Scheimpflug Imaging Research Articles

Mediators of Visual Acuity in Descemet Membrane Endothelial Keratoplasty and Ultrathin Descemet Stripping Automated Endothelial Keratoplasty.

The aim of this study was to investigate mediators of visual acuity in ultrathin Descemet stripping automated endothelial keratoplasty (UT-DSAEK) compared with Descemet membrane endothelial keratoplasty (DMEK). This was a prespecified secondary analysis of the Descemet Endothelial Thickness Comparison Trial, a prospective, randomized controlled trial comparing UT-DSAEK with DMEK. Subjects with Fuchs endothelial dystrophy or pseudophakic bullous keratopathy presenting to 2 academic centers were enrolled and randomized to either UT-DSAEK (n = 25 eyes) or DMEK (n = 25 eyes). Higher order aberrations (HOAs) and corneal densitometry were measured with Pentacam Scheimpflug imaging at 3, 6, 12, and 24 months. The posterior corneal surface at the 6.0-mm optical zone had significantly less total HOAs ( P <0.001) in the DMEK group compared with UT-DSAEK at 24 months. Anterior and posterior corneal densitometry improved from baseline to 24 months for both UT-DSAEK and DMEK, but there was no significant difference between the 2 groups. Corneal densitometry and posterior HOAs were both associated with best-corrected visual acuity ( P <0.05). DMEK had 1.3 logarithm of the minimum angle of resolution better visual acuity compared with UT-DSAEK at 24 months. Approximately 64% of this effect was mediated through posterior HOAs, whereas none was mediated through anterior HOAs or densitometry. Decreased posterior HOAs mediate better visual acuity and account for improved vision after DMEK compared with UT-DSAEK. Corneal light scatter as measured by densitometry is similar between UT-DSAEK and DMEK, indicating that the increased thickness and stromal-stromal interface in UT-DSAEK do not significantly affect visual acuity.

In Vivo Biomechanical Response of the Human Cornea to Acoustic Waves

The cornea is the optical window to the brain. Its optical and structural properties are responsible for optical transparency and vision. The shape, elasticity, rigidity, or stiffness are due to its biomechanical properties, whose stability results in ocular integrity and intraocular pressure dynamics. Here, we report in vivo observations of shape changes and biomechanical alterations in the human cornea induced by acoustic wave pressure within the frequency range of 50–350 Hz and the sound pressure level of 90 dB. The central corneal thickness (CCT) and eccentricity (e2) were measured using Scheimpflug imaging and biomechanical properties [corneal hysteresis (CH) and intraocular pressure (IOP)] were assessed with air-puff tonometry in six young, healthy volunteers. At the specific 150 Hz acoustic frequency, the variations in e2 and CCT were 0.058 and 7.33 µm, respectively. Biomechanical alterations were also observed in both the IOP (a decrease of 3.60 mmHg) and CH (an increase of 0.40 mmHg).

Accuracy of an Air-Puff Dynamic Tonometry Biomarker to Discriminate the Corneal Biomechanical Response in Patients With Keratoconus.

The aim of this study was to assess accuracy of the mean corneal stiffness ( kc , N/m) parameter to discriminate between patients with keratoconus and age-matched healthy subjects. Dynamic Scheimpflug imaging tonometry was performed with Corvis ST (Oculus Optikgeräte GmbH, Germany) in patients with keratoconus (n = 24; study group) and age-matched healthy subjects (n = 32; control). An image processing algorithm was developed to analyze the video sequence of the Corvis ST air-puff event and to determine the geometric and temporal parameters that correlated with the corneal tissue biomechanical properties. A modified 3-element viscoelastic model was used to derive the kc parameter, which represented the corneal tissue resistance to deformation under load. Receiver operating characteristic curves were used to assess the overall diagnostic performance for determining the area under the curve, sensitivity, and specificity of the kc in assessing the corneal tissue deformation to the Corvis ST air-puff event in keratoconus and control eyes. The Corvis Biomechanical Index ( CBI ) was analyzed for external validation. The kc parameter was significantly different between keratoconus and controls ( P < 0.001), ranging from 24.9 ±3.0 to 34.2 ±3.5 N/m, respectively. It was highly correlated with CBI (r = -0.69; P < 0.001); however, the kc parameter had greater specificity (94%) than CBI (75%), whereas the 2 biomarkers had similar area under the curve (0.98 vs. 0.94) and sensitivity (96% vs. 92%) in predicting the occurrence of keratoconus. The kc parameter extracted by video processing analysis of dynamic Scheimpflug tonometry data was highly accurate in discriminating patients with clinically manifest keratoconus compared with controls.

