Cornea / Refractive surgery Flashcards
Your patient had LASIK over one year ago, and her prescription has regressed slightly by 1.25 D of myopia. She wishes to get an enhancement and asks you what is the MOST common complication associated with a LASIK enhancement?
Flap dislocation
Post sub-capsular opacification
Correct answer
Epithelial ingrowth
Presbyopia
Explanation - The most common complication associated with an enhancement after previously undergoing LASIK is epithelial ingrowth. Although this condition can occur after the first LASIK procedure due to poor flap adhesion or from stray epithelial cells remaining under the flap, it is far more common with enhancements. Some surgeons are attempting to decrease the incidence of ingrowth occurrence with enhancements by re-cutting a new flap or via refractive keratotomy (RK). In general, ingrowth does not cause a problem if it is isolated to a small area and if there is little elevation or change with time. If the ingrowth is significant and vision is compromised, treatment requires that the flap be lifted and the offending cells removed.
Posterior capsular opacification only occurs after cataract surgery when residual lenticular epithelial cells proliferate, causing opacification of the posterior aspect of the space between the posterior lens implant and the posterior capsule. If vision is compromised, treatment requires that the cells be removed via a YAG laser.
Which 2 of the following agents stain dead cells, devitalized cells, and mucin? (Select 2)
Sodium fluorescein
Methylene blue
Rosebengal
Lissamine green
Explanation - Rose Bengal is an iodine derivative of fluorescein that preferentially stains the nuclei of devitalized cells, dead cells, and mucin. It is typically applied via a moistened filter paper strip or in drop form to the conjunctiva and is very helpful in evaluating keratoconjunctivitis sicca, herpes simplex lesions, corneal abrasions, ulcerations, foreign bodies, and conjunctival tissue changes. Rose Bengal has also been shown to have some antiviral properties.
Lissamine green stains degenerated cells, dead cells, and mucous in a very similar manner to that of Rose Bengal; however, lissamine green is preferentially used due to marked ocular irritation and discomfort that tends to occur more frequently with the use of Rose Bengal.
Methylene blue has properties similar to Rose Bengal but also has the ability to stain corneal nerves.
Sodium fluorescein is the most widely utilized dye for use in eye care due to its low toxicity and excellent fluorescent properties. It is most commonly used in the assessment of corneal and conjunctival lesions, foreign bodies, in the fitting and management of contact lenses, and in the measurement of intraocular pressure.
Which of the following corneal conditions occurs as a result of excessive amyloid deposition?
Fleck dystrophy
Lattice dystrophy
Granular dystrophy
Macular dystrophy
Answer: C
Explanation - Lattice dystrophy is an autosomal dominant dystrophy (except for type III, which is autosomal recessive) with four sub-types categorized according to age of onset, systemic involvement, causative mutation, and appearance. Essentially, this condition is due to a deposition of amyloid that causes a decrease in visual acuity. The opacifications in this dystrophy appear as thick or thin lines and dots (depending on the sub-type).
Granular dystrophy results from a deposition of eosinophilic hyaline in the anterior stroma. Again, this condition is autosomal dominant and onsets in the first decade of life. As time passes, the deposits tend to coalesce and cause a decrease in visual acuity. Granular dystrophy presents with a clear limbal zone. The stroma between the opacities remains clear in the early stages of the condition.
Macular dystrophy occurs secondary to a deposition of glycosaminoglycans (mucopolysaccharides) in the stroma during the first decade of life. This condition is autosomal recessive and causes poor vision by the time the patient reaches roughly 20-30 years of age due to corneal thinning and enlargement of opacities that involves all of the corneal layers. This dystrophy extends to the limbus. The preferred surgical intervention is a corneal transplant. Macular dystrophy is the most visually devastating of the three stromal dystrophies mentioned here.
A good mnemonic for committing this to memory is: Marilyn Monroe Got Hers in Los Angeles (Macular-Mucopolysaccharide, Granular-Hyaline, Lattice-Amyloid).
Fleck dystrophy is an autosomal dominant condition that has an onset in the first decade of life and occurs due to fleck or comma-like deposition of glycosaminoglycan in the stroma. This dystrophy rarely requires any intervention.
Your patient calls you at home because they have lost their pre-LASIK patient instructions and they have forgotten all the restrictions. Which of the following actions is permitted?
Driving home after the surgery
Swimming the day after surgery
Wearing contact lenses the day before the surgery
Eating or drinking the day of the surgery
Answer : D
There are no restrictions placed upon the ingestion of food or drink the day of the surgery; however, the consumption of alcohol the day of surgery is not recommended. The patient should absolutely not wear their contact lenses since a clear, clean and defect-free cornea is essential the day of the surgery. Contact lenses can alter the shape of the cornea (and the prescription) which will alter the final visual outcome. Legally, the patient will not be allowed to drive home after the surgery. In case of an accident, the surgeon may be held liable. Patients are not allowed to swim or go into a hot tub for at least one week post-LASIK (two weeks is preferable). Patients are also advised not to get water or shampoo in their eyes while showering for a week post-surgery.
In cases of epidemic keratoconjunctivitis (EKC), subepithelial infiltrates (SEIs) typically appear within how many days after the onset of the disease?
1-2 days
8 days
14 days
SEIs are not associated with EKC
10-12 days
Answer - 14 days
Epidemic keratoconjunctivitis typically runs a common clinical course that begins with characteristic signs and symptoms following an 8-10 day incubation period. Initially, patients will usually complain of eyelid edema, pain, photophobia, and lacrimation. Early conjunctival clinical signs include a mixed papillary and follicular response, hyperemia, chemosis, and subconjunctival hemorrhages that typically last for 7-21 days. In more severe cases, the development of a conjunctival membrane or pseudomembrane is possible.
