Uveitis is usually associated with trauma, inflammation, and infectious processes. Anterior uveitis is the most common type of uveitis. Symptoms include eye redness, eye pain, photophobia, lacrimation and decreased vision. Signs include conjunctival ciliary congestion, keratic precipitates, anterior chamber flare and inflammatory cells, iris posterior synechia, iris depigmentation, iris nodule, hypopyema as examples. Systemic diseases associated with anterior uveitis include HLA-B27-related diseases, juvenile idiopathic arthritis, inflammatory bowel disease, sarcoidosis, Behcet's disease (BD), or tubulointerstitial nephritis (TINU).
There are three other types of uveitis: intermediate uveitis, posterior uveitis and panuveitis. Systemic diseases associated with intermediate uveitis include multiple sclerosis, sarcoidosis and tubulointerstitial nephritis (TINU). Systemic diseases associated with posterior uveitis include Vogt-Koyanagi-Harada syndrome, leukemia, systemic lupus erythematosus, Behcet's disease (BD), and multiple sclerosis. BD is a systemic vasculitis that can also cause panuveitis.
Regardless of type, if there is infectious uveitis, the source of the uveitis can include virus (herpes simplex virus, varicella-zoster virus, cytomegalovirus), bacteria (endophthalmitis, syphilis, tuberculosis, etc.), or parasites/helminths (toxoplasmosis, lyme disease, Toxocara Sp, Bartonella, or other atypical infections).
Uveitis is usually a complication of systemic disease in the eye. In a study done from 2006 to 2007, the incidence of uveitis was 24.9 cases per 100,000 persons. Prevalence rates for 2006 and 2007 came in at 57.5 and 58 respectively per 100,000 persons. There was no difference in the incidence rate between men and women, but women had a higher prevalence. Anterior uveitis is the most prevalent form, accounting for approximately 50% of uveitis cases (See “References 6”).
Myopia is a refractive error in the eye which occurs when rays of light entering the eye parallel to the optic axis are brought to a focus in front of the retina when ocular accommodation is relaxed. The anatomic cause is typically because the eyeball is too long from front to back, but it can also be caused by an overly curved cornea and/or a lens with increased optical power.
Myopia may be due to multiple factors and can be associated with:
- Age: The main factor leading to faster progression of myopia in children is a young age of onset.
- Race: Studies have shown a higher prevalence of myopia in Asian children than in non-Hispanic white children between 6 months and 6 years of age.
- Family history: Myopia is heritable, and children with myopic parents have a threefold or greater risk compared to nonmyopic parents.
- Eye development: There’s a risk of myopia when children's hyperopia reserve is below normal levels.
- Visual environment: The risk of myopia development and progression is significantly associated with reading at very close distances (<20 cm) and for continuous periods of time (>45 minutes) rather than being associated with total time spent on all near activities. Educational activities: The longer the formal education period, the higher the prevalence of myopia.
- Binocular vision: Children and adolescents with binocular insufficiency have an increased incidence of myopia; inadequate correction of myopia also contributes to the progression of myopia.
Myopia is an important condition in childhood and in adults. The prevalence of myopia (defined as 0.75 D or more) is estimated to be 9% in children in the United States aged 5 to 17 years. In children aged 6 to 72 months, the prevalence of myopia in non-Hispanic white children was 1.2% and for Asian children it was 4.0%. For black American children it was 6.6% and for Hispanic children it was 3.7%. A meta-analysis of population-based studies found a 25% prevalence of myopia (defined as 1.00 D or more) in persons over age 40 in the United States; a study based on a sample representative of the U.S. population found a prevalence of 31% in those aged 40 and older and of 36% in those aged 20 and older. A number of population-based studies have shown that the prevalence of myopia is lower in older persons than in younger persons. The prevalence is about 35% to 40% among persons in their 20s to 40s and decreases to about 15% to 20% among those in their 60s, 70s, and 80s (See “References 8”).
Dry eye is described in the literature as having a tear film imbalance with a patient presentation of multiple ocular symptoms. Pathogenesis of dry eye is complicated, including instability and high osmotic pressure of tear film, inflammation and injury of ocular surface, and neurosensory abnormalities. Etiology is broad and vast and may be related to general disorders such as age, sex, race, meibomian gland dysfunction, contact lens wearing, Sjogren's syndrome, environmental exposure, using of electronic displays, diabetes and other systemic disorders, genetic factors as examples of other factors which lead to the disease.
According to the study published on AJO June 2019 by Reza Dana, Dry Eye Disease (DED) prevalence was 5.28% overall, 7.78% among female beneficiaries, 2.96% among male beneficiaries and increased with age from 0.20% for ages 2-17 years, to 11.66% for individuals aged 50+ years. Annual prevalence increased from 0.8% to 3.0% overall, from 1.4% to 4.5% in female beneficiaries, and from 0.3% to 1.6% in male beneficiaries (See “References 3”).
Glaucoma has many causes with typical findings of pathological measured intraocular pressure elevation, characteristic visual field defects and optic atrophy as the common lesions (typically the atrophy is irreversible), and ultimately leading to vision loss. Glaucoma is the leading cause of blindness worldwide, second only to cataracts as an eye disease. Risk factors for open-angle glaucoma mainly include elevated intraocular pressure, increasing age, positive family history, ethnic background, myopia, thin cornea, hypertension, and diabetes. Patients with elevated intraocular pressure or other risk factors should be examined regularly for timely detection of glaucoma.
Risk factors for angle-closure glaucoma mainly include ethnic background, increasing age, female, positive family history, and hyperopia. Patients with these risk factors should be examined regularly to detect angle-closure glaucoma in a timely manner.
