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Influence of pregnancy on refractive parameters after laser in situ keratomileusis surgery
Influencia del embarazo sobre los parámetros refractivos tras cirugía laser in situ keratomileusis
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López-Prats, J.J. Hidalgo-Mora, E. Sanz-Marco, A. Pellicer, A. Perales, M. Díaz-Llopis" "autores" => array:6 [ 0 => array:4 [ "nombre" => "M.J." "apellidos" => "López-Prats" "email" => array:1 [ 0 => "susa_lpl@hotmail.com" ] "referencia" => array:2 [ 0 => array:2 [ "etiqueta" => "<span class="elsevierStyleSup">a</span>" "identificador" => "aff0005" ] 1 => array:2 [ "etiqueta" => "<span class="elsevierStyleSup">¿</span>" "identificador" => "cor0005" ] ] ] 1 => array:3 [ "nombre" => "J.J." "apellidos" => "Hidalgo-Mora" "referencia" => array:1 [ 0 => array:2 [ "etiqueta" => "<span class="elsevierStyleSup">b</span>" "identificador" => "aff0010" ] ] ] 2 => array:3 [ "nombre" => "E." "apellidos" => "Sanz-Marco" "referencia" => array:1 [ 0 => array:2 [ "etiqueta" => "<span class="elsevierStyleSup">a</span>" "identificador" => "aff0005" ] ] ] 3 => array:3 [ "nombre" => "A." 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"apellidos" => "Díaz-Llopis" "referencia" => array:1 [ 0 => array:2 [ "etiqueta" => "<span class="elsevierStyleSup">a</span>" "identificador" => "aff0005" ] ] ] ] "afiliaciones" => array:2 [ 0 => array:3 [ "entidad" => "Servicio de Oftalmología, Hospital Universitario La Fe, Valencia, Spain" "etiqueta" => "<span class="elsevierStyleSup">a</span>" "identificador" => "aff0005" ] 1 => array:3 [ "entidad" => "Servicio de Ginecología y Obstetricia, Hospital Universitario La Fe, Valencia, Spain" "etiqueta" => "<span class="elsevierStyleSup">b</span>" "identificador" => "aff0010" ] ] "correspondencia" => array:1 [ 0 => array:3 [ "identificador" => "cor0005" "etiqueta" => "⁎" "correspondencia" => "<span class="elsevierStyleItalic">Corresponding author</span>." ] ] ] ] "titulosAlternativos" => array:1 [ "es" => array:1 [ "titulo" => "Influencia del embarazo sobre los parámetros refractivos tras cirugía <span class="elsevierStyleItalic">laser in situ keratomileusis</span>" ] ] "textoCompleto" => "<span class="elsevierStyleSections"><span id="sec0005" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Introduction</span><p id="par0005" class="elsevierStylePara elsevierViewall">Different ocular changes associated to pregnancy, such as diminished ocular pressure, diminished tear production and alterations in structures such as the cornea and lens have been studied in the past decades with unconclusive and even contradictory results.<a class="elsevierStyleCrossRefs" href="#bib0005"><span class="elsevierStyleSup">1,2</span></a></p><p id="par0010" class="elsevierStylePara elsevierViewall">Estrogen receptors have been proposed as the cause of the physiological modifications in the cornea and the lens, with the ensuing increase of stimulation for said modifications.<a class="elsevierStyleCrossRef" href="#bib0010"><span class="elsevierStyleSup">2</span></a> The cornea could exhibit an increase of its central thickness between 1 and 16<span class="elsevierStyleHsp" style=""></span>μm, also due to its edematization secondary to liquid retention typical of gestation. In addition, corneal curvature could also increase in an average of 1<span class="elsevierStyleHsp" style=""></span>dpt during the second half of pregnancy. Both changes could be resolved after labor or lactation. Furthermore, changes have been described in the lens morphologies such as increased curvature, which could give rise to a temporary loss of accommodation capacity.<a class="elsevierStyleCrossRefs" href="#bib0010"><span class="elsevierStyleSup">2–6</span></a></p><p id="par0015" class="elsevierStylePara elsevierViewall">However, there is no consensus on these proposals. Whereas some studies have not found significant changes in corneal sensitivity, others have demonstrated alterations in these parameters during pregnancy.<a class="elsevierStyleCrossRefs" href="#bib0025"><span class="elsevierStyleSup">5,7</span></a> In the latter type of study, it is frequent to find in clinical practice contact lens intolerance among pregnant patients, which could be explained by the changes in corneal curvature and thickness as well as the reduction of tear production during the third quarter of gestation, demonstrated in 18% of studied patients.<a class="elsevierStyleCrossRefs" href="#bib0025"><span class="elsevierStyleSup">5–8</span></a> Some authors have postulated that, despite their presence, these changes do not involve significant variations in visual acuity or refractive error during pregnancy.<a class="elsevierStyleCrossRefs" href="#bib0045"><span class="elsevierStyleSup">9,10</span></a></p><p id="par0020" class="elsevierStylePara elsevierViewall">On the other hand, various complications in corneal refractive surgery associated to pregnancy have been pointed out. One is myopic regression, consisting in lower efficacy of the technique, associated to the normal cicatrization process of the surgical wound. In order to compensate for the defect created by the laser, a proliferation of keratocytes would occur together with growth of epithelial and stromal tissue, which could partially or totally reverse the refractive defects obtained with the surgery, particularly in severely myopic patients.