Horizontal Anterior Chamber Diameter Research Articles

Changes in corneal high order aberrations and anterior chamber parameters following scleral fixated intraocular lens implantation

BackgroundTo evaluate the change in corneal high order aberrations (HOAs) and anterior chamber parameters following scleral fixation in aphakic patients using the Scheimpflug camera system. MethodsThis retrospective study included patients who were aphakic after phacoemulsification surgery and underwent scleral-fixed intraocular lens (SF-IOL) implantation with Z suture technique between 2010 and 2022. Preoperative and postoperative best corrected visual acuity (BCVA), anterior segment parameters and corneal aberrations were evaluated with a combined Scheimpflug-Placido disk corneal topography device (Sirius Costruzione Strumenti Oftalmici, Florence, Italy). The following values were recorded: Simulated keratometry (SimK), flat meridian (K1), steep meridian (K2), iridocorneal angle (ICA), temporal anterior chamber angle (T-ACA), nasal anterior chamber angle (N-ACA), horizontal anterior chamber diameter (HACD), anterior chamber volume (ACV), corneal volume (CV), total Root Mean Square (RMS), high order aberrations (HOAs), spherical aberration, coma, trefoil, quadrifoil, and secondary astigmatism. ResultsThe study included 31 eyes of 31 patients (mean age: 63.00 ± 19.41 years, 17 males/14 females). Postoperative BCVA was better than preoperative BCVA (p = 0.012). Postoperatively, there was a statistically significant increase in ACV and CV values and a statistically significant decrease in K2 (p = 0.009, p = 0.032, p = 0.015). Preoperative T-ACA and preoperative and postoperative ACV were negatively correlated with postoperative intraocular pressure (r=-0.427 p = 0.033, r=-0.406 p = 0.032 and r=-0.561 p = 0.001). There were statistically significant postoperative increases in corneal RMS, trefoil and HOAs for 3 mm pupil diameter (p = 0.0177, p = 0.001, p = 0.031) and in corneal RMS, trefoil and quadrifoil aberrations for 6 mm pupil diameter (p = 0.033, p = 0.001, p = 0.001). ConclusionsIn conclusion, SF-IOL implantation with Z-suture technique used for visual rehabilitation of aphakic patients may affect visual quality by increasing corneal HOAs while improving visual acuity.

Evaluation of Eyelid, Angle, and Anterior Segment Parameters Using Scheimpflug Camera and Topography System in Obstructive Sleep Apnea Syndrome.

The purpose of the study was to investigate the eyelid hyperlaxity, anterior segment, and corneal topographic parameters in patients with obstructive sleep apnea syndrome (OSAS) using Scheimpflug camera and topography system. In this prospective and cross-sectional clinical study, 32 eyes of 32 patients with OSAS and thirty-two eyes of 32 healthy subjects were evaluated. The participants with OSAS were selected from those with an apnea-hypopnea index ≥ 15. The minimum corneal thickness (ThkMin), apical corneal thickness (ACT), central corneal thickness (CCT), pupillary diameter (PD), aqueous depth (AD), aqueous volume (AV), anterior chamber angle (ACA), horizontal anterior chamber diameter (HACD), corneal volume (CV), simulated K readings (sim-K), front and back corneal keratometric values at 3 mm, RMS/A values, highest point of ectasia on the anterior and posterior corneal surface (KVf, KVb), symmetry indices and keratoconus measurements were taken by combined Scheimpflug-Placido corneal topography and compared with healthy subjects. Upper eyelid hyperlaxity (UEH) and floppy eyelid syndrome were also evaluated. There were no statistically significant difference between groups in terms of age, gender, PD, ACT, CV, HACD, simK readings, front and back keratometric values, RMS/A-KVf and KVb values, symmetry indices, and keratoconus measurements (p>0.05). ThkMin, CCT, AD, AV, and ACA values were significantly higher in OSAS group compared to the control (p<0.05). UEH was detected in two cases in the control group (6.3%) and in 13 cases in the OSAS group (40.6%) and the difference was significant (p<0.001). The anterior chamber depth, ACA, AV, CCT, and UEH increase in OSAS. These ocular morphological changes occurring in OSAS may explain why these patients prones to normotensive glaucoma.