Scheimpflug Corneal Tomography Anterior Chamber Depth in Descemet Stripping Endothelial Keratoplasty Recipients.

Our study investigates whether preoperative anterior chamber depth (ACD) measured by Scheimpflug tomography could serve as a potential predictor of graft failure in eyes undergoing Descemet stripping endothelial keratoplasty (DSEK). A retrospective review was conducted on patients who underwent primary or repeat DSEK between January 2020 and August 2021 at Bascom Palmer Eye Institute. Charts from 378 primary and 192 repeat DSEK patients were reviewed and ultimately 47 primary and 21 repeat DSEK patients met criteria for inclusion. Data collection included demographics, preoperative ACD, best-corrected visual acuity, and length of follow-up. Demographics were similar between groups, and there was no significant difference in the average best-corrected visual acuity between the single and repeat DSEK groups preoperatively. Baseline preoperative ACD was greatest in the single DSEK group (3.51 ± 0.90 mm) when compared to baseline preoperative ACD in the repeat DSEK group (3.01 ± 0.67 mm, P = 0.003). The preoperative mean ACD was smallest in the repeat DSEK group before the second DSEK (2.94 ± 0.48 mm, P = 0.001). Preoperative baseline ACD was the only variable to affect graft survival time significantly ( P = 0.012). The incidence of glaucoma diagnosis was similar in both groups (42.5% vs. 42.8%, P = 0.471). The diagnosis of glaucoma and presence of incisional glaucoma surgery did not affect the graft survival time ( P = 0.129, P = 0.559) or need for repeat DSEK. Smaller baseline preoperative Scheimpflug ACD measurement may be a possible predictor of the need for repeat DSEK. Our study found that Scheimpflug ACD decreases with subsequent DSEK failure.

Evaluation of Ciliary Body Morphology and Position of Implantable Collamer Lens in Low-Vault Eyes Using Ultrasound Biomicroscopy.

To investigate the ciliary body anatomy and position of the implantable collamer lens (ICL) in low-vault eyes and analyze factors related to insufficient vault. Zhongshan Ophthalmic Center, Guangzhou, China. Retrospective case-control observational study. In this study, 73 eyes of 73 patients with insufficient vault (＜250 µm) were matched with 73 eyes with an ideal vault (250 to 750 µm). Ultrasound biomicroscopy (UBM) was used to determine the ciliary body morphology and ICL position. The biometric parameters acquired by Scheimpflug tomography were compared. The correlation between the vault and these factors was analyzed, and the Least Absolute Shrinkage and Selection Operator (LASSO) method was used to screen the risk factors for low-vault. The low-vault group had a steeper corneal curvature, thicker lens thickness (LT), higher crystalline lens rise, and shorter axial length (AL) (All P <.005). The ciliary process length (CPL) and maximum ciliary body thickness (CBTmax) were significantly smaller, and the trabecular-ciliary angle (TCA), iris-ciliary angle (ICA), and ciliary sulus width (CSW) were significantly greater in the low-vault eyes. (All P <.005). The low-vault group had more ICL haptics below the ciliary process, and TCA, ICA, CPL, CBTmax, CSW, and haptic position were related to the postoperative vault (All P <.05). CPL, AL, and LT were identified as predictors of a low-vault. Malposition of ICL haptics behind the ciliary process is a risk factor for low-vault. A shorter CPL, thicker LT, and shorter AL are significant risk factors for postoperative low-vault.

New keratoconus staging system based on OCT.

