Freedom from glasses is an increasingly important objective in cataract surgery. Current biometry techniques are precise in the correction of spherical refractive errors (myopia and hyperopia). However, a failure to correct refractive errors associated with astigmatism during cataract surgery may compromise the patient’s ability to be free of glasses.
The prevalence of corneal astigmatism is 95% in the population. Recent studies on different ethnic groups have confirmed that among cataract patients; approximately 60% present a prevalence of corneal astigmatism lower than 1.5 diopters (D) and greater than 0.75 D [
Among the treatment options for astigmatism, the toric intraocular lens (IOL) implantation is considered to be the most effective. Despite the excellent refractive results for toric lenses, which provide a visual acuity greater than 20/40 in more than 80% of cases and freedom from glasses in approximately 70% of cases [
Questionnaires have been developed to evaluate visual quality. One important instrument is the 25-item Visual Functioning Questionnaire (VFQ-25) produced by the National Eye Institute (NEI) of the United States. The questionnaire measures the influence of low vision and visual symptoms on specific areas of overall health, such as the emotional state and social functioning [
The objective of this study was to evaluate the refractive and the quality of vision outcomes of toric IOL implantation in patients with low astigmatism.
A single-arm, blinded, prospective study was performed. It included patients with cataracts who repeatedly visited a public hospital and underwent phacoemulsification, preoperative testing, and postoperative testing to measure improvements in distance best corrected (BCVA) and uncorrected (UCVA) visual acuity and contrast sensitivity (CS). The cataract classification, demographic and epidemiological data, and the visual quality questionnaire were performed.
The inclusion criteria were cataract diagnosis confirmed by biomicroscopy, corneal astigmatism range from 0.75 D to 1.5 D, and no previous ocular surgeries or ocular diseases that could compromise vision. The exclusion criteria were incomplete postoperative follow-up and intraoperative and postoperative complications like posterior capsule rupture and IOL misalignment.
Ethics committee approval for the study protocol was obtained. All patients signed an informed consent from before preoperative examinations.
The participants were evaluated before and after phacoemulsification. The following data were used in the study: UCVA and BCVA. CS. Refraction and spherical equivalent (SE). Score on the visual quality questionnaire.
The eye with the lower visual acuity was chosen in each patient.
This study was planned to identify a difference between questionnaire domains of at least 20 points, a level of significance of 5%, and 80% power. The standard deviation of a previous study was found to be 20 points, and this was therefore considered the minimal difference for the present study. The sample size was calculated after considering quantitative differences in the group before and after the intervention; accordingly, a minimum of 21 group participants were determined [
The same surgeon (E.S.B.) performed all surgeries. The surgery performed was phacoemulsification with a toric IOL implantation while the patient was under topical anesthesia. The main incision was a 2.5 mm clear corneal incision and it was made at 120°.
Rayner T Flex® IOLs were used in this study. This is an aspheric toric IOL, the IOL edges are squared, and its spherical aberration is neutral. Rayner T Flex has an optic body diameter of 5.75 or 6.25 mm and an overall length of 12 or 12.5 mm. The estimated A-constant is 118.9 and the spherical power ranges from +6 to +30 D and the cylinder power ranges from +1 to +6 D.
The data obtained by the IOL Master® 500 were inserted into the supplier’s website (RaynerCalculator®), and the intraocular lens that came closest to emmetropia was chosen. The surgically induced astigmatism was set at 0.3 D on the axis where the main incision was made.
The ophthalmologic evaluation was performed by a specialist (L.F.P.) and included the patient’s clinical history and the following exams: BCVA, UCVA, CS, tonometry, corneal topography, and retinal evaluation.
Biomicroscopy was performed to characterize cataracts by type (cortical, nuclear, or posterior subcapsular) and by grade (1 to 6) according to the international lens opacity classification system (LOCS III) [
The participants were evaluated on the first and seventh postoperative days, as well as 6 weeks after surgery.
The rotational stability of the IOL was evaluated 6 weeks postoperatively at the slit-lamp.
Visual acuity at 6 meters was measured using the Snellen chart; values were obtained up to the decimal notation.
This was measured using the Pelli–Robson chart. As recommended in the chart, the test was performed in a room with uniform lighting, and the table presented a mean luminance of 85 cd/m2. This situation was considered photopic, with an acceptable range of 60 to 120 cd/m2. This value was tested before the exam using a Gossen-Starlite meter. The patient was seated 1 meter from the table, thus allowing legibility of the optotypes, with a spatial frequency of approximately 1 cycle per degree (CPD) at this testing distance. The CS value considered was that which corresponded to the last group of three letters in which the patient was able to read at least two correctly.
Corneal astigmatism was evaluated using the IOL Master 500 device and 6 central points that were 2.5 mm in diameter.
Autorefraction was performed using the Huvitz HRK-7000® device with three measurements from which the mean value was calculated. This value was tested subjectively using the Bausch & Lomb® refractor.
