Significant Reduction In Visual Acuity Research Articles

Effects of Miosis on the Visual Acuity Space under Varying Conditions of Contrast and Ambient Luminance in Presbyopia.

Background: Presbyopia is an age-related ocular condition, typically affecting individuals aged over 40 years, characterized by a gradual and irreversible decline in the eye's ability to focus on nearby objects. Correction methods for presbyopia encompass the use of corrective lenses, surgical interventions (corneal or lens based), and, more recently, the FDA-approved topical administration of 1.25% pilocarpine. While prior research has demonstrated the efficacy of daily pilocarpine eye drop application in enhancing near visual acuity by increasing the depth of focus leveraging the pinhole effect, limited knowledge exists regarding its influence on visual acuity under varying conditions of contrast and ambient luminance. Methods: This study aims to investigate the impact of these variables on visual acuity, employing the VA-CAL test, among 11 emmetropic and 11 presbyopic volunteers who reported subjective difficulties with near vision. This study includes evaluations under natural conditions with a pinhole occluder (diameter of 2 mm), and subsequent administration of 1% pilocarpine (Pilomann, Bausch + Lomb, Laval, Canada). Results: The VA-CAL results demonstrate the expected, statistically significant effects of contrast and ambient luminance on visual acuity in both emmetropic and presbyopic volunteers. Furthermore, in emmetropic individuals, the application of pilocarpine resulted in a statistically significant reduction in visual acuity. In contrast, presbyopes did not exhibit statistically significant differences in the visual acuity space under either the pinhole or pilocarpine conditions when compared to natural conditions. Conclusions: The pharmacological treatment of presbyopia with pilocarpine eye drops, intended to enhance near vision, does not adversely affect visual acuity in presbyopes. This suggests that pilocarpine may offer a viable alternative for individuals averse to wearing corrective eyewear.

Visual function changes along the continuum of Alzheimer's disease

Aims/Purpose: The progression of Alzheimer's disease (AD) is manifested by a gradual transition from a preclinical phase, characterized by asymptomatic pathological alterations, to an advanced phase of AD accompanied by cognitive impairment. The aim of this study was to explore visual function along the entire AD continuum.Methods: Each participant underwent a comprehensive visual examination, with only visually healthy individuals being selected for the study. The study comprised the following groups: controls (n = 53), positive family history of AD (FH+) (n = 13), mild cognitive impairment (MCI) (n = 23), mild AD (n = 25), and moderate AD (n = 21). The study analysed the results of visual acuity (VA) and contrast sensitivity (CS).Results: A significant reduction in VA was identified between the control group and the MCI, mild AD and moderate AD groups. CS showed significant changes in all cognitive impairment groups compared to the control group and the FH+ group at spatial frequencies of 12 and 18 cpd. In contrast, significant differences were only observed at spatial frequencies of 3 and 6 cpd between the cognitively impaired groups, starting from moderate AD, with no detectable decrease in CS during the MCI phase. No differences were detected between the control group and the FH+ group. The tests showed a positive correlation with the Mini Mental State Examination score and exhibited a favourable predictive ability in the presence of memory impairment, with higher predictive performance observed in the advance stages of AD.Conclusions: The presence of alterations in VA and CS can be observed as early as the MCI stage in individuals with AD. Recognizing the continuum of AD holds significant significance in early detection, with visual examination offering a straightforward and cost‐effective diagnostic tool for AD. Healthcare professionals can leverage this knowledge to gain a better understanding of the progressive nature of the disease.

