Development in anterior segment imaging for glaucoma

Corneal higher-order aberrations in corneal endothelial decompensation secondary to obstetric forceps injury

Forceps corneal injuries during infant delivery cause Descemet membrane (DM) breaks, that cause corneal astigmatism and corneal endothelial decompensation. The aim of this study is to characterise corneal higher-order aberrations (HOAs) and corneal topographic patterns in corneal endothelial decompensation due to obstetric forceps injury. This retrospective study included 23 eyes of 21 patients (54.0 ± 9.0 years old) with forceps corneal injury, and 18 healthy controls. HOAs and coma aberrations were significantly larger in forceps injury (1.05 [0.76-1.98] μm, and 0.83 [0.58-1.69], respectively) than in healthy controls (0.10 [0.08-0.11], and 0.06 [0.05-0.07], respectively, both P < 0.0001). Patient visual acuity was positively correlated with coma aberration (r_s = 0.482, P = 0.023). The most common topographic patterns were those of protrusion and regular astigmatism (both, six eyes, 26.1%), followed by asymmetric (five eyes, 21.7%), and flattening (four eyes, 17.4%). These results indicate that increased corneal HOAs are associated with decreased visual acuity in corneal endothelial decompensation with DM breaks and corneal topography exhibits various patterns in forceps injury.

Evaluations of bridging sutures in preventing iris capture in eyes with intrascleral fixation of implanted intraocular lens

PURPOSE

The study aims to determine the effectiveness of bridging sutures in preventing iris capture and a subsequent reverse pupillary block after an intrascleral fixation of an implanted intraocular lens (IOL).

METHODS

We studied 6 eyes that had an iris capture with reverse pupillary block due to a dislocated IOL after an intrascleral fixation. After the dislocated IOL was repositioned, 10-0 polypropylene sutures were inserted 1.5 mm posterior to the limbus and directed to run between the iris and the IOL. The sutures were placed orthogonal to the haptics of the IOL. Anterior segment optical coherence tomography (AS-OCT) was used in 4 eyes to evaluate the degree of iridodonesis before and after the bridging sutures. The heights of the temporal and nasal sectors of the middle iris from the iris plane (the line between anterior chamber angles) were compared for each 0.2-s AS-OCT image taken immediately after the eye moved from a lateral to a primary position.

RESULTS

None of the eyes had a recurrence of the iris capture after the bridging sutures. The refractive error, anterior chamber depth, and vision were not significantly altered after the bridging sutures were placed. The AS-OCT images showed that the height of the nasal iris was decreased more at 0 s postoperatively blocking the excessive downward movement of the nasal iris but not the iridodonesis.

CONCLUSION

Bridging sutures were effective in preventing iris capture and subsequent reverse pupillary block after an intrascleral fixation of an IOL.

Large Amplitude Iris Fluttering Detected by Consecutive Anterior Segment Optical Coherence Tomography Images in Eyes with Intrascleral Fixation of an Intraocular Lens

Saccadic eye movements induce movements of the aqueous and vitreous humor and iris fluttering. To evaluate iris fluttering during eye movements, anterior segment optical coherence tomography (AS-OCT) was used in 29 eyes with pars plana vitrectomy (PPV) and intrascleral fixation of an intraocular lens (ISF group) and 15 eyes with PPV and an IOL implantation into lens capsular bag (control group). The height of the iris from the iris plane (the line between the anterior chamber angles) was compared every 0.2 s after the eye had moved from a temporal to the primary position (time 0). The height of the nasal iris in the ISF group decreased to −0.68 ± 0.43 mm at 0 s (p < 0.001) and returned to −0.06 ± 0.23 mm at 0.2 s. The height of the temporal iris increased to 0.45 ± 0.31 mm at 0 s (p < 0.001) and returned to −0.06 ± 0.18 mm at 0.2 s. The height of the nasal iris at 0 s in the ISF group was significantly lower, and that of the temporal iris was significantly higher than the control (−0.05 ± 0.09 mm, 0.03 ± 0.06 mm, p < 0.001, respectively). Iris fluttering can act as a check valve for aqueous and vitreous humor movements and can be quantified by consecutive AS-OCT images. Large amplitude iris fluttering in eyes with intrascleral fixation is important because it can lead to a reverse pupillary block.