<a class="elsevierStyleCrossRefs" href="#bib0055"><span class="elsevierStyleSup">11,12</span></a> Accordingly, pregnancy could involve increased risk in this regard due to the physiological changes that occur at the corneal level and cause its thickening and edematization.</p><p id="par0025" class="elsevierStylePara elsevierViewall">Corneal haze constitutes an additional complication described in pregnancy and is associated to laser refractive surgery. Its cause is not known although it is believed to be related with alterations in the cicatrization of the interface created during surgery.<a class="elsevierStyleCrossRef" href="#bib0065"><span class="elsevierStyleSup">13</span></a> Other complications have been described, including corneal ectasia, less frequent but more severe than those described above.<a class="elsevierStyleCrossRef" href="#bib0070"><span class="elsevierStyleSup">14</span></a></p><p id="par0030" class="elsevierStylePara elsevierViewall">In recent years, several papers have been published assessing the influence of pregnancy in patients intervened for PRK.<a class="elsevierStyleCrossRefs" href="#bib0055"><span class="elsevierStyleSup">11,15–17</span></a> However, even though PRK has become the most widely used corneal surgery, there is no literature concerning the effects of pregnancy in women who undergo LASIK.<a class="elsevierStyleCrossRef" href="#bib0090"><span class="elsevierStyleSup">18</span></a></p><p id="par0035" class="elsevierStylePara elsevierViewall">For the above reasons, we considered a prospective observational study in which an analysis of visual acuity and the anatomic characteristics of ocular structures which have the potential of modifying diopter power would enable us to assess the ways in which changes in ocular physiology during pregnancy and postpartum could alter the refractive condition in pregnant women who have previously undergone LASIK surgery. An additional objective was to assess the risk that pregnancy could involve for the appearance or development of post-surgery ophthalmological complications. This paper presents the results of the modifications observed in said patients in the first 2 quarters of gestation.</p></span><span id="sec0010" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Materials and methods</span><p id="par0040" class="elsevierStylePara elsevierViewall">The study, with the participation of patients, was carried out in accordance with human experimentation rules of the Nuremberg Code (1947), the declarations of Helsinki (1964), Sidney (1968), Tokyo (1975), Venice (1983), Hong-Kong (1989) and supplementary regulations, directive 91/507/CE, R.D. 561/1993, the Bioethics Agreement of the Council of Europe (BOE 20/10/99) and the medical ethics and deontology codes in force.</p><span id="sec0015" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Patients</span><p id="par0045" class="elsevierStylePara elsevierViewall">Overall, 36 eyes were analyzed, 18 belonging to the study group comprising nine pregnant women who previously underwent LASIK surgery and a further 18 belonging to the control group made up of nine pregnant women with refractive alterations without surgical correction. The age of the patients was between 18 and 35 in order to avoid changes derived from presbyopia becoming a confusion factor when analyzing refractive results.</p><p id="par0050" class="elsevierStylePara elsevierViewall">Participating patients were referred to the Ophthalmology Service of the <span class="elsevierStyleItalic">La Fe</span> Hospital of Valencia from the Obstetrics Service of said hospital after their first visit prior to the twelfth week of gestation and obstetric anamnesis evidenced refractive surgery history, prior to confirmation of compliance with the inclusion criteria and informed consent signature.</p></span><span id="sec0020" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Type of study and sample size</span><p id="par0055" class="elsevierStylePara elsevierViewall">The study was designed to be analytic, observational and prospective with cohort and control group. The sample size calculated for the study group was of 34 eyes (17 patients), obtained by taking population size twice the size of the analyzed group in the study with the largest sample published to date.<a class="elsevierStyleCrossRef" href="#bib0075"><span class="elsevierStyleSup">15</span></a> The control group was made up by the same number of patients.</p><p id="par0060" class="elsevierStylePara elsevierViewall">The data and results obtained from the interviews and diagnostic tests were included in a custom made database utilizing the application <span class="elsevierStyleItalic">Statistical Package for the Social Sciences</span> (SPSS) version 17 (IBM spss statistics 17). The statistical analysis of data was made utilizing the nonparametric tests for related samples (Wilcoxon test) considering a statistically significant value of <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span><<span class="elsevierStyleHsp" style=""></span>0.05 with a confidence interval of 95%.