Fourier-domain Optical Coherence Research Articles

Longitudinal Epithelial Thickness Profile Changes 18 Months After Photorefractive Keratectomy.

Long-term evaluation of corneal epithelial thickness (ET) profile changes after photorefractive keratectomy (PRK) using Fourier-domain anterior segment optical coherence tomography. Three hundred twenty-six eyes of 163 patients were included in this prospective observational study. The corneal epithelial map was obtained across a 9-mm diameter area of the cornea before and up to 27 months after surgery. ET was assessed in 25 sectors and 4 annular zones (central 2 mm, paracentral 2-5 mm, midperipheral 5-7 mm, and peripheral 7-9 mm). There was a significant reduction in mean ET in all zones 1 month after PRK. Subsequently, ET increased in all annular zones. The change in mean ET became stable in the midperipheral and peripheral zones at 3 to 6 months and in the central zone at 12 months, and it continued to increase in the paracentral zone even after 18 months after surgery. The ET was 3.40 μm and 4.05 μm in the central and paracentral zones at 6 months, respectively. Postoperative spherical equivalent changed significantly only from 1 to 3 months (P < 0.04). There was a significant correlation between postoperative spherical equivalent at month 1 and ET change in the paracentral and midperipheral zones (P < 0.027). There is a significant reduction in ET 1 month after myopic PRK with a gradual thickening thereafter until it reaches stability at 12 months in the central zone. However, it continues to change even after 18 months in the paracentral zone. The greatest thickening is in the paracentral zone, followed by the central zone.

Evaluation of meibomian gland and tear film changes in patients with pterygium.

Background:Recent studies have demonstrated that pterygium has a close relationship with dry eye disease. This study is to determine abnormalities in meibomian gland and tear function in patients with pterygium and to assess the relationship between the variables.Materials and Methods:Forty eyes from forty patients with primary nasal pterygium and forty eyes from forty volunteers without ocular pathologies were enrolled in this study. Ocular surface disease index scores, meibomian gland expression scores, lid margin abnormality scores, meiboscore, tear film breakup time (BUT), Schirmer test (SIT) value, and the lower tear meniscus height (TMH), tear meniscus depth (TMD), and tear meniscus area (TMA) using Fourier domain optical coherence were performed. Analysis of variance was applied for intergroup comparisons. A statistical significance level of P < 0.05 was considered.Results:Ocular symptom scores, BUT scores, lid margin abnormality, meibomian gland expression, and meiboscore were significantly higher in pterygium patients than in controls (P < 0.01 for all scores). However, the SIT scores, the lower TMH, TMD, and TMA values did not revealed a significant difference between two groups (all P > 0.05). Multivariate regression analysis demonstrated that meiboscore significantly correlated with ocular symptom scores, BUT, lid margin abnormality scores, and meibomian gland expression scores.Conclusions:Meibomian gland function may be altered in pterygium patients, which is associated with uncomfortable ocular symptoms. Being aware of meibomian gland changes seems essential to understand the complex relationship among pterygium, tear film functions, and ocular surface changes.

Defocus and numerical focusing in interference microscopy with wide time-varying spectrum of illumination field

This paper presents an analysis of the influence of illumination with wide temporal spectrum on the properties of a defocused interference signal and numerically focused imaging in interference microscopy. It is shown that the differences in defocus influence on different spectral components of a signal with wide temporal spectrum may lead to degradation of the images of defocused sample parts, in spite of the use of numerical focusing. The magnitude of these effects depends on the temporal spectrum width, the numerical aperture of the imaging system and the amount of defocus. The influence of these effects on the properties of numerically focused imaging in Fourier domain optical coherence tomography/microscopy is considered.

Short-term effects of topical cyclosporine A 0.05% (Restasis) in long-standing prosthetic eye wearers: a pilot study.

Long-standing prosthetic eye wearing induces ocular surface inflammation. We investigated the short-term effects of topical cyclosporine A 0.05% (Restasis) in patients with ocular discomfort resulting from long-standing prosthetic eye wearing. This was a prospective, interventional case series. Patients who were unilateral prosthetic eye wearers over a period of 5 years were enrolled at a single institution from March to July 2013. The subjects were instructed to instill topical cyclosporine A 0.05% twice per day. Measurements were made pre-treatment and after 1 and 3 months of treatment. Outcome measures were the ocular symptom score, the lid margin abnormality score, the Schirmer test, and the tear meniscus amount, using Fourier-domain optical coherence tomography. In total, 20 consecutive patients (mean age: 60.1 years, 8 males, 12 females) were included. Ocular symptoms were improved after treatment for 1 month in all patients (ocular symptom score pre-treatment 76.83 vs 46.75 after treatment; P<0.001). There was no statistically significant difference in lid margin abnormality score or tear meniscus amount. The Schirmer test results were improved after treatment for 3 months (pre- and after treatment, 6.70 vs 11.40; P<0.001). Topical cyclosporine A 0.05% showed a satisfactory effect in long-standing prosthetic eye wearers. Ocular symptoms were markedly relieved in all subjects after treatment for 1 month.