To establish a numerical spectral-domain optical coherence tomography (SD-OCT)-based keratoconus (KC) staging system and compare it with existing KC staging systems. Eye Hospital of Wenzhou Medical University, Wenzhou, China. Retrospective case-control study. Scheimpflug tomography, air-puff tonometry, and SD-OCT were performed on 236 normal and 331 KC eyes. All SD-OCT-derived parameters of the corneal epithelium and stroma were evaluated based on their receiver operating characteristic (ROC) curves, area under the curve (AUC), sensitivity, and specificity to discriminate between normal and KC eyes. The best performing parameters were subsequently used to create an OCT-based staging system, which was compared with existing tomographic and biomechanical staging systems. 236 eyes from 236 normal patients and 331 eyes from 331 KC patients of different stages were included. The highest ranked AUC ROC SD-OCT parameters, derived from stroma and epithelium, were stroma overall minimum thickness (ST: AUC 0.836, sensitivity 90%, specificity 67%) and epithelium overall SD (EP: AUC 0.835, sensitivity 75%, specificity 78%). A numerical SD-OCT staging system called STEP including 2 parameters-"ST" and "EP"-with 5 stages was proposed. The new SD-OCT-based KC staging system is the first to take the epithelium with its sublayer stroma information into account, showing a strong agreement to the existing staging systems. This system could be incorporated into daily practice, potentially leading to an overall improvement in KC treatment and follow-up management.

Effective Optical Zone and Centration Following SMILE and FS-LASIK for High Myopia Calculated With a Novel Method

Purpose: To compare the effective optical zone (EOZ) and centration in eyes with high myopia after small incision lenticule extraction (SMILE) and femtosecond laser–assisted in situ keratomileusis (FS-LASIK) using a novel method. Methods: Forty eyes of 40 consecutive patients with high myopia scheduled for SMILE or FS-LASIK were enrolled in the study. The EOZ, optical zone decentration, and corneal aberrations were analyzed using Scheimpflug imaging. These values were then analyzed and compared between the two procedures 6 months after surgery. Results: The mean EOZ diameter for SMILE (4.41 ± 0.14 mm) was larger than that for FS-LASIK (4.24 ± 0.28 mm; P = .002), corresponding to reductions of 1.60 ± 0.11 and 1.71 ± 0.21 mm, respectively, compared with the programmed optical zone (POZ) ( P = .007). Moreover, the total decentration for SMILE (0.33 ± 0.12 mm) was greater than that for FS-LASIK (0.27 ± 0.15 mm; P = .020). The induction of spherical aberration (SA) was lower with SMILE than with FS-LASIK ( P = .007). Conclusions: A larger EOZ and less SA were observed after SMILE than after FS-LASIK in eyes with high myopia. [ J Refract Surg . 2023;39(11):736–740.]

Children with high astigmatism: tomographic and refractive characteristics and the ability of current indices to rule out keratoconus

PurposeTo assess corneal tomographic, topographic, and refractive changes in children with high astigmatism and their ability to exclude keratoconus. MethodsIn this longitudinal observational study, the medical records of children with high regular cylindrical refraction of ≥3.50 D referred to the Hospital for Sick Children, Toronto, to exclude keratoconus between January 2009 and June 2020 were reviewed retrospectively. Corneal tomography records (Scheimpflug imaging) were reviewed for subjects with total astigmatism of ≥ +3.50 D by retinoscopy. Children with abnormal anterior segment examination and/or other risk factors for corneal disease or ectasia and those with unreliable corneal tomography were excluded. Baseline demographic, longitudinal tomographic, topographic, and refractive data were analyzed. ResultsA total of 67 eyes of 37 children (mean age, 9.1 ± 3.5 years) were included. Mean cylindrical refraction at presentation was 5.10 ± 1.30 D. Mean follow-up was 2.3 ± 1.8 years. Twenty-nine eyes had Kmax ≥47.20 D at baseline, with no change at last follow-up. Ksteep, Kmax, and thinnest pachymetry were 46.44 ± 2.33 D, 47.06 ± 2.57 D, and 525.86 ± 35.45 μm, respectively, at baseline compared with 46.40 ± 2.28 D, 46.98 ± 2.40 D, and 527.61 ± 37.67 μm at last follow-up (P > 0.05). All eyes were predicted as not having keratoconus using inferior-superior dioptric asymmetry ratio (I-S ratio), and the keratometry, inferior-superior, and astigmatism index (KISA%), which also incorporates skew percentage. The other tomographic indices predicted keratoconus or subclinical keratoconus in at least 22.4% of eyes. All parameters did not significantly change during follow-up. ConclusionsIn the absence of other risk factors for keratoconus, children with high regular astigmatism demonstrated clinical and tomographic stability over time. Based on our results, we recommend that I-S ratio and KISA% be primarily used when monitoring normal children with high astigmatism to rule out keratoconus-related changes.

