3. Gradual Loss of Vision Flashcards
(174 cards)
1
Q
How does gradual loss of vision typically present in terms of speed and sensation?
A
Gradual loss of vision usually presents as a slowly-progressive and painless deterioration in vision.
2
Q
Is gradual loss of vision usually unilateral or bilateral?
A
It is usually bilateral, although it may be asymmetrical, with one eye affected more than the other.
3
Q
Over what time frame does vision loss occur in gradual vision deterioration?
A
Vision loss typically occurs over weeks to years, rather than hours or days.
4
Q
What distinguishes gradual vision loss from acute vision loss in terms of clinical course?
A
Gradual vision loss progresses slowly over time and is not associated with pain, whereas acute vision loss occurs suddenly and may be painful depending on the cause.
5
Q
According to the WHO, what visual acuity defines blindness?
A
Visual acuity (VA) less than 3/60 in the better eye, even with the best possible correction.
6
Q
What is the visual field criterion for blindness according to the WHO?
A
A visual field constricted to less than 10 degrees around central fixation in the better eye.
7
Q
Why is the WHO definition of blindness important in a clinical or social context?
A
It determines eligibility for disability grants and access to specific support services for visually impaired individuals.
8
Q
Can a person with visual acuity better than 3/60 be considered blind?
A
Yes, if their visual field is constricted to less than 10 degrees, they still meet the WHO criteria for blindness.
9
Q
What is the general definition of visual impairment?
A
Visual impairment generally refers to visual acuity of 6/18 or worse in the better eye, even with the best possible correction.
10
Q
How is visual impairment classified?
A
Visual impairment is divided into categories based on the severity of vision loss.
11
Q
Which eye is considered when assessing the severity of visual impairment?
A
The better eye is used when determining the level of visual impairment
12
Q
Is visual impairment always the same as blindness?
A
No, visual impairment includes a range of vision loss, and only the most severe cases meet the criteria for blindness.
13
Q
Which types of visual conditions cause loss of central vision?
A
Loss of central vision occurs in Age-Related Macular Degeneration (AMD) and Toxic Optic Neuropathy.
14
Q
Which conditions are associated with peripheral vision loss?
A
Retinitis pigmentosa and glaucoma are associated with loss of peripheral vision.
15
Q
What are neurological field defects and what causes them?
A
Neurological field defects are vision losses due to brain or optic pathway damage, such as hemianopia or quadrantanopia, often caused by stroke, tumors, or trauma.
16
Q
What is nystagmus and how does it affect vision?
A
Nystagmus is an involuntary, repetitive movement of the eyes that can cause blurred or unstable vision, making it difficult to focus.
17
Q
What is a scotoma?
A
A scotoma is a blind spot or an area of reduced vision within the visual field, which may be central or peripheral depending on the cause.
18
Q
What happens to the alignment of a blind eye if blindness occurs before the age of 2 years?
A
The blind eye typically becomes esotropic, meaning it deviates inward.
19
Q
What happens to the alignment of a blind eye if blindness occurs after the age of 2 years?
A
The blind eye usually becomes exotropic, meaning it deviates outward.
20
Q
Why does the age at which an eye becomes blind affect its alignment?
A
This is due to the developmental influence of vision on ocular alignment; early vision loss disrupts normal visual fixation and alignment patterns.
21
Q
Conditions that can cause reversible visual impairment
A
Refractive Error
Cataract
Diabetic maculopathy
Corneal scarring / opacity
22
Q
What is the most common reversible cause of visual impairment worldwide?
A
Refractive error, such as myopia, hyperopia, or astigmatism, is the most common and easily correctable cause.
23
Q
How can cataracts lead to reversible blindness?
A
Cataracts cause clouding of the lens and lead to visual impairment, but vision can be restored with surgery.
24
Q
Is vision loss from diabetic maculopathy reversible?
A
Diabetic maculopathy can be partially reversible with timely laser therapy, anti-VEGF injections, and good glycaemic control.
25
Can corneal scarring or opacity cause reversible vision loss?
Yes, in some cases corneal scarring/opacity may be reversible with corneal transplantation or treatment of the underlying cause.
