Irregular Astigmatism After Corneal Transplantation—Efficacy And

CLINICAL SCIENCE

Irregular Astigmatism After Corneal Transplantation—Efﬁcacy and Safety of Topography-Guided Treatment

Inês Laíns, MD, MSc,*† Andreia M. Rosa, MD,*† Marta Guerra, MD, MSc,* Cristina Tavares, MD,* Conceição Lobo, MD, PhD,*† Maria F. L. Silva, PhD,‡ Maria J. Quadrado, MD, PhD,*† and Joaquim N. Murta, MD, PhD*†

Key Words: astigmatism, corneal topography, corneal transplanta- Purpose: fi To analyze the ef cacy and safety of topography-guided tion, excimer, photorefractive keratectomy photorefractive keratectomy (TG-PRK) to treat irregular astigmatism after corneal transplantation. (Cornea 2016;35:30–36) Methods: This was a retrospective observational case series. Eyes with irregular astigmatism after penetrating keratoplasty treated with orneal transplantation (CT) is one of the most commonly TG-PRK (Allegretto Wave Eye-Q) with the topography-guided Cperformed transplant procedures throughout the world.1 customized ablation treatment protocol were included. All treatments Although it is generally successful, patients frequently present had been planned to correct the topographic irregularities, as well as with high irregular postoperative astigmatism, which pre- to reduce the refractive error after neutralizing the induced refractive cludes them from achieving satisfactory visual acuity.2 It can change. Clinical records, treatment plan, and the examinations affect up to 40% of the eyes3 and remains a challenge even for performed were reviewed and the following data were collected: experienced cornea specialists, as spectacles and rigid contact corrected and uncorrected distance visual acuities; manifest refrac- lenses often represent an unsuccessful option for visual tion; topographic parameters, and corneal endothelial cell count. rehabilitation.4 Results: We included 31 eyes [30 patients; mean age 45.0 6 13.4 In recent decades, excimer laser treatment has emerged 5 (SD) years]. At the last postoperative follow-up (mean 9.2 6 8.2 as an alternative. The conventional ablation procedures months), we observed a significant improvement in corrected (P = account only for lower-order aberrations, such as defocus fi 0.001) and uncorrected distance visual acuities (P , 0.001). There and regular astigmatism; therefore, their ef cacy is widely was a gain of $1 uncorrected distance visual acuity line in 96.8% limited for the highly aberrated post-CT corneas. When the (n = 30) of the eyes. Similarly, the refractive parameters also target is irregular astigmatism, customized ablation protocols 6 improved (cylinder P , 0.001; spherical equivalent P = 0.002). At must be considered. Currently, there are 2 options available: the last visit, 54.8% (n = 17) of the patients presented a spherical wavefront-guided and topography-guided (TG). Wavefront equivalent of 61 D. The 3-mm topographic irregularity also ablation considers the aberrations of the entire eye and assumes decreased significantly (P , 0.001). There was no significant that most, and potentially all, can be corrected by reshaping the 7 variation of the corneal endothelial cell count. cornea. However, mainly because of the limitations of the current wavefront sensors8 (aberrometers), these measurements Conclusions: This is the largest case series of TG-PRK to treat are difficult to obtain and are usually not accurate in highly irregular astigmatism in postcorneal transplantation eyes. Our results aberrated corneas.9 Additionally, this treatment protocol does confirm that TG-PRK is an efficient treatment, associated with not address their core pathology,10 as in these cases, higher- fi signi cant improvements of both visual acuity and refractive order aberrations and irregular astigmatism are mainly attrib- parameters. uted to corneal irregularities.6 Conversely, TG treatments rely only on topographic corneal height maps11 and thus can be more suitable. This 10 Received for publication June 11, 2015; revision received August 19, 2015; was highlighted in a recent review, which concluded that, accepted August 26, 2015. Published online ahead of print October 28, even with reliable wavefront measurements, in the presence 2015. of significant corneal irregularities, TG treatments may be From the *Department of Ophthalmology, Centro Hospitalar e Universitário de Coimbra, Coimbra, Portugal; †Faculty of Medicine, University of Coimbra, superior. TG ablation is planned to reshape the irregular Coimbra, Portugal; and ‡Visual Neuroscience Laboratory, CNC.IBILI, cornea to a symmetric regular surface by fitting it to the best Faculty of Medicine, University of Coimbra, Coimbra, Portugal. asphere.10 The main skepticism of this approach is the The authors have no funding or conflicts of interest to disclose. theoretical lack of predictability of the final refractive Reprints: Joaquim N. Murta, MD, PhD, Department of Ophthalmology, outcome because of unknown changes induced by the Centro Hospitalar e Universitário de Coimbra, Praceta Prof. Mota Pinto, 7 3049 Coimbra, Portugal (e-mail: [email protected]). correction of irregularities. The new treatment protocols Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved. already take it into account, performing a final adjustment to