Influence of Subclinical Corneal Edema on Contrast Sensitivity in Fuchs Endothelial Corneal Dystrophy.

The aim of this study was to compare visual function, with a focus on contrast sensitivity, between patients with Fuchs endothelial corneal dystrophy (FECD) with and without subclinical corneal edema. In this cross-sectional, observational, single-center study, 46 pseudophakic eyes of 31 patients with FECD were divided into 2 groups depending on the presence of subclinical corneal edema. All eyes presented with a Krachmer grade of 5 and no clinical corneal edema. The criteria for subclinical corneal edema were loss of regular isopachs, displacement of the thinnest point, and focal posterior surface depression in Scheimpflug tomography. If more than 1 criterion was present, subclinical corneal edema was diagnosed. The corrected distance visual acuity, contrast sensitivity (Pelli-Robson chart and CSV-1000 test with optional glare), and straylight were measured. The differences between both groups were analyzed using clustered Wilcoxon rank-sum tests. The corrected distance visual acuity and the contrast sensitivity, measured with a Pelli-Robson chart, were significantly inferior in eyes with subclinical corneal edema compared with eyes without subclinical edema ( P < 0.05). At all spatial frequencies, eyes with subclinical edema demonstrated lower contrast sensitivity with a statistically significantly reduction in total contrast sensitivity when tested with ( P = 0.005) and without ( P = 0.002) glare. The straylight did not significantly differ between both groups ( P > 0.05). The corrected distance visual acuity and contrast sensitivity were significantly reduced in FECD eyes with subclinical corneal edema compared with those with no subclinical edema. This decrease in visual quality may be considered when evaluating the need for surgical intervention at earlier stages of FECD.

Repeatability and Agreement of Chord Mu Between Scheimpflug Tomography and Swept-source Optical Coherence Tomography.

To evaluate repeatability and agreemeny of chord mu between Scheimpflug tomography (Pentacam HR, Oculus Optikgeräte GmbH, Wetzlar, Germany) and swept-source optical coherence tomography-based optical biometer (IOLMaster 700, Carl Zeiss Meditec AG, Jena, Germany). In this retrospective study, 63 eyes of 33 patients were included. Chord mu, X, and Y Cartesian distances between the corneal vertex and the pupil center (Px and Py), and the pupil diameter were compared using two instruments. Repeatability was evaluated using intraclass correlation coefficient (ICC), coefficient of variation (CoV), and within-subject standard deviation (Sw). Inter-device agreement was evaluated using paired t-tests and Bland-Altman plots. Although Sw values for all parameters were similar between the two devices, CoV values of chord mu and pupil diameter were lower, and ICC values of those parameters were higher, in the IOLMaster 700 than in the Pentacam HR. Chord mu and pupil diameter values were higher in IOLMaster 700 than Pentacam HR (p < 0.01). The width of the 95% limit of agreement was wide for all parameters. IOLMaster 700 showed better repeatability than Pentacam HR in chord mu, Px, Py, and pupil diameter values. Because there were statistically significant differences and a low level of agreement in chord mu and pupil diameter values between the two devices, they cannot be used interchangeably.

Refractive Index Measurement of the Crystalline Lens in Vivo.

This study provides a new method to measure the refractive index of crystalline lens in the human eye in vivo . Accessing the refractive index of crystalline lenses in the human eye in vivo has long been a challenge. This study aimed to measure the refractive index of a lens in vivo using an anterior segment optical coherence tomography (AS-OCT) system combined with a Scheimpflug imaging system. A ray-traceable Scheimpflug imaging was developed and integrated into an AS-OCT system. A theoretical study revealed that the combination of these two systems provides a unique solution for simultaneously measuring the refractive index and the thickness of the lens. The average lens refractive index along the ray pathway ( Nav ) and lens shape were measured for seven subjects. The lens Nav along the central ray varies from 1.383 to 1.419 between subjects. The lens refractive index function across the lens diameter varies from subject to subject. The lens Nav increases for accommodated eyes. The thicknesses and profiles of the lenses are also determined. The lens refractive index varies substantially from individual eye to individual eye, not only along the central ray pathway but also for the lens refractive index function across the lens diameter. Ray-traceable Scheimpflug imaging-equipped AS-OCT is useful for testing the refractive index of lenses in the human eye in vivo .

