Anatomy and Development of Eye MCQs

Ans. C. Inferonasal All clobomas (including iris) are mostly inferonasal.

Dimensions of an adult eyeball Anteroposterior diameter : 24 mm Horizontal diameter : 23.5 mm Vertical diameter : 23 mm Circumference : 75 mm Volume : 6.5 ml Weight : 7 g Reference: Comprehensive Ophthalmology 7 th ed. – A.K.Khurana, Ch-1 Anatomy and development of eye

Dimensions of an adult eyeball Anteroposterior diameter : 24 mm Horizontal diameter : 23.5 mm Vertical diameter : 23 mm Circumference : 75 mm Volume : 6.5 ml Weight : 7 g Reference : Comprehensive Ophthalmology 7 th ed. – A.K.Khurana, Ch-1 Anatomy and development of eye

Cloquet’s canal, which contains the primary vitreous at birth, runs straight from the lens to the optic disc. The secondary vitreous eventually becomes liquefied and shrinks. Between 40 and 70 years of age in most individuals and earlier in myopes, vitreous liquefaction or syneresis occurs; the vitreous mass gradually shrinks and collapses, causing its separation from the retina, a condition known as PVD. Condensations of the vitreous fibrils are present within this liquefied vitreous and are visible as floaters. Reference: Parson’s diseases of the eye, 23 rd ed. Ch 17-Diseases of retina and vitreous

Explanation: The superior oblique and levator palpebrae muscles originate in the orbital apex superior to the annulus. All the recti muscles arise in a fibrous ring around the optic foramen to the nasal side of the axis of the eye, the annulus of Zinn, and are inserted in the sclera by flat tendinous insertions about 10 mm broad. The medial rectus is inserted into the sclera about 5.5 mm to the nasal side of the corneoscleral margin, the inferior rectus 6.6 mm below, the lateral rectus 7 mm to the temporal side and the superior rectus 7.75 mm above The inferior oblique originates behind the lacrimal fossa.

The cornea and the crystalline lens are the avascular structures of the eye. The remaining structures are supplied by the branches of ophthalmic artery which is a branch of internal carotid artery. Reference: Parson, 22nd Edition, Pg no. 238-244.

The lateral rectus is supplied by one anterior ciliary artery. Reference : kurana 2/e, p. 47

The inferior oblique muscle has its origin on the maxillary bone just posterior to the inferior medial orbital rim and lateral to the nasolacrimal canal. The inferior oblique is the only extraocular muscle to have its anatomic origin in the anterior orbit. Reference: Kanski, 5 th ed, Page no. 529.