María C. Puell

Mesopic contrast sensitivity in the presence or absence of glare in a large driver population

BackgroundTo evaluate mesopic contrast sensitivity in conditions of glare and no glare in a vehicle driver population, and to explore the effects of age, habitual spectacle correction, photopic visual acuity and driving exposure.MethodsA cross-sectional study was performed on 297 drivers stratified by age into six groups. The mesopic contrast sensitivity was measured in the absence or presence of glare using the Mesotest II (Oculus, Germany) in each subject both with habitual and best spectacle correction. A questionnaire on the subject’s driving habits was completed.ResultsThere were no significant differences between contrast sensitivity measured with habitual or best spectacle correction. In conditions of no glare, the mesopic contrast sensitivity gradually got worse from 51 to 60 years onwards, and from 41 to 50 years onwards in the presence of glare. In both conditions, the total decrease in contrast sensitivity was 0.3 log units. The with-glare and without-glare mesopic contrast sensitivity improved as photopic visual acuity increased. Forty-five per cent of drivers who reported difficulties in driving at night were unable to perform any of the tests with glare, compared to 20% without glare. However, the effect of driving habits on contrast sensitivity was only significant in the oldest age group.ConclusionsThe mesopic contrast sensitivity and glare sensitivity seem to be stable until the age of 50 years, from which point they start to decline at a rate of 0.1 log contrast sensitivity loss per decade. Drivers with poor visual acuity and/or older drivers who avoided night driving presented worse mesopic contrast sensitivity and greater glare sensitivity.

Normal values for photopic and mesopic letter contrast sensitivity.

PURPOSE The exponential increase of patients having refractive surgery has increased the number of patients with night vision disturbances, such as decreased contrast sensitivity. However, there are no standard contrast sensitivity scales in normal persons in the mesopic range. We describe Pelli-Robson contrast sensitivity under photopic and mesopic luminance conditions in a large Spanish population over a wide range of age groups to provide normal values. A further aim was to evaluate the effect of photopic visual acuity on photopic and mesopic contrast sensitivity. METHODS A cross-sectional study was performed on 292 participants stratified by age into six groups. Binocular contrast sensitivity was determined with best spectacle correction using the Pelli-Robson letter chart at 1 m under photopic (85 cd/m2) and mesopic (0.15 cd/m2) luminance conditions. RESULTS Phototopic letter contrast sensitivity began to decrease gradually from the 61 to 70-year-old age group onward, and for mesopic conditions, from the 51 to 60-year-old age group onward. The reduction in mean contrast sensitivity between the oldest and the youngest age groups was 0.20 log units (photopic) and 0.33 log units (mesopic). Loss in contrast sensitivity due to luminance (two successive triplets) increased slightly with age. Both photopic and mesopic letter contrast sensitivity significantly improved as photopic visual acuity increased. CONCLUSIONS Under mesopic conditions, Pelli-Robson contrast sensitivity began to decline 1 decade earlier than under photopic conditions and was affected by visual acuity. Normal values for mesopic contrast sensitivity could be of help in deciding whether mesopic function is normal or a decrease in contrast sensitivity is pathologic in nature.

Impaired Mesopic Visual Acuity in Eyes with Early Age-Related Macular Degeneration

PURPOSE To determine photopic and mesopic distance high-contrast visual acuity (HC-VA) and low-contrast visual acuity (LC-VA) in eyes with early age-related macular degeneration (AMD). METHODS Measurements were made in 22 subjects with early AMD and 28 healthy control subjects. Inclusion criteria included a photopic HC-VA of 20/25 or better. Distance VA was measured using HC (96%) and LC (10%) Bailey-Lovie logMAR letter charts under photopic (85 cd/m(2)) and mesopic (0.1-0.2 cd/m(2)) luminance conditions. RESULTS Mean mesopic distance HC-VA and LC-VA were significantly worse (0.1 logMAR and 0.28 logMAR, respectively) in the early AMD group than in the control group. Under mesopic conditions, the mean difference between LC-VA and HC-VA was significantly greater in the early AMD (0.45 logMAR) than the control group (0.27 logMAR). Mean differences between mesopic versus photopic HC-VA and mesopic versus photopic LC-VA were significantly greater in the early AMD than the control group (0.13 and 0.32 logMAR of difference between the means, respectively). Sensitivity and specificity were significantly greater for mesopic LC-VA than for mesopic HC-VA (Receiver Operating Characteristics, area under the curve [AUC], 0.94 ± 0.030 and 0.76 ± 0.067, respectively). AUC values for photopic HC-VA and LC-VA were below 0.70. CONCLUSIONS Visual acuity testing under low luminance conditions emerged as an optimal quantitative measure of retinal function in early AMD.

