Peter Åsman

Virtual reality cataract surgery training: learning curves and concurrent validity

Purpose:  To investigate initial learning curves on a virtual reality (VR) eye surgery simulator and whether achieved skills are transferable between tasks.

Diffuse visual field loss and glaucoma

Abstract. It is often claimed that general reduction, or diffuse loss, of perimetric sensitivity is an early sign of glaucoma. Our clinical experience and the results of a few other studies led us to believe otherwise. To investigate factors associated with diffuse field loss we reviewed 4222 Humphrey 30–2 threshold tests from 1582 eyes of 862 patients followed at our department. Most of these patients had ocular hypertension or glaucoma. Each field test was evaluated with the Glaucoma Hemifield Test of the Statpac 2 program. The Glaucoma Hemifield Test classifies field test results as within or outside normal limits regarding localized field loss and general shifts in sensitivity. General reduction of sensitivity without concomitant localized loss was found in 117 tests from 81 eyes of 69 patients. Corresponding patient records were found for 60 eyes of 60 patients. Media opacities or miotic therapy were noted in 46 eyes (77%), 10 eyes (17%) had end‐stage field loss, and in 2 eyes (3%) other non‐glaucomatous ocular pathology explained the diffuse loss of sensitivity. Thus, general reduction of differential light sensitivity as an isolated finding was almost always associated with reasons other than early to moderate glaucoma in this material mainly consisting of patients with glaucoma or increased intraocular pressure. Since only 2 out of the 1582 eyes had general reduction of sensitivity that was not explained by non‐glaucomatous reasons, we conclude that purely diffuse field loss was not a sign of glaucoma.

Spatial analyses of glaucomatous visual fields; a comparison with traditional visual field indices

Abstract Interpretation of numeric automated threshold visual field results is often difficult. A large amount of data is obtained for every single field tested. Various approaches to summarize this data have been suggested, most commonly the mean and standard deviation of departures from age‐corrected normal threshold values. These visual field indices differ substantially from subjective field interpretation where spatial relationships are important. We have previously devised two methods for automated field interpretation which take spatial information into account ‐ regional up‐down comparisons and arcuate cluster analysis. We now studied the merits of using these new spatial methods and compared them to traditional visual field indices for discrimination between normal and glaucomatous field results. Central static 30° field results in 101 eyes of 101 normal subjects and 101 eyes of 101 patients with glaucoma were discriminated using logistic regression analysis. The best field classification was obtained with a spatial visual field model combining up‐down differences and arcuate clusters. The advantages of the spatial model were confirmed in an independent material of 163 eyes of 163 normal subjects and 76 eyes of 76 patients with glaucoma where eyes with large field defects had been removed. In this material the spatial model gave 87% sensitivity and 83% specificity while the best non‐spatial model gave 82% sensitivity and 80% specificity. Visual field interpretation in glaucoma may be significantly enhanced if detection is focused on circumscribed field loss rather than on averages of differential light sensitivities and similar indices which do not take spatial relationships into consideration.

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.

Internet-based assessment of medical students’ ophthalmoscopy skills

Acta Ophthalmol. 2010: 88: 854–857

Arcuate cluster analysis in glaucoma perimetry.

Typical glaucomatous visual field defects are often contiguous areas of diminished differential light sensitivity presenting as clusters of abnormally depressed points in the visual field chart. We investigated the value of recognizing arcuate cluster patterns, corresponding to the anatomy of the normal retinal nerve fiber layer. Cluster sizes were quantified using cluster volume and surface area. Clusters were analyzed separately in different regions of the visual field. Central 30 degrees static threshold fields from 87 eyes of 87 normal subjects and 101 eyes of 101 patients with glaucoma were studied. The two groups were discriminated with logistic regression. Central and nasal clusters were more indicative of glaucoma than were equally large clusters in other areas. Discrimination of normal and glaucoma eyes was significantly better with arcuate cluster analysis than with a traditional cluster analysis, which did not take cluster shape into account. Thus, arcuate cluster analysis was more sensitive to early central, paracentral, or nasal glaucomatous field loss and at the same time capable of deemphasizing common test artifacts and nondiagnostic field disturbances. Arcuate cluster volume gave better classification than did arcuate surface area. The results indicate that analysis of arcuate clusters offers substantial advantages as compared with traditional cluster analysis for recognition of early glaucomatous visual field loss.

