DIS - Corneal Refractive Surgery Workup - Week 2 Flashcards by B H

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

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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

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Which refractive surgery is the most common and what percentage does it account for?

LASIK - 95%

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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

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What was the first method used to create a flap in LASIK? What is the flap thickness (range)?

Microkeratome
Flap thickness of 100 - 160um

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List two potential complications of using a microkeratome.

Partial flaps
Free caps

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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

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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

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What is the theoretical range for LASIK (myopia, hyperopia, and astigmatism)?

+4.00 to -8.00DS
Up to -5.00DC
-regular astigmatism

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What is an ideal age for LASIK?

> 21

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List 7 aspects of clinical history that should be taken.

Occupation
Hobbies/sporting activities
POH
FH
GH
Allergies
Monovision discussion (trial if appropriate)

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List 7 specific aspects of POH to ask a LASIK candidate.

Injury
Infection
Surgery
Laser surgery
Amblyopia
Strabismus
Current correction, including CL history

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List 4 specific aspects of FH to ask a LASIK candidate.

Glaucoma
Diabetes
Myopia
Retinal health

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List 3 specific aspects of GH to ask a LASIK candidate.

Medications
Systemic conditions
Surgical history

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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

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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

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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

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What three things should you do during a tear film assessment for a LASIK candidate?

NaFl + LG staining
Schirmer test without anaesthesia

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What three things should you check for when doing slit lamp examination on a LASIK candidate?

Blepharitis
Meibomianitis
Corneal scarring/dystrophies

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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

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What three things should you rule out when doing DFE on a LASIK candidate?

Retinal thinning
Holes
Partial detachment

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What is the purpose of cycloplegic refraction on a LASIK candidate?

Ensure theyre not overminused

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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

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List 5 absolute systemic contraindications to LASIK.

Pregnant/nursing women
Autoimmune disease and immunodeficiency
Collagen vascular disorder
Certain medications
Unrealistic patient expectations

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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?

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?

Is there a risk of corneal ectasia with phakic IOLs?

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?

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