Pachymetry Map of Corneal Epithelium in Children Wearing Orthokeratology Contact Lenses

Purpose: To study the pachymetry map of the corneal epithelium in children wearing orthokeratology lenses automatically generated by a Fourier-domain optical coherence tomography.Materials and Method: The study was conducted on 60 children who had been fitted with myopic orthokeratology lenses. Patients were divided into two groups according to the duration of OK lens treatment (group 1: ≤14 days, n = 28; group 2: >14 days, n = 32). The control group consisted of 44 children. An FD-OCT device with a pachymetry module was used to map the central 6-mm corneal epithelial thickness. An epithelial thickness map was automatically generated and divided into three zones: central 2 mm, paracentral 2 to 5 mm (P1) and mid-peripheral 5 to 6 mm (P2). The average epithelial thickness of central (C), the temporal (T1), nasal (N1), superior (S1) and inferior (I1) sectors of P1, and the temporal (T2), nasal (N2), superior (S2) and inferior (I2) sectors of P2 were recorded and compared. The minimum and maximum points of epithelial thickness across the map were also recorded. Munnerlyn’s formula was used to model the expected change in refractive error based on Δ(Max-Min) (Δ(Max-Min) = (Max-Min)study-(Max-Min) mean of control).Results: The central epithelial thickness was significantly different between individual groups and a significant difference from the control (Group 0) was seen in each treatment group. Both the epithelial thickness measurements of T1 and I1 were thinnest in Group 1. Both the epithelial thickness measurements of S2 and I2 were thickest in Group 2. The difference between maximum and minimum thickness was significantly different between groups with the largest effect in Group 2. The refractive changes predicted by Munnerlyn’s formula were less than the actual refractive changes measured in both study groups.Conclusions: The epithelial thickness map automatically generated by FD-OCT can provide regional information about corneal epithelium thickness following overnight wearing of OK lenses.

Outcomes of 4-Snip Punctoplasty for Severe Punctal Stenosis: Measurement of Tear Meniscus Height by Optical Coherence Tomography

To investigate the surgical outcome of rectangular 4-snip punctoplasty, a modification of rectangular 3-snip procedures, using objective measurements. Noncomparative case series. The medical charts of patients who underwent rectangular 4-snip punctoplasty for severe punctal stenosis with at least 6 months follow-up were reviewed. Before surgery and at 1 and 6 months after surgery, subjective evaluation of tearing was assessed using Munk scores. The size of the punctum was graded based on slit-lamp examination, and measurement of tear meniscus height was done using Fourier-domain optical coherence tomography. A total of 45 eyes (26 patients) were studied. The subjective epiphora score was significantly reduced after surgery and maintained until 6 months after the surgery (χ2 for trend test, P<.001). The grade of the punctum size was also significantly enlarged after surgery and the enlarged punctum was maintained until 6 months after the surgery (χ2 for trend test, P<.001). The mean preoperative tear height (452.4±249.3 μm) was significantly reduced both at 1 month after surgery (341.6±207.9 μm; P=.003, paired t test) and at 6 months after surgery (362.1±212.6 μm; P=.004, paired t test). The functional success rate was 93.3% and anatomic success rate was 88.9% at 6 months after surgery. Rectangular 4-snip punctoplasty was an anatomically and functionally effective procedure for severe punctal stenosis patients, maintaining large puncta for fairly long periods.

Comparing the ganglion cell complex and retinal nerve fibre layer measurements by Fourier domain OCT to detect glaucoma in high myopia

AimTo compare the diagnostic ability to detect glaucomatous changes between peripapillary retinal nerve fibre layer (RNFL) thickness and the macular ganglion cell complex (GCC) in highly myopic patients using Fourier...

