OSCE 3 Objective Structured Clinical Examination of FRCOphth examإمتحان الزمالة البريطانية للعيون
A 65-year-old female complains of gradual painless deterioration of vision in both eyes more in the right eye. She had previous cataract surgey in the right eye 6 years ago.
A case of Fuchs’ endothelial corneal dystrophy which is a non-inflammatory, sporadic or autosomal dominant, dystrophy involving the endothelial layer of the cornea resulting in a reduction in the number of Na+/K+ ATPase pumps. Over the course of decades, the cornea develops guttae and increases in thickness, causing glare, halos, and reduced visual acuity. It is more common in females.
Clinical findings:
Right eye is pseudophakic with YAG posterior capsulotomy done.
Left eye lens nuclear sclerosis.
Both eyes: Guttata on Descemet's membrane: the guttata tend to be central and slowly become more prominent peripherally.
Differential diagnosis:
1. Pigment dispersion syndrome
2. Keratic precipitates from uveitis
3. Herpetic stromal keratitis
4. Pseudophakic or aphakic bullous keratopathy
5. Iridocorneal endothelial (ICE) dystrophy
6. Congenital hereditary endothelial dystrophy
7. Congenital stromal dystrophy
8. Toxic anterior segment syndrome
9. Posterior Polymorphic Membrane Dystrophy
Precautions during cataract surgery:
Preoperative:
1-Patient counselling: The nature of the disease that it is progressive and the need for another surgery as corneal transplant.
2-Surgical procedure choice: Is the cataract significant?
a-Once a cataract is visually significant; and the cornea condition is mild, a decision must be made on proceeding with cataract surgery alone.
b-If the cornea condition is severe with visually significant cataract; a decision must be made on proceeding with cataract surgery combined with a corneal transplant, also known as a triple procedure (Keratoplasty + cataract extraction + IOL).
c-If the visual impairment is caused more by the corneal pathology rather than a cataract; it may still be prudent to remove the cataract at the time of corneal surgery. The cataract will likely progress and become visually significant in the future as a result of natural aging or from postoperative long-term topical steroid use. Proceeding in this manner would also prevent further endothelial cell damage associated with a subsequent surgery.
3-Ultrasound pachymetry and endothelial cell density, by specular microscopy. Pachymetry measurements greater than 640 µm and, or endothelial cell density of less than 1000 per mm2 place a patient at increased risk for corneal decompensation following cataract surgery.. In this situation, , it may be prudent to undergo a triple procedure.
4-Anterior segment OCT, Confocal Microscopy or Corneal Topography for objective quantification of corneal haze, also known as backscatter, to serve as a more sensitive parameter for corneal endothelial cell health.. Backscatter, specifically as measured by confocal microscopy, has been shown to be more precise than corneal pachymetry in predicting the need for corneal transplant following cataract surgery.
5-Control IOP and treat Ocular Hypertension if present.
Intraoperative: Surgical Technique: See the comments of the Video of Secrets of Cataract with Fuch's Endothelial Dystrophy.
Postoperative:
1-All patients with low corneal endothelial cell counts preoperatively should be counselled on prolonged visual recovery due to more significant and prolonged corneal oedema that can negatively impact visual acuity.
2-These patients often require more frequent administration and more prolonged use of topical steroids in the postoperative period.
3-Medical therapy for the treatment of pseudophakic corneal edema is multifaceted and directed towards the suspected etiology. General therapy includes the use of Muro 128 5% a hypertonic saline (5%) in either solution or ointment form to desiccate the corneal stroma.
4- If IOP is elevated, this can also compromise endothelial cell function and lead to oedema. Medical therapy should be directed towards lowering IOP with the use of one or more topical antihypertensive medications. If medical therapy cannot lower the IOP sufficiently, surgical intervention may be warranted.