</p></span><span id="sec0025" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Ophthalmological study</span><p id="par0065" class="elsevierStylePara elsevierViewall">The patients were assessed during the first 2 quarters of gestation, carrying out the explorations described below and obtaining clinical data on the course of the pregnancy as well as the observed ophthalmological symptoms and signs in personal interviews.</p><p id="par0070" class="elsevierStylePara elsevierViewall">The following diagnostic means were applied for each one of the assessments:<ul class="elsevierStyleList" id="lis0005"><li class="elsevierStyleListItem" id="lsti0005"><span class="elsevierStyleLabel">-</span><p id="par0075" class="elsevierStylePara elsevierViewall">Anterior pole biomicroscopy and photograph (visual study of the entire anterior ocular segment): Shin-Nippon SL-203<span class="elsevierStyleSup">®</span> slit lamp.</p></li><li class="elsevierStyleListItem" id="lsti0010"><span class="elsevierStyleLabel">-</span><p id="par0080" class="elsevierStylePara elsevierViewall">Objective refraction measure: Topcon KR8100<span class="elsevierStyleSup">®</span> autorefractometer.</p></li><li class="elsevierStyleListItem" id="lsti0015"><span class="elsevierStyleLabel">-</span><p id="par0085" class="elsevierStylePara elsevierViewall">Axial length study, the anterior chamber depth and keratometry (curvature measurement of the 2 main corneal axes, information on diopter power of the central cornea and of the presence of aberrations such as astigmatism, ectasia or keratoconus): Zeiss Iol Master<span class="elsevierStyleSup">®</span>.</p></li><li class="elsevierStyleListItem" id="lsti0020"><span class="elsevierStyleLabel">-</span><p id="par0090" class="elsevierStylePara elsevierViewall">Corneal thickness analysis and topography (surface) and anterior chamber measurements: Oculus<span class="elsevierStyleSup">®</span> Pentacam.</p></li></ul></p></span></span><span id="sec0030" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Results</span><p id="par0095" class="elsevierStylePara elsevierViewall">During the first 2 quarters of gestation, refractive data were measured in sphere, cylinder and EE value diopters (D) along with uncorrected visual acuity in the Snellen scale of 36 eyes divided in 2 groups, where 18 eyes were submitted to refractive surgery (LASIK) as the study group and 18 eyes with refractive involvement without surgery as the control group. The main parameters of the analysis comprised visual acuity and the values of sphere, cylinder and EE. In addition, intraocular pressure (IOP) was measured in both quarters.</p><p id="par0100" class="elsevierStylePara elsevierViewall">Mean equity in the group of intervened pregnant patients was of 0.9<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.13 in the first quarter and of 0.83<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.19 in the second quarter, without observed differences being significant (Wilcoxon test; <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.059). In the control group the results were 0.94<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.1 and 0.92<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.12 in the first and second portions respectively, likewise without exhibiting statistically significant differences (Wilcoxon test; <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.340).</p><p id="par0105" class="elsevierStylePara elsevierViewall">The spherical refractive value in the study group was of −0.77<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.6<span class="elsevierStyleHsp" style=""></span>D in the first quarter and −1<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.81<span class="elsevierStyleHsp" style=""></span>D in the second quarter, with a mean decrease of 0.25<span class="elsevierStyleHsp" style=""></span>D. In the control group, the results were −2.57<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>4.17<span class="elsevierStyleHsp" style=""></span>D in the first quarter and −2.62<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>4.04<span class="elsevierStyleHsp" style=""></span>D in the second quarter. None of the groups exhibited significant differences (Wilcoxon test; <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.072 and <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.245 respectively).</p><p id="par0110" class="elsevierStylePara elsevierViewall">Concerning the cylinder, the group of surgically intervened patients exhibited values of 0.3<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.37<span class="elsevierStyleHsp" style=""></span>D in the first quarter and 0.61<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.5<span class="elsevierStyleHsp" style=""></span>D in the second. Here, statistically significant differences were observed with a mean increase of 0.3<span class="elsevierStyleHsp" style=""></span>D (Wilcoxon test; <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>≤<span class="elsevierStyleHsp" style=""></span>0.01). In the control group the results were 1.14<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.75 in the first quarter and of 1.13<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.9 in the second quarter, once more with significant differences (Wilcoxon test; <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.046).