Mini-incision cataract surgery and toric lens implantation for the reduction of high myopic astigmatism in patients with pellucid marginal degeneration

Purpose

To evaluate the clinical outcomes, safety, and efficacy of cataract surgery with the implantation of a toric intraocular lens (IOL) in eyes with stable pellucid marginal degeneration (PMD).

Methods

Eleven eyes (eight patients) diagnosed as stable PMD and cataract underwent mini-incision 2.2 mm cataract surgery followed by the implantation of hydrophobic toric aspheric IOL (AcrySof IQ Toric IOL, Alcon, Fort Worth, TX, USA). Perioperative variables of interest included uncorrected (UDVA) and corrected (CDVA) distance visual acuities, manifest refraction, and corneal topography. Paired samples t-tests were used to analyze preoperative and postoperative visual acuity, astigmatism, and spherical equivalent (SE) parameters. Follow-up was 6 months.

Results

The mean CDVA was 0.62±0.26 logMAR preoperatively and 0.07±0.07 logMAR postoperatively. The mean preoperative sphere and cylinder was −3.14±3.58D and −4.84±2.02D, respectively. The mean postoperative manifest refractive sphere and cylinder was −0.30±0.51D and −0.81±1.51D, respectively. There was a significant reduction in refractive astigmatism after toric IOL implantation (P<0.002). The toric IOL axis rotation was <5° in all cases at the final follow-up.

Conclusions

Implantation of hydrophobic toric IOL was a safe and effective surgical procedure to correct mild to moderate stable PMD.     

Clinical evaluation of two types of intracorneal ring segments (ICRS) for keratoconus

Purpose

To compare the outcome measures following implantation of two types of ICRS.

Methods

Forty-four eyes of keratoconic patients (aged 18–50 years) were randomly assigned to femtosecond laser-assisted Keraring ICRS (Group A) or MyoRing (Group B) implantation. Uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, keratometry (K), and aberrations were compared preoperatively, at 3 and 6 months postoperatively. A survey was conducted to assess patient’s satisfaction, 6 months postoperatively.

Results

In Groups A (n = 26) and B (n = 18), UDVA was increased (P < 0.05), but CDVA increased only in Group A (P < 0.05) 6 months postoperatively. The mean K was reduced by 4.55 D (P < 0.0001) in Group A and 6.51 D (P < 0.001) in Group B. Six months postoperatively, the mean refraction spherical equivalent (MRSE) decreased by 2.90 and 3.60 D in Groups A and B, respectively (P < 0.0001). Between groups, coma was more reduced (P = 0.035) in Group B than A, 6 months postoperatively. On motivation for surgery, 88.9% of patients’ ranked “desire to improve unaided vision” and “relief from glasses” (77%) topmost. Seventy-seven (77%) of Group A and 89% of Group B patients were satisfied with their unaided vision at the final visit, after 6 months.

Conclusions

KeraRing (A) and MyoRing (B) corneal implants both performed well in improving vision and stabilising the cornea. Implantation of the MyoRing caused greater reduction in coma and better patient satisfaction, but CDVA improved only in the Keraring group, at the final visit.

     

Factors affecting outcomes of corneal collagen crosslinking treatment

Purpose

To assess the effects of preoperative patient characteristics on clinical outcomes of corneal crosslinking (CXL) treatment in patients with progressive keratoconus.

Methods

This retrospective study comprised 96 eyes of 96 patients who had unilateral CXL treatment for progressive keratoconus. All patients underwent a complete ophthalmological examination and corneal topography at baseline and 1 year. Subgroup analyses were performed according to the age (<30 and≥30 years), gender, preoperative corrected distance visual acuity (CDVA, <0.3 and ≥0.3 logMAR (log of the minimum angle of resolution)), preoperative maximum keratometry (K, <54 and ≥54 D), baseline topographic cone location (central, paracentral, and peripheral), and preoperative thinnest pachymetry (<450 and ≥450 μm) to determine the associations between preoperative patient characteristics and outcomes (changes in visual acuity and maximum keratometry) of CXL treatment.

