Image Settings Affecting Nuchal Translucency Measurement Using Volume NT(TM) Software

PURPOSE: To evaluate the effects of the deviation from the mid-sagittal plane, fetal image size, tissue harmonic imaging (THI), and speckle reduction filter (SRF) on the measurement of the nuchal translucency (NT) thickness using Volume NT(TM) software. MATERIALS AND METHODS: In 79 pregnant women, NT was measured using Volume NT(TM). Firstly, the three-dimensional volumes were categorized based on the angle of deviation in 10degrees intervals from the mid-sagittal plane. Secondly, the operator downsized the fetal image to less than 50% of the screen (Method A) and by magnifying the image (Method B). Next, the image was magnified until the fetal head and thorax occupied 75% of the screen, and the NT was measured (Method C). Lastly, NT values were acquired with THI and SRF functions on, with each function alternately on, and with both functions off. RESULTS: The mean differences in NT measurements were -0.09 mm (p<0.01) between two-dimensional (2D) and a deviation of 31-40degrees and -0.10 mm (p<0.01) between 2D and 41-50degrees. The intraclass correlation coefficients (ICC) for 2D-NT and NT according to image size were 0.858, 0.923, and 0.928 for methods A, B, and C, respectively. The ICC for 2D-NT and NT with respect to the THI and SRF were 0.786, 0.761, 0.740, and 0.731 with both functions on, THI only, SRF only, and with both functions off, respectively. CONCLUSION: NT measurements made using Volume NT(TM) are affected by angle deviation from the mid-sagittal plane and fetal image size. Additionally, the highest correlation with 2D-NT was achieved when THI and SRF functions were used.

The Clinical Feature and Surgical Outcome of Infantile Exotropia

PURPOSE: To investigate the clinical features and treatment of infantile exotropia which developed in the first year of life. METHODS: The medical records of infantile exotropia operated on in our hospital were reviewed for preoperative and postoperative deviation, cycloplegic refraction, Worth 4-dot test and Titmus stereo acuity test. RESULTS: Preoperative mean deviation was 37 prism diopters. The average post-operative follow-up period was 26.5 months (12~86 months). Twelve patients (71%) had successful horizontal alignment with final horizontal deviations of less than 8 prism diopters, and five patients were undercorrected between 10 and 20 prism diopters. None were overcorrected. Six patients (35%) had fusion at distance and near as well as stereoacuity of 200 seconds of arc or less. Both preoperative and postoperative associated anomalies were inferior oblique muscle overaction (35%), dissociated vertical deviation (18%), both inferior oblique muscle overaction and dissociated vertical deviation (18%), nystagmus (12%) and V-pattern (6%). CONCLUSION: Although infantile exotropia is rare, it has similarities to infantile esotropia. Infantile exotropia features a large-angle deviation, accompanied with inferior oblique muscle overaction and dissociated vertical deviation. After operation, no cases were overcorrected, while high levels of binocular function, and stereoacuity developed in some cases.

Measurement of Angle Deviation Using Digital Photographs

PURPOSE: The prism-cover test has been known to be the most accurate method in measuring ocular angle deviation, but the Hirschberg test is used in poorly cooperative patients. To enhance the accuracy of Hirschberg test, we designed a geometric model using digital photographs. METHODS: Fifty normal volunteers were included in this study, who had no ocular disorders. Digital photographs were obtained in the subjects seated 2 m in front of the fixation targets and the camera was set 1 m in front of subjects. In each photograph, the apparent width of the cornea and the distance from the corneal light reflex to the limbus were measured using computer program for calculation of angle deviation. Then we compared the calculated angle deviation with the actual one. RESULTS: Calculated angle deviations with digital image photographs were corresponded to the actual ones from esodeviation 40delta to 10delta (p>0.05), whereas in esodeviation 60delta, 70delta and exodeviation, the larger the deviation angle, the larger the calculated angle composed with the actual one. CONCLUSIONS: Angle deviation measurement using digital photographs appears to be relatively precise and its clinical application will be available in measuring angle deviation of esodeviation.

A Study of the Change in Angle Deviation under General Anesthesia in Horizontal Strabismus Patients

We measured the angle deviation by prism cover test before operating and by Hirschberg's method while under a surgical plane of anesthesia and studied the changes in 105 patients with uncomplicated comitant horizontal strabismus who underwent muscle surgery in the Department of Ophthalmology, Dongsan Medical Center, Keimyung University School of Medicine from June 1985 to February 1987. We excluded from the study those patients with previous muscle surgery, neurological disease, and those with mechanical restrictions of eye movement detected either by clinical examination or positive forced duction tests under general anesthesia, or both. The results were as follows: 1. Angle deviation at far was 28.7 +/- 13.8 delta in exotropia and 39.9 +/- 15.6 delta in esotropia, revealing a significantly larger angle deviation in esotropia than exotropla. 2. The change in angle deviation under general anesthesia showed a decrease in the amount of preoperative angle deviation of 15.5 +/- 12.0 delta in exotropia and 27.2 +/- 17.7 delta in esotropia, significantly more decreased in esotropia than in exotropia. The change according to sex and age was of no significance in exotropia and esotropia. 3. The relationship between the preoperative angle deviation at far(DF) and that under general anesthesia(DA) was linear and could be written as the approximate regression formula: DA=0.40DF+2.20(r=0.76). 4. The relationship between the preoperative angle deviation at far(DF) and the change in angle deviation under general anesthesia[D(A-F)] was linear and could be written as the approximate regression formula: D(A-F)=-0.60DF+2.20 (r= -0.87). The change in angle deviation under general anesthesia revealed a decrease in the amount of preoperative angle deviation both in exotropia and esotropia and, in general, the larger the preoperative angle deviation was, the greater was the change in angle deviation under general anesthesia. 5. In exotropia, the change in angle deviation under general anesthesia according to the difference between preoperative angle deviation at near and far was -14.4 +/- 11.9 delta in cases of larger angle deviation at near than far, -18.3 +/- 9.6 delta in cases of larger angle deviation at far than near, and -18.8 +/- 15.4 delta in cases of the same angle deviation at near and far, respectively, which was of no clinical significance. 6. In esotropia, the change in angle deviation under general anesthesia according to the difference between preoperative angle deviation at near and far was +26.7 +/- 14.3 delta in cases of larger angle deviation at near than far, +35.3 +/- 27.3 delta in cases of larger angle deviation at far than near, and +25.6 +/- 18.3 delta in cases of the same angle deviation at near and far, respectively, which again was of no clinical significance. Thus, our results suggest that the eye position under surgical anesthesia has a tendency to change toward the anatomical position of rest and the innervational imbalance may play a major role in the causation of horizontal strabismus. It seems to have no influence in changing the preoperative surgical plan on the basis of the change in angle deviation under general anesthesia in horizontal strabismus patients.