sign in sign up
<<
Home , Astigmatism, Keratoconus, Visual acuity

& REFRACTIVE

Comparing refractive outcomes in Study demonsrates the importance in considering all options in managing keratoconus

By Dr Guillermo Rocha, eratoconus is a condition that affects 1 in Over the course of the past few years, there MD, FRCSC K2000 individuals. It results in thinning and has been a paradigm shift in the management of steepening of the and this leads, in turn, keratoconus. Mild cases may still be managed to irregular , increased coma (high with and contact ; however, order aberration) and decreased quality of vision. corneal crosslinking (CXL) has become Associated systemic conditions may include atopic an important aspect in the management of these disease and rubbing. cases. In the management of keratoconus, it is In fact, in mild and moderate cases CXL has been important to consider a practical and functional proven to arrest the condition. can classification of keratoconus, because based on be further improved in mild cases with phakic or this a treatment approach will be generated. It is pseudophakic toric intraocular implants. also important to consider the goal that is being For moderate cases, an attempt is made to achieved in the management of these patients. improve the BCVA, either by modifying the shape of In general, I tend to classify keratoconus as mild, the cornea with intracorneal ring segments, or by moderate, or severe. In terms of practical aspects, reshaping the surface of the cornea with excimer mild and moderate keratoconus have central laser procedures. In addition, the management pachymetry readings greater than or equal to (> or of severe cases has evolved towards using not = to) 400 microns and keratometry readings less only penetrating but also deep anterior lamellar than or equal to (< or = to) 55 dioptres (D); however, keratoplasty techniques. severe cases of keratoconus have corneal thickness The treatment approach is based on the specific lower than 400 microns and steepening greater goals. One needs to prevent rubbing to continue than 55 D. with the mechanical insult to the cornea, stop Clinically, mild keratoconus often presents as progression, strengthen the cornea, change the form fruste keratoconus or subclinical keratoconus, shape, improve the best-corrected visual acuity and it may present in young individuals or be suspected distortion, as well as improving the uncorrected in an eye which has more advanced keratoconus visual acuity by reducing irregular astigmatism. in the contralateral eye; and it may also end up Based on this, we have developed a treatment progressing over time. algorithm over the past several years, which is Moderate keratoconus begins to show contact summarized in Table 1. It shows the most common lens intolerance, may still have good best-corrected techniques that are used to date, including CXL, visual acuity (BCVA) but employment issues begin to be an important aspect. Finally, severe keratoconus is characterized by apical scarring, marked thinning and poor BCVA, all in the face of continued progression. In short... Keratoconus results in the thinning and steepening of the cornea, leading to irregular astigmatism, increased coma Evolution of treatment and decreased quality of vision. Previously, observation In the past, observation was the only treatment was the only treatment offered for mild to moderate forms of keratoconus, with penetrating keratoplasty being offered for mild and moderate keratoconus. considered when the progressed to the severe Patients were instructed to wear glasses or form. In this article, Dr Rocha discusses the evolution of contact lenses until such a time that the condition keratoconus treatment and management as well as the progressed to the severe form. At that time, one results of a comparative study, which revealed that all options should be considered in managing keratoconus would consider penetrating keratoplasty as the only patients. treatment option.