Slit-Lamp-Adapted Fourier-Domain OCT for Anterior and Posterior Segments: Preliminary Results and Comparison to Time-Domain OCT

Purpose: To evaluate the diagnostic potential of a slit-lamp (SL)-adapted Fourier-domain (= spectral radar, SR) optical coherence tomography (OCT)—SL-SR-OCT—instrument as an in vivo imaging device for use in examinations of the anterior and posterior segments.Materials and Methods: In a pilot study, 88 eyes from 70 healthy volunteers and patients were examined using a prototype Fourier-domain SL-SR-OCT system. Results were compared to those from the following commercially available systems: the 1310-nm SL-OCT (Heidelberg Engineering, Heidelberg, Germany) for anterior segment and the Stratus OCT (Zeiss Meditec, Jena, Germany) for posterior segment imaging. Our SL-SR-OCT provides 1025 axial scans, 5000 Hz line-scan frequency, scan length of up to 8 mm, axial depth in air of 3.5 mm, and resolution of 9 μm. For posterior visualization, a hand-held 78-diopter ophthalmoscopic lens was used.Results: Our SL-SR-OCT system allowed simultaneous scanning with direct biomicroscopic and SL imaging of anterior and posterior segment structures. Anatomical structures and pathological changes were displayed with high resolution and excellent contrast. Measurements of corneal and retinal thickness were possible. In comparison to images obtained by the SL-OCT, our SL-SR-OCT boasted a higher resolution, thus providing more clinically relevant details of the corneal epithelium, internal structure of filtering blebs, etc. Complete imaging of the chamber angle was limited, however, due to the backscattering properties of the sclera at 830 nm. For posterior segment imaging, excellent delineation of the macula and optic nerve head details, with a distinct portrayal of macular pathology and retinal edema, was possible with SL-SR-OCT.Conclusion: SL-SR-OCT enables detailed imaging of physiological and pathological anterior and posterior segment structures. As a multi-purpose device, it offers a wide spectrum of applications, with high-quality OCT-imaging, in a comfortable setting without the need to move the patient.

An Agonistic TrkB mAb Causes Sustained TrkB Activation, Delays RGC Death, and Protects the Retinal Structure in Optic Nerve Axotomy and in Glaucoma

Brain-derived neurotrophic factor (BDNF) receptors TrkB and p75(NTR) are expressed in the retina. However, exogenous BDNF does not provide retinal ganglion cells (RGCs) with long-lasting neuroprotection in vivo during optic nerve axotomy or in glaucoma rat models of neurodegeneration. The authors set out to answer the hypothesis that a selective TrkB agonist might afford more efficient neuroprotection. Animal models of acute neurodegeneration (complete optic nerve axotomy) and chronic neurodegeneration (ocular hypertension, glaucoma) were used. After intravitreal delivery of test agents or controls, surviving RGCs were quantified. Transient or sustained activation of TrkB receptors in vivo was quantified by Western blot analysis retinal samples for TrkB-phosphotyrosine. Time-dependent changes to the neuronal retinal layers were quantified longitudinally by Fourier domain-optical coherence tomography. The authors show that a selective TrkB agonist caused long-lived TrkB activation and significantly delayed RGC death in these models of acute and chronic retinal injury in vivo. Importantly, using noninvasive retinal imaging, they also show that a selective TrkB agonist caused preservation of the retinal structure in both animal models, with maintenance of the layers comprising neurons and neuronal fibers. In animal models of acute and chronic neurodegeneration, a TrkB agonist affords long-lasting neuroprotection by causing sustained TrkB activation. The use of structural end points could have prognostic value to evaluate neuroprotection. This work contributes to the understanding of neurotrophic mechanisms underlying RGC death in glaucoma and optic nerve axotomy.

Comparison of Macular Thickness Measurements Between Fourier-Domain and Time-Domain Optical Coherence Tomography in Normal Eyes and Eyes With Macular Diseases

Purpose: To define and measure macular thickness and volume using Fourier domain OCT (FD OCT) and compare the values with Stratus OCT in normal eyes and eyes with macular disease. Methods: On the same day, macular thicknesses of the ETDRS 9 subfield and total macular volumes were measured in 35 eyes of 23 normal subjects and 19 diseased eyes of 24 patients with FD OCT and Stratus OCT. The macular cube scan protocol for FD OCT and the fast macular thickness map protocol for Stratus OCT were used to measure macular thicknesses. Results: Foveal thickness of the central subfield in FD OCT (251.49) was thicker than the value of Stratus OCT (210.26 ) (p and 7.040.96 for FD OCT and Stratus OCT, respectively (p