Normal Values for the Size of a Halo Produced by a Glare Source

PURPOSE To determine the size of a halo in the visual field induced by bright light in healthy eyes of all ages using the Vision Monitor (MonCv3; Metrovision, Pérenchies, France) and to assess the repeatability of the method. METHODS Measurements were made in the right eyes of 147 healthy subjects (mean age: 48.2 ± 16.2 years) who were classified into six age groups. Using the Vision Monitor, optotypes of low luminance were presented at a distance of 2.5 m. The visual angle subtended by the radius of the halo was calculated in minutes of arc (arc min). The repeatability of the method was determined in a subset of 37 subjects older than 50 years by calculating the Bland-Altman coefficient of repeatability. RESULTS The mean radius of the halo was 111.6 ± 39.8 arc min. Halo radius started to increase significantly from the age of 50 to 59 years. The relationship between halo radius and age (r = 0.65; P < .0001) was described by fitting a power function to the data. Halo size was independent of gender. The coefficient of repeatability of the method was ±44 arc min. CONCLUSIONS Halo size increases with age following a power model. The normal halo size values provided could help clinicians distinguish between normal or abnormal glare problems. The intersession repeatability observed for halo size measurement indicates this method could be useful for assessing visual impairment caused by glare.

Effect of driver distraction and low alcohol concentrations on useful field of view and frequency-doubling technology perimetry

Purpose:  To investigate the effects of a mental psychometric task that simulates the distraction effect of a hands‐free mobile phone and of low alcohol concentrations (0.3–0.5 g/l) on two tests: the useful field of view (UFOV) and frequency‐doubling technology (FDT) perimetry.

Relationship between macular pigment and visual acuity in eyes with early age-related macular degeneration.

Purpose:  Today the extent to which MP impacts visual function in early AMD remains unclear. This study examines the relationship between macular pigment optical density (MPOD) and high‐contrast visual acuity (HC‐VA) and low‐contrast visual acuity (LC‐VA) in eyes with early age‐related macular degeneration (AMD).

Effect of a yellow filter on mesopic contrast perception and differential light sensitivity in the visual field.

Purpose: Previous studies on the effects of yellow filters in the visual performance have been carried out, presenting discrepancies among the different investigations. Our study reports the influence of the yellow filter without residual reflections on contrast perception and differential light sensitivity (DLS) under mesopic conditions. Methods: Contrast sensitivity, low contrast visual acuity and luminance thresholds in the central visual field (30°) were measured in a group of 38 adult subjects with and without a coated yellow lens (482-nm cut-off) under mesopic conditions. Results: The contrast sensitivity mean was significantly better with the filter at low- and middle-range spatial frequencies (1.5 cycles/degree p = 0.002 and 6 cycles/degree p = 0.02). At 5% contrast, the mesopic low contrast visual acuity improved significantly (p = 0.004) when interposing the yellow filter. The increase in DLS was statistically significant [e.g. all visual fields p = 0.0003 and macular visual field (9.5°) p = 0.00001] through the yellow filter on the different established areas of the visual field (30°). Conclusions: The yellow filter without residual reflections had a positive influence on the brightness and contrast perception of healthy subjects, for which its use would be beneficial under mesopic conditions.

Soft contact lens fitting after intrastromal corneal ring segment implantation to treat keratoconus

PURPOSE To assess the feasibility of fitting a lathed soft toric contact lens (STCL) after the implant of intrastromal corneal ring segments (ICRSs) to treat keratoconus. METHODS Six months after ICRS implantation, 47 eyes of 47 patients (18-45 years) were fitted with a STCL. In each eye, we determined refractive error, uncorrected (UDVA) and corrected distance visual acuity (CDVA), and keratometry and asphericity measures. The outcome of STCL fitting was defined according to CDVA as successful (≤0.2logMAR) or unsuccessful (>0.2logMAR). Patients in the unsuccessful group were refitted with a piggy-back (PB) system. The above variables and the change in CDVA observed after STCL and PB lens fitting from spectacle CDVA were compared in the two groups. RESULTS STCL fitting was successful in 75%, 66.66% and 0% of the ICRS implanted eyes with stages I-III keratoconus, respectively. Spectacle-CDVA was 1.5 lines better and mean corneal power was 3.62D lower in the successful STCL group. In this group, the difference in cylinder axis between spectacles and STCL was 24.25° lower. PB refitting achieved a PB-CDVA ≤0.2logMAR in all cases. A similar difference in the CDVA change achieved by contact lenses versus spectacles was observed in the successful STCL and PB refitted groups. CONCLUSION STCL fitting is a feasible option in a large proportion of patients implanted with ICRS. When these lenses are unsatisfactory, a PB system is a good alternative.