Commentary: Reliability, repeatability, and accuracy of Sirius topographer in assessing anterior segment morphology following laser peripheral iridotomy in primary angle-closure disease.

Commentary: Reliability, repeatability, and accuracy of Sirius topographer in assessing anterior segment morphology following laser peripheral iridotomy in primary angle-closure disease.

Changes in anterior chamber dimensions following small incision lenticule extraction (SMILE).

To evaluate the changes in anterior chamber dimensions including horizontal anterior chamber diameter (HACD), anterior chamber depth (ACD), and iridocorneal angle (ICA) following small incision lenticule extraction (SMILE) using Scheimpflug-Placido disk tomographer (Sirius). The records of the 73 eyes of 47 patients who received SMILE for myopia and myopic astigmatism were retrospectively reviewed. Preoperative and 6-month postoperative measurements of central corneal thickness (CCT), HACD, ACD, ICA, nasal anterior chamber angle (nACA), and temporal anterior chamber angle (tACA) were obtained by tomography, and compared with paired t-tests. Pearson's correlation and linear regression tests were used to evaluate the relationship between these parameters. The CCT, HACD, and ACD values decreased significantly at 6-month postoperatively (p < 0.05 for all). ICA, nACA, and tACA showed no statistically significant difference postoperatively (p = 0.54, p = 0.118, and p = 0.255, respectively). Pearson's correlation analysis confirms negative relationship between Δ-HACD and Δ-tACA (r = -0.475, p < 0.01), and a loose negative relationship between change in ACD and change in ICA (r = -0.282, p = 0.016). Age and Δ-tACA were found as predictive parameters for Δ-HACD and, Δ-ICA was a predictor for Δ-ACD. While HACD and ACD decreased significantly, there was no significant change in ICA, nACA and tACA. Changes in HACD and ACD should be considered in terms of subsequent surgeries after SMILE.

Assessment of corneal endothelial cell morphology and anterior segment parameters in COVID-19.

Background:The ocular manifestations of the 2019 novel coronavirus disease (COVID-19) vary from acute follicular, pseudomembranous, and hemorrhagic conjunctivitis to keratoconjunctivitis with subepithelial infiltrates and dendritic lesions. Similar to other respiratory viruses, such as adenoviruses, it is thought that COVID-19 may impact the cornea. However, its impact on the cornea and anterior segment parameters are currently poorly understood.Objective:This study aims to assess the corneal endothelial cell morphology and anterior segment parameters in patients who have recovered from COVID-19.Methods:In this cross-sectional study, the COVID-19 group comprised 34 patients who had been diagnosed with and recovered from COVID-19, while the control group comprised age- and sex-matched individuals without any systemic or ocular diseases. The endothelial cell density (ECD), coefficient of variation (CV) of cell area, hexagonal cell percentage (HEX), anterior chamber depth (ACD), central corneal thickness (CCT), horizontal anterior chamber diameter (HACD), iridocorneal angle (ICA), horizontal visible iris diameter (HVID), pupillary diameter (PD), and keratometry values (K1 and K2) were analyzed for each participant. The differences in each of these between the groups were analyzed using either an independent samples t test or a Mann–Whitney U test based on the normality of the data.Results:Regarding corneal endothelial cell morphology, the ECDs for the COVID-19 and control groups were 2278.50 ± 186.78 cells/mm2 and 2420.15 ± 222.25 cells/mm2, respectively (p = 0.002). A significant increase was noted in CV values in the COVID-19 group compared with the control group (p < 0.001). The HEX values for the COVID-19 and control groups were 56.26 ± 5.75 and 61.50 ± 3.63, respectively (p < 0.001). Regarding the anterior segment parameters, no significant differences were observed between the groups (p > 0.05).Conclusions:It was hypothesized that individuals who had recovered from COVID-19 would demonstrate a reduction in their endothelial functional preserves. A decrease in ECD and HEX and an increase in CV were observed in the individuals during their early post-recovery period from COVID-19.

