Fully automated biometry of in situ intraocular lenses using long scan depth spectral-domain optical coherence tomography.

PURPOSE: Spectral-domain optical coherence tomography (SD-OCT) was used to automatically measure accommodative biometric changes in the anterior segment of eyes implanted with an intraocular lens (IOL). The repeatability and reliability of the automated measurements were also evaluated. METHODS: Long scan depth SD-OCT was used to image the anterior segment of eyes implanted with IOLs. A fully automated algorithm was used to detect the boundaries of the cornea and IOL and yielded the measurements. The results included anterior segment dimensions in IOL eyes and the deflection of the IOLs. Automated measurements were validated in vitro and compared with the manual results in vivo on 15 cross-sectional images from patients with IOLs. Five eyes with five different types of IOLs, respectively, were enrolled to test the repeatability of the automated measurements during accommodation. RESULTS: Intraocular lens central thickness and anterior and posterior curvature radii measured by long scan depth SD-OCT in vitro and in a model eye matched well with those determined by a micrometer caliper and interferometer. In vivo, there was good correlation of the biometric data determined by automated and manual segmentations (P<0.05, r-value range: 0.635-0.997). There were no significant differences for any variable between the two measurements at each accommodative state (P>0.05). Anterior chamber depth and pupil diameter showed significant changes between the nonaccommodative and 2.5-D accommodative states (P<0.05), whereas the shape of the IOLs did not change significantly (P>0.05). CONCLUSIONS: The long scan depth SD-OCT with the automated algorithm was verified to have a great potential in studying accommodative biometric changes of the anterior segment in eyes with IOLs and IOL deflections.

Corneal reshaping and wavefront aberrations during overnight orthokeratology.

PURPOSE: To investigate changes of corneal thickness at the vertical and horizontal meridians and of wavefront aberrations (WA) over a 30-day period of overnight myopia orthokeratology (OK) lens wear. METHODS: Sixteen subjects (11 women, 5 men, 26.3±3.2 years) were enrolled and fitted for OK lenses. Long scan depth optical coherence tomography was used to measure corneal thickness profiles at both horizontal and vertical meridians at baseline and on days 1, 7, and 30 days. Corneal and ocular WA of a 6-mm pupil were measured and the root-mean-square (RMS) of the astigmatism, coma, spherical aberration (SA), and total higher-order aberrations (HOAs) were determined. RESULTS: During the 30-day period, the central cornea thinned in the horizontal and vertical meridians, whereas corneal thickening occurred in the temporal, nasal, and inferior mid-peripheries. In contrast, the cornea thinned in the mid-peripheral superior. There were significant increases in RMS for astigmatism, SA, coma, and positive horizontal coma during the study period. After OK, there were significant positive correlations between the midperipheral-central thickness change difference and the changes in corneal and ocular RMS of total HOAs and SA (r range: 0.281 to 0.492, P<0.05). Only the change of corneal coma RMS was correlated with midperipheral-central thickness change difference (r=0.270, P<0.05). The change in corneal horizontal coma was correlated with the temporal-nasal thickness change difference (r=-0.289, P<0.05). CONCLUSIONS: Overnight OK caused unique changes in corneal thickness profiles at the vertical and horizontal meridians and increased corneal and ocular HOAs related to corneal reshaping.

Influence of preoperative dilation time on the effect of cataract ultrasonography combined with goniostomy in patients with primary closed angle glaucoma and its clinical significance.

OBJECTIVE: To evaluate the impact of preoperative pupil dilation time on the outcomes of cataract ultrasonoemulsification combined with goniostomy in patients with primary angle-closure glaucoma (PACG). METHODS: A retrospective analysis was conducted on 106 PACG patients who underwent cataract ultrasonoemulsification with goniostomy. Patients were divided into two groups based on pupil dilation times: group A (dilation time between 20 to 30 minutes) and group B (dilation time between 30 minutes to 1 hour). Pre- and postoperative intraocular pressure (IOP), visual acuity, pupil diameter, anterior chamber depth (ACD), and lens thickness (LT) were measured. Surgical time and cumulative dissipated energy (CDE) were also analyzed. Multivariate analysis was performed to identify independent risk factors for postoperative complications. RESULTS: Both groups showed significant postoperative improvement in visual acuity (P < 0.05). Group B exhibited significantly lower postoperative IOP than group A (P < 0.05). There were significant increases in ACD and pupil diameter and a decrease in LT post-dilation in both groups (all P < 0.05). Group B showed a deeper ACD, thinner LT, and larger pupil diameter compared to group A (all P < 0.05). While CDE was similar between groups, operation duration was longer in group A (P < 0.05). Disease course > 5.5 years, preoperative IOP > 25.14 mmHg, pupil diameter before dilation < 4.895 mm, ACD before dilation < 2.105 mm, and dilation time ≤ 30 minutes were independent risk factors for postoperative complications. CONCLUSION: Preoperative pupil dilation time > 30 minutes leads to better surgical outcome. Several preoperative factors, including dilation time ≤ 30 minutes, are independent risk factors for postoperative complications.

Enhancing deep-UV emission at 234 nm by introducing a truncated pyramid AlN/GaN nanostructure with fine-tuned multiple facets.

The external quantum efficiency of a high-Al content (>0.6) AlGaN deep-ultraviolet (DUV) light-emitting diode is typically below 1% in the sub-250 nm wavelength range. One of the main reasons for this low efficiency is the fundamental properties of high-Al content AlGaN comprising the transverse-magnetic (TM)-dominant emission and low light extraction due to the total internal reflection (TIR). This work demonstrates a truncated pyramid nanostructure with fine-tuned multiple facets in an (AlN)8/(GaN)2 digital alloy to achieve highly efficient DUV emission at 234 nm. By applying nanoimprint lithography, dry and wet etching, a hexagonal truncated pyramid nanohole structure is fabricated featuring multiple crystal facets of (0001), (10-13), and (20-21) planes. These fine-tuned multiple facets act as reflecting mirrors that can effectively modulate the light propagation and extraction patterns to overcome the TIR via multiple reflections and enhanced scattering. Consequently, significant light extraction enhancements of 5.6 times and 1.1 times for TM and transverse-electric emissions are achieved in the truncated pyramid nanohole structure, respectively. The total luminous intensity of this unique nanostructure is greatly increased by 191% compared to that of a conventional planar structure. The truncated pyramid AlN/GaN nanostructure with fine-tuned multiple facets used in this work provides a promising approach for realizing highly efficient sub-250 nm DUV light-emitting devices.