Spezifische OCT-Veränderungen bei einer neuen Mutation im RS1-Gen bei X-chromosomal-rezessiver Retinoschisis

X-linked retinoschisis (XLRS) is a rare vitreoretinal dystrophy caused by molecular genetic changes in the RS1 gene. It usually manifests itself at a young age with symmetrical splitting within different layers of the retina and leads to a significant reduction in visual acuity. Correct diagnosis at older ages is difficult due to nonspecific changes in OCT scans. We report the morphological changes in OCT scans at different stages of life in a family with XLRS and a novel mutation in the RS1 gene. Our 78-year-old index patient presented with visual disturbances that he had experienced since his childhood. After a detailed anamnesis, complete clinical examination and measurement with SD-OCT, we performed germline genetic testing using whole blood DNA on the index patient, his clinically unaffected daughter and her clinically affected son. The OCT examination of the index patient showed nonspecific atrophic macular changes on both sides. A fundoscopy of the 8-year-old grandson showed the typical macular star pattern. The OCT scan showed the typical retinoschisis of the macula. The genetic analysis revealed thepreviously undescribed pathogenic variant c.487T>G; p.Trp163Gly in the RS1 gene in all 3patients. The typical fundus image and OCT pattern, which are absent in the 78-year-old patient, are also present in childhood with the novel RS1 mutation. Our case shows that even with nonspecific changes in the OCT scans, a detailed family history can provide important information on X-linked recessive inheritance and thus for an appropriate molecular genetic diagnosis, so that rare retinal diseases can be diagnosed even at an advanced age.

Age-related laryngoscopic visual acuity.

BackgroundEndotracheal intubation by direct laryngoscopy is a mainstay of advanced airway management performed both in the prehospital environment and in the Emergency Department. Many factors may affect the quality of view during direct laryngoscopy, one of them being the visual acuity (VA) of the intubator under these demanding conditions. While some individual variation in VA is to be expected in younger populations, VA naturally deteriorates in older populations particularly beyond the age of 40 years. This study aimed to describe VA in a younger (n=19) and an older (≥40 years of age, n=20) cohort of intubators at baseline and during simulated adult laryngoscopy, and to compare VA between these two age cohorts.MethodsA baseline near VA test was done using a Sloan Early Treatment Diabetic Retinopathy Study (EDTRS) near vision chart at 40 cm under ambient indoor light. Participants in both age cohorts were then requested to perform laryngoscopy using an airway simulator at 40 cm viewing distance and again at a viewing distance of their choice. Both binocular and monocular VA were tested using a near VA chart placed anterior to the vocal cords of the airway trainer. VA was quantified using the logarithm of the minimum angle of resolution (logMAR). Differences in VA between age cohorts were assessed using independent samples t-tests and differences within age cohorts were assessed using paired samples t-tests.ResultsBinocular and monocular near VA was significantly reduced in the older cohort compared to the younger cohort at baseline (both eyes −0.129 logMAR; p = 0.04, right eye −0.147 logMAR; p = 0.005, left eye −0.197 logMAR; p = 0.002). Within each age cohort VA was significantly reduced during laryngoscopy at a fixed viewing distance (younger; both eyes −0.111 logMAR; p < 0.001, right eye −0.095 logMAR; p < 0.001, left eye −0.105 logMAR; p < 0.001; older; both eyes −0,08 logMAR; p < 0.001, right eye −0.110 logMAR; p < 0.001, left eye −0.065 logMAR; p = 0.01) but this was improved by reducing viewing distance.ConclusionIncreased age was associated with a significant reduction in VA at baseline and during laryngoscopy, which can be partially compensated for by adjusting viewing distance. Although it is currently unknown to what extent this age-related reduction of VA might negatively affect time to place an endotracheal tube or success of placement under direct vision, older intubators should be aware of this effect and consider specialized corrective eyewear in order to maintain an adequate level of VA.

Changes in Sensory Functions in Response to Living in an Extreme Underwater Saturation Environment

