Anand Aggarwal

Comparison of anterior segment optical coherence tomography and ultrasound biomicroscopy for assessment of the anterior segment

PURPOSE: To compare anterior segment parameters using quantitative imaging by anterior segment optical coherence tomography (AS‐OCT) and ultrasound biomicroscopy (UBM). SETTING: Tertiary‐care glaucoma research center. METHODS: Sixty‐three eyes of 63 subjects had anterior segment evaluation by AS‐OCT (Visante‐Zeiss) and UBM (Paradigm). Central corneal thickness (CCT), anterior chamber depth (ACD) (measured from the central corneal endothelium to the anterior lens capsule), and the peripheral iridocorneal angles (temporal and nasal) were assessed and compared. RESULTS: There was an excellent correlation between AS‐OCT and UBM measurements for the nasal angle (r = 0.84; P<.0001), temporal angle (r = 0.86; P<.0001), ACD (r = 0.97; P<.0001), and CCT (r = 0.91; P<.0001). There was no significant difference (paired t test) between the mean ACD, CCT, and angle parameters measured by AS‐OCT or UBM. The mean values of the parameters measured by AS‐OCT and UBM were, respectively, as follows: nasal angle, 26.25 degrees ± 11.0 (SD) and 28.27 ± 11.3 degrees (P = .3); temporal angle, 25.1 ± 11.4 degrees and 28.3 ± 13.5 degrees (P = .15); ACD, 2.85 ± 0.5 mm and 2.78 ± 0.5 mm (P = .2); and CCT, 512 ± 46 μm and 502 ± 46 μm (P = .25). The AS‐OCT images showed sharper definition of the scleral spur than the UBM images. CONCLUSION: Anterior segment optical coherence tomography and UBM can both be used for anterior segment measurements and yielded comparable results.

Post-penetrating keratoplasty glaucoma

To study the risk factors in the development of glaucoma following penetrating keratoplasty, we retrospectively analysed 190 eyes of 185 consecutive patients who had undergone surgery during 1990. The donor button was larger by 0.2 mm and 0.5 mm in phakia and aphakia/pseudophakia patients, respectively. Over a mean follow-up period of 14.5 months, 52 of the 190 eyes (27.4%) either developed glaucoma de novo or had worsening of preexisting glaucoma. Of these 52 eyes, 38 were managed medically and 14 required surgery. From our study, aphakia (37%), pseudophakia (24%), preexisting glaucoma (81.8%), and regrafting (43.18%) were found to be the significant risk factors in the development of glaucoma following penetrating keratoplasty.

Ultrasound biomicroscopy in opaque grafts with post-penetrating keratoplasty glaucoma.

Purpose: To evaluate the anterior segment in opaque grafts with post-penetrating keratoplasty glaucoma (PPKG) by using ultrasound biomicroscopy (UBM). Methods: An observational clinical case series of patients with opaque corneal grafts with PPKG who underwent UBM examination of the anterior chamber is reported. Indication for keratoplasty, lens status, intraocular pressure at the time of presentation, and the time of diagnosis of glaucoma were noted. Examination included slit-lamp biomicroscopy, posterior-segment ultrasound evaluation, and UBM evaluation of the anterior segment. Results: Thirty-one eyes of 31 patients with PPKG were recruited into the study. The mean intraocular pressure was 35.5 ± 5.8 mm Hg (range, 26-52 mm Hg). The mean time of follow-up after penetrating keratoplasty was 6.97 ± 2.98 months (range, 2-16 months). Of the 31 patients, 11 had undergone penetrating keratoplasty for therapeutic purposes (infectious keratitis), whereas the remaining 20 had undergone keratoplasty for optical reasons. Fourteen (45.1%) patients were pseudophakic, 13 (41.9%) were aphakic, and 4 (12.9%) were phakic. The types of synechiae noted on the UBM included peripheral anterior synechiae in 30/31 (96.7%) eyes, synechiae at the graft-host junction in 13/31 (41.93%) eyes, both peripheral anterior synechiae and graft-host junction synechiae in 12/31 (38.7%) eyes, central iridocorneal synechiae in 6/31 (19.3%) eyes, and intraocular lens iris synechiae in 3/31 (9.6%) eyes. Conclusions: Secondary angle closure caused by anterior synechiae formation is one of the important causes of PPKG in eyes with opaque grafts. UBM serves as a useful tool for anterior-segment evaluation in such cases and can help in planning the site for glaucoma filtering surgeries and drainage devices.

Management of acute corneal hydrops secondary to keratoconus with intracameral injection of sulfur hexafluoride (SF6).

