KConus

Question 1

KConus is a bilateral but asymmetric dz caused by o____ stress - which products accumulate and lead to corneal thinning?

Answer 1

oxidative stress

ROS/RNS accumulate

-goal of Tx: minimize oxidative stress

Question 2

No clear gender/race, but (white/black) (males/females) tend to get it more commonly according to CLEK study

• onset: __ to __ decade
• earlier onset = (faster/slower) progression

Answer 2

white males

2nd-3rd decade

early onset = faster progression = more severe dz

Question 3

T/F: KConus can cause monocular diplopia

Answer 3

true. Can even cause polyplopia (multiple images d/t light scatter in all directions)

Question 4

mean flat-K values are ~__D (approximate), and mean irregular astigmatism is ~__D

Answer 4

flat K: 50D+/- 6

astig: 3.5D+/- 3

Question 5

bulging of the lid on downgaze (worse in advanced cases) is called ____’s sign

Answer 5

munson’s sign

Question 6

three classifications for topography in KConus:

• which is EASIEST TO FIT w/ CLs?
• which is MOST COMMON?

Answer 6

1) nipple - EASIEST TO FIT- tends to be the most central
2) oval - sags a bit - MOST COMMON - will get inferior fit lens
3) globus - up to 90% of cornea

Question 7

Name of the ring found @ the base of a cone? D/T deposition of what molecule?

Answer 7

Fleischer’s ring - deposition of IRON (found in 86% of KConus pts)

Question 8

Name 6 biomicroscopic changes seen in KConus pts [FVASHH]

Answer 8

1) Fleischer’s ring
2) Vogt’s striae
3) Apical thinning
4) Corneal Scarring (ruptured Bowman’s)
5) acute Hydrops (ruptured Descemet’s allowing AH into stroma)
6) Hurricane/whorl/vortex staining

Question 9

What’s the no. 1 choice of correction for KConus pts? Is the goal to improve vision and retard progression of KConus?

Answer 9

GP lenses

NO - goal is ONLY to improve vision - NOT to retard KConus

Question 10

T/F: in mild/moderate KConus, you can get away w/ a SCL w/ a thicker design to treat kconus
-most common SCL for KConus?

Answer 10

true - might be able to mask SOME topographical irregularity

-Kerasoft IC (expensive; uses the Morocca VA assessment routine)

Question 11

What does CLEK stand for? It studied the Hx of keratoconus but also whether apical ____ or ___ is more desirable to prevent apical SCARRING

Answer 11

collaborative longitudinal evaluation of keratoconus

clearance or touch

-also studied KConus vision, dz progression, scarring factors

Question 12

GENERALLY: KConus GP lenses have three distinct features:

1) (small/large) overall diameter
2) (small/large) optic zone
3) relatively (steep/flat) PCs (compared to the BC)

Answer 12

1) small dia
2) small OZD
3) FLAT PCs compared to BC

Question 13

Rose K/K2: customizable GPs that (mimic/counter) the shape of the KConus cornea

Answer 13

mimic - elevate right where the nipple of the cone elevates

Question 14

T/F: a small amt of central touch is ok on a rigid lens.

-other FA fitting goals?

Answer 14

true. Small amt of clearance is ever better (apically)
- other: minimal para-central pooling, even mid-peri bearing/touch (support lens), peripheral clearance for tear exchange

Question 15

where do you want your endpoint for fitting a KConus lens (name)? Better to have touch or clearance?

Answer 15

FDACL: first definite apical CLEARANCE lens

Question 16

fitting: BC selected based on k____

- settling time? __-__ mins

Answer 16

keratometry

20-30 mins

Question 17

troubleshooting: if there’s EXCESSIVE PARACENTRAL POOLING, what adjustment do you make?

Answer 17

decrease OZD (by @ least 0.4mm)

Question 18

troubleshooting: if there’s EXCESSIVE MID-PERIPHERAL BEARING (TOUCH), what adjustment do you make?

Answer 18

flatten BC by 0.50mm; unless there’s excessive edge lift (where you’d steepen by 0.50mm)

Question 19

troubleshooting: if there’s PERIPHERAL CLEARANCE, what adjustment do you make?

Answer 19

if minimal: flatten by 0.50mm

if excessive: steepen by 0.50mm

Question 20

does the OR w/ the final diagnostic lens correlate well w/ the spectacle Rx? Tend to be high minus or high plus?

Answer 20

poor correlation

HIGH MINUS

Question 21

large ovals or globus cones should have lenses w/ (large/small) diameters

Answer 21

large diameter

-and large OZD, flat BCs, and larger pooling areas under the lens

Question 22

A piggyback system has what type of lens placed over another?

• why would you do it?
• biggest disadvantage?

Answer 22

Rigid lens ON TOP of SCL carrier

• decrease MECHANICAL trauma
• improve stability and comfort
• disadvantage: twice as many lenses, decreased Dk/t; tearing of soft lens

Question 23

What are the three zones in scleral lenses? What is the function of each? [CLS]

Answer 23

Corneal zone: vault cornea/cone
Limbal zone: clear the limbus (want to avoid compression)
Scleral zone: fitting zone (want even bearing across sclera)

Question 24

when might you use a HYBRID lens in Keratoconus?

Answer 24

• EARLY to SEVERE Kconus (anytime)

- if pt has poor tolerance to GPs, or poor vision w/ specs or soft torics

Question 25

PMD (pellucid marginal degeneration)

• band of thinning __-__mm in the ____ cornea, usually in the __-__ o’clock position
• protrusion occurs ____ to the cornea

Answer 25

thinning 1-2 mm in the inferior cornea, in the 4-8 oclock position.

protrusion in the superior part - normal thickness…

PMD is BILATERAL, PERIPHERAL

Question 26

what layer does PMD affect? are the others normal or abnormal

• when does this occur in life?
• T/F: you may see vascularization/fleischer’s ring/scarring like in KC

Answer 26

BOWMAN’S layer - all others are normal

• 2nd-5th decade
• FALSE - NON-INFLAMMATORY (like KC). No vascularization, or iron findings like in KConus

Question 27

PMD - name 2 findings that CAN occur/that you MAY see in PMD that are also seen in KConus

-what type of pattern might you see on topo?

Answer 27

• striae/descemet’s folds
• acute hydrops

-gull-wing, kissing doves

Question 28

Terrien’s marginal degeneration (not on test) - consists of a “g____” that progressively thins/widens over many years

• usually in ____-____ position
• where is the usually “steep” zone?

Answer 28

gutter - excavation/thinning toward limbal area

• superonasal
• superior steep zone (PMD was inferior)