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Glaucoma. Dr. Abdullah Al-Amri Ophthalmology Consultant. Contents. Anatomy and basic physiology. Definition of glaucoma. Classification of glaucoma. Gonioscopy. Measurement of IOP. Primary open angle Vs closed angle glaucoma. Management of glaucoma. Secondary glaucomas. Anatomy.
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Glaucoma Dr. Abdullah Al-Amri Ophthalmology Consultant
Contents • Anatomy and basic physiology. • Definition of glaucoma. • Classification of glaucoma. • Gonioscopy. • Measurement of IOP. • Primary open angle Vs closed angle glaucoma. • Management of glaucoma. • Secondary glaucomas.
Basic physiology • Aqueous is produced by secretion and ultrafiltration from the ciliary processes into the posterior chamber. • It then passes through the pupil into the anterior chamber to leave the eye predominantly via the trabecular meshwork, Schlemm’s canal and the episcleral veins (the conventional pathway).
A small proportion of the aqueous (4%) drains across the ciliary body into the supra-choroidal space and into the venous circulation across the sclera (uveoscleral pathway). • The intraocular pressure level depends on the balance between production and removal of aqueous humour.
Definition of glaucoma • The term glaucoma refers to a group of diseases that have in common a characteristic optic neuropathy with associated visual function loss. • Although elevated intraocular pressure (IOP) is one of the primary risk factors, its presence or absence does not have a role in the definition of the disease.
Three factors determine the lOP: • The rate of aqueous humor production by the ciliary body. • Resistance to aqueous outflow across the trabecular meshwork-Schlemm's canal system. • The level of episcleral venous pressure.
Measurement of IOP • Applanation tonometry is the method used most widely. • Measurement of lOP in a clinical setting requires a force that indents or flattens the eye.
The normal pressure is 15.5 mmHg. • The limits are defined as 2 standard deviations above and below the mean (11–21 mmHg).
Optic nerve cupping • Cupping is a normal feature of the optic disc. • The disc is assessed by estimating the vertical ratio of the cup to the disc as a whole (the cup to disc ratio). • In the normal eye the cup disc ratio is usually no greater than 0.4.
Primary open angle glaucoma • Affects 1 in 200 subjects over the age of 40. • Affecting males and females equally. • There may be a family history. • The prevalence among blacks is 3 to 4 times higher than whites. • Symptomless unless the patient becomes aware of a severe visual deficit.
Primary angle closure glaucoma • Affects 1 in 1000 subjects over 40 years. • Females more commonly affected than males. • Strong family history. • Prevalence is more common among Asians and Eskimos. • Patients are likely to be hyperopic. • In acute cases, patient may have sever pain, photophobia, vision loss and nausea.
On examination visual acuity is reduced, the eye is red, the cornea is cloudy and the pupil is oval, fixed and dilated.
Management of glaucoma • Medical treatment. • Laser treatment. • Surgical treatment.
Surgical treatment • Drainage surgery (trabeculectomy) relies on the creation of a fistula between the anterior chamber and the subconjunctival space. • The operation is usually effective in substantially reducing intraocular pressure. • It is performed increasingly early in the treatment of glaucoma.
Secondary glaucoma Open angle: Closed angle: Abnormal iris blood vessels may obstruct the angle and cause the iris to adhere to the peripheral cornea, closing the angle (rubeosis iridis). A large choroidal melanoma may push the iris forward. A cataract may pushing the iris forward (phacomorphic). Uveitis may cause the iris to adhere to the trabecular meshwork. • Blood (hyphema), following blunt trauma. • Inflammatory cells (uveitis). • Pigment from the iris. • Deposition of material produced by the epithelium of the lens, iris and ciliary body in the trabecular meshwork (pseudoexfoliative glaucoma). • Steroid-induced glaucoma. • Raised episcleral venous pressure.