26
Conditions of irreversible causes of visual impairment
Optic atrophy
- Glaucoma
- Other
Age related macular degeneration
Retinal dystrophies – retinitis pigmentosa
27
Why is optic atrophy considered an irreversible cause of vision loss?
Optic atrophy involves permanent damage to the optic nerve, which cannot regenerate, making the vision loss irreversible.
28
Is vision loss due to glaucoma reversible?
No, glaucoma causes progressive optic nerve damage and permanent peripheral vision loss, which is not reversible.
29
How does age-related macular degeneration (AMD) lead to irreversible vision loss?
AMD affects the central retina (macula), especially in its dry form, causing permanent central vision loss.
30
What are retinal dystrophies and why is vision loss from them irreversible?
Retinal dystrophies, like retinitis pigmentosa, are genetic degenerative disorders that cause progressive and irreversible photoreceptor loss.
31
What do all irreversible causes of blindness have in common?
They involve permanent structural or neural damage to critical visual pathways or retinal tissues, with no current treatments that can restore lost vision.
32
What is intracapsular cataract extraction (ICCE)?
In ICCE, the entire lens is removed along with its capsule and zonules in one piece.
33
What is extracapsular cataract extraction (ECCE)?
In ECCE, the lens is removed but the posterior capsule is left behind, which helps support an intraocular lens implant.
34
What is the preferred method for cataract extraction today?
Extracapsular cataract extraction (ECCE) with insertion of an intraocular lens (IOL) is the preferred technique.
35
Why is ECCE with IOL implantation preferred over ICCE?
It preserves the posterior capsule, allows for IOL implantation, and results in better visual outcomes and fewer complications.
36
What is a major drawback of intracapsular cataract extraction (ICCE)?
ICCE may leave the patient aphakic (without a natural or artificial lens), requiring +10 dioptre spectacles to see clearly.
37
What happens if an aphakic patient from ICCE does not use corrective glasses?
Without powerful +10 spectacles, the patient may remain functionally blind, similar to before the operation.
38
What is phacoemulsification in cataract surgery?
Phacoemulsification uses an ultrasound probe to emulsify (break up) the cataract, which is then sucked out through a small wound.
39
How is phacoemulsification related to extracapsular cataract extraction (ECCE)?
Phacoemulsification is the modern technique of ECCE, offering smaller incisions and faster recovery
40
Does phacoemulsification require sutures?
No sutures are usually needed because the incision is small and self-sealing.
41
What advanced technology can be used to assist in phacoemulsification?
Some surgical steps in phacoemulsification can now be performed using a femtosecond laser, improving precision and outcomes
42
What is the most common cause of leukocoria?
Cataract is the most common cause of leukocoria.
43
Name infectious causes of leukocoria that also cause vision loss.
Toxoplasmosis and Toxocariasis can cause leukocoria and vision loss.
44
Which malignant eye condition presents with leukocoria?
Retinoblastoma, a malignant tumor of the retina, presents with leukocoria.
45
What retinal conditions can cause leukocoria?
Longstanding retinal detachment can cause leukocoria.
46
What congenital vitreous disorder causes leukocoria?
Persistent posterior hyperplastic primary vitreous (PHPV) causes leukocoria
47
Causes of leukocoria
Cataract
Toxoplasmosis
Toxocariasis
Retinoblastoma
Longstanding retinal detachment
Persistent posterior hyperplastic primary vitreous
48
Why is refractive error an important public health issue?
It is a very common cause of correctable blindness, especially in lower socio-economic groups.
49
How can healthcare workers quickly check for a refractive error?
By using a pinhole test—if vision improves, the issue is likely a refractive error.
50
What should be done for patients found to have a refractive error?
They should be referred to an optometrist for assessment and corrective lenses
51
How is access to refractive correction being improved in low-income communities?
Many optometrists run clinics for indigent patients, improving access to affordable vision care.
52
What simple test can be used to assess whether poor vision is due to a refractive error?
The pinhole test is used to check if vision improves when looking through a 1mm pinhole.
53
How does the pinhole improve vision in refractive error?
The pinhole allows only central, parallel rays of light to enter, which do not require refraction, resulting in a clear retinal image.
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What does improvement in vision through a pinhole suggest?
