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14.1 Major Blinding Diseases

Table of Contents

Blindness according to WHO is defined as a visual acuity of less than 3/60 with the best correction available or central visual field of less than 10º in the better eye. In a simpler way, it is when someone fails to count fingers at a distance of 3 meters in the eye that is considered good with the best available corrective/distance spectacles. The definition is the same to children and infants though there are different methods for testing vision in young children until when they are at preschool age when normal visual acuity chart can be used. The common causes of blindness are Cataract, Glaucoma, Trachoma, Vitamin A deficiency (discussed under nutrition chapter), and Diseases of the Retina, uncorrected Refractive Errors and Low Vision.

14.1.1 Cataract

Diagnostic Criteria

  • Cloudiness in the lens seen as a white mark behind the pupil and iris
  • Conjunctiva and cornea are clear and the whole iris can be seen clearly
NOTE:
Cataract may present in all age groups,blindness due to cataract is reversible
Treatment is only by surgery
Early treatment in children is mandatory

Referral

Refer all cases to eye surgeon for cataract surgery, available at some of the Districts,

Regional, Zonal and National Hospitals. Children should be referred immediately to a Paediatric Eye Tertiary Centre, White pupil in children may be a tumor in the eye and late referral may lead to permanent loss of vision, squint, loss of eye or loss of life.

14.1.2 Glaucoma

Glaucoma is a syndrome characterized by optic nerve damage and peripheral visual field loss which may be associated with raised intraocular pressure. The main classes of glaucoma are open angle glaucoma and angle closure glaucoma.

Note: Glaucoma may be congenital, primary or secondary to other ocular conditions

14.1.2.1 Primary Open Angle Glaucoma

Diagnostic Criteria

  • Painless loss of peripheral vision leading to absolute glaucoma as the end stage
  • Affects mainly adults of 40 years of age and above
  • Cornea and conjunctiva are clear
  • Pupil in the affected eye does not react with direct light in advanced stage
  • The optic nerve is always damaged, this can be seen through fundoscopy
  • One eye may be affected more than the other
  • First degree relatives of glaucoma patients are at increased risk
NOTE:
Primary Open Angle Glaucoma does not have symptoms in early stages, hence routine intraocular pressure check up and fundus examinations should be done in all people of 40 years and above by a qualified eye care personnel
All suspected cases of glaucoma should be referred to qualified eye care personnel for confirmation of diagnosis and treatment plan
Surgical treatment is usually preceded by medical treatment

Pharmacological Treatment

This is initiated after a diagnosis is reached by an ophthalmologist, refill of some medicines can be done by Assistant Medical Officers in ophthalmology but with regular reviews at a health facility with eye specialist. Medical treatment should be life long unless there are conditions necessitating other interventions

C: Timolol 0.25% or 0.5%, one drop in the affected eye, instill 12 hourly.

OR

D: Betaxolol 0.25% or 0.5%, one drop in the affected eye, instill 12 hourly. Use lower strength in mild disease and those at risk of complications.

In patients who comply to treatment and there is no good response

ADD

D: Latanoprost 0.005% one drop, 24 hourly in the affected eye.

OR

D: Prostamide bimatoprost 0.03%, one drop, 24 hourly in the affected eye.

  • These may be used as first-line in patients with contraindication of betablockers.
  • They can be used as a second-line drug in patients on beta-blockers if the target IOP reduction has not been reached.

In patients who are intolerant to prostaglandin analogue or are not responding give: D: Brimonidine 0.15–0.2%, one drop, 12 hourly, in the affected eye.

Failure to respond give:

C: Pilocarpine hydrochloride 2% or 4%, instill one drop in the affected eye 6 hourly.

Note: Pilocarpine causes long-standing pupil constriction so it should not be used unless a patient is prepared for glaucoma surgery or as an alternative topical treatment for patients who are contraindicated for Timolol use. Consult a specialist before using it.

In severe cases or while waiting for surgery, use:

C: Acetazolamide tablets (PO) 250 mg 6 hourly

Note: β-blockers are contraindicated to people who are known to have overt asthma as this group of medication may cause an acute asthmatic attack within a short time following instillation into the eye

Laser Treatment

  • It may be indicated in addition to or instead of eye drops or surgery.
  • Laser trabeculoplasty (Argon Laser Trabeculoplasty, Selective Laser Trabeculoplasty) or cyclophotocoagulation are different options among others

Surgical Treatment

It is done in all patients with poor compliance and when medical treatment is not useful.

