An objective evaluation of simulated surgical outcomes among surgical trainees using manual small-incision cataract surgery virtual reality simulator

Purpose:The purpose of this study was to evaluate trainee performance across six modules of a virtual reality (VR) simulator.Methods:A retrospective observational study was conducted on 10 manual small-incision cataract surgery (MSICS) trainees who practiced cataract surgery on an MSICS VR simulator for one month. They were assessed in six major steps which included scleral groove, tunnel dissection, keratome entry, capsulorhexis, nucleus delivery, and intraocular lens (IOL) insertion under a trainer’s supervision. The information included in their score metrics was collected, and their overall performance was evaluated.Results:Thirty attempts were evaluated for scleral groove, tunnel dissection, and capsulorhexis and 15 attempts for keratome entry. Candidates had varied results in the dimensional aspects and their rates of complications with a mean satisfactory score of 3.1 ± 4.17, 6.8 ± 5.75, 5.8 ± 7.74, and 1.8 ± 2.57, respectively. Nucleus delivery (n = 5) had more of iris pull and IOL insertion (n = 5) had more of lost IOL as complications but both had a higher satisfactory outcome.Conclusion:A VR simulator is a useful tool for training surgeons before their entry into live surgery. It is an effective method for evaluating objectively the structural characteristics of each phase in MSICS and their associated complications, helping them anticipate it earlier during live surgery by giving them a near real world experience.     

Virtual reality simulator for vitreoretinal surgery

AIM: To develop computer simulation of steps in vitreoretinal surgery using virtual reality technology. MATERIAL AND METHODS: A workstation with three-dimensional position tracking stylus was attached to a Pentium II desktop PC with a graphic accelerator. Computer algorithms were developed using Open GL and Microsoft Visual C++ languages to control the interaction and update the visual feedback tracking the instruments. Soft tissue computer modelling was carried out to mimic the removal of a vitreous opacity. Lens touch with the instruments was also detected. Mathematical modelling to allow for lens distortion was taken into account. RESULTS: A virtual reality computer model has been developed that can simulate initial steps of vitreoretinal surgery. Soft tissue modelling of the vitreous opacity and its removal by the vitrector was successfully simulated. The movements of the active and passive instruments in the dummy eye corresponded to the movements on the computer screen. On evaluation of the system, there was a minimal but discernable time lag between the stylus movement and the visual feedback. There was no tactile feedback when the lens touch was simulated. No further complex vitreoretinal surgery simulation was possible at this stage.     

Development of a virtual reality training curriculum for phacoemulsification surgery

Purpose

Training within a proficiency-based virtual reality (VR) curriculum may reduce errors during real surgical procedures. This study used a scientific methodology to develop a VR training curriculum for phacoemulsification surgery (PS).

Patients and methods

Ten novice-(n) (performed <10 cataract operations), 10 intermediate-(i) (50–200), and 10 experienced-(e) (>500) surgeons were recruited. Construct validity was defined as the ability to differentiate between the three levels of experience, based on the simulator-derived metrics for two abstract modules (four tasks) and three procedural modules (five tasks) on a high-fidelity VR simulator. Proficiency measures were based on the performance of experienced surgeons.

Results

Abstract modules demonstrated a ‘ceiling effect'' with construct validity established between groups (n) and (i) but not between groups (i) and (e)—Forceps 1 (46, 87, and 95; P<0.001). Increasing difficulty of task showed significantly reduced performance in (n) but minimal difference for (i) and (e)—Anti-tremor 4 (0, 51, and 59; P<0.001), Forceps 4 (11, 73, and 94; P<0.001). Procedural modules were found to be construct valid between groups (n) and (i) and between groups (i) and (e)—Lens-cracking (0, 22, and 51; P<0.05) and Phaco-quadrants (16, 53, and 87; P<0.05). This was also the case with Capsulorhexis (0, 19, and 63; P<0.05) with the performance decreasing in the (n) and (i) group but improving in the (e) group (0, 55, and 73; P<0.05) and (0, 48, and 76; P<0.05) as task difficulty increased.

Conclusion

Experienced/intermediate benchmark skill levels are defined allowing the development of a proficiency-based VR training curriculum for PS for novices using a structured scientific methodology.     

