Vision, attention, and driving.

Safe driving demands the coordination of multiple sensory and cognitive functions, such as vision and attention. Patients with neurologic or ophthalmic disease are exposed to selective pathophysiologic insults to driving-critical systems, placing them at a higher risk for unsafe driving and restricted driving privileges. Here, we evaluate how vision and attention contribute to unsafe driving across different patient populations. In ophthalmic disease, we focus on macular degeneration, glaucoma, diabetic retinopathy, and cataract; in neurologic disease, we focus on Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Unsafe driving is generally associated with impaired vision and attention in ophthalmic and neurologic patients, respectively. Furthermore, patients with ophthalmic disease experience some degree of impairment in attention. Similarly, patients with neurologic disease experience some degree of impairment in vision. While numerous studies have demonstrated a relationship between impaired vision and unsafe driving in neurologic disease, there remains a dearth of knowledge regarding the relationship between impaired attention and unsafe driving in ophthalmic disease. In summary, this chapter confirms-and offers opportunities for future research into-the contribution of vision and attention to safe driving.

Glaucomatous visual fields and neurocognitive function are independently associated with poor lane maintenance during driving simulation.

BACKGROUND: Driving simulators are a safe alternative to on-road vehicles for studying driving behavior in glaucoma drivers. Visual field (VF) loss severity is associated with higher driving simulator crash risk, though mechanisms explaining this relationship remain unknown. Furthermore, associations between driving behavior and neurocognitive performance in glaucoma are unexplored. Here, we evaluated the hypothesis that VF loss severity and neurocognitive performance interact to influence simulated vehicle control in glaucoma drivers. METHODS: Glaucoma patients (n = 25) and suspects (n = 18) were recruited into the study. All had > 20/40 corrected visual acuity in each eye and were experienced field takers with at least three stable (reliability > 20%) fields over the last 2 years. Diagnosis of neurological disorder or cognitive impairment were exclusion criteria. Binocular VFs were derived from monocular Humphrey VFs to estimate a binocular VF index (OU-VFI). Montreal Cognitive Assessment (MoCA) was administered to assess global and sub-domain neurocognitive performance. National Eye Institute Visual Function Questionnaire (NEI-VFQ) was administered to assess peripheral vision and driving difficulties sub-scores. Driving performance was evaluated using a driving simulator with a 290° panoramic field of view constructed around a full-sized automotive cab. Vehicle control metrics, such as lateral acceleration variability and steering wheel variability, were calculated from vehicle sensor data while patients drove on a straight two-lane rural road. Linear mixed models were constructed to evaluate associations between driving performance and clinical characteristics. RESULTS: Patients were 9.5 years older than suspects (p = 0.015). OU-VFI in the glaucoma group ranged from 24 to 98% (85.6 ± 18.3; M ± SD). OU-VFI (p = .0066) was associated with MoCA total (p = .0066) and visuo-spatial and executive function sub-domain scores (p = .012). During driving simulation, patients showed greater steering wheel variability (p = 0.0001) and lateral acceleration variability (p < .0001) relative to suspects. Greater steering wheel variability was independently associated with OU-VFI (p = .0069), MoCA total scores (p = 0.028), and VFQ driving sub-scores (p = 0.0087), but not age (p = 0.61). CONCLUSIONS: Poor vehicle control was independently associated with greater VF loss and worse neurocognitive performance, suggesting both factors contribute to information processing models of driving performance in glaucoma. Future research must demonstrate the external validity of current findings to on-road performance in glaucoma.

Effect of Near Work on Intraocular Pressure in Emmetropes.