The SE was calculated as the sum of the value of the spherical degree and half of the cylindrical degree.
The NEI VFQ-25 was used. The questionnaire is composed of 25 questions that evaluate various domains of quality of life and visual functioning, as outlined in Table
Domains considered in the NEI VFQ-25. The table reports the domains considered in the VFQ-25, the number of items considered in each domain, and their respective questions.
Domain | Number of items | Questions that assessed the domain |
---|---|---|
General health | 1 | 1 |
General vision | 1 | 2 |
Ocular pain | 2 | 4 and 19 |
Near activities | 3 | 5, 6, and 7 |
Distance activities | 3 | 8, 9, and 14 |
| ||
Social functioning | 2 | 11 and 13 |
Mental health | 4 | 3, 21, 22, and 25 |
Role difficulties | 2 | 17 and 18 |
Dependency | 3 | 20, 23, and 24 |
Driving | 3 | 15c, 16, and 16a |
Color vision | 1 | 12 |
Peripheral vision | 1 | 10 |
The patients themselves completed the questionnaires; they were aided by the specialist when questions arose.
Each question corresponds to a numerical value established so that a score of 100 represents the best conditions and a score of 0 reflects the worst conditions. The means were calculated according to the following equation: the mean is defined as the sum of the numerical values of each question within a given domain divided by the number of items evaluated in that domain [
The SPSS program, version 23.0 for Mac (SPSS Inc., Chicago, Illinois, USA), was used in the statistical analyses. The normality of the sample was evaluated using the Kolmogorov-Smirnov test. Noncontinuous variables were expressed as frequency, and the continuous variables were expressed as means and standard deviations. The variables were statistically analyzed using the paired
A total of 21 eyes from 21 patients were studied.
The mean age was
The results of cataract type as classified by the LOCS III were shown in Figures
Histogram classifying the type of cataract according to the LOCS III system; this figure shows that 15 (71.4%) were nuclear, 1 (4.8%) was cortical, and 5 (23.8%) were posterior subcapsular.
Histogram classifying the type of cataract according to the LOCS III system; this figure shows that 1 (4.8%) was of grade 1, 1 (4.8%) was of grade 2, 3 (14.3%) were of grade 3, 5 (23.8%) were of grade 4, 8 (38.1%) were of grade 5, and 3 (14.3%) of were grade 6.
As shown in Table
Visual function results. There was a statistically significant difference between the preoperative and postoperative periods when the following visual functions were compared (
Function | Preoperative mean | Preoperative SD | Postoperative mean | Postoperative SD | Range of means | |
---|---|---|---|---|---|---|
UCVA (decimal) | <0.20 | 0.17 | 0.80 | 0.19 | 0.60 | <0.001 |
BCVA (decimal) | 0.28 | 0.15 | 0.97 | 0.15 | 0.69 | <0.001 |
CS (log) | 1.22 | 0.32 | 1.74 | 0.19 | 0.52 | <0.001 |
UCVA = uncorrected visual acuity; BCVA = best-corrected visual acuity; CS = contrast sensitivity.
Histogram showing the distribution of postoperative UCVA: 86% of the participants exhibited vision acuity of 0.6 or higher.
The mean preoperative and postoperative BCVA were
The mean BCVA in the contralateral eye was
The mean preoperative and postoperative photopic CS were
The mean preoperative corneal cylinder (IOL Master) was
The mean preoperative and postoperative refractive astigmatism were −
Refraction results. The table shows a statistically significant variation in terms of preoperative and postoperative refractive cylinder values, as well as a lack of statistically significant differences between preoperative and postoperative spherical equivalence.
Field | Preoperative mean | Preoperative SD | Postoperative mean | Postoperative SD | Mean variation | |
---|---|---|---|---|---|---|
Refractive cylinder | −1.23 | 0.53 | −0.34 | 0.39 | 0.89 | <0.001 |
Spherical equivalence | −0.17 | 2.33 | −0.52 | 0.35 | 0.35 | 0.517 |
Refractive cylinder boxplot showing statistically significant variation between preoperative and postoperative refractive cylinder values. Preoperative mean was −1.23 D and postoperative mean was −0.34 D.
Histogram of postoperative refractive cylinder showing that 86% of the patients presented a postoperative refractive cylinder lower than −0.5 D.
The questionnaire results are presented in Table
Results of the NEI VFQ-25 showing positive variation with statistical significance between preoperative and postoperative values in all fields of the questionnaire and in total score.
