6
Case reports
Sunil Shah, Stephen J Doyle and Paul Cherry
In this chapter we look at various interesting and complicated patient outcomes from refractive surgery. We begin, however, with a brief guide to the video clips on the CD that accompanies this book.
Videos on CD
Video 1 – Orbscan
Video 1 (courtesy of Bausch and Lomb) shows the two scanning slits of the Orbscan anterior segment analysis unit in operation. In real time each scan takes 0.7 seconds. The scans are also combined with Placido information.
Video 2 – Superior flap
Video 2 (courtesy of Bausch and Lomb) shows the Bausch and Lomb Hansatome microkeratome cutting a corneal flap in a laser in-situ keratomileusis (LASIK) procedure. This is a two-piece microkeratome and the cutting device can be seen being placed onto the base plate. Note that the flap is hinged superiorly (seen from the surgeon’s
persepctive), which some surgeons argue is better for the healing of the cornea, although others suggest that a nasal hinge leads to less corneal nerve disturbance.
Video 3 – Amadeus
Video 3 (courtesy of AMO) shows the Amadeus one-piece microkeratome by Advanced Medical Optics (AMO). Note that the corneal flap is hinged nasally and that the flap thickness in this particular case is slightly thicker than that in Video 2.
Video 4 – Laser subepithelial keratectomy
Video 4 starts with the alcohol well in place filled with a low percentage ethanol solution. This is absorbed with a Merocel surgical spear. The cornea is washed and dried and the surgeon (Sunil Shah) then breaks the epithelium. The epithelium is moved away from the central area and the excimer laser beam is applied to Bowman’s membrane to create the new corneal profile, in accordance with the refractive error. The epithelium is
replaced. Note that the epithelium does not lift in one thick slice, but rather a thin sheet is kept intact and removed and subsequently repositioned. The thickness of the epithelium is around 50μm, as opposed to a LASIK flap of around 160μm.
Video 5 – WAVE CL system
Video 5 (courtesy of Northern Lenses) shows the Keratron SCOUT topography unit, from Carlton Ophthalmic. This portable device can be handheld, table mounted or slit-lamp mounted. The system is based on a Placido cone and able to use its radius of curvature data from the anterior cornea to design a gas permeable contact lens for that particular cornea. The data are used by Northern Lenses in their WAVE system contact lenses. This system is particularly useful when a corneal lens is required for an irregular corneal profile.
Flap transaction
•Corneal consultant, Sunil Shah;
•Urgent patient referral to hospital corneal consultant;
•0/–1.5 refraction in affected eye, –2D in other eye;
•Age 55 years, male.
The patient had planned to have surgery on the left eye (LE) only, but on the day of surgery (when he saw the surgeon at the
50 ■ Refractive surgery: a guide to assessment and management
high-street clinic for the first time), he was persuaded to have surgery on the right eye (RE) also. What persuaded the patient to have surgery in the RE also is unclear, as he stated that he could read reasonably well with the RE and his personal thinking previously had been that he could always have the RE treated at a later date.
The Hansatome was apparently normal (nothing unusual with the K-readings, corneal topography or corneal examination), as no abnormality was noted by the surgeon or scrub nurse. The pressure readings were good. The LE was not treated.
When the microkeratome was removed and the flap lifted, there was a horizontal transaction of the flap (superior hinge with half of the flap attached), a 9 o’clock to 3 o’clock cut through the flap, with that portion being a free flap.
Figure 6.1
Superior portion of flap in situ, with an epithelial and stromal deficit inferiorly
The inferior free-flap portion could not be found on the eye or on the microkeratome. Examination of the blade was unremarkable. No abnormality could be found in the microkeratome set up.
The patient was seen urgently by the ophthalmological consultant at the hospital that evening. Obviously extremely anxious, he had been speaking to his solicitor in the car while being transferred from the clinic.
Examination confirmed the superior portion of the flap in situ, with an epithelial and stromal deficit inferiorly (Figure 6.1). Options were discussed with patient and conservative management suggested for the time being. He was started on guttae hyaluronic acid 0.18% hourly, ocular liquid paraffin six times daily, and both chloramphenicol and dexamethasone four times daily.
The patient was reviewed at 1 day, 1 week, 1 month and 3 months post-incident:
•1 day review: no significant change, with little epithelial healing.
•1 week review: full epithelial healing, and the epithelium looked quite healthy. There was a clear stromal deficit. Retinoscopy confirmed a mild myopic astigmatism in the superior portion and high hyperopia in the lower portion.
•1 month review: epithelium had filled in the stromal deficit completely, with refraction now stable across whole cornea at pre-surgery levels.