It suggests that the cause of poor vision is likely a refractive error.
56
When should the pinhole test be used?
In any patient complaining of poor vision, after measuring their visual acuity.
57
What are the four main types of refractive error?
Myopia, hyperopia, astigmatism, and presbyopia.
58
What is myopia?
Myopia (nearsightedness) is when distant objects appear blurry because the eye focuses images in front of the retina.
59
What is hyperopia?
Hyperopia (farsightedness) is when near objects appear blurry because the eye focuses images behind the retina.
60
What is astigmatism?
Astigmatism is caused by an irregularly shaped cornea or lens, resulting in blurred or distorted vision at all distances.
61
What is presbyopia?
Presbyopia is the age-related loss of near focusing ability, due to the decreased elasticity of the lens, usually noticeable after age 40.
62
What is hyperopia?
Hyperopia (farsightedness) is a refractive error where near objects appear blurry because images are focused behind the retina.
63
What causes hyperopia?
It is usually due to an eyeball that is too short or a cornea that is too flat.
64
How is hyperopia corrected?
With convex (plus) lenses that converge light rays to focus images correctly on the retina.
65
What visual clue may be seen in a child wearing glasses for hyperopia?
The convex lenses used to correct hyperopia magnify the appearance of the child’s eyes.
66
What is myopia?
Myopia (nearsightedness) is a refractive error where distant objects appear blurry because images are focused in front of the retina.
67
What causes myopia?
It is usually due to an eyeball that is too long or a cornea that is too curved.
68
How is myopia corrected?
With concave (minus) lenses that diverge light rays to move the focal point back onto the retina.
69
What visual clue may be seen in someone wearing glasses for myopia?
The concave lenses used to correct myopia minify the appearance of the patient’s eyes.
70
What is degenerative myopia?
A severe form of myopia, typically with refractive error > -8 dioptres, where the eyeball becomes progressively elongated, leading to structural damage.
71
Why are highly myopic eyes more prone to degeneration
Because of "stretchy eyeballs"—the excessive lengthening causes thinning and weakening of the retina and surrounding structures.
72
What are two serious complications of degenerative myopia?
Retinal degeneration
Haemorrhage from choroidal neovascularisation
73
What is choroidal neovascularisation, and why is it dangerous in degenerative myopia?
It is the growth of abnormal new blood vessels beneath the retina, which can bleed and scar, leading to severe vision loss.
74
What is keratoconus?
Keratoconus is a progressive eye condition in which the cornea thins and bulges into a cone shape, causing visual distortion.
75
What type of refractive error does keratoconus cause?
It leads to progressive myopic astigmatism.
76
What are some conditions and habits associated with keratoconus?
Atopy (allergic conditions)
Chronic eye rubbing
Down’s syndrome
Other genetic or environmental factors
77
What is the initial treatment for keratoconus?
Hard contact lenses can help improve vision by providing a regular refracting surface.
78
What may be required in advanced keratoconus?
A corneal transplant may become necessary if contact lenses no longer provide adequate vision.
79
Where is corneal blindness most commonly seen?
Corneal blindness is most common in the developing world, especially in equatorial countries.
80
What is a major infectious cause of corneal blindness in equatorial regions?
Trachoma, a chronic chlamydial eye infection.
81
What are the complications of trachoma that lead to corneal blindness?
Entropion (inward turning of the eyelid)
Trichiasis (inward-growing eyelashes)
Scarring of the conjunctiva and cornea
82
What is interstitial keratitis and what causes it?
Interstitial keratitis is inflammation of the corneal stroma without ulceration, often following infections like:
Congenital syphilis
Tuberculosis (TB)
Measles
83
What is band keratopathy?
Band keratopathy is calcification of the cornea, typically seen as a horizontal, grayish-white band across the central cornea.
84
What causes band keratopathy?
It can result from any cause of chronic intraocular inflammation
85
Which condition in children is a known cause of band keratopathy?
Juvenile idiopathic arthritis (JIA)-related uveitis, which can lead to painless, slow loss of vision.
86
Which children with JIA are at highest risk for developing uveitis and band keratopathy?
Children with pauciarticular JIA who are ANA-positive.