</p><p id="par0115" class="elsevierStylePara elsevierViewall">As for the study group, results in the first quarter were of −0.87<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.6<span class="elsevierStyleHsp" style=""></span>D and in the second quarter of −1.37<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.75<span class="elsevierStyleHsp" style=""></span>D, with a mean increase of 0.5<span class="elsevierStyleHsp" style=""></span>D. In the first quarter, the control group had −3.16<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>4.31<span class="elsevierStyleHsp" style=""></span>D and −3.27<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>4.20<span class="elsevierStyleHsp" style=""></span>D in the second. Statistically significant differences were found in both groups (Wilcoxon test: <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.001 study group; <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.037 control group).</p><p id="par0120" class="elsevierStylePara elsevierViewall">The different evolution of EE values in the study group according to diopters prior to LASIK surgery were analyzed. The sample was divided in 2 subgroups with 9 eyes each. The first group exhibited a presurgery EE up to −4.5<span class="elsevierStyleHsp" style=""></span>D and the second group of −4.5 to −9<span class="elsevierStyleHsp" style=""></span>D. The results for the first group were −0.6<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.47<span class="elsevierStyleHsp" style=""></span>D in the first quarter and −1.3<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.8<span class="elsevierStyleHsp" style=""></span>D in the second, exhibiting a mean EE increase of 0.5<span class="elsevierStyleHsp" style=""></span>D. In the group of surgically intervened patients with a baseline of about 4.5<span class="elsevierStyleHsp" style=""></span>D pre-LASIK, the results obtained were −1.14<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.6<span class="elsevierStyleHsp" style=""></span>D in the first quarter and −1.4<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>0.75<span class="elsevierStyleHsp" style=""></span>D in the second, observing a mean increase of 0.25<span class="elsevierStyleHsp" style=""></span>D. In both separate analysis a statistically significant result was obtained (first subgroup <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span><<span class="elsevierStyleHsp" style=""></span>0.01 and second subgroup <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.026).</p><p id="par0125" class="elsevierStylePara elsevierViewall">In addition, corneal curvature variations were analyzed by means of the <span class="elsevierStyleItalic">K</span><span class="elsevierStyleInf">1</span> and <span class="elsevierStyleItalic">K</span><span class="elsevierStyleInf">2</span> parameters. <span class="elsevierStyleItalic">K</span><span class="elsevierStyleInf">1</span> did not exhibit statistically significant changes between both quarters in any of the groups (study group <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.695; control group <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.126). The same occurred with the <span class="elsevierStyleItalic">K</span><span class="elsevierStyleInf">2</span> parameter (study group <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.378; control group <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.489).</p><p id="par0130" class="elsevierStylePara elsevierViewall">Following the same procedure, no significant changes were found in the axial length between both quarters in the study group (<span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.115).</p><p id="par0135" class="elsevierStylePara elsevierViewall">Lastly, changes in mean IOP in mmHg between both control groups did not exhibit statistically significant differences. The results in the study group were 9.45<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>1.85<span class="elsevierStyleHsp" style=""></span>mmHg in the first quarter and 9.78<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>2<span class="elsevierStyleHsp" style=""></span>mmHg in the second. In the control group, a mean value of 12.6<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>1.45<span class="elsevierStyleHsp" style=""></span>mmHg was found in the first quarter and in the second 13<span class="elsevierStyleHsp" style=""></span>±<span class="elsevierStyleHsp" style=""></span>2.83<span class="elsevierStyleHsp" style=""></span>mmHg (study group <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.358; control group <span class="elsevierStyleItalic">p</span><span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>0.606).</p></span><span id="sec0035" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Discussion</span><p id="par0140" class="elsevierStylePara elsevierViewall">Physiological ocular changes associated to pregnancy and related to the presence of estrogen receptors in the ocular anatomy have been broadly described in the literature.<a class="elsevierStyleCrossRefs" href="#bib0005"><span class="elsevierStyleSup">1,2</span></a> In recent years, several studies have relatedly said changes with possible complications in patients submitted to PRK-type surgery.