Related Experiment Video
Updated: Jun 25, 2025
07:11
Assessing Early Stage Open-Angle Glaucoma in Patients by Isolated-Check Visual Evoked Potential
Published on: May 25, 2020
6.3K
Contrast Discrimination and Global Form Perception in Primary Open-Angle Glaucoma and Primary Angle-Closure Glaucoma
Siddharth K Karthikeyan1, Allison M McKendrick2,3,4, Vijaya H Pai5
1Department of Optometry, Manipal College of Health Professions, Manipal Academy of Higher Education, Manipal, Karnataka, India.
Investigative Ophthalmology & Visual Science
|May 21, 2024
Summary
Primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG) patients show impaired visual processing. POAG patients performed worse on form perception tasks than PACG patients with similar visual field loss.
Area of Science:
- Ophthalmology
- Visual Neuroscience
- Medical Imaging
Background:
- Glaucoma, a group of optic neuropathies, affects millions worldwide.
- Primary open-angle glaucoma (POAG) and primary angle-closure glaucoma (PACG) are distinct subtypes with varying pathophysiologies.
- Understanding visual processing deficits in glaucoma subtypes is crucial for early detection and management.
Purpose of the Study:
- To investigate early and intermediate visual processing in POAG and PACG.
- To compare contrast discrimination and global form perception between POAG and PACG subtypes.
- To correlate visual processing abilities with visual field defect severity in glaucoma patients.
Main Methods:
- Contrast discrimination task (Porkorny and Smith, 1997) and global form perception task (glass pattern coherence thresholds) were employed.
- Visual processing thresholds were measured centrally and in the mid-periphery (12.5°) in unaffected visual field quadrants.
- Sixty participants (20 POAG, 20 PACG, 20 controls) aged 50-77 were recruited, with matched visual field defect severity between glaucoma groups.
Main Results:
- Both POAG and PACG groups exhibited significantly higher thresholds for contrast discrimination and global form perception compared to controls.
- No significant difference in contrast discrimination thresholds was found between POAG and PACG.
- POAG patients demonstrated significantly higher thresholds (worse performance) in global form perception compared to PACG patients.
Conclusions:
- Individuals with POAG show more pronounced deficits in intermediate visual processing (form perception) than those with PACG, even with similar visual field severity.
- These findings suggest that POAG may involve more extensive functional damage impacting higher-level visual processing compared to PACG.
- Further research is warranted to elucidate the specific neural mechanisms underlying these differential visual processing deficits in glaucoma subtypes.
More Related Videos
13:47Laser Capture Microdissection of Highly Pure Trabecular Meshwork from Mouse Eyes for Gene Expression Analysis
Published on: June 3, 2018
9.3K
08:55Translaminar Autonomous System Model for the Modulation of Intraocular and Intracranial Pressure in Human Donor Posterior Segments
Published on: April 24, 2020
3.0K
Related Concept Videos
01:28Angle Closure Glaucoma: Treatment
479
Angle-closure glaucoma, or closed-angle glaucoma, is an eye condition where the iris bulges out and blocks the iridocorneal angle, resulting in a buildup of aqueous humor and increased intraocular pressure. Immediate medical attention is necessary due to the sudden onset of symptoms. The treatment for angle-closure glaucoma includes short-term and long-term approaches. Short-term treatment involves using eye drops like pilocarpine to lower intraocular pressure by increasing aqueous humor...
479
01:27Open Angle Glaucoma: Treatment
430
In open-angle glaucoma, the iridocorneal angle remains open, but the trabecular meshwork becomes stiff, slowing down the outflow of aqueous humor. This causes a buildup of aqueous humor in the anterior chamber, leading to a sudden increase in intraocular pressure. The treatment for open-angle glaucoma focuses on reducing the elevated intraocular pressure by either decreasing the secretion of aqueous humor or increasing its outflow.
Drugs such as carbonic anhydrase inhibitors, α2- and...
Drugs such as carbonic anhydrase inhibitors, α2- and...
430
01:25Glaucoma: Overview
548
Glaucoma is an eye condition characterized by increased intraocular pressure that damages the retina and optic nerve, leading to irreversible blindness if left untreated. The human eye has various components, including the cornea, iris, pupil, lens, and optic nerve. Aqueous humor is secreted by the epithelium of the ciliary body in the posterior chamber and flows through the trabecular meshwork and canal of Schlemm, maintaining normal intraocular pressure. The trabecular meshwork and the canal...
548
01:22Photoreceptors and Visual Pathways
6.0K
At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category,...
6.0K
01:16Focusing of Light in the Eye
2.7K
Light rays enter the eye through the cornea, a transparent dome-shaped tissue that is the eye's outermost layer. The cornea bends or refracts, light rays traveling to the pupil. The shape of the cornea determines how much of the light is bent and whether the image will be focused correctly on the retina at the back of the eye. Once the light has passed through both refraction layers, it converges into a single focal point onto a small area. This is where photoreceptors start transforming...
2.7K