The present challenges of long duration spaceflight and other missions in extreme environments include changes of sensory functions, including vision impairment and changes in taste perception. In order to monitor and improve astronaut health and performance during long duration spaceflight and future spaceflight missions we studied sensory functions in response to living in an extreme environment during the NASA Extreme Environment Mission Operation (NEEMO) 23. The Aquarius Reef Base is located at 20 m (66 ft) with 2.6 atm (air) pressure inside the habitat, while levels of CO2 are elevated similarly to the International Space Station.This study assessed the changes in visual acuity and taste perception in 6 NEEMO 23 subjects (2 males, 4 females) 1 day before the mission, during the mission at half time and 1 day post mission. Visual changes were assessed using the NIH Toolbox protocol, while changes in taste perception were measured using solutions containing concentrations of either salty, sweet and bitter flavors in three different concetrations on the side of the tongue and in full mouth.We observed a trend of decreased salty and bitter taste sensation in the habitat and post mission, compared to baseline, while the sweet taste sensation did not change. When testing the full mouth, the salty taste sensation significantly decreased post mission, compared to baseline at low or medium concentration. Bitter taste sensation significantly decreased at low concentration in habitat and post mission, compared to baseline. At medium concentration the bitter taste sensation significantly decreased post mission, compared to baseline and in‐habitat, while at high concentration it significantly decreased post mission, compared to baseline. There was a signifcant reduction in the Overall Raw and in Overall Uncorrected Vision Scores between baseline and post mission indicating a significant reduction in visual acuity during the 9 days mission that was not restored immediately after the mission.Living in a saturation environment decreases certain sensory modalities that may persist for an unknown length of time after the exposure. Diminished sensitivity to taste can alter nutritional status and chemosensory changes may also relate to space sickness, stress and psychological factors, while changes in vision may impair operational tasks. These data indicate that mitigation strategies need to be developed and tested in space analog environments.Support or Funding InformationKetone Technologies LLC provided partial funding for the study. SIFT provided partial salary for CA.

Outcomes of Micropulse Transscleral Cyclophotocoagulation in Eyes With Good Central Vision.

This study is the first to report micropulse transscleral cyclophotocoagulation (MP-TSCPC) use in only good vision patients. MP-TSCPC significantly reduced intraocular pressure (IOP) and glaucoma medication use without any significant reduction in visual acuity at every postoperative follow-up point. To evaluate outcomes of MP-TSCPC in eyes with baseline best-corrected visual acuity (BCVA) of ≥20/60. A retrospective review of patients who underwent MP-TSCPC at Mayo Clinic and Ross Eye Institute from July 2016 to August 2017 with BCVA of ≥20/60, and a minimum of 3 months follow-up. A total of 61 eyes of 46 patients (68.80±17.12 y) underwent MP-TSCPC with a mean follow-up of 10.2±3.1 months. Mean IOP and mean number of glaucoma medications used were significantly reduced from baseline at every follow-up time point (P<0.0001). At month 12, mean IOP was reduced 40.2% from baseline with 85.4% of the patients having an IOP reduction of ≥20%, and mean glaucoma medication use reduced by 0.82±0.53 with 79.6% of the patients having a reduction of ≥1 medication. There was no significant reduction in BCVA from baseline at any follow-up point (P>0.05), except for 10 eyes with a vision loss of ≥2 lines and 5 out of 10 eyes had cataract progression. The probability of complete success (IOP range, 6 to 21 mm Hg or ≥20% IOP reduction; BCVA loss ≤2 lines, no reoperation for glaucoma) was 74.14%, 83.61%, 84.21%, and 75.0% at months 1, 3, 6, 12, respectively. The probability of qualified success (above criteria for IOP, no reoperation and BCVA loss >2 lines) was 81.03%, 91.80%, 94.74%, and 93.75% at months 1, 3, 6, 12, respectively. MP-TSCPC should be considered earlier in the management of glaucoma and can possibly be offered as an alternative to incisional glaucoma surgeries.

Ophthalmologic manifestations in Taiwanese patients with mucopolysaccharidoses.

