Corneal Densitometry in Healthy Corneas and Its Correlation With Endothelial Morphometry

Comparison of Scheimpflug Corneal Tomography and Anterior Segment Optical Coherence Tomography Measurements in Corneal Cystinosis: A Case Series

PURPOSE

To report the clinical course and compare the utility of Scheimpflug tomography (ST) and anterior segment optical coherence tomography (AS-OCT) for central corneal thickness (CCT) and corneal densitometry (CD) assessment in patients with corneal crystals owing to nephropathic cystinosis.

METHODS

A retrospective chart analysis of three patients with nephropathic cystinosis and the presence of corneal cystine crystals in both eyes was performed. All patients underwent clinical examination and anterior segment photography, ST, and AS-OCT scans. Corneal densitometry was exported from built-in proprietary software for ST and from custom-made validated software for AS-OCT. Anterior segment optical coherence tomography images were rescaled to grayscale units from 0 (maximum transparency) to 100 (minimum transparency) to match built-in ST densitometry readings. Furthermore, the mean pixel intensity, representative of CD, was calculated from the pixels corresponding to the segmented cornea.

RESULTS

All three patients had pathognomonic cystine crystals deposits in the cornea and were treated with cysteamine medications that resulted in clinical improvement. The CCT measured using ST exhibited a range from 560 to 958 μm. Conversely, when assessed with AS-OCT, the CCT varied within the range of 548 to 610 μm. Both examinations could be performed, but in the more severe cases, AS-OCT showed far greater utility to estimate CD. In four of six eyes examined, ST showed disproportionate CCT values, compared with the AS-OCT, whereas reliable CD measurements were only available in AS-OCT.

CONCLUSION

The AS-OCT could be considered a baseline ocular measurement in cystinosis and in the evaluation of disease progression and treatment efficacy.

Assessment by the Scheimpflug imaging system of corneal clarity and anterior segment properties in rosacea patients

OBJECTIVE

To evaluate the effects of rosacea on ocular surface changes such as alterations in dry eye parameters, corneal densitometry, and aberrations, in comparison with healthy controls.

METHODS

A total of 88 eyes of 44 patients diagnosed with rosacea and 88 eyes of 44 healthy controls were enrolled in this cross-sectional study. All participants underwent a comprehensive dermatologic and ophthalmic examination and Tear Break-Up Time (TBUT) and Schirmer-1 tests were performed. The rosacea subtype and Demodex count and OSDI scores of all participants were recorded. Corneal topographic, densitometric, and aberrometric measurements were obtained using the Scheimpflug imaging system.

RESULTS

The mean age of the 44 patients was 41.2 ± 11.0 years of whom 31 (70.5%) were female. The mean TBUT and Schirmer-1 test values were significantly decreased and OSDI scores were significantly increased in the rosacea group compared to healthy controls (p < 0.01 for all). The most common subtype of rosacea was erythematotelangiectatic rosacea (70.4%). The severity grading of rosacea revealed that 18 (40.9%) patients had moderate erythema. The median (min-max) Demodex count was 14.0 (0-120) and the disease duration was 24.0 (5-360) months. The comparison of the corneal densitometry values revealed that the densitometry measurements in all concentric zones, especially in central and posterior zones were higher in rosacea patients. Corneal aberrometric values in the posterior surface were also lower in the rosacea group compared to healthy controls. The topographic anterior chamber values were significantly lower in the rosacea group.

STUDY LIMITATIONS

Relatively small sample size, variable time interval to hospital admission, and lack of follow-up data are among the limitations of the study. Future studies with larger sample sizes may also enlighten the mechanisms of controversial anterior segment findings by evaluating rosacea patients who have uveitis and those who do not.

CONCLUSION

Given the fact that ocular signs may precede cutaneous disease, rosacea is frequently underrecognized by ophthalmologists. Therefore, a comprehensive examination of the ocular surface and assessment of the anterior segment is essential. The main priority of the ophthalmologist is to treat meibomian gland dysfunction and Demodex infection to prevent undesired ocular outcomes.

Corneal densitometry and associated factors in an elderly population

CLINICAL RELEVANCE

Knowing normative corneal optical density (COD) values is important for identifying pathologic corneal changes.

BACKGROUND

The aim of this work is to determine the distribution and associated factors of COD in the elderly population.

METHODS

This report is a part of a cross-sectional population-based study conducted on the elderly population (≥60 years) of Tehran, Iran from Jan 2019 to Jan 2020. Using a multi-stage stratified random cluster sampling method, a total of 160 clusters were randomly selected from 22 districts of Tehran city. Study participants underwent a complete ocular examination including measurement of visual acuity, refraction, and slit-lamp biomicroscopy. Corneal densitometry was evaluated using the Pentacam HR. Generalized estimating equation (GEE) models were used to investigate associations of COD with study variables.

RESULTS

A total of 3633 eyes from 2068 individuals were analysed. Of these, 1256 (60.7%) were female, and the mean age of the individuals was 66.42 ± 5.28 (60 to 95) years. The mean entire COD was 21.96 ± 4.45 greyscale unit (GSU) (95% CI: 21.57-22.34). There was a statistically significant difference in the mean COD between the anterior, central, and posterior layers (p < 0.001); the highest and lowest average COD was related to the anterior and posterior corneal layers, respectively. The lowest and highest mean COD were observed in the 0-2 mm [17.21GSU (95% CI:16.87-17.55)], and 10-12 mm annular zones [31.4 GSU (95% CI: 30.89-31.91)], respectively (p < 0.001). According to the multiple GEE model, the COD had a statistically significant direct relationship with age, central corneal thickness, and mean keratometry, while it was significantly inversely associated with female sex, anterior chamber depth, white-to-white distance, and corneal volume.

CONCLUSION

These normal values of COD in the present study could be used as reference data in older adults. The associated factors of COD should be taken into account to avoid misinterpretation of physiologic changes as pathologic processes.

Crystalline lens clarity in patients treated with isotretinoin

CLINICAL RELEVANCE

Isotretinoin has been the best treatment option for moderate and severe acne vulgaris since the 1980s. Some studies have shown evidence of subclinical anterior segment involvement of the eye in patients treated with isotretinoin.

BACKGROUND

This study aimed to evaluate lens clarity with the densitometry software of Scheimpflug tomography in patients treated with isotretinoin and to compare with healthy control subjects.

METHODS

Thirty-seven acnepatients treated with isotretinoin who met the inclusion criteria (24 males and 13 females, mean age 22.94 ± 4.21 years) and 39 healthy control subjects were included in the study. Clinical characteristics of the isotretinoin and control subjects were recorded. Lens density was evaluated with the densitometry software of the Scheimpflug tomography device (PentacamHR, Oculus, Wetzlar, Germany).

RESULTS

There was no statistically significant difference between the groups in age, gender distribution, spherical equivalent, or anterior segment parameters measured by the Pentacam system (p > 0.05 for all). Lens density values in zones 2 and 3 were significantly higher in the isotretinoin group (p = 0.042, p < 0.001) and positively correlated with cumulative isotretinoin dose (zone 2: r = 0.384, p = 0.032; zone 3: r = 0.384, p = 0.005).

CONCLUSION

Zone 2 and zone 3 lens density are higher in patients treated with isotretinoin when compared to healthy controls.

Corneal densitometry in Chinese adults with healthy corneas: associations with sex, age, ocular metrics, and optical characteristics

BACKGROUND

Standardized corneal densitometry (CD) values in large samples of healthy Chinese individuals are scarce. Therefore, we aimed to determine the standard CD values using a Scheimpflug camera in healthy corneas, investigate the correlations of sex, age, and ocular parameters with corneal density, and explore the impact of corneal density on the forward scattering and optical quality of the eye.

METHODS

This retrospective observational study involved 990 healthy Chinese individuals, including 494 males and 496 females (mean age: 23.88 ± 6.90 years). The CD values at various depths and radial areas of 0-12 mm were measured using a Scheimpflug camera. Densitometric measurements were expressed in standardized grayscale units (GSU). The optical scatter index (OSI), modulation transfer function cutoff values (MTFcutoff), and Strehl's ratio (SR) were also determined using an optical quality analysis system.

RESULTS

The average CD within a 12 mm diameter area was 16.26 ± 1.35 GSU. The highest and lowest optical densities at different depths were observed in the anterior (21.41 ± 2.16 GSU) and posterior (12.00 ± 1.01 GSU) layers, respectively (P < 0.001). Similarly, the maximum and minimum optical densities at different radial areas were observed in the 10-12 mm (14.09 ± 0.93 GSU) and 2-6 mm (25.93 ± 4.77 GSU) circles, respectively (P < 0.001). There was no significant difference in the average CD within a 12 mm diameter area between males and females (P > 0.05). However, upon adjusting for age, central corneal thickness (CCT), corneal curvature, white-to-white (WTW) corneal diameter, and axial length, females exhibited a greater average CD within the 12 mm diameter and in the 6-10 mm and 10-12 mm circles than males. Age-related changes in CD were evident, except in the 2-6 mm circle. CCT, corneal curvature, WTW corneal diameter, and partial depth correlated with CD in the radial area, and CD in different areas correlated with the OSI, MTFcutoff, and SR (P < 0.05).

