3. Binocular Single Vision Part 2

[Audio] NON- STRABISMUS BINOCULAR ANOMALIES ANOMALIES Of ACCOMMODATION Diminished or deficient accommodation 1. physiological (presbyopia) 2. Pharmacological (cycloplegia) 3-pathological Insufficiency of accommodation Ill-sustained accommodation Accommodation inertia Paralysis of accommodation Increased Accommodation Excessive accommodation Spasm of accommodation ANOMALIES Of CONVERGENCE Convergence insufficiency Convergence insufficiency associated with accommodative insufficiency Convergence paralysis Convergence spasm.

[Audio] ANOMALIES OF ACCOMMODATION Increased Accommodation 1. physiological (presbyopia) 2. Pharmacological (cycloplegia) 3-pathological Insufficiency of accommodation Ill-sustained accommodation Accommodation inertia Paralysis of accommodation spasm of accommodation Excessive accommodation Diminished or deficient accommodation.

[Audio] 1.Presbyopia Age-related condition characterized by reduced accommodative power, leading to progressive difficulty with near vision. Not classified as an error of refraction. Typically begins between 40-45 years of age. Causes of Presbyopia: Age-related changes in the lens: Decreased elasticity of the lens capsule. Progressive increase in size and hardness (sclerosis) of lens substance. Age-related decline in ciliary muscle power. Causes of Premature Presbyopia: Uncorrected hypermetropia. Premature sclerosis of the crystalline lens. General debility causing presenile weakness of ciliary muscle. Chronic simple glaucoma..

[Audio] Symptoms: Difficulty in near vision: Inadequate vision for small print and fine objects. Holding reading material farther away. Symptoms worsen in the evening or in dim light. Asthenopic symptoms: Eye strain and discomfort after near work due to ciliary muscle fatigue. Intermittent diplopia at near: Related to the interrelationship between accommodation and convergence. Signs: Detected through testing for presbyopia. Testing should be conducted both monocularly and binocularly..

[Audio] 2.Paralysis of Accommodation (Cycloplegia) Paralysis of accommodation, also known as cycloplegia, refers to complete absence of accommodation. Causes: Drug-Induced Cycloplegia: Caused by atropine, homatropine, or other parasympatholytic drugs. Internal Ophthalmoplegia: Paralysis of ciliary muscle and sphincter pupillae. Causes: neuritis (diphtheria, syphilis, diabetes), chronic alcoholism, cerebral/meningeal diseases, mild head injury. Typically, bilateral. Complete Third Nerve Paralysis: Due to intracranial or orbital lesions (traumatic, inflammatory, vascular, demyelination, neoplastic)..

[Audio] Clinical Features 1.Blurring of Near Vision: Main complaint in emmetropic/hypermetropic patients. Less severe in myopic patients. 2.Photophobia (Glare): Accompanied by mydriasis (pupil dilation). 3.Micropsia: Objects appear smaller due to increased accommodative effort. 4.Abnormal Near Point: Receding near point and decreased accommodation range. 5.Third Nerve Palsy Signs: Additional signs if due to third nerve paralysis..

[Audio] 3.Pathological Insufficiency of Accommodation Accommodative power significantly and persistently below normal physiological limits for the patient's age. Should be distinguished from presbyopia, which is age-related and physiological. Causes: Premature sclerosis of the lens: Essentially premature presbyopia; stable condition. Weakness of ciliary muscle due to systemic causes: Debilitating illnesses, anemia, toxemia, malnutrition. Diabetes mellitus, pregnancy, mental stress. Whooping cough, measles, nasal obstruction, hypopituitarism. Weakness of ciliary muscle due to local causes: Primary open-angle glaucoma. Mild cyclitis (e.g., during the onset of sympathetic ophthalmia)..

[Audio] Clinical Features: Uncommon before age 15 and after 45 years. Symptoms may be intermittent or constant, and transient or persistent. Symptoms: Similar to presbyopia, but with more prominent asthenopic symptoms. Headache, fatigue, and eye irritability during near work. Blurred near vision, making near work difficult or impossible. Intermittent diplopia: Associated with disturbances of convergence. Accommodative failure often linked with convergence insufficiency (seen in 66% of cases). Sometimes excessive convergence occurs when attempting to accommodate..

