Tag: biology

Ciliary body and the attached suspensory ligament change the shape (flattened or round) of the lens through relaxation and contraction of ciliary muscles and thereby the focal length to focus on the distant and near object. Contraction of ciliary muscles releases the suspensory ligaments and allow the lens to become round (convex) while relaxation of these muscles makes the lens taut. Since ciliary muscles are involved in accommodation required for close vision, loss of their contraction would not cause loss of vision but would affect the close vision only. The amount of light entering retina is controlled by the iris. 

The choroid is a layer of eyeball. The eyeball has three coats namely sclera, choroid, and retina. The choroid is middle dark pigmented thin vascular layer of the eyeball and is characterized by the presence of many blood vessels. Retina forms the innermost layer of the eye. 

Compound eyes are the characteristic feature of insects. The compound eye of insects consists of many ommatidia, each of which is a separate visual unit that portrays each object into several broken pieces. This type of vision is called as mosaic vision. Among the given options, housefly is an insect and has ommatidia as a unit of an eye. Pheretima (annelid) and pila and sepia (molluscs) do not have compound eyes. 

The choroid is the part of the vascular coat in eyes. It also contains blood vessels that provide nourishment to the eye. It is pigmented towards a rear of the eye and absorbs light. It is a dark brown in colour. It darkens the cavity of the eyeballs to prevent internal reflection of light that might blur the image.

• The word ''Opthalmology'' comes from the Greek roots ''Ophthalmol'' means ''Eye'' and ''Logos'' means ''Study''. Hence Ophthalmology literally means the ''The science of eyes''. 
• An Ophthalmologist is a specialist in medical and surgical eye problems.
• Hence Ophthalmology is the study of Caring, diagnosis and cure of eye diseases.
• So, the correct answer is 'Ophthalmology'.