CONCLUSIONS

This study provides the normative CD measurement data of Chinese adults with healthy corneas, emphasizing the significance of sex, age, CCT, corneal curvature, and WTW corneal diameter in CD evaluation. Notably, elevated CD can lead to increased forward scattering within the eye, thereby affecting the optical quality.

Biometric and corneal characteristics in marfan syndrome with ectopia lentis

PURPOSE

To describe the biometric and corneal characteristics of patients with Marfan Syndrome (MFS) and ectopia lentis.

STUDY DESIGN

Observational, descriptive, prospective study. Subjects Individuals with MFS with ectopia lentis (EL).

METHODS

Fourty-four eyes of 23 patients underwent Scheimpflug analysis using the Pentacam (Oculus, Wetzlar, Germany), axial length (AL) using the IOL master 700 (Carl Zeiss AG, Oberkochen, Germany), endothelial cell count (ECC) using the CEM-350 (NIDEK, Maihama, Japan) and corneal biomechanics evaluation with the Ocular Response Analyzer: ORA (Reichert Ophthalmic Instruments, Buffalo, New York, USA) and Corvis (Oculus, Wetzlar, Germany). Statistical analysis was performed using IBM SPSS Statistics 25.0.

RESULTS

The direction of lens subluxation was most frequently supero-nasal 40.9% (18/44). Mean keratometry (Km) was 40.22±1.76 Diopters (D); mean corneal astigmatism was 1.68±0.83 D; total corneal aberrometric root mean square (RMS) was 2.237±0.795μm; higher-order aberrations (HOAs) RMS were 0.576±0.272μm; mean AL was 25.63±3.65mm; mean ECC was 3315±459cell/mm2; mean CBI was 0.13±0.24, mean TBI was 0.31±0.25, mean posterior elevation was 4.3±4.5μm; mean total corneal densitometry was 16.0±2.14 grayscale units (GSU).

CONCLUSION

Increased axial length, flatter and thicker corneas with higher regular astigmatism, normal densitometry, normal corneal biomechanical indices and normal posterior elevation were observed in Marfan patients with EL.

The comparison of corneal densitometry in cases with glaucoma following childhood cataract surgery and juvenile glaucoma

PURPOSE

To compare the corneal densitometry (CD) in pediatric cases with glaucoma following childhood cataract surgery and juvenile open-angle glaucoma (JOAG).

METHODS

This prospective comparative study involved 13 eyes with JOAG, 12 eyes with pseudophakic glaucoma, 13 eyes with aphakic glaucoma, and 15 control subjects. Pentacam HR Scheimpflug corneal topography was employed to evaluate corneal thickness (CCT) and CD values.

RESULTS

The mean intraocular pressure (IOP) and CCT were significantly higher in aphakic glaucoma cases than the other groups (p = 0.001). In aphakic eyes, the mean CD values were higher in most of the anterior, center, and posterior layers of 0-2 mm, 2-6 mm, 6-10 mm, and total zones (p < 0.001 for all). In pseudophakic eyes, the mean CD values were statistically similar with that of aphakic eyes and higher than that of JOAG and control eyes in all layers of 0-2 mm zone and in anterior layer of 10-12 mm and anterior and total layers of 2-6 mm zones (p < 0.05 for all). The CD values demonstrated significant correlations with CCT values in both aphakic and pseudophakic eyes. However, a significant correlation of CD values with IOP was only demonstrated in aphakic eyes (p = 0.01 for all).

CONCLUSION

The probable effects of childhood cataract surgery especially aphakia might cause corneal backscatter of light and increased CD in all layers in all zones of the cornea. Increased CD values and its correlation with CCT and IOP in aphakic glaucoma eyes may be of importance in clinical management.

The outcomes of postoperative eye patching after cataract surgery in patients with Fuchs' endothelial corneal dystrophy

PURPOSE

To investigate the influence of post-operative eye patching on corneal thickness, endothelial cells' loss and visual acuity in patients diagnosed Fuchs' endothelial corneal dystrophy (FECD).

SETTING

Public healthcare centre, Shamir Medical Centre, Israel.

METHODS

This randomized controlled trial included patients with FECD undergoing routine cataract surgery in a public medical centre. Patients were randomly assigned to 2 groups: the eye undergoing surgery was covered with a patch for 24 h in the first group (patched group), and a plastic shield was used in the second (non-patched group). Both groups received a unique dose of a local steroid and antibiotic post-operatively. The eyes were examined pre-operatively, and on days 1, 7 and 30 post-surgery . Examination included: best corrected visual acuity (BCVA), comeplete slit lamp examination, intra ocular pressure (IOP), anterior chamber depth (ACD), central corneal thickness (CCT) using the IOL Master 700 (Zeiss, Germany) and endothelial cell density (ECD) using Specular microscopy. Cumulative dissipated energy (CDE) and operation time were recorded for all cases.

RESULTS

The study included 46 eyes of 46 patients diagnosed with FECD. Twenty-three eyes in the patched group, and 23 eyes in the non-patched group . Thirty days post-operatively the CCT in the patched group decreased by 60 ± 38 mµ (9%) compared to 92 ± 80 mµ (13.5%) in the non- patched group (p = 0.04). Seven days post-operatively the CCT in the patched group decreased by 31 ± 35 mµ (5%) compared to 58 ± 76 (8%) in the non-patched group, but this difference did not reach statistical significance (p = 0.081). There was no statistically significant difference in endothelial cells loss as well as BCVA at 1, 7 and 30 days post-operatively between the study groups.

CONCLUSIONS

Avoiding eye patch post-operatively after cataract surgery in patients with FECD results in better corneal clarity recovery and reduced corneal edema one month post-operatively. Visual acuity and endothelial cell's loss were not influenced by patching.

Effect of smoking on corneal and lens clarity: a densitometric analysis

PURPOSE

To assess the effect of chronic cigarette smoking on corneal and lens densitometry measurements using Pentacam HR and to compare the results obtained with those in non-smokers.

MATERIALS AND METHODS

This cross-sectional comparative study included 40 chronic-smokers and 40 age-matched healthy non-smokers between 18-40 years. After general ophthalmic examination, the Pentacam HR imaging system was used to evaluate corneal and lens densitometry measurements of smokers and non-smokers.

RESULTS

The mean corneal densitometry values were not statistically significantly different in all the concentric zones and layers in the eyes of the smokers and non-smokers (p > 0.05, for all). However, the mean values of zone 1, zone 2, zone 3 and average lens densitometry measurements of the smokers were statistically significantly higher compared to non-smokers (p < 0.05, for all). Additionally, significant positive correlations were detected between the number of pack-years smoked and lens densitometry measurements.

CONCLUSION

Lens densitometry measurements of smokers were significantly increased while corneal densitometry measurements were not significantly altered compared to non-smokers. Smoking may contribute to cataractogenesis and smoking and age-related changes may act synergistically to cataract development among smokers.

Scheimpflug Corneal Densitometry Patterns at the Graft-Host Interface in DMEK and DSAEK: A 12-Month Longitudinal Comparative Study

BACKGROUND

To compare corneal densitometry (CD) patterns at the graft-host interface between Descemet Membrane Endothelial Keratoplasty (DMEK) and Descemet Stripping Automated Endothelial Keratoplasty (DSAEK). Corneal densitometry is a quantitative assessment that objectively evaluates corneal clarity and optical quality by measuring the light backscatter from the cornea.

METHODS

Fifty-one eyes that received DMEK or DSAEK surgery for corneal endothelium dysfunction were evaluated. The primary endpoint included CD patterns at the graft-host interface, which were assessed by the Pentacam HR device at the center point of the corneal horizontal meridian (CDcentral), and at six points on the central circumference of the cornea (with a total diameter of 4 mm) (CDI,II,III,IV,V,VI). Secondary endpoints included the best-corrected distance visual acuity (BCDVA), central corneal thickness (CCT), and graft thickness (GT). All of the evaluations were performed at follow-up appointments one, three, six and twelve months after the procedure.

RESULTS

DMEK showed a significant overall CD reduction of -7.9 ± 8.5 grayscale unit (GSU) compared to DSAEK (p < 0.001). In addition, the DMEK group showed significantly lower CDCentral,I,II,III,IV,V,VI values at follow-up appointments one, three, six and twelve months after the procedure compared to the DSAEK group (p < 0.001). BCDVA, CCT and GT were in favor of the DMEK group with a mean value of 0.39 ± 0.35 LogMar, 552.2 ± 71.1 µm and 11.03 ± 1.4 µm, respectively (p < 0.001).

CONCLUSIONS

CD patterns at the graft-host interface seem to be different depending on the endothelial keratoplasty procedure. This provides specific insight into CD changes in this critical region of surgery, which may provide a better understanding of the postoperative evolution of these patients.