Giant Cell Arteritis Presenting with Oculomotor Nerve Palsy

We present a case of histologically proven giant cell arteritis presenting as an acute unilateral oculomotor nerve palsy without pupillary dilatation. The etiology and mechanisms involved in this uncommon phenomenon are discussed. It is emphasized that a giant cell arteritis with cranial nerve involvement is a medical emergency, and that swift diagnosis and treatment is necessary to avoid permanent disability.

Pitfalls of automated perimetry in glaucoma diagnosis.

Perimetry is a cornerstone in glaucoma management. The detection of glaucomatous visual field loss is of crucial importance for diagnosing the disease. Automated threshold perimetry makes thorough testing of the central visual field very possible and high-quality data are often achieved. Certain factors, however, may hamper the visual field examination or visual field interpretation. Many diseases other than glaucoma are known to influence the visual field in more or less predictable ways. Of interest is also low patient reliability, learning and fatigue effects, as well as test artifacts and suboptimal test strategies or parameters. Finally, statistical aids provided by the built-in computer of the perimeter must be judged keeping in mind the population from which the patient is derived. We describe such pitfalls in glaucoma perimetry, how they can be identified, and dealt with clinically.

Stereoacuity and intraocular surgical skill: effect of stereoacuity level on virtual reality intraocular surgical performance.

PURPOSE: To evaluate the effect of stereoacuity on various intraocular surgical skills in inexperienced medical students using a virtual reality intraocular surgical simulator. SETTING: Department of Clinical Sciences, Malmö: Ophthalmology, Skåne University Hospital, Malmö, Sweden. DESIGN: Comparative case series. METHODS: Ninth‐semester medical students performed 1 iteration on each of the following 3 cataract training modules: navigation, forceps, and capsulorhexis. Before the simulator training, the trainees received standardized instructions and were allowed to perform 1 training round on the cataract navigation training module. After completion of the training, the level of stereoacuity was measured using TNO charts. Surgical performance for each task was measured, and performance parameter scores were recorded. RESULTS: The study included 70 students. The simulator performance score correlated with the level of stereoacuity for the navigation training module (Spearman r = 0.377, P=.001) and forceps training module (Spearman r = 0.306, P=.01), showing a gradual increase in surgical performance with increasing stereoacuity. No such relationship was found for the capsulorhexis module (Spearman r = 0.18, P=.136). CONCLUSIONS: A gradual detrimental effect on initial intraocular surgical skill with decreasing stereoacuity was shown. This calls for studies of the impact of deficient stereopsis on long‐term training effects. Financial Disclosure: Neither author has a financial or proprietary interest in any material or method mentioned.

Kinetic and static fixation methods in automated threshold perimetry.

PURPOSE Static fixation is the standard method for stabilizing the eye during automated perimetry. Kinetic fixation is an alternative for fixation control in which the eye follows a moving target. This study was conducted to evaluate the fixation accuracy of static and kinetic fixation perimetry and to determine their ability to detect the absolute scotoma of the physiologic blind spot. METHODS The 71 patients with early glaucomatous field loss (mean age 65 years) and 45 control subjects (mean age 57 years) recruited from five clinical sites underwent threshold testing on the Dicon perimeter (kinetic fixation; Vismed, San Diego, CA) and Humphrey Field Analyzer (static fixation). The frequency of Heijl-Krakau fixation catch-trial errors was used as an indicator of fixation accuracy, and the measured sensitivity at the physiologic blind spot was used as an indicator of perimetric accuracy. RESULTS In patients with glaucoma, the frequency of fixation errors was significantly greater for kinetic fixation (17.2%) than for static fixation (10.2%). In the control group, the frequency of fixation errors also was significantly greater for kinetic fixation (27.5%) than for static fixation (12.6%). The threshold at the presumed location of the blind spot (15 degrees temporal, 3 degrees inferior from fixation) was 14.8 dB using kinetic fixation versus 4.0 dB with static fixation in patients with glaucoma, and 18.5 dB using kinetic fixation versus 2.5 dB using static fixation in the control group. CONCLUSION Relative to static fixation, kinetic fixation was associated with fixation inaccuracy and underestimation of the absolute scotoma at the physiologic blind spot.