Effects of a Single Dose of Topical Brimonidine 0.15% on Anterior Segment Morphology, Pupil Characteristics, and Choroidal Thickness in Healthy Subjects.

To investigate the effects of a single dose of brimonidine 0.15% on anterior segment morphology, pupil characteristics, and choroidal blood flow in treated and untreated eyes of healthy subjects and to compare the results obtained with those in another healthy volunteer group. Participants were classified as study and control groups. The eyes in the study group were randomized. Only one eye received one drop of brimonidine (treated eyes), and the contralateral eye received single dose of sodium hyaluronate (untreated eyes). In addition, only right eyes of control subjects, who had single dose of sodium hyaluronate to both eyes, were analyzed (control eyes). Anterior segment parameters including central corneal thickness (CCT), aqueous depth, anterior chamber volume, iridocorneal angle (ICA), horizontal anterior chamber diameter, and pupil measurements including scotopic, mesopic, photopic, and dynamic pupil diameters (PDs) were performed with Sirius Scheimpflug camera. Choroidal thickness (CT) measurements were taken with optical coherence tomography. These measurements were taken at baseline and repeated 1 hour after the dosing. Only the treated eyes had significantly thicker CCT and wider ICA values after instillation of brimonidine. Static and dynamic PD values of treated eyes and even untreated eyes significantly decreased after brimonidine. However, brimonidine has no significant effect on CT measurements. A single dose of brimonidine causes thickening in CCT and widening in ICA values in treated eyes. In addition, it has significant effect to decrease the scotopic, mesopic, photopic, and dynamic PD values in treated and even contralateral eyes while has no effect on choroidal blood flow.

Evaluation of anterior segment parameters in pars plana vitrectomy and silicone oil injection

Purpose The aim of this study was to compare the changes in anterior segment parameters induced by pars plana vitrectomy (PPV) and silicone oil injection in phakic and pseudophakic eyes.Patients and methods This is a prospective comparative study that included 40 eyes with rhegmatogenous retinal detachment that underwent vitrectomy and silicone oil injection. They were divided equally into two groups. Group 1 included phakic eyes and group 2 included pseudophakic eyes. Anterior segment parameters were documented by using a CSO Camera (Costruzione Strumenti Oftalmici) before and 1 month after surgery. The changes in the following parameters were compared between the two groups: anterior chamber depth (ACD), anterior chamber volume (ACV), anterior chamber angle (ACA), central corneal thickness (CCT), corneal volume (CV), horizontal anterior chamber diameter, and surgically induced astigmatism.Results At 1 month postoperatively, in group 1, there was a significant decrease in the mean of ACA and ACV as compared with the preoperative values (P=0.024 and 0.011, respectively). In group 2, there was a significant decrease in the 1-month postoperative mean of ACD, ACA, and ACV as compared with the preoperative values (P=0.021, <0.0001 and 0.015, respectively) and a significant increase in the mean of CCT and CV values (P<0.0001 and 0.002, respectively). In group 2, there was more reduction in ACD, less reduction in ACA, and higher increase in CCT and CV as compared with group 1 (P=0.021, 0.001, <0.0001, and 0.023, respectively).Conclusion The presence of the crystalline lens acts as a barrier which decreases the changes in the anterior segment parameters and improves the functional outcome following PPV and silicone oil injection as compared with pseudophakia. Therefore, it may be useful to stabilize the anterior segment in patients with PPV and silicone oil injection.

Does Dry Eye Affect Repeatability of Corneal Topography Measurements?