Corneal optical density: Structural basis, measurements, influencing factors, and roles in refractive surgery

The cornea is the main refractive medium of the human eye, and its clarity is critical to visual acuity. Corneal optical density (COD) is an important index to describe corneal transparency. Intact corneal epithelial and endothelial cells, regular arrangement of collagen fibers in the stroma, and normal substance metabolism are all integral for the cornea to maintain its transparency. In the last two decades, the Pentacam Scheimpflug imaging system has emerged as a breakthrough for the measurement of COD (also called corneal densitometry). It has been found that a wide variety of factors such as age, refractive status, and corneal diseases can affect COD. Different corneal refractive surgery methods also change COD in different corneal regions and layers and affect visual acuity following the surgery. Thus, COD has gradually become a significant indicator to evaluate corneal health, one on which the attention of clinicians has been increasingly focused.

Corneal densitometry: an innovative method to quantitatively evaluate corneal changes after phacovitrectomy

BACKGROUND

To quantitatively investigate corneal changes and the correlation between corneal densitometry (CD) and endothelial parameters after phacovitrectomy.

METHODS

Thirty-eight eyes with idiopathic full-thickness macular holes (iFTMHs) and cataracts underwent phacovitrectomy. Examinations were conducted at baseline and Day 1, Day 7, Month 1, and Month 3 postoperatively. CD and central corneal thickness (CCT) were measured using Pentacam. Corneal endothelial cell density (ECD), coefficient of variation (CV), and hexagonality (HEX) were measured using specular microscopy.

RESULTS

ECD and HEX significantly decreased after surgery and the change in HEX occurred prior to CV. CCT increased immediately after surgery and recovered 3 months postoperatively. CD values increased significantly 1 day after surgery and then gradually decreased. For CD in the 0-2 mm zone, it took 1 month to recover in the central and posterior layers and 3 months in the anterior and total layers. For CD in the 2-6 mm zone, the central layer recovered at Day 7, the anterior and total layers recovered at 1 month, and the posterior layer did not recover until 3 months postoperatively. The CD within all layers in the 0-2 mm zone was positively correlated with CCT. Posterior CD in the 0-2 mm zone was negatively correlated with ECD and HEX.

CONCLUSIONS

CD is not only correlated with CCT, ECD, and HEX but also reflects the state of the whole cornea and each layer. CD can be an objective, rapid, and noninvasive tool that reflects corneal health and undetectable edema and monitors the process of lesion repair.

TRIAL REGISTRATION

This study was registered with the Chinese Clinical Trial Registry (31/10/2021, ChiCTR2100052554).

Analysis of corneal topographic and densitometric properties in patients receiving systemic isotretinoin therapy

PURPOSE

To evaluate dry eye parameters, corneal topographic features, corneal densitometric changes, and anterior segment parameters in patients receiving systemic isotretinoin treatment.

METHODS

This prospective cross-sectional study included 66 eyes of 33 patients who were started on oral isotretinoin therapy for severe acne vulgaris. All patients were evaluated in terms of ocular surface tests such as tear break-up time (TBUT) and Schirmer-1 and were asked to fill in the ocular surface disease index (OSDI) questionnaire. Corneal densitometric and topographic measurements were obtained using the Scheimpflug imaging system.

RESULTS

The mean age of the patients was 19.9 ± 1.6 years, and 21 (63.6%) of the participants were female. The mean OSDI score was significantly higher in the third month than before treatment (20.05 ± 19.38, vs. 26.96 ± 22.94, p = 0.00, respectively). The mean values of the TBUT test were significantly lower in the third month than before treatment (9.06 ± 4.40 sec, vs. 10.71 ± 4.61 sec, p = 0.02, respectively). Mean scores of the Schirmer 1 test showed no statistically significant difference between before treatment and the third month (16.08 ± 8.40 mm, vs. 16.08 ± 8.50 mm, p = 1, respectively). There was no statistically significant difference between before treatment and the third month in the majority of the densitometry measurements in concentric zones. However, the difference tended to be significant between the groups concerning posterior zone 0-2 mm (11.01 ± 0.85 GSU vs. 10.62 ± 0.89 GSU, p = 0.006). The RMS LOAs (front), RMS Total (Total), RMS LOAs Total (Total), RMS HOAs Total (Total), K_max, CCT, and CoV values were significantly higher in the third month than before treatment (p < 0.05 for all).

CONCLUSIONS

The dermatology specialists should be aware of the ocular complications of systemic isotretinoin therapy. Therefore, a complete ophthalmologic examination for the prompt apprehension and management of ocular involvement is essential in patients under isotretinoin therapy to increase ocular comfort and adherence to the therapy.

Comparison of Corneal Densitometry and Visual Quality after Small Incision Lenticule Extraction (SMILE) and Laser Epithelial Keratomileusis (LASEK): One-Year Comparative Study

Purpose

To investigate changes in corneal densitometry (CD) and visual quality following small incision lenticule extraction (SMILE) and laser epithelial keratomileusis (LASEK) in patients with mild-to-moderate myopia.

Methods

A retrospective analysis was performed on 24 and 25 patients (46 eyes each) who underwent SMILE and LASEK, respectively, for mild-to-moderate myopia. The visual quality and CD values were recorded. Using the Pentacam Scheimpflug system, CD values were collected in three concentric optical zones at the depths of the anterior, central, and posterior layers. Efficacy, safety, predictability, corneal wavefront aberrations, and QoV scores were measured to evaluate visual quality. A correlation analysis was performed between changes in CD and clinical characteristics.

Results

There were no statistical differences in efficacy and safety indices between the two groups. At 3 months postoperatively, a pronounced reduction in several zones was observed in the LASEK group (p < 0.05), whereas no obvious change was observed in the SMILE group. There were obvious changes in the CD values in several zones in the SMILE and LASEK groups (p < 0.05) after 1 year. The magnitude of the CD changes in the anterior and central corneal layers was smaller in the SMILE group than in the LASEK group (all p < 0.05). Lower HOAs, spherical aberration, and horizontal comas of the anterior and whole corneal surfaces were observed in the SMILE group. QoV scores were similar between the two groups.

Conclusion

CD decreased in the SMILE and LASEK groups after 1 year; there was a smaller reduction in SMILE than in LASEK. SMILE and LASEK did not differ significantly in terms of safety and effectiveness in correcting mild-to-moderate myopia.

Changes in corneal thickness, corneal volume, and densitometry after long-term orthokeratology wear

PURPOSE

To investigate changes in the corneal volume, corneal densitometry and pachymetry of young myopes wearing over-night orthokeratology (OK) contact lenses.

METHODS

The medical records of 28 right eyes of young myopes wearing OK between 2013 and 2018 were reviewed retrospectively. The baseline refractive error, best corrected visual acuities at baseline and uncorrected visual acuity at the most recent visit were recorded. Corneal volume of the central 10 mm cornea; densitometry at central, nasal and temporal cornea; and pachymetry along the horizontal and vertical meridians were collected from the Pentacam® HR at baseline, after one night of lens wear, and at the latest visit.

RESULTS

The mean age of subjects was 12.03 ± 3.80 years at the time of OK lens fitting and wore OK overnight for a mean duration of 666 days (range 206-1736 days). The baseline spherical equivalent refractive error was -3.03 ± 1.56 D (range -1.00 to -6.00 D). The corneal volume increased significantly after OK wear (p = 0.001). Corneal densitometry increased after OK wear, but the change did not reach statistical significance (p = 0.113). Pachymetry in the central cornea did not change significantly across all visits (p > 0.05) but increased significantly in the mid-peripheral regions of the cornea. Baseline refractive error was not found to be correlated with the changes in corneal volume, corneal densitometry, or pachymetry.

CONCLUSION

The increase in corneal volume and densitometry and no significant change in the central corneal thickness may indicate the presence of corneal oedema from long-term OK wear. The baseline refraction was not correlated with the changes in corneal volume, densitometry or pachymetry.

In vivo confocal microscopy of sub-basal corneal nerves and corneal densitometry after three kinds of refractive procedures for high myopia

PURPOSE

To observe corneal nerve fibers and densitometry after small incision lenticule extraction (SMILE), femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK) and laser-assisted subepithelial keratomileusis (LASEK) for high myopia.

METHODS

This is a prospective, cross-sectional research study. Patients with high myopia (equivalent spherical lens: -6.00 and -11.00D) who underwent laser corneal refractive surgery were divided into three groups: SMILE, FS-LASIK and LASEK. Scheimpflug imaging of corneal nerves in five areas was observed by confocal microscopy before and 6, 12 months after surgery. Corneal densitometry was measured by Pentacam anterior segment analysis system.

RESULTS

Overall, 59 patients were enrolled. The nerve density in the central area did not recover to the preoperative level in three groups until 12 months. The density and length of corneal nerves in central and lower area were better in the SMILE group 6 months postoperatively (p = 0.01), while nerve density did not differ significantly among three groups 12 months postoperatively (p = 0.18). Nerve fibers in central and temporal region were wider in LASEK than that in other two groups at 6- and 12-month follow-up. Corneal densitometry in the central 6 mm diameter was significantly higher in the LASEK group compared with other two groups 6 months postoperatively (p = 0.04). Twelve months postoperatively, corneal densitometry in range of all zone was lower in SMILE than in FS-LASIK and LASEK (p = 0.01, 0.03, 0.04).

