A Novel Entity of Corneal Diseases with Irregular Posterior Corneal Surfaces: Concept and Clinical Relevance

Does Corneal Topography Using 3-Dimensional Optical Coherence Tomography Suggest Different Subtypes of Terrien Marginal Degeneration?

PURPOSE

The aim of this study was to analyze corneal topography relative to astigmatism, higher order aberrations, and corneal curvatures in Terrien marginal degeneration using 3-dimensional anterior-segment optical coherence tomography.

METHODS

Twenty-nine eyes of 15 Finnish patients from a tertiary referral center had topographic axial power maps classified into 4 patterns by visual grading: crab claw (CC), mixed (M), arcuate (A), and normal. Regular astigmatism, keratometry, higher order aberrations, maximal corneal thinning, apex thickness, and curvature changes relative to best fit sphere toward maximal peripheral thinning were compared.

RESULTS

Four, 9, and 12 eyes were classified as CC, M, and A, respectively; 1 as normal with clinical disease; and 3 as normal with unilateral disease. Median follow-up was 2.3 (range, 0-7.2) years. Three eyes changed pattern. Patients with the CC pattern were the youngest when diagnosed, progressed more rapidly, exhibited cavities in superior quadrants with anterior bulging, and had greater higher order posterior aberrations. Patients with the M pattern were older, progressed slower, and showed superonasal asymmetric corneal steepening extending centrally, often with asymmetric bow tie. Patients with pattern A showed little progression and were the oldest when diagnosed, with maximal corneal thinning equally in all quadrants. According to the Wang classification, the median stage was 4, 2, and 2 in CC, M, and A patterns, respectively, whereas it was always 2 by the Süveges classification.

CONCLUSIONS

Terrien marginal degeneration is characterized by distinct corneal topographic patterns that differ in tomographic features, suggesting existence of subtypes in addition to different stages of disease. Patients representing CC and M patterns might benefit from more frequent monitoring.

Quantitative evaluation of corneal irregularity and scarring after infectious keratitis using anterior segment optical coherence tomography

PURPOSE

Corneal scars after infectious keratitis lead to insufficient transparency and irregular astigmatism, affecting visual acuity; therefore, they should be accurately evaluated to estimate visual function. This study aimed to quantitatively evaluate corneal irregularity and scarring after infectious keratitis using anterior segment optical coherence tomography (AS-OCT).

METHODS

This was an observational clinical study. We included patients who had corneal scarring after treatment of infectious keratitis between 2014 and 2021 at University of Tokyo Hospital. We retrospectively examined best spectacle-corrected visual acuity (BSCVA), average keratometric power, central corneal thickness (CCT), and four components of the Fourier harmonic analysis including spherical and asymmetry components, as well as regular astigmatism and higher-order irregularity. We included anterior and posterior corneal data and compared results with those of contralateral healthy eyes. Additionally, we quantitatively evaluated the densitometry of the cornea obtained using AS-OCT.

RESULTS

A total of 122 eyes of 61 patients were examined; male predominance was observed (n = 37), and the mean patient age was 55.3 ± 19.4 years. Comparisons with contralateral healthy eyes showed that BSCVA worsened (0.30 ± 0.83 and 0.93 ± 1.36 logMAR, respectively, P = 0.003), and CCT (531.1 ± 46.2 and 591.8 ± 132.4 μm, respectively, P < 0.001) and corneal densitometry (84.4 ± 11.8 and 111.9 ± 19.2 grayscale units, respectively, P < 0.001) increased significantly in affected eyes. The asymmetry component and higher-order irregularities that were not corrected with spectacles significantly increased (both P < 0.001), and there were no significant differences in the changes among the bacterial, fungal, herpetic, and acanthamoeba types of keratitis.

CONCLUSION

Corneal scarring persisted after treatment for infectious keratitis, and the asymmetry and irregularities of corneal astigmatism increased as visual acuity deteriorated. AS-OCT with the Fourier harmonic analysis was useful for evaluating corneal topographic changes in patients with corneal scarring after keratitis.

Association between Corneal Higher-Order Aberrations Evaluated with a Videokeratographer and Corneal Surface Abnormalities in Dry Eye

Analysis of higher-order aberrations (HOAs) is one reported method for evaluating dry eye disease (DED)-related loss of visual function. Tear film (TF) instability and corneal epithelial damage (CED) are both reportedly responsible for HOAs in DED, although, to the best of our knowledge, there are no reported methods that allow concurrent evaluation of their effects. In this study, we used a videokeratographer (VK) to continuously measure HOAs in DED after eye opening and investigated factors of ocular surface abnormalities that determine HOAs. This study involved 96 DED cases that underwent DED symptom assessment with a questionnaire and examination of tear volume, TF abnormalities (i.e., TF lipid-layer interference grades and spreading grades, and non-invasive breakup time and fluorescein breakup time), and CED, and their correlation with HOAs evaluated via VK. The results show that HOAs at 1 or 2 s after eye opening can reflect TF instability and CED within the central 4-millimeter-diameter area of the optical zone in DED eyes concurrently. This finding may be useful for the rapid and non-invasive detection and evaluation of degraded visual function in DED cases with a variety of clinical features.

