Lens Dx Flashcards
Cataract VS Nuclear Sclerosis
Cataracts:
-> Blindness
- Retro- illumination highlights lens opacities
- Variable progression, usually faster than sclerosis
- Full fundus exam not possible
Nuclear Sclerosis:
- No blindness
- Retroillumination = transparent nucleus
- Fundus exam possible needs pupil dilation
- V slow progression
Nuclear Sclerosis
- Senile = increasing density of secondary fibers
- The fibers are arranged regularly, the light passes through unobstructed
- Occurs as the lens ages
- Advanced nuclear sclerosis similar to cataract
- Cloudy, circular central lens
- Retroillumination - full tapetal reflection
Cataract Formation
- Nutrition and waste removal relies on aqueous humor - no blood to lens
- Disrupt lens fibres = increase hydration and deposits lens protein = loss of transparency
- Uveitis, glaucoma and progressive retinal atrophy (PRA) are common causes
- Systemic metabolic diseases can lead to cataract formation due to the change in the ocular metabolism
- Diabetes mellitus is the most common endocrinopathy that causes cataract
Cataract Tx:
Surgery
Medical tx - anterior uveitis
Correct metabolic dx
Aetiology
Primary = inherited
Secondary
1. Metabolic dx
2. Intraocular dx (uveitis, endophthalmitis)
3. Trauma Electrocution
4. Toxic corticosteroids ketoconazole, DMSO
5. Senile
6. Radiation
Cataract Classification - Degree of Opacity
- Incipient
- Immature
- Mature
- Hypermature
- Morganian - starts to dissolve
Diabetic Cataract
Rapid dev
* Hyperglycemia altera metabolism of the lens
* Due to osmotic forces the water from the aqueous enters the lens
* Oedema of the lens fibers and vacuole formation ensues
* The level of hyperglycemia does not correspond with the progression of the cataract
* Early surgery is generally indicated
Lens Induced Uveitis
- Lens induced or phacoclastic uveitis
- Inflammatory reaction against lens proteins released from diseased lens
- Often severe and difficult to control medically
- Can be assumed in all patients with mature and hypermature
cataract - Must be recognized and treated before surgery
- Must be treated to prevent glaucoma and other secondary complications
- Topical NSAIDs or corticosteroids, often long-term, is needed to control uveitis
- Systemic NSAID may be required in severe cases
- Care must be taken with application of topical glucocorticoids, especially if diabetes is present
Cataract Surgery
- Surgery = only tx
- Short term = improve vision in early-stage nuclear cataracts
- Atropine 1% , 1 drop every 2-3 days, to effect (improves peripheral vision as the pupil is dilated)
- Medical management aimed at treating cataract complications (anterior uveitis)
- Lens induced uveitis assumed in all mature and hypermature cataracts
Cataract Surgery Complications
- Uveitis is inevitable- immunogenic lens proteins released after opening the capsule
- Lens fibre regrowth
- Post-operative spikes in IOP may be temporary but blinding) and
happen in 25-50% of dogs - The reported incidence of glaucoma varies between the studies 6.7% to 19.3%
- Retinal detachment –low prevalence (Bichon fries possibly predisposed)
- Posterior capsular opacifications (PCO) proliferation of the epithelial cells and fibrous metaplasia, called secondary cataract
- Intraocular hemorrhage
- Infection
- Leakage from the surgical site
Cat Cataracts
- Uncommon
- Congenital reported in Persian and British
shorthaired- very rare - Almost aways secondary:
➢Post inflammatory-uveitis
➢Traumatic
➢Metabolic- rare and slower compared to the dog
➢Secondary to other ocular disease (glaucoma, lens luxation)
➢Nutritional- arginine and histidine deficient diet in milk replacement formulas
Lens Luxation - 2 types
Primary - Hereditary
- Jack Russel/ fox terrier ADAMSTS17 gene mutation
Secondary - anterior uveitis, glaucoma, tumours, cataract
Posterior Lens Luxation
- Surgery
- Medical-miotic tx long-term = risk anterior luxation, glaucoma
- Complication = glaucoma
Anterior Lens Luxation
Dislocate lens from normal position
Zonules break down
1o/2o