Changes in visual function under mesopic and photopic conditions after intrastromal corneal ring segment implantation for different stages of keratoconus

Purpose To analyze and compare the changes in visual function under mesopic and photopic conditions in different stages of keratoconus before and after Keraring intrastromal corneal ring segment (ICRS) implantation. Setting Clinico San Carlos Hospital and Faculty of Optics and Optometry, Complutense University, Madrid, Spain. Design Case series. Methods Keratoconic eyes were evaluated under mesopic (0.1 to 0.2 candelas [cd]/m2) and photopic (85 cd/m2) conditions. LogMAR high‐contrast corrected distance visual acuity (CDVA) and low‐contrast CDVA were assessed using the Bailey‐Lovie test and logarithmic contrast sensitivity, using the Pelli‐Robson test. Results The study evaluated 12 eyes with stage I keratoconus, 21 eyes with stage 2, and 14 eyes with stage 3. The mean change in photopic high‐contrast CDVA was 0.16 logMAR ± 0.20 (SD) (P<.00001). Photopic low‐contrast CDVA increased by a mean of 0.14 ± 0.26 logMAR (P=.0005), photopic contrast sensitivity by a mean of 0.09 ± 0.22 logMAR (P=.005), and mesopic high‐contrast CDVA by a mean of 0.10 ± 0.26 logMAR (P=.03). There were no significant differences between stages. Surgery did not affect the mean changes in mesopic low‐contrast CDVA or mesopic contrast sensitivity for any stage. Conclusions Implantation of ICRS in keratoconic eyes increased photopic high‐contrast CDVA, low‐contrast CDVA, and contrast sensitivity. Under low luminance, the mean changes in high‐contrast CDVA, low‐contrast CDVA, and contrast sensitivity did not worsen after ICRS implantation performed 5.0 mm from the visual axis, despite the rings being partially superimposed on the mydriatic pupil. Financial Disclosure No author has a financial or proprietary interest in any material or method mentioned.

Disk halo size measured in individuals with monofocal versus diffractive multifocal intraocular lenses.

Purpose To compare disk halo size in response to a glare source in eyes with an aspheric apodized diffractive multifocal intraocular lens (IOL) or aspheric monofocal IOL. Setting Rementeria Ophthalmological Clinic, Madrid, Spain. Design Prospective randomized masked study. Method Halo radius was measured using a vision monitor (MonCv3) with low‐luminance optotypes in eyes that had cataract surgery and bilateral implantion of an Acrysof Restor SN6AD1 multifocal IOL or Acrysof IQ monofocal IOL 6 to 9 months previously. The visual angle subtended by the disk halo radius was calculated in minutes of arc (arcmin). Patient complaints of halo disturbances were recorded. Monocular uncorrected distance visual acutity (UDVA) and corrected distance visual acuity (CDVA) were measured using high‐contrast (96%) and low‐contrast (10%) logMAR letter charts. Results The study comprised 39 eyes of 39 subjects (aged 70 to 80 years); 21 eyes had a multifocal IOL and 18 eyes a monofocal IOL. The mean halo radius was 35 arcmin larger in the multifocal IOL group than the monofocal group (P < .05). Greater halo effects were reported in the multifocal IOL group (P < .05). The mean monocular high‐contrast UDVA and low‐contrast UDVA did not vary significantly between groups, whereas the mean monocular high‐contrast CDVA and low‐contrast CDVA were significantly worse at 0.12 logMAR and 0.13 logMAR in the multifocal than in the monofocal IOL group, respectively (P < .01). A significant positive correlation was detected by multiple linear regression between the halo radius and low‐contrast UDVA in the multifocal IOL group (r = 0.72, P < .001). Conclusions The diffractive multifocal IOL gave rise to a larger disk halo size, which was correlated with a worse low‐contrast UDVA. Financial Disclosure None of the authors has a financial or proprietary interest in any material or method mentioned.