consu l ta t i on sec t ion

refractive surgical problem edited by Thomas Kohnen, MD

A 31-year-old healthy woman had bilateral laser in situ kerato- quite small and decentered upward on both sides. Wave-

front analysis (Zywave�, Bausch & Lomb) was also performedmileusis (LASIK) 10 months ago. According to the patient’s

(Figure 3).file, the preoperative refraction was approximately �5.75

Please explain the most probable reason for this unusual�0.50 � 175 in the right eye and �5.25 �0.75 � 175 in the

appearance after LASIK. How would you treat this case?left eye. The best corrected visual acuity (BCVA) was 20/20 to

20/16 and the scotopic pupil diameter (Colvard pupillometer),

5.0 mm in both eyes. Pachymetry by topography (Orbscan,

Bausch & Lomb) showed a central thickness of 524 �m in� This patient’s UCVA is worse than in the initialthe right eye and 528 �m in the left eye. The LASIK procedure,postoperative period, and she has developed symptomsperformed with a Technolas� 217 excimer laser (Bausch &of glare, halos, and double vision. These complaintsLomb), was uneventful other than the patient reporting a pain-and the topographic findings are consistent with a diag-ful sensation during the microkeratome cut, made with a Han-nosis of post-LASIK corneal ectasia. Although there aresatome� (Bausch & Lomb) (8.5 mm suction plate, flapno anterior corneal topographic signs of keratoconus,thickness 160 �m). The optical zone was 6.2 mm in the rightthe Orbscan posterior float is less than 0.05 �m, whicheye and 6.3 mm in the left eye. The ablation depth was 116 �mis representative of subclinical keratoconus,1 and thereand 118 �m, respectively.is mild corneal inferior–superior asymmetry.During the first 5 weeks after the treatment, the uncor-

Reported risk factors for postoperative corneal ecta-rected visual acuity (UCVA) was 20/16 in both eyes and thesia are a residual stromal bed of less than 250 �m, highpatient reported being satisfied with the refractive outcome.myopia, and preoperative subclinical keratoconus.2 TheIn the following weeks, the UCVA worsened in both eyes andpatient did not have high myopia, but the preoperativethe patient started to notice double vision.

Ten months after LASIK, the patient comes to you for a

consultation. She reports a loss in visual acuity and contrast

sensitivity compared to preoperatively as well as double vision,

glare, and halos, particularly in the dark and in the left eye.

To better explain her complaints, the patient designed images

portraying her visual problems (Figure 1).

The UCVA is 20/50 in the right eye and 20/25 in the

left eye and the BCVA, 20/16 with �1.00 �0.50 � 0 and

20/20 with �0.25 �0.25 � 10, respectively; the cycloplegic

data are similar between eyes. The scotopic pupil size

(0.07 lux, Procyon digital infrared pupillometry) is 6.92 mm in

the right eye and 7.38 mm in the left eye. The low mesopic

pupil size (0.88 lux) is 5.81 mm and 6.41 mm, respectively,

and the high mesopic pupil size (6.61 lux) is 3.97 mm and

4.35 mm, respectively. Ultrasound pachymetry shows a thick-

ness of 447 �m in the right eye and 435 �m in the left

eye. Topographic images are shown in Figure 2. Slitlamp

examination revealed a healthy cornea with a well-adapted Figure 1. (Kohnen) Images describing double vision, contrast sen-sitivity, glare, and halos as seen by the patient.flap and clear interface, although the flap appeared to be

2004 ASCRS and ESCRSPublished by Elsevier Inc.

CONSULTATION SECTION

Figure 2. (Kohnen) Corneal topog-raphy image (Orbscan, quad map) 10months after LASIK. Top: Right eye.Bottom: Left eye.

Figure 3. (Kohnen) Wavefront analysis at 6.0 mm with a maximally dilated pupil 10 months after LASIK. Left: Right eye. Right: Left eye.

