Cataract quiz for residents, part 3

Test your knowledge and judgment as you assess risks and predict outcomes in six clinical scenarios.

Uday Devgan

This is the third and final part of the cataract surgery quiz for residents. Each question presents a challenging clinical situation. Use your best judgment to select the most appropriate answer.

1. This patient presents with a complaint of decreased vision in her left eye and she desires surgery to improve her vision. Examination shows 2+ nuclear sclerosis in both eyes and a large nasal pterygium only in the left eye. Her refraction in the right is close to plano with minimal astigmatism, yielding an acuity of 20/50. The left eye’s refraction shows 3 D of cylinder, which gives a best corrected acuity of 20/200. The right eye has a measured corneal power of 44 D spherical, but you are unable to get an accurate keratometry reading of the left eye due to distortion of the mires. Both eyes have axial lengths of exactly 23.50 mm, and both eyes have normal posterior segments. What is the best way to improve her vision in the left eye?

Question 1 image. Images: Devgan U

a.Perform the cataract surgery of the left eye using the keratometry readings from the right eye in order to do the IOL calculations.

b.Inject a pharmaceutical agent such as a steroid, 5-fluorouracil or mitomycin C into the pterygium.

c.Excise the pterygium, wait months until the cornea heals and stabilizes, then repeat the keratometry measurements, do the IOL calculations and perform cataract surgery.

d.Perform cataract surgery of the left eye and implant a toric IOL to treat her astigmatism, which is induced by the pterygium.

2. You have decided to try microincision cataract surgery (MICS), and you will be moving from your 2.8-mm incision (with a 1.1-mm diameter phaco needle) to a 2-mm incision (with a 0.8-mm diameter phaco needle). Your method of surgery is phaco chop, and you want to program new settings for the nucleus quadrant removal. For the 2.8-mm incision, you typically use a peristaltic phaco machine with 220 mm Hg vacuum, 35 cc/min flow and 80 cm bottle height. How should you program your phaco machine for the new 2-mm incision MICS procedure?

a.Lower the vacuum level, increase the flow rate and raise the bottle height.

b.Raise the vacuum level, decrease the flow rate and raise the bottle height.

c.Lower the vacuum level, decrease the flow rate and lower the bottle height.

d.Raise the vacuum level, increase the flow rate and lower the bottle height.

3. You performed cataract surgery on the patient. The case was complicated by a posterior capsule rupture and vitreous prolapse. You were able to place a three-piece acrylic IOL securely in the ciliary sulcus. Today you see the patient back in your clinic 3 days after the surgery. The slit lamp examination shows vitreous prolapsing around the optic and through the pupil (blue arrow) and leading to the temporal corneal incision (red). What are the potential risks to your patient during the postoperative period?

Question 3 image.

a.The patient is at a higher risk for retinal detachment because there is vitreous traction.

b.The patient is at a higher risk for cystoid macular edema due to vitreous traction.

c.The patient is at a higher risk for endophthalmitis due to the open posterior capsule and complicated surgery.

d.All of the above are potential risks.

4. A patient with a history of diabetic retinopathy has a moderate 2+ nuclear sclerotic/2+ posterior subcapsular cataract and desires surgery. This eye previously had panretinal photocoagulation for proliferative changes that have since regressed. When you look at the posterior segment in detail, there is no retinal thickening or hard exudates within 500 µm of the center of the macula. There is one area of retinal thickening, about one disc area in size, but its edge is about 750 µm below the fovea. What is the best way to proceed?

a.The patient needs to be treated for clinically significant macular edema before you proceed with cataract surgery.

b.Because there are no hard exudates or thickening within 500 µm of the center of the macula, do routine cataract surgery.

c.Do cataract surgery but keep the patient on topical steroids and NSAIDs for a prolonged period afterward.

d.Do cataract surgery using a larger incision manual technique to avoid delivering ultrasonic phaco energy into the eye.

5. This 75-year-old patient had a successful penetrating keratoplasty a few years ago and now presents to you requesting cataract surgery. You measure the endothelial cell count at 910 cells/mm². The cataract appears dense and white. What is the most likely risk for this patient during routine phacoemulsification?