OBJECTIVE: To determine whether accommodation induced by reading alters intraocular pressure (IOP) in healthy, young, emmetropic adults and to document the duration and magnitude of this effect. DESIGN: Cross-sectional study. Participants. Fifteen healthy, emmetropic young adults. METHODS: Subjects performed 20 minutes of near work (reading at 33 cm) followed by 20 minutes of far work (reading at 520 cm) while IOP was measured using an iCare tonometer at baseline and every 5 minutes thereafter. Statistical analysis was performed using repeated measures ANOVA. Main Outcome Measures. Intraocular pressure. RESULTS: IOP decreased significantly compared to baseline IOP after 10 minutes of near work (average change of -1.60 ± 2.2 (SD) mm Hg, p < 0.05). IOP remained lower than baseline IOP throughout all subsequent near and far work. The difference in IOP at the end of experimentation compared to baseline IOP was -1.87 ± 1.81 mm Hg (p < 0.05). IOP remained lower than baseline IOP throughout all subsequent near and far work. The difference in IOP at the end of experimentation compared to baseline IOP was -1.87 ± 1.81 mm Hg (. CONCLUSIONS: Near work decreases IOP in healthy emmetropes, and this effect is sustained for at least 20 minutes after discontinuing prolonged near work. Providers may need to consider this effect when measuring IOP in clinical practice.

Pneumotonometer Accuracy Using Manometric Measurements after Radial Keratotomy, Clear Corneal Incisions and Lamellar Dissection in Porcine Eyes.

Purpose/Aim of the study: Measured intraocular pressure (IOP) after corneal incisions may not be reflective of the true IOP because of changes in corneal biomechanical properties. The purpose of this study is to investigate the effect of various corneal incisions on pneumotonometer accuracy in enucleated porcine eyes.Materials and Methods: A pneumotonometer was used to measure IOP (IOPp) at manometrically controlled pressure levels of 10, 20, 30 and 40 mmHg in enucleated porcine eyes. IOP measurements at each level were repeated after one of the following corneal incisions: radial keratotomy (8 eyes), lamellar dissection (10 eyes), clear cornea standard phacoemulsification incisions (10 eyes). The pneumotonometer error, defined as the difference between IOPp and manometric pressure (IOPm), was calculated for each pressure level. The error before the corneal incisions was compared to the error after the corneal incisions to assess the accuracy of the pneumotonometer.Results: The pneumotonometer underestimates true IOP at all pressure levels, both before and after the corneal procedures. There was a statistically significant greater underestimation of IOP after radial keratotomy incisions at pressure levels of 20, 30 and 40 mmHg (p = .013, 0.004, and 0.002, respectively). There was no statistically significant difference in the amount of pneumotonometer underestimation error after lamellar dissection or standard cataract incisions.Conclusion: The pneumotonometer underestimates true IOP in enucleated porcine eyes at all pressure levels between 10-40 mmHg. Radial keratotomy incisions caused a statistically significant greater underestimation error in pneumotonometry measurements at pressures of 20-40 mmHg. Lamellar dissection and clear corneal cataract incisions did not cause an additional error in pneumotonometry measurements in enucleated porcine eyes.

Factors affecting wound leakage in 23-gauge sutureless pars plana vitrectomy.

PURPOSE: To evaluate risk factors for sclerotomy leakage in 23-gauge sutureless pars plana vitrectomy in 219 patients. METHODS: Nested case-control study involving 48 patients with wound leaks (visible on-table sclerotomy leakage requiring sutures) and 171 control subjects without wound leaks. Patients received either a conventional sclerotomy incision at 45°, which was then changed to 90° midincision, or an extremely oblique sclerotomy incision (OSI) at 10°, which was then changed to 30° midincision. Risk factors studied included age, gender, laterality, surgical duration, sclerotomy incision (OSI vs. conventional sclerotomy incision), preoperative diagnosis (macular vs. nonmacular), history of vitrectomy, and primary surgeon (attending vs. supervised resident). RESULTS: Multivariate logistic regression analysis found significant (P ≤ 0.05) protective factors for wound leakage including OSI, macular preoperative diagnosis, no previous vitrectomy, and female gender. Surgical duration at least 45 minutes was considered a borderline risk factor. CONCLUSION: Using an extremely OSI versus a conventional sclerotomy incision reduces the incidence of wound leakage postoperatively because of its self-sealing effect. Other factors that contribute to wound leakage, such as increased surgical duration and nonmacular diagnosis, may be indirect measurements of extensive trocar rotation, causing wound leakage despite the use of an OSI.