Corneal involvement in patients with EKC is variable, but most patients develop diffuse, fine, superficial keratitis within the first week of the onset of the disease. After about 6-13 days, focal punctate epithelial lesions that appear elevated and stain with sodium fluorescein often occur, and by day 14, subepithelial opacities develop under these focal lesions in about 20% of patients. These subepithelial infiltrates may affect vision and can persist for months to years but typically will eventually resolve without scarring or neovascularization.
Which 2 of the following statements regarding laser-assisted in-situ keratomileusis (LASIK) and contact lens wear are TRUE? (Select 2)
Soft contact lenses should be removed 2 weeks prior to the procedure
Toric contact lenses should be removed for a minimum of 6 weeks prior to the procedure
Soft multifocal contact lenses must be discontinued 4 weeks prior to the procedure
Extended wear contact lenses should be removed for a minimum of 2 weeks prior to the procedure
Rigid contact lenses should be removed for 1 week per decade of wear prior to the procedure
Daily disposable contact lenses may be worn until 2 days prior to the procedure
Contact lenses of all types can have an effect on a patient’s tear film, corneal topography, and refractive error. Therefore, it is important to have a patient discontinue wear of their contact lenses for a certain timeframe prior to surgery. The FDA requires patients to be out of soft contact lenses for a minimum of 2 weeks prior to any customized procedure. Because rigid gas-permeable lenses can have a more dramatic effect on corneal topography and thus on refractive error, they require a longer time for the cornea to normalize. The FDA requirement is a minimum of 1 month with the recommendation of 1 month for every decade of wear or until the corneal topography is stable.
Answer A and D
What is the phenomenon referred to as Sattler’s Veil?
Colored fringes seen around bright lights due to corneal edema
Haloes or ghosting around dark objects seen due to multiple sclerosis
Shadows in the peripheral vision seen due to lactose intolerance
Constant flashes in the periphery seen due to optic nerve damage
Explanation - When the cornea swells, light becomes scattered by basal cells which act as diffraction gratings to produce diffraction rings.
Corneal edema can cause the appearance of colored fringes around bright sources of light. All other options are purely fictional.
Answer A
Your patient has keratoconus and is pregnant. She would like to know if this condition is hereditary. What is the MOST appropriate response to this question?
Yes, keratoconus is hereditary 100% of the time
Yes, there is a hereditary component to keratoconus but it presents with incomplete penetrance
No, keratoconus has a high correlation with hypertension
No, there is no hereditary component associated with keratoconus
Explanation - Although there still remains a lot of debate regarding the genetic link to keratoconus, according to the collaborative longitudinal evaluation in keratoconus study (CLEK) it is believed that the condition is autosomal dominant with incomplete penetrance.
Therefore, there is a slightly higher chance of her child manifesting keratoconus; however, the odds are still quite small. Most patients with diagnosed cases of keratoconus do not profess a family history of the condition. Keratoconus does appear to be linked to eye rubbing, although whether this is a cause or simply a symptom is unclear at this point. There also appears to be a very high correlation between keratoconus and atopy. People who suffer from eczema, allergies, and hay fever tend to display a higher incidence of keratoconus compared to the rest of the general population. Again, this subset of people has a high correlation of eye rubbing associated with ocular irritation, which may contribute to the formation of keratoconus.
Answer: B
Which of the following findings would you expect to see in a patient with Grade 2+ diffuse lamellar keratitis (DLK)?
High levels of irregular astigmatism
A slight hyperopic shift in vision
No change in refractive error
Large central epithelial defects
Diffuse lamellar keratitis is a non-infectious inflammation at the interface between the corneal flap and the stroma in patients who have undergone a LASIK procedure.
As the inflammation advances, the stromal tissue melts resulting in a flattening of the cornea and a hyperopic shift.
DLK does not result in corneal epithelial defects and usually does not result in high levels of irregular astigmatism.
Answer : B
Which of the following systemic conditions is MOST commonly associated with the development of interstitial keratitis?
Herpes simplex
Chlamydia
Lyme disease
Human immunodeficiency virus
Syphilis
Sarcoidosis
The presence of interstitial keratitis (IK) is essentially synonymous with congenital syphilis in most cases but may also occur in association with other infective causes such as Lyme disease, leprosy, and other viral diseases. Due to the common connection with congenital syphilis, all patients diagnosed with interstitial keratitis must undergo treponemal serology testing irrespective of the presence or absence of other associated clinical finding
Answer: Syphilis
Which type of hypersensitivity reaction (Gell and Coombs classification) is responsible for allergic conjunctivitis?
Type III Hypersensitivity
Type IV Hypersensitivity
Type I Hypersensitivity
Type II Hypersensitivity
According to the Gell and Coombs classification of hypersensitivity reactions, Type I reactions are IgE-mediated reactions that result in an immediate response occurring within minutes of exposure. This type of reaction is seen in allergic disease. Type II reactions are antibody-dependent cytotoxic reactions that are mediated by IgM/IgG and complement. Type III reactions are due to immune complex formation. Immune complex diseases include systemic lupus erythematosus, arthus reactions and serum sickness. Type IV hypersensitivity is delayed-type hypersensitivity and is the result of T-lymphocyte response. Typically, symptoms will occur 2 days after exposure. Prime examples include the PPD test for TB, contact dermatitis, and chronic organ transplant rejection.
Answer : C
