The growth of the eye from infancy to adulthood is a complex, sequential process with the anterior portion of the eye developing earlier than the posterior portion. The newborn infant eyeball measures 16.5 mm in axial length, and is 70% of the adult size. The anterior chamber between the cornea and the iris grows rapidly in the first 2 years, followed by the slower, gradual posterior…
Introduction Since the late 1970s, there has been an explosion of new information about the maturation of the human visual system. A growing appreciation of the role of visual experience in shaping the functional organization of the maturing visual system has driven the research effort to define the normal course of maturation and its susceptibility to early abnormal visual experience. There are several critical periods during…
This chapter combines the traditional anatomical approach to embryology with the rapidly advancing understanding of developmental biological processes involved in eye formation and maturation. Knowledge of the gene networks involved in ocular development provides a foundation for understanding the impact of developmental disorders on visual function. Appreciation of ocular developmental gene networks is also critical for processes of induced pluripotent stem cell (iPSC) differentiation to ocular…
Introduction This chapter first presents a number of key considerations and issues relevant to understanding and applying evidence from epidemiological studies of childhood visual impairment (VI), severe visual impairment (SVI), or blindness ( Box 1.1 and Box 1.2 ) – collectively “VI” for brevity. Thereafter, the impact of childhood VI is considered from different perspectives. This is followed by consideration of childhood VI in the broader…
Eyelid trauma Periocular haematoma A ‘black eye,’ consisting of a haematoma (focal collection of blood) and/or periocular ecchymosis (diffuse bruising) and oedema, is a very common result of blunt injury and is generally innocuous. It is important to exclude serious associated damage to the eyeball or orbital structures, particularly occult orbital roof fracture (subconjunctival haemorrhage without a visible posterior limit may be an indicator), and basal…
Cornea Vortex keratopathy (cornea verticillata) Signs: (a) fine greyish or golden-brown opacities in the inferior corneal epithelium, (b) progressing to a whorl-like pattern that originates from a point below the pupil and swirls outwards, sparing the limbus ( Fig. 20.1 ); usually reversible on cessation of medication. Vision is not impaired, but some patients may experience haloes. Causes: quinolone antimalarials (chloroquine, hydroxychloroquine) and amiodarone. Chlorpromazine Long-term…
Optic nerve Table 19.1 Signs of optic nerve dysfunction Reduced VA Relative afferent pupillary defect Dyschromatopsia: impairment of colour vision, mainly red and green Diminished light brightness sensitivity Diminished contrast sensitivity Visual field defects, varying with the underlying pathology Table 19.2 Visual field defects in optic neuropathies 1 Central scotoma Demyelination Toxic and nutritional Leber hereditary optic neuropathy Compression 2 Enlarged blind spot Papilloedema Congenital anomalies…
Amblyopia Definition: unilateral, or rarely bilateral, subnormal best corrected VA caused by form vision deprivation and/or abnormal binocular interaction, for which there is no identifiable pathology of the eye or visual pathway. Classification Strabismic: resulting from abnormal binocular interaction in which there is continued monocular suppression of the deviating eye. Anisometropic: caused by a difference in refractive error between the eyes. Stimulus deprivation: caused by marked…
Muscae volitantes Muscae volitantes are extremely common minute fly- or worm-like physiological opacities best seen by the patient against a pale background. They are thought to be predominantly composed of embryological remnants in the vitreous gel. You’re Reading a Preview Become a Clinical Tree membership for Full access and enjoy Unlimited articles Become membership If you are a member. Log in here
Definitions Retinal detachment (RD): separation of the neurosensory retina (NSR) from the RPE, with the accumulation of subretinal fluid (SRF). Rhegmatogenous RD: occurs when a full-thickness defect in the NSR permits synchytic (liquefied) vitreous to gain access to the subretinal space. Tractional RD: involves the contraction of vitreoretinal membranes in the absence of a retinal break. Exudative RD: SRF is derived from retinal or choroidal vessels…