Assessment of a high-fidelity,virtual reality-based,manual small-incision cataract surgery simulator: A face and content validity study

Purpose:To establish the face and content validity of the HelpMeSee Eye Surgery Simulator – a virtual reality-based cataract surgery simulator for manual small-incision cataract surgery (MSICS).Methods:The face and content validity were assessed on the sclero-corneal tunnel construction course. A questionnaire with 11 questions focused on the visual realism, with resemblance to real life surgery, and the training value of the simulator was developed. Thirty-five experienced MSICS surgeons participated in the study. Responses were recorded using a seven-point scoring system.Results:Overall, 74.3% (26/35) of the respondents agreed that the overall visual representation of the eye and the instruments in the simulator were realistic. The task of injecting a visco-elastic through the paracentesis was reported to be the most visually realistic task with a mean score of 5.78 (SD: 1.09; range: 2–7). With regard to content validity, 77.1% (27/35) of the subjects felt agreed that the errors and complications represented throughout the entire tunnel construction module were similar to those encountered in real life; the task of entering the anterior chamber with the keratome had a mean score of 5.54 (SD: 0.98; range 1–7), being rated the highest in that aspect. Overall, 94.3% (33/35) of the subjects agreed that the simulator would be useful in developing hand–eye co-ordination. A similar number of 94.3% (33/35) agreed that based on their experience, they would recommend cataract surgical training on this simulator.Conclusion:The results suggest that the HelpMeSee Eye Surgery Simulator appears to have sufficient face and content validity for cataract surgical training.     

Block-building performance test using a virtual reality head-mounted display in children with intermittent exotropia

PurposeTo determine whether childhood intermittent exotropia (IXT) affects distance divergence and performance in block-building tasks within a virtual reality (VR) environment.MethodsThirty-nine children with IXT, aged 6–12 years, who underwent muscle surgery and 37 normal controls were enrolled. Children were instructed to watch the target moving away and perform a block-building task while fitted with a VR head-mounted display equipped with eye- and hand-movement tracking systems. The change in inter-ocular distance with binocular distance viewing, time to stack five cube blocks of different sizes in order, and distance disparities between the largest and farthest cubes were assessed. All children were evaluated at baseline and 3-month time points.ResultsThe patients with IXT exhibited a larger distance divergence than did controls (p = 0.024), which was associated with greater distance angle of deviation and poorer distance control (r = 0.350, p = 0.001 and r = 0.349, p = 0.004). At baseline, the patients with IXT showed larger distance disparities in the block-building task than did controls in terms of the horizontal, vertical, and 3-dimensional (3-D) measurements (all ps < 0.050). Larger horizontal disparity was associated with greater distance angle of deviation (r = 0.383, p = 0.037). Three months after surgery, the horizontal and 3-D disparities in the patients with IXT improved significantly and were not comparably different compared with controls.ConclusionsThese preliminary findings suggest that VR-based block-building task may be useful in testing possible deficits in visuo-motor skills associated with childhood IXT.Subject terms: Eye manifestations, Outcomes research     

Systematic distortions of perceptual stability investigated using immersive virtual reality

Using an immersive virtual reality system, we measured the ability of observers to detect the rotation of an object when its movement was yoked to the observer's own translation. Most subjects had a large bias such that a static object appeared to rotate away from them as they moved. Thresholds for detecting target rotation were similar to those for an equivalent speed discrimination task carried out by static observers, suggesting that visual discrimination is the predominant limiting factor in detecting target rotation. Adding a stable visual reference frame almost eliminated the bias. Varying the viewing distance of the target had little effect, consistent with observers underestimating distance walked. However, accuracy of walking to a briefly presented visual target was high and not consistent with an underestimation of distance walked. We discuss implications for theories of a task-independent representation of visual space.     

Cataract surgeons outperform medical students in Eyesi virtual reality cataract surgery: evidence for construct validity

Purpose: To investigate construct validity for modules hydromaneuvers and phaco on the Eyesi surgical simulator. Methods: Seven cataract surgeons and 17 medical students performed capsulorhexis, hydromaneuvers, phaco, navigation, forceps, cracking and chopping modules in a standardized manner. Three trials were performed on each module (two on phaco) in the above order. Performance parameters as calculated by the simulator for each trial were saved. Video recordings of the second trial of the modules capsulorhexis, hydromaneuvers and phaco were evaluated with the modified Objective Structured Assessment of Surgical Skill (OSATS) and Objective Structured Assessment of Cataract Surgical Skill (OSACSS) tools. Results: Cataract surgeons outperformed medical students with regard to overall score on capsulorhexis (p < 0.001, p = 0.035, p = 0.010 for the tree iterations, respectively), navigation (p = 0.024, p = 0.307, p = 0.007), forceps (p = 0.017, p = 0.03, p = 0.028). Less obvious differences in overall score were found for modules cracking and chopping (p = 0.266, p = 0.022, p = 0.324) and phaco (p = 0.011, p = 0.081 for the two iterations, respectively). No differences in overall score were found on hydromaneuvers (p = 0.588, p = 0.503, p = 0.773), but surgeons received better scores from the evaluations of the modified OSATS (p = 0.001) and OSACSS (capsulorhexis, p = 0.003; hydromaneuvers, p = 0.017; phaco, p = 0.001). Conclusions: Construct validity was found on several modules previously not investigated (phaco, hydromaneuvers, cracking and chopping, navigation), and our results confirm previously demonstrated construct validity for capsulorhexis and forceps modules. Interestingly, validation of the hydromaneuvers module required OSACSS video evaluation tool. A further development of the scoring system in the simulator for the hydromaneuvers module would be advantageous and make training and evaluation of progress more accessible and immediate.     