<a class="elsevierStyleCrossRefs" href="#bib0055"><span class="elsevierStyleSup">11,15–17</span></a></p><p id="par0145" class="elsevierStylePara elsevierViewall">The first of said papers, developed by Hefetz et al. in 1996, studied 8 women who had undergone said type of surgery and during the one year post-op follow-up became pregnant. In the results, the authors pointed out that 2 of the 8 subjects developed myopic regression whereas the remaining 6 maintained a stable ocular situation. Of the latter, three became pregnant at least 5 months after the intervention while the remaining 3 became pregnant only one month after the ocular surgery. With these results, limited by the small number of patients, the authors concluded that pregnancy and labor would not have effects in refractive results after PRK-type laser surgery. However, they observed higher sensitivity to hormonal changes in the cornea of gestating women after surgery compared to the cornea of healthy subjects, mainly due to the restructuring of corneal fibrils which occurs after this type of mechanical procedure.<a class="elsevierStyleCrossRefs" href="#bib0075"><span class="elsevierStyleSup">15,20</span></a></p><p id="par0150" class="elsevierStylePara elsevierViewall">In a subsequent paper, Sharif analyzed again the refractive changes in 9 women who became pregnant after undergoing PRK surgery. These were followed-up for at least one year. Twelve of the 18 eyes (66%) exhibited myopic regression. In addition, 30% developed a corneal haze of 1+ and 53% a corneal haze of 2+, which is not frequent in low or medium myopia post-PRK patients. The 3 women who remained stable had become pregnant at least 5 months after surgery. Sharif pointed out that the said regression, as well as the corneal haze, increased in 50% of the eyes after giving birth. Likewise, he observed a second positive correlation between the higher probability of myopic regression and corneal haze and the higher amount of complications associated to the pregnancy of the patients.<a class="elsevierStyleCrossRef" href="#bib0075"><span class="elsevierStyleSup">15</span></a> As previously described by Machatt in 1996, Sharif observed that 2/3 of the women of the study who suffered a myopic regression had what is considered to be a difficult pregnancy, with intense symptoms such as nausea, vomiting and severe morning discomfort, while on the contrary all the patients who exhibited refractive stability had an easy pregnancy with few associated symptoms. In the conclusions, Sharif recommended avoiding pregnancy for at least 6 months after PRK surgery in order to diminish the risk of complications or regression of the surgery effects.<a class="elsevierStyleCrossRefs" href="#bib0095"><span class="elsevierStyleSup">19,20</span></a> In this regard, Tally et al. and Dinn et al. suggested however that this type of refractive surgery should be delayed until refraction becomes stable in the postpartum period.<a class="elsevierStyleCrossRefs" href="#bib0080"><span class="elsevierStyleSup">16,17</span></a></p><p id="par0155" class="elsevierStylePara elsevierViewall">In our study we observed statistically significant modifications in the EE and cylinder during the first half of the pregnancy in both subjects who had undergone LASIK surgery as well as in those who had not been intervened for refractive defects. However, the reductions in visual acuity, sphere value and IOP did not exhibit relevant alterations. According to our results, pregnancy would have a clear influence on the refractive characteristics both in the eyes of the control group and in those submitted to laser surgery. However, statistical significance in the study group is much more important than in the control group, demonstrating that the mechanical effect on the cornea must be a destabilizing factor when addressing said changes, which are physiological by nature.</p><p id="par0160" class="elsevierStylePara elsevierViewall">With the exception of IOP, each one of the study variables (visual acuity, sphere, cylinder and EE) worsened during the first 2 quarters of pregnancy in both groups. Even so, the magnitude of the changes is not statistically significant in all variables although a clear tendency is apparent. It is worthy to note that one of the limitations we found at this level of the analysis of results is the small sample size even though it is the largest of all groups that have been studied in the international literature to date.</p><p id="par0165" class="elsevierStylePara elsevierViewall">For the EE and cylinder values, our results exhibited clear statistical significance in both groups although it was always more important in the group of LASIK surgery patients.