A comparative study of Pentacam indices in various types and severities of refractive error in candidates for photorefractive keratectomy (PRK) surgery.

This study aimed to specify Pentacam indices in patients who suffered from different types of refractive error and underwent photorefractive keratectomy (PRK) surgery. It is a descriptive cross-sectional study carried out on 1125 patients (2215 eye samples) who underwent PRK surgery in the Noor Surgical Center of Ardabil, Iran, over a 5 year period (2014-2018). A particular checklist was provided to patients, which consisted of demographic data, pachymetry test, keratometry, refractive error, corneal-thickness indices, and corneal surface area indices. The data were analysed using the statistical analysis package of IBM® V25. The mean age of the participants in this study was 28.48±6.82 years, and the ratio of women to men was 66.4%. It was observed that the differences between angle, volume, the depth of the anterior chamber, IVA, and ISV were significant (P=0.00) when compared to each other in all types of refractive errors. High myopes had significantly higher Kmax front than low myopes (P=0.00). In astigmatism patients, the Kmax in front of the cornea in extreme type was significantly higher than in moderate (P=0.00) and high (P=0.01) types. High myopes had significantly lower Rmin than mild myopes (P=0.02), and extreme astigmatism had significantly lower Rmin than high (P=0.014) and moderate types (P=0.013). The data from this study revealed that in patients undergoing PRK surgery, some Pentacam indices could be related to some types of refractive error, and in some of these indices, there are statistically significant differences between different severities of refractive errors. Therefore, their preoperative evaluation is very important.

One-year follow-up of patients with hyperopia undergoing photorefractive keratectomy with Allegretto WaveLight Eye Q 400.

This study aimed to examine the effectiveness of photorefractive keratectomy (PRK) in treating patients with cycloplegic hyperopia from +1.00 to +7.00 diopter using Allegretto wave Eye Q 400. This study was conducted on 25 patients with cycloplegic astigmatism ≤1 diopter and cycloplegic hyperopia between +1.00 and +7.00 diopters in 47 eyes, who successively entered into the study within 6 months and underwent PRK. Prior to PRK surgery, all the patients were examined for cycloplegic refraction (astigmatism and hyperopia), slit lamp, keratometry, fundus, and best-corrected (BCVA) and uncorrected visual acuity (UCVA) testing. These examinations were repeated after 1 week, 1 month, 3 months, 6 months, and 1 year postoperatively. The mean preop UCVA of patients was 0.76±0.28 (ranging from 0.00 to 1.3), which reached 0.19±0.22 (ranging from 0.00 to 0.78) one year after the surgery (P=0.000). There was a significant correlation between increasing astigmatism and preop cycloplegic hyperopia >5 diopters (P=0.000), corneal ring haziness at 12th months (P=0.000), and 12 months cycloplegic residual hyperopia ≥2.00 diopters (P=0.000). 53.2% of the eyes (with a mean grade of 2.34) were detected with corneal ring haziness at 12th months, which was significantly correlated with 12 months residual cycloplegic hyperopia of ≥2.00 diopters (P: 0.000) and cycloplegic sphere above 5 diopters (P=0.006). Although the use of photorefractive keratectomy (PRK) with Allegretto Eye Q 400 is associated with a decrease in the mean cycloplegic and improved UCVA and BCVA, its use is not recommended in cases with preop cycloplegic hyperopia above 5 diopters due to the high rate of induction of astigmatism, corneal haziness, and regression of hyperopia.

Paired Opposite 4 mm Clear Corneal Incisions on Steep Meridian during Phacoemulsification.

