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Forms of Nonsurgical Strabismus Management

Definitions Orthoptics: a wide range of techniques used to expand fusional vergence amplitudes and permit improved single binocular vision. Convergence insufficiency: a deficiency in convergence of the eyes to focus on a near target, causing symptoms such as difficulty reading. Key Feature Numerous nonsurgical techniques are available to treat strabismus and should be considered before strabismus surgery is performed. Orthoptics The treatment of strabismus by means…

Amblyopia

Definition Amblyopia is diminished vision that results from discordant visual experience during the first years of life when the visual pathways are within the early stages of maturation. Key Features Reduced visual acuity accompanied by an amblyogenic factor, most commonly strabismus or anisometropia. Suppression of the amblyopic eye. Reduced or nil stereoacuity. Associated Features Sensory: reduced contrast sensitivity, altered perception of alignment (vernier acuity), deficits in…

Other Vertical Strabismus Forms

Definition Vertical strabismus not paretic in origin. Key Features Incomitance. Supranuclear or mechanical causation. Introduction The various findings in nonparetic vertical strabismus can be grouped into several clinical entities. All share incomitance as a feature. The causes are multiple and include supranuclear, strabismic, mechanical, restrictive, and muscle fibrosis. Dissociated Vertical Divergence Introduction Dissociated vertical divergence (or dissociated vertical deviation [DVD]) is characterized by a spontaneous upward…

Paralytic Strabismus

Definition Strabismus resulting from partial or complete paralysis of the third, fourth, or sixth cranial nerve. Key Features Incomitance—magnitude of deviation is gaze dependent. Secondary deviation—magnitude of deviation increases when paretic or restricted eye is fixating on a target. Associated Features Third nerve palsy—ipsilateral exotropia, hypotropia, ptosis, and pupillary findings. Fourth nerve palsy—ipsilateral hypertropia with head tilt to the opposite side. Sixth nerve palsy—ipsilateral esotropia with…

Torsional Strabismus

Definition Strabismus related to ocular torsion. Key Features A- and V-pattern deviations. Oblique muscle overactions and underactions. Torsion of the globe. Introduction Definitions of Inferior Oblique Overaction, Superior Oblique Overaction, A Pattern, and V Pattern “Oblique muscle overaction” and A- or V-pattern strabismus are defined based on clinical exam findings. Oblique overaction and pattern strabismus usually are intimately related in well-defined ways. It helps to clarify…

Exotropia

Definition Divergent misalignment (outward deviation) of the visual axes of the eyes, which may manifest constantly or intermittently. It may be acquired or congenital. Most often its etiology is unknown (primary forms of exotropia), but it may be secondary to underlying neurological pathology, muscle restriction, or poor vision. Key Feature Outward deviation of one eye (may be alternating). Associated Features History of closing one eye in…

Esotropia

Infantile Esotropia Definition Inward deviation of the visual axes, with an onset before 6 months of age. Infantile Esotropia Key Features Esotropia greater than 30Δ present before 6 months. Cross-fixation. Little or no binocular vision. Normal refractive error for age. Initially, similar deviation at distance and near fixation. Infantile Esotropia Associated Features (Often Appear After the First Year of Life) Inferior oblique overaction. Dissociated vertical deviation.…

Sensory Adaptations in Strabismus

Definition Suppression: Cortical synaptic inhibition preventing conscious appreciation of diplopia and visual confusion in patients with strabismus. Anomalous correspondence: Cortical adaptation to early-onset, long-standing, stable-angle strabismus that permits crude binocular vision. Monofixation syndrome: A form of anomalous binocular vision featuring peripheral fusion and reduced stereopsis in patients incapable of bifoveal fusion. Key Features Suppression is regional, determined by the direction and angle of strabismus, and may…

Sensory Status in Strabismus

Definitions Sensory fusion: cortical integration of similar images into a unified percept. Horopter: the locus in space representing the intersection of all object locations that project images onto corresponding retinal points. Panum's fusional area: area in space surrounding the horopter in which objects are perceived as single, although their images fall on noncorresponding retinal points. Motor fusion: vergence eye movements stimulated by subconscious detection of retinal…

Examination of Ocular Alignment and Eye Movements

Definitions Orthophoria: Exact ocular balance. In this state, perfect equilibrium occurs in the oculomotor apparatus, and the visual axes of each eye intersect at the object of regard. Phoria (Heterophoria): A latent (hidden/controlled) tendency of visual axis deviation manifesting only when the fusion is disrupted. Tropia (Heterotropia): A manifest (obvious/seen all the time) visual axis deviation (also known as strabismus or squint ). This condition can…

