Early Changes of Ocular Biological Parameters in Rhesus Monkeys After Scleral Cross-linking With Riboflavin/Ultraviolet-A.

PURPOSE: To evaluate the ocular biological parameter difference between scleral corneal cross-linking (CXL) and control eyes in rhesus monkeys by using a rebound tonometer, A-scan ultrasonography, retinoscopy, optical coherence tomography, and electroretinography (ERG). METHODS: Six rhesus monkeys were used in this study, with ages ranging from 3 to 3.5 years. One eye of each rhesus monkey was randomly selected to receive riboflavin/ultraviolet-A CXL in the temporal quadrant of the equatorial sclera and the contralateral eye served as an intra-individual control. The ocular biological parameters were repeatedly measured in both eyes of the monkeys before scleral CXL and 1 week, 1 month, and 3 months postoperatively. RESULTS: The intraocular pressure, refractive state, total axial length, and axial dimensions of the anterior chamber, crystalline lens, vitreous chamber, and central corneal thickness were not statistically significantly different between the control and cross-linked specimens at the different time periods (each P > .05). No obvious changes in the waveform of the standard full-field ERGs were observed in the control and cross-linked specimens. There were no statistically significant differences between the control and cross-linked specimens in the dark-adapted 0.01 ERG, the dark-adapted 3.0 ERG, the light-adapted 3.0 ERG, and the amplitudes of the a-wave and b-wave for the different time periods (each P >.05). CONCLUSIONS: The scleral CXL laboratory technique might not significantly affect the ocular biological parameters of the rhesus monkey in the early postoperative period, but long-term effects and histological changes still need to be investigated further. [J Refract Surg. 2019;35(5):333-339.].

Consistent comparison of angle Kappa adjustment between Oculyzer and Topolyzer Vario topography guided LASIK for myopia by EX500 excimer laser.

AIM: To evaluate and compare the uniformity of angle Kappa adjustment between Oculyzer and Topolyzer Vario topography guided ablation of laser in situ keratomileusis (LASIK) by EX500 excimer laser for myopia. METHODS: Totally 145 cases (290 consecutive eyes )with myopia received LASIK with a target of emmetropia. The ablation for 86 cases (172 eyes) was guided manually based on Oculyzer topography (study group), while the ablation for 59 cases (118 eyes) was guided automatically by Topolyzer Vario topography (control group). Measurement of adjustment values included data respectively in horizontal and vertical direction of cornea. RESULTS: Horizontally, synclastic adjustment between manually actual values (dxmanu) and Oculyzer topography guided data (dxocu) accounts 35.5% in study group, with mean dxmanu/dxocu of 0.78±0.48; while in control group, synclastic adjustment between automatically actual values (dxauto) and Oculyzer topography data (dxocu) accounts 54.2%, with mean dxauto/dxocu of 0.79±0.66. Vertically, synclastic adjustment between dymanu and dyocu accounts 55.2% in study group, with mean dymanu/dyocu of 0.61±0.42; while in control group, synclastic adjustment between dyauto and dyocu accounts 66.1%, with mean dyauto/dyocu of 0.66±0.65. There was no statistically significant difference in ratio of actual values/Oculyzer topography guided data in horizontal and vertical direction between two groups (P=0.951, 0.621). CONCLUSION: There is high consistency in angle Kappa adjustment guided manually by Oculyzer and guided automatically by Topolyzer Vario topography during corneal refractive surgery by WaveLight EX500 excimer laser.

[Advanced research in the safety of UVA-riboflavin cross-linking for strengthening corneal and scleral tissue].

UVA-riboflavin cross-linking is an effective approach to increase the mechanical and biochemical rigidity of the collagen fiber, which has been used in treating some corneal diseases such as keratoconus, and might become a new treatment modality for strengthening scleral tissue to prevent progressive myopia, so the safety of the new therapy has be paid attention widely. This article focus on the diffusion process and saturation judgment of riboflavin and describes the effect of riboflavin, direct UV damage, photochemical damage and the prevention of side effects in cross-linking therapy.

[Caution to perform excimer laser corneal ablation on the ametropia with corneal guttata].

It is very important to avoid inadequate patients to perform excimer laser keratectomy in order to prevent from surgical complications. The ametropic eyes with corneal guttata is considered very carefully whether to perform excimer laser corneal ablation or not, especially for the patient with corneal guttata companied by Fuchs endothelial dystrophy family history is contraindicated to perform laser corneal refractive surgery.

Rigid iris-fixated phakic lens implantation for high myopia: novel trapezoidal corneal versus scleral incisions.