</p><p id="par0170" class="elsevierStylePara elsevierViewall">The fact that the variable exhibiting the biggest modification between both quarters was the cylinder and not the sphere leads us to think that the main cause of this worsening is due to changes that take place at the corneal level, in addition to the fact that said changes are sharper in the cornea submitted to LASIK refractive surgery. An interesting result was found when dividing the study group in 2 subgroups according to presurgery diopters, one (n<span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>9) comprising patients with a presurgery EE up to 4.5<span class="elsevierStyleHsp" style=""></span>D and the other (n<span class="elsevierStyleHsp" style=""></span>=<span class="elsevierStyleHsp" style=""></span>9) with a presurgery ED of 4.5–9<span class="elsevierStyleHsp" style=""></span>D. It was seen that, even though both groups independently exhibited statistical significance, the significance was higher in patients with smaller previous refractive defects. That is, the patients with lower presurgery diopters who in theory endured a smaller alteration of their corneal structure by means of LASIK worsened more. These results lead us to consider the hypotheses that said partially modified cornea, with a larger amount of residual stromal base and therefore a higher number of estrogen receptors, would become more altered due to edematization, in addition to undergoing greater restructuring of their fibrils in a random and disorderly manner. However, the cornea submitted to more aggressive surgery, thinned out to the extreme, would exhibit a smaller residual stromal base with the absence of estrogen receptors to react against the physiological stimuli of pregnancy, apart from having few residual fibrils that could restructure in a disorderly manner.</p><p id="par0175" class="elsevierStylePara elsevierViewall">Significant changes in the corneal curvature as well is in the axial length between both quarters were not evidenced in any of the groups.</p><p id="par0180" class="elsevierStylePara elsevierViewall">The mean uncorrected visual acuity in both groups did not exhibit significant changes. However, the study group evidenced a clear downward tendency between both quarters. Likewise, sphere modifications did not exhibit significant changes but evidenced a much higher tendency towards worsening in the group of operated eyes against non-intervened eyes.</p><p id="par0185" class="elsevierStylePara elsevierViewall">On the other hand, in the references published to date on IOP, it is pointed out as an additional factor that exhibits downward values in the course of pregnancy.<a class="elsevierStyleCrossRefs" href="#bib0005"><span class="elsevierStyleSup">1,2</span></a> However, in our study we did not find statistically significant differences in any of the groups.</p><p id="par0190" class="elsevierStylePara elsevierViewall">According to our results, it is possible to establish a tendency towards the worsening of the refractive condition in the first 2 quarters of pregnancy of gestating women with refractive disorder history, and that this worsening is more significant in patients submitted to LASIK refractive surgery. Accordingly, there are factors, which are not yet established that determine lower capacity of operated cornea to adapt to the physiological changes of pregnancy. There is evidence that during pregnancy the cornea thickens secondary to excessive hydration of the stroma due to the activation of estrogen receptors therein, as well as an influence of these hormones on the elasticity and biomechanics of corneal tissue.<a class="elsevierStyleCrossRef" href="#bib0010"><span class="elsevierStyleSup">2</span></a> The procedure for applying Excimer laser only in specific central areas of a structure which is supposed to be physiologically in proportion and provided with the given number of uniformly distributed estrogen receptors may lead us to consider the partial loss of said receptors only in specific areas, with an ensuing dissimilar edematization when the remaining receptors respond to the growth during gestation. At this point, we should also consider the hypothesis of the loss of the ability of operated cornea to adapt to a uniform and proportional increase in volume, accordingly bringing about an increase in the cylinder associated to variations in the astigmatic axis. In addition to edematization, the said diminished corneal rigidity, which has been described as an effect of estrogens, would be similarly out of proportion and would involve the appearance of different magnitudes of stress upon different points of the corneal surface according to the mechanically weakened areas. According to our results, the absence of variations in the axial length in the study group raises the question whether this was the cause of the refractive parameter changes. In addition, the lack of significant variation in corneal curvature in all groups supports our theory about the presence of as yet undetermined factors which cause operated cornea to suffer greater alterations in their corneal parameters vis-à-vis non-operated cornea, which is not demonstrated with routinely studied clinical data.</p><p id="par0195" class="elsevierStylePara elsevierViewall">By way of conclusion, in the last decade PRK and LASIK have demonstrated their usefulness for treating corneal refractive defects, involving surgical techniques which have been progressively accepted. Women in the age range of 20–30 years have exhibited a greater demand for this treatment. This is a fully fertile decade of life and in many cases corneal surgery is followed by at least one gestation with the effects that this can entail at the ocular level.