Relationships Between Night Myopia And Black Hole Illusion In Pilots

Black hole illusion（black hole illusion,BHI）is a high incidence of optical illusion（optical illusion,OI）,which often occurs in the environment of poor visibility or lack of terrain features,especially in the process of approach,it is easy to induce pilots to enter the low glide path.Despite the severity of the problem,BHI is poorly understood from a theoretical perspective.Little empirical evidence exists to support a definitive cognitive or perceptual cause and an effective training method.Previous studies have mostly proposed hypotheses related to pilots’misjudgment of altitude and distance in a terrain-feature environment from a psychological perspective,and research methods have mostly been used flight simulators to construct approach black hole scene.Night myopia is a visual physiological phenomenon that occurs easily under empty visual field conditions,and the conditions under which it occurs are similar to those under which BHI occurs.Prior studies in our laboratory have found that night myopia may be an important cause of BHI.This study verifies the relationship between night myopia and BHI and the effect of BHI on distance judgment in terms of questionnaire surveys,flight accident cases analysis and human experiments.To study and establish a visual training method to overcome BHI,which is of great significance in aviation medicine to ensure flight safety.Purpose1.To further explore the role of visual factors through typical flight accident cases.2.To understand the visual characteristics of night visual approach and its influence on flight safety through military investigation.3.To explore the influence of runway light brightness on distance perception during BHI and its relationship with night myopia.4.To study the effect on approach distance judgment at night after overcoming night myopia.5.To explore the causes of underestimation of aim point and its relationship with BHI phenomenon6.To develop a visual training device to overcome BHI and establish training methods.Materials and Methods1.Analysing the visual factors of typical BHI accidents and questionnaire to investigate the visual phenomena during night approach.In the BHI-related Controlled Flight Into Terrain（CFIT）accidents,poor visibility,high decline rate,underestimation of runway distance,and loss of runway visual reference were selected as the characteristic accidents.National Transportation Safety Board（NTSB）and the flight accident reports,to sort out the visual clues of the accidents,summarize the characteristics of BHI accidents,the role of visual factors,and draw lessons from them.Through interviews with pilots of various types of aircraft to understand the current situation of pilots’awareness of the BHI phenomenon,a questionnaire was developed based on the feedback from the interviews and the visual clues and characteristics of the BHI occurrence to understand the role of visual factors in the visual approach process at night in low visibility conditions and their impact on flight safety.2.Verifying the relationship between night myopia and BHI.Establishing the BHI ground simulation experience method:A simulation environment of BHI occurrence was established in a standard dark room,and the perception task of runway light position during approach was constructed through visual target motion,and the subjects’perception of motion position was observed according to their judgment of motion distance of visual targets with different luminance,in order to explore the effect of runway light luminance on motion distance when BHI occurs and its relationship with night myopia.During the test,the“ear-hand transponder”was used to test the response time to interfere with the subject’s attention allocation and monitor the changes of relevant physiological indicators（eye movements and EEG）.On this basis,the conditions for disrupting the formation of the empty visual field were established to observe the effect on the judgment of the distance to the motion visual target after overcoming the state of night myopia.3.Exploring the effect of depression angle on distance judgment.According to the final stage of approach pilots are to observe the aim point（runway lights）at a certain depression angle as an important reference basis for distance judgment,a height-variable intelligent mobile platform was developed to form different gaze angles（0°,-5°,-10°）between the height of the light visual target and the observer’s eye level,and to test the subject’s difference in distance discrimination（50cm between visual target distances）in the dark room channel.In addition,a shimmering integrating sphere was used to simulate a full moon shimmering environment,and a visual environment with a reference object was established by setting up a reference object.The difference in distance discrimination in the visual environment with a reference was measured at a gaze angle（-5°）.Subjects completed the visual task under the interference load of"ear-hand manipulation"and the response time was recorded.4.Verifying the influence of the change of the angle between the edges of the simulated runway on the judgment of dynamic distance.A BHI simulation experience device was established to simulate the change of runway sidelight angle from 0°to the test angle（0°,10°,20°,30°,40°）during the aircraft approach,and to observe the subjects’judgment of the distance difference between the runway light（aim point）and the reference light during the simulated approach in the dark room environment,and the effect of the change of sidelight angle on the distance judgment.5.Developing a training device to against night myopia and BHIBased on the phenomenon that the effect of BHI on distance judgment can be overcome after destroying night myopia,we developed a training device to alleviate night myopia and BHI.Results1.BHI-related CFIT accident performance.The analysis of typical accidents can be concluded that the following visual factors are closely related to the occurrence of accidents.（1）Poor visibility will affect the clarity of runway lights.If there is no light condition to stimulate the empty visual field,it is prone to night myopia.