Evaluating Vision in Preverbal and Preliterate Infants and Children

Definition Visual acuity in preverbal infants is defined as a motor or sensory response to a threshold stimulus of known size at a known testing distance. Visual acuity in preliterate but verbal children is described as the smallest target of known size at a known testing distance correctly identified by a child. Key Features Vision screening is important to identify treatable causes of vision loss. In…

Anatomy and Physiology of the Extraocular Muscles and Surrounding Tissues

Definition Muscles and associated tissues that provide eye movements and allow for binocular vision. Key Features Unique muscle type with specialized structure, metabolism, and innervation. Connective tissue gimbal supporting the eyeball and regulating its rotational properties. Embryology The development of extraocular muscles, which are of mesodermal origin, begins at 3–4 weeks’ gestation. Early in gestation, neural crest cells divide and encircle the mesodermal cells destined to…

Evidence-Based Medicine in Glaucoma

Definition Evidence-based medicine is the use of the highest-quality medical data currently available to assist in clinical decision making. Key Features The Oxford Centre for Evidence-Based Medicine 2011 Levels of Evidence propose the hierarchy for levels of evidence shown in Fig. 10.32.1 . Introduction The practice of medicine will always be a combination of science and art. We learn the artistic aspects from our teachers and…

Genes Associated With Human Glaucoma

Definition The genetic component underlying the pathogenesis of many of the heterogeneous diseases referred to as glaucoma . Key Features Congenital or juvenile onset. Common forms of glaucoma with complex inheritance. Introduction For many years a family history of glaucoma has been recognized as an important disease risk factor. Some forms of glaucoma are inherited as mendelian dominant or recessive traits, including juvenile open-angle glaucoma, congenital…

Complications of Glaucoma Surgery and Their Management

Definition Untoward events occurring with glaucoma surgery intraoperatively or postoperatively that can limit the success of the surgery. Key Features Can occur in the intraoperative, early postoperative, or late postoperative period. May or may not be technique dependent. May cause pain, decreased vision, double vision, irritation, or loss of vision. Associated Features Conjunctival buttonhole. Intraocular hemorrhage. Hypotony. Shallow anterior chamber. Infection. Cataract. Diplopia. Introduction The primary…

Drainage Implants

Definition Glaucoma drainage implants are surgically placed to lower intraocular pressure. They may be used at any stage in the treatment of glaucoma. Key Feature Glaucoma drainage implants bypass the natural aqueous outflow systems and typically shunt aqueous humor via a silicone tube from the anterior chamber to a plate in the sub-Tenon's or subconjunctival space, generally >8 mm posterior to the limbus. Associated Features Glaucoma…

Antifibrotic Agents in Glaucoma Surgery

Definition Medical and other adjunctive agents and associated surgical techniques used intraoperatively and/or preoperatively and postoperatively to modulate the wound healing associated with glaucoma surgery in an effort to increase its success. Key Features Mitomycin C. 5-Fluorouracil. Topical intraoperative use. Subconjunctival injected preoperative and postoperative use. Associated Features Most commonly indicated for patients with elevated risk of failure, including previous surgery, neovascular glaucoma, and black African…

Trabeculectomy

Definition A surgical procedure featuring a partial-thickness scleral flap that creates a fistula between the anterior chamber and the subconjunctival space for filtration of aqueous fluid and the creation of a conjunctival bleb in an effort to lower intraocular pressure. Key Features Bleb formation occurs. When successful, decreases intraocular pressure significantly from preoperative levels. Wound healing influences success. Meticulous intraoperative technique is required. Intense postoperative observation…

Microinvasive Glaucoma Surgeries

Definition Minimally invasive glaucoma surgery and microincisional glaucoma surgery offer the theoretical advantages of lowering intraocular pressure with incisional surgery with fewer risks compared with conventional operations. Approaches include the use of microdevices for removal or bypass of abnormally high-resistance tissues. Key Features Lower surgical and postoperative risk versus conventional glaucoma surgery. Typically less IOP reduction versus conventional glaucoma surgery. Minimally invasive and microincisional glaucoma surgeries:…

Goniotomy and Trabeculotomy

Definition Anterior segment surgical techniques for the treatment of childhood glaucoma. Key Features Angle surgery uses an ab interno or ab externo surgical approach to create a direct communication between the anterior chamber and Schlemm’s canal by incising the trabecular meshwork to lower intraocular pressure. Trabeculotomy is performed when the cornea is too cloudy to allow visualization of the angle or when the operating surgeon is…