87
What screening is recommended for children with JIA?
Regular eye screening is essential to detect asymptomatic uveitis early and prevent complications like band keratopathy.
88
What is optic atrophy?
Optic atrophy refers to the degeneration of the optic nerve, resulting in vision loss and pallor of the optic disc.
89
What is glaucomatous cupping?
In glaucomatous optic atrophy, the optic disc shows increased cupping due to pressure-induced loss of nerve fibres.
90
What does the optic disc look like in non-glaucomatous optic atrophy?
The disc appears flat with diffuse pallor, without increased cupping.
91
What does the optic disc look like in post-papilloedema optic atrophy
The disc is raised and pale, reflecting previous swelling and subsequent damage.
92
What are common causes of optic atrophy related to mechanical damage?
Compression of the optic nerve, such as by a tumour.
93
How does glaucoma cause optic atrophy?
Through damage to the optic nerve head caused by elevated intraocular pressure.
94
What metabolic, infective, and genetic diseases can cause optic atrophy?
Retinitis pigmentosa
Syphilis
Tobacco-alcohol amblyopia
Ethambutol toxicity
95
How can chronic papilloedema lead to optic atrophy?
Prolonged swelling of the optic nerve head causes ischemic damage and nerve fibre loss, resulting in atrophy.
96
List the causes of optic atrophy
- Compression of the optic nerve eg. tumour
- Damage to the optic nerve head in glaucoma
- Metabolic, infective & genetic diseases of the retina: retinitis pigmentosa, syphilis, tobacco-alcohol amblyopia, ethambutol toxicity
- Chronic papilloedema
97
What is a characteristic optic disc feature in retinitis pigmentosa?
Waxy pallor of the optic disc.
98
What pigmentary change is seen in retinitis pigmentosa?
Bone spicule pigmentary retinopathy—clumps of pigment shaped like bone spicules scattered in the retina.
99
What happens to the retinal blood vessels in retinitis pigmentosa?
The blood vessels become attenuated (narrowed).
100
Rerinitis Pigmentosa Features
- Waxy pallor of the disc
- Bone spicule pigmentary retinopathy
- Attenuated blood vessels
101
What are some systemic associations of retinitis pigmentosa?
Deafness (e.g., in Usher syndrome)
Heart block
Cerebellar disease
102
What are common symptoms of retinitis pigmentosa?
Night blindness (nyctalopia)
Tunnel vision due to progressive loss of peripheral vision
103
What is the underlying cause of retinitis pigmentosa?
It is caused by hundreds of genetic mutations affecting retinal photoreceptors or the retinal pigment epithelium.
104
What is papilloedema?
Papilloedema is bilateral optic disc swelling due to raised intracranial pressure.
105
What clinical features should prompt you to look for papilloedema?
Early morning headaches
VI nerve palsies
Personality changes
106
Does acute papilloedema cause vision loss?
No, acute papilloedema does not cause vision loss, but it can cause transient visual obscurations lasting seconds and occurring multiple times a day.
107
What condition should you suspect if a patient has a swollen disc and sudden vision loss?
Papillitis (optic neuritis)—urgent referral to an ophthalmologist is needed within 24 hours.
108
What can chronic papilloedema lead to if untreated?
It can cause slow, progressive loss of vision due to optic atrophy.
109
What is the appropriate referral for any patient with papilloedema?
Refer to neurology for neuroimaging and further investigation to identify the underlying cause of raised intracranial pressure.
110
What is Age-Related Macular Degeneration (ARMD)?
ARMD is a degenerative disease of the macula seen in elderly patients, especially those who are lightly pigmented (e.g., Caucasians).
111
What are drusen, and how are they related to ARMD?
Drusen are yellow deposits under the retina, commonly found in older Caucasians. They are early signs of ARMD and initially do not interfere with vision
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What are the main causes of central vision loss in ARMD?
Macular atrophy
Leakage or bleeding from choroidal neovascular membranes (Wet ARMD)
Fibrosis or scarring
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What treatment can prevent vision loss in Wet ARMD?
Early treatment with anti-VEGF injections can prevent leakage, bleeding, and scarring in Wet ARMD.
114
When should a patient with ARMD be referred?