（2）The visual environment without feature terrain is prone to excessive decline rate and distance underestimation.（3）The low descent path in the early stage of approach is related to the loss of runway vision caused by night myopia.（4）Underestimation of runway distance is an important cause of BHI-type accidents.2.Results of the questionnaire.The results of the questionnaire showed that more than 10%of pilots relied on visual approach for landing in visual conditions with poor visibility.The most common strategy used by pilots for visual approaches in this environment was to use runway lights to estimate the distance to the landing point（73%）.The most common types of night approach misjudgments were"low for high"（35%）and"far for near"（42%）.Most pilots（85%）were concerned about the increasing angle of the sidelight as they approached the runway.3.The effect of visual target luminance on perceived motion distance.Under completely dark room conditions,the difference between the subjects’perceived visual target motion distance and the actual value increased significantly when the motion visual target luminance was 1×10^-4cd/m²,and the distance difference was significantly different from both the visual target luminance of 1×10^-2cd/m²and 1×10^-3cd/m² groups（P<0.001）.When the visual target luminance was 1×10^-4cd/m²,the perceived distance difference decreased significantly（P<0.001）after increasing the red and green light source stimuli to break the empty visual field.Behavioral observations revealed that the subjects could not easily find the target during low luminance(1×10^-4cd/m²)visual target movements,and the eye movement monitoring indexes showed that the longitudinal（Z-axis）direction value of the gaze point scene（490.65±28.89mm）was smaller（P<0.01）in the 0-5s time period from the beginning of the gaze movement visual marker compared to the other luminance groups,and the pupil diameter（6.90±0.03mm）was also relatively small compared to the other luminance groups（P<0.01）.After destruction of the empty visual field,the subjects’gaze point Z values were larger in the 0-5s（619.76±61.31mm）and 5-10s（565.51±67.93mm）time periods than in the no-light stimulation group（P<0.05）,and pupil diameter was larger in the 0-5s time period（7.01±0.03mm）than in the no-light stimulation group（P<0.05）.Ear-hand response time:the 1×10^-4cd/m² group was slower than the 1×10-3cd/m² group（P<0.05）.4.Effect of depression angle on distance judgment.In the no-reference environment,the three gaze angle groups（0°,-5°,-10°）showed significant variability（P<0.001）in the difference in distance assessment,with the following trend in the degree of underestimation of distance:depression angle 10°>depression angle 5°>horizontal angle 0°.At the gaze angle of-5°,the reference group underestimated the distance values less than the no-reference group（P<0.001）.Ear-hand response time:the reference group was faster than the no-reference group（P<0.05）.5.Effect of sidelight angle on distance evaluation.In the darkroom environment,there was a significant difference（P<0.01）in the variation of the runway sidelight angle（sidelight angle variation 0°,10°,20°,30°,40°）on the distance judgment difference,and the greater the angle variation,the greater the error in distance judgment for each group,where the comparison between the groups:between 0°and 20°angle,between 0°and 30°angle,between 0°and 40°,between 10°and 40°between 0°and 20°angle,between 0°and 30°angle,between 0°and 0°,between 10°and40°,and between 20°and 40°were different（P<0.05）.6.Initial establishment of counteracting BHIBased on the fact that the method of using red and green light source stimulation can effectively improve night myopia,it is proposed that pilots observing the red and green lights on the left and right wingtips to break the void field of view state can overcome the BHI phenomenon caused by low brightness runways.Currently,the method has been verified by the visual experience of the approach process of three pilots under the condition of poor visibility.A BHI simulation experience device was developed based on the retinal image of the runway edge light in the air perspective during the approach.The device verified the underestimation of the reference light by simulating the angle change of the sideline light in the darkroom environment through 10 subjects.Conclusions1.Runway lights are the key visual cue for low visibility approach.Pilots tend to use runway lights to estimate the distance to the aim point during visual approach,and are prone to"mistaking low for high"and"mistaking far for near"in poor visibility or lack of visual reference,which is an important cause of similar accidents in BHI.2.In the dark room simulated BHI environment,it not only affects the subjects’discovery of the low luminance light visual target and the judgment of the visual target distance,but also the estimated distance is higher than the actual distance,which is consistent with the visual phenomenon felt in the flight under the condition of empty visual field.When the condition of empty visual field is destroyed,the ability of visual performance is significantly improved,and the parameters of eye movement are significantly improved,indicating that the near shift of far point and the change of diopter may be the main reasons for the decline of visual performance in night myopia.3.The observation of runway lights at different depression angles and the influence of the change in the angle of the sidelight during the flight will approximate the distance of the aim point,which can further explain the occurrence of BHI under the visual cues of closer to the runway or clear runway lights.4.The method of observing the wing traffic lights can improve the night myopic state,effectively regulate the phenomenon of blurred distance vision,improve the ability to discriminate runway position,and overcome the occurrence of BHI during approach under low visibility conditions.The BHI simulation experience device allows pilots to experience the phenomenon of distance underestimation caused by the change in the angle of the simulated runway sidelight after the night myopic state is improved,which helps pilots realize the illusion of visual distance during approaching and develop a sense of safety that firmly believes in the instrument.