Subclinical Keratoconus Detection and Characterization Using Motion-Tracking Brillouin Microscopy

To characterize focal biomechanical alterations in subclinical keratoconus (SKC) using motion-tracking (MT) Brillouin microscopy and evaluate the ability of MT Brillouin metrics to differentiate eyes with SKC from normal control eyes. Prospective cross-sectional study. Thirty eyes from 30 patients were evaluated, including 15 eyes from 15 bilaterally normal patients and 15 eyes with SKC from 15 patients. All patients underwent Scheimpflug tomography and MT Brillouin microscopy using a custom-built device. Mean and minimum MT Brillouin values within the anterior plateau region and anterior 150 μm were generated. Scheimpflug metrics evaluated included inferior-superior (IS) value, maximum keratometry (Kmax), thinnest corneal thickness, asymmetry indices, Belin/Ambrosio display total deviation, and Ambrosio relational thickness. Receiver operating characteristic (ROC) curves were generated for all Scheimpflug and MT Brillouin metrics evaluated to determine the area under the ROC curve (AUC), sensitivity, and specificity for each variable. Discriminative performance based on AUC, sensitivity, and specificity. No significant differences were found between groups for age, sex, manifest refraction spherical equivalent, corrected distance visual acuity, Kmax, or KISA% index. Among Scheimpflug metrics, significant differences were found between groups for thinnest corneal thickness (556 μm vs. 522 μm; P < 0.001), IS value (0.29 diopter [D] vs. 1.05 D; P < 0.001), index of vertical asymmetry (IVA; 0.10 vs. 0.19; P < 0.001), and keratoconus index (1.01 vs. 1.05; P < 0.001), and no significant differences were found for any other Scheimpflug metric. Among MT Brillouin metrics, clear differences were found between control eyes and eyes with SKC for mean plateau (5.71 GHz vs. 5.68 GHz; P < 0.0001), minimum plateau (5.69 GHz vs. 5.65 GHz; P < 0.0001), mean anterior 150 μm (5.72 GHz vs. 5.68 GHz; P < 0.0001), and minimum anterior 150 μm (5.70 GHz vs. 5.66 GHz; P < 0.001). All MT Brillouin plateau and anterior 150 μm mean and minimum metrics fully differentiated groups (AUC, 1.0 for each), whereas the best performing Scheimpflug metrics were keratoconus index (AUC, 0.91), IS value (AUC, 0.89), and IVA (AUC, 0.88). Motion-tracking Brillouin microscopy metrics effectively characterize focal corneal biomechanical alterations in eyes with SKC and clearly differentiated these eyes from control eyes, including eyes that were not differentiated accurately using Scheimpflug metrics. Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Klinik olarak Tek Taraflı Psödoeksfoliasyon Sendromu Olanların Ön Segment Parametrelerinin Schempflug Görüntüleme Tekniği ile değerlendirilmesi

Objective: We aimed to compare the intraocular pressure (IOP), keratometry values (K), and anterior segment parameters of patients with clinically unilateral pseudoexfoliation syndrome (PEX) with the other eyes without PEX and the control group. Material and Method: Fifty four patients with unilateral PEX findings and 40 participants without PEX findings in both eyes were included in the study as a control group. IOP was measured by Goldmann applanation tonometry. K values and anterior segment parameters [central corneal thickness (CCT), anterior chamber depth (ACD), iridocorneal angle (ICA), and anterior chamber volume (ACV)] were measured using Scheimpflug imaging technique. Results: The mean age of PEX patients was 67.9±9.2 years, while the mean age of the control group was 58.9±5.7 years. The IOP values of the eyes with PEX were significantly higher than the other eyes (p=0.02), and there was no significant difference between them and the control group (p=0.59). In terms of K values and anterior segment parameters, the measurements of eyes with PEX and the other eyes, and eyes with PEX and control group were similar (p&amp;gt;0.05). Conclusion: In our study, eyes with PEX had higher IOP values than the fellow eyes and control group. In addition, thinner CCT, narrower ACD, and ICA values were found in eyes with PEX than in the other eyes. However, these values were not statistically significant.