WHO speculated that there are approximately 66.8 million people with primary glaucoma worldwide (in 2000), of whom approximately 10% are blind. The prevalence of primary glaucoma is 0.52% in China, 2.07% in people over 50 years old, and the blindness rate of glaucoma is 9.04% ~ 10% (reported in 1996) (See “References 5”).
Age-related macular degeneration (AMD) is a disorder of the macula, located in the back of the eye, characterized by one or more of the following:
- Presence of at least intermediate-size drusen (63 µm or larger in diameter)
- Retinal pigment epithelial (RPE) abnormalities such as hypopigmentation or hyperpigmentation
- Reticular drusen
- the RPE (i.e., atrophic/dry macular degeneration), choroidal the RPE (i.e., atrophic/dry macular degeneration), choroidal neovascularization (CNV, i.e. exudative/wet macular degeneration), polypoidal choroidal vasculopathy (PCV), or retinal angiomatous hyperplasia.
Risk factors for AMD as examples include age, ethnicity, smoking, family history, hypertension and cardiovascular disease, BMI > 30 or higher, and low antioxidant levels in the body.
AMD is responsible for an estimated 46% of cases of severe visual loss (visual acuity 20/200 or worse) in persons over 40 years of age in the United States. Although an estimated 80% of AMD patients have non-neovascular or atrophic AMD, the neovascular form is responsible for nearly 90% of the severe visual acuity loss (20/200 or worse) from AMD.
A recent meta-analysis and systematic review reported a higher prevalence of AMD in Europeans than in Asians or Africans, with no difference in prevalence between Asians and Africans. The global number of people with AMD was projected to be 196 million in 2020, increasing to 288 million in 2040 (See “References 7”).
Conjunctivitis caused by microbial infection is called infectious conjunctivitis. The causative organisms are typically bacteria, viruses or chlamydia. Common symptoms of conjunctivitis include foreign body sensation, burning sensation, itching, photophobia, lacrimation and ocular pain when inflammation affects the cornea. Typical signs of infective conjunctivitis include conjunctival congestion, conjunctival discharge, conjunctival papillary hyperplasia, conjunctival edema as examples., The estimated number of cases of bacterial conjunctivitis in the United States in 2005 was 4 million (See “References 2”).
Allergic conjunctivitis is caused by conjunctiva hypersensitivity to allergen stimulation, mainly type I and type IV hypersensitivity. The typical symptoms of allergic conjunctivitis include itchy eyes, foreign body sensation and increased secretion in conjunctival sac. Most patients with allergic conjunctivitis complain of itching and a few complained of foreign body sensation; the conjunctival sac secretions of allergic conjunctivitis are predominantly white mucinous secretions. A child with allergic conjunctivitis may present with rubbing or with frequent blinking. Conjunctival hyperemia (erythema) is the most common sign of allergic conjunctivitis with varying degrees of conjunctival edema. Conjunctival papilla is one of the characteristics of allergic conjunctivitis.
There continues to be a lack of epidemiological data characterizing allergic conjunctivitis in China. Outside of China, in the United States, a report documented 40% of Americans suffer from allergic conjunctivitis, yet only 10% seek treatment. In Asia it is estimated that 15% to 20% of Japanese have a history of allergic conjunctivitis. In China perennial-seasonal allergic conjunctivitis account for 74% of all reported allergic conjunctivitis; contrast in the United States where seasonal allergic conjunctivitis accounts for more than 90% of allergy conjunctivitis (See “References 2”).
Anatomically, any opacification of the lens is called cataract. Cataracts are common causes of blindness and visual disability. Age-related cataracts are typically characterized by having one or more of these issues: decreased visual acuity, decreased contrast sensitivity, refractive changes, monocular diplopia or polyopia, glare, color perception changes, or visual field defects. Other problems may occur with less frequency.
Lens opacities expand slowly for several months or even several years, and patients with early cataracts may present with a variety of symptoms, such as blurred vision (main symptom), ghosting, decreased vision, visual distortion, glare, monocular diplopia, color perception changes.
With continued opacification of the lens, a mature cataract develops at a later stage, which is characterized by the complete opacification of the lens cortex into white. The color and size of the lens nucleus often can’t be resolved due to the occlusion of the cortex. Visual acuity is decreased to hand movement or light perception, and the fundus cannot be seen.
In the United States, cataracts account for approximately 50% of visual impairment in adults over the age of 40. In 2010, half of white Americans had cataracts by 75 years of age, and 70% of white Americans, 61% of Hispanic Americans, and 53% of black Americans had cataracts by 80 years of age (See “References 4”).
Blepharitis is clinically divided into:
- Staphylococcal Blepharitis Staphylococcal blepharitis mainly affect the anterior eyelid and can be referred to as anterior blepharitis.
- Seborrheic Blepharitis Seborrheic blepharitis also mainly affect the anterior eyelid and can also be referred to as anterior blepharitis.
- Meibomian Gland Dysfunction (MGD) Meibomian gland dysfunction (MGD) is a chronic diffuse meibomian gland abnormality that may result in changes in tear film, ocular irritation symptoms, obvious inflammation and ocular surface disease.
Blepharitis often causes ocular surface inflammation, including conjunctivitis, functional tear deficiency, and keratitis. Blepharitis may also exacerbate symptoms of complicating ocular surface disorders, such as allergies and tear deficiencies.
Although blepharitis is one of the most common ocular disorders, epidemiologic information on its incidence or prevalence within defined populations is lacking. One study noted that compared with patients who have other forms of blepharitis, patients who have staphylococcal blepharitis were found to be relatively younger (42 years old) and most were female (80%). A survey of ophthalmologists and optometrists reported that blepharitis was commonly seen in clinical practice in 37% and 47% of their patients, respectively (See “References 1”).