Automated iris volume analysis and trabecular meshwork length using anterior segment optical coherence tomography - Application in pseudoexfoliation and pseudoexfoliation glaucoma

Purpose:

The aim of this study was to evaluate differences in the iris and angle parameters in psuedoexfoliation syndrome (PXF) and pseudoexfoliation glaucoma (PXG) using anterior segment optical coherence tomography (ASOCT).

Methods:

Patients with PXF or PXG were compared using ASOCT with primary open-angle glaucoma POAG eyes as controls in this noninterventional comparative study conducted at a tertiary eye care center in East India. All angle parameters, TM length, and iris thickness were analyzed from the enhanced depth imaging (EDI) single scans obtained. Quadrant scans were used for the calculation of iris volume using a custom-built in-house software. In particular, the software performs multiple operations including edge detection, connected components, and thresholding to localize and segment the iris. Differences in the iris volume/thickness and TM length in PXF and PXG with POAG were analyzed.

Results:

A total of 225 eyes were included, which included 75 PXG and 98 PXF cases and 52 POAG with a mean age of 67 ± 9.7 years at presentation. The algorithm repeatability and reproducibility was also established with correlation coefficients more than 99% which was substantiated with Bland-Altman plots. The iris volume (calculated in 197 images of 225 eyes) did not differ significantly in PXF and PXG eyes, although both had significantly greater volume compared to POAG eyes. The iris volume or other angle parameters including TM length did not correlate with clinical variables such as IOP, age, or visual field indices.

Conclusion:

Iris parameters or TM length do not explain pathogenesis of glaucoma in pseudoexfoliation.

Assessment of the anterior segment of patients with primary congenital glaucoma using handheld optical coherence tomography

PURPOSE

To investigate the potential of handheld optical coherence tomography (HH-OCT) in assessing the anterior segment of the eye in patients with primary congenital glaucoma.

DESIGN

A prospective, case-controlled observational study.

PARTICIPANTS

Twenty-two patients with primary congenital glaucoma (PCG, 9 females and 13 males; mean age 4.36 ± 3.4 years) and age-, gender- and ethnicity-matched healthy participants.

METHODS

Anterior OCT was performed in all participants using a high-resolution HH SD-OCT device (Envisu 2300, Leica Microsystems, Germany) without anaesthesia or sedation.

RESULTS

Anterior HH-OCT in PCG visualised Haab's striae in 14.3%, uneven internal cornea in 9.5% and epithelial thickening in 11.9% of patients with central corneal thickening (CCT, p < 0.001). CCT was significantly correlated with the intraocular pressure (IOP, p < 0.001). The flat iris with a thin collarette zone was found in 59.5%, anterior iris insertion in 11.90% of eyes affected by PCG. Two independent examiners showed sensitivity and specificity of 87% and 77%, respectively, by instating iris thinning and flattening of the anterior profile.

CONCLUSIONS

Anterior HH-OCT has significant potential to improve diagnosis and management of PCG. Clinically relevant information can be obtained non-invasively and without sedation. High specificity makes anterior HH-OCT an important adjunct for management of PCG. Excellent visualisation of the iris insertion on OCT indicates potential for AS OCT to assist with surgical planning, including decision on the type of surgery and location of the incision.

Agreement of Anterior Segment Parameters Obtained From Swept-Source Fourier-Domain and Time-Domain Anterior Segment Optical Coherence Tomography

Purpose

To assess the interdevice agreement between swept-source Fourier-domain and time-domain anterior segment optical coherence tomography (AS-OCT).

