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Ocular Irritation Testing
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
George P. Daston, F. E. Freeberg
Swelling of the corneal stroma is a typical early response to irritant exposure. Burton47 described a method to measure corneal thickness (pachymetry) using a depth-measuring attachment on a slit-lamp microscope. He used the ratio of corneal thickness at the corneal apex after the instillation of an irritant to the preexposure thickness as an index of irritation. Burton found that there is a strong positive correlation between corneal thickness and the Draize scores for corneal opacity, overall corneal irritation, and overall conjunctival irritation (although corneal swelling had apparently reached a maximum when conjunctival irritation was only moderate). Furthermore, subtle differences in corneal thickness were measured in eyes which would have been given the same subjective Draize score. Thus, corneal thickness measurement may be a more powerful method for ranking the relative irritancies of similar materials.
Glaucoma
Published in Mary E. Shaw, Agnes Lee, Ophthalmic Nursing, 2018
Perimetry, posterior-segment examination and applanation tonometry are carried out to diagnose and monitor the disease. Corneal pachymetry is also performed to determine the thickness of the cornea.
SKILL Corneal shape, structure and thickness
Published in Sam Evans, Patrick Watts, Ophthalmic DOPS and OSATS, 2014
There are several techniques for the measurement of corneal thickness. The trainee should be aware of these; however, the most commonly used is ultrasound pachymetry. Historically, the most frequently used were optical systems, and these still exist. As more modern ophthalmic imaging techniques proliferate, the task of pachymetry may fall to optical coherence tomography (OCT), Scheimpflug cameras, confocal microscopy or corneal waveform (a variation of ultrasonic techniques).
Corneal Biomechanics Assessment with Ultra High Speed Scheimpflug Camera in Primary Open Angle Glaucoma Compared with Healthy Subjects: A meta-analysis of the Literature
Published in Current Eye Research, 2023
Fiammetta Catania, Emanuela Morenghi, Pietro Rosetta, Vinciguerra Paolo, Riccardo Vinciguerra
CCT was acquired with different methods in the considered studies. Wang et al.22 and Pradhan et al.24 reported CCT derived from Corvis ST measurement, Vinciguerra et al.25 and Salvetat et al.27 used ultrasound pachymetry, Coste et al.26 measured pachymetry using optical coherence tomography (OCT Visante, Zeiss) and Tian et al.23 considered data derived from Scheimpflug corneal tomography (Pentacam, OCULUS). Mean CCT of the healthy control population ranged from 528 ± 29 to 554 ± 35 µm while mean CCT in the POAG population varied from 522 ± 31 to 557 ± 39 µm. The overall analysis did not detect any statistically significant difference in the healthy and POAG population as concerns CCT (p = .532, see Table 2).
Periventricular leukomalacia mimicking normal-tension glaucoma: a case report
Published in Clinical and Experimental Optometry, 2021
Zeynep Kayaarasi Ozturker, Serpil Akar
On orthoptic evaluation with glasses, the patient had 10 prism dioptres esotropia at distance and 5 prism dioptres dissociated vertical deviation in the right eye and 10 prism dioptres dissociated vertical deviation in the left eye at distance. Her best-corrected visual acuity, with spectacle correction of +1.25/-1.25 X 25 in the right eye and +4.25/-4.50 X 180 in the left eye, was 6/6 in each eye. Upon detection of bilateral large optic disc cupping, the patient was referred to the glaucoma unit for a detailed evaluation. In slitlamp examination, the cornea was transparent, and the anterior chamber was normal. Intraocular pressure with Goldmann applanation tonometer was 16 mmHg in each eye. Pachymetry showed normal corneal thickness of 560 microns on the right and 577 microns on the left eye. Gonioscopic examination showed bilateral grade 3 to 4 open angles with two positive pigmentation without peripheral anterior synechia. Examination of the fundus revealed a vertical cup-disc ratio of 0.75 in the right eye, and 0.70 in the left eye (Figure 1A). No optic disc pallor was present. In 30-2 SITA Standard visual field test, there were bilateral homonymous defects in the lower quadrants that respect the horizontal midline (Figure 1B). Optical coherence tomography (OCT) showed bilateral superior retinal nerve fibre layer (RNFL) thinning. Among the disc parameters, optic disc area was 2.07 mm2 on the right eye and 1.85 mm2 on the left eye. Macular ganglion cell complex (GCC) analysis showed correlated thinning of the ganglion cell layer, most pronounced in the left eye (Figure 1C).
Corneal ectasia associated with posterior lamellar opacification
Published in Ophthalmic Genetics, 2021
Madeline Yung, Angela C. Chen, Doug D. Chung, Alice Barrington, Junwei Zhang, Ricardo F. Frausto, Otavio A. Magalhaes, Anthony J. Aldave
On examination, CDVA measured 20/30 OD and 20/40 OS. Slit lamp examination revealed conjunctival papillae and bilateral grayish opacification of the inferocentral posterior corneal stroma, which corresponded to the site of maximal corneal thinning and appeared as posterior lamellar hyperreflectivity on AS-OCT (Figure 1(a-d)). Corneal tomographic imaging demonstrated inferior conical corneal steepening in both eyes with Kmax of 47.4 D OD and 55.0 D OS (Figure 1(e-f)). Central corneal thickness measured by ultrasound pachymetry was 360 µm OD and 382 µm OS. Progression of corneal steepening and stromal thinning in the right eye was noted during a follow-up period of 14 months. Based on the ophthalmic history, clinical course, and tomographic findings, the patient was diagnosed with keratoconus. Genetic testing for PACD and BCS was offered to the patient, who failed to provide a sample.