38 - Hirschberg test

Positive Hirschberg sign: the light falls on the centre of the right pupil, but is medial to the centre of the left pupil; therefore, the person in the picture has an exotropia.

In the fields of optometry and ophthalmology, the Hirschberg test, also Hirschberg corneal reflex test, is a screening test that can be used to assess whether a person has strabismus (ocular misalignment).

A photographic version of the Hirschberg is used to quantify strabismus.

It is performed by shining a light in the person's eyes and observing where the light reflects off the corneas. In a person with normal ocular alignment the light lands on the centre of both corneas. For an abnormal result, based on where the light lands on the cornea, the examiner can detect if there is an exotropia (abnormal eye is turned out), esotropia (abnormal eye is turned in), hypertropia (abnormal eye higher than the normal one) or hypotropia (abnormal eye is lower than the normal one).

In exotropia the light lands on the medial aspect of the cornea. In esotropia the light lands on the lateral aspect of the cornea. In hypertropia the light lands on the inferior aspect of the cornea. In hypotropia the light lands on the superior aspect of the cornea. A cover test can tell you the extent of the eso/exotropia.

Individuals can suffer from several tropias at once. In Graves ophthalmopathy, it is not uncommon to see an esotropia (due to pathology of the medial rectus muscle) co-morbid with a hypotropia (due to pathology of the inferior rectus muscle).

The technique was developed by German ophthalmologist Julius Hirschberg who in 1886 used a candle to observe the light reflex in an eye with strabismus.

37 - Persistent Hyperplastic Primary Vitreous (PHPV)

* It is persistence of the primary vitreous and hyaloid arterial system.

* Almost always unilateral (~90%)

*It is associated with Patau syndrome (Trisomy 13) .

* Presents as white pupillary reflex in the newborn (congenital leukocoria)

*It is usually associated with cataract, glaucoma , long and extended ciliary processes because of pull from contracted retrolental tissue, micropthalmos, intraocular hemorrhage and tractional retinal detachment.

* Investigations : USG and CT scan

* Differential diagnosis with retinoblastoma is done on the basis of micropthalmos and elongated ciliary processes.

* If diagnosed early, treatment is aspiration of lens, excision of retrolental membrane and vitrectomy.

* Visual prognosis is poor.

36 - Muscae Volitantes (Eye Floaters)

Muscae volitantes or floaters are moving vitreous opacities perceived when they cast a shadow on the retina. So they are more noticeable against a bright background.

They may be perceived by the patient as black dots, rings, strands or spider webs and keep on moving even when the head is still. Vitreous is normally transparent but when some processes cause degeneration and liquefaction of the vitreous it produces floaters.

The various causes of floaters are :

35 - Vitreous Mcqs with answers and explanations

1. Hyaluronic acid is found in ?
a. Vitreous humor
b. Synovial fluid
c. Cartilage
d. Cornea

answer a.Vitreous humor

2. Floaters can be seen in all of the following except ?
a. Vitreous hemorrhage
b. Retinal detachment
c. Uveitis
d. Acute congestive glaucoma

answer d. Acute congestive glaucoma.

3. The most common cause of vitreous hemorrhage in adults is ?
a. Retinal hole
b. Trauma
c. Hypertension
d. Diabetes

answer d. Diabetes. Trauma is the most common cause of vitreous hemorrhage among young individuals.

4. Black floaters in a diabetic patient indicate ?
a. Vitreous hemorrhage
b. Maculopathy
c. Vitreous infarction
d. Post vitreous detachment

answer a. Vitreous hemorrhage.

5. A 25 year old male gives history of sudden painless loss of vision in one eye for the past 2 weeks. There is no history of trauma. On examination the anterior segment is normal but there is no fundal glow. Which one of the following is the most likely cause ?
a. Vitreous hemorrhage
b. Optic atrophy
c. Developmental cataract
d. Acute attack of angle closure glaucoma

answer a.vitreous hemorrhage .

6. "Snow ball" opacity in vitreous is seen in ?
a. Pars planitis
b. sarcoidosis
c. Juvenile RA
d. Toxoplasmosis
e. Fuch's lesion

answer a and b. Pars planitis and Sarcoidosis. Other causes are amyloidosis,candidiasis and lyme disease.

7. Which one of the following statements concerning persistent hyperplastic primary vitreous (PHPV) is not true ?
a. It is generally unilateral
b. Visual prognosis is usually good
c. It may calcify
d. It is most easily differentiated from retinoblastoma by the presence of exopthalmos or cataract

answer b is a wrong statement because the prognosis of PHPV is usually poor.

8. PHPV is associated with which of the following ?
a. Patau syndrome
b. Down syndrome
c. Tuberous sclerosis
d. Sturge weber syndrome

answer a. Patau syndrome. Trisomy 13.

9. A vitreous aspirate has been collected in an emergency at 9 pm. What advice would you like to give to the staff on duty regarding the overnight storage of the sample ?
a. The sample should be kept at 4 degree centigrade
b. The sample should be incubated at 37 degree centigrade
c. The sample should be refrigerated in deep freezer
d. The sample should be refrigerated for the initial 3 hours and then incubated at 37 degree centigrade

answer a. The sample should be kept at 4 degree centigrade.

34 - Macular Function tests

Try this stupid mnemonic to remember this :

Photo Card's Entoptic view Indirectly stressed that Amsler's Flying Potential was Inferior 2 Maddox.

33 - Gerontoxon and Pseudogerontoxon

 

Arcus senilis (Gerontoxon) 
A common finding in the elderly but of no pathological significance. It is formed by lipid deposition at the periphery of the cornes. This condition is also found in familial hypercholesterol-anemias.

Pseudogerontoxon is a lesion that resembles a small segment of arcus senilis or gerontoxon and is seen in many individuals with limbal vernal or atopic keratoconjunctivitis. It is an important clinical finding because pseudogerontoxon is often times the only clinical evidence of previous allergic eye disease.

It is a characteristic feature of VERNAL KERATOCONJUNCTIVITIS, also called SPRING CATARRH.