BackgroundMucopolysaccharidoses (MPSs) are a group of rare lysosomal storage disorders characterized by the accumulation of glycosaminoglycans in various tissues and organs. Ocular problems that affect the cornea, trabecular meshwork, sclera, retina, and optic nerve are very common in these patients. However, there was limited literature focusing on comprehensive ocular findings in different types of MPS.MethodsWe retrospectively reviewed the clinical ophthalmologic features and electrodiagnostic results of 50 Taiwanese patients with a diagnosis of MPS (34 males and 16 females; age range, 1.1–34.9 years; nine with MPS I, 17 with MPS II, 17 with MPS IV, and seven with MPS VI).ResultsAmong 44 patients with available data for visual acuity, 15 patients (34%) had a visual acuity of less than 0.5 (6/12) equivalent in their better eye, including 71% of those with MPS VI, 38% with MPS IV, 29% with MPS I, and 14% with MPS II. Severe corneal opacities existed in 57% of MPS VI patients and 11% of MPS I patients, compared with none for MPS II and MPS IV patients. Among 80 eyes with available data of refraction, 11 eyes (14%) had myopia (≦−0.50 D), 55 eyes (69%) had hyperopia (≧0.50 D), and 55 eyes (69%) had high astigmatism (≧1.50 D). Ocular hypertension was found in 45% (28/62) of eyes. There were 16% (14/90), 11% (10/90), 13% (12/90), 31% (27/86), and 79% (30/38) of MPS eyes with lens opacities, optic disc swelling, optic disc cupped, retinopathy, and visual pathway dysfunction, respectively. Intraocular pressure was positively correlated with the severity of corneal opacity (p < 0.01).ConclusionsOcular complications with significant reduction in visual acuity are common in MPS patients. Diagnostic problems may arise in these patients with severe corneal opacification, especially for those with MPS VI and MPS I.

Measurement of Contrast Sensitivity Using the M&amp;S Smart System II Compared with the Standard Pelli–Robson Chart in Patients with Primary Pterygium

Background : Contrast sensitivity (CS) is widely used as a measure of visual function in research and clinical settings. CS is regarded as an important visual parameter, detecting subtle reductions in vision prior to significant reduction in visual acuity. Methods : We examined the agreement between the gold-standard Pelli-Robson chart and a computerized test termed the M&S Smart System II (MSSS-II) in patients with primary pterygium. Ninety-three patients (93 primary pterygium eyes) who visited an ophthalmology clinic were selected. The patients were randomly assessed for CS using the MSSS-II or Pelli-Robson chart. The primary outcome was agreement in log units between these two tests in the assessment of CS in patients with primary pterygium. Results : The mean and standard deviation of CS measurement in the two tests were comparable (1.22 ± 0.56 vs. 1.21 ± 0.57 log units, respectively, p = 0.083). The Bland-Altman plot revealed that the mean difference between the two charts was 0.0016 log units (standard deviation: 0.009 log units) with narrow limits of agreement of -0.0186 to 0.0186. Conclusions : MSSS-II provides an alternative for the clinical assessment of CS using a computerized method that describes the status of visual function in patients with primary pterygium.

Effects of Regular Physical Activity on the Visual Analyzer and the General Condition of Children and Adolescents

Purpose.to study the effect of physical exertion on the visual analyzer and the general functional state in children and adolescents who regularly engage in sports.Material and Methods.The study was conducted in a group of 600 children and adolescents aged from 8 to 17 years who were divided into two groups of 300 people: the I group — “athletes” (regularly engaged in sports), the second group — “schoolchildren” (those engaged in sports less than 3 hours per week). Each group was divided into two subgroups of 150 people — “emmetrops” and “myopes”. The parameters of visual acuity, axial eye length, indices of regional eye hemodynamics were evaluated.Results.After 12 months, the group “athletes” showed a statistically significant decrease in refraction on average by 0.14 ± 0.18 on the background of stable visual acuity. In the group “schoolchildren” there was a significant reduction in visual acuity without correction by 0.06 ± 0.19 (p = 0.004) and refractive indices by 0.35 ± 0.61 (p &lt; 0.001) on the average. After 12 months, among the emmetrops, myopia was diagnosed in 6 % of cases in the “athletes” group and 10 % in the “schoolchildren” group. Among the “myopes” in both groups there was a significant increase in the body mass index and the number of persons with impaired functional state of the musculoskeletal system in the form of a violation of posture and shape of the foot in comparison with the “emmetrops”.Сonclusion.Regular physical activity can be considered as one of the factors preventing the development and progression of myopia, and functional disorders of the musculoskeletal system in the form of violation of posture and shape of the foot and excessive body weight — as possible risk factors for the development of myopia.

