KConus Flashcards
KConus is a bilateral but asymmetric dz caused by o____ stress - which products accumulate and lead to corneal thinning?
oxidative stress
ROS/RNS accumulate
-goal of Tx: minimize oxidative stress
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
white males
2nd-3rd decade
early onset = faster progression = more severe dz
T/F: KConus can cause monocular diplopia
true. Can even cause polyplopia (multiple images d/t light scatter in all directions)
mean flat-K values are ~__D (approximate), and mean irregular astigmatism is ~__D
flat K: 50D+/- 6
astig: 3.5D+/- 3
bulging of the lid on downgaze (worse in advanced cases) is called ____’s sign
munson’s sign
three classifications for topography in KConus:
- which is EASIEST TO FIT w/ CLs?
- which is MOST COMMON?
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
Name of the ring found @ the base of a cone? D/T deposition of what molecule?
Fleischer’s ring - deposition of IRON (found in 86% of KConus pts)
Name 6 biomicroscopic changes seen in KConus pts [FVASHH]
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
What’s the no. 1 choice of correction for KConus pts? Is the goal to improve vision and retard progression of KConus?
GP lenses
NO - goal is ONLY to improve vision - NOT to retard KConus
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?
true - might be able to mask SOME topographical irregularity
-Kerasoft IC (expensive; uses the Morocca VA assessment routine)
What does CLEK stand for? It studied the Hx of keratoconus but also whether apical ____ or ___ is more desirable to prevent apical SCARRING
collaborative longitudinal evaluation of keratoconus
clearance or touch
-also studied KConus vision, dz progression, scarring factors
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)
1) small dia
2) small OZD
3) FLAT PCs compared to BC
Rose K/K2: customizable GPs that (mimic/counter) the shape of the KConus cornea
mimic - elevate right where the nipple of the cone elevates
T/F: a small amt of central touch is ok on a rigid lens.
-other FA fitting goals?
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
where do you want your endpoint for fitting a KConus lens (name)? Better to have touch or clearance?
FDACL: first definite apical CLEARANCE lens
fitting: BC selected based on k____
- settling time? __-__ mins
keratometry
20-30 mins
troubleshooting: if there’s EXCESSIVE PARACENTRAL POOLING, what adjustment do you make?
decrease OZD (by @ least 0.4mm)
troubleshooting: if there’s EXCESSIVE MID-PERIPHERAL BEARING (TOUCH), what adjustment do you make?
flatten BC by 0.50mm; unless there’s excessive edge lift (where you’d steepen by 0.50mm)
troubleshooting: if there’s PERIPHERAL CLEARANCE, what adjustment do you make?
if minimal: flatten by 0.50mm
if excessive: steepen by 0.50mm
does the OR w/ the final diagnostic lens correlate well w/ the spectacle Rx? Tend to be high minus or high plus?
poor correlation
HIGH MINUS
large ovals or globus cones should have lenses w/ (large/small) diameters
large diameter
-and large OZD, flat BCs, and larger pooling areas under the lens
A piggyback system has what type of lens placed over another?
- why would you do it?
- biggest disadvantage?
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
What are the three zones in scleral lenses? What is the function of each? [CLS]
Corneal zone: vault cornea/cone
Limbal zone: clear the limbus (want to avoid compression)
Scleral zone: fitting zone (want even bearing across sclera)
when might you use a HYBRID lens in Keratoconus?
- EARLY to SEVERE Kconus (anytime)
- if pt has poor tolerance to GPs, or poor vision w/ specs or soft torics
PMD (pellucid marginal degeneration)
- band of thinning __-__mm in the ____ cornea, usually in the __-__ o’clock position
- protrusion occurs ____ to the cornea
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
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
BOWMAN’S layer - all others are normal
- 2nd-5th decade
- FALSE - NON-INFLAMMATORY (like KC). No vascularization, or iron findings like in KConus
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?
- striae/descemet’s folds
- acute hydrops
-gull-wing, kissing doves
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?
gutter - excavation/thinning toward limbal area
- superonasal
- superior steep zone (PMD was inferior)