14.1.2.2 Angle Closure Glaucoma

This is also known as Congestive glaucoma and commonly affect people aged 40 years and above.

Diagnostic Criteria

  • Patients presents with acute sudden onset of painful red eye in the affected eye
  • Severe headache and cloudiness of the cornea
  • Shallow anterior chamber
  • Fixed and semi-dilated pupil
  • Severe elevated intraocular pressure.
  • There is usually dramatic visual impairment and vomiting may be present
  • It may be asymptomatic if IOP raises slowly
Note:
Primary Angle Closure Glaucoma is an Ophthalmological Emergency
Refer all patients with Congestive glaucoma to eye specialist after initial medical treatment

Pharmacological Treatment

Institute therapy and then refer the patient to eye specialist at the Regional, Zonal or National Hospital for investigations and proper management. Try to achieve immediate IOP reduction

First-Line Treatment

C: Acetazolamide tablets, 500mg PO immediately as a single dose followed by 250 mg 6 hourly

AND

C: Timolol 0.25–0.5% eye drops, instill one drop 12 hourly in the affected eye

Use the above combined treatment until you have achieved your target IOP reduction, then continue with only Timolol eye drops for life unless patient has received surgical intervention and the IOP is reduced to normal level.

Note: Manage the associated pain and vomiting

Second-Line Treatment

If the above measures fail, use as a short term treatment, give systemic osmotic agents:

C: Intravenous 15–20% Mannitol 1.5–2mg/kg body weight to run slowly over 30–60 minutes

OR

C: Glycerol syrup (PO) 1–2 g/kg body weight, 50% solution as a single dose immediately.

These medicines have diuretic effects so they are only used as a single dose. They are also used in emergencies to prepare patients with high intraocular pressure for surgery as they lower intraocular pressure rapidly.

Note:
Acetazolamide is a sulphur containing medicine, do not use in patients allergic to sulphur.
Glycerol is a concentrated sugar solution, it should not be given in diabetic patients.

Referral

Management of advanced angle closure glaucoma is done by eye specialist. Hence, all patients with Angle Closure Glaucoma should be referred to eye specialist.

14.1.2.3 Childhood Glaucoma

  • Presents from birth to 5 years.
  • It is a syndrome where by the intraocular pressure is raised and cause abnormality of the eyeball and visual disturbances even blindness.

Diagnostic Criteria

  • Patients presents with eyes bigger than normal for age (buphthalmos)
  • Photophobia
  • Tearing
  • Cloudy cornea,
  • Red conjunctiva though not severe.

Surgical Treatment

Treatment for congenital glaucoma is usually surgery, which is done by Pediatric Ophthalmologist or Glaucoma specialist.

Referral

Refer any child who has the above mentioned signs and you suspect that he/she is having congenital glaucoma to a specialist at a Paediatric Eye Tertiary Centre (National Hospital and Zonal Referral Hospitals).

14.1.2.4 Secondary Glaucoma

This presents as a complication of other eye diseases such as uveitis, hypermature cataract, trauma and retinal diseases. It may also be due to prolonged use of steroids.

Diagnostic Criteria

  • Poor vision in the affected eye associated with
  • High intraocular pressure
  • Optic nerve damage
  • New vessels on the iris if the cause is retinal diseases

Pharmacological Treatment

Management of these patients depends on the cause but it includes medical, surgical and laser. Institute these treatments as you refer these patients:

C: Acetazolamide tablets, 500mg PO immediately as a single dose followed by 250 mg 6 hourly

AND

C: Timolol 0.25–0.5% eye drops, instill one drop 12 hourly in the affected eye.

Treatment of the preexisting eye disease is highly recommended.

Referral

Refer all patients suspected to have secondary glaucoma to a qualified eye specialist available at the Regional, Zonal or National Hospital.

14.1.3 Trachoma

It is a chronic conjunctivitis caused by infection with Chlamydia trachomatis (bacteria). It is one of the commonest causes of blindness worldwide. There is a chronic inflammation of the conjunctiva leading to scarring of the upper eyelid tarsal plate, entropion and in turn of eyelashes.

