DIS - Corneal Refractive Surgery Workup - Week 2 Flashcards
List 5 types of refractive surgery.
Laser in-situ keratomileusis -LASIK - most common Photo-refracrive keratectomy -PRK Laser assisted sub-epithelial keratectomy -LASEK Phakic IOLs -implantable contact lenses Refractive lens exchange
List 8 common reasons for having refractive surgery.
Convenience Cosmesis Increased security Lifestyle choice Vision entry requirement Sport/hobby Intolerance/poor comfort with contact lenses Cumulative cost saving
Which refractive surgery is the most common and what percentage does it account for?
LASIK - 95%
Briefly describe the procedure for LASIK (3).
A thin flap is created in the anterior cornea (epithelium, bowmans layer, anterior stroma)
When folded back, it exposes the central stroma
An excimer laser is used to permanently remove corneal tissue
The flap is replaced
What was the first method used to create a flap in LASIK? What is the flap thickness (range)?
Microkeratome
Flap thickness of 100 - 160um
List two potential complications of using a microkeratome.
Partial flaps
Free caps
What is an alternative to using a microkeratome? Describe the flap in comparison, its thickness and what two additional things you would expect using this method.
Femtosecond laser Uniform, thin, planar flap Consistent thickness Less suction Flap oedema Transient light sensitivity
Compare the two methods of flap creation for LASIK in terms of complication rates and visual outcomes.
Both have low complication rates and good visual outcomes
What is the theoretical range for LASIK (myopia, hyperopia, and astigmatism)?
+4.00 to -8.00DS
Up to -5.00DC
-regular astigmatism
What is an ideal age for LASIK?
> 21
List 7 aspects of clinical history that should be taken.
Occupation Hobbies/sporting activities POH FH GH Allergies Monovision discussion (trial if appropriate)
List 7 specific aspects of POH to ask a LASIK candidate.
Injury Infection Surgery Laser surgery Amblyopia Strabismus Current correction, including CL history
List 4 specific aspects of FH to ask a LASIK candidate.
Glaucoma
Diabetes
Myopia
Retinal health
List 3 specific aspects of GH to ask a LASIK candidate.
Medications
Systemic conditions
Surgical history
List 12 components of a clinical work-up for a potential LASIK candidate.
Ocular dominance Uncorrected vision Cover test / phoria Habitual correction (D/N) Subjective refraction - dry (D/N) Pupil size (bright/dim) Corneal topography Slit lamp assessment -tear film assessment IOP Pachymetry DFE Cycloplegic refraction
What is the expectation with contact lens wear (soft and rigid) prior to doing corneal topography on a LASIK candidate? What three things should you check for on topography and what should you do?
No SCL wear for a minimum of 1 week or 4 weeks for RGP
Check for irregularity, asymmetry, and ectasia
Predict post-operative K readings
What should you be weary of with topography on a LASIK candidate and why? What may result if LASIK is done on hyperopic eyes with >49D K readings and myopic eyes <36D?
Be weary of extremely flat or steep corneas
<36D - may result in poor post-operative optics
>49D - may result in more dry eye symptoms
What three things should you do during a tear film assessment for a LASIK candidate?
NaFl + LG staining
Schirmer test without anaesthesia
What three things should you check for when doing slit lamp examination on a LASIK candidate?
Blepharitis
Meibomianitis
Corneal scarring/dystrophies
What is the required post-operative CCT? What three things does ablation depth depend on and approximately how many microns per dioptre?
≥410um
Ablation depth based on optic zone diameter, blend zone, and refractive error
-15um per D
What three things should you rule out when doing DFE on a LASIK candidate?
Retinal thinning
Holes
Partial detachment
What is the purpose of cycloplegic refraction on a LASIK candidate?
Ensure theyre not overminused
List 6 absolute ocular contraindications to LASIK.
Refractive instability -more than 0.5D over 12 months Corneal ectasia (any form) or irregular topography Significant corneal scarring Relatively thin corneas -baseline thickness <500um Active corneal pathology Monocularity
List 5 absolute systemic contraindications to LASIK.
Pregnant/nursing women Autoimmune disease and immunodeficiency Collagen vascular disorder Certain medications Unrealistic patient expectations
List 2 medications that are an absolute contraindication to LASIK.
Isotretinoin
Amiodarone
List 3 relative systemic contraindications to LASIK.
Oral corticosteroid use
Hormone replacement therapy
Diabetes
List a relative general health contraindication to LASIK.
History of keloid scarring
List 2 relative prior ocular history contraindications to LASIK.
Herpes simplex
Herpes zoster
List 7 relative ocular health contraindications to LASIK.
Severe dry eye Severe atopy Severe eyelid disease Corneal neovascularisa7on Recurrent corneal erosions Glaucoma Large pupil size
List 3 relative occupation contraindications to LASIK.
Armed forces
Fighter pilots
Railways
Are contact sports considered a LASIK contraindication?
Yes, a relative one
What is the typical optom (4) and ophthal (1) follow-up schedule for LASIK post-operative evaluation?