PURPOSE: To evaluate the effect of opposite clear corneal incisions (OCCI) with 4 mm incisions on the steep meridian on postoperative astigmatism. METHODS: This study was performed on 64 eyes of 55 patients with keratometric astigmatism of ≥ 1 diopter (D) undergoing phacoemulsification. Patients were divided into two groups, with-the-rule (WTR) astigmatism and against-the-rule (ATR) astigmatism. Initial incisions in the WTR group were performed on the temporal side with 3.2 mm keratome and paired stab incisions were performed on the steep meridian. At the end of the surgery, stab incisions were enlarged to 4 mm. Follow-up visits were scheduled at 1, 3, 6, and 12 months postoperatively, which included refraction and keratometry. RESULTS: It was found that the mean preoperative keratometric astigmatism was 2.06 ± 0.86 D. The postoperative mean keratometric astigmatism was 1.3 ± 0.7 D after 1 month and 1.2 ± 0.7 D after 12 months. The mean astigmatism correction between the preoperative measure and that taken at 1 month was statistically significant (P = 0.001), but there was no significant change in the severity of astigmatism afterward. The mean surgically-induced astigmatism was found to be 1.99 ± 0.9 D. The 12-month changes of mean absolute astigmatism were: 1.06 ± 0.7 D in the WTR group, and 0.53 ± 0.7 D in the ATR group. The difference between the two groups was statistically significant (P = 0.02). CONCLUSION: Based on our findings, we posit that paired OCCI on the steep axis, using 4 mm incisions is an effective technique to correct preoperative astigmatism.

Pentacam Indices in Photorefractive Keratectomy Surgery.

Refractive eye surgeries are one of the most non-emergent ophthalmic surgeries due to the effect on the reduction of refractive errors, increasing visual acuity, enhancing the quality of vision, and indirectly increasing the quality of life of patients. The aim of this study was to determine Pentacam indices in the patients who underwent photorefractive keratectomy (PRK) during 2014-2018, as well as to show their correlation with the type of refractive error. This descriptive cross-sectional study was performed on 2215 eyes of 1125 patients undergoing PRK surgery. The patients' checklist, including demographic information, refractive index, keratometry, pachymetry, corneal surface zone indices, and progressive corneal thickness indices, was provided. All data were analyzed using the IBM SPSS software, version 25. The findings showed that there was a significant association between posterior corneal astigmatism (PCA) and anterior corneal astigmatism (ACA) (p=0.00). The mean Kmax front was recorded as 44.844 ± 1.58 D, which was significantly correlated with the type of refractive errors (p=0.00). According to the findings, there was a significant relationship between anterior chamber indices and refractive error types and their severity (p=0.00). There was also a significant correlation between the surface zone and keratoconus indices (i.e., index of surface variance - ISV, index of vertical asymmetry - IVA, index of height asymmetry - IHA, and minimum radius of curvature - Rmin) with refractive errors (p=0.00). The findings showed that some of the Pentacam indices could be related to the types of refractive errors in patients undergoing PRK surgery. Therefore, their evaluation is of great importance in this regard.

Femtosecond laser arcuate keratotomy for the correction of postkeratoplasty high astigmatism in keratoconus.

BACKGROUND: Astigmatism is the leading complication in visual recovery after penetrating keratoplasty (PKP) and deep anterior lamellar keratoplasty (DALK); in this study, we evaluated the outcome of femtosecond laser arcuate keratotomy (FLAK) after DALK and PKP in Iranian keratoconic patients. MATERIALS AND METHODS: In this prospective interventional case series, refractive and keratometric predictability, efficacy, and complications of FLAK for postkeratoplasty astigmatism in keratoconus were evaluated; 23 eyes of 23 consecutive patients (mean age of 32.43 ± 9.11 years) with high astigmatism were enrolled. The femtosecond laser performed paired 90°-angled arcuate incisions. RESULTS: Mean logarithm of the minimum angle of resolution of corrected and uncorrected visual acuity improved from preoperative values of 0.30 ± 0.18 and 0.85 ± 0.32 to 6-month values of 0.19 ± 0.17 and 0.65 ± 0.33, respectively (P < 0.05). Mean subjective astigmatism was 7.79 ± 2.64 diopter (D) preoperatively and 3.69 ± 2.25D at 6-month after surgery (P < 0.05). Surgically induced astigmatism was 9.27 ± 5.00D. Mean refractive spherical equivalent showed no significant (P = 0.69) hyperopic shift from - 4.21 ± 4.84D preoperatively to - 2.16 ± 6.09D postoperatively. Two (8.7%) microperforations were observed. CONCLUSION: FLAK is a relatively safe and effective method for the treatment of postkeratoplasty astigmatism.