RESIDENT'S REVIEW

A Toric Lens + LRIs = Less Residual Astigmatism for a Patient

By Capt. Michael A. Blair, MD, USAF, MC

A 51-year-old African American male presented with a unilateral 2+ nuclear sclerosis cataract of the right eye and trace NS in the left eye. The patient had no history of trauma, steroid use or other pertinent ocular history. His refraction on initial screening was −8.00 +5.00 × 090 OD and −4.00 + 3.50 × 088 OS. His BCVA was 20/50 OS and 20/20 OS. In this patient, an emmetropic outcome after cataract surgery could pose potential problems.

A preoperative workup of the patient showed no ocular pathology. Keratometry showed values of 42.78/46.68 @ 92 OD and 42.99/46.62 @88 OS. His axial length was 24.3 OD and 24.07 OS. Pinhole PAM showed potential VA of 20/20 OD. An Orbscan (Bausch + Lomb) of the eye is shown in Figure 1.

Figure 1. An Orbscan printout of the patient's eye.

Choices and Outcome

The patient was counseled on the various risks, benefits and alternatives to cataract surgery to include some key issues to his case. First, if corrected to plano, he would have significant ani-sometropia and probably would not tolerate eyeglasses. Second, his astigmatism was out of the range of the available toric lenses in the United States and we would not be able to correct his astigmatism completely with an IOL alone, thus LRIs would have to be employed. Finally, his corneal thickness would prohibit a refractive touch-up should we have any residual correction and also prohibit balancing of the left eye to correct the anisometropia.

We discussed the following options: 1) Leaving the eye myopic to avoid anisometropia and using eyeglasses after surgery. 2) Attempting to correct to plano OD and wearing a contact OS, but still requiring reading spectacles 3) Correcting to plano OD and proceeding with a clear lens exchange OS, and still needing reading spectacles. 4) LRIs at a later date in the operative eye 5) LRIs in the fellow eye (OS) to reduce the anisometropia.

The patient chose to correct to plano and wear a contact lens in the left eye, with the option of doing a clear lens exchange in the future.

The patient was fit for a soft toric lens in the left eye and given a 3-week trial to ensure he could tolerate the lens. He did very well and surgery was scheduled. I chose to do LRIs at the time of surgery based on anticipated residual corneal astigmatism. The lens chosen was an Alcon 18.0 D SN6AT5 (3.00 CYL). This lens would leave the patient with 1.84 D of residual corneal cylinder, so I chose to do paired LRIs of 65 degrees to fully correct his astigmatism (Figures 2, 3).

Figure 2. The AcrySof Toric IOL calculator helps estimate the amount of post-operative corneal astigmatism to be corrected.

Figure 3. The LRI calculator assists in preop planning of limbal relaxing incisions.

The patient tolerated the surgery well and had no complications. The toric IOL was within 3 degrees of the desired outcome after surgery. His 1-month exam showed a UCVA of 20/25+ with a BCVA of 20/15+ and a refraction of −0.50 + 0.25 × 030. He was tolerating the contact lens well and was very happy with the outcome. At 6 months, he showed a small myopic shift and had UCVA of 20/30 (BCVA 20/15+), UCNVA of J3, and a refraction of −1.00 + 0.25 × 030. Fortunately, he likes the change and was able to use the slight myopia for monovision, using his right eye for near and left eye for distance. nMD

Dr. Blair is a captain with the United States Air Force. He is part of Ophthalmology Services, Mike O'Callaghan Federal Hospital, Nellis AFB, Nev.