Objectives:The purpose of this study was to assess the repeatability of corneal topography measurements in dry eye patients and healthy controls.Materials and Methods:Participants underwent consecutive corneal topography measurements (Sirius; Costruzione Strumenti Oftalmici, Florence, Italy). Two images with acquisition quality higher than 90% were accepted. The following parameters were evaluated: minimum and central corneal thickness, aqueous depth, apex curvature, anterior chamber volume, horizontal anterior chamber diameter, iridocorneal angle, cornea volume, and average simulated keratometry. Repeatability was assessed by calculating intra-class correlation coefficient.Results:Thirty-three patients with dry eye syndrome and 40 healthy controls were enrolled to the study. The groups were similar in terms of age (39 [18-65] vs. 30.5 [18-65] years, p=0.198) and gender (M/F: 4/29 vs. 8/32, p=0.366). Intra-class correlation coefficients among all topography parameters within both groups showed excellent repeatability (>0.90).Conclusion:The anterior segment measurements provided by the Sirius corneal topography system were highly repeatable for dry eye patients and are sufficiently reliable for clinical practice and research.

Multivariate Analysis to Predict the Horizontal Anterior Chamber Diameter from Other Anterior Chamber Parameters Using Scheimpflug Imaging: Is There a Better Method Than Adding a Fixed Constant?

ABSTRACTPurpose: To evaluate the predictive association between the horizontal anterior chamber diameter (HACD) and other measurements using Scheimpflug imaging, and to assess whether a method superior to using fixed constants can be proposed.Methods: This hospital-based study was performed in the Cornea and Refractive Surgery Services, New Medical Center (NMC) specialty hospital, Abu Dhabi. Initially, 100 candidates were included serially in the model building group (group1). All candidates underwent detailed evaluation and Scheimpflug imaging (CSO, Sirus, Italy). Subsequently, another 100 candidates were included serially in the validation group (group 2). Candidates in both groups underwent the same tests.Results: In group 1, the mean HACD was 12.25 ± 0.48 mm. This measurement correlated significantly with the horizontal visible iris diameter (HVID), anterior chamber depth, angle (ACA), and volume (ACV) (r = 0.2–0.7). The overall regression equation was HACD = 5.62 + 0.01 × ACV + 0.45 × HVID − 0.013 × ACA (adjusted R2 = 0.66, p < 0.001). Situation-based equations derived from the outcomes of group 1 were tested in group 2. Equation A included all factors found significant during model-building, Equation B included only non-volumetric significant factors, and situation C only included the HVID. Equations D through F used direct substitution by HVID plus a constant to predict HACD (the constant was 0.0, 0.5, and 1.0 for Equations D, E, and F, respectively).The predicted HACD (pHACD) was within ±0.5 mm of the actual HACD (aHACD) in 93%, 88%, 87%, 83%, 69%, and 16% case for Equations A, B, C, D, E, and F, respectively. The mean prediction error was −0.14 ± 0.27 mm (p = 0.08), −0.15 ± 0.28 mm (p = 0.03), −0.18 ± 0.30 mm (p = 0.001), −0.18 ± 0.32 mm (p < 0.001), 0.33 ± 0.35 mm (p < 0.001), and 0.83 ± 0.35 mm (p < 0.001) for Equations A, B, C, D, E, and F, respectively.Conclusion: Regression equations using Scheimpflug-derived anterior chamber parameters may predict HACD to varying degrees, depending on the input parameters. Adding 0.5 or 1.0 mm to the corneal diameter (CD) to estimate the HACD is not recommended.

