Ch 17 Anterior Segment OCT

Question 1

Name the 5 criteria for keratoconus risk in Anterior Segment OCT:

Answer 1

All are calculated in the central 5mm:

1. difference between minimum thickness and mean thickness < -63um
2. The difference in average thickness of the inferior (I) octant and the superior (S) octant is less than −31 μm (I − S < −31 μm).
3. The difference in average thickness of the inferotemporal (IT) octant and the superonasal (SN) octant is less than −48 μm (IT − SN < −48 μm).
4. Minimum corneal thickness is less than 492 μm.
5. The thinnest region of the cornea is outside of the central 2-mm area.

_{<strong>1 abnormal parameter: sugestive</strong>}

_{<strong>2 abnomal parameters: Dx</strong>}

Question 2

What is the special utility in the messurement of residual stromal bed after LASIK using AS-OCT?

Answer 2

That it can do it in vivo, without the need for a flap lift, as it would be with a pachymeter.

Question 3

How is the corneal power estimation afected after keratorefractive surgery if a keratometer is used?

Answer 3

Overestimated afer miopic corrections

Underestimated after hiperopic corrections

Question 4

Is the central corneal power calculated by the AS-OCT more or less accurate than that of a keratometer after refractive surgery?

Answer 4

Is more accurate

This is because it images both the anterior and posterior corneal curvatures, which means that there will be no under/over estimation produced by the loss of anterior/posterior relationship.

Question 5

Can the AS-OCT be used to image and plan for corneal opacities?

Answer 5

Yes

OCT has more penetrance than other light based instruments, and therefore can be used to messure, follow, asess and surgical planing of corneal opacities.

It could even provide more information of the opacified cornea than UBM.

Question 6

How would you describe this AS-OCT of a patient in the post op of DSAEK:

Answer 6

The image shows a detachment of the endothelial graft and corneal edema.

Question 7

What is the safe Lens Rise in anterior segment imaging for Artisan PIOL placement?

Answer 7

Lens Rise (distance between the anterior pole of the lens and the angle recess plane)

>0.6mm is of risk for PIOL placement