If ARMD is detected clinically
If the patient has lost vision in one eye
115
What type of vision loss does diabetic maculopathy cause?
It causes insidious (gradual and painless) loss of vision.
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How is diabetic maculopathy treated?
Treatment includes:
Laser therapy
Anti-VEGF injections
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Why is early detection of diabetic maculopathy important?
Because early treatment can preserve vision and prevent progression to irreversible vision loss.
118
What is glaucoma?
Glaucoma is an optic neuropathy characterized by:
Cupping of the optic disc
Characteristic visual field loss
Often associated with raised intraocular pressure (IOP)
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What is the normal range for intraocular pressure (IOP)?
10–21 mmHg
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Can vision and IOP be normal in early glaucoma?
Yes. Visual acuity (VA) and IOP may be completely normal in the early stages of glaucoma.
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What is the hallmark optic disc change seen in glaucoma?
Cupping of the optic disc
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What are the two main anatomical types of glaucoma?
Open-Angle Glaucoma (Acute or Chronic)
Closed-Angle Glaucoma (Acute or Chronic)
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How is glaucoma further classified based on cause?
Primary Glaucoma
Secondary Glaucoma (can be Pre-Trabecular, Intra-Trabecular, or Post-Trabecular)
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How is the type of glaucoma (open vs closed angle) diagnosed?
By gonioscopic examination, which assesses the anterior chamber angle where aqueous humor drains.
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What distinguishes primary from secondary glaucoma?
Primary glaucoma has no identifiable underlying cause.
Secondary glaucoma occurs due to another condition, such as trauma, inflammation, or steroid use.
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What are the key symptoms of acute angle-closure glaucoma?
Severe eye pain
Decreased visual acuity and haloes around lights
Redness of the eye
Nausea and vomiting
Mid-dilated pupil
Hazy cornea
Positive eclipse sign
127
What is the "eclipse sign" in acute glaucoma?
A clinical sign where the iris blocks aqueous humor drainage, causing a shadow on the iris seen with oblique light.
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What are the symptoms of chronic glaucoma?
Usually painless
Visual acuity may be normal (but can be no perception of light (NPL) in late stages)
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How is chronic glaucoma diagnosed?
Through a combination of:
Optic disc examination (cupping)
Visual field testing
Intraocular pressure (IOP) measurement
Gonioscopy to assess angle
130
Risk factors for open angle glaucoma
- Genetic (TIGR Myocillin gene etc)
- Black African Ancestry
- Myopia (long eyeball)
- Age > 45
- ?Diabetes
131
Risk factors for angle-closure glaucoma
- Genetic factors (especially South East Asian Ancestry as in Mamre)
- Hyperopia (short eyeball)
- Age
- Exposure to sympathomimetics or anticholinergics
132
What is the "eclipse sign" in acute glaucoma and how is it detected?
The eclipse sign refers to a crescent-shaped shadow on the nasal side of the iris when a torch is shone obliquely from the temporal side of the eye.
- It suggests a shallow anterior chamber.
- It is a clinical indicator of angle closure, as the iris bows forward, partially blocking the drainage angle.
- Commonly seen in acute angle-closure glaucoma.
133
How do you perform and interpret the eclipse sign test, and what is its clinical significance?
Shine a light from the temporal (side) of the eye.
If the medial (nasal) iris is in shadow, this is a positive eclipse sign.
A positive eclipse sign indicates a shallow anterior chamber and risk of angle-closure glaucoma.
Do NOT dilate the pupil or prescribe anticholinergics or sympathomimetics, as these can precipitate acute angle closure.
134
What is the role of peripheral iridectomy and YAG laser iridotomy in angle-closure glaucoma?
Peripheral iridectomy is a surgical procedure that creates a small hole in the peripheral iris to allow aqueous humor to flow and prevent or treat angle-closure glaucoma.
The YAG laser can perform peripheral iridotomies non-invasively, often avoiding the need for surgery.
These procedures are performed by ophthalmologists after referral.``
135
What is acute angle-closure glaucoma (AACG)?
AACG is a sight-threatening ocular emergency caused by a sudden rise in intraocular pressure (IOP) due to closure of the anterior chamber angle, which prevents aqueous humour outflow.