Correlations between parameters of aqueous humor dynamics and the influence of central corneal thickness.

PURPOSE: The individual parameters of aqueous humor dynamics may influence each other to maintain intraocular pressure (IOP) homeostasis. Central corneal thickness (CCT) is known to be associated with onset and progression of glaucoma and can potentially influence the individual parameters of aqueous humor dynamics that maintain IOP. This study investigates the correlation between parameters of aqueous humor dynamics and the influence of CCT in healthy volunteers and compares it with the correlations seen in patients with ocular hypertension. METHODS: Aqueous humor dynamics (aqueous flow, outflow facility, and uveoscleral outflow), IOP, and pachymetry data from 94 healthy ocular normotensive (ONT) volunteers and 63 ocular hypertensive (OHT) patients was analyzed retrospectively. Linear correlations between individual aqueous humor dynamics parameters and pachymetry were evaluated using scatter plots and the Spearman correlation coefficient where appropriate. RESULTS: In both groups, a significant (P < 0.05) negative correlation was found between corneal thickness and aqueous flow (ONT, R(2) = 0.14; OHT, R(2) = 0.10) and between corneal thickness and uveoscleral outflow (ONT and OHT, R(2) = 0.10). A significant (P < 0.05) positive correlation was found between aqueous flow and outflow facility (ONT, R (2) = 0.24; OHT, R(2) = 0.10). In healthy controls, but not OHT patients, a significant (P < 0.001) positive correlation was found between aqueous flow and uveoscleral outflow (R(2) = 0.15). CONCLUSIONS: Thicker corneas may be associated with lower aqueous production and lower uveoscleral outflow. The interplay between parameters of aqueous humor dynamics suggests possible autoregulatory mechanisms in the eye. OHT may differ from ONT subjects in their inability to increase the uveoscleral outflow with increases in aqueous inflow.

Evaluation of endothelial mucin layer thickness after phacoemulsification with next generation ophthalmic irrigating solution.

PURPOSE: To evaluate human corneal endothelial mucin layer thickness and ultrastructure after phacoemulsification and irrigation-aspiration with either next generation ophthalmic irrigating solution (NGOIS) or BSS PLUS. METHODS: Paired human corneas were mounted in an artificial anterior chamber, exposed to 3 minutes of continuous ultrasound (US) at 80% power using the Alcon SERIES 20000 LEGACY surgical system (n = 9) or to 2 minutes of pulsed US at 50% power, 50% of the time at 20 pps using the Alcon INFINITI Vision System (n = 5), and irrigated with 250 mL of either NGOIS or BSS PLUS. A control group of paired corneas did not undergo phacoemulsification or irrigation-aspiration (n = 5). Corneas were divided and fixed for mucin staining or transmission electron microscopy. Mucin layer thickness was measured on the transmission electron microscopy prints. RESULTS: The mucin layer thickness in the continuous phaco group was 0.77 +/- 0.02 microm (mean +/- SE) with NGOIS and 0.51 +/- 0.01 microm with BSS PLUS (t test, P < 0.001). The mucin layer thickness in the pulsed phaco group was 0.79 +/- 0.02 microm with NGOIS and 0.54 +/- 0.01 microm with BSS PLUS (P < 0.001). The mucin layer thickness in the untreated control group was 0.72 +/- 0.02 microm. The endothelial ultrastructure was normal in all corneas. CONCLUSIONS: In this in vitro corneal model, NGOIS, due to its lower surface tension and higher viscosity, preserved endothelial mucin layer thickness better than BSS PLUS with both the INFINITI Vision System (pulsed US) and the LEGACY surgical system (continuous US).