Ophthal - day 1
Optom - week 1, month 1, month 3, month 6
What is the post-operative treatment for LASIK, including dosage and duration (3)?
Ciprofloxacin + pred forte qid -7 days Regular non-preserved lubrication -q1h for 48h -q2h for 1m -qid for first 3/12
What instructions are patients given post-operatively for LASIK and what may they be given?
Not to rub eyes
Protective eye shield overnight
-7 days
What are three normal symptoms of LASIK on the day of surgery?
Mild foreign body sensation
Mild ocular discomfort
Hazy vision
What three things should you do a day after LASIK surgery?
History
UCVA
Slit lamp
What four things should you do a week after LASIK surgery?
History
UCVA
BCVA
Slit lamp
What may be occurring in patients with patients not correcting to 6/6 or pre-op BCVA at one week post-LASIK?
Flap or interface complications
What two things should you especially look out for when doing slit-lamp a week after LASIK?
DLK
Early epithelial ingrowth
What five things should you do a month after LASIK surgery?
History UCVA BCVA Slit lamp Tonometry
What can be expected of Rx during the first month post-LASIK and why?
Slight over-correction of Rx not unexpected
-due to calcaulated nomograms that anticipate a natural regression effect
What may be expected of astigmatism a month after LASIK and why?
Mild induced astigmatism due to corneal remoulding or tear film disruption
What six things should you do three months after LASIK surgery?
History UCVA BCVA Slit lamp Topography Tonometry
What is expected of refraction and VA in patients 3 months after LASIK?
Most will have stable refraction and VA
What is the predicted time course for the following:
Halos and glare at night
Fluctuations in vision
Dry eye
Halos and glare at night - 4-6 weeks
Fluctuations in vision - 4-6 weeks, up to 3 months
Dry eye - 3-9 months
What is the proportion of intra-operative complications vs post-operative for LASIK (percentage)?
Intra-operative - 95%
Post-operative - 5%
What is the incidence of intra-operative complications for LASIK?
0.16 to 0.32%
List 3 types of intra-operative complications that can occur during LASIK.
Microkeratome induced
Laser induced
Epithelial defects
List 7 types of post-operative complications that can occur after LASIK.
Striae DLK Infection Epithelial ingrowth Posterior segment (very rare) Residual refractive error Corneal ectasia
List 5 microkeratome-induced complications that can occur during LASIK.
Button-hole Incomplete/short flap Free cap Variable thickness/irregular cut Contamination of interface
In what corneal K readings are button-holes and free caps more common?
Button-hole - >48D
Free cap - <41D
Are femto-second created flaps more or less accurate vs microkeratomes?
More accurate
Describe transient light sensitivity sydrome.
Ccute light sensitivity, 2-4 weeks post-surgery in the absence of visual or slit lamp signs
Occurs with femtosecond created flaps
What 5 things may epithelial defects be due to (intra-operative complication)?
Manipulation of the cornea during the procedure
Overuse of topical anaesthetic
Presence of pre-existing epithelial instability
Older age
Diabetes
How should epithelial defects be treated (3)?
Like a corneal abrasion
- bandage CL overnight
- antibiotic coverage
- regular lubrication
What do epithelial defects increase the risk of (2)?
DLK
Epithelial ingrowth
What are flap striae frequently caused by and in what type of eyes?
Eye rubbing/squeezing
-also poor flap placement
More common in myopic eyes
Do flap striae affect vision?
If central, yes
List three treatment options for flap striae.
Lift and smooth flap technique
Hypotonic saline
Suture flap
What is another name for diffuse lamellar keratitis?
Sands of Sahara
When does DLK appear?
During the first week
What is diffuse lamellar keratitis?
Inflammatory condititon located at the stromal interface
Is DLK uni- or bilateral?
Either
Does DLK have symptoms?
No
Is the anterior chamber generally quiet with DLK?
Yes
What causes DLK?
Accumulation of white blood cells pushing up on flap, typically at the edge of the flap
-eosinophils, neutrophils, lymphocytes
What can severe cases of DLK result in?
Stromal necrosis leading to flap melt and potential corneal scarring
What is the aetiology of DLK?
Unknown
Probably multi-factorial
-inflammatory response to foreign antigen
-Toxic response to dead Pseudomonas cell wall protein found in
instruments and auto-clave
What is the treatment for DLK? What may severe cases require and what should be monitored?
1% pred forte q1h Monitor daily Taper steroids over 3-4 weeks Severe cases may require irrigation with steroid Monitor IOP
What is epithelial ingrowth?
Epithelial surface cells grow into the flap interface
When do epithelial ingrowths occur? Can they occur after 4 weeks?
Occurs 1-4 weeks post-op
-will not develop after 4 weeks
What can epithelial ingrowth result in if significant?
Cap melt within 1-4 weeks
List 5 symptoms of epithelial ingrowths. Are they common?
Often asymptomatic Glare Photophobia Tearing Mild ocular discomfort Visual distortion (if central)
What five things are epithelial ingrowths associated with?