136
What are the classic clinical features of acute angle-closure glaucoma?
Severe ocular pain
Red eye
Headache
Blurred vision or halos around lights
Nausea and vomiting
Mid-dilated, sluggish pupil
Corneal haze/edema
Shallow anterior chamber
137
What is the significance of a mid-dilated, sluggish pupil in AACG?
It indicates iris sphincter ischemia due to elevated intraocular pressure, and is a hallmark sign of AACG.
138
Why is corneal haze seen in acute angle-closure glaucoma?
Corneal haze occurs due to corneal edema secondary to very high IOP, which disrupts endothelial pump function and fluid balance.
139
What causes the red eye in AACG?
Redness is due to ciliary injection (perilimbal flush), indicating deep eye inflammation and congestion.
140
What is the "eclipse sign" in AACG and what does it indicate?
The eclipse sign refers to the appearance of the iris casting a shadow on the lens during oblique illumination, indicating a shallow anterior chamber, commonly seen in AACG.
141
How is AACG differentiated from other causes of red eye (e.g., conjunctivitis or uveitis)?
AACG has severe pain, mid-dilated pupil, hazy cornea, and high IOP, while conjunctivitis typically lacks pain and pupil changes. Uveitis often has a small, irregular pupil and no IOP spike.
142
What is the immediate management of acute angle-closure glaucoma?
Reduce IOP urgently with:
- IV acetazolamide
- Topical beta-blockers (e.g., timolol)
- Alpha-agonists (e.g., apraclonidine)
- Topical pilocarpine after initial pressure reduction
Definitive treatment: laser or surgical peripheral iridotomy to open the angle.
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What is the prognosis if acute angle-closure glaucoma is left untreated?
Permanent vision loss or blindness can occur within hours to days, making timely recognition and intervention critical.
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Who is at increased risk for acute angle-closure glaucoma?
Older adults
Hyperopes (farsighted individuals)
Women
People of Asian descent
Those with a family history of glaucoma
145
What are the possible sequelae of untreated or delayed acute angle-closure glaucoma?
Permanent corneal edema due to endothelial cell damage
Relative Afferent Pupillary Defect (RAPD) indicating optic nerve damage
Permanent vision loss or blindness
Chronic angle-closure glaucoma from peripheral anterior synechiae
Optic atrophy
146
What is a Relative Afferent Pupillary Defect (RAPD), and why does it occur in AACG?
RAPD is a sign of optic nerve dysfunction, caused by ischemic damage from prolonged elevated IOP. It is observed using the swinging flashlight test
147
What is the role of bilateral peripheral iridotomies (PIs) in AACG?
Bilateral PIs can prevent an acute attack in the fellow eye, which is at high risk for developing angle closure due to similar anatomy.
148
Why can permanent corneal edema occur after AACG?
Elevated IOP damages the corneal endothelium, which is responsible for pumping fluid out of the cornea. Once damaged, this results in chronic corneal clouding.
149
Can angle-closure glaucoma become chronic after an acute episode?
Yes. If angle closure leads to the formation of peripheral anterior synechiae, it may result in chronic angle-closure glaucoma, requiring long-term management.
150
What is chronic glaucoma?
Chronic glaucoma, most commonly primary open-angle glaucoma (POAG), is a slowly progressive optic neuropathy associated with elevated intraocular pressure, optic disc changes, and visual field loss.
151
What are the symptoms of chronic glaucoma?
It is often asymptomatic until late stages, when irreversible vision loss has already occurred. Patients may not notice vision loss until one eye is completely blind, as central vision is preserved until late.
152
Why is central vision preserved until late in chronic glaucoma?
Because glaucoma initially affects the peripheral retinal nerve fibers, causing tunnel vision. The macula, responsible for central vision, is spared until advanced disease.
153
What is the best way to detect glaucoma in the community?
By examining the optic disc using ophthalmoscopy, looking for signs like:
Increased cup-to-disc ratio
Disc cupping or notching
Thinning of the neuroretinal rim
These may indicate glaucomatous optic neuropathy.
154
What are risk factors for chronic (open-angle) glaucoma?