Results

In the entire study population, mean CDVA and maximum K significantly improved after CXL treatment (P<0.001). Patients with a preoperative CDVA of 20/40 Snellen equivalent or worse (≥0.3 logMAR) experienced more visual improvement after CXL treatment (P<0.001). However, an age ≥30 years and a baseline thinnest pachymetry less than 450 μm were found significantly associated with more flattening in maximum keratometry (P=0.024, P=0.005 respectively). Gender, preoperative maximum K, and baseline topographic cone location did not show significant effect on postoperative visual acuity and maximum keratometry (P>0.05).

Conclusions

In patients with progressive keratoconus, age, baseline visual acuity, and baseline thinnest pachymetry seem to affect the success of the CXL treatment.     

Corneal collagen crosslinking for corneal ectasia of post-LASIK: one-year results

AIM: To evaluate the efficacy and safety of corneal collagen crosslinking (CXL) to prevent the progression of post-laser in situ keratomileusis (LASIK) corneal ectasia. METHODS: In a prospective, nonrandomized, single-centre study, CXL was performed in 20 eyes of 11 patients who had LASIK for myopic astigmatism and subsequently developed keratectasia.The procedure included instillation of 0.1% riboflavin-20% dextrane solution 30 minutes before UVA irradiation and every 5 minutes for an additional 30 minutes during irradiation. The eyes were evaluated preoperatively and at 1-, 3-, 6-, and 12-month intervals. The complete ophthalmologic examination comprised uncorrected visual acuity, best spectacle-corrected visual acuity, endothelial cell count, ultrasound pachymetry, corneal topography, and in vivo confocal microscopy. RESULTS: CXL appeared to stabilise or partially reverse the progression of post-LASIK corneal ectasia without apparent complication in our cohort. UCVA and BCVA improvements were statistically significant(P＜0.05) beyond 12 months after surgery (improvement of 0.07 and 0.13 logMAR at 1 year, respectively). Mean baseline flattest meridian keratometry and mean steepest meridian keratometry reduction (improvement of 2.00 and 1.50 diopters(D), respectively) were statistically significant (P＜0.05) at 12 months postoperatively. At 1 year after CXL, mean endothelial cell count did not deteriorate. Mean thinnest cornea pachymetry increased significantly. CONCLUSION: The results of the study showed a long-term stability of post-LASIK corneal ectasia after crosslinking without relevant side effects. It seems to be a safe and promising procedure to stop the progression of post-LASIK keratectasia, thereby avoiding or delaying keratoplasty.     

Treatment of moderate to severe keratoconus with 6-mm Intacs SK

AIM: To evaluate the effect of Intacs SK corneal ring segment implant for treatment of patients with moderate to severe keratoconus, who have clear central cornea and cannot tolerate contact lens. METHODS: In this prospective, non-comparative, interventional case series study performed in Dena Hospital, Shiraz, Iran, thirty-seven eyes of thirty-six patients with moderate to severe keratoconus, clear central cornea, and contact lens intolerance were enrolled and underwent Intacs SK corneal ring segment implantation. Preoperatively, uncorrected distance visual acuity (UCDVA), best-corrected distance visual acuity (BCDVA), central corneal thickness(CCT) and average keratometry (Av-K) were measured and compared with post-operative results at one week, one month, three months, and six months. RESULTS: Mean preoperative UCDVA and BCDVA were (1.32±0.31)logMAR and (1.07±0.27)logMAR, respectively. Av-K was (52.13±0.39)D, and the CCT was (432±39.5)μm. Post-operative examinations showed a clinically significant improvement in both UCDVA and BCDVA (P<0.001). There was also a significant effect based on the time of assessment on both UCDVA and BCDVA and both parameters had a continuous improvement during the follow-up period. Three months after operation there was a statistical significant reduction of Av-K (P=0.0001), but there were no significant changes in CCT (P=0.149). CONCLUSION: Intacs SK corneal ring segment implants seem to be a safe and effective treatment option for patients who have keratoconus, clear central cornea, and contact lens intolerance.     

