Lele Cui

Ultra-high resolution optical coherence tomography for imaging the anterior segment of the eye.

Developments in optical coherence tomography (OCT) have expanded its clinical applications for ultra-high resolution imaging of the anterior segment of the human eye. This review presents the latest advances for imaging the anterior segment of the eye using ultra-high resolution OCT (UHR-OCT). Unique applications of UHR-OCT technology in clinical and basic scientific laboratory research are discussed and a summary of the results is provided. The authors focused on the use of UHR-OCT for imaging of tear dynamics, contact lens interactions with the corneal surface, and in vivo histological diagnosis of disorders of the cornea, as well as the future direction in this field.

Characterization of Soft Contact Lens Edge Fitting Using Ultra-High Resolution and Ultra-Long Scan Depth Optical Coherence Tomography

PURPOSE To characterize the edge fitting of soft contact lenses using ultra-high resolution optical coherence tomography (UHR-OCT) and ultra-long scan depth optical coherence tomography (UL-OCT). METHODS A total of 20 participants (11 men, 9 women; mean age, 32.3 years) were recruited. Four different types of soft contact lenses were randomly fitted to both eyes of each subject on two separate visits. After 30 minutes, the horizontal meridians of the corneal center, midperiphery, and limbus were imaged by UHR-OCT. UL-OCT imaged each lens in vitro and the ocular surface of a physical model eye. RESULTS Angle-edged lenses had significantly less conjunctival buildup than did round-edged lenses (P = 0.008). Limbal post-lens tear film gaps were present in 42% of the eyes, with the round-edged lenses having the most at 68%. Similarly, post-lens tear film gaps at the corneal mid-periphery were present in 47% of all eyes, with the round-edged lens having the most at 75%. Mismatches between the lens and the ocular surface were simulated based on UL-OCT images of the in vitro lenses and the model eye. The existence of tear film gaps and touching points were predicted in the simulation. CONCLUSIONS The soft contact lens edge fitting was characterized by the conjunctival buildup and tear film gaps. Different types of contact lenses presented different levels of conjunctival buildup as well as different frequencies of tear film gaps. The findings by UHR-OCT were predicted in the simulation by UL-OCT. The application of these new technologies may open new ways of designing lenses and evaluating their fit.

Extended scan depth optical coherence tomography for evaluating ocular surface shape

Spectral domain optical coherence tomography (SD-OCT) with extended scan depth makes it possible for quantitative measurement of the entire ocular surface shape. We proposed a novel method for ocular surface shape measurement using a custom-built anterior segment SD-OCT, which will serve on the contact lens fitting. A crosshair alignment system was applied to reduce the misalignment and tilting of the eye. An algorithm was developed to automatically segment the ocular surface. We also described the correction of the image distortion from the segmented dataset induced by the nontelecentric scanning system and tested the accuracy and repeatability. The results showed high accuracy of SD-OCT in measuring a bicurved test surface with a maximum height error of 17.4 μm. The repeatability of in vivo measurement was also good. The standard deviations of the height measurement within a 14-mm wide range were all less than 35 μm. This work demonstrates the feasibility of using extended depth SD-OCT to perform noninvasive evaluation of the ocular surface shape.

Ultra-high resolution optical coherence tomography for monitoring tear meniscus volume in dry eye after topical cyclosporine treatment

Purpose This study was designed to determine the ability of ultra-high-resolution optical coherence tomography (UHR-OCT) to monitor tear meniscus volume after dry eye treatment with Restasis® (0.05% cyclosporine). Methods UHR-OCT was used to image the upper and lower tear menisci (height and volume) in 14 consecutive dry eye patients at baseline. The treatment group was initiated on daily Restasis and measurements were repeated at 1 and 2 months while on treatment. All measurements were performed immediately after a blink. Results The baseline tear meniscus volumes were 0.40 ± 0.19 μL (upper) and 0.43 ± 0.18 μL (lower). In the treatment group, tear meniscus heights showed significant increases of both upper (post-hoc test with Bonferroni correction: P = 0.003) and lower (P = 0.0003) tear menisci, after 1 month on Restasis. The tear meniscus volumes in the treatment group after 1 month of Restasis showed significant increases of both upper (P = 0.007) and lower (P = 0.007) tear menisci. At 2 months, the increase of the tear meniscus was still evident in all measured variables compared with baseline (P < 0.05). Conclusion UHR-OCT offers a promising tool for monitoring dry eye treatment. With this method, a measurable increase in tear meniscus volume was evident after 1 month of treatment with Restasis in dry eye patients.

Micrometer-scale contact lens movements imaged by ultrahigh-resolution optical coherence tomography.