人工晶状体置换术的临床分析

目的　探讨临床行人工晶状体置换术的原因、手术方法和效果。方法　回顾性分析7例(8眼)人工晶状体置换术的原因,总结手术方法,对手术效果进行观察。结果　人工晶状体置换术的原因包括人工晶状体浑浊5例(6眼) ,人工晶状体屈光度数错误2例(2眼)。手术方法为人工晶状体取出和另一枚人工晶状体囊袋内植入。术后最佳矫正视力≥0 . 5者7眼(87. 5 0 % ) ,0 . 2 5者1眼(12 . 5 0 % )。术后并发症为散光2眼。结论　人工晶状体浑浊和屈光度数错误是人工晶状体置换术的原因,人工晶状体置换术是解决人工晶状体异常的有效方法。     

人工晶状体置换术的临床分析

目的 探讨临床行人工晶状体置换术的原因、手术方法和效果。方法 回顾性分析20例（21眼）人工晶状体置换术的原因和手术方法，并对手术效果进行观察。结果 行人工晶状体置换术的原因为人工晶状体位置异常10例10眼（47．6％），人工晶状体瞳孔夹持6例7眼（33．3％），屈光度数误差2例21眼（9．5％），人工晶状体襻脱落2例2眼（9．5％）。手术置换人工晶状体的方法包括晶状体囊袋内植入5眼（23．8％），睫状沟固定6眼（28．6％），植入前房型人工晶状体10眼（47．6％）。术后裸眼远视力≥0．5者12眼（57．1％），0．1～0．4者8眼（38．1％），〈0．1者1眼（4．8％）。术后并发症包括术后一过性高眼压1例，前房出血1例，晶状体后囊膜混浊1例。结论 人工晶状体位置异常、瞳孔夹持、屈光度数误差及人工晶状体襻异常是行人工晶状体置换术的主要原因；掌握操作技巧可减少白内障摘除人工晶状体植入术后人工晶状体异常情况发生；人工晶状体置换术是处理人工晶状体异常的有效方法。     

The development of a symptom questionnaire for assessing virtual reality viewing using a head-mounted display.

PURPOSE: Virtual reality devices, including virtual reality head-mounted displays, are becoming increasingly accessible to the general public as technological advances lead to reduced costs. However, there are numerous reports that adverse effects such as ocular discomfort and headache are associated with these devices. To investigate these adverse effects, questionnaires that have been specifically designed for other purposes such as investigating motion sickness have often been used. The primary purpose of this study was to develop a standard questionnaire for use in investigating symptoms that result from virtual reality viewing. In addition, symptom duration and whether priming subjects elevates symptom ratings were also investigated. METHODS: A list of the most frequently reported symptoms following virtual reality viewing was determined from previously published studies and used as the basis for a pilot questionnaire. The pilot questionnaire, which consisted of 12 nonocular and 11 ocular symptoms, was administered to two groups of eight subjects. One group was primed by having them complete the questionnaire before immersion; the other group completed the questionnaire postviewing only. Postviewing testing was carried out immediately after viewing and then at 2-min intervals for a further 10 min. RESULTS: Priming subjects did not elevate symptom ratings; therefore, the data were pooled and 16 symptoms were found to increase significantly. The majority of symptoms dissipated rapidly, within 6 min after viewing. Frequency of endorsement data showed that approximately half of the symptoms on the pilot questionnaire could be discarded because <20% of subjects experienced them. CONCLUSIONS: Symptom questionnaires to investigate virtual reality viewing can be administered before viewing, without biasing the findings, allowing calculation of the amount of change from pre- to postviewing. However, symptoms dissipate rapidly and assessment of symptoms needs to occur in the first 5 min postviewing. Thirteen symptom questions, eight nonocular and five ocular, were determined to be useful for a questionnaire specifically related to virtual reality viewing using a head-mounted display.     