The biomechanical properties of the cornea in patients with systemic lupus erythematosus

Pupose:

The purpose of this study was to compare the biomechanical properties of the cornea and intraocular pressure (IOP) between patients with systemic lupus erythematosis (SLE) and age-matched controls.

Patients and Methods:

In this prospective study, 30 healthy individuals (control group) and 30 patients with SLE (study group) underwent Reichert ocular response analyzer (ORA) measurements. In the right eye of each participant, the corneal hysteresis (CH), corneal resistance factor (CRF), and Goldman-related IOP (IOPg) were recorded using the ORA.

Results:

Mean CH, CRF, IOPg were significantly different between groups. Mean CH was 10.2±0.6 mm Hg in the study group and 11.3±1.3 in the control group (P=0.02); mean CRF was 9.7±1.1 mm Hg and 11.9±1.5 mm Hg, respectively (P=0.001). Mean IOP_g was 13.9±2.9 mm Hg in the study group and 16.9±2.6 mm Hg in the control group (P=0.001).

Conclusion:

The biomechanical properties of the cornea are altered in patients with SLE compared with normal controls. These findings should be taken into account when measuring IOP values in patients with SLE as IOP readings may be underestimated in SLE eyes.     

Optical quality of toric intraocular lens implantation in cataract surgery

AIM: To analyze the optical quality after implantation of toric intraocular lens with optical quality analysis system. METHODS: Fifty-two eyes of forty-four patients with regular corneal astigmatism of at least 1.00 D underwent implantation of AcrySof toric intraocular lens, including T3 group 19 eyes, T4 group 18 eyes, T5 group 10 eyes, T6 group 5 eyes. Main outcomes evaluated at 3mo of follow-up, included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), residual refractive cylinder and intraocular lens (IOL) axis rotation. Objective optical quality were measured using optical quality analysis system (OQAS Ⅱ?, Visiometrics, Spain), included the cutoff frequency of modulation transfer function (MTFcutoff), objective scattering index (OSI), Strehl ratio, optical quality analysis system value (OV) 100%, OV 20% and OV 9% [the optical quality analysis system (OQAS) values at contrasts of 100%, 20%, and 9%]. RESULTS: At 3mo postoperative, the mean UDVA and CDVA was 0.18±0.11 and 0.07±0.08 logMAR; the mean residual refractive cylinder was 0.50±0.29 D; the mean toric IOL axis rotation was 3.62±1.76 degrees, the mean MTFcutoff, OSI, Strehl ratio, OV 100%, OV 20% and OV 9% were 22.862±5.584, 1.80±0.84, 0.155±0.038, 0.76±0.18, 0.77±0.19 and 0.78±0.21. The values of UDVA, CDVA, IOL axis rotation, MTFcutoff, OSI, Strehl ratio, OV100%, OV20% and OV9% depending on the power of the cylinder of the implantation were not significantly different (P>0.05), except the residual refractive cylinder (P<0.05). CONCLUSION: The optical quality analysis system was useful for characterizing the optical quality of AcrySof toric IOL implantation. Implantation of an AcrySof toric IOL is an effective and safe method to correct corneal astigmatism during cataract surgery.     

Satisfaction Level of Physicians Who Have Undergone Corneal Refractive Surgery

Purpose

To evaluate the levels of satisfaction among physicians who have undergone corneal refractive surgery.