Purpose: To report the use of sulfur hexafluoride (SF6) gas in the management of corneal edema caused by acute corneal hydrops secondary to keratoconus. Methods: Nine eyes with acute hydrops secondary to keratoconus managed by SF6 gas injected into the anterior chamber (group 1) were compared to another 9 eyes that were managed conservatively with conventional medical therapy (group 2). Results: Of 9 eyes in group 1, 3 had 1 injection, 4 had 2 injections, and the remaining 2 had 3 injections into the anterior chamber. All the eyes in group 1 showed an early resolution of corneal edema at 4 weeks. The same was achieved in group 2 at 12 weeks. The central corneal thickness (CCT) in group 1 and group 2 was >1.0 mm at presentation. The CCT at 3 and 12 weeks in group 1 was 0.99 and 0.65 mm, respectively, whereas CCT in group 2 at 3 weeks was >1.0 mm and at 12 weeks was 0.991 mm (P = 0.001). The mean best spectacle-corrected visual acuity (BSCVA) at 12 weeks in group 1 and group 2 was 0.39 and 0.24, respectively (P = 0.016). The results were significant in favor of group 1 over group 2 both in CCT and BSCVA. Conclusion: Early intervention with intracameral SF6 injection is a safe and effective therapy for early reduction of corneal edema in eyes with keratoconus and acute hydrops.

Sutureless single-port transconjunctival pars plana limited vitrectomy combined with phacoemulsification for management of phacomorphic glaucoma

&NA; We describe a technique that uses a small‐gauge, single‐port, sutureless transconjunctival limited pars plana vitrectomy to facilitate phacoemulsification in eyes with a shallow anterior chamber and high intraocular pressure (phacomorphic glaucoma). These eyes have positive vitreous pressure, and anterior chamber formation with an ophthalmic viscosurgical device may not be possible. Surgery is difficult and prone to various intraoperative complications.

Retinal nerve fiber layer thickness measurement by scanning laser polarimetry (GDxVCC) at conventional and modified diameter scans in normals, glaucoma suspects, and early glaucoma patients.

PurposeTo study the retinal nerve fiber layer (RNFL) at 3 different scan diameters using GDxVCC in healthy, primary open-angle glaucoma (POAG) suspects, and early POAG. MethodRNFL parameters were evaluated in 100 normal subjects, 50 POAG suspects, and 50 early POAG patients using GDxVCC at conventional small, medium, and large circle. TSNIT (temporal, superior, nasal, inferior, temporal) average, superior average, inferior average RNFL thickness, and nerve fiber indicator (NFI) were evaluated. ResultsThe TSNIT average (μm) in normal subjects, POAG suspects, and POAG at 3 different circles was 54.17±4.6, 49.96±6.5, 46.92±6.2 (small); 47.17±4.8, 43.79±5.7, 41.48±6.5 (medium); and 41.57±4.6, 39.77±5.9, 38.33±7.1 (large). All RNFL parameters at all circles showed significant difference between normal and early POAG eyes (P<0.001). Area under the curve was 0.911 for NFI at all circles. All parameters at small and medium circle, all except TSNIT average at large circle showed significant difference between normal and POAG suspects (P<0.001), area under curve being the highest (0.780 to 0.801 at 3 circles) for NFI. All parameters progressively decreased with increasing diameter with significant difference between small-medium (P<0.001), medium-large (P<0.001), and small-large circle results (P<0.001) in all the groups for all parameters except NFI. ConclusionsMedium and large circles can also be used for RNFL evaluation in glaucoma. NFI is the best discriminating measure across all scan diameters.

Evaluation of retinal nerve fiber layer thickness parameters in myopic population using scanning laser polarimetry (GDxVCC)

INTRODUCTION Myopia presents a significant challenge to the ophthalmologist as myopic discs are often large, tilted, with deep cups and have a thinner neuroretinal rim all of which may mimic glaucomatous optic nerve head changes causing an error in diagnosis. OBJECTIVE To evaluate the retinal fiber layer (RNFL) thickness in low, moderate and high myopia using scanning laser polarimetry with variable corneal compensation (GDxVCC). SUBJECTS AND METHODS One hundred eyes of 100 emmetropes, 30 eyes of low myopes (0 to - 4 D spherical equivalent(SE), 45 eyes with moderate myopia (- 4 to - 8D SE), and 30 eyes with high myopia (- 8 to - 15D SE) were subjected to retinal nerve fiber layer assessment using the scanning laser polarimetry (GDxVCC) in all subjects using the standard protocol. Subjects with IOP > 21 mm Hg, optic nerve head or visual field changes suggestive of glaucoma were excluded from the study. The major outcome parameters were temporal-superior-nasal-inferiortemporal (TSNIT) average, the superior and inferior average and the nerve fibre indicator (NFI). RESULTS The TSNIT average (p = 0.009), superior (p = 0.001) and inferior average (p = 0.008) were significantly lower; the NFI was higher (P less than 0.001) in moderate myopes as compared to that in emmetropes. In high myopia the RNFL showed supranormal values; the TSNIT average, superior and inferior average was significantly higher(p less than 0.001) as compared to that in emmetropes. CONCLUSION The RNFL measurements on scanning laser polarimetry are affected by the myopic refractive error. Moderate myopes show a significant thinning of the RNFL. In high myopia due to peripapillary chorioretinal atrophy and contribution of scleral birefringence, the RNFL values are abnormally high. These findings need to be taken into account while assessing and monitoring glaucoma damage in moderate to high myopes on GDxVCC.