PURPOSE To dynamically evaluate contact lens movement and ocular surface shape using ultrahigh-resolution and ultralong-scan-depth optical coherence tomography (OCT). DESIGN Clinical research study of a laboratory technique. METHODS Four different types of soft contact lenses were tested on the left eye of 10 subjects (6 male and 4 female). Lens edges at primary gaze and temporal and nasal gazes were imaged by ultrahigh-resolution OCT. Excursion lag was obtained as the distance between the lens edge at primary gaze and immediately after the eye was quickly turned either nasally or temporally. The inferior lens edges were imaged continuously to track vertical movements during blinking. Ultralong-scan-depth OCT provided quantifiable images of the ocular surface, and the contour was acquired using custom software. RESULTS Excursion lag at the horizontal meridian was 366 ± 134 μm at temporal gaze and 320 ± 137 μm at nasal gaze (P > .05). The lens uplift at the vertical meridian was 342 ± 155 μm after blinking. There were significant differences in horizontal lags and vertical movements among different lenses (P < .05). Horizontal lags were correlated with radii of curvatures and sagittal heights at 6-mm and 14-mm horizontal meridian (P < .05). The blink-induced lens uplift first lowered by 104 ± 8 μm, and then lifted 342 ± 155 μm after the blink. CONCLUSIONS Ultrahigh-resolution and ultralong-scan-depth OCT can assess micrometer-scale lens movements and ocular surface contours. Both lens design and ocular surface shape affected lens movements.

Visualization of the precorneal tear film using ultrahigh resolution optical coherence tomography in dry eye.

Purpose: To visualize the precorneal tear film (PCTF) in dry eye patients using ultrahigh resolution optical coherence tomography (UHR-OCT). Methods: A custom-built UHR-OCT with ultrahigh resolution (∼3 &mgr;m) was used to image the PCTF at the vertical meridian. Eighteen right eyes of 18 previously diagnosed dry eye patients (9 men and 9 women, age, 47.8±20.7 years) with aqueous tear deficiency were studied. Images were taken during normal and delayed blinking. The visualized PCTF was measured directly. An indirect calculation was used to obtain the thickness in cases where the PCTF could not be visualized. Results: During normal blinking, the PCTF was visualized in 5 of 18 eyes (27.8%) with an average PCTF thickness of 5.8 &mgr;m (SD, 1.3 &mgr;m). During delayed blinking, the PCTF was visualized in 11 eyes (61.1%) with a significantly increased average thickness of 7.3 &mgr;m (SD, 0.9 &mgr;m; P<0.05). The percent increase of the visualized PCTF thickness was higher during delayed blinking compared with normal blinking (&khgr;2 test, P<0.05). The averaged PCTF was 4.4 &mgr;m during normal blinking, and the PCTF thickness was significantly increased to 6.6 &mgr;m (SD, 2.9 &mgr;m; P<0.05) during delayed blinking. Conclusions: We report the first visualization of PCTF in vivo in dry eye patients with UHR-OCT. Precorneal tear film can be directly visualized in some eyes during both normal and delayed blinking, and it seemed thicker during delayed blinking compared with normal blinking.

Detection of Magnetic Particles in Live DBA/2J Mouse Eyes Using Magnetomotive Optical Coherence Tomography

Objectives: To demonstrate in vivo molecular imaging of the eye using spectral-domain magnetomotive optical coherence tomography (MMOCT). Methods: A custom-built, high-speed, and high-resolution MMOCT was developed for imaging magnetic particle-coupled molecules in living mouse eyes by applying an external dynamic magnetic field gradient during optical coherence tomography (OCT) scanning. The magnetomotive signals were tested in vitro by scanning magnetic beads embedded within an agarose gel (1.5%) and in vivo in the anterior segment of a mouse eye. Results: Cross-sectional OCT images of the gel and the anterior segment of the eye were acquired by regular OCT structural scanning. Magnetomotive optical coherence tomography signals were successfully captured in the agarose gel with embedded magnetic beads. The signals were captured in the anterior segment of the mouse eyes after injecting the beads. The signal was overlaid successfully onto the structural OCT image. Conclusions: We demonstrated the ability to detect particles injected into the anterior chamber of the mouse eye using MMOCT. This suggests that MMOCT is effective for future live detection of molecular (protein) targets in various ocular diseases in mouse models.

The Watery Eye

The surface of the eye needs to be wet constantly to ensure its integrity in maintaining ocular comfort, clear vision, and ocular health. This article presents new findings in the tear dynamics of the human eye, with an emphasis on the tear meniscus and tear film through the day and in response to punctual occlusion and wearing of contact lenses. Recent advances in imaging technique are briefly discussed.

Characterization of Soft Contact Lens Fitting Using Ultra-Long Scan Depth Optical Coherence Tomography

Objectives To evaluate the centration and movement of soft contact lenses and to verify the repeatability of two repeated measurements of the lens centration and movement using ultra-long scan depth optical coherence tomography (UL-OCT). Methods A 1-day Acuvue® Define™ lens was tested on both eyes of 10 subjects (5 males and 5 females; mean age, 31.6 years). The centration and blink-induced movement of the contact lens were measured using UL-OCT at 5 min and 30 min after insertion. The measurements were repeated once at each checkpoint. Results Good repeatability was found in the lens centration and movement between the two repeated measurements at either checkpoint. The values of the lens movement were 0.457 ± 0.248 mm and 0.402 ± 0.229 mm at 5 min and decreased to 0.197 ± 0.065 mm and 0.211 ± 0.110 mm at 30 min after insertion for the right and left eyes, respectively (P < 0.05). Conclusions The custom-built UL-OCT presented good repeatability of centration and movement in Define lenses at 5 min and 30 min after insertion. Most of the lenses were centered temporal and inferior to the cornea during the first 30 min wearing period. Compared with 5 min after insertion, the lens was centered better and exhibited less movement at 30 min.