Subthreshold Laser and Subliminal (Micropulse) Laser in Diabetic Retinopathy and Diabetic Macular Edema

Diabetic macular edema (DME) is one of the main causes of a significant reduction in visual acuity in working-age adults and is the most common cause of visual acuity loss from diabetic retinopathy. Most of the studies have shown that the ability of the conventional laser to maintain or improve visual acuity is limited, possibly because of the development of retinal scars, which decrease the potential for improved visual acuity. Subthreshold laser and subliminal (micropulse) laser has the potential to reduce DME with better visual acuity results compared with conventional laser, as it does not cause collateral damage in the retina. These lasers cannot cause permanent damage to the retina. This article mentions subthreshold laser, and subliminal (micropulse) laser in diabetic retinopathy and diabetic macular edema.

Central Retinal Vein Occlusion in Younger Swedish Adults: Case Reports and Review of the Literature.

Purpose:To investigate associated systemic diseases, other conditions, visual outcome, ocular complications and treatment in Swedish patients younger than 50 years with central retinal vein occlusion (CRVO) and reviewing the literature.Methods:Twenty-two patients with CRVO, younger than 50 years, were examined with full-field electroretinography (ERG) within 3 months after a thrombotic event, or were periodically examined and were observed for at least 6 months. In 18 of these patients, the initial retinal ischemia was studied using the cone b-wave implicit time in the 30 Hz flicker ERG. Fifteen patients also underwent fluorescein angiography. Optical coherence tomography (OCT) was performed in 14 patients. The patients studied were divided into two groups, non-ischemic and ischemic, which were compared. All patients underwent ocular and systemic examination, as well as complete screening for thrombophilic risk factors.Results:Of the 22 patients, 15 had non-ischemic type of CRVO and 7 the ischemic type. Patients with non-ischemic CRVO showed significantly improved visual acuity (VA) at the final examination (p=0.006). Patients with ischemic CRVO showed no significant reduction in VA at the final examination (p=0.225). Systemic hypertension (27% in non-ischemic CRVO and 29% in ischemic CRVO) was the most prevalent systemic risk factor for CRVO. The mean central foveal thickness (CFT) decreased significantly from 402.3±136.2 (µm) at the initial examination to 243.8±48.1 (µm) at the final examination in the non-ischemic group (p=0.005). The mean initial CFT was 444.5±186.1 (µm) in the ischemic CRVO group, which decreased to 211.5±20.2 (µm) at the final visit (p=0.068). Pigment dispersion syndrome (PDS)/pigmentary glaucoma (PG), ocular hypertension and dehydration were equally frequent; four patients each (18%) out of 22. The clinical course of 4 younger patients with PDS/PG are described.Conclusion:The patients with non-ischemic CRVO showed significantly improved VA and significantly decreased CFT at the final examination. Systemic hypertension was the most prevalent risk factor for CRVO. Younger adults with CRVO also had a high prevalence of PDS/PG, ocular hypertension and dehydration. This study highlights the importance of careful IOP monitoring, and the need to investigate possible PDS/PG and to obtain an accurate history of the patient including alcohol intake and intense exercise.

Ultraviolet Corneal Crosslinking

This review presents basic information on UV corneal crosslinking. The method is widely used in ophthalmology to treat various types of ectasia, which are characterized by progressive degenerative changes in the cornea, associated with its thinning , hazing and scarring, which leads to a significant reduction in visual acuity. Crosslinking is based on ultraviolet (UV) irradiation of the cornea wavelength 370 nm in the presence of riboflavin, leading to photochemical intracorneal interactions. As a result of crosslinking of collagen treatments, an increase of strength and mechanical properties of the cornea, stops the progression of the disease. The article displays the steps of the method development and the ways of its implementation are described especially occurring biomechanical, biochemical, morphological and ultrastructural changes, as well as the main areas of clinical application of riboflavin-UV-A-induced crosslinking of cornea.