Corneal remodeling after SMILE for moderate and high myopia: short-term assessment of spatial changes in corneal volume and thickness

PurposeTo evaluate the early corneal remodeling and its influencing factors after Small incision lenticule extraction (SMILE) for moderate and high myopia.MethodsThis was a retrospective study. Pre- and post-operative (1 week and 1, 3, 6 months) corneal volume (CV), mean keratometry (Km), and corneal thickness (CT) were measured by Scheimpflug tomography. CT at the central, thinnest point, and on concentric circles of 2, 4, and 6 mm diameter was recorded to assess corneal thickness spatial profile (CTSP) and percentage of thickness increase (PTI) in the moderate and high myopia groups, and to explore possible influencing factors.ResultsAfter SMILE, the peripheral CT decreased in the moderate myopia group and central corneal thickness (CCT) increased in the high myopia group at 1 month compared to 1 week (all P < 0.05). The CV, Km and CT were significantly increased at 3 months compared to 1 month (all P < 0.05), but there was no significant change at 6 months compared to 3 months for both groups (all P > 0.05). Patients with high myopia showed greater corneal thickness changes (△CT) and higher PTI than moderate myopia (all P < 0.05). Regression analysis revealed that in addition to refraction, peripheral PTI was negatively correlated with CCT in the moderate myopia group (4 mm: β = -0.023, P = 0.001; 6 mm: β = -0.050, P < 0.001), as well as in the high myopia group (4 mm: β = -0.038, P < 0.001; 6 mm: β = -0.094, P < 0.001). Moreover, peripheral PTI in the moderate myopia group was negatively correlated with age (4 mm: β = -0.071, P = 0.003; 6 mm: β = -0.162, P < 0.001).ConclusionsAfter SMILE, the CV, Km, and CTSP showed dynamic changes in the early stage, which stabilized after 3 months. Compared to the moderate myopia group, the high myopia group experienced slower corneal stabilization. The change in PTI at 6 months after SMILE may be related to higher preoperative refraction, thinner CCT and younger age.

Rate of fractional change in corneal tomography parameters in keratoconus using a combination of predictive parameters

BackgroundTo compare the rate of fractional change for multiple corneal tomographic factors in progressive keratoconus (KC).MethodsIn this retrospective case series, 40 eyes (40 patients) with progressive KC (increase in central keratometry of 1.00 D or maximum keratometry of 1.50 D on two visits at least six months apart) were included. Cases with previous history of ocular surgery, poor scans, corneal scars, severe dry eyes, post-excimer ectasia, pellucid marginal degeneration were excluded. Medical records, corneal tomography and anterior corneal wavefront (8 mm) (Scheimpflug tomography, Pentacam, Oculus, Germany) were analyzed. Rate of fractional change (Rx = (x1 − x0)/(|x0|tm)); where, x1 = value at follow-up, x0 = value at initial visit and tm = time in months, was measured.ResultsThe mean age of the patients was 30.0 ± 8.4 years. The mean follow-up duration was 8.9 ± 4.2 months. Coma (0.076 ± 1.4) had the largest rate of fractional change (P = 1.7 × 10−14, Kruskal–Wallis test). The rate of fractional change was higher for aberrometric parameters (anterior corneal higher-order aberrations root mean square and anterior coma) compared to pachymetric and keratometric parameters (P values ranging from 1.4 × 10−4 to 7.4 × 10−10, Mann–Whitney test, effect size ranging from 0.4–0.7). The rate of fractional change was comparable between pachymetric and keratometric factors (P > 0.05 for all comparisons, Mann–Whitney test).ConclusionsAnterior corneal wavefront, especially anterior coma, were noted to have higher rate of fractional change compared to single point keratometric and pachymetric indices in progressive KC. This information can be used for decision-making when monitoring patients with KC.