Methods

Fifty-three eyes from 41 subjects underwent CASIA2 and Visante OCT imaging. One hundred eighty–degree axis images were measured with the built-in two-dimensional analysis software for the swept-source Fourier-domain AS-OCT (CASIA2) and a customized program for the time-domain AS-OCT (Visante OCT). In both devices, we examined the angle opening distance (AOD), trabecular iris space area (TISA), angle recess area (ARA), anterior chamber depth (ACD), anterior chamber width (ACW), and lens vault (LV). Bland-Altman plots and intraclass correlation (ICC) were performed. Orthogonal linear regression assessed any proportional bias.

Results

ICC showed strong correlation for LV (0.925) and ACD (0.992) and moderate agreement for ACW (0.801). ICC suggested good agreement for all angle parameters (0.771–0.878) except temporal AOD500 (0.743) and ARA750 (nasal 0.481; temporal 0.481). There was a proportional bias in nasal ARA750 (slope 2.44, 95% confidence interval [CI]: 1.95–3.18), temporal ARA750 (slope 2.57, 95% CI: 2.04–3.40), and nasal TISA500 (slope 1.30, 95% CI: 1.12–1.54). Bland-Altman plots demonstrated in all measured parameters a minimal mean difference between the two devices (−0.089 to 0.063); however, evidence of constant bias was found in nasal AOD250, nasal AOD500, nasal AOD750, nasal ARA750, temporal AOD500, temporal AOD750, temporal ARA750, and ACD. Among the parameters with constant biases, CASIA2 tends to give the larger numbers.

Conclusions

Both devices had generally good agreement. However, there were proportional and constant biases in most angle parameters. Thus, it is not recommended that values be used interchangeably.

Anterior Segment Imaging for Angle Closure

PURPOSE

To summarize the role of anterior segment imaging (AS-imaging) in angle closure diagnosis and management, and the possible advantages over the current standard of gonioscopy.

DESIGN

Literature review and perspective.

METHODS

Review of the pertinent publications with interpretation and perspective in relation to the use of AS-imaging in angle closure assessment focusing on anterior segment optical coherence tomography and ultrasound biomicroscopy.

RESULTS

Several limitations have been encountered with the reference standard of gonioscopy for angle assessment. AS-imaging has been shown to have performance in angle closure detection compared to gonioscopy. Also, imaging has greater reproducibility and serves as better documentation for long-term follow-up than conventional gonioscopy. The qualitative and quantitative information obtained from AS-imaging enables better understanding of the underlying mechanisms of angle closure and provides useful parameters for risk assessment and possible prediction of the response to laser and surgical intervention. The latest technologies-including 3-dimensional imaging-have allowed for the assessment of the angle that simulates the gonioscopic view. These advantages suggest that AS-imaging has a potential to be a reference standard for the diagnosis and monitoring of angle closure disease in the future.

CONCLUSIONS

Although gonioscopy remains the primary method of angle assessment, AS-imaging has an increasing role in angle closure screening and management. The test should be integrated into clinical practice as an adjunctive tool for angle assessment. It is arguable that AS-imaging should be considered first-line screening for patients at risk for angle closure.

Retinal nerve fibre layer and ganglion cell complex thickness in patients with keratoconus