The influence of diabetes mellitus on the management and visual outcome of patients with uveitis

Uveitis and diabetes mellitus (DM) are potentially blinding conditions, especially in the developed world (Durrani et al. 2004; Zhang 2010). High doses and long-term courses of systemic corticosteroids are used to treat sight-threatening uveitis (Lightman 1991). However, this may lead to the induction of type 2 DM (Gulliford et al. 2006). The combined effect of uveitis and DM on visual outcome and uveitis management strategies has not been well addressed. This study aimed to examine the visual outcome and changes in treatment strategies among patients with uveitis following the diagnosis of DM. In this study, 1654 hospital case notes were reviewed of patients attending the uveitis clinic at Moorfields Eye Hospital in London, UK. This study was approved by the hospital's Research Governance Committee (Protocol LIGS 10201, Visual Loss in Uveitis). Patients were included if they had uveitis for at least 1 year and were later diagnosed with type 2 DM. The best corrected visual acuity (BCVA) was recorded at baseline (the year prior to the diagnosis of DM), at time of DM diagnosis and onwards at yearly intervals. Causes of reduced vision (≥0.3 Logmar from baseline) were recorded. Management of uveitis relapses were compared pre- and postdiagnosis of diabetes. Successful uveitis relapse control was defined as reduction in anterior chamber cells scores to ≤0.5+ and/ or an improvement in the vitritis haze score to <1+ and/or cystoid macular oedema (CMO) elimination with no or residual intraretinal cysts based on optical coherence tomography within 3 months of starting an intervention. A total of 96 eyes of 52 patients were identified. The average BCVA was 0.31 ± 0.06 logMAR at baseline and 0.44 ± 0.07 logMAR at the time of DM diagnosis. Multivariate linear regression analysis using generalized estimating equation methods was carried out, adjusting for CMO and cataract surgery. There was a significant reduction in the average BCVA compared to baseline by 0.11 logMAR at the time of diabetes diagnosis (p = 0.02, 95% CI 0.02–0.20), by 0.13 logMAR at 1 year (p = 0.006, 95% CI: 0.04–0.19) and by 0.10 logMAR at 2 years postdiagnosis (p = 0.03, 95% CI 0.01–0.20). No significant reduction in BCVA was observed during the third, fourth and fifth years onwards (p > 0.05). The main causes of reduced vision at the time of diabetes diagnosis were cataract progression (12%) and new onset CMO (10%). The proportion of relapses treated with systemic steroids significantly reduced from 70% prediabetes to 56% postdiabetes diagnosis. Adding local steroid injection while on systemic steroids increased from 4% to 15% (p = 0.003, chi-square test). No significant difference was observed in the uveitis relapse treatment success preversus postdiabetes diagnosis (Table 1). Of the 96 eyes with uveitis and DM, one eye developed a clinically significant macular oedema after 3 years and required grid laser treatment, while seven eyes of six patients (7.3%) developed non-proliferative diabetic retinopathy, which occurred at a median of six (range, 2–11) years. While one previous study explored the visual outcome of 36 patients with diabetes who later developed uveitis (Oswal et al. 2013), our study further explores the synergistic effect of uveitis and diabetes by examining the effect of newly diagnosed diabetes on the eyes with uveitis and the effect of diabetes on uveitis treatment strategies. In conclusion, the concurrent diagnosis of DM in uveitis patients is associated with a significant reduction in visual acuity within the first 2 years. More uveitis relapses were treated with local steroid injection rather than increasing systemic corticosteroid dose, without affecting the ability to control uveitis relapses. It is important to optimize treatment protocols for DM and uveitis when occur concurrently.

Repetitive visual stimulation enhances recovery from severe amblyopia

Severe amblyopia, characterized by a significant reduction in visual acuity through the affected eye, is highly resistant to reversal in adulthood. We have previously shown that synaptic plasticity can be reactivated in the adult rat visual cortex by dark exposure, and the reactivated plasticity can be harnessed to promote the recovery from severe amblyopia. Here we show that deprived-eye visually evoked responses are rapidly strengthened in dark-exposed amblyopes by passive viewing of repetitive visual stimuli. Surprisingly, passive visual stimulation rapidly enhanced visually evoked responses to novel stimuli and enhanced the recovery from severe amblyopia driven by performance of active visual discriminations. Thus a series of simple, noninvasive manipulations of visual experience can be used in combination to significantly guide the recovery of visual response strength, selectivity, and spatial acuity in adult amblyopes.