Problemlösung bei komplizierten kornealen Verhältnissen: Sklerallinsen und deren Anpassung mit neuen modernen Messmethoden

Purpose. The case report describes the follow up fitting with scleral contact lenses for visual rehabilitation in advanced keratoconus and the influence of the scleral fitting characteristics on the daily wearing time as well as the wearing comfort of the contact lenses. Material and Methods. Scleral contact lenses were fitted using Scheimpflug images and analysis of optical coherence tomography cross-sectional images. Based on this data an optimization of the contact lens design could be performed. Results. In the present case, a significant improvement in visual acuity, daily wearing time and wearing comfort was achieved due to scleral lens re-fitting with individual scleral lens sagittal height calculation and custom fitting according to corneo-scleral profile measurement data. Conclusion. Scleral lenses can be a good alternative to other contact lens treatments to achieve visual rehabilitation in complex corneal situations. Analysis of the corneo-scleral profile by Scheimpflug technique and accurate evaluation of the sagittal height are of great benefit, in addition to the assessment of the fitting and landing zone of scleral lenses by anterior segment OCT. This results in significant time savings for the fitting and leads to a more physiologically compatible contact lens treatment result. Keywords keratoconus, scleral lenses, optical coherence tomography (OCT), corneo-scleral profile (CSP)

Surgical management of complicated Descemet’s membrane detachment in corneas without prior endothelial keratoplasty

PurposeTo provide insights into morphologic and functional features of eyes with complicated Descemet's membrane detachment (DMD) and report clinical outcomes after surgical intervention.MethodsRetrospective study of 18 eyes with complicated DMD between 2010 and 2022. Complicated DMD was defined if any of the following criteria applied: prior penetrating keratoplasty (PKP), corneal thinning, total DMD or persistent DMD after Air/Gas-Descemetopexy. Causes, surgical management, and clinical outcomes were analyzed. Scheimpflug tomography, anterior segment optical coherence tomography (AS-OCT) and histologic examination were performed to characterize corneas with DMD.ResultsFourteen eyes with prior PKP developed spontaneous DMD after 24.2 ± 12.9 years (range = 18 months – 47 years, median = 25.7 years). Complicated DMD without prior PKP was associated in three eyes after cataract surgery and in one eye after infectious keratitis. In cases with previous PKP, AS-OCT demonstrated rupture of Descemet’s membrane (DM) in five eyes and spontaneous reattachment was found in four eyes within 8 weeks of initial diagnosis, with no rupture of DM in any of the cases. There was no rupture of DM in corneas without previous PKP. After prior keratoplasty, definitive surgical treatment was repeat PKP in 13 eyes and Air/Gas-Descemetopexy in one eye. In corneas without prior keratoplasty, three eyes underwent PKP and one eye Air/Gas-Descemetopexy. Histological examination of two corneal explants revealed a severely thinned graft-host junction and a disrupted DM close to the graft-host junction. Visual acuity improved from 1.80 ± 0.58 logMAR to 0.75 ± 0.69 logMAR after prior PKP and from 1.45 ± 0.65 logMAR to 0.85 ± 1.13 logMAR without prior PKP. The postoperative course was uneventful in 16 of 18 eyes.ConclusionPKP is an effective treatment option for complicated DMD, especially in ectatic corneas, whereas Air/Gas-Descemetopexy or Descemet Membrane Endothelial Keratoplasty do not address the primary issue of the curvature anomaly.

Minimum Corneal Diameter and Anterior Steep Axis Curvature Share the Same Meridian: A Novel Finding