30 | www.corneajrnl.com Cornea Volume 35, Number 1, January 2016

the manifest refractive error, but a second procedure may be charts (converted to logMAR values for analysis), manifest required to address it.12 refractive parameters (spherical equivalent, manifest cylinder Despite the current evidence that TG ablation treat- and sphere), applanation tonometry, corneal endothelial cell ments are more suitable for highly irregular corneas11 and density (cells per squared millimeter), topographic parameters therefore may represent the most appropriate option for post- (irregularities at the 3- and 5-mm zones), and central CT eyes, only small limited series4,8,11,13–15 have been pachymetry (Orbscan IIz system; Bausch & Lomb). Treat- published, and it is not widely adopted. ment characteristics were also collected, namely the maxi- To our knowledge, this study presents the largest case mum and central ablation treated, as well as the optical and series of irregular astigmatism after CT treated with ablation zones and the treated refractive error. Duration of topography-guided photorefractive keratectomy (PRK). Our follow-up and complications were also registered. aim was to evaluate the efficacy and safety of this approach. Surgical Plan and Surgical Technique MATERIALS AND METHODS All eyes had been treated with topography-guided This is a retrospective, noncomparative, consecutive customized ablation treatment (T-CAT) PRK with the Alle- case series, conducted at the Department of Ophthalmology, gretto Eye-Q 400-Hz excimer Wavelight (Germany) (wave- Centro Hospitalar e Universitário de Coimbra, Coimbra, length: 193 nm, pulse duration: 12 nanoseconds, repetition rate: Portugal. Before TG surgery, all patients were informed 400 Hz). TG-PRK was always performed at least: 12 months about the risks and benefits of the procedure. All patients after CT; 6 months after the removal of the last sutures—sutures signed an informed consent form in accordance with the were removed in the steepest meridian when topographic Declaration of Helsinki, in which they agreed that their astigmatism (Orbscan IIz system; Bausch & Lomb) was equal clinical data could be included in scientific studies. or superior to 3 diopters (D). If the astigmatism remained high despite this approach, all sutures were removed; 6 months of confirmed refractive stability, defined as less than 0.50 D Study Design and Population change; and adequate corneal thickness. Eyes submitted to TG-PRK were identified in our All surgical plans were performed by the same surgeon database, and their clinical records were reviewed. Only (A.M.R.), based on data obtained using the Allegretto Top- subjects who fulfilled the following inclusion criteria were olyzer (Germany). This is a Placido-based system with 11 considered for this study: (1) TG-PRK performed according rings that generates 22,000 measuring points and has an to the protocol described below, because of irregular integrated keratometer. It provides several topographic maps, astigmatism caused by CT; (2) Minimum follow-up of 6 which should