Generalized photoreceptor dystrophies Retinitis pigmentosa Genetics: Typical retinitis pigmentosa (RP) is a group of retinal dystrophies initially mainly affecting the rod photoreceptor cells and subsequently cones (rod–cone dystrophy). It can be sporadic or inherited as AD, AR, or X-L; many cases are due to mutation in the rhodopsin gene. X-L has the worst prognosis with severe visual loss by the 4th decade, AR and sporadic cases…
Age-related macular degeneration Introduction Definition: degeneration affecting the macula; characterized by drusen and RPE changes, and sometimes CNV. Classification: non-exudative (‘dry’)—most common, and exudative (‘wet’); the latter is associated with more rapid progression to advanced sight loss. Importance: most common cause of irreversible visual loss in industrialized countries; advanced age-related macular degeneration (AMD) in one eye confers a 50% chance of advanced AMD in the fellow…
Diabetic retinopathy Introduction Prevalence: (a) the overall prevalence of diabetic retinopathy (DR) in diabetic patients is approximately 40%; (b) DR is more common in type 1 than in type 2 diabetes, (c) sight-threatening disease is present in up to 10%, and (d) proliferative disease affects 5–10% of the diabetic population (60% after 30 years in type 1). Risk factors: (a) duration of diabetes (50% after 10…
Benign epibulbar tumours Conjunctival naevus Diagnosis Presentation: in 1st and 2nd decades. Signs: (a) slightly elevated pigmented bulbar lesion of variable size and pigmentation, (b) often juxtalimbal ( Fig. 12.1 ); (c) cystic spaces are common. Signs of potential malignancy: (a) prominent feeder vessels, (b) sudden growth or increase in pigmentation, and (c) development after the 2nd decade, particularly in an unusual site such as palpebral…
Terminology Uveitis: inflammation of the uveal tract. Anterior uveitis: iritis and iridocyclitis (iris and ciliary body). Intermediate uveitis: inflammation of the pars plana, the peripheral retina, and the vitreous. Posterior uveitis: inflammation posterior to the vitreous base. Retinitis: primary retinal focus of inflammation. Choroiditis: primary choroidal focus. Vasculitis: inflammation of veins, arteries, or both. Panuveitis: involvement of the entire uveal tract. Endophthalmitis: involves all intraocular tissues…
Ocular hypertension Diagnosis Normal IOP: mean IOP in the general population is 16 mm Hg; two standard deviations to either side of this gives a ‘normal’ IOP range of 11–21 mm Hg ( Fig. 10.1 ). Definition: 4–7% of individuals older than 40 years have IOPs >21 mm Hg without detectable glaucomatous damage—‘ocular hypertension’ (OHT). Risk factors for conversion of OHT to glaucoma: (a) higher IOP, (b) greater age,…
Acquired cataract Age-related cataract Subcapsular ( Fig. 9.1 ): (a) anterior lies directly under the lens capsule, and (b) posterior lies just in front of the posterior capsule and appears black on retroillumination; the latter often has a more profound effect on vision than a comparable nuclear or cortical cataract, with glare and poor near vision. Nuclear: often associated with myopia due to an increase in…
Episcleritis Simple episcleritis Diagnosis Presentation: acute onset of redness and mild discomfort. Signs: hyperaemia may be sectoral (typically interpalpebral; Fig. 8.1 ) or diffuse. Course: spontaneous improvement occurs within several days, but recurrences may occur. Treatment: not required if mild; otherwise lubricants or a weak steroid four times daily for 1–2 weeks. Nodular episcleritis Diagnosis Presentation: less acute onset than simple episcleritis with redness and discomfort…
Keratoplasty Introduction Classification: (a) partial (anterior or posterior lamellar) or (b) full-thickness (penetrating [PKP]). Indications: (a) optical, (b) tectonic, (c) therapeutic, and (d) cosmetic. Donor tissue: should be removed within 12–24 hr of death and stored under special conditions; contraindications to donation include certain infections (e.g. HIV) and some forms of ocular disease. Penetrating keratoplasty Technique: (a) determination of graft size, (b) trephination of donor tissue, (c)…
Bacterial keratitis Pathogenesis Pathogens: most common are (a) Pseudomonas aeruginosa , (b) S. aureus , and (c) streptococci. Risk factors: (a) contact lens wear, (b) trauma, and (c) ocular surface disease. Diagnosis Presentation: subacute onset of pain, photophobia, blurred vision, and discharge. Signs: (a) epithelial defect with larger infiltrate ( Fig. 6.1 ), (b) stromal oedema, (c) anterior uveitis, often with hypopyon ( Fig. 6.2 ),…