CONCLUSIONS

Compared with FS-LASIK and LASEK, SMILE-treated eyes with high myopia had certain advantages in nerve density, length and nerve connection way and had better corneal transparency after operation.

Scheimpflug Corneal Densitometry Values and Severity of Guttae in Relation to Visual Acuity in Fuchs Endothelial Corneal Dystrophy

PURPOSE

The purpose of this study was to investigate the association between corneal densitometry (CD) values from Scheimpflug tomography imaging, severity of guttae, and visual acuity in eyes with Fuchs endothelial corneal dystrophy (FECD).

METHODS

This was a retrospective, cross-sectional study. Patients with FECD were examined at the Bascom Palmer Eye Institute from January 2015 to September 2019. We extracted CD values at central annuli of 0-2, 2-6, 6-10 and 10-12 mm from Scheimpflug tomography images. We investigated the association of corrected distance visual acuity (CDVA) with CD values, severity of guttae, central corneal thickness (CCT), cataract grade, refractive error, corneal edema grade, age, and gender using multivariate generalized estimating equation regression models.

RESULTS

One hundred ninety-two eyes from 110 patients were included in this study. Increase in central CD values at the 0 to 2 mm zone (P < 0.001), severity of guttae (P = 0.046), age (P < 0.001), cataract grade (P < 0.001), corneal edema grade (P < 0.001), and type of refractive error (P = 0.008) were significantly associated with decreased CDVA. Central corneal thickness, sex, and the peripheral CD values (2-6, 6-10, and 10-12 mm) were not significantly associated with CDVA (P > 0.05) in the final multivariate regression model.

CONCLUSIONS

Our study demonstrates that central CD values at 0 to 2 mm and severity of guttae are each associated with decreased CDVA in FECD. These findings carry implications for patients with FECD considering surgical intervention for phacoemulsification alone, Descemet stripping only, or endothelial cell transplantation and provide a multifactorial perspective on vision loss in FECD.

Assessment of Corneal Densitometry in Big-Bubble Dissection Versus Manual Dissection Deep Anterior Lamellar Keratoplasty

PURPOSE

The aim of this study was to assess corneal densitometry and visual outcomes after big-bubble deep anterior lamellar keratoplasty (BB-DALK) and manual dissection deep anterior lamellar keratoplasty in patients with keratoconus.

METHODS

This retrospective comparative observational study included 40 keratoconic patients who underwent DALK surgery: 22 eyes had BB-DALK (group I) and 18 eyes had failed BB technique and DALK was completed by manual dissection (group II). Best -corrected visual acuity (BCVA), corneal topographic parameters, residual stromal tissue thickness, and endothelial cell count were recorded at 1, 3, 6, and 12 months postoperatively. Densitometric analysis of different corneal layers and zones was performed using Scheimpflug tomography at each visit; values were recorded and compared between the 2 groups.

RESULTS

At 1 and 6 months postoperatively, BCVA was better in group I than in group II, but with no statistically significant difference. At 12 months, the visual acuities became nearly similar in both groups (0.30 ± 0.13 vs. 0.30 ± 0.14 logarithm of the minimum angle of resolution, P = 0.888). Regarding corneal densitometric analysis, the recorded values for the posterior corneal layer were significantly higher in group II compared with group I at 3, 6, 9, and 12 months postoperatively in the 0- to 2-mm zone (P < 0.001) and the 2- to 6-mm zone (P = 0.029, 0.028, 0.001, and <0.001).

CONCLUSIONS

Manual dissection DALK after failed BB technique may affect the interface stromal reflectivity up to 12 months postoperatively. However, this does not significantly affect the visual acuity in comparison with successful BB-DALK.

Visual Corneal Photomechanical Analysis Is Combined with the Pentacam Correlation Index for the Diagnosis of Cone Corneas at Different Stages of Progression

Cone-shaped corneas are blinding eye diseases characterised by dilated and thinning corneal tissue and forward conical protrusions, most often in adolescents. Early detection and intervention can prevent further dilatation of the cornea. The prevailing examination methods and techniques are not difficult to diagnose clinical cone corneas, but there are limitations in the diagnosis of early cone corneas (static cone corneas and subclinical cone corneas). In this study, we investigated the diagnostic value of the combination of these two instruments in the diagnosis of clinical cone corneas and subclinical cone corneas by performing the Pentacam and Corvis ST examinations in healthy eyes and dystrophic cone corneas. This study provides a theoretical basis for early cone cornea screening and diagnosis. The analysis revealed that only TP, SPA1, ARTh, and bIOP were normally distributed among all included parameters, and only bIOP was normally distributed with equal variance. TBI and CBI indices have a certain sensitivity and specificity for the diagnosis of subclinical cone corneas, with a strong diagnostic ability, and can be used for screening and early diagnosis of cone corneas.

Changes in corneal densitometry after long-term orthokeratology for myopia and short-term discontinuation

Purpose

To quantify changes in corneal densitometry after long-term orthokeratology treatment in myopic children and to analyze the reversibility one month after discontinuation.

Methods

Seventy-four myopic subjects aged 8–16 years, who wore orthokeratology lenses for two years, were divided into relatively steep- (lens movement within 1.0–1.5 mm, thirty-six participants) and flat-fitting groups (lens movement within 1.5–2.0 mm, thirty-eight participants). Based on refractive errors, they were divided into low and moderate myopia groups (thirty-seven participants in each group). Corneal densitometry was performed using Pentacam (Oculus Optikgeräte GmbH, Wetzlar, Germany) at each follow-up timepoint. Repeated-measures analysis of variance was used to compare the parameters before and after orthokeratology.

Results

The corneal densitometry values over the 0–10 mm diameter area increased from 12.84±1.38 grayscale units (GSU) at baseline to 13.59±1.42 GSU after three-month orthokeratology (P = .001) and reached 14.92±1.45 GSU at two years (P < .001). An increase in densitometry began at one month (P = .001) over the 0–2 mm annulus compared with that at three months over the 2–6 mm and 6–10 mm zones (P = .002,.014). The densitometry values significantly increased at three months in the relatively steep-fitting group (P = .003) and at one year in the relatively flat-fitting group (P = .001). After discontinuation of orthokeratology for one month, the values showed no significant decrease.

Conclusions

Long-term orthokeratology treatment causes a small but statistically significant increase in corneal densitometry values. During the first year, the onset of these changes was related to the fitting mode. Corneal densitometry values showed no significant reduction after one-month discontinuation.

Potential Factors of Corneal Endothelial Cells for Progression in Children with Uveitis

Objective

To observe the morphological changes and abnormal structure of corneal endothelial cells in children with uveitis, to analyze the related factors affecting the morphological changes of corneal endothelial cells, and to explore the clinical application of a corneal endothelial microscope in children with uveitis.

Methods

The corneal endothelial cells of 70 patients with uveitis were photographed with the Topcon SP-3000 noncontact corneal endothelial microscope, and the corneal endothelial cell density (CD), average cell area (AVE), coefficient of variation of the cell area (CV), and percentage of hexagonal cells (PHC) were measured with the IMAGEnet system. Twenty-eight patients (56 eyes) with monocular uveitis were selected, with the affected eyes (28 eyes) as the experimental group and the contralateral healthy eyes (28 eyes) as the control group. The corneal endothelial cell parameters between the two groups were statistically analyzed. The parameters of corneal endothelial cells in 70 children with uveitis were compared, and the effects of the course of the disease, inflammatory cells in the anterior chamber, and posterior corneal deposition (KP) on the parameters of corneal endothelial cells were analyzed.

Results

There are four abnormal forms of the corneal endothelium in children with uveitis: enlarged cell area gap, irregular cell shape, blurred intercellular space, and cell loss. KP showed irregular high reflective white spots in the corneal endothelial microscope images, surrounded by dark areas, and existed in all the eyes with dusty KP found in slit lamp examination and a small number of eyes without obvious KP. Comparing the corneal endothelial cell parameters between the experimental group and the control group, it was found that the corneal endothelial CD and PHC of the former were lower than those of the latter, and the difference was statistically significant (P < 0.001 and P = 0.018, respectively). The AVE and CA of the former were higher than those of the latter (P = 0.013 and P = 0.046, respectively). The corneal endothelial cell density of the eyes with a course of the disease of more than 1 year was lower than that of the eyes with a course of the disease less than 1 year, the coefficient of variation of the corneal endothelial cell area of the eyes with KP was higher than that of the eyes without KP, and the difference was statistically significant (P = 0.003 and P = 0.030, respectively).

Conclusion

Corneal endothelial microscopy is one of the important methods for the detection of uveitis with high sensitivity. The change of morphological parameters of corneal endothelial cells is one of the important indexes to assist in the diagnosis of uveitis and can be further promoted in ophthalmological examination.