be similar to each other. Up to 8 maps are months; (3) Availability in the preoperative evaluation and averaged by the system, and the percentage of the data the last appointment of corneal topography and pachymetry contained in the chosen optical zone is displayed. Highly obtained with the Orbscan IIz system (Bausch & Lomb, irregular corneas after CT, without a specific pattern of Rochester, NY), and the corneal endothelial cell count astigmatism, were treated as long as more than 90% of their obtained with the Topcon specular microscope. Irregular area was acquired (maps with less than 90% of data are astigmatism was considered as the presence of spectacle excluded automatically) and data were reproducible in 8 corrected distance visual acuity (CDVA) of one or more lines topographic maps. Eyes that did not fulfill these criteria were less than the visual acuity with a rigid contact lens or pinhole, not submitted to this treatment. To perform the surgical plans, 7 coupled with the presence of topographic changes—either the following protocol was followed stepwise : unequal slopes of hemimeridians along a single meridian or 1. Initially, the surgeon evaluated the treatment plans hemimeridians of an equal slope but not aligned with each 16 produced by the Topolyzer without information about other, or a combination of both. manifest refraction. As the correction of the irregular- For this analysis, we excluded patients with a spectacle ities induces a shift in refraction, manifest refraction CDVA inferior to 20/100 (0.70 logMAR) or with a history of fl should not be initially entered, otherwise it can induce other concomitant ocular pathologies (such as retinal, in am- a refractive error. matory, autoimmune, or neuroophthalmic diseases), as well 2. Second, the induced change in sphere and the needed as a history of other ocular surgeries besides CT. In addition, amount of treatment to compensate for it were identified. among eyes undergoing CT, we included only subjects For example, if more tissue ablation was planned for the treated with penetrating keratoplasty (PK). Other surgical periphery than for the center, resembling a hyperopic techniques, such as deep anterior lamellar keratoplasty, were correction, it would induce myopia (ie, make the central excluded from our study because they induce different 17,18 cornea steeper), which must be taken into account. This biomechanical corneal responses and represented is performed by adjusting the spherical equivalent (C12) a minority of the cases that we have treated with TG-PRK. fi and sphere (C4) until they are similar. For subjects who ful lled all the eligibility criteria, the 3. Finally, the manifest refraction was added to calculate following data were collected: age; sex; treated eye; primary the final treatment. diagnosis for CT; clinical data from the baseline visit (before TG treatment) and the last follow-up visit—uncorrected Treatment was centered on the visual axis. The target distance visual acuity (UDVA) and CDVA with Snellen asphericity was not adjusted, because previous authors