Economic costs of cataract surgery using a rigid and a foldable intraocular lens.

Optimal delivery of healthcare requires consideration of various costs. A foldable intraocular lens (IOL) is more expensive than an equivalent rigid IOL. However, surgical and post-operative costs may make a foldable IOL economically preferable. We compared the economic costs of cataract surgery plus implantation of a foldable IOL with implantation of a rigid IOL. Prospective audit of the clinical records of 82 pseudophakes; 39 implanted with a rigid IOL and 43 implanted with a foldable IOL by one surgeon. Average follow-up periods were 25 +/- 7 months and 23 +/- 5 months respectively. There was no difference between the two groups for the follow-up period (P = 0.55), number of post-operative complications (P = 0.25) or cost of post-operative visits (P = 0.83). The cost of single-use theatre equipment was greater for the rigid-IOL group (P= 0.0001). The total identified cost per patient was greater for the foldable-IOL group (P = 0.0001). Despite possible technical advantages, implantation of the foldable IOL did not provide an economic benefit, either in the initial cost or in the costs of post-operative care. Over the 2-year period, implanting with the rigid IOL cost, on average, Pound Sterling57 less per patient. Despite this economic difference, a cost-benefit analysis is required, since other factors may be more important.     

Development of visually driven postural reactivity: a fully immersive virtual reality study

The objective of this study was to investigate the development of visually driven postural regulation in typically developing children of different ages. Thirty-two typically developing participants from 5 age groups (5-7 years, 8-11 years, 12-15 years, 16-19 years, or 20-25 years) were asked to stand within a virtual tunnel that oscillated in an anterior-posterior fashion at three different frequencies (0.125, 0.25, and 0.5 Hz). Body sway (BS) and postural perturbations (as measured by velocity root mean squared or vRMS) were measured. Most of the 5- to 7-year-old participants (67%) were unable to remain standing during the dynamic conditions. For older participants, BS decreased significantly with age for all frequencies. Moreover, vRMS decreased significantly from the 8- to 11- through 16- to 19-years age groups (greatest decreases for 0.5 Hz, followed by 0.25-Hz and 0.125-Hz conditions). No difference of frequency or instability was found between the 16- to 19- and 20- to 25-year-old groups for most conditions. Results suggest an over-reliance on visual input relative to proprioceptive and vestibular inputs on postural regulation at young ages (5-7 years). The finding that vRMS decreased significantly with age before stabilizing between 16 and 19 years suggests an important transitory period for sensorimotor development within this age range.     

Luminance calibration of virtual reality displays in Unity

Virtual reality (VR) displays are an increasingly popular medium for experiments on visual perception. This presents the challenge of showing precisely controlled stimuli on devices that were not primarily designed for research. Here we describe methods for controlling stimulus luminance in VR experiments created in Unity using the Built-in Render Pipeline. We discuss the Gamma/Linear setting, measuring luminance in a VR headset, and using color grading in Unity’s Post-Processing Stack to make stimulus luminance proportional to achromatic RGB value. We provide MATLAB code that uses luminance measurements from a VR headset to generate the lookup table that Unity requires for linearizing luminance. We emphasize that when creating experiments in this complex environment, it is important to experiment with the rendering process to confirm that stimuli are displayed as expected. We show results of several such tests and provide code as a starting point for readers who wish to run further tests related to their own research.     

内眼手术并发脉络膜上腔出血的临床分析

目的：探讨内眼手术术中和术后并发脉络膜上腔出血(suprachoroidal hemorrhage, SCH)的临床特点以及发生的危险因素,观察其视力预后。

方法：回顾性分析2005-06/2015-06共10a间本科收治的手术相关的SCH患者13例13眼,年龄22～76岁。13例13眼患者中,合并高度近视者6眼(46%),有高眼压病史者6眼(46%),合并高血压病者4眼(31%)。术中发生的驱逐性出血8眼,术后发生者迟发性出血5眼; 7眼为硅油取出术并发,4眼为白内障囊外取出术并发,1眼为小梁切除联合白内障囊外摘除术并发,1眼为晶状体脱位行晶状体切除联合玻璃体切除手术并发。5眼药物治疗,4眼行巩膜外放液引流联合玻璃体注气术,4眼行玻璃体切割联合重水和硅油注入。

结果：随访10mo,所有SCH全部吸收,最终视力除1眼放弃治疗无光感之外,其余12眼视力光感～0.4。

结论：内眼手术并发的SCH后果严重,高龄、高血压、高度近视和高眼压可能为其危险因素,手术切口导致术中眼压波动大可能与其发生有关,积极治疗后可以维持一定视力。