[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Ophthalmology](https://durgical.com/en/ophthalmology/) › [The eye exam](https://durgical.com/en/ophthalmology/areas/exam/) › Dilated fundus examination: when and how # Dilated fundus examination: when and how - Examination Through an undilated pupil the ophthalmoscope shows little more than the disc. Dilating drops open the view to the macula and periphery, with few risks. Updated Nov 5, 2026 **See it in 3D:** [Optic disc](https://durgical.com/en/anatomy/optic-disc/) · [Retina](https://durgical.com/en/anatomy/retina/) · [Macula](https://durgical.com/en/anatomy/macula/) ## Key points - Dilate to see the macula and beyond the disc. - Check acuity and pupils first. - Angle closure after dilation is rare. - Do not dilate unrecorded in neurological observation. ## What it is The fundus is the back of the eye: optic disc, retinal vessels, macula and peripheral retina. A direct ophthalmoscope through a small pupil shows a narrow area around the disc. Dilating the pupil with short-acting drops widens the view; ophthalmologists add binocular indirect ophthalmoscopy or slit lamp lenses to see the periphery, where retinal tears hide. Diabetic retinopathy screening needs a dilated exam or retinal photographs. ## Normal values and scales - Tropicamide acts quickly and lasts a few hours; phenylephrine adds dilation through the sympathetic route. - Dilation rarely triggers acute angle closure; a shallow anterior chamber is a reason for caution, not an absolute contraindication. - In neurological observation (head injury, coma) pupils are not dilated without agreement, and if they are it must be recorded clearly. - Normal cup-to-disc ratio is usually under about 0.5, and similar in both eyes. ## How it is done - Measure visual acuity and check the pupils before dilating, and look at the anterior chamber depth with a penlight. - Instil a short-acting dilating drop (tropicamide, often with phenylephrine) in each eye. - Wait about 15 to 30 minutes for full dilation. - With the direct ophthalmoscope, find the red reflex, follow a vessel to the disc, then look at each quadrant and finally at the macula. - Describe the disc (colour, margins, cup), the vessels, haemorrhages or exudates, and the macula. - Warn the patient about blurred near vision and glare for several hours, and advise not to drive until it settles. ## How to interpret it - Peripheral retinal tears cannot be excluded with a direct ophthalmoscope even through a dilated pupil. - The disc and vessels show raised intracranial pressure, hypertension, diabetes and glaucoma. - If dilation causes a painful red eye with halos, it is acute angle closure: better found in the clinic than later. ## Next step / Initial management - Abnormal disc (swelling, pallor, large or asymmetric cup) or retina: refer according to the finding (urgent for swelling or haemorrhages with symptoms). - Diabetes: dilated exam or retinal photography at diagnosis of type 2 and then periodically. - New floaters, flashes or a shadow: dilated peripheral exam by ophthalmology. - Painful red eye after dilation: emergency angle closure pathway. ## Test yourself Think of the answer, then tap the question to see it. ## Why is the pupil dilated for a fundus exam? Through a small pupil only a narrow area around the disc is seen; dilation shows the macula and more of the retina. ## What should be done before dilating the pupils? Measure visual acuity, check the pupil reactions and estimate the anterior chamber depth. ## When should dilation be avoided or clearly documented? In patients under neurological observation, where pupil changes are monitored. [Add to my cards (3)](https://durgical.app/estudiar/?add=/en/ophthalmology/dilated-fundus-examination-when-and-how/) ## Elsewhere in DurgiPedia - [Fundoscopy: the optic disc, papilledema and retinopathy](https://durgical.com/en/clinical-exam/fundoscopy-the-optic-disc-papilledema-and-retinopathy/) ## Connections ## See it in 3D 3 The structures of Durgical's 3D anatomy where it is found. - [Optic disc](https://durgical.com/en/anatomy/optic-disc/) - [Retina](https://durgical.com/en/anatomy/retina/) - [Macula](https://durgical.com/en/anatomy/macula/) ## Related 5 - [The swollen optic disc: papilloedema or not](https://durgical.com/en/ophthalmology/the-swollen-optic-disc-papilloedema-or-not/) - [The optic disc: cup, rim and colour](https://durgical.com/en/ophthalmology/the-optic-disc-cup-rim-and-colour/) - [Diabetes and the eye: screening and grading](https://durgical.com/en/ophthalmology/diabetes-and-the-eye-screening-and-grading/) - [Floaters and flashes](https://durgical.com/en/ophthalmology/floaters-and-flashes/) - [Acute angle closure: what to do before the ophthalmologist](https://durgical.com/en/ophthalmology/acute-angle-closure-what-to-do-before-the-ophthalmologist/) ## Related conditions 4 - [Diabetic retinopathy](https://durgical.com/en/conditions/diabetic-retinopathy/) - [Hypertensive retinopathy](https://durgical.com/en/conditions/hypertensive-retinopathy/) - [Open-angle glaucoma](https://durgical.com/en/conditions/open-angle-glaucoma/) - [Idiopathic intracranial hypertension](https://durgical.com/en/conditions/idiopathic-intracranial-hypertension/) ## In Pharmacology 3 - [Tropicamide](https://durgical.com/en/pharmacology/tropicamide/) - [Phenylephrine](https://durgical.com/en/pharmacology/phenylephrine/) - [Mydriatics and cycloplegics](https://durgical.com/en/pharmacology/classes/mydriatics-and-cycloplegics/) [← All of ophthalmology](https://durgical.com/en/ophthalmology/) Educational content; not a clinical guideline and no substitute for assessment by a health professional. For sudden visual loss, severe eye pain, a chemical burn or an eye injury, go to an emergency department at once. Sources: [Auxiliary Lenses for Slit-Lamp Examination of the Retina](https://www.ncbi.nlm.nih.gov/books/NBK587346/) (StatPearls Publishing (NCBI Bookshelf), 2023); [Acute Angle-Closure Glaucoma](https://www.ncbi.nlm.nih.gov/books/NBK430857/) (StatPearls Publishing (NCBI Bookshelf), 2026); [Diabetic Retinopathy](https://www.ncbi.nlm.nih.gov/books/NBK560805/) (StatPearls Publishing (NCBI Bookshelf), 2023). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/ophthalmology/dilated-fundus-examination-when-and-how/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/ophthalmology/dilated-fundus-examination-when-and-how/