Opthalmology

Squint (strabismus)

This is an eye condition in which the two eyes are not aligned when looking at an object

– The condition can be present occasionally or permanently, and usually affects one eye

– The problem is that if present during childhood, it can result in amblyopia and loss of depth perception

Types:

i) Concomitant:

– This is where the deviation is the same magnitude regardless of gaze position

– This occurs due to an imbalance in the power of the extraocular muscles of the eye

– Can be convergent (more common) or divergent

ii) Incomitant:

– This is a type where the magnitude varies as the person shifts gaze in different directions

iii) Paralytic:

– This is much rarer which occurs due to paralysis of the extraocular muscles

Tests:

– Corneal light reflection test – hold a light source 30cm from the child’s face to see if the light reflects symmetrically on the pupils

– Cover test – This is used to identify the nature of the squint.

– Ask the child to focus on an object and cover one eye

– Look at the uncovered eye to see if it deviates. This shows if there is misalignment between the two eyes

Management:

– Refer to ophthalmology

– Relieve deprivation and correct refractive errors with glasses

– Patch the good eye till vision in lazy eye improves –> this forces the “lazy” eye to work to prevent amblyopia

Congenital Cataract

This is used to describe a clouding of the lens which leads to a decrease in vision

– It covers a broad spectrum of severity, from insignificant to profound visual impairment

– It is important to treat this urgently as failure to treat can lead to amblyopia (lazy eye)

Causes:

– Infections in utero –> rubella, CMV, toxoplasmosis

– Genetic causes –> Down syndrome, Marfan syndrome, Alport syndrome

– May also be idiopathic

Symptoms:

Difficulties in vision, but this is difficult to tell in new-borns

Diagnosis:

Ophthalmoscope shows loss of the red reflex

Management:

Surgical removal of the cataract to avoid amblyopia

Retinoblastoma

This is a malignant proliferation of the immature cells of the retina, which is the most common primary malignant tumour of the eyes seen in young children.

– It does not have a high mortality rate, but children may lose their vision in that eye irreversible

– Half of children have an inherited form of the condition, which is due to a mutation in the tumour suppressor gene Rb on Chr 13

– This is an autosomal dominant mutation and has 90% penetrance

– As both alleles are required to give rise to the condition, if children inherit one faulty allele, then only one other mutation is required to give rise to retinoblastoma

– This is known as the “two-hit model”

– It can also be due to a sporadic mutation

Symptoms:

– Lead to difficulties in vision, but this is difficult to tell in new-borns

– Loss of the red reflex – leukocoria (white pupil)

– Can lead to a squint

Tests:

– Ophthalmoscope shows loss of red reflex

– CT/MRI

Management:

Enucleation of the eye is the mainstay of treatment

Ophthalmia neonatorum/Neonatal conjunctivitis

This refers to conjunctivitis which occurs in the first 28 days of life, usually due to bacterial infection

– It is typically contracted during vaginal delivery due to exposure to bacteria in the birth canal

– If left untreated, neonatal conjunctivitis can lead to blindness

Causes:

– Neisseria gonorrhoea (most common)

– Chlamydia trachomatis

Tests:

Discharge should be swabbed and gram-stained and cultured

Management :

– Antibiotic ointment into new-born’s eyes to prevent gonococcal ophthalmia

– If baby develops conjunctivitis –> use antibiotic eye drops