suggested that it is usually associated with poor predictabil- eyes. The main primary diagnosis leading to CT was ity.19 This system considers all aberrations up to the sixth keratoconus (74.2%). The remaining were corneal central order as a whole, so no selective treatments based on Zernike scars due to herpes simplex keratitis (6.5%) or due to other terms were applied. The only exception refers to tilt, which causes (19.4%), including previous trauma. All eyes had been the software allows to unselect. By definition, tilt is a lower- submitted to PK, with the diameters of corneal buttons order aberration that describes a prism error of an eye.20 Its varying from 8 to 8.5 mm. The baseline characteristics of correction would require a prism-like ablation profile, with the included subjects are detailed in Table 1. maximum ablation on one point of the optical zone and zero Regarding TG-PRK ablation, the maximum treatment ablation at the opposite edge of the optical zone, thus applied was 110.4 6 28.2 mm (range: 60.5–171.9 mm) and the requiring large amounts of tissue removal. Considering this, central ablation was 90.4 6 37.6 mm (range: 13.8–171.5 mm). treating a prism error would increase the central ablation The mean correction performed in these eyes was 25.86 6 depth without affecting the refractive result, so we selected 0.84 D (range: 212.00 to 0.00 D) of sphere and 5.47 6 0.84 “Tilt off” in all our treatment plans. No additional modifica- of cylinder (range: 3.29–6.00 D). The optical and ablation tions of the aberration profile are possible with this software. zones varied between 5.0 to 6.5 mm and 8.0 to 9.0 mm, Regarding tissue ablation, besides taking into account respectively. that the maximum approved treatment for the T-CAT protocol is up to 6 D of astigmatism in the corneal plan,7 we did not predefine a maximum value, as the other treatment option for Postoperative Outcomes these eyes would be to perform a new corneal transplantation. The mean duration of available follow-up was 9.2 6 However, the system does not allow any treatments that may 8.2 months (range: 6–33 months). At the last visit, CDVA result in a minimum residual corneal thickness inferior to 250 presented a significant improvement (0.14 6 0.19 logMAR) mm. For eyes requiring deep ablations (total equal or superior compared with baseline (0.25 6 0.15 logMAR, P = 0.001) to 210 D), we reduced the ablation area 0.5 to 1.0 mm. (Fig. 1A). Surgeries were performed by 4 surgeons (A.M.R., C.T., C.L., and M.J.Q.) under topical anesthesia. The corneal epithelium was mechanically removed with a spatula, and then TABLE 1. Clinical and Demographic Characteristics of the patients were asked to fixate on a target light during corneal Study Population ablation, under constant eye-tracking control. Immediately after Sample Eyes/Patients, n 31/30 laser ablation, mitomycin C 0.02% was applied during 40 Age, yrs seconds with a Weck sponge, which was placed over the ablated 6 6 stroma to avoid haze and refractive regression. The corneal Mean SD 45.0 13.4 surface and the entire conjunctiva were then vigorously irrigated Range 23 to 83 with saline solution. At the end of the procedure, a bandage Sex, male/female, no. patients 20/11 contact lens was applied and kept until the fourth day after Eye, right/left, n 18/13 surgery. Topical antibiotic was prescribed in the first 2 weeks, Primary diagnosis, eyes, n (%) and steroids were administered for 3 months, with a tapered Keratoconus 23 (74.2) dosing scheduled. Subjects with a history of herpetic keratitis Central scar due to herpetic keratitis 2 (6.5) were additionally treated with oral acyclovir 400 mg twice per Central scar due to other causes 6 (19.4) 21 UDVA, logMAR day. Postoperative visits were scheduled at 3 days and 1 6 6 month after surgery, and then according to the clinical evolution. Mean SD 0.95 0.27 Range 0.52 to 1.30 CDVA, logMAR 6 6 Statistical Analysis Mean SD 0.25 0.15 The sample’s demographics and clinical characteristics Range 0.00 to 0.70 Manifest spherical equivalent, D were summarized with traditional descriptive methods, namely 6 2 6 mean 6 SD for continuous variables and percentages (%) for Mean SD 3.36 3.68 Range 216.00 to 3.00 nominal or categorical parameters. Assumption of normality was – Manifest cylinder, D calculated with the Shapiro Wilk test. Because all the evaluated 6 6 comparisons related to continuous variables, preoperative and Mean SD 6.35 2.21 Range 3.00 to 11.00 postoperative values were assessed with the paired-sample t test Central pachymetry, mm when normality was observed and with the 1-sample sign test 6 6 when it was not. Statistical analysis was performed with SPSS Mean SD 546.3 81.7 statistical software, version 20.0 (SPSS Inc, Chicago, IL), and Range 313 to 733 the significance level was set at P # 0.05. 3-mm irregularity, D Mean 6 SD 3.80 6 1.39 Range 2.00 to 8.80 5-mm irregularity, D RESULTS 6 6 We included 31 eyes of 30 patients [mean age 45.0 6 Mean SD 6.27 2.56 13.4 (SD) years]. Of the treated eyes, 18 (58.1%) were right Range 2.90 to 13.30