Methods

This study included 212 eyes of 107 consecutive patients who underwent laser in situ keratomileusis or laser sub-epithelial keratomileusis surgery. Patients were divided into two groups: one group of physicians and one group of other healthcare workers (HCWs). The physicians'' group was also subdivided into two different groups: surgeons or doctors using microscopes and medical physicians. The main outcome measures were scale scores obtained by using the Visual Function Index-14 questionnaires; uncorrected distance visual acuity (UDVA), residual spherical equivalent (SE), optical zone diameter, and residual corneal thickness were also compared between the groups.

Results

No significant differences in preoperative parameters, with the exception of the ratio of types of refractive surgery, were noted between the physicians and the HCWs group. Additionally, no differences between the groups were noted in the postoperative UDVA, residual SE, optical zone diameter, residual corneal thickness, and level of satisfaction. When comparing the two subgroups of physicians, the differences in satisfaction rates were not statistically significant, even in terms of the performance of delicate manual work.

Conclusions

No statistically significant differences in the clinical outcomes and satisfaction scores were detected after surgery between the physicians and HCWs groups, nor were any significant differences detected between the surgeons and medical physicians groups. Corneal refractive surgery can conceivably be recommended even for physicians who perform intensive near vision-dependent activities and delicate operations.     

Comparation of the new rebound tonometer IOPen and the Goldmann tonometer, and their relationship to corneal properties

Purpose

To compare the intraocular pressures (IOPs) obtained with the IOPen rebound tonometer, Goldmann applanation tonometer (GAT) and the ocular response analyzer (ORA) and investigate the effects of corneal biomechanical properties on IOPen measurements.

Methods

A total of 198 normal eyes were included in this cross-sectional and randomized study. Three measurements were taken using IOPen. Agreement between tonometers was calculated using the Bland and Altman limits of agreement (LoA) analysis.

Results

The median IOPen IOP was 3 mm Hg below the GAT (P<0.001), 3 mm Hg below the ORA IOP similar to Goldmann (IOPg), and 3 mm Hg below the ORA IOP corrected using corneal parameters (IOPcc)(P<0.01). The LoA width between the IOPen and GAT IOPs varied between 13.92 (mean IOPen IOP) and 15.99 mm Hg (third IOPen measurement). The central corneal thickness (CCT) was unrelated to IOPen measurements (P>0.05). Corneal hysteresis (CH) and corneal rigidity factor (CRF) were correlated with IOPen and GAT.

Conclusions

IOPen underestimated the IOP compared with GAT and ORA. The effect of measurement quality or measurement order on IOPen was low. CCT did not affect the IOPen, but the CH and CRF did. The LoA width between the IOPen and GAT IOPs was higher than between the ORA IOPg or ORA IOPcc and GAT IOPs.     

Factors influencing corneal flap thickness in laser in situ keratomileusis with a femtosecond laser

Purpose

To evaluate factors responsible for the variability between intended and achieved corneal-flap thickness during femtosecond laser-assisted laser in situ keratomileusis (LASIK).

Methods

A prospective, nonrandomized, case study was performed on 35 eyes of 18 consecutive patients who underwent LASIK surgery using the 60 kHz femtosecond laser microkeratome. Eyes were assigned to three different thickness groups, with 110-, 120-, or 130-µm cut depths. Anterior segment optical coherence tomography was used to assess the morphology of 35 LASIK flaps at postoperative one week postoperatively. The flap thickness was assessed at seven measuring points across each flap. Patient age, preoperative spherical equivalent, manual keratometry, preoperative central pachymetry, and regional variability of the cornea were evaluated to determine where they influenced the achieved corneal flap thickness.

Results

Cuttings of all flaps were easily performed without any intraoperative complications. Flap-thickness measurements had a mean of 115.21 ± 4.98 µm (intended thickness, 110 µm), 121.90 ± 5.79 µm (intended, 120 µm), and 134.38 ± 5.04 µm (intended, 130 µm), respectively. There was no significant difference between the 110-µm and 120-µm groups when compared with the 130-µm group (one-way analysis of variance test, p > 0.05). Patients'' age, preoperative spherical equivalent, manual keratometry, and preoperative central pachymetry did not affect the achieved flap thickness (Pearson correlations test, p > 0.05). The reproducibility of flap thickness in the central 1.5-mm radius area was more accurate than that in the peripheral 3.0 to 4.0-mm radius area (paired samples t-test, p < 0.05).