Epithelial defects Irregular flaps Previos corneal surgery Anterior basement membrane disease Flap lifts
Why can corneal melt occur with epithelial ingrowth?
Due to collagenases released by dying, trapped epithelial cells
List four symptoms of infectious keratitis. Is it common or rare?
Pain Epiphora Photophobia Reduced VA Rare
When can infectious keratitis occur post-LASIK?
Any point during the recovery period
What can infectious keratitis initially appear similar to?
DLK
What are the two most common causes of infectious keratitis?
Gram + bacteria
Mycobacterium
What two things may be required for infectious keratitis?
Intensive broad spectrum antibiotics initially
May require flap lift with scraping and irrigation with antibiotics
List 5 contributors to dry eye post-LASIK.
Neurotrophic disease Tear film instability True aqueous deficiency Local inflammation Corneal exposure
When does dry eye peak post-LASIK?
A month after surgery
What is a major risk factor for post-op dry eye? List 2 more.
Pre-existing dry eye
Deeper ablations
Thicker flaps
List 4 posterior segment complications that may occur post-LASIK. Is there a direct cause?
Retinal detachment Choroidal neovascularisation Macular hole Macular haemorrhage No conclusive evidence of LASIK being the direct cause
When can post-LASIK ectasia occur? Is it common or rare?
May occur at any time after surgery
Relatively rare
List four potential risk factors for post-LASIK ectasia, with the most significant one first.
Abnormal pre-operative topographic indices
Younger age (<30)
Higher myopia (>8.00D)
Thinner pre-operative corneal thickness
What is the management for post-LASIK ectasia?
Similar to keratoconus
Briefly describe PRK.
Debridement of the corneal epithelium, followed by application of the excimer laser onto the stromal surface
Briefly describe LASEK.
Epithelium is retained, however an alcoholic solution is used to weaken the epithelial cells so they can be folded out of the way
List three indications for PRK and LASEK.
Mild/moderate Rx with thin cornea
-where there is concern about post-operative ectasia
Recurrent erosions/epithelial basement disease
Predisposition to trauma (martial arts, military)
Between PRK and LASIK, which has decreased overall inflammation and faster visual rehabilitation?
LASIK
What does the creation of a corneal flap induce in LASIK?
Physical weakening to the cornea (permanent)
Between LASIK and PRK, which has less overall rates of dry eye?
PRK
What are the visual outcomes like between LASIK and PRK?
Comparable outcomes for myopia and hyperopia at one year post-surgery
What is the post-operative care for LASEK and PRK (8)? Give duration and dose if appropriate.
Bandage CL 1 week Topical corticosteroids qid Topical antibiotic qid Acular bid (day of surgery and day 1) Non-preserved lubricants q1h Topical antibiotic 2 days after bandage CL removal Topical steroids tapered very gradually (12 weeks) IOP needs to be monitored
What is UCVA like over time with PRK and LASEK?
Initially very good for the first 2 days, then may drop off as surface abrasion heals
What may you see initially on the patients epithelium in PRK and LASEK? Does it affect vision?
Epithelium will have an oedematous line at junction point of re-epithelialisation which may further blur patients VA for 2-3 days
What are phakic IOLs?
Surgically implanted contact lenses
Where are phakic IOLs positioned?
On or behind the iris and in front of the lens
What level of ametropia (and type) is an indication for phakic IOLs.
High myopia
-5.00D to -20.00D
List four qualities of a good candidate for phakic IOLs.
Pre-presbyopic high myope
Deep anterior chamber
Adequate endothelial cell count
No cataract
When are phakic IOLs considered?
When LASIK/PRK/LASEK re contraindicated
Do phakic IOLs induce higher order aberrations?
No
Is there a risk of corneal ectasia with phakic IOLs?
No
What provides better vision for high myopes, laser surgery or phakic IOLs?
Phakic IOLs
What are the risks of phakic IOLs similar to? List them (8).
Cataract surgery
- IOP rise
- endophthalmitis
- CMO
- hypopyon
- hyphaema
- corneal oedema
- retinal detachment
- cataract
What is the post-op care of phakic IOL surgery similar to? What is required annually (at least)?
Cataract surgery
-at least annual specular microscopy of the corneal endothelium
What endothelial cell count is a contraindication for phakic IOLs?
<2000mm2
What is refractive lens exchange?
Removal of the crystalline lens for refractive
purposes
What does refractive lens exchange eliminate the need for?
Future cataract surgery
List two indications for refractive lens exchange.
Moderate to high myopia
Hyperopia
Is refractive lens exchange often considered for patients under 50?
No
What does refractive lens exchange carry and increased risk of and in what type of eyes?
Retinal detachment, especially in young, high myopic eyes
List 5 qualities of a good candidate for refractive lens removal.
Incipient cataract Significant refractive error Presbyopia Strong desire for reduced dependence on spectacles/CLs Need to lower IOP
What two types of refractive error would make for a good candidate for refractive lens exchange.
Significant hyperopia with low astigmatism