</p><p id="par0200" class="elsevierStylePara elsevierViewall">In addition to completing this project with data for the remainder of gestation and postpartum, additional developments could involve an assessment of the extent in which mechanically weakened and thin cornea can be deformed without altering their refractive properties and the way in which fibrils restructure after the application of laser affects the cornea when responding to hormonal physiological stimuli.</p></span><span id="sec0040" class="elsevierStyleSection elsevierViewall"><span class="elsevierStyleSectionTitle">Conflict of interest</span><p id="par0205" class="elsevierStylePara elsevierViewall">No conflict of interests has been declared by the authors.</p></span></span>" "textoCompletoSecciones" => array:1 [ "secciones" => array:10 [ 0 => array:2 [ "identificador" => "xres152793" "titulo" => array:5 [ 0 => "Abstract" 1 => "Objectives" 2 => "Methods" 3 => "Results" 4 => "Conclusions" ] ] 1 => array:2 [ "identificador" => "xpalclavsec140798" "titulo" => "Keywords" ] 2 => array:2 [ "identificador" => "xres152792" "titulo" => array:5 [ 0 => "Resumen" 1 => "Objetivos" 2 => "Métodos" 3 => "Resultados" 4 => "Conclusiones" ] ] 3 => array:2 [ "identificador" => "xpalclavsec140799" "titulo" => "Palabras clave" ] 4 => array:2 [ "identificador" => "sec0005" "titulo" => "Introduction" ] 5 => array:3 [ "identificador" => "sec0010" "titulo" => "Materials and methods" "secciones" => array:3 [ 0 => array:2 [ "identificador" => "sec0015" "titulo" => "Patients" ] 1 => array:2 [ "identificador" => "sec0020" "titulo" => "Type of study and sample size" ] 2 => array:2 [ "identificador" => "sec0025" "titulo" => "Ophthalmological study" ] ] ] 6 => array:2 [ "identificador" => "sec0030" "titulo" => "Results" ] 7 => array:2 [ "identificador" => "sec0035" "titulo" => "Discussion" ] 8 => array:2 [ "identificador" => "sec0040" "titulo" => "Conflict of interest" ] 9 => array:1 [ "titulo" => "References" ] ] ] "pdfFichero" => "main.pdf" "tienePdf" => true "fechaRecibido" => "2011-01-15" "fechaAceptado" => "2011-09-11" "PalabrasClave" => array:2 [ "en" => array:1 [ 0 => array:4 [ "clase" => "keyword" "titulo" => "Keywords" "identificador" => "xpalclavsec140798" "palabras" => array:5 [ 0 => "Cornea" 1 => "Refractive surgery" 2 => "Laser in situ keratomileusis" 3 => "Pregnancy" 4 => "Myopia" ] ] ] "es" => array:1 [ 0 => array:4 [ "clase" => "keyword" "titulo" => "Palabras clave" "identificador" => "xpalclavsec140799" "palabras" => array:5 [ 0 => "Córnea" 1 => "Cirugía refractiva" 2 => "Laser in situ keratomileusis" 3 => "Embarazo" 4 => "Miopía" ] ] ] ] "tieneResumen" => true "resumen" => array:2 [ "en" => array:2 [ "titulo" => "Abstract" "resumen" => "<span class="elsevierStyleSectionTitle">Objectives</span><p id="spar0005" class="elsevierStyleSimplePara elsevierViewall">Different ocular changes and complications of refractive surgery such as photorefractive keratectomy (PRK) due to pregnancy have been described in the last few years. However there is no information about the possible problems of laser in situ keratomileusis (LASIK) in pregnant women. Our objective was to study how physiological changes secondary to pregnancy could alter the refractive situation in pregnant women who have undergone LASIK surgery. We show the results obtained due to the changes between the first two trimesters of the pregnancy.</p> <span class="elsevierStyleSectionTitle">Methods</span><p id="spar0010" class="elsevierStyleSimplePara elsevierViewall">A prospective and observational study was conducted in which one study group, made up of 9 patients who had undergone LASIK surgery before becoming pregnant, was compared with a control group of 9 patients with non-surgically corrected refractive problems. The following measurements were made in both groups in the first and second trimesters of the pregnancy; visual acuity, the best corrected visual acuity, tonometry, ocular anatomical characteristics by biometry, and refractive and corneal study by Pentacam<span class="elsevierStyleSup">®</span>.</p> <span class="elsevierStyleSectionTitle">Results</span><p id="spar0015" class="elsevierStyleSimplePara elsevierViewall">Significant changes were observed in the cylinder and spherical equivalent between the two trimesters in both groups. Visual acuity and spherical equivalent show a strong trend towards worsening, which was more significant in the study group. The patients of this group who had a larger pre-surgical defect showed lower modifications during the six first months of pregnancy.</p> <span class="elsevierStyleSectionTitle">Conclusions</span><p id="spar0020" class="elsevierStyleSimplePara elsevierViewall">The majority of women who require laser refractive surgery are between 20 and 30 years old, thus in many cases corneal surgery is followed by at least one pregnancy, with different possible ophthalmological effects.</p><p id="spar0025" class="elsevierStyleSimplePara elsevierViewall">The conclusions that may be derived from this study are that the assessment of the refractive changes in surgically operated corneas may be biomechanically weakened on being subjected to physiological hormone stimulation as it happens during gestation.