Age >40
Family history of glaucoma
African or Asian ancestry
Diabetes
Hypertension
High myopia
Prolonged steroid use
155
How is chronic glaucoma confirmed after optic disc abnormalities are found?
Tonometry to measure IOP
Visual field testing for peripheral field defects
Optical Coherence Tomography (OCT) to assess nerve fiber layer
Gonioscopy to assess the drainage angle
156
What is the main goal of chronic glaucoma treatment?
To lower intraocular pressure (IOP) and prevent further optic nerve damage. Treatment does not reverse existing vision loss.
157
Disc Signs of Glaucoma
- CDR >0.6
- Baring, bayonetting and nasalisation of vessels
- Disc haemorrhages
- Exposed lamina cribrosa (laminar dot sign)
- Notching of cup
Disc pallor
158
What is trabeculectomy surgery?
Trabeculectomy is a surgical procedure used to treat open- or closed-angle glaucoma by creating a controlled fistula to allow aqueous humour to drain from the eye, thereby lowering intraocular pressure (IOP).
159
How does trabeculectomy work to reduce intraocular pressure?
A full-thickness channel is created through the sclera, allowing aqueous humour to drain out. A scleral flap is sutured over it to control the rate of drainage.
160
What happens to the aqueous humour after it drains through the surgical fistula in trabeculectomy?
The aqueous humour diffuses into the subconjunctival space, forming a filtering bleb, where it is gradually absorbed into surrounding tissues.
161
In which types of glaucoma can trabeculectomy be used?
Trabeculectomy is indicated for both primary open-angle glaucoma and chronic or poorly controlled angle-closure glaucoma, especially when medications or laser therapy fail.
162
What is a filtering bleb and what is its role in trabeculectomy?
A filtering bleb is a raised area on the conjunctiva where aqueous humour collects after trabeculectomy. It acts as a reservoir and allows gradual diffusion of fluid into surrounding tissues, helping to maintain lower IOP.
163
What is a glaucoma drainage device (GDD)?
A GDD is an implanted tube shunt system that facilitates aqueous humour drainage from the anterior chamber to a plate or reservoir placed under the conjunctiva, helping to lower IOP in refractory or complicated glaucoma.
164
In which types of glaucoma are GDDs typically used?
GDDs are used in complicated glaucomas such as:
- Neovascular glaucoma
- Uveitic glaucoma
- Congenital or pediatric glaucoma
- Failed trabeculectomy cases
- Eyes with significant scarring or conjunctival damage
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Why might trabeculectomy fail in neovascular glaucoma?
In neovascular glaucoma, fibrovascular proliferation and conjunctival scarring often cause trabeculectomy failure due to rapid closure of the drainage site.
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How does a glaucoma drainage device work?
The tube is inserted into the anterior chamber, allowing aqueous humour to bypass the trabecular meshwork and drain to an external plate, promoting long-term IOP control.
167
What is the role of the tube in a GDD?
The tube maintains an open sclerostomy, ensuring continuous drainage of aqueous humour and preventing closure, which is common in high-risk or scarred eyes.
168
What is buphthalmos?
Buphthalmos, meaning "ox eye", is an enlargement of the eyeball due to raised intraocular pressure (IOP) in congenital or infantile glaucoma.
169
What are the classic signs of buphthalmos?
Corneal edema (cloudy cornea)
Enlarged eyeball
May also have watery eye (epiphora)
Photophobia (light sensitivity)
170
Why does the eyeball enlarge in buphthalmos?
In young children, the sclera is more elastic, so raised IOP causes the eyeball to stretch and enlarge.
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Can buphthalmos be subtle or asymptomatic?
Yes. Some cases may be mild or unnoticed, which is why early recognition and referral are essential if there’s any doubt
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What should be done if buphthalmos is suspected in a child?
Urgent referral to an ophthalmologist is needed to confirm the diagnosis and start prompt treatment to prevent vision loss.
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Iris bombé in secondary glaucoma after uveitis
This is caused by blockage of aqueous flow from the posterior to the anterior chamber
(A Bombé is a kind of cake with a hole in the middle):
174
Diabetic rubeotic (neovascular) glaucoma
Can be prevented by timeous retinal laser treatment
