Accommodation and its anomalies ppt by Saharukh
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This document defines accommodation as the ability to see near objects clearly by increasing the converging power of the lens. It describes the mechanism of accommodation, which involves contraction of the ciliary muscles and relaxation of the suspensory ligament, allowing the lens to become more spherical. It defines the far point and near point of the eye and discusses range and amplitude of accommodation. Finally, it summarizes several anomalies of accommodation, including presbyopia, insufficiency of accommodation, paralysis of accommodation, and spasm of accommodation.
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Accommodation
Accommodation is the eye's ability to focus on near objects by increasing the lens power. It allows diverging rays from near objects to focus on the retina. Key aspects of accommodation include the near and far points of accommodation and the amplitude or range of accommodation which decreases with age causing presbyopia. Accommodation involves changes in lens curvature and thickness brought about by ciliary muscle contraction and zonule relaxation. Several theories have been proposed to explain the mechanism of accommodation. Anomalies of accommodation include diminished accommodation, presbyopia, paralysis and excess or spasm of accommodation.
Accommodation
1. Accommodation is the mechanism by which the eye changes its refractive power to focus on objects at different distances. It occurs when the ciliary muscle contracts, allowing the lens to become more curved and powerful.
2. Accommodation has two components - physical accommodation involving the actual deformation of the lens, and physiological accommodation involving the contractile power of the ciliary muscle. Terminologies like far point, near point, and amplitude of accommodation are used to describe accommodation.
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Accommodation
Accommodation is the eye's ability to focus on near objects by increasing the lens power. It allows diverging rays from near objects to focus on the retina. Key aspects of accommodation include the near and far points of accommodation and the amplitude or range of accommodation which decreases with age causing presbyopia. Accommodation involves changes in lens curvature and thickness brought about by ciliary muscle contraction and zonule relaxation. Several theories have been proposed to explain the mechanism of accommodation. Anomalies of accommodation include diminished accommodation, presbyopia, paralysis and excess or spasm of accommodation.
Accommodation
1. Accommodation is the mechanism by which the eye changes its refractive power to focus on objects at different distances. It occurs when the ciliary muscle contracts, allowing the lens to become more curved and powerful.
2. Accommodation has two components - physical accommodation involving the actual deformation of the lens, and physiological accommodation involving the contractile power of the ciliary muscle. Terminologies like far point, near point, and amplitude of accommodation are used to describe accommodation.
3. Accommodation is assessed using tests like RAF rule, pushup test, and dynamic retinoscopy to measure the near point, amplitude, and accommodative response respectively. Assessment of dynamic accommodation involves testing accommodative facility using
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This document provides an overview of retinoscopy, including:
- Retinoscopy is an objective method of measuring the optical power of the eye using light reflections.
- There are different types of retinoscopes and retinoscopy techniques including static, dynamic, near, and wet retinoscopy.
- The document outlines the basic procedure for performing retinoscopy, including neutralizing reflexes with trial lenses to obtain a prescription.
- Sources of error and special techniques like Mohindra and Bell retinoscopy are also discussed.
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The near point of convergence is defined as the point of intersection of the lines of sight of the eyes when maximum convergence is used. It is measured as the distance from this point of intersection to the midpoint between the eyes. Measuring the near point of convergence involves having a patient fixate on a target that is slowly moved toward them while maintaining fusion until their eyes can no longer converge or they see double. This distance is used to assess a patient's ability to converge their eyes for near vision tasks. A near point further than 10cm may indicate convergence insufficiency while one closer than 5cm suggests convergence excess.
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This document discusses anomalies of accommodation, including diminished or deficient accommodation (presbyopia, cycloplegia, insufficiency), and increased accommodation (excessive accommodation, spasm). Presbyopia is an age-related decrease in accommodation due to hardening of the lens or weakening of the ciliary muscles. Treatment includes optical corrections like glasses or surgery. Insufficiency of accommodation can be due to premature lens sclerosis or ciliary muscle weakness from various systemic or local causes. Treatment addresses the underlying cause and includes near vision corrections. Excessive accommodation can occur in young hyperopes or myopes doing excessive near work, while spasm of accommodation is an abnormal excessive accommodation outside voluntary control.
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Aniseikonia refers to an unequal apparent size of images seen by the two eyes. It can result from differences in refractive errors between the eyes (refractive aniseikonia) or differences in the distribution of retinal elements (basic aniseikonia). Symptoms include headaches, asthenopia, and difficulties with mobility or fusion. Aniseikonia is usually caused by anisometropia above 1.50-2.00 diopters and analyzing ocular components can help determine if it is due to refractive or axial differences.
By pd examination of a squint
Please look at the light and tell me what you see
Patient: I see two lights that are side by side
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Patient: As you move the lights closer, they are now merging into one light.
Assistant: Thank you. That demonstrates you do not have diplopia in primary position. Now I am going to move the light up, down, left, and right. Please tell me if you see one light or two lights as I move it to different positions.