Changes in corneal higher-order aberrations during treatment for infectious keratitis

This study aimed to quantify the changes in corneal higher-order aberrations (HOAs) before and after treatment for infectious keratitis and verify the correlation between corneal HOAs and visual acuity. Corneal HOAs were analysed using swept-source anterior segment optical coherence tomography (AS-OCT). Ninety-eight eyes of 96 consecutive patients with infectious keratitis treated with topical eye drops were retrospectively evaluated. Corneal HOAs increased with the infection but decreased with infection resolution following antimicrobial treatment. Corneal HOAs became larger as the degree of corneal findings became more severe. The increase in HOAs of the total cornea was correlated with the decrease in visual acuity both before and after treatment (4 mm, ρ = 0.530 and 0.590; 6 mm, ρ = 0.479 and 0.567, respectively; all P < 0.0001). Furthermore, pretreatment HOA (anterior, 6 mm), pretreatment logMAR best spectacle-corrected visual acuity, and age were prognostic factors significantly associated with posttreatment visual acuity (β = 0.31, P = 0.013; β = 0.36, P < 0.0001; and β = 0.35, P = 0.0007, respectively) (adjusted R² = 0.474). These results indicate that corneal HOAs quantified using AS-OCT can be used as an objective index to evaluate corneal optical function during the treatment of infectious keratitis.

Corneal irregularity and visual function using anterior segment optical coherence tomography in TGFBI corneal dystrophy

The purpose of this study was to evaluate corneal irregular astigmatism of patients with granular and lattice corneal dystrophy (GCD and LCD). 70 GCD, 35 LCD, and 81 control eyes were included. Anterior and posterior corneal topographic data obtained from anterior segment optical coherence tomography were expanded into four components via Fourier harmonic analysis. These components were compared with healthy eyes and the association between each component and best-corrected visual acuity (BCVA) was investigated. Anterior and posterior components increased in both GCD and LCD eyes. Anterior and posterior components of GCD2, anterior of LCD type 1 (LCD1), posterior of LCD type IIIA (LCD 3A), and type IV (LCD4) significantly increased. BCVA was significantly associated with anterior and posterior components in LCD eyes but not in GCD. The anterior components of LCD1, anterior and posterior of LCD3A, and posterior of LCD4 , were positively correlated with BCVA. As conclusions, in GCD eyes, anterior and posterior components differed from those of the control but BCVA was not significantly associated with them. In LCD eyes, the anterior and posterior components increased, and BCVA was significantly associated with the anterior and posterior components.

Evaluation of corneal nerves and dendritic cells by in vivo confocal microscopy after Descemet's membrane keratoplasty for bullous keratopathy

This study evaluated changes in corneal nerves and the number of dendritic cells (DCs) in corneal basal epithelium following Descemet membrane endothelial keratoplasty (DMEK) surgery for bullous keratopathy (BK). Twenty-three eyes from 16 consecutive patients that underwent DMEK for BK were included. Eyes of age-matched patients that underwent pre-cataract surgery (12 eyes) were used as controls. In vivo confocal microscopy was performed pre- and postoperatively at 6, 12, and 24 months. Corneal nerve length, corneal nerve trunks, number of branches, and the number of DCs were determined. The total corneal nerve length of 1634.7 ± 1389.1 μm/mm² before surgery was significantly increased in a time-dependent manner to 4485.8 ± 1403.7 μm/mm², 6949.5 ± 1477.1 μm/mm², and 9389.2 ± 2302.2 μm/mm² at 6, 12, and 24 months after DMEK surgery, respectively. The DC density in BK cornea pre- and postoperatively at 6 months was significantly higher than in the controls, and decreased postoperatively at 12 and 24 months and was significantly lower than that at 6 months postoperatively. Thus, our results suggest that DMEK can repair and normalize the corneal environment.

Characteristics of Corneal Higher-Order Aberrations in Congenital Ectopia Lentis Patients

Purpose

The purpose of this study was to investigate the characteristics of corneal higher-order aberrations (HOAs) in patients with congenital ectopia lentis (CEL).

Methods

Clinical characteristics and HOAs of 60 patients with CEL and 75 healthy controls at Zhongshan Ophthalmic Center in China were retrospectively analyzed. The Q value and the corneal HOAs in the CEL group and the controls were measured by using Pentacam and compared value between the CEL and control groups. The correlation between HOAs and age was investigated using the Pearson correlation analysis.

