Anterior Segment Biometry Changes with Cycloplegia in Myopic Adults.

PURPOSE: To determine the effect of cycloplegia on corneal thickness, corneal curvature, anterior chamber depth (ACD), angle-to-angle (ATA) and white-to-white (WTW) distances, and axial length (AL). METHODS: Changes in corneal thickness, corneal curvature, ACD, ATA and WTW distances, and AL with and without cycloplegia were analyzed in 31 eyes of 31 young myopic adults, aged 26.4 ± 3.0 years. Pentacam was used to measure the corneal thickness, corneal volume, and corneal curvatures. Visante optical coherent tomography (OCT) measured corneal thickness, ATA distance, ACD, and pupil size. The AL and WTW distance were measured using IOLMaster. RESULTS: Cycloplegia induced significant flattening of corneal curvatures (p = 0.019, 0.001, and 0.003 for anterior sagittal, posterior tangential, and posterior sagittal curvatures, respectively). The difference in the posterior corneal curvature was greater in corneas with steeper posterior curvatures. Cycloplegia also induced significant deepening of ACD (0.08 ± 0.06, p < 0.001) and widening of both WTW (0.42 ± 0.43, p < 0.001) and ATA (0.08 ± 0.17, p = 0.015) distances. The cycloplegia-related increase in the ATA distance correlated negatively with AL (r = -0.361, p = 0.046), whereas the cycloplegia-related increase in WTW distance correlated weakly with the increase in ACD (r = 0.347, p = 0.056) but not with AL. The AL did not change with cycloplegia. Pentacam measured a slightly thicker cornea than OCT (p = 0.002). Both Pentacam and OCT detected a significant increase in corneal thickness of 4 µm, which could be attributed to reflex tearing, after cycloplegia. CONCLUSIONS: Cycloplegia resulted in deeper ACD, greater ATA distance, and flatter corneal curvatures. Surgeons should be aware of these cycloplegia-related alterations for more accurate phakic/functional intraocular lens selection and better refraction results.

Noncontact detection of dry eye using a custom designed infrared thermal image system.

Dry eye syndrome is a common irritating eye disease. Current clinical diagnostic methods are invasive and uncomfortable for patients. This study developed a custom designed noncontact infrared (IR) thermal image system to measure the spatial and temporal variation of the ocular surface temperature over a 6-second eye-open period. This research defined two parameters: the temperature difference value and the compactness value to represent the temperature change and the irregularity of the temperature distribution on the tear film. Using these two parameters, this study achieved discrimination results for the dry eye and the normal eye groups; the sensitivity is 0.84, the specificity is 0.83, and the receiver operating characteristic area is 0.87. The results suggest that the custom designed IR thermal image system may be used as an effective tool for noncontact detection of dry eye.

Anterior chamber depth measurement in phakic and pseudophakic eyes.

PURPOSE: To compare anterior chamber depth (ACD) measurements using two non-contact optical devices, Pentacam and IOLMaster, and a contact device, ultrasonic A-scan in phakic and pseudophakic eyes. METHODS: Ninety phakic and 94 pseudophakic eyes were enrolled in this prospective study. The difference between ACD measurements by the three devices was analyzed using the repeated-measures analysis of variance, and agreement among the three measurements was investigated. The accuracy of detecting the anterior lens surface of the intraocular lens (IOL) with or without blue-blocker was also assessed. RESULTS: In phakic eyes, the Pentacam measured the deepest ACD with the smallest standard deviation (3.26 +/- 0.41, 3.20 +/- 0.45, and 3.12 +/- 0.44 mm measured by Pentacam, IOLMaster, and A-scan, respectively, p < 0.001). In contrast, the Pentacam measurement of ACD had the largest standard deviation in pseudophakic eyes (4.05 +/- 0.58, 4.06 +/- 0.46, and 3.81 +/- 0.41 mm by Pentacam, IOLMaster, and A-scan, respectively, p < 0.001). The Pentacam instrument failed to correctly identify the anterior lens surface in 26.4% of IOLs without blue-blocker and in 58.5% of blue light-filtering IOLs (p = 0.016). Manual correction of the Pentacam image and subsequent ACD measurement improved the agreement between Pentacam and the other two devices. After manual adjustment, the average ACD value increased, and the standard deviation decreased significantly (4.34 +/- 0.28 mm). CONCLUSIONS: ACD measurements by Pentacam, IOLMaster, and A-scan were in better agreement in phakic eyes when compared with pseudophakic eyes. In pseudophakic eyes, the 95% limits of agreements between Pentacam and IOLMaster as well as Pentacam and A-scan were unsatisfactory. IOLs with blue-blocker might interfere with ACD measurements. However, this error can be corrected manually in the Pentacam examination.