This tests for diplopia in different gazes which helps localize the site of the problem causing diplopia
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This document provides an introduction to binocular single vision (BSV) including its definition, grades, advantages, development, mechanisms, anomalies, and investigations. BSV is the coordinated use of both eyes to see a single image through the process of fusion. It develops in early childhood as the visual axes align and fusional movements are established. Maintaining BSV provides advantages like stereopsis and binocular summation. Investigations of BSV assess fusion, retinal correspondence, suppression, and stereopsis.
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Retinoscopy is the primary objective method for determining a patient's refractive error. It involves using a retinoscope to illuminate the retina and observe the movement of the reflected light. For myopic patients, the light moves in the opposite direction of the retinoscope's movement, while for hyperopic patients it moves in the same direction. The goal is to find the neutralization point where no movement is seen, indicating the proper refractive correction. Factors like the working distance, type of mirror used, and patient's fixation can impact results. Retinoscopy is useful for initial refractive estimates and screening for ocular conditions.
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Dynamic retinoscopy srijana
Dynamic retinoscopy is used to objectively determine a patient's refractive error when their accommodation is active. It involves having the patient fixate on a near target while the examiner performs retinoscopy. The direction of the retinoscopic reflex indicates whether the eye is focused in front of, behind, or aligned with the retinoscope. Various methods of dynamic retinoscopy have been developed, including Monocular Estimation Method, Bell retinoscopy, and Nott retinoscopy. Dynamic retinoscopy can reveal a patient's lag of accommodation, or the difference between their accommodative response and the stimulus provided by the near target. A normal lag is between +0.50D to +0.75D.
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This document describes how to test for the near point of accommodation (NPA) and near point of convergence (NPC). For NPA testing, the examiner places a near testing card at 16 inches from the patient's eye and moves it closer until the letters blur, recording the distance. This is repeated for each eye. For NPC testing, the examiner holds a target at 16 inches from the patient and moves it closer until the image doubles or one eye deviates, recording the distance from the nose. Both tests measure the closest point an image can remain clear and single.
Vergence
Vergence eye movements allow for the convergence and divergence of the eyes to change the angle formed by the visual axes. The vergence system includes voluntary and reflexive components. Reflex vergence is composed of tonic, accommodative, proximal, and fusional vergence responses. Accommodative convergence is the vergence response stimulated by accommodation. The AC/A ratio represents the relationship between accommodation and convergence. Maintaining the proper balance between all the components of the vergence system is important for managing vergence and binocular vision problems.
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Ophthalmic dispensing
The document discusses the process of optical dispensing, including defining optical dispensing, measuring frames and lenses, selecting frames based on facial shapes, lens materials and coatings, and the process of laying off, cutting, and edging lenses to fit into frames. Key steps include determining facial measurements, selecting appropriate frames, measuring pupillary distance, marking lenses, cutting lenses to shape using hand or automatic edgers, and fitting the finished lenses into frames.
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Accommodation
The document defines accommodation as the eye's ability to focus on near objects by changing the lens curvature. It describes how the ciliary muscle controls the lens shape by relaxing the zonules attached to the lens capsule. When relaxed, the elastic capsule makes the lens more convex to focus on nearby objects. The range and amplitude of accommodation are defined. Presbyopia and other accommodation anomalies like insufficiency, paralysis, and spasm are explained in terms of causes, symptoms, and treatments.
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Accomodation
(1) Accommodation is the mechanism by which the eye changes refractive power by altering the shape of the lens to focus on objects at different distances.
(2) Theories of accommodation include the relaxation theory of Helmholtz which proposes that contraction of the ciliary muscle relaxes the suspensory ligaments of the lens allowing it to take on a more spherical shape.
(3) Accommodative anomalies include decreased accommodation seen in presbyopia and other conditions, as well as increased accommodation seen in conditions like accommodative excess or spasm.
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1. Accommodation is the process by which the eye increases optical power to maintain clear focus on nearby objects. During accommodation, the ciliary muscles contract and relax zonular tension on the lens, allowing the lens to become more convex.
2. Presbyopia is the age-related loss of accommodation due to hardening of the lens and weakening of the ciliary muscles. It results in difficulty seeing objects close up and is treated with convex lenses.
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This document discusses accommodation and presbyopia. It defines accommodation as the ability of the eye to change focus from distant to near objects by changing the shape of the lens. Accommodation decreases with age in a process called presbyopia as the lens becomes less flexible. Presbyopia symptoms include difficulty seeing close objects clearly and can be treated with reading glasses, bifocal glasses, or multifocal contact lenses to restore near vision. The document also covers topics like ciliary muscle function, amplitude of accommodation measurement, and factors affecting presbyopia.
