Optical Quality Analysis After Surface Excimer Laser Ablation: The Relationship Between Wavefront Aberration and Subepithelial Haze

Does corneal epithelial thickness show the severity of psoriasis? SD-OCT study

BACKGROUND

Previous studies have generally focused on dry eye test abnormalities and ocular involvements such as uveitis, and blepharitis in psoriasis. Psoriasis area severity ındex (PASI), which is used to assess psoriasis severity, is a time-consuming and complex tool.

OBJECTIVE

To evaluate the relationship between disease severity and central corneal epithelial thickness (CCET) in psoriasis.

METHODS

175 eyes of 175 psoriasis patients and 57 eyes of 57 healthy individuals as a control group was included in this study. Psoriasis patients were divided into three subgroups according to PASI score as < 10 mild, 10‒20 moderate and > 20 severe. CCET was measured by spectral domain-optical coherence tomography (SD-OCT), and mean values were recorded. Mean CCET values were compared between the psoriasis groups and the control group. Additionally, the relationship between PASI score and CCET was examined.

RESULTS

The mean CCET value was 58.06±3.1μm in the mild group, 60.10±5.0μm in the moderate group, 65.75±6.3μm in the severe group and 56.16±3.1μm in the control group. It was determined that the mean CCET value was significantly higher in all psoriasis groups compared to the control group (p<0.001). The mean CCET value was significantly higher in the moderate psoriasis group than in the mild psoriasis group (p=0.018), and in the severe psoriasis group compared to the moderate psoriasis group (p<0.001). There was a strong positive correlation between PASI score and CCET (p<0.001, r=0.519).

STUDY LIMITATIONS

Cross-sectional design and a relatively small number of participants.

CONCLUSIONS

There is a strong positive correlation between psoriasis severity and CCET. Contactless measurement of CCET by SD-OCT can be an indicator of psoriasis severity.

Evaluation of Corneal Epithelial Thickness Imaged by High Definition Optical Coherence Tomography in Healthy Eyes

PURPOSE

To evaluate corneal epithelial thickness (CET) and corneal thickness (CT) in healthy eyes using spectral domain optical coherence tomography.

METHODS

Thirty-six healthy eyes were imaged using the Cirrus high-definition (HD)-optical coherence tomography device. The average CET and CT were assessed using Cirrus Review Software within predefined concentric corneal ring-shaped zones. Specific regions of CET (superior, inferior, temporal, nasal, superonasal, inferotemporal, superotemporal, and inferonasal) were also assessed. The difference between zones was compared between males and females.

RESULTS

The average CET was 48.3, 47.1, 46.1, and 45.8 μm in the 4 concentric zones (0-2, 2-5, 5-7, and 7-9 mm), respectively (P < 0.001). The average CT was 533.5, 550.8, and 579.4 μm in the 3 zones (0-2, 2-5, and 5-7 mm), respectively (P < 0.001). There was no statistically significant correlation between CET and CT in any of the measured zones. Males had thicker corneas than did females in each of the 3 CT zones (P < 0.05), but CET did not differ significantly. The CET superonasal-inferotemporal in 2.0 to 5.0 mm and CET superotemporal-inferonasal in 5.0- to 7.0-mm zones were significantly thinner in males than in females (-1.15 vs. 0.9 μm, -3.5 vs. -1.9 μm), respectively (P < 0.05).

CONCLUSIONS

Optical coherence tomography-based analysis of CET reveals that it is thinner in the periphery, whereas the total corneal thickness is greater. Although total CT seems to be influenced by sex, CET is not. Regional and sex-based variations in CT may need to be considered when assessing corneal and epithelial alterations in the setting of disease.

Detailed Distribution of Corneal Epithelial Thickness and Correlated Characteristics Measured with SD-OCT in Myopic Eyes

Purpose

To investigate the detailed distribution of corneal epithelial thickness in single sectors and its correlated characteristics in myopic eyes.

Methods

SD-OCT was used to measure the corneal epithelial thickness distribution profile. Differences of corneal epithelial thickness between different parameters and some correlations of characteristics were calculated.

Results

The thickest and thinnest part of epithelium were found at the nasal-inferior sector (P < 0.05) and at the superior side (P < 0.05). respectively. Subjects in the low and moderate myopia groups have thicker epithelial thickness than those in the high myopia group (P < 0.05). Epithelial thickness was 1.39 μm thicker in male subjects than in female subjects (P < 0.001). There was a slight negative correlation between corneal epithelial thickness and age (r = −0.13, P = 0.042). Weak positive correlations were found between corneal epithelial thickness and corneal thickness (r = 0.148, P = 0.031). No correlations were found between corneal epithelial thickness, astigmatism axis, corneal front curvature, and IOP.

Conclusions

The epithelial thickness is not evenly distributed across the cornea. The thickest location of the corneal epithelium is at the nasal-inferior sector. People with high myopia tend to have thinner corneal epithelium than low–moderate myopic patients. The corneal epithelial thickness is likely to be affected by some parameters, such as age, gender, and corneal thickness.

Ocular higher-order aberration features 10 years after photorefractive keratectomy

The aim of the present study is to re-evaluate the original cohort of patients who participated in the first photorefractive keratectomy (PRK) trial in the 1990s, especially their optical performance. Forty-four eyes (24 patients) of the original cohort who underwent PRK using the NIDK EC-5000 excimer laser platform returned 10 years (range 9-14 years) postoperatively to have higher-order aberrations (HOAs) recorded. Wavefront aberrations were measured using Wavescan (VISX, Santa Clara, CA, USA) and calculated for 3- and 6-mm pupil size. The total RMS (the square root of the sum of squared Zernike coefficients) of higher-order wavefront error (3rd-6th radial order) and the Zernike coefficients, as well as the third-order (S 3) and fourth-order (S 4) aberrations, spherical aberrations and coma aberration values were analyzed. An independent sample t test was used for comparisons and a P value <0.05 was considered statistically significant. The mean RMS of higher-order wavefront values showed an increase but no significant difference in postoperative eyes compared to the control-matched normal level with the 6-mm pupil (HOA RMS: control group 0.31 ± 0.12 μm; 10-year post-PRK group 0.56 ± 0.15 μm; P = 0.141). The main contribution was the increase of spherical aberrations (Z 12) and spherical-like aberrations (S 4), which increased by fourfold and 2.5-fold, respectively, in the 10-year post-PRK group (control group Z 12 0.08 ± 0.11 μm, S 4 0.14 ± 0.05 μm; 10-year post-PRK group Z 12 0.35 ± 0.15 μm, S 4 0.37 ± 0.14 μm; P = 0.010*). Most increases of ocular HOAs induced by corneal refractive surgery are becoming extremely minor at 10 years postoperatively, closer to the corresponding preoperative amount. The largest increase was spherical and spherical-like aberrations, especially with a larger pupil size.