•3 month review: stable, no haze and best-corrected visual acuity (BCVA) back to 6/5 (Figure 6.2).
Figure 6.2
Patient in Figure 6.1 at 3 month review: stable, no haze, BCVA back to 6/5
Epithelial remodelling following laser subepithelial keratectomy that caused an increase in prescription
A patient persuaded the surgeon (Sunil Shah) to perform laser subepithelial keratectomy (LASEK) on her. She was very eager to have surgery as a number of her family members had previously undergone successful refractive surgery by the same surgeon. Initially, surgery was refused as the prescription was very mild (0/–1.5D × 115 and 0/–1.5D × 80) with an unaided visual acuity (VA) of 6/12 in each eye, improving to 6/9 binocularly unaided.
The prospective patient was adamant that she wanted refractive surgery and clearly stated that she was aware that she may gain little benefit from laser refractive surgery, but she wanted to take the chance. She was particularly aware that there was very little risk from LASEK for this sort of prescription and agreed that LASIK was an unnecessary risk in her case.
Surgery was uneventful using the butterfly LASEK technique. Recovery was unremarkable in that the epithelial healing occurred within 3 days. A review appointment was given for 1 week. She telephoned a few days later and said she felt that her uncorrected visual acuity (UCVA) was worse than it had been before surgery and she had returned to wearing her glasses.
At the 2 week review, her refraction was –1/–1 × 90 and –0.75/–1.25 × 65. This refraction was maintained over the next 3 months (subjective and objective), which was presumed to result from epithelial hyperplasia, and it played a significant role as the original prescription was so small.
Bilateral flap infection masquerading as diffuse lamellar keratitis
The patient underwent routine uncomplicated LASIK in a full ophthalmic operating theatre (not just a clean laser room). The surgery (Sunil Shah) was uncomplicated, in the middle of a laser list and all the other patients were uncomplicated. Review at 1 day was unremarkable, with UCVA 6/9 in each eye.
An urgent review was carried out at 4 days, as the patient was worried. UCVA was 6/60 RE and 6/24 LE. The appearance was of grade 1 diffuse lamellar keratitis (DLK) with some small focal opacities in the RE only. The patient was asked to continue topical chloramphenicol four times daily, and
to increase the prednisolone acetate 1% from four times a day to hourly in each eye.
On review 1 day later (at 5 days), the DLK had substantially resolved, but one focal abnormality in the RE was unchanged and the LE had multiple tiny focal abnormalities that appeared to be settling. UCVA had not improved and the treatment was continued. The eyes remained white throughout.
On review 2 days later (at 7 days), the UCVA was unchanged. The RE focal abnormality was larger in size and had slightly fluffy edges, the LE focal abnormalities were unchanged and there was no further evidence of DLK. A diagnosis of bilateral flap infection was made. Treatment was changed to prednisolone acetate 1% four times daily, chloramphenicol once an hour and ofloxacin once an hour.
On review 1 day later (at 8 days), there was no deterioration, but no improvement, in the LE; in the RE, the size was unchanged, but there were satellite lesions around the original lesion. A decision was made to collect samples from the RE with a flap washout and a corneal scrape. The LE was felt safe to leave. The RE flap was lifted and a corneal scrape performed.The opacity was not impressive in terms of infection: it felt like a string of mucus. There was no corneal melt around the opacity. A washout was then performed.
Urgent microscopy revealed a staphylococcus as the probable organism. The treatment was felt to be adequate and therefore continued. Culture of the organism confirmed Staphylococcus aureus, sensitive to both chloramphenicol and ofloxacin. It is worth noting that a typical DLK is probably an infection and an indication for an early flap lift.
Slow resolution followed and left some minor stromal scarring.
Refraction improved from –1.5/–2 × 90 RE and –1.25/–0.5 × 110 at 2 weeks to 0.75/–0.5 × 90 and –0.75/–0.25 × 100 at 3 months. BCVA was initially 6/20 in the RE, which improved to 6/7.5 at 3 months, but it remained at 6/5 in the LE throughout.
Flap melt after treatment for epithelial ingrowth
The patient was referred from a ‘highstreet clinic’ to local corneal consultant (Sunil Shah). Apparently an uncomplicated LASIK originally, but recurrent epithelial ingrowth had been treated twice already. Further recurrence occurred with poor BCVA.
Examination revealed 30% epithelial ingrowth that encroached on the visual axis. Pre-operative refraction was –3DS,
Corneal anatomy, physiology and response to wounding ■ 51
and the refraction on presentation to the corneal consultant was +3/–2 × 85. The other eye was UCVA 6/5, but for the ingrowth eye BCVA was 6/15.