Corneal Densitometry Assessed With Scheimpflug Camera in Healthy Corneas and Correlation With Specular Microscopy Values and Age

PURPOSE

To investigate correlations between specular microscopy endothelial parameters and age with corneal densitometry values, as they are presented from a Scheimpflug device, in different levels of the cornea.

METHODS

Two hundred eighty-four eyes of 142 healthy subjects were included in this observational, prospective study. Corneal densitometry was evaluated with Scheimpflug imaging system in the central 0- to 2-mm annular zone of the cornea, whereas the endothelial cell properties were assessed with the use of a noncontact specular microscope.

RESULTS

Corneal densitometry values of all corneal layers were statistically significant and positively correlated with age. In univariate linear regression analysis among corneal densitometry values and the endothelial parameters, only endothelial cell density (CD) was statistically significant and inversely correlated with densitometry values in all corneal layers. In stepwise multivariate linear regression analysis, after adjustment for age, hexagonality was statistically significant and inversely correlated with posterior densitometry values, whereas coefficient of variation was positively and significantly correlated with the anterior densitometry values. When repeating stepwise multivariate linear regression analysis without adjusting for age, CD was negatively and significantly correlated with corneal densitometry values of all layers, whereas coefficient of variation was positively and significantly correlated with anterior and total corneal densitometry values.

CONCLUSIONS

Corneal densitometry increases with age. It is also inversely correlated with CD, and this might be used as an indirect way to assess the status of the corneal endothelium.

Safety of EVO ICL Implantation With an Ophthalmic Viscosurgical Device-Free Technique in the Early 24 h After Surgery

Purpose: To compare the safety of the non-ophthalmic viscosurgical device (OVD) technique with that of the minimum OVD technique in EVO Implantable Collamer Lens (EVO-ICL) implantation.

Methods: A total of 180 eyes of 90 consecutive patients were enrolled in the study, of which 100 eyes of 50 patients were treated with non-OVD technique, with a 55% success rate. The remaining 80 eyes of 40 patients were treated with min-OVD technique, so they were classified into the min-OVD group. Preoperative and postoperative intraocular pressure (IOP) measurements were collected and analyzed at 1, 2, 3, and 24 h. Visual acuity, corneal endothelial cell density (ECD), and corneal densitometry 24 h postoperatively were evaluated.

Results: No significant difference was found in visual outcomes (P = 0.54) or ECD (P = 0.78) between the two groups. The operation time was significantly shorter in the non-OVD group (P < 0.0001). The IOP was significantly higher at 1 h (P < 0.0001), 2 h (P < 0.0001) and 3 h (P = 0.0045) postoperatively in the min-OVD group. The non-OVD group had significantly lower IOP than the min-OVD group at 1 h (P = 0.01) and 2 h (P = 0.013) postoperatively. The temporal corneal densitometry in the non-OVD group were significantly lower than those in the minimum group (P = 0.0063) 1 day after surgery.

Conclusion: The non-OVD technique is safe and efficient for ICL implantation. It can be a safer method of ICL implantation in that it completely eliminates ophthalmic viscoelastic devices related complications without causing additional complications in short term.

Ascorbic acid ameliorates corneal endothelial dysfunction and enhances cell proliferation via the noncanonical GLUT1-ERK axis

BACKGROUND

The pumping function of corneal endothelial cells (CECs) plays a pivotal role in the maintenance of corneal water homeostasis. Corneal endothelial dysfunction (CED) leads to corneal edema and opacity, but with the exception of keratoplasty, no optimal therapeutic strategies have been established for CED. In this study, we aimed to investigate the ameliorative effect of ascorbic acid (AA) on CED and the underlying mechanism of action in the corneal endothelium.

METHODS

Rabbit corneal endothelial damage was induced by anterior chamber injection of benzalkonium chloride (BAK). AA was topically administered to the corneal surface, and the transparency and thickness of the cornea were assessed by external eye photography, slit-lamp photography, and ultrasonic pachymetry. To further analyze the mechanism, rabbit CECs and immortalized human CECs (B4G12 cells) were cultured. A ferric reducing/antioxidant and AA (FRASC) assay was performed to measure the AA concentration. Cell proliferation was evaluated by cell counting and bromodeoxyuridine (BrdU) labeling assays, and protein expression was examined by liquid chromatography-mass spectrometry (LC/MS) and immunoblotting. The involvement of glucose transporter 1 (GLUT1) and phospho-ERK was evaluated via GLUT1-siRNA and phospho-ERK inhibitor (PD98059) treatment.

INTERPRETATION

We observed that topical AA ameliorates BAK-induced rabbit corneal endothelial damage. Furthermore, we demonstrated that AA is transported into B4G12 cells via GLUT1, and afterward, AA increases ERK phosphorylation and promotes cell proliferation. Our findings indicate that CEC proliferation stimulated via the noncanonical AA-GLUT1-ERK axis contributes to AA-enhanced healing of CED.

One-step viscoelastic agent technique for ICL V4c implantation for myopia

AIM

To investigate the safety and efficacy of using a one-step viscoelastic agent technique for posterior chamber phakic implantable collamer lens with a central hole (ICL V4c) implantation for myopia correction.

METHODS

The one-step viscoelastic agent technique for ICL V4c implantation was used in 100 eyes of 52 patients. Refractive outcomes, intraocular pressure (IOP), corneal endothelial cell, and corneal densitometry values were evaluated at 1d, 1wk, 1 and 3mo postoperatively.

RESULTS

All the surgeries were uneventful. No corrected distance visual acuity was lost after 3mo. IOP was 16.12±3.18 mm Hg before surgery, and 14.74±3.08 mm Hg at 1d and 14.50±2.56 mm Hg at 3mo after surgery (P<0.05). Corneal endothelial cell density was 2580±242 cell/mm², the coefficient of variation in cell size was 42.11%±7.92%, and the percentage of hexagonal cells was 40.98%±9.46% before surgery. No significant difference was found when these outcomes were compared between the studied time points (P>0.05). The corneal densitometry values of the central 2 mm and 2 to 6 mm areas showed similar regularities. After surgery, the values significantly increased at 1d, then decreased to the preoperative values at 1wk, and then continued to decrease at 3mo (P<0.05).

CONCLUSION

The one-step viscoelastic agent technique for ICL V4c implantation is found to be safe and effective for myopia correction and causes little disturbance to the cornea.

Analysis of corneal densitometry and endothelial morphometry in patients with psoriasis

BACKGROUND

To evaluate corneal endothelial properties and corneal densitometry values in patients with psoriasis and to compare the results with those of healthy controls.

METHODS

This prospective, comparative, and cross-sectional study included 106 eyes of 53 patients who were diagnosed with psoriasis and 106 eyes of 53 age-gender matched healthy controls. All patients were evaluated in terms of ocular surface tests such as Schirmer-1 and tear break-up time (TBUT). Corneal endothelial measurements were performed using noncontact specular microscopy. Corneal tomographic and densitometric measurements were obtained using the Scheimpflug imaging system. Measurements were also evaluated according to the psoriasis area and severity index (PASI) score.

RESULTS

The mean TBUT and Schirmer 1 test values were significantly lower in the psoriasis group than in the healthy controls (p = 0.02, p < 0.001, respectively). While the mean endothelial cell density was significantly lower in patients with psoriasis than the healthy controls (2389.9±314.9 cells/mm² vs. 2512.4±289.7 cells/mm², p = 0.02), the mean average endothelial cell area, standard deviation of cell area, coefficient of variation of cell area were significantly higher in patients with psoriasis (426.6±62.7 µm² vs. 403.2±46.1 µm², p = 0.01; 206.4±52.3 µm² vs. 183.2±43.8 µm², p = 0.006; and 48.1±6.3% vs. 45.7±6.7%, p = 0.04, respectively). Most of the densitometry measurements in concentric zones were higher in patients with psoriasis than in healthy controls, but none of the differences reached statistical significance.

CONCLUSIONS

A regular eye examination is crucial in patients with psoriasis because corneal structural and functional changes, particularly endothelial alterations, are of utmost importance in planning intraocular surgeries in patients with psoriasis.

New algorithm for corneal densitometry assessment based on anterior segment optical coherence tomography

PURPOSE

To describe a new algorithm to measure corneal densitometry based on images obtained by swept source anterior segment ocular coherence tomography (SS-AS-OCT) and establish standard densitometry values in a group of normal eyes.

METHODS

A total of 111 healthy participants (195 eyes) were enrolled in this study. Using a MATLAB designed algorithm, the cornea was segmented into three layers: anterior, posterior and mid-stroma, and it was divided into two concentric areas, 0-2 and 2-4 mm, resulting in nine areas for the analysis. The mean corneal densitometry values were calculated and expressed as grayscale units (GSU).

