Comparison of measurements between manual and automated eyetracking systems in patients with strabismus – A preliminary study

Purpose: The main objective is to test the measurements made by an automated eye?tracking system in the presence of strabismus and to compare the data with manual measurements of deviation. Methods: A prospective observational cross?sectional masked double?blinded study was conducted in a tertiary eye care center with 39 participants included in our study, aged 3–41 years. Initial screening of all participants was performed by an ophthalmologist. Ocular deviations were evaluated and compared between manual measurements and an automated eye?tracking system. The device is based on eye?tracking technology. The participants had either a congenital or acquired type of manifest or latent strabismus. Children less than 3 years of age, visual acuity <6/36, and abnormal configuration of the anterior segment were excluded from the study. Results: The prism alternate cover test (PACT) manual measurements and the automated alternate cover test for measuring horizontal deviation, the manual measurement, and the automated eye track system showed a highly positive correlation (r = 0.932, P < 0.001). The Bland Altman plot analysis shows good agreement between the two measurements, with the mean difference between the two measurements being 1.55 PD, and the 95% limit of agreement was ± 10 PD. Conclusion: The results obtained with an automated eye?tracking system correlate well with manual strabismus measurements with PACT in terms of diagnosis, precision, and accuracy, with an added benefit of lesser time consumption in performing the test in cooperative/motivated patients. Considering these aspects, patients above the age of 3 years could be assessed with the equipment.

Laser Refractive Surgery Using an Active Eye-Tracking System in Congenital Nystagmus

PURPOSE: Nystagmus is not considered a good indication for laser refractive surgery. However, we report 2 cases with congenital nystagmus that underwent a safe procedure due to improvement of laser firing rate and eye tracker. CASE SUMMARY: Two myopic patients with congenital nystagmus underwent transepithelial photorefractive keratectomy with the Schwind Amaris laser platform using an eye tracker. The laser ablations were performed under topical anesthesia without any mechanical eyeball fixation. A 30-year-old man with a history of muscle surgery at 11 years of age had a conjugate, 4 Hz right beating jerk nystagmus. His preoperative refractive error was -8.50 D sph = -0.50 D cyl x 160degrees x 20/30) in the right eye, and -6.00 D sph = -0.75 D cyl x 30degrees x 20/25) in the left eye. A 19-year-old man had a conjugate, 3 Hz pendular nystagmus. His refractive error was -5.25 D sph = -2.50 cyl x 175degrees x 20/30) in the right eye, and -4.25 D sph = -2.50 D cyl x 180degrees x 20/30) in the left eye. Both patients underwent a well-centered laser ablation without any problems. Six months after surgery, uncorrected visual acuity was 20/25 or better, and refractive error was within +/-0.50 D in all 4 eyes. In addition, the 19-year-old man showed decreased nystagmus amplitude. CONCLUSIONS: In some patients with congenital nystagmus, laser refractive surgery may be safely and accurately performed under topical anesthesia using an active tracking system. The best uncorrected visual acuity may improve in certain patients postoperatively.

Topographical Analysis of Ablation Decentration Between Eye Tracker-assisted and Unassisted LASIK

PURPOSE: This study was aimed to evaluate the efficacy of an eye-tracking system, in terms of the amount of decentration. Comparison was made between two LASIK groups operated with and without the use of eye-tracking system. METHODS: An eye-tracking system was used in 41 eyes(Group 1) and patient fixation alone without an eye-tracking system in 41 eyes(Group 2). Corneal topography(Humphrey ATLAS(TM) Corneal Topography System; Zeiss Humphrey Systems, Dublin, California, U.S.A.) was performed before surgery and 3 months postoperatively. The amount of ablation decentration was measured on the difference map obtained from the axial map. RESULTS: The mean +/-SD of decentration was 0.38 +/-0.23 mm in group 1, and 0.49 +/-0.24 mm in group 2(p=0.047). The amount of decentration was graded as follows: grade I(1.0 mm). Grade I, there was a significantly less decentration in group 1(p=0.037). For grade II, however, there was no significant difference between the two groups(p=0.766). CONCLUSIONS: Using eye-tracking system alone may not be effective in decreasing moderate decentration. Good fixation of the patients seemed to be as effective as an eye tracking system in achieving good ablation centration.