[Audio] Ill-Sustained Accommodation Condition where accommodation range is normal but cannot be sustained, leading to accommodation fatigue and receding near point of accommodation (NPA) during close work. Etiology: Early stage of true accommodation insufficiency. Similar causes to accommodation insufficiency. Common conditions: Convalescence from illness. General tiredness. Relaxation in bed. Clinical Features: Symptoms: Fatigue during near tasks. Receding near point. Blurred near vision during sustained close work..

[Audio] ACCOMMODATION INERTIA It is a condition in which there is difficulty in adjusting the accommodation according to the distance of the object of regard so as to gain clear vision. It is a comparatively rare condition Clinical Features The patient typically complains that it takes some time and involves some definite effort for him or her to focus a near object after looking at the distance. Usually this condition does not assume any serious preposition, but occasionally may give rise to some trouble and annoyance..

[Audio] Excessive Accommodation Exerting more than the normal required accommodation for near work. Voluntary and intermittent; differs from spasm of accommodation, which is continuous. Causes: Young Hypermetropes: Use excessive accommodation for clear vision as a physiological adaptation. 2.Young Myopes: Engage in excessive near work, leading to increased accommodation and convergence. 3.Astigmatic Error: May occasionally lead to excessive accommodation. 4.Early Presbyopes: Compensate with excessive accommodation for near tasks. 5.Improper Spectacles: Ill-fitting spectacles can cause excessive accommodation..

[Audio] Clinical Features: Blurred Vision: Induced pseudo myopia causing varying degrees of blurred vision. Accommodative Asthenopia: Symptoms include headaches, fatigue, and discomfort in the eyes. Altered Far and Near Points: Both points are brought closer to the eye. Near Vision Difficulty: Blurring of text during prolonged reading, which clears after a rest. Macropsia: Objects appear larger than they are. Miosis: Constriction of the pupils..

[Audio] Spasm of Accommodation Continuous exertion of abnormally excessive accommodation, beyond voluntary control. Also known as cyclotonia. Causes: Drug-Induced: Strong miotics (e.g., echothiophate, di-isopropyl fluorophosphate). Spontaneous in Children: Compensating for refractive anomalies (e.g., uncorrected hypermetropia, astigmatic error, myopia). Occurs with excessive near work, poor illumination, bad reading position, lowered vitality, neurosis, mental stress, or anxiety. Iridocyclitis: Associated with ciliary spasm. Spasm of Near Reflex: Excessive accommodation, convergence, and miosis in tense or disturbed individuals. Brainstem Lesions: Irritative phase (e.g., tabetic crisis, epidemic encephalitis, meningitis). Toxic Reactions: E.g., sulphonamides, arsenic, smoking..

[Audio] ANOMALIES Of CONVERGENCE Convergence insufficiency Convergence insufficiency associated with accommodative insufficiency Convergence paralysis Convergence spasm.

[Audio] CONVERGENCE INSUFFICIENCY Convergence insufficiency is the inability to obtain and or maintain adequate binocular convergence for any length of time without undue effort. It is the most common cause of ocular asthenopic symptoms. Aetiology: Primary or Idiopathic: • Unknown cause; associated with wide PD and delayed functional development. • Precipitated by general debility, psychological instability, overwork, and worry. 2.Refractive Errors: High Hypermetropia: Decreases accommodative convergence. Myopia: Reduced need for accommodation and associated convergence. Overcorrection with Plus Lenses: Reduces accommodative convergence. 3.Presbyopia: Decreased near point use; may worsen with presbyopic correction. 4.Muscular Imbalances: E.g., exophoria, intermittent exotropia, vertical muscle imbalances. 5.Surgical Outcomes: Recession of medial recti or resection of lateral recti muscles..

