Dilated fundus examination

The most common agents used to dilate the pupil are phenylephrine (2.5% in pediatrics or 10% in adults) and tropicamide (0.5% or 1%). While phenylephrine stimulates receptors that contract the dilator muscle of the pupil, tropicamide blocks stimulation of the pupillary sphincter muscle to allow for relaxation. As the insertion of these drops may cause some stinging or burning, some practitioners choose to first insert a drop of topical anesthetic to numb the eye. Pupil dilation typically begins within 15 minutes and may last for 3–8 hours. Evaluation of the optic disc may include noting the color of the disc, the sharpness of the disc outline and if any swelling is present, and signs of an enlarged or bulging optic cup, the central depression in the optic disc. Evaluation of the retina includes examining the arteries and veins for narrowing or arteriovenous nicking, as well as detecting any lesions, exudates, retinal hemorrhages, microaneurysms, or neovascularization. Dilated fundus exam is the preferred method of diagnosis, as undilated exam may be too limited to visualize lesions or neovascularization that are more peripheral. • Glaucoma: A group of eye diseases that can cause vision loss due to damage to the optic nerve, generally from increased intraocular pressure. Changes on ophthalmologic exam include deepening and enlargement of the optic cup (leading to a high cup/disc ratio), a more vertical oval optic cup shape, pallor of the disc, and an increase in the blood vessels within the optic nerve on the nasal side of the disc. Other disc findings may include notching of the disc, or flame/splinter hemorrhages, which are located in the outer nerve layer. • Age-related macular degeneration: A common cause of central vision loss; early diagnosis via ophthalmologic examination may facilitate slower disease progression. The examiner will evaluate the macula for deposits of cellular debris called drusen, in particular their size, number, and distribution, as well as pigmentary changes, atrophy, and hemorrhage, among other signs. == Screening guidelines ==

Adults The American Academy of Ophthalmology recommends comprehensive eye examinations, including dilated fundus examination, for asymptomatic patients without risk factors for eye disease at varying frequencies based on age: every 5–10 years in adults under 40 years, every 2–4 years in adults aged 40 to 54 years, every 1–3 years in adults aged 55 to 64 years, and every 1 to 2 years in adults aged 65 years and older. In contrast, individuals with diabetes mellitus are at risk of diabetic retinopathy and therefore require more frequent screening. Those with type 1 diabetes should have their first comprehensive eye examination 5 years after diagnosis, followed by yearly exams. Those with type 2 diabetes should have their first comprehensive eye examination at the time of diagnosis, followed by yearly exams. Women with type 1 or type 2 diabetes who are planning a pregnancy should have a comprehensive eye examination prior to conception as well as early in the first trimester; women with gestational diabetes do not require screening for diabetic retinopathy during pregnancy. However, if an infant is premature (gestational age under 32 weeks) or has a low birth weight (less than 1500 g) a dilated fundus examination is indicated due to risk of retinopathy of prematurity. A child will continue to be screened for vision issues, as well as normal eye alignment and movement, at regular intervals during their well child exams; if they fail a vision test or findings are inconclusive, the child can be referred for a more comprehensive eye examination including dilation. Finally, children with certain medical conditions that place them at a higher risk for eye pathology (Down syndrome, juvenile idiopathic arthritis, neurofibromatosis) require comprehensive eye examinations with dilation. Similarly, children with a family history of amblyopia, strabismus, retinoblastoma, congenital cataracts or glaucoma may also require more frequent or comprehensive examinations. == Contraindications ==

A dilated fundus examination is typically contraindicated in situations where mydriatic eye drops are contraindicated. Absolute contraindications include: • Anterior uveitis • Pregnancy • Breastfeeding ==References==