Conclusions

Femtosecond laser-assisted LASIK is likely to reproduce a reliable thickness of the corneal flap, which is independent of corneal shape factors or refractive status. Future studies should focus on variations in corneal biomechanical factors, which may also play an important role in determining flap thickness.     

Assessment of visual outcomes of cataract surgery in Tujia nationality in Xianfeng County, China

AIM: To evaluate the visual outcome and factors influencing visual outcome of manual small incision cataract surgery (MSICS) in the rural area in the Xianfeng County. METHODS: Eighty-two eyes of 82 patients who underwent cataract surgery performed by using MSICS technique were identified. Data collected included each patient’s age, gender, the level of education. Uncorrected and corrected distance visual acuity (UDVA and CDVA) at presentation and at 1, 6, 8wk postoperatively, pre-existing eye disease, operative findings and complications, the risk factors were evaluated. RESULTS: In 82 patients, the average age was 69.6±0.6y, illiterate were 52 (63.4%). Of 82 eyes, pseudophakia was present in 77 eyes (93.9%). At 1wk postoperatively, 47 eyes (57.3%) had the UDVA of ≥6/18, and 52 eyes (63.4%) had the CDVA of ≥6/18. At 6 to 8wk postoperatively, 50 eyes (61.0%) had UDVA of ≥6/18, and 57 eyes (69.5%) had the CDVA of ≥6/18. Postoperative visual status was significantly related to the co-morbidities, such as corneal pathology, glaucoma (P<0.001). Operative complications, such as posterior capsule opacity and cystoid macular edema were main operative cause for the poor visual outcome. CONCLUSION: MSICS provides a good visual recovery in our study but the vision outcome did not fulfill the standards proposed by WHO, which highlights the need for an improvement in local socioeconomic understanding, population education and surgery quality.     

Association between corneal biomechanical properties and myopia in Chinese subjects

Purpose

To examine the relationship between corneal biomechanical properties and the degree of myopia.

Methods

Chinese subjects (n=172, age: 11−65 years) were divided into diagnostic groups with non-myopia (spherical equivalence (SE)>−0.50 D), low (−3.00≤SE≤−0.50 D), moderate (−6.00≤SE<−3.00 D), and high myopia (SE<−6.00 D). Only the right eye of each subject was analyzed. Central corneal thickness (CCT) was measured by optical coherence tomography. An ocular response analyzer was used to measure corneal hysteresis (CH), corneal resistance factor (CRF), intraocular pressure (IOP), and corneal compensated IOP (IOPcc). Refraction was measured by both automated and subjective refractometry and expressed as SE.

Results

CH was significantly lower in high myopia compared with both low and non-myopia (P≤0.002). CCT was 1.5 times more correlated to CH variation compared with refraction. Similarly, CRF was four times more dependent on CCT than refraction. CH (P<0.001) or CRF (P=0.005) was positively correlated to refraction. Both IOP and IOPcc were negatively correlated to refraction (P<0.001), respectively.

Conclusions

CH decreases only in high myopia. Refraction is positively correlated to both CH and CRF but negatively correlated to both IOP and IOPcc. These results indicate that the mechanical strength in anterior segment of the eye is compromised in high myopia. In addition, high myopia may increase the risk of glaucoma.     