FIGURE 1. Visual and refractive outcomes. A, Visual acuity variation during follow-up. Error bars denote SD. B, Gain of CDVA lines. C, Gain of UDVA lines. D, Evolution of manifest refraction during the follow-up. Error bars indicate SD.

Most of the eyes (n = 23, 74.2%) gained at least 1 line of 6 103.1 mm (range: 260–667 mm). Six eyes (19.4%) CDVA, and 12.9% (n = 4) presented a gain of 5 or more lines, developed haze, within an average time of 52.0 6 29.0 aspresentedinFigure1B.In2cases,theoppositewas days (range: 11–90 days). In all but one case, referred to observed, with loss of 1 and 3 lines of CDVA, respectively. above, haze was classified as grade 1 and was successfully The first case developed postoperative grade 3 central haze. The treated with topical steroids. There were no other post- second was due to recurrence of herpetic keratitis with further operative complications registered during the follow-up. development of a central corneal scar. The mean gain of CDVA Thirty-two percent (32.3%, n = 10) of the eyes were lines was 1.85 6 1.32 (range: loss of 3 to gain of 6 lines). followed for at least 1 year, and no cases of postoperative A similar pattern of improvement was observed in ectasia were described. Figure 2 presents an example of UDVA (Fig. 1A). UDVA increased from 0.95 6 0.27 a case successfully treated with TG-PRK. logMAR to 0.38 6 0.30 logMAR, P , 0.001. At the last follow-up, all but 1 eye (96.8%) had gained lines of UDVA (Fig. 1C). Interestingly, a high percentage of eyes gained at DISCUSSION least 5 lines of UDVA (42.0%), with a mean gain of UDVA We present a retrospective case series of 31 eyes with lines of 4.55 6 3.04 (range: 0–9). irregular astigmatism after PK treated with TG-PRK. Our data Regarding manifest refraction, there was a significant reveal that this treatment was associated with a significant reduction in both spherical equivalent (23.36 6 3.68 to improvement in both CDVA (P = 0.001) and UDVA (P , 21.11 6 1.63 D, P = 0.002) and cylinder (6.35 6 2.21 D 0.001). At the last follow-up visit, 74.2% of the eyes (n = 23) preoperative to 1.96 6 1.14 D, P , 0.001). Figure 1D had gained CDVA lines and a gain of UDVA was also presents the comparison before and after TG-PRK. observed in 96.8% (n = 30). This was accompanied by an At the last visit, 54.8% (n = 17) of the eyes presented improvement of manifest refraction (cylinder, P , 0.001; a manifest spherical equivalent of 61.00 D (range 24.75 to spherical equivalent, P = 0.002), without significant post- 1.75 D). All treated subjects presented at that time a manifest operative complications. cylinder #4 D (range: 0–4 D), with 29.0% (n = 9) of them Besides the relevance of the observed UDVA improve- within 1 D and 61.3% (n = 19) up to 2 D. Among the eyes ment, the CDVA increase is particularly critical for patients. It with less than 6.5 D of preoperative manifest cylinder (6 D in represents an opportunity of returning to useful and tolerable the corneal plane, n = 18), 36.8% presented less than 1 D of spectacles or soft contact lens wear,10 which is usually not postoperative refractive astigmatism. possible in highly irregular corneas, as observed after CT.22 The topographic irregularities also improved signifi- Other published studies in this field suggested similar results. cantly in the central 3 mm (P , 0.001) but not in the central 5 For example, Rajan et al14 published the largest complete mm. There was no significant decrease in the corneal series available so far (n = 16 eyes, with TG laser-assisted endothelial cell count (1123 6 756 cells/mm2 to 1027 6 subepithelial keratectomy) and also observed significant 330 cells/mm2, P = 0.799). Mean final pachymetry was 443.7 CDVA and UDVA improvements. Regarding TG-PRK, Lin

FIGURE 2. We present a case of a 66 year-old man, with a history of PK in the left eye, which was performed 6 years before because of keratoconus. The patient presented a CDVA of 20/50, with a manifest refraction of 26.50 · 15 degrees. A, Pre- operative Topolyzer topography map. As deﬁned in our protocol, 8 of these maps were averaged to obtain the initial treatment plan, which is shown in (B). In this initial plan, the required cylindrical correction would be approximately 9 D (white box). However, it can be safely performed only up to 6 D, so refractive correction was added to sphere. Then, a balance between it (C4, sphere) and spherical equivalent (C12) was guaranteed, achieving the ﬁnal treatment plan. C, The white box highlights the initial treatment plan and the plan after the described adjustments. In D, we present the Topolyzer map, 3 months after TG-PRK, with an evident improvement compared with the obtained preoperatively (A). In the last visit, the patient presented a CDVA of 20/20, with a correction of 23.0 · 140 degrees.