RESULTS

The mean age was 57 years (range 22-87), with 100 (51.3%) right eyes and 95 (48.7%) left eyes. The total corneal densitometry was 86.9 ± 12.1 GSU. The mid-stroma layer had the highest densitometry values, 87.4 ± 12.1 GSU, and the anterior layer had the lowest values, 81.9 ± 14.2 GSU. Densitometry differences between the anterior layer and the mid-stroma layer (P < 0.001), as well as the anterior layer and the posterior layer (P < 0.05) were statistically significant. The 0-2 mm concentric area had higher mean densitometry values, 97.8 ± 12.7 GSU, and the differences were significant compared to the 2-4 mm concentric area (P < 0.001). No correlation was found between the corneal densitometry values and gender or age.

CONCLUSIONS

The new MATLAB segmentation algorithm for the analysis of corneal SS-AS-OCT images is capable to objectively assess corneal densitometry. We provide standard and normal data for better clinical and research approach.

Evaluation of corneal densitometry changes in patients with lichen planus

PURPOSE

To investigate the corneal topography and densitometry changes in patients with lichen planus (LP).

METHODS

Anterior segment parameters and corneal densitometry of patients with LP and age- and gender-matched individuals with healthy eyes were evaluated using Scheimpflug corneal topography. A 12 mm corneal area was divided into 4 annular zones and 3 regions-in-depth anterior, central and posterior-for densitometry evaluation.

RESULTS

The study included 45 patients with LP and 50 individuals with healthy eyes. The two groups were similar in age and gender, and they showed no significant differences in anterior segment corneal topography parameters. Schirmer's I test results were significantly lower in the patients with LP than in the control group (P ˂ .001). The total corneal densitometry was higher in patients with LP than in the control group (P = .030). The anterior, central and posterior corneal densitometry in the 0-2 mm and 2-6 mm annular zones was higher in the LP group than in the control group. Correlation analysis between disease duration and corneal densitometry values showed a strong positive correlation in the anterior segment and a moderate positive correlation in the central and posterior segments (r = 0.632, P ˂ .001; r = 0.572, P ˂ .001; and r = 0.562, P ˂ .001, respectively).

CONCLUSIONS

Corneal densitometry values were higher in patients with LP than in individuals with healthy eyes, even if the patients had a clinically transparent cornea. More studies are needed to evaluate the changes that may occur in corneal transparency in patients with LP and other autoimmune dermatologic diseases that may affect the eye.

A four-year observation of corneal densitometry after implantable collamer lens V4c implantation

Background

To observe the changes in corneal densitometry (CD) with a Pentacam after implantable collamer lens (ICL) V4c implantation in myopia patients, and to investigate potential influencing factors.

Methods

We reviewed 65 eyes of 33 patients (mean age, 29.08±5.54 years) with myopia or myopic astigmatism who underwent ICL V4c implantation. Clinic parameters and Pentacam images of corneal topography and CD were obtained pre- and postoperatively.

Results

After an average of 52±2.2 months follow-up, the efficacy and safety indexes assessed at the last follow-up were 1.03±0.18 and 1.21±0.21, respectively. Except in the central annular zone of 0-2 mm, the CD values increased significantly at postoperative day 1 and decreased significantly until postoperative 1 year (P<0.05). The increase in CD values at different annular zones at postoperative day 1 was ranked as: 0-2 mm <2-6 mm < 6-10 mm. No significant difference was observed in corneal density at 1 week, 1 month, and 1-year follow-up when compared with the preoperative value (P>0.05). The CD value at 4 years follow-up increased significantly and correlated positively with age and preoperative uncorrected distance visual acuity, and negatively with preoperative spherical equivalent and intraocular pressure (IOP) (P<0.05).

Conclusions

ICL V4c implantation demonstrated safety and efficacy for myopia correction. The CD value increased at 4 years postoperatively and correlated with age, preoperative spherical equivalent, uncorrected distance visual acuity, and IOP.

Analysis of Corneal Densitometry and Endothelial Cell Function in Fuchs Uveitis Syndrome

OBJECTIVES

To evaluate corneal densitometry and endothelial cell properties in patients with unilateral Fuchs uveitis syndrome (FUS), and to compare results with unaffected contralateral eyes and healthy control subjects.

METHODS

A total of 90 participants were included in this prospective cross-sectional study. Forty-five affected eyes of patients with FUS were regarded as group 1 (FUSa), 45 fellow eyes were regarded as group 2 (FUSf), and 45 healthy-control eyes were regarded as group 3. Corneal densitometry was measured with densitometry software of Scheimpflug Corneal Topography (Pentacam HR, Oculus GmbH, Wetzlar, Germany), whereas endothelial cell measurement was evaluated with specular microscopy (Tomey, EM4000, GmbH, Germany).

RESULTS

The mean corneal densitometry values were higher in the midstromal (zones; 2-6, 6-10 mm), posterior (all zones), and total thickness (zones; 2-6, 6-10 mm) layers in the FUSa compared with FUSf and control eyes (P<0.05 for all comparisons). The mean values of average cell area and cell size characteristics (minimum, maximum, SD, and coefficient of variation) were higher; endothelial cell density and percentage of hexagonal cells were lower in the FUSa than in the other two groups (P<0.05 for all comparisons). There was a significantly strong correlation between specular microscopy parameters and posterior corneal densitometry values in the FUSa group.

CONCLUSIONS

Impairment of endothelial cell function in affected eyes of patients with FUS resulted in increased values of corneal densitometry, especially posterior layer.

Corneal densitometry and biomechanical properties in patients with primary congenital glaucoma

OBJECTIVE

To describe corneal densitometry, topographic measurements, and biomechanical properties in patients with primary congenital glaucoma (PCG) and healthy patients. To examine correlations between variables and determine their glaucoma diagnostic capacity.

METHODS

This was a cross-sectional, case-control study conducted in 50 eyes of 50 patients with PCG (G1) and 40 eyes of 40 healthy patients (G2). The variables determined in each participant were: intraocular pressure, best corrected visual acuity (BCVA), corneal densitometry, topographic data using the Pentacam HR-Scheimpflug imaging system (Oculus Optikgerate GmbH, Wetzlar, Germany), and corneal hysteresis (CH) and corneal resistance factor (CRF) using the Ocular Response Analyzer (Reichert Ophthalmic Instruments, Depew, NY).

RESULTS

Overall densitometry was significatively higher in the PCG group (G1: 17.94 ± 4.99 vs G2: 13.25 ± 1.96, p < 0.001). CH (G1: 8.02 ± 11.35 vs G2: 11.35 ± 1.42, p < 0.001) and CRF (G1: 9.48 ± 2.83 vs G2: 10.77 ± 1.34, p < 0.001) were lower in the glaucoma group. Mean posterior, central, and anterior elevation and mean keratometry were higher in G1 (p < 0.05). In the PCG group, overall densitometry showed significant correlation with CH (r = -0.321, p = 0.028) and with BCVA (r = -0.498, p = 0.002). AUCs (areas under the curve) for CH and overall densitometry were high (0.839 and 0.899 respectively) and the best overall densitometry; CH and CRF cutoffs were 14.0, 9.3 and 9.2 respectively.

CONCLUSION

Densitometry is increased, and biomechanical corneal properties are decreased in patients with PCG. Densitometry and visual acuity showed a negative and significant correlation, so this measurement could be used as an indirect parameter of BCVA in the clinical practice.

Corneal Properties in Primary Open-angle Glaucoma Assessed Through Scheimpflug Corneal Topography and Densitometry

PURPOSE

The purpose of this study was to compare corneal topography and densitometry measurements in patients with primary open-angle glaucoma (POAG) and healthy subjects.

PATIENTS AND METHODS

A total of 200 eyes of 75 patients with POAG and 125 healthy controls underwent corneal topography and densitometry (Oculus Pentacam HR). The data compared in the 2 groups were: anterior chamber angle, anterior chamber depth, and anterior chamber volume, keratometry (Kminimum, Kmaximum, and Kmean), central corneal thickness, central anterior elevation, anterior elevation apex, maximum anterior elevation, and posterior elevation apex. Densitometry measurements were made at 3 depths on a 12-mm-diameter circle divided into 4 concentric rings (0 to 2, 2 to 6, 6 to 10, and 10 to 12 mm). The diagnostic capacity of the corneal variables was assessed through the areas under the receiver operating characteristics curve.

RESULTS

The corneal density of practically all depth layers and total corneal density were significantly higher in the POAG than the control group (P<0.05). Total corneal density was positively correlated with age (r=0.623; P<0.001) and also showed a good diagnostic capacity for glaucoma [area under the curve=0.617; 95% confidence interval (CI): 0.541-0.697; P<0.001]. In a multiple linear regression designed to assess its relationship with age, sex, central corneal thickness, and Kmean, age emerged as a significant confounder both in controls (coefficient=0.315; P<0.001; 95% CI: 0.246-0.384) and patients (coefficient=0.370; P<0.001; 95% CI: 0.255-0.486).

CONCLUSION

Corneal densitometry measurements showed a good diagnostic capacity for POAG suggesting this type of examination could have clinical applications in the diagnosis and management of glaucoma.

Corneal densitometry: a potential indicator for early diagnosis of Fabry disease

Purpose

To assess corneal densitometry in patients with Fabry disease (FD) and to compare corneal densitometry differences in FD patients to different corneal manifestations.