Comparison of two types of visual quality analyzer for the measurement of high order aberrations

AIM: To compare the difference and agreement of KR-1W and iTrace for measurement of high order aberrations. METHODS: KR-1W and iTrace were respectively used in a group of healthy people (40 volunteers, 32 eyes) to measure the high order aberration (HOA) of corneal, internal and total ocular. The clinical difference and agreement of two instruments were respectively evaluated by paired-samples t-test and Bland-Altman analysis. RESULTS: The paired-samples t-test showed that the corneal HOA measured by the two instruments had no statistical differences (P＞0.05); but the internal and total ocular HOA had significant statistical differences (P＜0.05), and the mean results measured by iTrace were higher than that of KR-1W. However, Bland-Altman analysis revealed that the HOA of corneal and internal were all in 95% limits of agreement; and just one point of total ocular HOA was beyond the 95% limits of agreement. CONCLUSION: KR-1W and iTrace were consistent well in the measurement of corneal, internal and total ocular HOA, especially for the cornea.     

Astigmatism and biometric optic components of diode laser-treated threshold retinopathy of prematurity at 9 years of age

Purpose

To assess the prevalence of astigmatism and its relationship with biometric optic components in preterm school children with diode laser-treated threshold retinopathy of prematurity (ROP).

Methods

A prospective, cross-sectional study in which cycloplegic keratometry, refraction, and ultrasound biometric measurement of optic components were performed on 24 consecutive preterm children with diode laser-treated threshold ROP at the age of 9 years. The study results were compared with data on 1021 age-matched full-term control children from a national survey.

Results

The laser-treated eyes had a mean astigmatism of 3.47 D, with a mean spherical equivalent of −4.49 D. Of the 46 eyes studied, 98% of eyes showed astigmatism ≥0.5 D and 50% had high astigmatism (>3.0 D). Most astigmatic eyes (97.7%) showed with-the-rule astigmatism, with the mean plus cylinder axis at 89.30^o. Further correlation analysis showed the astigmatism in refraction was highly correlated with the corneal astigmatism (r=0.921, P<0.001) and the vertical corneal curvature (r=0.405, P=0.005). There was significantly steeper vertical corneal curvature (P=0.003) and flatter horizontal corneal curvature (P=0.031) in eyes with laser-treated ROP when compared with age-matched full-term controls. The eyes with laser-treated ROP also show significantly thicker lens (3.93 mm) and shallower anterior chamber depth (ACD; 2.92 mm) than full-term controls (P<0.001).

Conclusions

There is significantly higher prevalence and greater magnitude of astigmatism in eyes with laser-treated threshold ROP compared with full-term controls. The steeper vertical corneal curvature component contributes to the increased astigmatism in eyes with laser-treated ROP.     

Analysis of changes in crystalline lens thickness and its refractive power after laser in situ keratomileusis

AIM: To evaluate changes in the anterior chamber depth (ACD), crystalline lens thickness (LT) and its refractive power after laser in situ keratomileusis (LASIK). METHODS: In all cases, the preoperative and postoperative central ACD which were measured with Pentacam, Orbscan, IOL-Master and A-scan ultrasonography, central corneal true net power which was measured with the Pentacam, Orbscan and IOL-Master, axial length (AL) which was measured with IOL-Master and LT which was measured with the A-scan ultrasonography were compared using the paired sample t test. Ocular refractive errors and lens refractive power at corneal plane were calculated and their correlations were also evaluated before and after LASIK. RESULTS: At 1 week after LASIK, LT and crystalline lens refractive power at corneal plane (Dlens) which were associated with the IOL-Master and Pentacam increased significantly (P≤0.005), ACD decreased significantly (P≤0.001), but no significant increase was observed in the Dlens which was associated with the Orbscan (P=0.261). Significant correlations between the changes in the ocular refractive errors and Dlens which were associated with the Pentacam were observed at 1 week and 6 months after LASIK (P=0.028; P=0.001). CONCLUSION: LT increased significantly after LASIK, and this might partially lead to ACD decrease, Dlens increase and a small quantity of myopic regression.     

Influence of cycloplegia with topical cyclopentolate on higher-order aberrations in myopic children

Purpose

To investigate the influence of cycloplegia with topical cyclopentolate on wavefront aberrations in myopic children.

