Ophtho2- Lens

surface ectoderm; lens capsule; the lens is not perceived to be as part of self, and exposure to the lens proteins will result in an inflammatory response

capsule, epithelium, cortex, nucleus, zonules

anteriorly, below the lens capsule, there is a lens epithelium that grows continuously throughout life--> lens can't get larger, so it just gets denser--> all animals > 6yo have lenticular sclerosis

• semi-permeable membrane
• anteriorly, the lens is bathed in aqueous humor, from which it receives nutrition and removes waste
• posteriorly, it is in contact with the vitreous

• the lens is AVASCULAR
• it relies on the aqueous humor for the supply of nutrients and removal of waste products
• abnormalities of the aqueous (anterior uveitis) can result in lens abnormalities

• dilate the pupil with tropicamide
• penlight exam: animals with cataracts should have normal PLR (cataracts will never interfere with the afferent arm of the PLR)
• fundic exam:abnormalities of the retina can lead to cataracts or prevent cataract sx in the future
• +/- biomicroscopy: referral only

diabetes mellitus

• abnormalities anterior to the center of rotation move in the same direction as the eye
• abnormalities posterior move in the opposite direction

• all dogs and cats >6 years old have lenticular sclerosis (diagnosed based on signalment!)
• it should not prevent examinations of the fundus
• no txt required

• loss of lens transparency
• Hereditary: not always present at birth
• Traumatic: penetrating injury, blunt injury, inflammation resulting from trauma
• Metabolic: most likely DM
• Toxic: not a huge differential
• Nutritional: Esbilac in orphaned puppies
• Radiation: gamma treatment of malignant neoplasia of the head
• Electric: shock from wires, etc

a localized, non-progressive cataract

a more severe, progressive cataract.

over abundance of glucose in aqueous humor--> glucose metabolism shifts to the sorbitol pathway, where glucose is instead reduced to sorbitol--> sorbitol cannot exit the lens, so it accumulates--> osmotic shift--> water drawn into lens, resulting in swelling and disruption of the fibers--> bilateral, rapid onset cataracts (not necessarily symmetrical)

• eyelids and conj (inflammation, necrosis, alopecia, depigmentation)
• cornea (ulceration)
• lens (equatorial cataracts)
• retina (hemorrhage, uveitis)

• capsular
• cortical (likely to progress b/c very actively growing part of lens)
• nuclear (always congenital, not always hereditary)
• equatorial (most likely to progress b/c most metabolically active part of lens)
• axial

• cortical
• equatorial

equatorial location

• incipient: very small area of the lens affected with a cataract
• immature: larger but still permits examination of the fundus with pupil dilation; some visual disturbance
• mature: involves entire lens, fundus cannot be seen, will result in blindness
• hypermature: describe the state of lens fibers (not amount affected); undergoing liquefication and leaking into aqueous--> lens-induced uveitis

cataract undergoing liquefication--> lens capsule is semi-permeable, so lens protein enters aqueous humor--> lens is not recognized as part of self, so body mounts an inflammatory response--> lens-induced uveitis

• uveitis may require treatment to prevent discomfort and secondary changes, such as glaucoma
• an eye with LIU has an increased risk associated with cataract sx

• SURGERY (phacoemulsification) +/- artificial lens implantation (always recommended if want return to almost normal vision)
• this is a referral procedure and is not to be done in private practice

• hereditary, metabolic
• inflammatory

• subcortical reflex; shine a bright light in the eye and it’s so physically abrasive that the patient has to look away
• abnormal if absent

• vitreous is usually hypoechoic on US
• with VD, vitreous becomes hyperechoic and swirls on US (increased risk factors)

topical intraophthalamic NSAIDs (delay and prevent PIFM, control lens-induced uveitis)

ultrasound and electroretinography

incision--> capsulorhexis--> +/- hydrodissection--> phacoemulsification--> cortical aspiration--> implant artificial lens--> closure

terriers (there's a genetic test- homozygotes WILL be affected b/w age 4-8; consider lens removal before lens luxates in these animals)

• anterior: lens covers part of the iris
• posterior: can see the back of the eye without dilating pupil

trauma, glaucoma, uveitis

• iridodenesis
• phacodenesis
• aphakic cresent
• corneal edema (focal or diffuse depending on anterior or posterior)
• anterior: painful, epiphora, blepharospasm, redness
• posterior: maybe no overt clinical signs

measure intraocular pressure!

• surgical emergency if acute and primary
• ciliary sulcus fixation with a new lens sutured in place to posterior iris

• surgical removal
• miotic agents (trap then lens in the back and monitor pressures until glaucoma results)
• +/- no therapy
• usually eventually needs enucleation or prosthesis

diffuse corneal edema, glaucoma, anterior uveitis, pain