TNPG 2006 OPTHALMOLOGY

OPTHALMOLOGY

219) concave lens is a

a. Diveging lens

b. Converging lens

c. Any of the above

d. None of the above

Answer (a) Diverging Lens

Reference: Khurana 3^rd Edition Page 47

220) Type of Surgery to Correct myopia

a. LASIK surgery

b. Dacrocystorhinostomy

c. Tarsorrpaphy

d. Enucleation

Answer (a) LASIK

Reference: Khurana 3^rd Edition Page 77

221) Strum's Conoid is associated with

a. Astigmatism

b. Glaucoma

c. Cataract

d. Retinal Detachment

Answer (a ) Astigmatism

Reference: Parson 18^th Edition Page 45

222) Retinitis pigmentosa is associated with all except

a. Goldenhar syndrome

b. Refsum’s Syndrome

c. Lawrence Moon Biedl

d. Usher’s Syndrome

Answer (a) Goldenhar Syndome

Reference: Khurana 3^rd Edition Page 261

223) Image in Direct opthalmoscopy is

a. Virtual Inverted magnified

b. Real Inverted Magnified

c. Real Erect and Magnified

d. Virtual, Erect and Magnified.

Answer (d) Erect, Virtual, Magnified

Reference: Khurana 3^rd Edition Page 34

224) To maintain the transperancy of cornea, the endothelial cell density should be at least

a. 3500 cells/sq.mm

b. 2500 cells/sq.mm

c. 1500 cells/sq.mm

d. 500 cells/sq.mm

Answer (d) 500 cells / sq. mm

Reference: Murphy C, et al. Prenatal and postnatal cellularity of the human corneal endothelium. A quantitative histologic study. Invest Ophthalmol Vis Sci 1984;25:312-22. and "Corneal endothelium." Wikipedia, The Free Encyclopedia. 22 Jul 2006, 05:15 UTC. Wikimedia Foundation, Inc. 9 Nov 2006 <http://en.wikipedia.org/w/index.php?title=Corneal_endothelium&oldid=65162345>.

The corneal endothelium is embryologically derived from the neural crest. The postnatal total endothelial cellularity of the cornea (approximately 300,000 cells per cornea) is achieved as early as the second trimester of gestation. Thereafter the endothelial cell density (but not the absolute number of cells) rapidly declines in direct proportion to the areal growth of the fetal cornea, achieving a final adult density of approximately 2400 - 3200 cells/mm². The normal corneal endothelium is a hexagonal monolayer of uniformly sized cells. This honeycomb tiling scheme yields the greatest efficiency, in terms of total perimeter, of packing the posterior corneal surface with cells of a given area.

To function properly, the endothelium must be intact. Transparency can be lost when endothelial cell density is reduced below a critical level, 500 cells/mm². Endothelial cell density in a normal human adult cornea is between 1,500 and 2,000 cells/mm². Infants have a higher density, even more than 3000 cells/mm²

Altered cell shape and the resulting decrease in cell-to-cell connections compromise the barrier function of corneal endothelium and can result in corneal edema and loss of visual acuity. (Right figure) Schematics of corneal endothelial cell density are shown (l to r) in young individuals, older individuals, and those with loss of monolayer integrity leading to gaps between cells (see arrow).

Corneal endothelial cells are post-mitotic and divide rarely, if at all, in the post-natal human cornea. Wounding of the corneal endothelium, as from trauma or other insults, prompts healing of the endothelial monolayer by sliding and enlargement of adjacent endothelial cells, rather than mitosis. Endothelial cell loss, if sufficiently severe, can cause endothelial cell density to fall below the threshold level needed to maintain corneal deturgescence. This threshold endothelial cell density varies considerably amongst individuals, but is typically in the range of 500 - 1000 cells/mm². Corneal edema can also occur as the result of compromised endothelial function due to intraocular inflammation or other causes. Excess hydration of the corneal stroma disrupts the normally uniform periodic spacing of Type I collagen fibrils, creating light scatter. In addition, excessive corneal hydration can result in edema of the corneal epithelial layer, which creates irregularity at the optically critical tear film-air interface. Both stromal light scatter and surface epithelial irregularity contribute to degraded optical performance of the cornea and can compromise visual acuity.

225) Long ciliary nerve supplies

a. Dilator Pupillae

b. Sphincter pupillae

c. Levator Palpabrae superioris.

d. None of the above

Answer ( a) Dilator Pupillae

Reference: Gray 38^th Edition Page 1234

226) Presbyopia is

a. insufficiency of accomodation,

b. decrease in elasticity and plasticity of the crystalline lens

c. Age related decrease in the power of ciliary muscles

d. all of the above

Answer (d) All of the above

Reference: Khurana 3^rd Edition Page