</p>" ] "es" => array:2 [ "titulo" => "Resumen" "resumen" => "<span class="elsevierStyleSectionTitle">Objetivos</span><p id="spar0030" class="elsevierStyleSimplePara elsevierViewall">Diversos cambios oculares y complicaciones de la cirugía refractiva corneal del tipo queratectomía fotorrefractiva (PRK) asociados al embarazo han sido estudiados en los últimos años. Sin embargo, no se han descrito en gestantes las posibles complicaciones derivadas de la realización de cirugía tipo <span class="elsevierStyleItalic">laser in situ keratomileusis</span> (LASIK). Nuestro objetivo fue valorar cómo los cambios fisiológicos oculares secundarios a la gestación pueden alterar el estado refractivo en gestantes sometidas a cirugía tipo LASIK. Presentamos los resultados correspondientes a las modificaciones observadas entre los dos primeros trimestres de embarazo.</p> <span class="elsevierStyleSectionTitle">Métodos</span><p id="spar0035" class="elsevierStyleSimplePara elsevierViewall">Estudio observacional prospectivo en el que comparamos un grupo de estudio formado por 9 gestantes sometidas a cirugía refractiva LASIK previamente al embarazo y un grupo control con 9 gestantes con alteraciones refractivas no corregidas quirúrgicamente. Se realizó en los dos primeros trimestres de gestación un estudio de agudeza visual, máxima agudeza visual corregida, tonometría, características anatómicas oculares mediante biometría y estudio corneal y refractivo mediante Pentacam<span class="elsevierStyleSup">©</span>.</p> <span class="elsevierStyleSectionTitle">Resultados</span><p id="spar0040" class="elsevierStyleSimplePara elsevierViewall">Fueron observados cambios significativos en el cilindro y el equivalente esférico entre los dos primeros trimestres en ambos grupos. La agudeza visual y el componente esférico mostraron una clara tendencia al empeoramiento, mayor en el grupo de estudio. Las pacientes de este grupo con un defecto prequirúrgico mayor presentaron menores modificaciones en el curso de los dos primeros trimestres.</p> <span class="elsevierStyleSectionTitle">Conclusiones</span><p id="spar0045" class="elsevierStyleSimplePara elsevierViewall">Las mujeres con una mayor demandan de cirugía refractiva mediante láser se encuentran entre los 20 y los 30 años, con lo que en muchos casos la práctica de la cirugía corneal se sigue de, al menos, una gestación, con los efectos que ello puede conllevar a nivel ocular.</p><p id="spar0050" class="elsevierStyleSimplePara elsevierViewall">Las conclusiones que se pueden derivar de este proyecto suponen la valoración de los cambios refractivos que sufrirían las córneas operadas y por tanto biomecánicamente debilitadas, al ser sometidas a estímulos hormonales fisiológicos como los propios de la gestación.</p>" ] ] "NotaPie" => array:1 [ 0 => array:2 [ "etiqueta" => "☆" "nota" => "<p class="elsevierStyleNotepara">Please cite this article as: López-Prats MJ, et al. Influencia del embarazo sobre los parámetros refractivos tras cirugía <span class="elsevierStyleItalic">laser in situ keratomileusis</span>. Arch Soc Esp Oftalmol. 2012;87:173–8.</p>" ] ] "bibliografia" => array:2 [ "titulo" => "References" "seccion" => array:1 [ 0 => array:2 [ "identificador" => "bibs0005" "bibliografiaReferencia" => array:20 [ 0 => array:3 [ "identificador" => "bib0005" "etiqueta" => "1" "referencia" => array:1 [ 0 => array:2 [ "contribucion" => array:1 [ 0 => array:2 [ "titulo" => "Perinatal ophthalmology" "autores" => array:1 [ 0 => array:2 [ "etal" => false "autores" => array:1 [ 0 => "F.M. 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| Year/Month | Html | Total | |
|---|---|---|---|
| 2018 February | 1 | 0 | 1 |
| 2018 January | 20 | 0 | 20 |
| 2017 December | 7 | 0 | 7 |
| 2017 November | 14 | 3 | 17 |
| 2017 October | 16 | 6 | 22 |
| 2017 September | 14 | 9 | 23 |
| 2017 August | 23 | 3 | 26 |
| 2017 July | 25 | 4 | 29 |
| 2017 June | 29 | 6 | 35 |
| 2017 May | 16 | 2 | 18 |
| 2017 April | 26 | 1 | 27 |
| 2017 March | 32 | 14 | 46 |
| 2017 February | 20 | 4 | 24 |
| 2017 January | 31 | 2 | 33 |
| 2016 December | 54 | 7 | 61 |
| 2016 November | 30 | 4 | 34 |
| 2016 October | 38 | 7 | 45 |
| 2016 September | 26 | 5 | 31 |
| 2016 August | 25 | 4 | 29 |
| 2016 July | 24 | 2 | 26 |
| 2016 June | 14 | 3 | 17 |
| 2016 May | 21 | 11 | 32 |
| 2016 April | 10 | 8 | 18 |
| 2016 March | 9 | 6 | 15 |
| 2016 February | 11 | 6 | 17 |
| 2016 January | 14 | 7 | 21 |
| 2015 December | 16 | 5 | 21 |
| 2015 November | 18 | 3 | 21 |
| 2015 October | 23 | 9 | 32 |
| 2015 September | 22 | 6 | 28 |
| 2015 August | 12 | 14 | 26 |
| 2015 July | 8 | 8 | 16 |
| 2015 June | 7 | 11 | 18 |
| 2015 May | 22 | 7 | 29 |
| 2015 April | 26 | 9 | 35 |
| 2015 March | 18 | 6 | 24 |
| 2015 February | 9 | 1 | 10 |
| 2015 January | 22 | 6 | 28 |
| 2014 December | 28 | 4 | 32 |
| 2014 November | 18 | 1 | 19 |
| 2014 October | 21 | 8 | 29 |
| 2014 September | 27 | 8 | 35 |
| 2014 August | 13 | 3 | 16 |
| 2014 July | 11 | 0 | 11 |
| 2014 June | 7 | 2 | 9 |
| 2014 May | 15 | 4 | 19 |
| 2014 April | 15 | 9 | 24 |
| 2014 March | 9 | 3 | 12 |
| 2014 February | 11 | 4 | 15 |
| 2014 January | 6 | 4 | 10 |
| 2013 December | 9 | 3 | 12 |
| 2013 November | 17 | 7 | 24 |
| 2013 October | 14 | 3 | 17 |
| 2013 September | 10 | 2 | 12 |
| 2013 August | 9 | 5 | 14 |
| 2013 July | 3 | 1 | 4 |
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