Article

The eighth cut is the deepest

Cataract surgery in post-radial keratotomy eyes.

Our patient was a 78-year-old male who presented to our clinic for cataract evaluation. He had a history of bilateral dry eye, mild-moderate primary open-angle glaucoma on timolol, latanoprost and dorzolamide as well as bilateral radial keratotomy performed in the 1980s. He complained of mild glare symptoms with night driving. His medical problems were gastroesophageal reflux disease and atrial fibrillation with a pacemaker in place.

INITIAL FINDINGS

The ocular exam

Our examination demonstrated the following:

  • Distance visual acuity (VA) with correction: 20/60- OD, 20/30- OS
  • Low contrast VA (10%): 20/80 OD, 20/60-2 OS
  • Manifest refraction (Mrx):
    • +2.50 -2.50 x090; 20/40- OD
    • +1.50 -1.25 x090; 20/30- OS
  • Pupils: reactive without afferent pupillary defect
  • IOP (applanation): 11 mm Hg OD, 10 mm Hg OS

Slit lamp examination showed severe corneal punctate epithelial erosions inferiorly OU with no erosions in the central visual axis, along with 8-cut RK scars OD and 16-cut RK scars OS. His lens demonstrated 2+ nuclear sclerosis with central posterior subcapsular changes OD>OS.

The patient’s cup-to-disc ratio was 0.75 OD and 0.50 OS with full rims OU. His exam was otherwise unremarkable.

Relevant preoperative surgical measurements obtained from optical biometry (IOLMaster 500, Carl Zeiss Meditec AG) were as follows:

  • Axial length: 25.04 mm OD, 24.76 mm OS
  • Keratometry:
    • OD: 41.01 @081, 44.18 @171
    • OS: 42.19 @080, 44.58 @170
  • Anterior chamber depth: 3.52 mm OD, 3.45 mm OS
  • Corneal topography (Atlas System Model 900, Carl Zeiss Meditec AG)
  • Severe against-the-rule astigmatism with inferior flattening OD (Figure 1)

Figure 1. Atlas photos of cornea OD taken at preoperative visit.

We planned for cataract extraction with IOL implantation (CEIOL), OD first. With eight-cut RK scars OD, we believed there was enough room between the RK incisions to construct the main wound via a clear corneal incision. We selected a 19.0 D PCB00 (TECNIS, Johnson & Johnson Vision).

THE CHALLENGES BEGIN

Intraoperative obstacles

On the day of surgery, standard phacoemulsification via clear-corneal incision was started as planned. During creation of the main wound, a clear corneal tunnel made with a 2.4-mm keratome was slightly longer than intended, and the superior portion of the tunnel came very close to superior adjacent RK wound. As the case progressed, the stress of surgery on the wound threatened to open the wound towards the RK scar; given the concern for wound-RK scar intersection with resultant wound gape, a 10-0 nylon suture was placed to incorporate the main wound and the abutting superior RK incision for stability following phacoemulsification and cortical material removal.

The rest of the case proceeded without complications and the J&J PCB00 lens was placed as intended.

Postoperative problems

At the postoperative day-one (POD1) visit, uncorrected VA (UCVA) OD was 20/40- and IOP OD was 20 mm Hg. The corneal exam was remarkable for edema at the main incision, which was Seidel negative, with the nylon suture incorporating the main wound and proximal superior RK incision. A 2+ cell was present in the anterior chamber (AC), and the lens was in a good position. The patient was started on routine postoperative drops.

At the patient’s POD7 appointment, his UCVA OD was 20/20-2 and IOP 22 mm Hg. His corneal exam was stable with rare AC cell, and the lens was in good position. His postoperative drops were tapered, and he was instructed to resume his preoperative glaucoma drops.

However, the patient’s postoperative course was later complicated by rebound iritis, diagnosed at postoperative month one (POM1); steroids were restarted and slowly tapered. His temporal nylon suture was removed. His second eye underwent uncomplicated cataract extraction with IOL insertion via scleral tunnel.

At his POM1 appointment following CEIOL OS, his corneal exam was remarkable for tear film irregularity OD>OS, with his final BCVA as follows:

  • OD: -1.25 -0.75 x080; 20/30+
  • OS: -1.00 -0.75 x090; 20/20

We informed the patient that his final VA may be limited due to corneal irregularity, for which he may benefit from a therapeutic hard contact lens (CTL) trial if not satisfied with glasses. He subsequently moved out-of-state and transferred his ophthalmic care elsewhere.

CATARACT SURGERY IN POST-RK EYES

Radial keratotomy in perspective

A now largely-abandoned refractive procedure aimed at correcting low to moderate myopia, radial keratotomy (RK) was first described in Europe in the 1800s and evolved into its modern form in 1960s Russia, with the first case done in the United States in 1978. Peaking in the 1980s and 1990s, RK consisted of creating multiple incisions into the cornea at 90% depth, with the total number of incisions varying, depending on surgeon technique and preference.1

The Prospect Evaluation of Radial Keratotomy (PERK) Study, a landmark publication, revealed the long-term complications and results of RK, specifically the progressive hyperopic shift seen over the 10-year study period due to corneal flattening.2 This, in conjunction with the development of LASIK and PRK, led to the decline of RK. With the aging of the post-RK population, more and more of these patients are now presenting for cataract evaluation.

