Virtual reality ophthalmic surgical simulation as a feasible training and assessment tool: results of a multicentre study.

OBJECTIVE: To compare performance on the Eyesi surgical simulator by users with different levels of experience in ophthalmology. DESIGN: Multicentre cross-sectional study. PARTICIPANTS: Four medical students, 4 ophthalmic medical technologist trainees, 36 ophthalmology residents, 3 fellows, and 18 staff ophthalmologists. METHODS: Subjects were recruited at the 2007 Canadian Ophthalmological Society Meeting and in the departments of ophthalmology at the University of Toronto, University of Ottawa, and University of Western Ontario. Subjects performed a standardized 20-minute session on the Eyesi simulator. The protocol consisted of a practice trial in the anterior segment module, followed by 3 scored trials in the anterior forceps, antitremor, and capsulorhexis modules. RESULTS: In the forceps module, participants with greater experience achieved significantly higher total scores than those who were less experienced: staff ophthalmologists (Group D) = 67.9 (SD 18.4), senior residents and fellows (Group C) = 67.6 (SD 21.1), junior residents (Group B) = 52.9 (SD 29.4), medical students and ophthalmic medical technologist trainees (Group A) = 27.8 (SD 29.4) (p = 0.011), with lower total task time (p = 0.044) and fewer injuries to the cornea (p = 0.001) and lens (p = 0.026). In the antitremor module, subjects in Group D achieved significantly higher (p = 0.004) total scores (46.7, SD 21.6) than Groups C (45.8, SD 25.1), B (41.2, SD 29.4), and A (8.5, SD 9.2) with lower total task time (p = 0.005) and fewer errors (p = 0.003). In the capsulorhexis module there was also a positive correlation between experience and total scores achieved (p = 0.065). CONCLUSIONS: Subjects' level of training is a reliable predictor of their performance on the Eyesi anterior forceps and antitremor modules (p < 0.05), indicating the modules' construct validity.

Pneumotonometry versus Goldmann tonometry after laser in situ keratomileusis for myopia.

PURPOSE: To assess the reliability of intraocular pressure (IOP) measurement by Goldmann applanation tonometry (GAT) versus pneumotonometry in patients after laser in situ keratomileusis (LASIK) for myopia. SETTING: Shiley Eye Center, University of California San Diego, La Jolla, California, USA. METHODS: In this prospective study, 31 eyes of 17 patients were evaluated before and 1 month after having LASIK for myopia. A masked observer measured preoperative and postoperative IOP by GAT centrally and by pneumotonometry at the center and the periphery of the cornea. Central corneal thickness and curvature were evaluated. RESULTS: Preoperative IOP showed a good correlation between GAT and pneumotonometry values (r = 0.82). Mean postoperative IOP by GAT was lower by 3.8 mm Hg +/- 2.2 (SD) (26.3% +/- 15.2%) than by pneumotonometry: 2.3 +/- 2.8 mm Hg (15.4% +/- 10.7%) (P = .01). There were no statistically significant differences in central IOP versus peripheral IOP measured by pneumotonometry (P = .4). Regression analysis showed no statistically significant differences in IOP as a function of change in corneal thickness or change in corneal curvature with either device. CONCLUSION: Postoperatively, there was a decrease in IOP measured by central GAT that was statstically significant. Differences in pneumotonometry were less substantial, with greater reliability of pneumotonometry than GAT after LASIK.

Intraocular pressure measurement in patients with instrastromal corneal ring segments.

PURPOSE: To study the measurement of intraocular pressure after implantation of Intacs (ICRS) intrastromal corneal ring segment, a device that is positioned circumferentially in the peripheral corneal stroma to correct myopia. The device changes the corneal curvature by shortening arc length. Since the ring segments are made of polymethylmethacrylate, this may cause localized changes in corneal elasticity so intraocular pressure measurement may be affected. METHODS: We measured the intraocular pressure of 12 eyes in which the ICRS had been in place longer than 6 months. We used Goldmann applanation and Tono-Pen tonometers over the central corneal and the paracentral corneal areas. We also measured the intraocular pressure with the Tono-Pen applanated directly over the intrastromal corneal ring segments. RESULTS: The resulting intraocular pressure measurements were similar for the Tono-Pen tonometer readings over the central cornea, paracentral cornea, and the Goldmann applanation tonometer readings over the central cornea (P < .01). Our measurements using the Goldmann applanation tonometer on the paracentral corneal area showed artificially elevated intraocular pressure in the 40 to 60 mmHg range. We were not able to obtain consistent results when we measured the intraocular pressure using the Tono-Pen on the corneal area directly overlying the intrastromal corneal ring segment implants. CONCLUSION: Consistent intraocular pressure measurements on eyes with the ICRS can be obtained with the Goldmann applanation tonometer over the central corneal area or with the Tono-Pen tonometer over the central or paracentral corneal areas.

Möbius syndrome with oculomotor nerve paralysis without abducens paralysis.

Möbius syndrome is typified by bilateral facial nerve palsies, usually with abducens palsies. We examined an infant with Möbius syndrome who had bifacial weakness and third nerve palsies, but intact abduction of both eyes. Lower cranial nerve involvement, leading to respiratory, swallowing, and cardiac difficulties, was also present. Pathologic examination of the brainstem showed absent or hypoplastic third, seventh, tenth, and twelfth nerve nuclei. The fourth, fifth, sixth, and eighth nerve nuclei were intact. In Möbius syndrome with ocular motor palsies, rarely the sixth nerve may be spared.

Age-related deterioration of motion perception and detection.

PURPOSE: The purpose of this study was to evaluate the effect of aging on motion detection and perception. METHODS: Forty-six subjects, ages 19-92 years, were asked to view a motion stimulus. Infrared oculography was used to objectively evaluate motion detection by documenting the presence of optokinetic nystagmus as the subjects viewed the stimulus. Subjective responses to motion perception were recorded using a computer joystick. RESULTS: Optokinetic nystagmus was clearly detectable in all 46 subjects. Motion detection and perception thresholds showed age-related deterioration. No relationship was found to gender or age-gender interaction. CONCLUSION: The results indicate motion detection and perception thresholds deteriorate with age. This may reflect a susceptibility to age-related degeneration in specific cortical areas responsible for motion perception as well as neurodegeneration in the retinogeniculate pathway.

Dissociation between the detection and perception of motion in Alzheimer's disease.

To better understand the damage to the motion pathway that occurs in senile dementia of the Alzheimer type (SDAT), we developed a system to assess separately the conscious perception and unconscious detection of motion in patients with SDAT. Motion perception thresholds were significantly elevated in SDAT (n = 9) compared with controls (n = 12), but motion detection thresholds were normal. This dissociation between the perception and detection of motion in early SDAT parallels histologic evidence of a disconnection between primary and association visual cortices. This disconnection may underlie the severe visual perception deficits seen in SDAT.