The effect of pupil dilation on driving vision in Canada.

To determine whether there is a clinically significant reduction in visual acuity (VA) or contrast sensitivity (CS), with and without glare, following examination with pupil dilation in patients currently driving. From November 1, 2004, to February 28, 2005, 105 consecutive patients were assessed in our institution. The better eye was assessed pre- and post-dilation with and without glare administered through the Brightness Acuity Tester. VA was assessed using the Early Treatment in Diabetic Retinopathy Study (ETDRS) and Snellen charts. CS was measured using the Vistech VCTS 6500 Chart. With no glare, there was a mean reduction of 4.8 letters read from the ETDRS chart following dilation (p < 0.001). With glare, there was a mean reduction of 7.1 letters (p < 0.001). Compared with patients with initial VA of 20/20, patients presenting with a Snellen VA of 20/25 to 20/40 had a 9.75 relative risk of postdilation VA worse than 20/40, whereas patients with initial VA of 20/40 had a 19.8 relative risk of postdilation VA worse than 20/40. With the addition of glare, these relative risks increased to 13.9 and 28.8, respectively. Without glare, there was a significant reduction in CS after dilation at spatial frequencies of 2.0, 4.0, and 6.0 cycles/degree (p = 0.014, p < 0.001, and p < 0.001, respectively). With glare, there was a greater reduction in CS at these 3 spatial frequencies (p < 0.001 for all). There is a significant reduction in VA and CS after dilation that is further confounded by the effect of glare. This reduction may limit some patients from driving after dilation.

How does normal crowding affect visual acuity?

Abstract Purpose Clinical tests of visual acuity (VA) that employ multiple, neighbouring optotypes assume that visual 'crowding' at the fovea is negligible. Findings from recent studies suggest that crowding effects can affect high contrast acuity thresholds at the fovea. The absence of data to describe the distribution of crowding effects within 'normal' vision makes it difficult to establish when a measured reduction in VA (with crowding) can no longer be considered to be within the normal range and is therefore indicative of abnormal development or pathology. The aim of this study was to quantify the effects of crowding on VA in the normal population. Methods We measured acuity thresholds, with and without crowding, in central vision (i.e. at the fovea and at +/‐1 degree, +/‐1.5 degrees, and +/‐2 degrees) in 80 normal subjects with the age range of 29.3 +/‐10.7 years. The stimulus optotype was a Landolt ring of 100% luminance contrast presented either in isolation or together with four surrounding rings at a distance equal to 1.5 times the diameter of the stimulus, these parameters were selected on the basis of preliminary studies varying the spacing and the number of distracters. Results The threshold stimulus size for correct discrimination of gap orientation increased almost linearly with eccentricity, the presence of distracter rings caused a significant reduction in VA. Conclusion The statistical distribution of the differences between the two measures of VA provides the data needed to define the effects of crowding in “normal” vision. The template extracted from these data is clinically useful to identify those subjects that show abnormal sensitivity to crowding, i.e. amblyopia or early degenerative conditions/ disease.

The effect of pupil dilation on driving vision in Canada

Background: To determine whether there is a clinically significant reduction in visual acuity (VA) or contrast sensitivity (CS), with and without glare, following examination with pupil dilation in patients currently driving.Methods: From November 1, 2004, to February 28, 2005, 105 consecutive patients were assessed in our institution.The better eye was assessed pre- and post-dilation with and without glare administered through the Brightness Acuity Tester. VA was assessed using the Early Treatment in Diabetic Retinopathy Study (ETDRS) and Snellen charts. CS was measured using the Vistech VCTS 6500 Chart.Results: With no glare, there was a mean reduction of 4.8 letters read from the ETDRS chart following dilation (p < 0.001). With glare, there was a mean reduction of 7.1 letters (p < 0.001). Compared with patients with initial VA of 20/20, patients presenting with a Snellen VA of 20/25 to 20/40 had a 9.75 relative risk of postdilation VA worse than 20/40, whereas patients with initial VA of 20/40 had a 19.8 relative risk of postdilation VA worse than 20/40. With the addition of glare, these relative risks increased to 13.9 and 28.8, respectively. Without glare, there was a significant reduction in CS after dilation at spatial frequencies of 2.0, 4.0, and 6.0 cycles/degree (p = 0.014, p < 0.001, and p < 0.001, respectively). With glare, there was a greater reduction in CS at these 3 spatial frequencies (p < 0.001 for all).Interpretation: There is a significant reduction in VA and CS after dilation that is further confounded by the effect of glare. This reduction may limit some patients from driving after dilation.