Challenges and solutions

Preoperative approaches and considerations involve slit lamp exams, measurements and lens selection. In the clinical approach to a post-RK patient seeking cataract surgery, take care to obtain a thorough patient history, including glasses use, stability of refraction, fluctuations in vision and hard or soft CTL use. A careful slit lamp exam is of paramount importance, noting the total number of RK cuts, presence of transverse cuts and ocular surface quality.

Lastly, obtaining MRx, high-quality IOL calculations with K readings as well as corneal topography is a must.

In surgical planning, it is critical to understand that the use of standard IOL calculations using IOL Master Ks and topography may result in unintended hyperopia due to overestimation of true corneal power.3 The standard of care is to use one of a variety of formulas designed to help calculate IOL power in post-RK eyes, such as the Barrett True-K or Atlas 1-4, that averages the central powers.4

One useful resource is the ASCRS calculator (http://iolcalc.ascrs.org ). It incorporates data from the IOLMaster and topography, as well as refraction data pre- or post-RK, if available. This was the formula we used in our patient.

While monofocal lenses are often employed in post-radial keratotomy eyes, successful implantation of customized multifocal and extended depth of focus (EDOF) lenses have been reported with satisfactory visual results.5-8 Prior to selection of such lenses, however, the ophthalmologist should be sure to obtain accurate, reproducible topographical measurements, as well as counsel the patient on the associated risks of glare and halos, which can occur due to increased higher-order aberrations.9

Intraoperative course: Potential complications and workarounds

Cataract surgeons may encounter numerous challenges in post-RK patients, including wound gape and poor visualization, which can occur especially if the main wound is too long.

Tips for managing these challenges include the following:

  • Maximizing the red reflex by optimizing operative microscope luminance
  • Having a low threshold for constructing a scleral tunnel, as opposed to making a clear corneal incision
  • Preemptively placing a suture at the RK adjacent to the main wound
  • Avoiding wound torque at all steps
  • Watching the AC depth, as fluctuations can result in sudden wound gaping or rupture.

During nuclear disassembly, tools such as the Akahoshi prechopper minimize corneal stress. One can also adjust the machine settings (eg, lowering the infusion pressure, raising the vacuum). Bimanual phaco can also be utilized to decrease wound size, although this wound must often be widened or a third wound made for IOL insertion.1

Finally, placing a bandage CTL at the end of the case, especially if a suture is placed, can reduce patient discomfort in the immediate postoperative period.

Postoperative period: Patience is key

Postoperatively, the surgeon should expect a certain degree of MRx fluctuation, not only over days and weeks, but also diurnally that can occur all the way to the limbus due to transient hyperopia from edema around the RK incisions. This can be managed best with a rigid gas permeable lens or keratoplasty. One can also expect a gradual myopic shift as the corneal edema resolves over the subsequent weeks postoperatively.

A rarely reported postoperative complication is delayed RK wound dehiscence, which may require a return trip to the OR.10

THE TAKE-AWAY PEARLS

The post-RK patient who desires cataract surgery demands a methodical approach. Give special attention to the slit lamp exam (eg, number of RK cuts), as well as surgical planning — namely main wound construction (clear corneal vs. scleral tunnel) and IOL selection. Also critical is familiarity with the multitude of possible intraoperative complications as well as the tools that can address these complications.

Lastly, the ophthalmologist should take care to counsel the patient on the prolonged postoperative course, specifically the time needed for refractive stabilization and the possibility of requiring therapeutic CTL to minimize corneal irregularity and optimize vision. OM

REFERENCES

  1. Meduri A, Urso M, Signorino GA, et al. Cataract surgery on post radial keratotomy patients. Int J Ophthalmo. 2017;10:1168-1170.
  2. Waring GO III, Lynn MJ, McDonnell PJ. Results of the prospective evaluation of radial keratotomy (PERK) study 10 years after surgery. Arch Ophthalmol. 1994;112:1298-1308.
  3. Radial Keratotomy: Determining true corneal power after radial keratotomy. East Valley Ophthalmology. https://www.doctor-hill.com/iol-main/postRK.htm . Accessed Sept. 25, 2019.
  4. Chen L, Mannis M, Salz JJ, Garcia-Ferrer FJ, Ge J. Analysis of intraocular lens power calculation in post-radial keratotomy eyes. J Cataract Refract Surg. 2003;29:65-70.
  5. Nuzzi R, Monteu F, Tridico F. Implantation of a multifocal toric intraocular lens after radial keratotomy and cross-linking with hyperopia and astigmatism residues: a case report. Case Rep Ophthalmol. 2017;8:440-445.
  6. Kim KH, Seok KW, Kim WS. Multifocal intraocular lens results in correcting presbyopia in eyes following radial keratotomy. Eye Contact Lens. 2017;43:e22-e25.
  7. Gupta I, Oakey Z, Ahemd F, Ambati BK. Spectacle independence after cataract extraction in post-radial keratotomy patients using hybrid monovision with ReSTOR multifocal and TECNIS monofocal intraocular lenses. Case Report Ophthal. 2014;5:157-161.
  8. Baartman B, Karpuk K, Eichhorn B, et al. Extended depth of focus lens implantation after radial keratotomy. Clin Ophthalmol. 2019;13:1401-1408.
  9. Patel R, Karp CL, Yoo SH, Amescua G, Galor A. Cataract surgery after refractive surgery. Int Ophthalmol Clin. 2016;56:171-182.
  10. Day A, Seward H. Delayed radial keratotomy dehiscence following uneventful phacoemulsification cataract surgery. Eye. 2007;21:886-887.

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