By/Mohamed Ahmed El Shafie
Assistant Lecturer in ophthalmology department KafrELShiekh University
4 What is glaucoma? Disease of the optic nerve.
When damage to the optic nerve fibersoccurs, blind spots develop; blind spotsusually go undetected until optic nerve issignificantly damaged.
Vision as it might beaffected by glaucoma
Anatomy of the drainage angleThe anterior chamber(AC) is that space, containing aqueous humor, which is bounded in front by the cornea and part of the sclera, and behind by the iris and part of the ciliary body. Its normal depth in adults varies from 2.5-3.5mm.The angle of the anterior chamber. refers to that peripheral recess bounded posteriorly by the root of the iris and the ciliary body and anteriorly by the corneo-scleral junction or the limbus. there is an annular channel, called the canal of Schlemm. The canal is separated from the aqueous in the anterior chamber by the trabecular meshwork.
Anatomy of glaucoma Clear liquid called aqueous humor circulates inside the frontportion of the eye.
To maintain a healthy level of pressure within the eye, a smallamount of aqueous humor is produced constantly, while an equalamount flows out of the eye through a microscopic drainagesystemthe trabecular meshwork.
Anatomy of glaucoma With glaucoma, aqueous humor does not flow through the trabecular meshwork properly.
Over time, eye pressure IOP increases, damaging the optic nerve fibers.
Types of glaucoma
Two main categories of glaucoma: Open-angle glaucoma: the most common form of glaucoma - (the most common form that affects approximately 95% of individuals)
Closed-angle glaucoma: a less common and more urgent form ofglaucoma.
Other Types of glaucoma:Normal-Tension GlaucomaCongenital glaucomaJuvenile glaucoma Secondary glaucoma
Classification of glaucoma.1-Angle configuration a-open(POAG=primary open angle glaucoma). b-Narrow/closed.(PACG=primary angle closure)
2-Onset a-acute(acute congestive glaucoma)red eye differential diagnosis. b-Chronic(primary open angle glaucoma)
3-Causes a-primary(POAG/PACG) or congenital/ developmental glaucoma. c-acquired/secondary glaucoma(secondary open angle and secondary close angle)
Secondary to other ocular diseases.neovascular glaucoma in CRVO or in diabetic eye diseaselens induced in neglected cataract.
Types of glaucoma Open-angleOpen-angle glaucoma
Trabecular meshwork becomes lessefficient at draining aqueous humor. Intraocular pressure (IOP) builds up,which leads to damage of the opticnerve. Damage to the optic nerve occurs atdifferent eye pressures amongdifferent patients.
Glaucoma risk factors Open-angle
Strong risk factors for open-angle glaucoma include:
High eye pressure (IOP) Family history of glaucoma Age 40 and older Thin cornea Suspicious optic nerve appearance with increased cupping (size of cup, the space at the center of optic nerve, is larger than normal) High myopia (severe nearsightedness) Diabetes Eye surgery or injury Use of corticosteroids (for example, eye drops, pills*, inhalers and creams)
Examination of the visual field
IOP depends on the relationship between aqueous production and outflow.
The normal ocular tension is between 10-21mm.Hg. There is a normal fluctuation in ocular tension of up to 3-5mm.Hg. during the course of the day called diurnal variation.
Digital palpation of ocular tension
Detecting GlaucomaTonometry:The tonometry eye test measures the inner pressure of the eye also known as Intraocular Pressure or IOP.
Indentation Tonometry: Schiotz tonometer
Types of Tonometry:Applanation tonometry measures intraocular pressure either by the force required to flatten a constant area of the cornea (e.g. Goldmann tonometry) or by the area flattened by a constant force.
Types of tonometrynon-contact tonometry or air-puff tonometry:This type of tonometer uses a rapid air pulse to applanate the cornea. Intraocular pressure is estimated by detecting the force of the air jet at the instance of applanation.
In most cases a stationary unit, Does not require anesthetic drops
Types of tonometryTono-pen - is a portable electronic, digital pen-like instrument that determines IOP by making contact with the cornea, after use of topical anesthetic eye drops tip covers are used between the patients.
Types of tonometry
The newest Advancement in tonometry is DIATON TONOMETER It measures intraocular pressure (IOP) through the Eyelid.Diaton Tonometer is intended for use by Inpatient & Outpatient Clinics such as Hospitals, Emergency Rooms, Nursing & Elderly Homes, General & Specialty Practitioners as well as Ophthalmologists and Optometrists. DIATON Requires No Contact with Cornea No Anesthetic Drops, No Risk of Infecting
Can be used on Children and Adults
Disc: damage usually begins as an upper or lower temporal notch, giving rise to a nasal arcuate scotoma,then progressive cupping can occur with progressive field lossFUNDOSCOPY
Examination technique used to visualize the structures of the anterior chamber angle. Mastering the various techniques of Gonioscopy is crucial in the evaluation of the Pathophysiology of aqueous humor outflow obstruction and the diagnosis of the various glaucomas.