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Referencesestimated residual bed thickness was 248 �m in the1. Arntz A, Duran JA, Pijoan JI. Diagnostico del querato-right eye and 250 �m in the left eye. At the 10-month

cono subclinico por topografıa de elevacion. Arch Soc Espexamination, the central corneal thickness measure-Oftalmol 2003; 78:659–664ments corresponded to within �6 �m of those estima-

2. Randleman JB, Russell B, Ward MA, et al. Risk factorstions. Although a residual stromal bed thickness of less and prognosis for corneal ectasia after LASIK. Ophthal-than 250 �m cannot explain more than 50% of cases mology 2003; 110:267–275of post-LASIK corneal ectasia,3 in my experience, a 3. Ou RJ, Shaw EL, Glasgow BJ. Keratectasia after laser

in situ keratomileusis (LASIK): evaluation of the calcu-residual stromal bed limit of 300 �m may be morelated residual stromal bed thickness. Am J Ophthalmolsuitable to allow for margins of error in pachymetry2002; 134:771–773readings, achieved flap thickness, and laser performance.

4. Schallhorn SC, Kaupp SE, Tanzer DJ, et al. Pupil sizeIn the present case, one may fall into the trap ofand quality of vision after LASIK. Ophthalmology 2003;

assuming the night-vision problems are related to a110:1606–1614

scotopic pupil size exceeding the optical zone size, par- 5. Pop M, Payette Y. Risk factors for night vision complaintsticularly in the left eye, in which the problems are most after LASIK for myopia. Ophthalmology 2004; 111:3–10bothersome. Long-term studies, however, show that 6. Moreno-Barriuso E, Lloves JM, Marcos S, et al. Ocular

aberrations before and after myopic corneal refractive sur-scotopic pupil size is not predictive of night-vision com-gery: LASIK-induced changes measured with laser rayplaints, whereas higher target spherical correction istracing. Invest Ophthalmol Vis Sci 2001; 42:1396–1403a major risk factor.4,5 The latter relationship may be

7. Chalita MG, Chavala S, Xu M, Krueger RR. Wavefrontexplained by an increased risk for amplification of high-analysis in post-LASIK eyes and its correlation with visualorder aberrations after LASIK for higher amounts ofsymptoms, refraction and topography. Ophthalmology

myopia.62004; 111:447–453

High postoperative high-order aberrations are the 8. McDonald JE II, El-Moatassem Kotb AM, Decker BB.likely cause of this patient’s visual symptoms. The total Effect of brimonidine tartrate ophthalmic solution 0.2%

on pupil size in normal eyes under different luminancehigh-order aberrations, which are approximately 0.7 �mconditions. J Cataract Refract Surg 2001; 27:560–564in each eye, may be explained by the posterior float

9. Budo C, Hessloehl JC, Izak M, et al. Multicenter studyelevation or the topographic inferior–superior anteriorof the Artisan phakic intraocular lens. J Cataract Refractasymmetry, although the specific role of each compo-Surg 2000; 26:1163–1171nent is impossible to establish. Total high-order aberra-

tions increase with increasing pupil size, accounting forthe worsening of visual symptoms in the dark, and

� Regarding the preoperative workup, the scotopicdouble vision is more bothersome in the left eye, consis-pupil diameter determined by the Colvard pupillometertent with its relatively higher amount of coma. A recentis meaningless as subsequent infrared pupillometryreport indicates that double vision may be better ex-proved larger pupil sizes. The patient had an opticalplained by coma itself than by high-order aberrations.7

zone of 6.2 mm in the right eye and 6.3 mm in theContinued follow-up is necessary to establishleft eye. With a refraction of approximately �6.0 diop-whether this patient will develop clinical keratoconus.

Meanwhile, brimonidine tartrate 0.2% (Alphagan�) ters (D) in both eyes, this is likely to give rise to a smallcan be prescribed to control pupil dilation at night and effective optical zone. If decentered in the presence ofthus alleviate some of the symptoms.8 large low mesopic or scotopic pupils, it could give rise

This case is a reminder that stringent residual bed to symptoms. However, it is interesting that during thecalculation, incorporating a margin for operative errors first few weeks after treatment, UCVA was excellentand possible retreatment, is an essential element in and the patient was very happy; however, with theLASIK screening. When the residual bed limit is healing process, the situation changed. Ten monthscrossed, the risk for complications increases. Phakic later, the patient reports a loss in visual acuity andintraocular lens implantation may be more suitable in contrast with symptoms of diplopia, glare, and halos,these cases.9

particularly night-vision disturbances. There is a defocuserror, particularly in the right eye, but the distanceMIHAI POP, MD

Montreal, Quebec, Canada acuity inevitably is reduced to 20/50. The left eye has

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