2 Times Europe Jan/Feb 2013 CATARACT & REFRACTIVE

intracorneal ring segments (ICRS), excimer laser as well as intraocular Table 1: G Rocha lens (IOL) implants. Technique Stop Strengthen Change Improve VA UCVA target These are aimed, in various ways progression cornea shape & distortion astigmatism and combinations, at stopping CXL ✔ ✔ ✔ ✔ progression, strengthening the ICRS ✔ ✔ ✔ ✔ cornea, changing the shape of the cornea, improving visual acuity and PTK / Excimer ✔ ✔ ✔ distortion and reducing astigmatism. T-ICL ✔ ✔ Based on this, Figures 1 and 2 show T-IOL ✔ ✔ clinical examples of keratoconus and post-LASIK ectasia treated with Intacs alone, or in combination with was central or inferiorly located CXL, respectively. (i.e., eccentric). Figure 1: OS 60 yo M: Intacs, CL difficulty 2. To determine the manifest Comparative study and allow the patient PreOp UCVA Sphere Cyl Axis BCVA We recently compared the visual to select the axis by rotating the 20/50 -2.00 +1.25 60 20/50 and refractive outcomes following axis knob on the . This What was done? Intacs (Addition Technology provides an exquisite precision Intacs Inferior .300 Inc., Sunnyvale, California, USA) to the axis of the astigmatism. implantation in keratoconus , 3. Use the nomogram to select but were particularly interested the thickness of the size of the in analysing the results between Intacs segment. central and eccentric cones.1 The 4. Decide on one or two segments PostOp basis for using intracorneal ring and consider symmetric versus UCVA Sphere Cyl Axis BCVA 20/30 segments was to strengthen the asymmetric implantation based cornea, as the Intacs provide an on the nomogram. additive effect in the periphery, to In this retrospective study we change the shape by flattening the included 20 patients who had Figure 2: OS 50 yo M: Post LASIK ectasia central cornea and reducing the symmetric (15 eyes) or asymmetric amount of astigmatism, to improve (16 eyes) implants. Intacs were PreOp visual acuity and distortion, and implanted by a single surgeon UCVA Sphere Cyl Axis BCVA to address the astigmatism by (G.R.) and the surgical technique 20/60 -1.00 +2.25 165 20/20 PreOp PostOp improving uncorrected visual acuity. included creating the channels with What was done? We, therefore, compared the an Intralase FS (Abbott Medical Intacs Inferior . visual and refractive outcomes Inc., Santa Ana, California, 350 + in keratoconus eyes between USA) with the following parameters: CXL central cones implanted with depth of the channel 400 microns, symmetric segments versus internal diameter 6.8 mm, external PostOp eccentric cones implanted with diameter 7.8 mm. UCVA Sphere Cyl Axis BCVA asymmetric segments. Our intention The incision axis was determined 20/20 Plano 20/20 was to also validate the current by the preoperative manifest planning nomogram provided refraction axis. We assessed by the manufacturer. There is a uncorrected and corrected distance and asymmetric implantation large amount of evidence, which visual acuity, manifest refraction for uncorrected distance vision, supports the use of ICRS, Intacs, in spherical equivalent (MRSE), MRSE, average K-reading or corneal keratoconus and pellucid marginal refractive cylinder and average astigmatism. With the exception of degeneration. K-readings. corrected distance visual acuity, Our approach consisted of four In corrected distance visual which was statistically significantly steps: acuity, asymmetric Intacs showed better in the asymmetric group, 1. To identify the cone on an statistically significant better both approaches showed a marked elevation map (Pentacam, results than symmetric implantation improvement in keratoconus eyes. OCULUS GmbH, Wetzlar, (p = 0.0016), however, there was no We also were able to validate Germany). In this way, we statistically significant difference the pre‑surgical planning guide determined whether the cone between the means of symmetric recommended by the manufacturer.

3 www.oteurope.com/cat_ref CATARACT & REFRACTIVE

Conclusion In conclusion, it is important to consider all the different options in managing keratoconus patients. Intacs are one of the options available. At this point we are combining, on a regular basis, Intacs with CXL, CXL with excimer laser and/or Intacs, and any of these combinations with intraocular correction of astigmatism using toric IOLs.

Reference 1. M. Kapasi and G. Rocha, Can. J. Ophthalmol., 2012;47:354–359.

What management practices do you

perform? www.oteurope.com/discuss

Author Dr Guillermo Rocha, MD, FRCSC, is medical director, GRMC Vision Centre; assistant professor, University of Manitoba, Brandon, Manitoba, Canada. He may be reached by E‑mail: [email protected] Dr Rocha has no proprietary or financial interests in any aspect of this manuscript

4 Ophthalmology Times Europe Jan/Feb 2013