At surgery, the flap was lifted very easily. A notch in the flap found in an area of ingrowth was assumed to be the cause of the ingrowth.
Flap and base were cleaned and treated gently with absolute ethanol and then copious irrigation. It was decided not to suture the flap at this stage as, despite the notch, the flap was sitting nicely and the extent of the original treatment was unclear because the original treating doctor was no longer in the country and records were sketchy.
Recovery was unremarkable. UCVA improved to 6/12 and BCVA to 6/6, with +0.75/+0.75 × 180.
Over the next 6 months, the peripheral flap melted in an area of previous epithelial ingrowth. The central flap was not affected visibly, but the subjective cylinder increased to 1.75D and the BCVA dropped to 6/9. The flap melt remained stable.
Therefore, a rigid contact lens was tried, which improved the BCVA to 6/5–. A cus- tom-fit contact lens was ordered, based on the topography, which gave an excellent fit and visual outcome.
LASEK in one eye with LASIK in the other eye because of unilateral von Hippel–Lindau lesion
This case is an example of both LASEK and LASIK used to give the same end result for each eye. The patient’s RE had a unilateral von Hippel–Lindau lesion (i.e., an angiomatous lesion), which was at risk of bleeding and had been treated with laser previously by a medical retina surgeon in an attempt to stabilize it.
The patient was –5D in each eye, and the risks and benefits were discussed with the surgeon (Sunil Shah). LASIK was too risky in the RE as increased intraocular pressure from the suction ring may cause the angiomatous lesion to bleed. The recommendation was to have LASEK in the RE and LASIK in the LE simultaneously.
The surgery was uncomplicated:
•1 day post-operatively, UCVA 6/12 and 6/5.
•1 week post-operatively, UCVA 6/6 and 6/5, refraction +0.5DS RE, 0 LE.
•1 month post-operatively, UCVA 6/5
and 6/5, refraction plano both eyes. The patient’s comments were that 3 days of discomfort were well worth it, there
was no significant pain and with visual recovery within 1 week she had no particular problem.
When asked whether she preferred LASIK or LASEK, she said she was petrified by the cut of LASIK and so, if she had to do it again, she would probably consider bilateral LASEK.
Keratectasia case
The patient was a 24-year-old male:
•RE: –6.25/–2.25 × 15, best-corrected spectacle visual acuity (BCSVA) 6/7.5;
•LE: –12.25/–2.0 × 15, BCSVA 6/10;
•Pupils were 6mm diameter;
•Pachymetry: RE 540 and LE 508.
LE LASIK was undertaken by the surgeon (Doyle) with the aim of only –3.25 because of the depth problems (the patient was happy with this outcome as then he could wear normal best-form glasses even if the RE was not good enough unaided). The optical zone (OZ) was 5.5mm and the treatment zone (TZ) was 7mm plus an elliptical cylinder to save depth (Nidek EC 5000). The flap was 130μm (Moria ‘one’). The predicted ablation depth was 130μm and the predicted bed was 248μm. Intraoperative pachymetry was not carried out in this case, in either eye.
After 2 weeks RE LASIK was undertaken, with 6mm OZ, 7.25mm TZ and a predicted ablation depth of 131μm (Nidek EC 5000). The flap was 160μm (Moria ‘one’), with a predicted bed of 249μm.
Post-operative pachymetry at 1 month was 400μm in both eyes, at 6 months it was RE 375μm and LE 400μm and at 1 year it was RE 385μm and LE 412μm.
Refraction at 2 months post-operative- ly was:
•RE +1/–1 × 180 (VA 6/12 unaided and 6/7.5 with glasses);
•LE –2/–1.5 × 30 (VA 6/15 unaided and 6/10 with glasses).
At 30 weeks refraction was:
•RE –1/–0.75 × 140 (VA 6/12 unaided and 6/7.5 with glasses);
•LE –3/–0.75 × 15 (VA 6/60 unaided and 6/10 with glasses).
He developed keratectasia in the RE, and serial topography showed that it started over the area of an old small scar. This scar was caused by a thorn when a child (thickness over this area post-operatively was about 475μm). Whether the scar was a relevant factor in this case is not known. What made the surgeon discount this initially was that surgeons carry out LASIK after penetrating keratoplasty, with a full-thickness 360° scar and the patients appear to have no problems. The initial topography was entirely
52 ■ Refractive surgery: a guide to assessment and management
regular and the patient had worn glasses from the age of 4 years.
It appears that the depth of the ablation and/or the flap was more than expected in the RE. The surgeon would have expected a greater likelihood of such a problem in the LE because of the initial thinness.
The patient was referred to the local University contact lens clinic for a gas permeable contact lens fitting, which was accomplished with great skill, although not without difficulty.