Diagnostic Criteria

  • Patients presents with photophobia in early stages or re-infection
  • Follicles in the upper tarsal plate seen as round and white nodules in active diagnostic.
  • In late stages, in-turned eyelashes rub on the cornea leading to corneal ulcers
  • Loss of vision due to Corneal scarring.

Clinical Stages according to World Health Organization

  • Trachomatous Inflammation Follicular (TF) – Presence of at least 5 follicles on the upper tarsal plate
  • Trachomatous Inflammation Intense (TI) – There is intense inflammation, the conjunctival blood vessels cannot be seen.
  • Trachomatous Scarring (TS) – Presence of white scars in the upper tarsal plate
  • Trachomatous Trichiasis (TT) – Presence of some eye lashes rubbing against the cornea
  • Corneal Opacity (CO) – Presence of corneal opacity (scar) affecting the central cornea

Non-Pharmacological Treatment

  • Face washing and total body hygiene to prevent transmission of disease from one person to the other
  • Environmental improvement/hygiene

Pharmacological Treatment

A: Oxytetracycline ointment 3% once a day for 6 weeks

OR

A: Azithromycin 1g as a single dose for adults- for preventive chemotherapy in mass treatment campaign

Table 14.1: Dosage of azithromycin in children

Weight (kg) I-day regimen
< 15 20mg/kg once daily
15 – 25 400mg (10 ml) once daily
26 – 35 600 mg (15 ml) once daily
36-45 800 mg (20 ml) once daily
> 45 Dose as per adults

Note: Preventive chemotherapy in mass treatment campaign is conducted only once a year

Surgery

Surgical correction of entropion in TT patients. This procedure can be done at a Dispensary or Health Centre and community level by a trained health worker.

14.1.4 Diseases of the Retina

Main diseases of the retina that cause blindness are Diabetic Retinopathy, Diabetic Macular Edema, Retinal Detachment and Age related Macular Degeneration.

14.1.4.1 Diabetic Retinopathy

  • It is a complication of diabetes mellitus in the eyes
  • It is a chronic progressive sight-threatening disease of the retinal blood vessels associated with the prolonged hyperglycaemia and other conditions linked to diabetic mellitus such as hypertension

Diagnostic Criteria

Diabetic retinopathy is mainly grouped into three stages/presentations:

  • Background diabetic retinopathy
  • Diabetic maculopathy
  • Proliferative diabetic retinopathy

Investigations

  • Perform fundoscopy in a well-dilated pupil (Direct or indirect ophthalmoscopy with or without biomicroscopy),
  • Fundus photography,
  • Optical Coherence Tomography and or Fluorescein Angiography done in specialized eye clinics
Note: Dilate the pupils with combined

C: Tropicamide 1%/Phenylephrine 2.5% eye drops

OR

C: Tropicamide 1% with C: Cyclopentolate 1% eye drops to screen

Pharmacological Treatment

For glycaemic control give antioxidant in non-proliferative diabetic retinopathy

C: Multivitamin +carotenoids tablets once daily to a maximum of 3 months

For intravitreal anti Vascular Endothelial Growth Factor (VEGF) in Proliferative Disease S: Bevacizumab 1.25 mg per 0.05ml stat

OR

S: Ranibizumab 0.5 mg per 0.05ml stat.

Repeat after every month to a maximum of 6 months. Re-assess on 3 monthly basis if there are signs of disease progression, restart treatment if any, with close follow up.

Note: These injections are only given by specialist eye surgeons.

AND

S: Injection Triamcenolone acetonide 0.05 ml intravitreal stat. Repeat after 3 months if it is necessary. This is indicated in Diabetic Macula Edema.

Surgical Treatment

  • This is done in the proliferative stage
  • It involves removal of vitreous and or blood, peeling of formed fibrovascular tissue and reattachment of retina if the retina is detached
  • It is combined with retinal photocoagulation
  • The vitreous cavity may be filled with temponade liquid such as silicon oil or expansile gas like sulfur perfluoropropane or hexafluoride depending on the level of complication
  • It may also be combined with pharmacological treatment (Anti VEGF) mentioned above

Laser Treatment

Laser photocoagulation: Extent and type of this treatment depending on the stage of the disease

Note:
Ophthalmologists should work together with Physicians to holistically treat the diabetic patient.
Poorly controlled diabetes and diabetic retinopathy can lead to blindness
All patients with diabetes mellitus regardless of their eye conditions, should have a thorough eye examination by available eye care personnel or an eye specialist at least once a year.
Dilated eye examination and direct viewing of the retina by an
ophthalmologist or qualified eye care personnel is mandatory.
Urgent referral of all diabetic patients with sudden loss of vision to eye specialist

14.1.4.2 Age Related Macular Degeneration

It is a disease condition characterized by progressive macular changes that are associated with increase in age.