The management of corneal abrasions in accident and emergency

Recent debate over the use of eyepads and mydriatics for corneal abrasions in ophthalmology departments (Mindin et al., 1996, JAMA 1996; 27: 837) has prompted this review of the management of small corneal abrasions ( < 60% of cornea) in a large teaching hospital accident and emergency (A&E) department. Ninety-nine patients were studied who presented to the Leicester Royal Infirmary A&E Department with a corneal abrasion: 49 were given an eye pad and 50 were not given an eye pad. All patients received chloramphenicol (1%) ointment. There was no significance difference between the two groups in terms of the duration of pain (p > 0.2). Four patients developed corneal infections (two wore an eyepad, two had no eye pad). There was only one patient who suffered a transient but significant reduction in visual acuity ( 6 9 - 6 18 ), following the use of an eye pad and subsequent diagnosis in eye casualty of a dendritic ulcer. It is concluded that accident and emergency treatment of small corneal abrasions is safe and effective if an eye pad is not given. Previous criticisms of A&E management of eye problems (Nayeen and Stansfield, Archs Emerg Med, 1992; 9: 257) are unfounded in this department.

Uveitis associated with rifabutin and macrolide therapy for Mycobacterium avium intracellulare infection in AIDS patients.

Uveitis has been increasingly recognised as a side effect of rifabutin regimens in the prophylaxis and treatment of Mycobacterium avium intracellulare (MAI) infection. This study describes the clinical features and analyses the factors associated with rifabutin induced uveitis. Retrospective observational study. Tertiary care institution, The Royal Hospitals NHS Trust, London. 68 HIV seropositive individuals receiving rifabutin for prophylaxis or treatment of MAI infection. 11 episodes of uveitis occurred in 10 different individuals at a median of 62 days. The disease was bilateral in four and unilateral in the remainder. All subjects experienced ocular pain and photophobia and 9 individuals had a significant reduction in visual acuity. Uveitis was treated with mydriatics and topical steroids and resolved in all cases when rifabutin was stopped. The risk of uveitis was significantly increased with concurrent clarithromycin therapy, Odds Ratio 13.08, 95% Confidence Interval 1.98 to 83.12. Rifabutin can cause a reversible uveitis. This risk is increased with concurrent clarithromycin therapy. Adverse drug interactions can be an important cause of morbidity in patients with advanced HIV disease.

VDU work, contrast adaptation, and visual fatigue

Abstract Prolonged VDU work leads to a number of detrimental changes in visual performance and to frequent complaints about asthenopia, musculoskeletal, and other symptoms. The relationship between changes in contrast adaptation at five spatial frequencies and workrelated symptoms were studied in an experimental approach with two groups, one working 2 h (n=13) and the other 4 h (n = 17). Both groups showed a significant reduction in visual acuity and contrast sensitivity, but there were no significant differences between working two or four hours. The relationship between contrast adaptation and symptoms showed a mixed pattern. For the 2 h group there was significant positive correlation between symptoms and all spatial frequencies. For the 4 h group there were mixed correlations between symptoms and contrast adaptation. The results offer only partial support to Lunn and Bank's hypotheses on contrast adaptation, accommodation control and visual fatigue symptoms. Contrast adaptation saturates after 1-2 h and induces a short term effect on visual fatigue. For longer work periods posture-ergonomic and oculomotor factors will penetrate and dilute the contrast sensitivity effect.