Results

The Q value of anterior corneal surface in the CEL group was larger than that in the controls (−0.41 ± 0.17 vs. −0.32 ± 0.13, P = 0.001); the total corneal horizontal coma in the CEL group were larger than that in the controls (0.24 ± 0.18 vs. −0.05 ± 0.14, P < 0.001); both the primary spherical aberrations of the anterior and total corneal surface were lower in the CEL group than that in the controls (for anterior corneal surface: 0.15 ± 0.08 vs. 0.27 ± 0.08 µm, P < 0.001; for total corneal surface: 0.10 ± 0.09 vs. 0.23 ± 0.09 µm, P < 0.001), the anterior and total corneal horizontal coma were negatively associated with age, whereas the anterior and total corneal spherical aberrations were positively associated with age in patients with CEL.

Conclusions

Patients with CEL had higher corneal horizontal coma and lower corneal vertical coma primary spherical aberrations than healthy controls.

Translational Relevance

These findings are informative for the clinical managements in patients with CEL.

A Study Validating the Estimation of Anterior Chamber Depth and Iridocorneal Angle with Portable and Non-Portable Slit-Lamp Microscopy

This study assessed the anterior chamber depth (ACD) and iridocorneal angle using a portable smart eye camera (SEC) compared to the conventional slit-lamp microscope and anterior-segment optical coherence tomography (AS-OCT). This retrospective case-control study included 170 eyes from 85 Japanese patients. The correlation between the ACD evaluations conducted with the SEC and conventional slit-lamp was high (r = 0.814). The correlation between the Van-Herick Plus grade obtained using two devices was also high (r = 0.919). A high kappa value was observed for the Van-Herick Plus grading (Kappa = 0.757). A moderate correlation was observed between the ACD measured using AS-OCT and the slit-lamp image acquired with the conventional slit-lamp microscope and SEC (r = 0.609 and 0.641). A strong correlation was observed between the trabecular-iris angle (TIA) measured using AS-OCT and Van-Herick Plus grade obtained with the conventional slit-lamp microscope and SEC (r = 0.702 and 0.764). Strong correlations of ACD evaluation and high kappa value of the Van-Herick Plus grading indicated the adequate subjective assessment function of the SEC. Moderate correlations between the ACD objective measurement and evaluation and strong correlation between the TIA and Van-Herick Plus grade suggested the good objective assessment function of the SEC. The SEC demonstrated adequate performance for ACD evaluation and angle estimation.

Characteristics of corneal high-order aberrations in adolescents with mild to moderate myopia

Background

This study investigated the characteristics of corneal higher-order aberrations (HOAs) of the anterior surface, posterior surface, and total cornea in adolescents with mild to moderate myopia.

Methods

A total of 183 patients with myopia (183 eyes) aged 8 to 18 years were enrolled in this study. The axial length (AL) of the eyes was measured by an IOL-Master, and corneal curvatures (K-values) and HOAs were measured by a Pentacam anterior segment diagnostic analyzer.

Results

Results of this study showed that the anterior, posterior and total corneal horizontal coma Z₃¹ were − 0.1249 ± 0.105 μm, 0.0009 ± 0.001 μm, and − 0.1331 ± 0.116 μm, respectively; the anterior, posterior and total corneal vertical coma Z₃^− 1 were − 0.0212 ± 0.164 μm, 0.0003 ± 0.043 μm, and − 0.0216 ± 0.168 μm, respectively; and spherical aberration (SA) Z₄⁰ values were 0.2244 ± 0.091 μm, 0.1437 ± 0.029 um, and 0.1889 ± 0.090 μm, respectively. Total corneal Z₃¹ was statistically correlated with posterior corneal astigmatism (K₂b − K₁b) (p = 0.038). Total corneal Z₃^− 1 was correlated with anterior corneal astigmatism (K₂f − K₁f) (p = 0.027). Anterior, posterior, and total corneal Z₄⁰ were correlated with anterior and posterior corneal curvature (K₁f, K₂f, K₁b, K₂b) (p = 0.001). Posterior corneal Z₄⁰b was also significantly correlated with AL.

Conclusions

In adolescents with mild to moderate myopia, the posterior corneal surface shape may play a compensatory role in the balance of corneal aberrations, and the posterior corneal SA tended to become less negative as the AL increased. The corneal coma may also play a compensatory role in posterior corneal surface astigmatism, which was valuable for the treatment for improving visual quality. This conclusion still needs to be verified.

Corneal higher-order aberrations in phlyctenular keratitis

PURPOSE

To characterize tomographic patterns and quantify corneal higher-order aberrations (HOAs) in eyes with corneal scar due to phlyctenular keratitis.

STUDY DESIGN

Retrospective consecutive case series.