Quantitative Assessment of Anterior Chamber Parameters in Pigmentary Glaucoma Using Slit-Lamp Optical Coherence Tomography

To quantitatively assess the parameters of anterior chamber and angle dimensions by slit-lamp optical coherence tomography (SL-OCT) in eyes with pigmentary glaucoma (PG). A total of 18 eyes of 11 patients with PG and 18 eyes of 11 healthy volunteers were included in the study. Anterior chamber depth (ACD), anterior chamber volume (ACV), spur distance (internal horizontal anterior chamber diameter), central corneal thickness (CCT), angle opening distance at 500 microm from the scleral spur (AOD 500), and trabecular iris space area at 500 microm from the scleral spur (TISA 500) parameters were detected by SL-OCT. The differences of anterior chamber parameters between patients with PG and the control group were analyzed by Mann-Whitney U test. Mean ACD and ACV were measured as 3.28 +/- 0.38 mm and 191.6 +/- 39.7 mm3 respectively in the PG group. Mean AOD 500 and TISA 500 were 0.88 +/- 0.47 mm and 0.29 +/- 0.15 mm2 at the nasal angle and 1.14 +/- 0.67 mm and 0.41 +/- 0.23 mm2 at the temporal angle, respectively. Nasal and temporal angles were 49.83 +/- 11.1 degrees and 53.83 +/- 10.46 degrees. In eyes with PG, the midperipheral iris configuration was found to be considerably concave in 15 eyes (83.3%). Except CCT and spur distance, all anterior chamber dimension and angle parameters detected by SL-OCT were found to be significantly higher in the eyes with PG (Mann-Whitney U test, p < 0.05). CONCLUSIONS. SL-OCT provided highly quantitative data on the parameters of anterior chamber and angle dimensions in PG. The evaluation of the anterior segment anatomy using SL-OCT revealed increased anterior chamber dimensions and posterior bowing of the iris consistent with the increase in angle parameters in patients with PG.

Comparison of Internal Anterior Chamber Diameter Imaging Modalities: 35-MHz Ultrasound Biomicroscopy, Visante Optical Coherence Tomography, and Pentacam

To compare the internal diameter of the anterior chamber among three different imaging modalities: 35-MHz ultrasound biomicroscopy (UBM), Visante optical coherence tomography (OCT), and Pentacam, and to compare the internal diameters with white-to-white (WTW) distance measured by Orbscan. The internal horizontal anterior chamber diameter was measured in 20 normal eyes using 35-MHz UBM (Optikon), Visante OCT (Carl Zeiss Meditec), and Pentacam (Oculus Inc). The mean horizontal anterior chamber diameters were compared, and the correlations between each pair of two different methods were evaluated. Horizontal WTW distance was measured by Orbscan IIz (Bausch & Lomb-Orbtek Inc) and then correlated with the measurements of internal anterior chamber diameter. The mean horizontal anterior chamber diameter was 10.99+/-0.47 mm with UBM, 11.70+/-0.47 mm with OCT, and 11.86+/-0.45 mm with Pentacam. Ultrasound biomicroscopy measurements were significantly different than those of OCT and Pentacam (P<.001 for both). However, no significant difference was found between OCT and Pentacam (P=.19). Regarding the correlations between each pair of two different methods, UBM and OCT showed significant correlation (r=0.848, P<.001), but there was no significant correlation between OCT and Pentacam (r=0.403, P=.078), even though the mean values were similar. In the Bland-Altman plots, the range of agreement was 0.51 mm between OCT and UBM, and 0.99 mm between Pentacam and OCT. Although the internal anterior chamber diameters measured by 35-MHz UBM were significantly smaller than those measured by Visante OCT and Pentacam, the measurements of UBM and Visante OCT showed significant correlation and good agreement with each other. Pentacam showed poor correlation with other measurements.