To define the external scleral sulcus (ESS) on a Scheimpflug image and use it for a morphometric analysis of corneal diameter (CD). Retrospective, cross-sectional study of pediatric Asian-Indian eyes. One random eye of 353 subjects between 5 and 18 years underwent 25-scan Pentacam HR imaging. For all scans, densitometry values along the anterior corneal edge were recorded and differentiated. The peaks on the differentiated curve were chosen as the ESS points, and this distance between them was called CD. Vertical (vCD), maximum (maxCD), minimum (minCD) CD and their meridians were defined. Multiple regression models (MRMs) with CD and other Pentacam parameters were built to predict astigmatism and its axis, mean keratometry (Kmean), and Belin/Ambrósio enhanced ectasia display deviation (BAD-D). MRMs were validated using intraclass correlation coefficient (ICC). Estimated horizontal CD (hCD) was validated against digital caliper measurement using ICC. The ICC (95% CI) between caliper and hCD was 0.96 (0.93, 0.97). MRM predictions (P < .001) used CD parameters, anterior chamber depth, corneal volume and distance from the corneal thinnest location to apex. These predictions achieved an ICC of 0.34 (0.18, 0.46), 0.82 (0.78, 0.86), 0.87 (0.84, 0.89), and 0.81 (0.76, 0.84), respectively. The astigmatism axis prediction depended on the minCD and maxCD meridians. Its within-subject SD (4.97°) was less than 2 consecutive Pentacam scan angles (7.2°). The CD metric strongly correlated with the astigmatism axis, keratometry, and BAD-D. Its spatial description may be significant in corneal treatment planning and disease diagnoses.

Comparison of the Central Corneal Thickness between a Scheimpflug Imaging-Based Device and an Optical Measurement-Based Device

Background Central corneal thickness is a critical parameter in corneal evaluation for a wide range of purposes in ophthalmology such as refractive surgeries including LASIK, cataract surgeries to assess endothelial pump function preoperatively to preserve the corneal transparency, and glaucoma in terms of diagnosis, management and follow up to avoid over/underestimation of intraocular pressure due to variations in CCT. Aim of the Work The study will investigate the discrepancy in measuring the CCT between Scheimpflug imaging using the Nidek AL-Scan and optical pachymetry using the Nidek Specular Microscope CEM-530. Patients and Methods In our study, we compared CCT measurements of both devices among 70 eyes of 35 normal subjects with a nonsignificant past ocular history. All subjects attended Ophthalmology Department at Ain Shams University Hospitals and all measurements were taken by the same examiner at the same time of the day. Our study is an observational comparative crosssectional study for six months in Ain Shams University Hospitals, Cairo, Egypt after approval of the research ethical committee on normal people without any history of ocular pathology except for refractive errors. Results The mean age of the study subjects was 29.49 ± 7.98 years (range 20-48 years). Regarding age, sex, and refraction, there was no statistically significant difference between CCT measurements by each individual device. However, there was a statistically significant difference between CCT measurements when compared by both devices. The difference between the mean ± SD of both devices was 7.17 ± 0.98 µm. Conclusion There is a statistically significant difference in central corneal thickness measurement between Nidek AL-Scan and Nidek Specular Microscope CEM-530. Several studies are needed to further correlate CCT with other parameters measured by both devices, namely anterior chamber depth and axial length.

Systematic Review of the Diagnostic Criteria and Severity Classification for Fuchs Endothelial Corneal Dystrophy.

There are no defined diagnostic criteria and severity classification for Fuchs endothelial corneal dystrophy (FECD), which are required for objective standardized assessments. Therefore, we performed a systematic literature review of the current diagnosis and severity classification of FECD. We searched the Ovid MEDLINE and Web of Science databases for studies published until January 13, 2021. We excluded review articles, conference abstracts, editorials, case reports with <5 patients, and letters. Among 468 articles identified, we excluded 173 and 165 articles in the first and second screenings, respectively. Among the 130 included articles, 61 (47%) and 99 (76%) mentioned the diagnostic criteria for FECD and described its severity classification, respectively. Regarding diagnosis, slitlamp microscope alone was the most frequently used device in 31 (51%) of 61 articles. Regarding diagnostic findings, corneal guttae alone was the most common parameter [adopted in 23 articles (38%)]. Regarding severity classification, slitlamp microscopes were used in 88 articles (89%). The original or modified Krachmer grading scale was used in 77 articles (78%), followed by Adami's classification in six (6%). Specular microscopes or Scheimpflug tomography were used in four articles (4%) and anterior segment optical coherence tomography in one (1%). FECD is globally diagnosed by the corneal guttae using slitlamp examination, and its severity is predominantly determined by the original or modified Krachmer grading scale. Objective severity grading using Scheimpflug or anterior segment optical coherence tomography can be applied in the future innovative therapies such as cell injection therapy or novel small molecules.