Methods

Ten participants (20 eyes) with FD and 10 age-matched healthy volunteers (20 eyes) were recruited. All participants were assessed by standardized ophthalmic examinations and the corneal densitometry analysis by Pentacam HR. Densitometry measurements were analyzed in standardized grayscale units.

Results

Seven patients developed conjunctival vessel tortuosity, cornea verticillata appeared in 6 patients, and two patients had Fabry cataract. Retinal vessel tortuosity occurred in 4 patients, and dilation of retinal vessels appeared in 3 patients, all symptoms occurred in both eyes. The first diagnosis of FD up to examination was 4.7 ± 3.23 years, and first ERT up to examination was 2.6 ± 2.27 years. The initial time to diagnosis was negatively related to the corneal densitometry value of the 0–2-mm (r = − 0.556, p = 0.011) and 2–6-mm (r = − 0.482, p = 0.032) zones in the posterior layer. FD group have significantly higher corneal densitometry in anterior 0–2-mm zone and 2–10-mm zone anterior and posterior layer than the control group (p ≤ 0.035, respectively). When divided into two groups by the existence of cornea verticillata, there was a statistically significant difference in the anterior layer, 6–10-mm zone (p = 0.031); in the central layer, 0–2 mm (p = 0.012), 2–6 mm (p = 0.001), 6–10 mm (p = 0.002), and total (p = 0.002); and in the posterior layer, 6–10 mm (p = 0.004) and total (p = 0.002).

Conclusions

FD patients show higher corneal densitometry, and corneal densitometry may have potential for early diagnosis and reminding progress of FD.

Corneal Scheimpflug Densitometry in Photorefractive Keratectomy Candidates

PURPOSE

To describe the normative data of corneal densitometry in photorefractive Keratectomy (PRK) candidates by using a Scheimpflug camera.

METHODS

Five hundred twenty-two eyes of 261 PRK candidates that underwent comprehensive optometric and ophthalmic examinations were enrolled in this study. Corneal densitometry values were obtained using a Scheimpflug camera (Pentacam HR; Oculus Optikgeräte GmbH, Wetzlar, Germany) and displayed in grayscale units (GSU).

RESULTS

Of 261 participants, 187 (71.6%) were women. The mean age of the participants was 28.79 ± 5.02 years (range: 21-40 years). The mean entire corneal densitometry was 14.86 ± 2.37 GSU. According to corneal depth, maximum and minimum densitometry values were seen in the anterior (30.28 ± 7.42 GSU) and posterior (9.86 ± 2.08 GSU) layers, respectively (P < 0.001). Based on the annulus over the cornea, the highest and lowest densitometry values were seen in the 10- to 12-mm (21.31 ± 4.26 GSU) and 2- to 6-mm zones (13.26 ± 2.34 GSU), respectively. However, this difference was not seen after 35 years of age. Individuals aged 30 to 35 years showed higher corneal densitometry values compared with subjects aged 20 to 25 years old (P < 0.001). In generalized linear models, the corneal thickness was associated with the densitometry value in the central and posterior corneal layers. There were no significant differences in sex and refractive errors among participants.

CONCLUSIONS

This study provided normal corneal densitometry data in PRK candidates. Corneal densitometry increased with age until 35 years of age and then decreased thereafter. This finding should be considered in patient selection for PRK and their postoperative examinations.

Pentacam corneal densitometry-guided treatment of adenoviral corneal subepithelial infiltrates: a comparative study between transepithelial phototherapeutic keratectomy and topical tacrolimus

PURPOSE

To compare the changes in the measurement of corneal densitometry and total corneal higher-order aberrations (HOAs) between topical tacrolimus and transepithelial phototherapeutic keratectomy (Te-PTK) in the treatment of adenoviral corneal subepithelial infiltrates (SEIs).

SUBJECT AND METHODS

This is an interventional prospective randomized study, including 63 eyes of 35 patients with symptomatic adenoviral corneal SEIs for at least 6 months. All patients underwent previous topical steroid therapy associated with unsatisfactory response and/or complications. Patients were assigned into three groups: (1) Te-PTK group: Te-PTK with MMC 0.02% was performed by a Technolas; Teneo excimer laser; (2) tacrolimus group: tacrolimus 0.03% ointment was applied once daily for 2-6 months; the endpoint of treatment was based on the improvement in the corneal densitometry, BCVA, and OSDI; and (3) control group: no intervention was done. BCVA, corneal densitometry, and total corneal higher-order aberrations (HOAs) evaluation using Pentacam HR were done at the baseline, 1 week, and then 1, 3, 6, and 12 months of the study.

RESULTS

The study population was similar between all groups. The mean follow-up was 12.75 ± 0.9 months. Bilateral corneal SEI was recorded at 80%. At 12-month follow-ups, the mean BCVA improved in both the Te-PTK and tacrolimus groups without significant changes in the control group. The mean corneal densitometry of the anterior, central, and total cornea decreased significantly in the Te-PTK and tacrolimus groups. HO-RMS and total RMS decreased significantly in the Te-PTK and tacrolimus groups. BCVA, corneal densitometry (anterior, central, and total cornea), and corneal aberrations (total coma, total trefoil, HO-RMS, and total RMS) values were significantly better for the Te-PTK and tacrolimus groups than the control group. There were no statistically significant differences between Te-PTK and tacrolimus groups in terms of BCVA, corneal densitometry, corneal HOA, and the persistence of corneal SEIs. The persistence of corneal SEIs was significantly lower in Te-PTK and tacrolimus groups than the control group.

CONCLUSION

Te-PTK and topical tacrolimus are effective methods for the treatment of adenoviral corneal SEIs improving visual acuity, corneal densitometry, and corneal HOA. The densitometry program of the Pentacam may give an objective guide for the treatment of adenoviral corneal SEIs.

TRIAL REGISTRATION

ClinicalTrials.gov ID is NCT04267991.

Corneal densitometry and topography in patients with primary congenital glaucoma

OBJECTIVE

To compare corneal densitometry and topography variables in patients with primary congenital glaucoma (PCG) and healthy subjects.

MATERIAL AND METHODS

Cross sectional study, consecutive recruitment with gender- and age-matched control group. Forty eyes of 40 patients in each group were studied with Pentacam corneal topography. The variables compared between the two groups were: intraocular pressure (IOP), visual acuity (VA) and Pentacam (Oculus, Wetzlar, Germany) corneal topography measurements: mean and maximum keratometry (Km, Kmax), cylinder (Cyl), anterior elevation apex (AEA), central anterior elevation (CAE), maximum anterior elevation (MAE), posterior elevation apex (PEA), central posterior elevation (CPE), maximum posterior elevation (MPE), pachymetry and anterior, mid-stromal and posterior corneal densitometry in the 0-2mm, 2-6mm, 6-10mm zones.

RESULTS

Significant differences between patients and healthy controls were detected in the topographic variables MAE (P=0.002) and MPE (P<0.001), and in all the densitometry variables (anterior, mid-stromal, posterior for the 0-2mm, 2-6mm and 6-10mm zones) (P<0.001 each). In the PCG group, negative correlation was observed between VA and total densitometry (r=-0.49; P=0.004).

CONCLUSION

Patients with PCG and healthy subjects display differences in corneal densitometry and topographic measurements. PCG patients show greater corneal density with an inverse relationship between visual acuity and higher elevation (anterior and posterior values).

Scheimpflug Corneal Densitometry Changes After Trabeculectomy

PURPOSE

To study the possible changes in Scheimpflug corneal densitometry 6 months after mitomycin C-augmented trabeculectomy and to compare these measurements with healthy controls.

METHODS

Corneal densitometry was monitored with the Pentacam HR3 before and 6 months after first-time uncomplicated mitomycin C-augmented trabeculectomy in 42 eyes of 42 white patients with open-angle glaucoma and in 22 healthy age-matched controls. Preoperative intraocular pressure (IOP), central corneal thickness, known duration of the disease, gender, the type and number of substances, applications and amount of benzalkonium chloride per day, and postoperative topical cortisone use were tested for possible correlations in the trabeculectomy group.

RESULTS

There was a statistically significant reduction of mean diurnal IOP from 19.0 ± 7.7 to 11.1 ± 7.7 mm Hg (P = 0.003) and the amount of pressure-lowering substances from 3.7 ± 1.0 to 0.1 ± 0.5 (P < 0.001). Densitometry measurements decreased in the entire cornea from 25.5 ± 5.7 to 23.1 ± 5.8 grayscale units (P = 0.001) with emphasis in the anterior layer. They returned close to normal 6 months after trabeculectomy and were not statistically significantly different compared with a healthy control group (22.8 ± 3.4 grayscale unit; P = 0.824). No correlations could be found with these observations and possible causing factors studied.

CONCLUSIONS

Corneal densitometry, an objective and sensitive measure of corneal transparency, returned close to normal 6 months after trabeculectomy. Although the observations cannot be associated with any causing factor in this study, the significant IOP reduction and the nearly complete cessation of topical antiglaucomatous substances including benzalkonium chloride seem to be the most plausible reasons for this finding.

