Myopia and Hypermetropia MCQs

2 D is already given as power to focus at far so Amplitude will be 1/ 0.1 - 2 = 10 -2 = 8 D Reference: Khurana Optics 2/e

Shortening of eyeball induces a hypermetropia of + 3 D Reference: Khurana Optics 2/e

Pseudo Myopia: This type of myopia is called as false appearance of myopia that occurs due to excessive accommodation and spasms of accommodation.This type of myopia usually manifest the execessive amount of myopia and decreased amount of hypermetropia. It could cause severe headache with asthenopic complaints. Reference: Khurana Optics 2/e

(Normal axial length is 24mm). A decrease of 1mm in axial length produces a hypermetropia of 3.0D. Curvature Hypermetropia: When the curvature of the cornea or lens is flatter than normal. An increase of 1mm in its radius of curvature produces a hypermetropia of 6. Reference: Khurana Optics 2/e

C/I of LASIK Age CCT Unstable refractive error for last 6 months Keratoconus Pregnancy Any active inflammatory/ infective intraocular disorder Reference: Khurana Optics 2/e

Pathological/degenerative myopia More frequency of degenerations like lattice, snow flake More chances of Retinal detachments Choroidal hemorrhage in macula: foster fuch’s spot Lacquer cracks: breaks in bruch’s membrane Myopic crescent: disparity b/t sclera ( globe enlarges) and RPE Posterior staphyloma: ectasia of sclera Large disc, large disc cup ratio Visibility of choroidal vessels, RPE thinning Tilted disc: dragging of retina nasally over disc Other features in myopia Large eyeball Far point comes near Does not accommodate for near → convergence insufficiency → exophoria Deep AC POAG, Pigmentary glaucoma, nuclear cataract Low ocular rigidity Reference: Khurana Optics 2/e

With movement of the red reflex along the movement of the retinoscope indicates either emmetropia or hypermetropia or myopia of less than 1D. Against movement of the red reflex to the movement of the retinoscope implies myopia of more than 1D No movement implies myopia of – 1D Bright and fast shadow is seen in the pupillary area which moves rapidly with the movement of the mirror, in patients with low degrees of refractive errors. Dull reflex which moves slowly with the movement of the mirror is seen in patients with high degrees of ametropia. When using a streak retinoscope of red reflex is narrow with a high degree of ametropia and the wide reflex means a low degree of ametropia. Reference: Khurana Optics 2/e

Two typical ophthalmoscopic appearances are seen in high myopia—changes at the disc typified in the development of a myopic crescent, and changes in the central area of the fundus described as chorioretinal myopic degeneration. Degenerative changes also occur at the periphery of the retina which may lead to a retinal detachment, and degenerative changes in the vitreous are common, giving rise to dust-like vitreous opacities or large floaters composed of elements of the vitreous framework. These 'floaters' are seen more plainly by myopic than by other eyes because the entoptic image is larger. These degenerative changes may have serious visual consequences; in fact, they are among the more common causes of severe visual disability. Reference: Parson ch 8, P. 79