Late flap lift post-LASIK
The patient was first examined by the surgeon (Cherry) on 29 April 1997. He was a high myope who successfully wore disposable soft contact lenses that had last been used 2 weeks prior to the examination. Presenting glasses prescription was RE –9.00, LE –8.00. Cycloplegic refraction was RE –8.50, –0.50 × 180, 6/7–, and LE –8.00, 6/6–. Keratometry was recorded as RE 43.87, 44.12 × 86, and LE 43.62, 44.00 × 98. He elected for a monovision LASIK treatment because he was a current successful wearer of monovision contact lenses. His LE was dominant.
Treatment day was scheduled for 16 May 1997 at The Toronto Laser Sight Centre. EyeSys topography was performed prior to the procedure and showed no abnormalities. Central pachymetry was RE 584, LE 580. Bilateral, simultaneous LASIK was undertaken, using the VISX 20/20 excimer laser (software version 4.02c) and the ACS keratome, which produced 8.5mm flaps with nasal hinges. Two treatments were undertaken in each eye, in accordance with multi-zone technology. Details were as follows (corneal plane):
•RE –2.31, –0.52 × 180, zone size an ellipse 6.00mm × 5.4mm, ablation 36μm;
•RE –3.00, zone size of 6.00mm, ablation 45μm;
•LE –3.43, zone size of 6.00mm, ablation 52μm;
•LE –3.50, zone size of 6.00mm, ablation 53μm;
•The flaps were 160μm in thickness, so
stromal beds of 343μm in the RE and 315μm in the LE remained.
Follow-up was uneventful. However, on 22 September 1997, the patient expressed some dissatisfaction in that the reading distance was too close with his RE. At that time, manifest refraction was RE –3.75, 6/7– and LE plano, 6/7–. He elected to have his RE retreated, which was accomplished by relifting the flap on 3 October 1997 at The Toronto Laser Sight Centre. Topography prior to retreatment showed central treatments with no complications. Pre-enhancement pachymetry was RE 541μm, somewhat thicker than the predicted thickness of 343 + 160 = 503μm. The laser used was the Chiron Keracor 116. Treatment for the RE, was –1.58, zone size of 6.00mm and ablation 27μm to leave a theoretical stromal bed of 316μm in the RE.
He was extremely happy after the retreatment, and did not quite complete his scheduled follow-up visits, having last attended for follow-up on 17 January 1998, when the uncorrected distance vision was RE 6/60, LE 6/9+. Manifest refraction was RE –1.50, –0.50 × 180, and he was delighted with the reading distance that this remaining myopia produced.
His opinion about monovision slowly changed, however. When he finally came back for a further examination on 27 November 2001, he was still happy with both his reading and distance vision, but was considering having the RE enhanced for distance in Arizona, where he was planning to go to escape the Canadian winter! At that time, cycloplegic refraction was LE +1.50, –0.50 × 90, 6/7 but, despite this overcorrection, he had no problems with distance vision.
He returned for re-examination on 28 November 2002, having not had any surgery in Arizona. Uncorrected distance vision was LE 6/12–. He was still happy with both his distance and reading vision, but now expressed a definite wish to rid himself of monovision and, further, to have the procedure done in Toronto. Keratometry was RE 39.37, 39.25 × 98. Cycloplegic refraction was RE –1.50, 6/7–.
RE enhancement was performed at the Sacor On-Site Laser, Toronto, on 3 January 2003, 5 years and 3 months after the previous enhancement. Pre-operative topography again showed no abnormalities. Pachymetry was RE 528μm compared with the theoretical corneal thickness of 316 + 160 = 476μm. The right scotopic pupil measured 5.5mm. The flap was lifted at the operating microscope using a Sinskey hook. The correct site of the flap edge in the temporal, peripheral cornea was first identified by gentle pressure on the cornea. Flap lifting was completed with a blunt spatula. It was noted that the flap lifted very easily; it certainly did not give the impression that it had last been lifted 5 years and 3 months previously. The excimer laser used to do the treatment was the Laser Sight LSX with an Accutrack eye tracker. The treatment at the corneal plane was RE –1.47, zone size of 6.00mm with a 1mm blend zone outside the optical zone, ablation of 24μm to leave a theoretical stromal bed of RE 316 – 24 = 292μm. A bandage soft contact lens did not have to be used post-operatively because the flap junction had not been disrupted unduly.
The initial result of this second RE enhancement on 10 January 2003 was uncorrected RE vision of 6/7– with a plano refraction. There was a small, horizontal microstria just below the pupil margin at slit-lamp examination; this was asymptomatic. The patient is currently lost to follow-up because he has escaped the Canadian winter again!