Field | Preoperative mean | Preoperative SD | Postoperative mean | Postoperative SD | Mean variation | |
---|---|---|---|---|---|---|
General health | 42.85 | 17.93 | 63.09 | 24.52 | 20.23 | 0.004 |
General vision | 42.85 | 14.54 | 72.38 | 17.50 | 29.52 | <0.001 |
Ocular pain | 57.73 | 26.36 | 86.90 | 22.17 | 29.16 | <0.001 |
Near activities | 34.52 | 17.92 | 77.77 | 20.12 | 43.25 | <0.001 |
Distance activities | 40.07 | 25.76 | 84.12 | 15.11 | 44.04 | <0.001 |
Social functioning | 57.73 | 23.54 | 92.85 | 13.44 | 35.11 | <0.001 |
Mental health | 35.11 | 24.16 | 75.89 | 22.38 | 40.77 | <0.001 |
Role difficulties | 36.30 | 22.32 | 84.52 | 18.91 | 48.21 | <0.001 |
Dependency | 54.36 | 31.36 | 90.07 | 18.37 | 35.71 | <0.001 |
Color vision | 64.28 | 29.12 | 97.61 | 7.51 | 33.33 | <0.001 |
Peripheral vision | 55.95 | 20.77 | 88.09 | 20.33 | 32.14 | <0.001 |
Total | 43.20 | 15.76 | 79.70 | 10.11 | 36.49 | <0.001 |
A significant linear correlation was observed between the variation in UCVA, BCVA, and CS and variation in VFQ results (Table
Correlations. The table shows the correlation coefficients, all of which were statistically significant between the variations in questionnaire values and UCVA, BCVA, and CS values, which were 0.548, 0.508, and 0.409, respectively. This result demonstrates a direct and positive association between the items evaluated.
Field correlated with the questionnaire | Correlation | |
---|---|---|
UCVA | 0.548 | 0.005 |
BCVA | 0.508 | 0.009 |
CS | 0.409 | 0.033 |
UCVA = uncorrected visual acuity; BCVA = best-corrected visual acuity; CS = contrast sensitivity.
Scatterplot showing the significant correlation between UCVA and total questionnaire score as per the Pearson’s coefficient of 0.548 (
Scatterplot showing the significant correlation between BCVA and total questionnaire score as per the Spearman coefficient of 0.508 (
Scatterplot showing the significant correlation between CS and total questionnaire score as per the Pearson coefficient of 0.409 (
Phacoemulsification currently has a refractive function in addition to simple cataract removal. It is important to note that an astigmatism greater than 0.5 D is found in approximately 80% of the cataract patient population [
The study sample was composed of 61.9% females and 38.1% males, and the mean patient age was 68.9 years. This sample was similar to those in other studies that have evaluated cataracts in the elderly [
With regard to cataract classification, most patients exhibited nuclear cataracts (71.4%), followed by posterior subcapsular cataracts (23.8%) and cortical cataracts (4.8%). According to Prokofyeva et al., the risk factors for nuclear cataracts are an unbalanced diet and poor socioeconomic conditions. This finding explains the higher prevalence of nuclear cataracts among the participants in the present study, which was performed in a developing country [
UCVA is an important parameter when evaluating the refractive effectiveness of cataract surgery. In the present study, the mean postoperative UCVA was 0.8, with 47% of patients experiencing vision that was better than or equal to 0.8 and 96% experiencing vision that was better than or equal to 0.5. Recent reviews of the literature on the surgical outcomes of toric IOLs have presented results in which UCVA greater than or equal to 0.8 was observed in 23% to 100% of cases and in which UCVA greater than or equal to 0.5 was observed in 68% to 100% of cases [
In this study, the mean postoperative BCVA was 0.97, with 100% of patients exhibiting BCVA greater than 0.8. Preoperative and postoperative variations were found to be statistically significant (
An important result of the present study was the sample’s mean corneal and refractive astigmatisms of
The mean spherical equivalent values increased without statistical significance (from
A search of the literature on PubMed in August 2016 (using the keywords “VFQ 25” and “toric IOL”) did not reveal articles in which the VFQ 25 was applied to patients who had undergone cataract surgery with toric IOL implants. However, greater satisfaction was reported among patients who had received the toric IOL implantation as opposed to those who had received the spheric IOL implantation [
More important than refractive, visual, and quality of life data is the interpretation of these findings based on their correlations. The current study revealed statistically significant correlations between patient satisfaction and the visual function items.
When the variation in the NEI VFQ 25 and CS was analyzed, Pearson’s coefficient was 0.409 (
When variations in BCVA were correlated with the results of the questionnaire, Spearman’s correlation coefficient was 0.508 (
The lack of a statistically significant difference between UCVA of the eye included in the study and the contralateral eye decreased the influence of visual acuity of the contralateral eye as a confounding factor when the benefit of the surgery was analyzed in terms of the results of the quality of life questionnaire.
Thus, according to the results presented here, cataract surgery with a toric IOL implant to achieve better visual and refractive results is associated with a greater patient perception of visual quality and a greater quality of life.
Patients with low astigmatism who underwent phacoemulsification with a toric IOL implant experienced significant decrease in refractive astigmatism and improvement in their quality of life; this finding positively correlated with variations in CS, UCVA, and BCVA.
The study protocol was submitted to the ethics committee of the institution. All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
The informed consent was obtained from all individual participants included in the study.
The authors declare that they have no conflict of interests regarding the publication of this paper.