Question 5 image.

a.The remaining 10-0 sutures could rupture during phaco, causing destabilization of the anterior segment.

b.You will need trypan blue dye to stain the lens capsule, but it will be toxic to the corneal endothelial cells.

c.The iris will likely prolapse through the phaco incision, leading to an iatrogenic iris defect and corectopia.

d.The phaco energy and fluid running through the eye can damage the corneal endothelium leading to a graft failure.

6. You are performing routine phacoemulsification surgery, and after removing the last nuclear fragment, there is a surge and the phaco tip punctures the center of the posterior capsule. What should your next step be?

a.Pull the phaco probe out of the eye so that vitreous does not get sucked into the phaco needle.

b.Do not pull the phaco probe out of the eye, but rather go to foot position 1 (irrigation only).

c.Pull the phaco probe out of the eye and then inject viscoelastic to inflate the anterior chamber.

d.Do not pull the phaco probe out of the eye, but rather go to foot position 2 (irrigation and aspiration) and raise the vacuum level.

Answers

1. c. Because both eyes have similar cataracts, the patient’s 20/200 vision in the left eye is due to both the pterygium and the cataract. The pterygium is distorting the cornea, inducing corneal astigmatism, and preventing accurate keratometry. The pterygium should be excised first. The cornea should be given at least a few months to heal and stabilize. At that point, the keratometry should yield accurate measurements that can then be used for the IOL calculations for cataract surgery of the left eye.

2. b. Raise the vacuum level, decrease the flow rate and raise the bottle height. For both inflow and outflow, there will be less flow due to the smaller size of the phaco tip and needle. For outflow, because the phaco needle is smaller gauge, you will need to raise the vacuum level to draw fluid through the phaco tip, and this fluid will come at a decreased rate, as explained by Poiseuille’s equation. For the inflow, the bottle should be raised in order to maintain the infusion pressure in the anterior chamber and prevent surge.

3. d. All of the above are potential risks. With the vitreous traction, the patient has a higher risk of retinal detachment and cystoid macular edema. And with an open posterior capsule in a complicated case, the risk of endophthalmitis is higher as well.

4. a. The patient meets the criteria for the diagnosis of clinically significant macular edema because of the retinal thickening of one disc area in size, any part of which is within one disc diameter of the center of the macula. This patient needs to be properly treated for clinically significant macular edema and given time to stabilize before proceeding with cataract surgery. Doing cataract surgery on this eye while clinically significant macular edema is present can worsen the macular edema and result in worse vision.

5. d. The patient already has a very low endothelial cell count, and the trauma from ultrasound and fluid flow can cause further cell loss and lead to graft failure. Because the cataract is quite dense, more energy may need to be used during surgery, posing an even higher risk. Plenty of viscoelastic should be used to protect the cornea, with frequent recoating. The phaco power and fluid flow can be minimized and care can be taken to operate within the capsular bag in order to keep a greater distance between the phaco tip and the corneal endothelium.

6. b. Do not pull the phaco probe out of the eye because this will cause the anterior chamber to depressurize and collapse, allowing vitreous to prolapse through the posterior capsule break. The phaco probe should be left in the eye and the foot pedal should be placed in position 1 to keep just the irrigation on. This keeps the anterior chamber pressurized and can prevent vitreous prolapse. Now, while still keeping the probe in the eye, the nondominant hand can be used to fill the anterior chamber with viscoelastic via the paracentesis incision.

Cataract surgery is a mix of manual dexterity, critical thinking and sound judgment. I trust that this quiz series has provided interesting and challenging clinical situations to help in your learning process. If you did well on these quizzes, pat yourself on the back but remember that mastering cataract surgery is a lifelong process.

• Uday Devgan, MD, FACS, FRCS(Glasg), is in private practice at Devgan Eye Surgery in Los Angeles, Beverly Hills and Newport Beach, Calif. He is also chief of ophthalmology at Olive View UCLA Medical Center and associate clinical professor at the UCLA School of Medicine. He can be reached at 11600 Wilshire Blvd., Suite 200, Los Angeles, CA 90025; 800-337-1969; fax 310-388-3028; email: devgan@gmail.com; website: www.devganeye.com.
• Disclosure: No products or companies are mentioned that would require financial disclosure.