL across the entire testing area of 5-30° (p=0.0251), 11-20° (p=0.0207) and 21-30° (p =0.0178). There was a statistically significant positive correlation between AL and dark stimuli errors across the entire testing area of 5-30° (p=0.0461), 11-20° (p=0.0424) and 21-30° (p =0.024). There was no statistically significant correlation when analyzing errors to light and dark stimuli separately at the 5-10° eccentricity. There was a statistically significant negative correlation between RE and combined light and dark errors across the entire testing area of 5-30° (p=0.0444) and a statistically significant negative correlation at the most peripheral eccentric range of 21-30° (p=0.0128). Subjects displayed higher errors to light stimuli over the entire testing area 5-30° (p=0.0166) and 21-30° (p=0.0007), but not at 5-10° or 11-20° (5-10° p=0.7043; 11-20° p=0.2572). The quadrant with the greatest average retinal thickness (IT) was associated with the lowest %errors (6.45 ± 6.56) and highest visual field mean sensitivity (VFMS, 30.9 ± 1.08 dB), whereas the quadrant with the least average retinal thickness (SN) was associated with the highest % errors (22.77 ± 15.93, p=8.91 x 10-9 for IT vs SN comparison) and among the lowest MS (29.43 ± 1.34, p=0.0020 for IT vs SN comparison). Conclusion: Higher levels of myopia are associated with greater response errors during ON-OFF perimetric testing, with higher error rates in response to light targets compared to dark targets. Both findings are most pronounced at the 21–30-degree eccentricity and have a stronger correlation with axial length compared to refractive error. Higher rates of error on ON-OFF perimetry correspond to thinner retinal thickness in the corresponding retinal quadrant. The highest average percent errors on ON-OFF perimetric testing were present in the superonasal visual field, which coincides with the thinnest total retinal thickness in the corresponding region of the retina (interotemporal). Better understanding of the structural and correspond to thinner retinal thickness in the corresponding retinal quadrant. The highest average percent errors on ON-OFF perimetric testing were present in the superonasal visual field, which coincides with the thinnest total retinal thickness in the corresponding region of the retina (interotemporal). Better understanding of the structural and corresponding functioning relationship between ON-OFF perimetric testing and retinal thickness may enhance our understanding of myopic refractive development.
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Effects of Scheduled Breaks on Digital Eye Strain and the 20-20-20 RulePurpose: The use of digital devices has increased substantially over the past two decades across all age groups, particularly during the recent pandemic, for both vocational and avocational purposes. Digital eye strain (DES) involves a range of visual and ocular symptoms that can be categorized into oculomotor/refractive abnormalities or dry eye symptoms. The so-called 20-20-20 rule, whereby individuals are advised to fixate an object at least 20 feet (6m) away for at least 20 seconds every 20 minutes is widely cited as a method for minimizing symptoms. Unfortunately, there is little or no peer-reviewed evidence to support this so-called rule. Accordingly, the aim of the present investigation was to determine whether 20-second breaks are indeed effective in reducing the adverse effects of digital device usage, and if so, then to identify the specific schedule that has the greatest success in controlling symptoms. Methods: The study was performed on 30 young, visually-normal subjects who performed a highly demanding 40-minute reading task from a tablet computer. The task required them to read random words and to identify which began with a specific letter chosen at random by the experimenter. The task was undertaken on four separate occasions, with 20-second breaks being allowed every 5, 10, 20 or 40 minutes (i.e., no break), respectively. Both before and immediately after each trial, subjects completed a questionnaire regarding ocular and visual symptoms experienced during the session. Additionally, both reading speed and task accuracy was quantified during the trial. Results: A significant increase in post-task symptoms (with respective to the pre-task value) was observed for all four trials (p<0.001). However, there was no significant effect of scheduled breaks on reported symptoms (p=0.70), reading speed (p=0.93) or task accuracy (p=0.55). Conclusions: While widely cited as a treatment option, these results do not support the proposal of using the 20-20-20 rule as a therapeutic intervention for DES. Future studies should look at alternative break schedules to determine their efficacy.
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Effects of Gingko biloba on Systemic and Retinal Blood CirculationIntroduction: The use of alternative medicine has increased in recent years due to its minimal side effects and holistic approach to healthcare. Ginkgo biloba extract (GBE) is a natural antioxidant derived from leaves of the Maidenhair tree and is known to improve blood vessel health. However, its effect on the retinal circulation is not fully understood. The purpose of this study is to examine the effect of GBE oral supplements on the retinal circulation. Methods: Blood pressure (Omron HEM-705CP), intraocular pressure (Canon T2 non-contact Tonometer), and blood flow velocities in the ophthalmic artery, central retinal artery, and short posterior ciliary arteries (Color Doppler imaging, Sequoia) were obtained from participants aged 22 to 36 with good ocular and systemic health. Measurements were performed between 12-5pm to control for circadian rhythm effects at 3 study visits: 1 week before baseline at pre-supplement visit (T-1), at baseline (T0) and after 4 weeks of 240mg/day GBE supplementation at post-supplement visit (T4). Ocular perfusion pressure (OPP) was calculated as OPP = 2/3 * (Mean Arterial Pressure – IOP). Results: Thirteen participants were recruited (5m, 8f; 25.54 ± 3.64 years). No significant changes in systemic blood pressure, OPP or retinal circulation were observed between pre-supplement visit (T-1) and baseline (T0) prior to GBE supplementation. However, the ophthalmic and short posterior ciliary arteries peak systolic velocities increased from baseline (T0) to post-treatment (T4) (ophthalmic artery baseline ave ± SD: 18.97 ± 6.67cm/s; post-treatment:24.33 ± 6.90cm/s; short posterior ciliary artery baseline: 10.56 ± 1.87cm/s; post-treatment: 11.58 ± 1.97cm/s; both p < 0.05). The increases in ophthalmic and short posterior ciliary arteries peak systolic velocities did not correlate with changes in systolic BP, diastolic BP, or OPP. Discussion: Our preliminary data suggests that 240mg/day of Ginkgo biloba extract (GBE) may increase blood flow in two major retinal ocular arteries. Such increase appears independent from changes in systemic blood pressure or OPP.