Design

This is a prospective, comparative study.

Methods

Twenty-eight myopic children with a mean age of 7.25±2.55 were enrolled in this study. We evaluated refraction and wavefront aberrations before and after cycloplegia with 1% cyclopentolate hydrochloride. Ocular and corneal aberrations were simultaneously measured and compared with each other. Individual Zernike components were also analyzed up to the sixth order. All these parameters were compared before and after cycloplegia.

Results

Ocular higher-order aberrations (HOAs) significantly increased after cycloplegia (P=0.012 for spherical-like and P=0.015 for total HOAs). Corneal HOAs did not change after cycloplegia. When corneal and ocular HOAs were compared, the ocular HOAs were significantly smaller than the corneal HOAs in spherical-like aberrations (P<0.001) and total HOAs (P=0.006). As for individual Zernike components, ocular aberration generally showed smaller or equivalent values in comparison with corneal aberration. In addition, each Zernike component showed a large standard deviation.

Conclusions

Internal optics compensates for corneal HOAs in myopic children, and paralysis of tonic accommodation with cyclopentolate considerably affects ocular HOAs. However, inter-individual variation in each Zernike component is quite large in myopic children.     

Evaluation of intrastromal corneal ring segments for treatment of keratoconus with a mechanical implantation technique

Purpose:

To evaluate the clinical outcomes of intrastromal corneal ring segment (ICRS) implantation in patients with keratoconus using a mechanical implantation technique.

Materials and Methods:

Thirty eyes of 17 patients with keratoconus were enrolled. ICRSs (Keraring) were implanted after dissection of the tunnel using Tunc''s specially designed dissector under suction. A complete ophthalmic examination was performed, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent, keratometric readings, inferosuperior asymmetry index (ISAI), and ultrasound pachymetry. All 3-, 6-, and 12-month follow-ups were completed, and statistical analysis was performed.

Results:

The mean preoperative UDVA for all eyes was 1.36 ± 0.64 logMAR. At 12 months, the mean UDVA was 0.51 ± 0.28 logMAR (P = 0.001), and the mean preoperative CDVA was 0.57 ± 0.29 logMAR, which improved to 0.23 ± 0.18 (P = 0.001) at 1 year. There was a significant reduction in spherical equivalent refractive error from –6.42 ± 4.69 diopters (D) preoperatively to –1.26 ± 1.45 D (P = 0.001) at 1 year. In the same period, the mean K-readings improved from 49.38 ± 3.72 D to 44.43 ± 3.13 D (P = 0.001), and the mean ISAI improved from 7.92 ± 3.12 to 4.21 ± 1.96 (P = 0.003). No significant changes in mean central corneal thickness were observed postoperatively. There were no major complications during and or after surgery.

Conclusion:

ICRS implantation using a unique mechanical dissection technique is a safe and effective treatment for keratoconus. All parameters improved by the 1-year follow-up.     

A new, pachymetry-based approach for diagnostic cutoffs for normal, suspect and keratoconic cornea

Purpose

To analyze whether an association exists between keratometric and pachymetric changes in the cornea, and whether it can be used to create pachymetric cutoff criteria secondary to keratometric criteria.

Methods

In this cross-sectional study, 1000 candidates presenting to the refractive surgery services of a tertiary care hospital underwent bilateral Orbscan IIz (Bausch and Lomb) assessment along with other ophthalmic evaluation.