Diagnostic Criteria

  • Drusens around macula area (yellowish excrescence in the retina)
  • Affects elderly over 60 years
  • Poor central vision, later can lead to blindness

Investigations

  • Fundoscopy through a well-dilated pupil,
  • Optical Coherence Tomography and or
  • Fluorescein angiography.

Pharmacological Treatment

  • This depends on clinical presentation.
  • Intravitreal injection in the affected eye

S: Bevacizumab 1.25 mg per 0.05ml stat

OR

S: Ranibizumab 0.5 mg per 0.05ml stat.

Give Antioxidant in non-proliretative Diabetic Retinopathy

C: Multivitamin + Beta-carotenoids, Zinc Sulphate and Lutein, 1 tablet once daily to a maximum of 3 months

Surgical Treatment

Type of surgery depends on the presentation/ stage of the disease

14.1.5 Refractive Errors

This is a condition where one presents with poor vision either at near or distance at any age. There are mainly 4 types of refractive errors namely presbyopia, myopia, astigmatism and hyperopia. A patient may have more than one type of refractive error.

14.1.5.1 Presbyopia

This is a disorder of refractive status commonly occurring in older people.

Diagnostic Criteria

  • It usually starts after the age of 40 years
  • The main complaint is difficulty in reading/writing or doing near works
  • Diagnosis is only through refraction. Attendance to heath facility is also a good opportunity for screening of glaucoma and diabetic retinopathy

Non-Pharmacological Treatment

Convex lens spectacles for near vision

14.1.5.2 Myopia (Short sightedness)

This is a condition whereby patient has difficulty seeing far objects.

Diagnostic Criteria

  • It is common in young age between 5–25 years
  • The condition persists throughout life
  • If not treated early, it may progress rapidly and lead to retinal complications
  • It is diagnosed through refraction.

Non-Pharmacological Treatment

Concave lens spectacles for constant wear.

14.1.5.3 Hypermetropia (Long sightedness)

This is a condition where patients have difficulty in seeing near objects. It is less manifested in children as they have a high accommodative power.

Diagnostic Criteria

  • Ocular strain
  • Diagnosis in children should be reached after refraction through a pupil that is dilated

Non-Pharmacological Treatment

Convex lens spectacles for constant wear

Note: Spectacles should be given to

• Children who have only significant hypermetropia (more than +3.00 Diopter of Sphere both eyes), all children who present with squint and have significant hypermetropia and children with anisometropia

• Elderly who present with signs of ocular strain

14.1.5.4 Astigmatism

This is a condition where the cornea and sometimes the lens have different radius of curvature in all meridians (different focus in different planes). Some myopic and hyperopic patients may have astigmatism.

Diagnostic Criteria

  • Poor vision at distance,
  • Photophobia
  • Headache (sometimes).
  • Diagnosis is reached through refraction

Non-Pharmacological Treatment

Cylindrical lenses spectacles for constant wear.

14.1.6 Low Vision

Low vision is irreversible visual loss that cannot be corrected with surgeries or spectacles resulting in reduced ability to perform many daily activities. They have visual impairment even with treatment and or standard refractive correction and

Diagnostic Criteria

Inability to

  • Recognizing people in the streets,
  • Reading black boards,
  • Writing at the same speed as peers and
  • Playing with friends.

They have a range of visual acuity from less than 6/18 to perception of light and a reduced central visual field.

Investigations

  • Assessment of these patients is by thorough eye examination to determine the causes of visual loss and
  • Low vision assessment

Non-Pharmacological Treatment

  • Assessment of the patients’ visual function
  • Accurate refraction and provision of spectacles if indicated
  • Low vision devices such as optical devices (magnifiers, telescopes) and or non optical devices (reading stands and or reading slits) as per assessment results.
  • Surgical intervention is indicated e.g if a patient has cataract

Referral

All children with low vision should be referred to Paediatric Tertiary Eye Centre (Muhimbili National Hospital and Zonal Referral Hospitals)

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