The intrinsic muscles of the eye are muscles that control the movements of the lens and pupil, and are therefore involved in the accommodation of vision. There are three smooth muscles that make up this group; Musculiciliary pupils, dilators and pupils of the sphincter. Question 9. A convex lens of 4D thickness is placed at a distance of 40 cm from a wall. How far from the lens should a candle be placed for its image to be formed on the wall? Answer: The candle must therefore be placed 66.66 cm from the lens. Question 51. What happens to the spacing of the image in the eye when we increase the distance from an object to the eye? Answer: In the eye, the distance of the image (distance between the lens of the eye and the retina) is fixed and cannot be changed. So if we increase the distance of an object, the spacing of the images does not change. Both types of glaucoma are treated with muscarinic receptor agonists, which cause the ciliary muscle to contract, leading to the opening of the trabecular mesh. Once this happens, the aqueous humor can flow through the Schlemm canal and eventually lead to a decrease in intraocular pressure. Question 7. Answer the following questions from the information above. (TS June 2019) i) What does the visual defect in „D“ suffer from? Why is this happening? (ii) What visual defects can be corrected using a biconcave lens? iii) Who suffers from a visual defect similar to „B“? (iv) Which of the above has no visual defect? Answer: i) 1) The visual defect of person „D“ is presbyopia.
2) Presbyopia occurs due to a gradual weakening of the ciliary muscles and a decrease in the flexibility of the lens of the eye. This effect can be observed in the elderly. (ii) The visual defect of person A can be corrected using a biconcave lens. (iii) Person „C“ suffers from a visual defect similar to that of „B“. (iv) Person „E“ has no visual defect. Presynaptic parasympathetic signals from the Edinger-Westphal nucleus are transported by the cranial nerve III (the oculomotor nerve) and pass through the ciliary ganglion via the postnodal parasympathetic fibers that migrate into the short ciliary nerves and supply the ciliary body and iris. Parasympathetic activation of muscarinic M3 receptors causes contraction of the ciliary muscles. The effect of contraction is to reduce the diameter of the ciliary muscle ring, which leads to the relaxation of zozonule fibers, the lens becomes more spherical and increases its power to refract light for near vision. [Citation needed] The effect of the contraction or relaxation of the ciliary muscles on the focusing power of the lens. When the ciliary muscle is contracted, the lens becomes more spherical – and has increased the focusing power – due to a reduction in tension on the zonal fibers( a). As the ciliary muscles relax, these fibers become tight and pull the lens into a flatter shape that has less focusing power (b).
Accommodating fatigue, the decrease in focusing power during pursuit near work, leads to hyperopic defocusing, which can in principle act as an incentive for eye growth. The appendages of the ciliary muscle have not yet been determined. According to some authors, the ciliary muscle comes from a protrusion of the sclera in the anterior chamber of the eye, also known as the spur of the sclerus. The outermost longitudinal layer of the ciliary muscle fits into the anterior third of the choroid, while the radial fibers reach the connective tissue of the base of the ciliary processes. Question 11. When Mohan looked at the white light through a transparent scale, he observed certain colors. Predict and write the phenomenon involved in its observation. (AP SCERT: 2019-20) Answer: The reflex pathway includes the optic nerve (CN II), the visual and frontal cortex, the oculomotor and accessory nucleus, and the oculomotor nerve (CN III). When adaptation is necessary, the optic nerve sends the first impulses to the primary visual cortex through the lateral cynicating body and optical radiation. From there, the impulse moves through the visual association cortex to the accessory/Edinger-Westphal nucleus of the oculomotor nucleus in the midbrain. Efferent parasympathetic fibers carried by the synapse of the oculomotor nerve with the ciliary ganglion, which sends postnodal fibers to the ciliary muscle. There is a whiff of existing evidence in the literature that the ciliary muscle also receives innervation of the sympathetic fibers of the autonomic nervous system (ANS).
Supposedly, these fibers provide the inhibitory impulses and thus inhibit the accommodation reflex. The condition of the ciliary muscle changes depending on whether we observe distant or nearby objects. Looking at the removed object, the ciliary muscle is relaxed, the zonal fibers are tightened, and the lens is flattened. In this state, the refractive power of the lens is sufficient to form a clear image of the object focused on the retina. However, to focus on a nearby object, the internal structures of the eye must adapt, which is possible through the adaptation process. The contraction of the ciliary muscle relaxes the zonal fibers, thereby increasing the convexity of the lens, which leads to an adaptation of near vision. It also regulates the pore size of the trabecular network. The ciliary muscle receives parasympathetic fibers from the short ciliary nerves that come from the ciliary ganglion. Sympathetic postnodal fibers are part of the cranial nerve V1 (nasociliary nerve of the trigeminal nerve), while the presympathetic parasympathetic fibers of the ciliary nodes come from the oculomotor nerve.
[7] Postnodal sympathetic innervation is caused by the upper cervical lymph nodes. [8] Question 6. What happens if the ciliary muscles do not contract and expand? Guess and write. (TS June 2018) Answer: Aqueous humor is a transparent fluid in the eye that provides internal structures with nutrients and maintains intraocular pressure. It is secreted by the cells of the ciliary body in the posterior chamber of the eye. It circulates through the pupil and enters the anterior chamber. From there, the liquid leaves the eye through the small kanas located on the limb of the eye (the schlemm channels). The process of secretion of aqueous humor must be in synergy with drainage. If this is not the case, the accumulation of this fluid can lead to an increase in intraocular pressure, which is the main risk factor for glaucoma. The ciliary muscle is an intrinsic muscle of the eye that forms as a smooth muscle ring[3][4] in the middle layer of the eye, uvea or (vascular layer). It controls the accommodation to view objects at different distances and regulates the flow of watery humor in the SchlemmSche Kanal. It also changes the shape of the lens in the eye, but not the size of the pupil[5] performed by the sphincter and dilator pills.
Question 38. Two convex lenses of 1D and 2D power are combined to form a new lens. So what is the resulting power and focal length of the lens? Answer: P1 = 1 D; P2 = Resulting power 2D P = P1 + P2 = 1 + 2 = 3D P = (frac{1}{f}) (f in meters) ∴ f= (frac{1}{P}) = (frac{1}{3}) = 0.3333 m = 33.33 cm. .