Background: Keratoconus, a corneal ectasia, is associated with corneal thinning and altered optical media. Consequently, assessment of the visual field, optic nerve head and intraocular pressure measurements may be challenging in patients with keratoconus. Few studies have investigated posterior segment variables including the retinal nerve fibre layer (RNFL) and ganglion cell complex (GCC) thickness in patients with keratoconus.Aim: To investigate RNFL and GCC thickness in patients with keratoconus.Methods: A comparative quantitative research design was used. The sample consisted of 56 participants (28 with mild, moderate or severe keratoconus, and 28 controls) who accessed the optometry clinic at the University of KwaZulu-Natal. There was an equal distribution of male (n = 14) and female (n = 14) participants in the keratoconus and control groups. Most participants were black (n = 34) or Indian (n = 18). Corneal power and refractive error were assessed with the Oculus Keratograph and subjective refraction respectively. The iVue-100 optical coherence topography device was used to measure RNFL and GCC thickness. Data were analysed by descriptive and inferential statistics.Results: The mean global RNFL thickness was slightly higher in the control group than the keratoconus group for the right (106 µm vs. 99 µm) and left (103 µm vs. 98 µm) eyes but these differences were not significant (p ≥ 0.057). For all RNFL quadrants, slightly lower mean RNFL measurements were found in the keratoconus group. The mean GCC thicknesses were marginally higher (3 µm – 6 µm) in the control group.Conclusion: The RNFL and GCC thickness differences between patients with keratoconus and controls are not clinically significant. Therefore, abnormally reduced RNFL and GCC thickness measurements in patients with keratoconus warrant further investigation for other pathologies specifically glaucoma.

Corneal Higher-order Aberrations and Visual Improvement Following Corneal Transplantation in Treating Herpes Simplex Keratitis

PURPOSE

To examine corneal higher-order aberrations (HOAs) and visual improvement following corneal transplantation in treating corneal scar caused by herpes simplex keratitis (HSK).

DESIGN

Retrospective consecutive case series.

METHODS

This study included a total of 52 eyes: 18 eyes of normal subjects, and 34 eyes of consecutive patients with corneal scar owing to HSK who underwent penetrating keratoplasty (PKP, 17 eyes) or deep anterior lamellar keratoplasty (DALK, 17 eyes). HOAs of the anterior, posterior surfaces and the total cornea were analyzed by anterior segment optical coherence tomography. The correlations between corneal HOAs and visual improvement were also analyzed.

RESULTS

Mean logarithm of the minimal angle of resolution (logMAR) visual acuity significantly improved from 1.40 ± 0.70 to 0.46 ± 0.45 after corneal transplantation (P < .0001). Mean corneal HOAs of the anterior surface significantly decreased after corneal transplantation (PKP: from 1.16 ± 0.59 μm to 0.58 ± 0.35 μm, P = .035, DALK: from 0.94 ± 0.57 μm to 0.37 ± 0.18 μm, P = .004). Visual acuity following corneal transplantation was correlated with the corneal HOAs at 12 months (r = 0.53, P = .01). Visual improvement at 3, 6, and 12 months was positively correlated with preoperative HOAs of the total cornea and posterior surface (all P < .01).

CONCLUSIONS

Preoperative corneal HOAs were associated with the visual improvement in treating corneal scar caused by HSK. Thus, the preoperative assessment of corneal HOAs, especially of the posterior surface, is important in the decision to perform corneal transplantation in eyes with HSK.

Corneal Higher-Order Aberrations in Infectious Keratitis

PURPOSE

To characterize the corneal higher-order aberrations (HOAs) in eyes with Acanthamoeba keratitis (AK), bacterial keratitis (BK), and fungal keratitis (FK).

DESIGN

Retrospective consecutive case series.

METHODS

This retrospective study includes 18 normal subjects and 63 eyes of 62 consecutive patients with corneal scarring due to AK (20 eyes), BK (35 eyes), and FK (8 eyes) from 2010 to 2016. HOAs of the anterior and posterior surfaces and the total cornea were analyzed by anterior segment optical coherence tomography. Corneal HOA patterns were assigned on the basis of corneal topography maps. Corneal opacity grading was assigned on the basis of slit-lamp examinations. We evaluated corneal HOAs, corneal opacity grading, and their correlation with visual acuity.