et al15 evaluated its efficacy to treat several causes of irregular cases. In this study, MMC was not used, which is probably astigmatism, including 27 eyes with a history of CT. linked with these results. As detailed, all our eyes were treated However, the authors did not independently characterize this with MMC, and we registered 6 cases (19.4%) of haze. All population at baseline and did not mention any preoperative but one resolved with topical steroids, and there was no requirements, such as time after the first surgery, so we cannot significant decrease in corneal endothelial cell density compare the data. Interestingly, it was recently described13 associated with this procedure, which suggests that higher that eyes after CT can present higher UDVA gains than eyes duration of MMC exposure might need to be considered in with other diagnoses (such as decentered optic zone, among some cases in the future. Interestingly, a higher incidence of others), but that the gain of CDVA can present an opposite haze after CT has been described also with conventional trend.8 Actually, Allan and Hassan8 observed that CDVA gain excimer ablation treatments,23 and other authors4,14,24 had was lower in patients with irregular astigmatism after CT than already emphasized that patients previously submitted to after previous refractive surgery, describing a median gain of corneal transplantation should always receive MMC with TG- 0 lines for CT eyes. The authors justified these outcomes by PRK ablations. Besides the described occurrence of haze, we the development of severe haze in a significant number of observed no other postoperative complications except 1 case

of herpetic keratitis recurrence. This happened despite oral be interesting. Additionally, despite not being our aim, it acyclovir prophylactic treatment, thus suggesting that these would also be interesting to compare TG with wavefront- eyes should be carefully monitored after this type of laser guided ablations. The current evidence7,10,22 suggests that the treatment. former are theoretically more appropriate for highly aberrated Regarding the refractive outcomes, they were also eyes, such as post-CT eyes. However, a prospective compar- successful in this study and are particularly relevant to ative study could provide important inputs to achieve definite discuss as one of the main skepticisms regarding TG ablation conclusions in this field. Another limitation refers to our is the theoretical unpredictability of the refraction obtained eligibility criteria of a minimum spectacle CDVA of 20/100 finally.12 Any corneal topographic change leads to an (0.70 logMAR) that can induce selection bias and may accompanying change in refraction.22 However, as described, influence our results. current surgical TG plans account for it. This results in In conclusion, this large case series demonstrated that satisfactory refractive correction, as shown in the present case TG ablations are an efficient treatment of irregular astigmatism series. Actually, our results are particularly satisfactory after corneal transplantation. The successful visual and refrac- considering the complexity of these eyes and their pre- tive results are probably linked with the performed smoothing operative extremely high manifest cylinders, ranging from 3 of the anterior cornea, thus removing its irregular surface to 11 D. Considering that the maximum approved treatment shape, which is frequently the cause of the irregular astigma- for the T-CAT protocol is up to 6 D of astigmatism in the tism and higher aberrations observed in transplanted eyes. corneal plan,7 undercorrection was planned for a high percentage of these eyes, which probably precluded even better results. In fact, when we considered only eyes with REFERENCES 1. Felipe AF, Hammersmith KM, Nottage JM, et al. Indications, visual astigmatism within the treatable range, the postoperative outcome, and ectasia in clear corneal transplants 20 years old or more. refractive cylinder was lower (36.1% within 1 D, compared Cornea. 2013;32:602–607. with 29.0% considering all the included study population). 2. Perlman EM. An analysis and interpretation of refractive errors after Vector analysis methods25 for the evaluation of surgically penetrating keratoplasty. Ophthalmology. 1981;88:39–45. induced refractive correction are commonly used to evaluate 3. 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