One-year natural course of corneal densitometry in high myopic patients after implantation of an implantable collamer lens (model V4c)

BACKGROUND

Corneal densitometry, which is also known as corneal backscattering, is a surrogate measure of corneal clarity. The purpose of the study was to investigate the changes in corneal densitometry (CD) after implanting an implantable collamer lens (ICL-V4c).

METHOD

Twenty-six high myopic patients (aged 29.3 ± 6.6 years, 6 males and 20 females) who underwent ICL-V4c implantation were enrolled. Intraocular pressure (IOP), corneal topography, corneal densitometry, uncorrected distance visual acuity (UCDVA), manifest refraction, and best corrected distance visual acuity (BCDVA) were evaluated pre-operatively and at 1 day, 1 week, and 1, 3, 6, and 12 months post-operatively. Endothelial cell density (ECD) was measured pre-operatively and at 3, 6, and 12 months post-operatively. The efficacy index (mean post-operative UCDVA / mean pre-operative BCDVA) and the safety index (mean post-operative BCDVA / mean pre-operative BCDVA) were evaluated at 1 month, 3 months, 6 months and 12 months post-operatively.

RESULTS

Over the annular diameters of 0-2 mm, the pre-operative densitometry values of the anterior layer, central layer, posterior layer, and total layer were 20.1 ± 2.8, 11.8 ± 1.1, 10.5 ± 0.9 and 14.1 ± 1.5, respectively. From pre-operatively to post-operative Month 12, the values changed insignificantly (P = 0.177, P = 0.153, P = 0.543 and P = 0.207, respectively). Over the annular diameters of 2-6 mm, the pre-operative mean densitometry values were 17.9 ± 2.2, 10.5 ± 0.9, and 12.6 ± 1.2, respectively. From pre-operatively to post-operative Month 12, the values decreased to 16.5 ± 2.1, 10.0 ± 0.9, and 11.9 ± 1.2, respectively, which were similar to the pre-operative values (all P > 0.05) but significantly lower than the values obtained at post-operative Day 1 (P = 0.013, P = 0.002 and P = 0.010, respectively). The densitometry value of the posterior layer over the annular diameters of 2 to 6 mm remained unchanged (from 9.4 ± 0.7 to 9.1 ± 0.7) over time (P = 0.372). The efficacy and safety indices assessed at 12 months post-operatively were 1.04 ± 0.27 and 1.19 ± 0.23, respectively. The changes in IOP and ECD values were statistically insignificant (P = 0.896 and P = 0.968, respectively).

CONCLUSION

ICL-V4c implantation may be safe and efficient for high ametropia correction. The corneal densitometry values obtained over the annulus of 0-6 mm increased slightly from before the operation to post-operative Day 1 and then decreased gradually, which indicates that ICL-V4c implantation may not compromise corneal clarity.

Corneal Endothelial Morphology and Thickness Changes in Patients with Gout

Objectives:

To investigate corneal endothelial cell density (ECD), morphology, and central corneal thickness (CCT) in patients with gout compared with healthy subjects.

Materials and Methods:

Fifty eyes of 50 gout patients and 50 eyes of 50 healthy subjects without gout or any other systemic disease were included in this study. After detailed ophthalmologic examination, specular microscopy (Tomey EM-4000; Tomey Corp) measurement was performed for all participants. ECD, average cell area (ACA), coefficient of variation (CV), hexagonality ratio, and CCT values were recorded.

Results:

Mean ECD and hexagonality ratio were lower (p=0.004 and p=0.002) and CV, ACA, and CCT values were higher (p=0.001, p=0.007, and p=0.001) in patients with gout when compared to healthy subjects. There were significant correlations between gout disease duration and CD and hexagonality ratio (p=0.019 and p=0.043) and also between uric acid value and hexagonality ratio and CCT (p=0.044 and p=0.003).

Conclusion:

Altered corneal endothelial function was found in patients with gout when compared to healthy subjects and the alteration increased as gout duration and uric acid value increased.

Comparison of corneal densitometry between big-bubble and visco-bubble deep anterior lamellar keratoplasty

Aims

To evaluate deep corneal densitometry and visual outcomes after big-bubble (BB-DALK) and visco-bubble (VB-DALK) deep anterior lamellar keratoplasty performed in patients with keratoconus.

Methods

Prospective comparative study of 50 advanced keratoconic patients who underwent DALK surgery; 25 eyes (group I) were completed with BB-DALK and 25 eyes (group II) with VB-DALK after the failure of pneumatic dissection. Best spectacle-corrected visual acuity (BSCVA), corneal tomographic parameters and endothelial cell count were recorded 1, 3, 6, 12 and 24 months after surgery. Densitometric analysis of the deep corneal interface was obtained using Scheimpflug tomography at each visit; values recorded were compared between the two groups and statistically analysed.

Results

BSCVA was significantly better in the BB-DALK group than the VB-DALK group (0.39±0.29 vs 0.65±0.23 logarithm of the minimum angle of resolution, respectively) for the first 3 months; and in the same time period, densitometry was significantly higher in the VB-DALK group than those recorded in the BB-DALK group (23.97±5.34 vs 17.13±4.44 grayscale units). However, densitometric values and visual acuity did not differ significantly in the two groups at 1 year. No statistically significant difference for the other variables analysed at any time frame was found.

Conclusion

The use of viscoelastic substance in the VB-DALK technique may induce modification of interface stromal reflectivity resulting in reduced visual acuity up to 3 months postoperatively. However, this initial negative effect on the interface quality does not affect the long-term visual outcome, with densitometric values and visual outcomes similar in the two groups from 6 months postoperatively.

Correlation Between Corneal Topographic, Densitometry, and Biomechanical Parameters in Keratoconus Eyes

Purpose

To investigate the correlation between corneal densitometry, corneal topographic parameters, and corneal biomechanical properties in keratoconus.

Methods

A total of 76 eyes of 76 keratoconus patients were enrolled in this cross-sectional study. Corneal densitometry and topography were measured using Pentacam HR. Corneal biomechanical properties were measured using CorVis ST.

Results

The corneal densitometry values of the anterior 0 to 2 and 2 to 6 mm layers significantly correlated with the maximum keratometry values (R = 0.373, P = 0.001 and R = 0.276, P = 0.016, respectively), thinnest corneal thickness values (R = -0.331, P = 0.003 and R = -0.234, P = 0.042, respectively), anterior corneal elevation (R = 0.392, P < 0.001 and R = 0.323, P = 0.004, respectively), and posterior corneal elevation (R = 0.450, P < 0.001 and R = 0.367, P = 0.001, respectively). The stiffness parameter-applanation time 1 (SP-A1) significantly correlated with the corneal densitometry values for the anterior 0 to 2 mm (R = -0.397, P < 0.001), anterior 2 to 6 mm (R = -0.331, P = 0.004), central 0 to 2 mm (R = -0.306, P = 0.007), central 2 to 6 mm (R = -0.228, P = 0.048), posterior 2 to 6 mm (R = -0.243, P = 0.035), total 0 to 2 mm (R = -0.291, P = 0.011), and total 2 to 6 mm (R = -0.295, P = 0.010) layers.

Conclusions

The corneal densitometry values correlated with the severity of keratoconus and the SP-A1 values.

Translational Relevance

Corneal densitometry values may serve as markers to predict the severity of keratoconus.

The effect of corneal infiltrates on densitometry and higher-order aberrations

BACKGROUND

This study aimed to measure the effects of persistent corneal subepithelial infiltrates associated with epidemic keratoconjunctivitis on corneal densitometry and total corneal higher order aberrations (HOAs), and to compare these measurements with the data obtained from their fellow unaffected healthy eyes.

METHODS

This prospective cross-sectional study included those who had persistent subepithelial infiltrates in only the affected eyes for at least three months and clinically normal fellow unaffected eyes. Corneal densitometry was measured with the densitometry software of the Pentacam HR-Scheimpflug corneal topographer over a 12 mm diameter of cornea. Further, total corneal HOAs including coma (Z[1,3], Z[3,-1]), trefoil (Z[3], Z[3,-3]), spherical aberration, higher order root mean square (HO-RMS), and total RMS in the Zernike analysis were analysed by the same Pentacam HR device.

RESULTS

Forty-six eyes of 23 participants were analysed in this study. The mean corneal densitometry values were statistically significantly higher in all annular concentric areas (0-2, 2-6, 6-10, and 10-12 mm) of the anterior and central corneal layers in the eyes with subepithelial infiltrates when compared to normal fellow eyes (p < 0.05, for each one). Additionally, there were statistically significant differences between the eyes with subepithelial infiltrates and normal fellow eyes with regard to coma, trefoil, HO-RMS, and total RMS in the Zernike analysis (p < 0.05, for each one).

CONCLUSION

This study quantitatively demonstrated that persistent corneal subepithelial infiltrates associated with epidemic keratoconjunctivitis decrease corneal transparency and corneal optical quality in affected eyes.