Accommodation
Accommodation is the process by which the eye focuses on near objects. It occurs through changes in the shape and thickness of the elastic lens, induced by contraction of the ciliary muscle. The amplitude of accommodation is the difference between the near point and far point, measured in diopters. Accommodative ability peaks at around 10 years old and gradually declines with age. Presbyopia is the age-related loss of accommodation, causing difficulty with near vision. Other anomalies include insufficiency, spasm, paralysis and excessive accommodation, which can be caused by factors like refractive error, drugs, trauma or ocular disease. Assessment of accommodation involves measuring the near point, amplitude and facility of accommodation using tools like lenses, rulers and
physiology of vision
ocular anatomy fluid system glaucoma lens cataract phototransduction field visual acuity ocular movement errors of refraction light reflex accommodation corneal reflex visual pathway and its lesions
Correcting presbyopia - Modern Options
This document provides an overview of modern options for correcting presbyopia. It discusses both static and dynamic correction techniques. Static techniques include glasses, contact lenses, corneal procedures like inlays/onlays, and intraocular lenses using monovision or being multifocal. Dynamic techniques aim to restore accommodation and include accommodating intraocular lenses, lens refilling procedures, and scleral expansion techniques. The document provides details on many of these specific procedures.
Eye physiology 1 bds.pptx physiology of eye
The document summarizes key aspects of eye physiology, including:
1. The eye contains two fluid systems - the vitreous humor and aqueous humor which help maintain intraocular pressure.
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3. Errors of refraction like myopia, hyperopia and astigmatism occur when light is not properly focused on the retina. Accommodation allows the eye to focus on near objects and presbyopia is the loss of this ability with age.
Human eye and colourful world
The human eye is one of the most valuable and sensitive sense organs in the human body. It enables us to see the wonderful world and colours around us.
Structure of eye:
The human eye has the following main parts:
Cornea: It is the transparent spherical membrane covering the front of the eye. Light enters the eye through this membrane.
Crystalline lens: The eyes lens is a convex lens made of a transparent, soft and flexible material like a jelly made of proteins.
Iris: It is a dark muscular diaphragm between the cornea and the lens. It controls the size of the pupil. It is the colour of the iris that we call as the colour of the eye.
Pupil: It is a small hole between the iris through which light enters the eye. In dim light, it opens up completely due to expansion of iris muscles, but in bright light it becomes very small due to contraction of iris muscles.
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Accommodation and its anomalies ppt by Saharukh
- 1. Accommodation & It’s Anomalies By Saharukh Alam D Optometry Date 02.09.2021
- 2. Definition of Accommodation It is the ability to see the near object clearly by increasing converging power of lens. At Rest, the radius of curvature of anterior surface of lens is 10 mm and posterior surface in 6 mm. In Accommodation, the curvature of anterior surface of lens changes but the posterior surface remains same.
- 3. Mechanism of Accommodation In Unaccommodative State, The suspensory ligament is in tension, so the lens remains flat. In Accommodation, Ciliary muscles contract > Reduction of circle formed by ciliary processes > Suspensory ligament relaxes > Lens then alter it’s shapes to become more spherical.
- 4. Far Point of Eye It is also called as Punctum remotum. It is a farthest point at which object can focus on retina when the ciliary muscle relaxed. Near Point of Eye It’s also called as Punctum proximum. It is the nearest point at which the small objects can be seen clearly after full accommodation.
- 5. ❏ Range of Accommodation:- It is a difference between the far point and near point. So, Range of Accommodation = Far Point - Near Point ❏ Amplitude of Accommodation:- It is the difference in refractive power of eye between the far point and near point. It gradually diminishes throughout the life. So, Amplitude of Accommodation = Dioptric power of Far Point - Dioptric power of Near
- 6. Anomalies of Accommodation ❖ PRESBYOPIA: This is a physiological aging process, in which the near point gradually reduce. ➢ Causes:- i. Lens capsule is less elastic. ii. Weakness of ciliary muscle. ➢ Symptoms:- i. Gradual difficulty in reading. ii. Headache. ➢ Treatment:- i. Used Convex Lens. ii. Contact Lens used. iii. Presbyopic LASIK
- 7. ❖ INSUFFICIENCY OF ACCOMMODATION: In this condition, the accommodation is lower limit of normal for the patient’s age. ➢ Causes:- i. Early Presbyopia. ii. Weakness of ciliary muscle. ➢ Symptoms:- i. Early Strain. ii. Difficulty in near work. ➢ Treatment:- i. Use convex lens. ii. Accommodation Exercises.
- 8. ❖ PARALYSIS OF ACCOMMODATION: Here the accommodation is paralysied due to some reasons. ➢ Causes:- Unilateral: i. For used Cycloplegics. ii. Paralysis of 3rd CN nerve. Bilateral: i. Due to diphtheria. ii. Diabetes. etc ➢ Treatment:- i. Treatment of causes. ii. Myotics are useful. iii. If the paralysis is parmanent, suitable convex lens should be used.
- 9. ❖ SPASM OF ACCOMMODATION: It refers to prolonged contraction of ciliary muscles. ➢ Causes:- i. Found mainly in children. ii. Myopes are more affected than Hyperopes. iii. Installation of miotics. ➢ Symptoms:- i. Asthenopia, ii. Blurring of distant vision. ➢ Treatment:- i. Atropinization for a few days or weeks. ii. Assurance and Psychotherapy.
- 10. Thank You All the Best