Results

Stepwise regression analysis-based models showed that simulated keratometry (simK) astigmatism was significantly predicted by the minimum corneal thickness (MCT) and difference between central and MCT (δCT), mean SimK by the MCT and δCT, and maximum keratometry in the central 10-mm zone by the MCT and δCT (P<0.001). The mean MCT values were 542.5±39.6, 539.9±39.2, 524.2±49.5, and 449.3±73.7 μm for flatter normal (<44 D), steeper normal (≥44 D), keratoconus suspect and keratoconic eyes, respectively (P<0.001). The mean differences between central corneal thickness and MCT (δCT) were 12.2±7.1 μm, 12.4±7.4 μm, 14.4±8.9 μm and 23.2±10.1 μm for the flatter normal, steeper normal, keratoconus suspect, and keratoconic eyes, respectively (P<0.001). Mean and 2SD cutoff were used to suggest that a cornea having MCT<461 μm or δCT>27 μm has only a 2.5% chance of being normal and not a keratoconus suspect or worse.

Conclusion

Pachymetric diagnostic cutoffs can be used as adjuncts to the existing topographic criteria to screen keratoconus suspect and keratoconic eyes.     

Evaluation of intrastromal corneal ring segments for treatment of post-LASIK ectasia patients with a mechanical implantation technique

Aim:

To evaluate the clinical outcomes of Keraring segment implantation in patients with post- laser-assisted in situ keratomileusis (LASIK) ectasia, using a mechanical implantation technique.

Materials and Methods:

Twelve eyes of 10 patients with post-LASIK ectasia were enrolled. Intracorneal ring segments (ICRS) were implanted after dissection of the tunnel using Tunc''s specially designed dissector under suction. A complete ophthalmic examination was performed, including uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), spherical equivalent, keratometric (K) readings, inferosuperior asymmetry index (ISAI), and ultrasound pachymetry. All 3, 6, and 12-month follow-ups were completed, and statistical analysis was performed.

Results:

The mean preoperative UDVA for all eyes was 1.28 ± 0.59 logMAR. At 12 months, the mean UDVA was 0.36 ± 0.19 logarithm of the Minimum Angle of Resolution (logMAR) (P=0.002), and the mean preoperative CDVA was 0.58 ± 0.3 logMAR, which improved to 0.15 ± 0.12 (P=0.002) at 1 year. There was a significant reduction in cylindrical refractive and spherical equivalent refractive error from –5.29 ± 2.47 diopters (D) and –5.54 ± 5.04 D preoperatively to –1.47 ± 0.71 D and –0.74 ± 1.07 D (P=0.001, P=0.002), respectively, at 1 year. In the same period, the mean K- readings improved from 47.93 ± 4.84 D to 40.87 ± 2.36 D (P=0.002), and the mean ISAI improved from 5.34 ± 3.05 to 2.37 ± 1.68 (P=0.003). No significant changes in mean central corneal thickness were observed postoperatively. There were no major complications during or after surgery.

Conclusion:

ICRS implantation using a unique mechanical dissection technique is a safe and effective treatment for post-LASIK ectasia. All parameters showed improvement at 1-year follow-up.     

Which Keratometer is Most Reliable for Correcting Astigmatism with Toric Intraocular Lenses?

Purpose

To evaluate the accuracy of preoperative keratometers used in cataract surgery with toric intraocular lens (IOL).

Methods

Twenty-five eyes received an AcrySof toric IOL implantation. Four different keratometric methods, a manual keratometer, an IOL master, a Pentacam and an auto keratometer, were performed preoperatively in order to evaluate preexisting corneal astigmatism. Differences between the true residual astigmatism and the anticipated residual astigmatism (keratometric error) were compared at one and three months after surgery by using a separate vector analysis to identify the keratometric method that provided the highest accuracy for astigmatism control.

Results

The mean keratomeric error was 0.52 diopters (0.17-1.17) for the manual keratometer, 0.62 (0-1.31) for the IOL master, 0.69 (0.08-1.92) for the Pentacam, and 0.59 (0.08-0.94) for the auto keratometer. The manual keratometer was the most accurate, although there was no significant difference between the keratometers (p > 0.05). All of the keratometers achieved an average keratometric error of less than one diopter.

Conclusions

Manual keratometry was the most accurate of the four methods evaluated, although the other techniques were equally satisfactory in determining corneal astigmatism.