METHODS

This study included 51 eyes of 38 patients (24 women; 14 men) with corneal scar due to phlyctenular keratitis. HOAs of the total cornea, and of the anterior and posterior surfaces were measured using anterior segment optical coherence tomography (AS-OCT). Corneal tomographic patterns were classified into five types: increased regular astigmatism, ectasia, asymmetric, flattening and minimal change patterns. The correlation between corneal HOAs and visual acuity was evaluated.

RESULTS

Mean months from onset was 50.7 ± 74.7 and mean number of recurrences 2.1 ± 1.1 (1-5). Mean logarithm of the minimal angle of resolution (logMAR) was 0.19 ± 0.31. AS-OCT showed ectasia pattern in 16 eyes (31.4%), asymmetric pattern in 12 eyes (23.5%), increased regular astigmatism pattern in 9 eyes (17.6%), flattening pattern in 3 eyes (5.9%) and minimal change pattern in 11 eyes (21.6%). HOAs of the total cornea were 0.57 ± 0.44 μm and 1.16 ± 0.77 μm within a 4-mm and 6-mm diameter, significantly larger than in normal controls (P < 0.0001). LogMAR visual acuity was significantly correlated with corneal HOAs (4-mm: r = 0.558, P < 0.0001, 6-mm: r = 0.566, P < 0.0001), central corneal thickness (r = - 0.349, P = 0.016), and corneal astigmatism (r = 0.414, P = 0.004), but not with average keratometric value (r = - 0.092, P = 0.537).

CONCLUSIONS

The most common tomographic pattern was ectasia, followed by a asymmetric pattern in eyes with phlyctenular keratitis. Corneal HOAs were associated with decreased visual acuity in phlyctenular keratitis patients.

Quantitative evaluation of visual function in patients with cornea verticillata associated with Fabry disease

PURPOSE

To evaluate the visual function of patients with cornea verticillata associated with Fabry disease through quantitative evaluations of contrast sensitivity function and straylight.

METHODS

We enrolled 28 eyes of 14 patients with Fabry disease (mean age, 37.1 ± 17.2  years) and 20 eyes of 20 age-matched healthy controls. Comprehensive ophthalmological examinations were performed and contrast sensitivity and letter contrast sensitivity were measured for all patients, following which the area under the log contrast sensitivity function (AULCSF) was calculated. Straylight was quantified using a straylight metre. Furthermore, subgroup analysis was performed according to the whorl-like pattern of cornea verticillata (mild and typical groups).

RESULTS

All 28 eyes showed cornea verticillata. Visual acuity and letter contrast sensitivity values were the same for normal eyes and those with Fabry disease. AULCSF differed by 0.15 log[s] between the eyes with Fabry disease and the control eyes (p < 0.001), while straylight differed by 0.45 log[s] between the two groups (p < 0.001). Subgroup analysis based on the whorl-like pattern of cornea verticillata showed that AULCSF and straylight differed by 0.11 log[s] and 0.08 log[s], respectively, between the typical and mild groups (p = 0.036 and p = 0.147, respectively).

CONCLUSION

Although cornea verticillata associated with Fabry disease does not affect the visual acuity and letter contrast sensitivity, more comprehensive testing of visual function by the inclusion of straylight and grating contrast sensitivity measurements shows clear functional deficits in these patients.

Long-term safety of laser in situ keratomileusis in eyes with thin corneas: 5-year follow-up

AIM

To investigate the long term (≥5y) efficacy, predictability, and safety of laser in situ keratomileusis (LASIK) in eyes with thin corneas [central corneal thickness (CCT) <500 µm].

METHODS

A total of 339 patients met the criteria of this study. Finally, 175 eyes of 89 patients who had thin corneas and underwent LASIK≥5y ago returned to our clinic and included in this study. Preoperative parameters recorded included uncorrected visual acuity (UCVA), corrected distance visual acuity (CDVA), manifest refraction, CCT and corneal topography. At returning visits, in addition to visual acuity and manifest refraction, ultrasound CCT and corneal topography were performed. Optical coherence tomography was used to measure the CCT, LASIK flap thickness, and residual stromal bed thickness (RSBT). Safety index, efficacy index, percentage of eyes within ±0.5 D and ±1.0 D of refraction, percent tissue altered (PTA), and percentage stromal bed thickness (PSBT) were calculated.

RESULTS

The safety index was 1.09 and efficacy index was 0.99. The percentages of eyes within ±0.5 D and ±1.0 D were 71.2% and 87.7%, respectively. The mean PTA was 40%±6% (range 20% to 55%); 76 eyes (43.4%) had PTA <40% and 99 eyes (56.6%) had PTA≥40%. The mean RSBT was 303±27 µm (range 240 to 390 µm), and 2 eyes had RSBT<250 µm. The mean PSBT was 61%±9% (range 51% to 85%). No eyes developed ectasia.

CONCLUSION

In this cohort with the PSBT of 50% or more, LASIK is safe with follow-up for at least 5y.