Q-91. Micro-aneurysms in diabetic retinopathy occur in which layer?
a) Inner nuclear layer
b) Outer plexiform layer
c) Retinal pigment epithelium
d) Layer of rods and cones
Answer: Inner nuclear layer
Explanation:
Micro-aneurysms are the earliest clinical sign of diabetic retinopathy and occur secondary to capillary wall out-pouching due to pericyte loss.
They appear as small red dots in the superficial retinal layers, and there is fibrin and red blood cell accumulation in the micro-aneurysm lumen.
Micro-aneurysms are located within the inner nuclear layer in capillaries linking the superficial and deep capillary network.
Hemorrhages – Ruptured micro-aneurysms, capillaries and venules are all sources of intra-retinal hemorrhages, which are mostly located within the outer plexiform and inner nuclear layers.
Hard Exudates – Extracellular collections of macrophages within the outer plexiform layer, derived from ingested leaked lipid & proteins from the abnormal vessels.
Retinal edema – Fluid collects initially between the outer plexiform and inner nuclear layer; secondary edema appear between the inner plexiform and nerve fibre layers.
Q-92. Soft exudates deposits seen in which layer of retina?
a) Outer plexiform layer
b) Inner nuclear layer
c) Ganglionic layer
d) Rods and cones cell layer
Answer: Ganglionic layer
Explanation:
Cotton wool spots result from occlusion of retinal pre-capillary arterioles supplying the nerve fibre layer with concomitant swelling of local nerve fibre axons. Also called “soft exudates” or “nerve fibre layer infarctions” they are white, fluffy lesions in the nerve fibre layer.
The retinal nerve fiber layer (RNFL) is formed by retinal ganglion cell axons and represents the innermost layer of the fundus.
Q-93. Critical angle of corneal-air interface is
a) 46°
b) 66°
c) 36°
d) 56°
Answer: 46°
Explanation:
The challenge of visualizing the anterior chamber angle structures lies with the critical angle.
The critical angle for the cornea-air interface is approximately 46°.
Corneal lenses or mirrors are needed to overcome the internal reflection of light. In direct gonioscopy, the anterior curve of the contact lens is such that the critical angle is not reached, and the light rays are refracted at the contact lens-air interface.
In indirect gonioscopy, the light rays are reflected by a mirror in the contact lens and leave the lens at nearly a right angle to the contact lens-air interface.
Q-94. Ex-press implant of glaucoma is made up of
a) Titanium
b) Silicon
c) Stainless steel
d) None
Answer: Stainless steel
Explanation:
The Ex-Press Mini Glaucoma Shunt is biocompatible device for implantation under the conjunctiva for controlling intraocular pressure (IOP).
It is a non-valved, MRI compatible, stainless steel device with a 50 micron lumen. It has an external disc at one end and a spur-like extension on the other to prevent extrusion.
Q-95. Ascorbate and alpha tocopherol levels are maintained in the lens by
a) Glucose
b) Fatty acids
c) Glutathione
d) Glycoprotein
Answer: Glutathione
Explanation:
Ocular concentrations of glutathione are very high when compared with most other tissues and decreased levels of glutathione are associated with both age related macular degeneration and cataract, and in diabetic patients with similar conditions.
Glutathione is critical in maintaining the reduced state of sulfhydryl-containing proteins in the lens.
Glutathione normally functions to maintain ascorbate, alpha-tocopherol, and other cellular components in reduced states.
Q-96. Pt presents with chuna particles fallen into the eye. Which of the following should not be done?
a) Repeated irrigation of conjunctival sac with NS
b) Frequent instillation of Na citrate drops
c) Thorough slit lamp exam
d) Double eversion of lids and removal of chuna particles
Answer: Thorough slit lamp exam
Explanation:
Kids have lost eyesight due to sudden bursting of packets of chuna or calcium hydroxide, an additive used with chewing tobacco, and children are at the risk of “irreversibly” damaging their eyes in families where this habit is prevalent.
Once chuna enters the eye, it sticks into the eye under the eyelid. Even thorough washing doesn’t remove all the particles.
Chuna particles leach from under the eyelid and get into cornea, destroying its outer covering called epithelium.
The tear secretion system gets completely destroyed and the eye becomes dry. It can lead to complete blindness.
Immediate response to such a situation should be vigorous washing of eye with water or with 0.9% saline if available.
After irrigation, the conjunctival fornices should be examined for chemical embedded in the tissue and swept with a swab to remove trapped particles. The superior fornices are exposed by using double eyelid eversion
The incidence of ulceration and perforation in the cornea of alkali-injured eyes is significantly reduced by treatment with tri-sodium citrate or sodium ascorbate. Topical citrate reduces the inflammatory response in the cornea by inhibiting polymorphonuclear leukocytes.
Q-97. Which of the following organism causes corneal perforation in just 2 days?
a) Staphylococcus
b) Pseudomonas
c) Diphtheria
d) Aspergillus
Answer: Pseudomonas
Explanation:
Eighty percent of bacterial corneal ulcers are caused by Staphylococcus aureus, Streptococcus pneumoniae and Pseudomonas species. Pseudomonas aeruginosa is the most frequent and the most pathogenic ocular pathogen which can cause corneal perforation in just 2-3 days.
The most common organisms associated with contact lens related bacterial keratitis are Pseudomonas aeruginosa and Staphylococci.
Q-98. Gas used in retinopexy
a) Co2
b) SF6
c) Nitrous oxide
d) None
Answer: SF6
Explanation:
Pneumatic retinopexy (PR) is an alternative to scleral buckling for the surgical repair of selected retinal detachments.
A gas bubble is injected into the vitreous cavity, and the patient is positioned so that the bubble closes the retinal break (s), allowing absorption of the sub-retinal fluid.
Cryotherapy or laser photocoagulation is applied around the retinal break(s) to form a permanent seal.
Sulfur hexafluoride (SF6) is the gas most frequently used for PR, followed by per-fluoro-propane (C3F8).
Q-99. Gene commonly indicated in congenital cataract
a) CRYGS3
b) PAX6
c) PITX3
d) LMX1B
Answer: CRYGS3
Explanation:
CRYGS3 mutation causes progressive cortical cataract in human.
Q-100. The light peak/dark trough (L/D) ratio in normal electro-oculogram reading
a) 1
b) 1.5
c) > 185 %
d) < 185 % Answer: > 185 %
Explanation:
The electro-oculogram (EOG) is an electro-physiologic test that measures the existing resting electrical potential between the cornea and Bruch’s membrane.
The smaller amplitudes are recorded when the eyes make the saccadic eye movements in the dark (dark trough); the peak amplitude is recorded against a steady light background (light peak).
The light peak/dark trough (L/D) ratio is an index (Arden index) used to assess retinal function.
An Arden ratio of 1.80 or greater is normal, 1.65 to 1.80 is subnormal, and < 1.65 is significantly subnormal.