Assessment and Comparison of Anterior Chamber Dimensions Using Various Imaging Techniques

To assess and compare the horizontal dimensions of the anterior chamber by different anterior segment imaging techniques. Eighty eyes of 40 patients without any ocular disease or previous ocular surgery were recruited and three consecutive measurements of internal anterior chamber diameter and white-to-white distance (WTW) parameters were determined. Mean internal anterior chamber diameter was 11.80 +/- 0.39, 11.56 +/- 0.47, and 11.61 +/- 0.58 mm with Visante-OCT, SL-OCT, and Pentacam, respectively. Mean WTW distance was 11.87 +/- 0.35 and 11.65 +/- 0.32 mm by IOLMaster and OrbscanIIz, respectively. There was no significant difference between Visante-OCT and Pentacam, IOLMaster, and OrbscanIIz (P = .125, .918, and .314). However, detection of mean internal anterior chamber diameter was significantly greater by Visante-OCT than SL-OCT (P = .026). All devices displayed a high intrasession repeatability (repeated measured ANOVA, P > .05). Internal anterior chamber diameter measurements using Visante-OCT, SL-OCT, and Pentacam, and WTW measurements using IOLMaster and OrbscanIIz were easy to handle and demonstrated good repeatability. Although similar results of horizontal anterior chamber diameter were determined by Visante-OCT, Pentacam, IOLMaster, and OrbscanIIz, the inter-device differences should be considered during clinical practice.

Internal anterior chamber diameter using optical coherence tomography compared with white-to-white distances using automated measurements

To compare internal horizontal anterior chamber (AC) diameter determined by optical coherence tomography (OCT) and horizontal corneal diameter (white-to-white [WTW]) using automated measurements. Department of Ophthalmology, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany. Internal AC diameter and WTW distance was measured in 52 eyes of 26 patients using the Visante OCT (Carl Zeiss Meditec), IOLMaster (Carl Zeiss Meditec), and Orbscan IIz topography system (Bausch & Lomb). Statistical evaluation was performed using the Bland-Altman method and regression analysis for comparison of measurement techniques. The Kruskal-Wallis test was used to measure the repeatability of each device. The mean internal AC diameter was 12.45 mm +/- 0.53 (SD) with OCT; the mean WTW distance was 12.17 +/- 0.45 mm with the IOLMaster and 11.84 +/- 0.41 mm with the Orbscan IIz. A positive regression was determined for AC diameter and both WTW measurements. Measurement values varied little between both WTW measurement systems (R(2) = 0.9384). Anterior chamber measurement using optical coherence tomography (Visante OCT) was easy to handle and showed good repeatability. The internal horizontal diameter of the AC was larger than the horizontal corneal diameter determined by automated WTW measurements (IOLMaster, Orbscan IIz). Optical coherence tomography with the Visante OCT allows direct measurement of the AC width.

Analyse du segment antérieur de l’œil avec un tomographe à cohérence optique: Étude statique et dynamique

To study the biometric modifications of the anterior segment depending on accommodation and age. To try and define their possible applications in certain fields of anterior segment surgery, in particular in refractive implants.Anterior chamber biometry can be very easily studied with 1310-nm wavelength optical coherence tomography. The equipment has a fixation target that can be focused and defocused with negative lenses in order to stimulate natural accommodation. The human anterior chamber was therefore studied during accommodation. We studied 104 eyes of 56 patients aged between 7 and 82 years. Refraction was between +5D and - 5D. A single operator carried out all the measurements. The anterior chamber's horizontal diameter, the anterior chamber's depth, the horizontal pupil diameter and the horizontal radius of curvature of the crystalline lens' anterior pole were measured unaccommodated or after stimulating accommodation.The different static or dynamic measurements were compared to ametropia, age and accommodation. At rest, the average AC diameter was 12.33 mm, the average AC depth was 3.11 mm and the average pupil diameter was 4.26 mm. On average, for 1 D of accommodation, the crystalline lens anterior pole moved forward by 30 microm. There was a 0.3-mm reduction in its radius of curvature and a 0.15-mm reduction in pupil diameter. Several other measurements are illustrated on graphs.The AC OCT is a user-friendly instrument to evaluate the anterior segment and explore the anterior chamber (cornea, iris, crystalline lens, irido-corneal angle). The 1310-nm light wavelength is blocked by pigments preventing exploration behind the iris. However, the AC OCT is capable of providing good-quality images and a better visualization of the anatomical relationships of the anterior segment, even behind an opaque cornea.