Refractive Mgmt/Intervention AAO Self-Assessment Flashcards
A preoperatively emmetropic and orthotropic patient is given the following glasses after bilateral cataract surgery: -0.50 -2.00 x 179 OD, +1.50 -1.00 x 90 OS, with +2.50 add OU located 1 cm below the optical center of the glasses. How much relative prism is induced when this patient looks through the top of his bifocals? 4Δ base-up over the right eye 10Δ base-down over the right eye 10Δ base-up over the right eye 4Δ base-down over the right eye
The amount of prism induced by the bifocals is equal in each eye and is canceled out. When this patient looks downward, only the power in the 90-degree meridian is deviating light. We can use Prentice’s rule to calculate the prismatic effect of these lenses: OD: -2.5D x 1 cm = 2.5Δ base-down OS: +1.5D x 1 cm = 1.5Δ base-up When these prism results are combined, the amount of induced prism is equivalent to 4Δ base-down over the right eye.
While performing retinoscopy on a 3-year-old, the retinoscopic reflex is neutralized by -3.00 sph OD and +3.50 sph OS. Assuming a working distance of 67 cm, what is the best prescription to give?
- 4.50 sph OD, +2.00 sph OS - 3.00 sph OD, +3.50 sph OS - 4.50 sph OD, plano OS - 3.00 sph OD, plano OS
Because 6.5 D of anisometropia is almost certainly amblyogenic if left uncorrected, the full cycloplegic refraction should be given, even in the hyperopic eye. In contrast to adults, children accept anisometropic corrections easily, but may have decreased stereopsis.
When performing a cycloplegic refraction for refractive surgery planning, which of the following medications provides strongest cycloplegia? 1% cyclopentolate 1% tropicamide 1% tropicalate 1% cyclopentamide
It is important to know a patient’s true refractive error, so it is necessary to paralyze accomodation by administering cyclopentolate. Although longer acting cycloplegics may be used, these are not well-tolerated by adults in a typical outpatient setting.
A 62-year-old patient wants to improve his distance glasses because of declining vision. Examination reveals 20/50 acuity OD and 20/40 acuity OS with refraction of -4.00 +1.50 X 180 OD and -2.50 +1.50 X 175 OS. Refraction does not improve his vision. Slit lamp exam reveals moderate cortical spokes and nuclear sclerosis bilaterally. Dilated exam is normal. What is an appropriate surgical approach?
Laser in situ keratomileusis (LASIK) alone
Cataract surgery with peripheral corneal relaxing incisions
LASIK followed by cataract surgery
Cataract surgery followed by conductive keratoplasty
This patient is a typical patient with a refractive error and a cataract. Provided no other ocular pathology is present, such as a corneal opacity or macular pathology, the inference is that his sub-optimal vision is a result of the cataract. If the patient has a functional visual complaint, the treatment for this condition is cataract extraction. With newer technologies now available, such as relaxing incisions and toric implant lenses, refractive surgery in this case is not indicated as these modalities can treat low degrees of corneal astigmatism. While LASIK could reduce his refractive error, it will not improve his visual acuity, and thus should not be employed as a first step. In the event of an IOL calculation error, LASIK may be beneficial to reduce this patient’s dependence on spectacles; however, this would be an unusual event.
Which of the following steps during surgery is critical when implanting a phakic intraocular lens?
Minimize rotation of the implant
Leave a very small amount of viscoelastic to prevent pupillary block
Rotate the posterior chamber implant 90 degrees to allow for maximal crystalline lens clearance
Generous amounts of viscoelastic should be used
The least amount of lens rotation is critical to avoid pigment dispersion into the anterior chamber angle. Viscoelastic should be used sparingly to avoid iris prolaspe.
An air traffic controller with 4 D of myopia and 1 D of accommodative amplitude wants single-vision glasses for viewing a video screen 80cm in front of her. If she uses half of her accommodative reserve, what power lenses should she be given?
- 2.75sph - 3.50sph - 3.00sph - 3.25sph
If the patient was fully corrected for distance, she would be able to see comfortably 2m in front of her using half of her accommodative reserve. The refractionist must supply the remainder in the glasses. The specified viewing distance, 80cm, is 1.25 D from the patient. Because the patient can provide 0.5 D, the ophthalmologist must provide the additional 0.75 D in the glasses. Thus, to meet the patient’s requirements, the single vision glasses should be -3.25 sph.
What principal factor(s) determine the magnitude of refractive correction associated with laser ablative surgery for myopia? Shape and depth of the ablation Keratometry readings Pupil size Corneal thickness
Among these options, the only one that influences the amount of refraction correction in myopic laser refractive surgery is ablation depth and shape. Keratometry readings affect the initial, and consequently the final refraction, but not the magnitude of correction (change).
What is the appropriate depth for placement of intrastromal corneal ring segments (INTACS) in a myopic cornea? Subepithelial 2/3 corneal thickness 1/3 corneal thickness Just above Descemet's membrane
In order for corneal ring segments to perform properly, implantation depth is critical. Too deep or too shallow can result in erosion and sub optimal effect.
A patient who wears soft contact lenses is being treated for a corneal ulcer. Initial gram stain and cultures were negative. There has been no improvement in their clinical findings after 3 days of fortified antibacterial antibiotics, and the patient continues to complain of severe pain. What is the most likely causative microbe? Yersinia Adenovirus Acanthamoeba Coagulase negative staphylococcus
One of the hallmarks of Acanthamoeba keratitis is severe eye pain. This patient is also a contact lens wearer, a known risk factor for Acanthamoeba. Acanthamoeba is resistant to fortified antibacterial therapy. These factors and the initial negative gram stain and culture results should raise the suspicion for Acanthamoeba. Coagulase-negative Staphylococcus should respond to fortified antibiotic therapy, making this an unlikely answer. Yersinia is an uncommon cause of keratitis. Adenovirus typically does not cause severe eye pain.
What is diffuse lamellar keratitis that presents 4 weeks after laser in situ keratomileusis (LASIK) most likely due to? Epithelial defect Atypical mycobacteria Medicamentosa Herpes simplex virus
Late onset DLK associated with epithelial defects has been reported. It is important for the LASIK surgeon to appreciate that this can occur, and that epithelial erosions or abrasions in LASIK patients may not follow the same course as in non operated patients. Mycobacterial keratitis, however has a different clinical appearance than DLK in that there is frequently an anterior chamber reaction (very rare in DLK). The infiltrates are frequently single or multiple, tend to be focal, and importantly – involve the stroma above and below the flap interface.
