Eye: examination – dark – mydriasis

• The addition of a mydriatic to the eye, after dilation of the pupil, allows the lens, vitreous and fundus to be examined in greater detail.

Uses

• As part of full examination of eye   Eye: examination - lighted  .

Advantages

• Allows complete examination of the structures posterior to the iris especially the lens and fundus.

Disadvantages

• Takes time to become effective.
• If atropine   Atropine sulfate  is used, prolonged mydriasis may occur for up to 3-4 weeks in some horses.

• Only use after conjunctival/corneal culture swabs   Cornea / conjunctiva: swab  , a Schirmer tear test   Lacrimal gland: schirmer tear test  and the neuro-ophthalmologic examination   Neurology: examination - adult  .
• It may be difficult to place drops in the eyes of some horses.

Alternative techniques

• Examination in a dark environment may allow adequate viewing of the posterior vitreous and fundus without mydriasis by both direct   Eye: examination - direct ophthalmoscopy - close  and indirect ophthalmoscopy   Eye: examination - indirect ophthalmoscopy  .
• For complete examination of the lens mydriasis is essential.

Time required

Preparation

• Installation of mydriatic: 5 min.
• For full action if topical 1% tropicamide is used: 15-20 min.

Procedure

• Examination of the eye: 5-10 min per eye.

Decision taking

Criteria for choosing test

• Any examination of the eye where full viewing of the posterior segment, especially the lens is required.

Risk assessment