[Audio] Clinical Features: Convergence insufficiency often becomes a clinical issue in children with increased schoolwork, as well as in individuals who engage in prolonged reading, desk work, or precision tasks.Asthenopic symptoms may be grouped as follows: 1. Symptoms of Muscular Fatigue Eye strain and a sensation of tension in and around the globes is a common complaint of such patients. Headache and eye ache after prolonged use of eyes especially for near work, which are relieved when the eyes are closed for a while. Difficulty in changing the focus from distant to near objects. Itching, burning and soreness of eyes and even hyperemia of the nasal half of the conjunctiva may occur after prolonged close work 2. Symptoms due to failure to maintain binocular vision. Blurred near vision and crowding of words while reading. Intermittent crossed diplopia for near vision under conditions of fatigue is not uncommon Characteristically, one eye Will be closed or covered while reading to obtain relief from VF..

[Audio] Differential Diagnosis: Convergence Insufficiency vs. Convergence Paralysis: Convergence Paralysis: Inability to overcome prism; pupillary constriction without convergence. Convergence Insufficiency: Demonstrates some convergence amplitude; pupillary changes with convergence effort. Convergence Insufficiency vs. Accommodative Effort Syndrome: Convergence Insufficiency: Often associated with exophoria. Accommodative Effort Syndrome: Usually esophoria; improved by –2 D test, worsened by plus lenses..

[Audio] Convergence Insufficiency Associated with Accommodation Insufficiency Convergence insufficiency may sometimes be secondary to accommodation insufficiency. Therefore, it is essential to rule out accommodation insufficiency before treating functional convergence insufficiency. Aetiology Secondary convergence insufficiency linked to primary accommodation insufficiency can occur in conditions such as: Tertiary Adie syndrome Sequelae from head trauma (especially posterior occipital or whiplash injuries) Subclinical viral encephalopathies Infectious mononucleosis Diphtheria Conversion reaction.

[Audio] Clinical Features Symptoms are similar to those of functional convergence insufficiency. Reduced near point of convergence (NPC). Markedly decreased near point of accommodation (NPA). Accommodation-to-convergence (A-C) ratio may be low or absent..

[Audio] Convergence Paralysis Convergence paralysis refers to a total lack of ability to overcome any amount of BO prisms. It is an uncommon entity and should not be confused with functional convergence insufficiency, which is very common. Aetiology Convergence paralysis is usually secondary to organic brain diseases affecting the corpora quadrigemina or the nucleus of the third cranial nerve. Associated organic brain lesions include: Head injury Encephalitis Disseminated sclerosis Tabes dorsalis Narcolepsy Tumors.

[Audio] Clinical Features Absence of Convergence: Complete inability to converge with an acute onset of convergence failure. Strabismus and Diplopia: Esotropia and crossed diplopia occur on attempted near vision. Normal Adduction: Eye adduction remains normal. Accommodation: Usually normal, but may be reduced or absent in some cases. Differential Diagnosis Convergence Paralysis vs. Functional Convergence Insufficiency In convergence paralysis, diplopia occurs immediately with BO prism use, whereas in functional convergence insufficiency, several diopters of convergence amplitude can be demonstrated before diplopia occurs..

[Audio] Convergence Spasm Convergence spasm is characterized by intermittent episodes of maximal convergence, often associated with spasm of accommodation. Aetiology Functional Causes: Most cases are functional in origin, commonly seen in patients with hysteria or neurosis. 2. Organic Causes: Rarely, it may be secondary to underlying organic lesions such as: Head trauma Encephalitis Tabes dorsalis Pituitary adenomas Posterior fossa neurofibromas Arnold-Chiari malformation.

[Audio] Clinical Features 1.Extreme Convergence: Eyes may be positioned in extreme convergence, resembling bilateral abducens palsy. 2.Homonymous Diplopia: Intermittent diplopia may occur. 3.Blurred Vision: Blurring of near vision due to associated spasm of accommodation, leading to difficulty in reading. 4.Miosis: Pupils typically become miotic as part of the near reflex. 5.Induced Myopia: Myopia up to 2 D may be induced by the spasm of accommodation, confirmed by retinoscopy. This can lead to reduced distance visual acuity during an attack..

[Audio] References Bowling B. Kanski’s Clinical Ophthalmology: A Systematic Approach. 8th ed. Sydney: Elsevier; 2016. Jogi R. Basic Ophthalmology. 4th ed. New Delhi: Jaypee Brothers Medical Publishers; 2016 Khurana, A. K. (2015). Theory and Practice of Optics and Refraction (5th ed.)..