RESULTS

HOAs of the total cornea within a 4-mm diameter were significantly larger in eyes with infectious keratitis (AK, 1.15 ± 2.06 μm; BK, 0.91 ± 0.88 μm; FK, 1.39 ± 1.46 μm) compared with normal controls (0.09 ± 0.01 μm, all, P < .001). Asymmetric pattern was the most common topographic pattern (30% in AK, 51.4% in BK, and 37.5% in FK), followed by the protrusion patterns (10% in AK, 20% in BK, and 12.5% in FK). The visual acuity significantly correlated with HOAs (anterior surface: R = 0.764, P < .0001; posterior surface: R = 0.745, P < .0001; total cornea: R = 0.669, P < .0001).

CONCLUSIONS

Larger corneal HOAs in patients with infectious keratitis were associated with poorer visual acuity values. Asymmetric pattern was the most common topographic pattern in infectious keratitis.

Changes in Anterior Segment Morphology of Iris Bombe before and after Laser Peripheral Iridotomy in Patients with Uveitic Secondary Glaucoma

Purpose. To quantify changes in anterior segment (AS) parameters after laser peripheral iridotomy (LPI) using AS-optical coherence tomography (OCT) of iris bombe. Method. AS images of eight eyes were captured before and after iris bombe and more than 2 weeks after LPI (post-LPI) using AS-OCT. We compared the following AS parameters: anterior chamber depth (ACD), anterior chamber volume (ACV), iris curvature (IC), iris thickness at 500 μm from the scleral spur (IT-1) in the middle between the iris root and pupillary margin (IT-2) and 500 μm from the pupillary margin (IT-3) to the anterior chamber angle (ACA) (angle opening distance [AOD750]), and trabecular iris space area. Results. Mean IT-1 and IT-3, but not IT-2, were lower after iris bombe (IT-1, P = 0.001; IT-2, P = 0.081; and IT-3, P = 0.001). There were no significant differences between ACD at pre-LPI and before iris bombe (P = 0.096). The mean ACV and AOD750 of iris bombe increased at post-LPI (ACV, P < 0.01, and AOD750, P < 0.05). The mean IT-1, IT-2, and IT-3 increased at post-LPI (all, P ≤ 0.01). IC decreased at post-LPI (P < 0.001), and ACD at post-LPI did not change. Conclusions. The iris extends and becomes thinner during iris bombe. LPI during bombe decreases the IC and increases the ACV and ACA.

Corneal Higher Order Aberrations in Granular, Lattice and Macular Corneal Dystrophies

Purpose

To evaluate the corneal higher-order aberrations (HOAs) in granular, lattice and macular corneal dystrophies.

Methods

This retrospective study includes consecutive patients who were diagnosed as granular corneal dystrophy type2 (GCD2; 121 eyes), lattice corneal dystrophies type 1, type 3A (LCDI; 20 eyes, LCDIIIA; 32 eyes) and macular corneal dystrophies (MCD; 13 eyes), and 18 healthy control eyes. Corneal HOAs were calculated using anterior segment optical coherence tomography, and the correlations between HOAs and visual acuity were analyzed.

Results

HOAs of the total cornea within 4 mm diameter were significantly larger in GCD2 (0.17 ± 0.35 μm), in LCDI (0.33 ± 0.27), LCDIIIA (0.61 ± 1.56) and in MCD (0.23 ± 0.18), compared with healthy controls (0.09 ± 0.02μm, all P < 0.01). HOAs of the total cornea within 6 mm diameter were significantly larger in GCD2 (0.32 ± 0.48), in LCDI (0.60 ± 0.46), LCDIIIA (0.83 ± 2.29) and in MCD (0.44 ± 0.24), compared with healthy controls (0.19 ± 0.06, all P < 0.001). In GCD2, there was no significant correlation between logMAR and HOAs (r = 0.113, P = 0.227). In MCD, LCDI and LCDIIIA, logMAR was positively significantly correlated with HOAs (r = 0.620 and P = 0.028, r = 0.587 and P = 0.007, r = 0.614 and P < 0.001, respectively).

Conclusions

Increased HOAs occur in eyes with corneal dystrophies, especially in eye with LCD and MCD. Larger amount corneal HOAs are associated with poorer visual acuity in patients with LCD and MCD.