Ophthalmology

Question 1

How thick is cornea?

Answer 1

About 0.77 to 0.89 mm

Question 2

Parts of the cornea.

Answer 2

Epithelium
Stroma
Descemet’s membrane
Endothelium

Question 3

Innervation of cornea.

Answer 3

it is innervated diffusely by the long ciliary nerves, which arise from the ophthalmic division of the trigeminal nerve (cranial nerve V) and terminate in naked nerve endings in the anterior stroma and among the wing cells of the corneal epithelium.

Question 4

Evaluation of PLR

Answer 4

light

Question 5

Palpebral reflex- afferent and efferent arms

Answer 5

Afferent= V cranial nerve 
Efferent= VII facial nerve

Question 6

Corneal reflex

Answer 6

corneal sensation- afferent way: trigeminal nerve
efferent way: facial nerve

Question 7

Lagophthalmos

Answer 7

incomplete eyelid closure

Question 8

What is strabismus

Answer 8

Strabismus is abnormal eye position, ‘misalignment’. Can be unilateral, bilateral; converging/diverging upward/downward (hypotropia/hypertropia).

Question 9

2 main functions of the cornea

Answer 9

1. Protection
2. Vision 70 % of the light is refracted on the cornea.

Question 10

Iridodialysis

Answer 10

Separation of the iris from the ciliary body mainly as a result of trauma.

Question 11

Most common causes of uveitis

Answer 11

Primary
Secondary : blunt / trauma, IO neoplasia, corneal ulceration, lents rupture, catarate, parasitic infection, systemic disease (bacteremia/septicemia “S. equi, L. interrogans, L. pomona and Gram- sepsis), immune-complex disease; viremia, diseminated mycosis and ERU syndrome)

Question 12

Congenital abnormalities of the lens

Answer 12

Aphakia- lack of lens
Microphakia- to small lens
Spherophakia- spherical lens
Lenticonus- bulging, protrusion of the anterior or posterior pole of the lens.
Coloboma- missing part of the lens, usually notching of the equator.
Most of the congenital lens abnormalities is associated with multiple ocular defects as during embryonal development lens is a important ‘stimulus’ for the development of other parts of the eye.

Question 13

Anatomy and physiology of conjunctiva

Answer 13

mucous membranes that cover the inner aspect of the eyelids and eyeball. Stratified non-keratinized columnar epithelium + goblet cells (producing mucous) and connective tissue= fibrous and lymphoid tissue (everted lymph nodes) + abundant blood vessels.

Question 14

Healing of the conjunctiva

Answer 14

Very quick, the only problem is the restoration of the normal amount of goblet cells which takes longer.

Question 15

Layers of the retina.

Answer 15

1. RPE- retinal pigmented epithelium
2. Photoreceptor layer.
3. External limiting membrane.
4. Outer nuclear layer.
5. Outer plexiform layer.
6. Inner nuclear layer.
7. Inner plexiform layer.
8. Ganglion cell layer.
9. Optic nerve fiber layer.
10. Internal limiting layer.

Question 16

Retinal pigmented epithelium.

Answer 16

The outermost retinal layer- creating the non-sensory retina. Lays between choroid and photoreceptor layer and contain melanin granules. It’s dark brown except for the part with tapetum.
The main role of that layer is to provide nutrition for the neurosensory retina, recycling of the bleached ‘used’ photopigment, storage of the vitamin A, phagocytosis, absorb stray light and free radicals.

Question 17

Photoreceptor layer.

Answer 17

Outer segments of rods and cones that contain stacked discs with photopigment, and part of the inner segments with mitochondria. Here’s where transduction of light stimulus happens.

Question 18

Outer nuclear layer.

Answer 18

Cell bodies of rods and cones.

Question 19

Outer plexiform layer.

Answer 19

Synaptic connections between photoreceptors and bipolar, amacrine and horizontal cells.

Question 20

Inner nuclear layer.

Answer 20

Cell bodies of horizontal, bipolar, amacrine and Mullers cells.

Question 21

Inner plexiform layer.

Answer 21

Is the second synaptic layer between axons of amacrine, bipolar, horizontal cells and retinal ganglion cells.

Question 22

Ganglion cell layer.

Answer 22

cell bodies of the RGCs, usually one cell thick, axons of these cells run parallel to the retina and converge onto the optic disc.

Question 23

Nerve fibre layer.

Answer 23

Axons of the RGCs that run parallel to the retina and converge onto the optic disc.

Question 24

Internal limiting layer

Answer 24

Basement layer, the border between the retina and vitreous.

Question 25

Types of cells that form neuro-retina.

Answer 25

Rods, cones, amacrine, horizontal, bipolar, interplexiform neurons, Muller’s cells, retinal ganglion cells.

Question 26

Blood supply to the retina.

Answer 26

Dual blood supply (as the most metabolically active tissue in the body).
1- Choroid vessels that supply outer retina and
2- retinal vessels that supply mid and inner retina, they’re branches of posterior ciliary arteries called cilioretinal arteries and penetrate the sclera in a circle around the optic disc.

Question 27

Ocular surface microflora.

Answer 27

Gram⁺: Staphylococcus, Bacillus, Corynebacterium; Streptomyces.

Gram^-: Moraxella, Escherichia, Acinetobacter, Enterobacter.

Fungi: Aspergillus, Clodosporium, Alternaria, Peneicillium, Mucor.

Question 28

Keratomalacia

Answer 28

corneal melting, results when there is an overabundance of these enzymatic proteins elaborated by these recruited inflammatory cells, activated resident host cells, and any pathogens present.

The destructive forces overwhelm the restorative responses and result in dissolution of corneal collagen and necrosis of cells. The production of elastase and alkaline phosphatase by Pseudomonas, hyaluronidase by Staphylococcus and other extracellular proteases by fungal organisms can greatly augment this melting process.

Even when an infection is eradicated by the frequent use of an effective antimicrobial, residual proteases may continue to destroy the corneal matrix, even after microbial replication has ceased