PURPOSE: To compare refractive performance of implantation of an iris-fixated phakic intraocular lens (PIOL) through a novel trapezoidal corneal and a scleral tunnel incision. METHODS: Sixty-nine eyes selected to undergo PIOL implantation were randomly assigned to 1 of 2 groups: 5.2-mm trapezoidal corneal incision (TCI), 34 eyes; 5.2-mm scleral tunnel incision (STI), 35 eyes. Visual acuity, refraction, corneal astigmatism, tonometry, and endothelial cell density were recorded preoperatively and postoperatively. Surgically induced astigmatism (SIA) was calculated using vector analysis. RESULTS: No intraoperative complications were noted. One day after surgery, the quantity of cells in the anterior chamber was significantly lower in TCI group than in STI group (p=0.019). The percentage of eyes with uncorrected visual acuity (UCVA) of ≥20/25 was 41.2% for TCI and 17.1% for STI; the difference was statistically significant (p=0.03), but not thereafter. The mean corneal astigmatism was significantly lower in the TCI group than in the STI group (p=0.01) 3 months postoperatively and subsequently. No significant between-group difference in SIA was found during the follow-up. There was no significant difference in best-corrected visual acuity and endothelial cell loss between groups, postoperatively. CONCLUSIONS: The TCI and STI techniques are comparable in terms of safety and induction of astigmatism for the rigid iris-fixated PIOL implantation. However, the TCI is easy to perform and provides a faster visual recovery and lower postoperative corneal astigmatism compared with the STI.

[Whether does the granular corneal dystrophy indicate for the excimer laser ablation surgery or not].

With the development of excimer laser technologies, the corneal refractive surgical procedures are improved constantly and the indication of excimer laser keratectomy is expanded. In clinic, PRK or LASEK or PTK or LASIK were performed on the eyes of granular corneal dystrophy with refractive error and the early results were satisfied, but the reoccurrence and server opacity of cornea are worried. Is this corneal disease the indication of excimer laser keratectomy? Nowadays, the exact indication for the disease should be declared in clinic. In this article, the customized treatment nomogram for three types of granular corneal dystrophy is explicated according to the clear classification and exact diagnosis on this disease, in order to apply the excimer laser keratectomy reasonably and correctly for the patient approaching the safe, effective and long term satisfactory result.

Comparison of age-related changes between corneal and ocular aberration in young and mid-age myopic patients.

AIM: To study the dynamic character of aberration between the cornea and the ocular with aging, and to evaluate the symmetry of the aberrations between right and left eye in order to supply the data for clinic to do the refractive surgery reasonably. METHODS: This is a comparative case series study. 82 normal cases (164 eyes) including 37 females (74 eyes) and 45 males (90 eyes) were recruited through the routine examinations, Topolyzer and wavefront analysis. The average age was 25.9±5.0 years old (range 18 to 49 years old), and the mean spherical equivalent (SE) is -3.82±2.21D (range -1.00 to -6.00D). The changes of aberrations regarding age, the relationship between anterior corneal and total aberrations were analyzed, as well as the symmetry between right and left eyes by using Zernike terms. RESULTS: The Z(3) (1), RMS3 of corneal aberrations, Z(3) (1), Z(4) (0) , RMS3 and RMS4 of ocular aberrations had a positive correlation with age. The zernike terms both in corneal and whole eye were significantly correlated between right and left eyes. CONCLUSION: The corneal horizontal coma, ocular horizontal coma and ocular spherical aberrations become to increase at the age of more than 40 years old. The dynamic change of aberration with aging, balance between corneal and ocular, and the symmetric character between left eye and right eye should be designed carefully in the treatment nomogram before the refractive surgery.

[Evaluation of intraocular lens power after keratorefractive surgery by IOLMaster].

OBJECTIVE: To study the accuracy of different formulas predicting intraocular lens (IOL) power after excimer laser keratorefractive surgery in order to calculate the diopter of IOL accurately in the clinical practice. METHODS: One hundred and eleven cases (222 eyes) were collected in this study and were divided into two groups (A and B) according to their axial length. Fifty-nine cases (118 eyes) with axial lengths of 24-26 mm were taken as group A, and 52 cases (104 eyes) with axial length of more than 26 mm were taken as group B. All of the subjects enrolled in this study were examined by the IOL-Master before and after LASIK, including the axial length, corneal curvature, anterior chamber depth (ACD), and the IOL power which was predicted by the SRK-II, SRK/T, Hoffer Q, Holladay, Haigis-L formulas and the Clinical History method offered by IOL-Master. The significance of the differences was analysed by using student's t-test. RESULTS: The corneal curvature after LASIK decreased significantly (t = 12.10, P < 0.01); the length of axis and ACD also decreased but had no significant differences as compared with pre-operation. The IOL powers of the two groups offered by the Haigis-L formula were significantly more than that offered by other formulas (t = 0.54, 1.21, P < 0.01). The difference between the Haigis and Haigis-L formulas was the smallest, and the difference between the SRK-II and Haigis-L formula was the greatest. The IOL powers offered by the clinical history method were higher than that offered by these formulas; the differences were significant in both group A and group B, except the group A in SRK-II (t = 0.00, -1.73, 0.00, P < 0.01). The IOL powers offered by Haigis-L were greater than that from the clinical history method or other formulas and showed significant differences except that between Haigis-L and CH-Haigis or CH-Haigis-L formula (P < 0.01). CONCLUSIONS: Taking into consideration the difference of IOL power offered by Haigis-L formula as compared with other current formulas, evaluation by IOL-Master will be helpful for improving the accuracy of IOL power prediction for the cataract eyes receiving corneal refractive surgery. However, the accuracy of the Haigis-L formula for eyes after corneal refractive surgery still requires to be confirmed by a further series of clinic data.

[Comparison of retaining or removing negative vertical coma in wavefront guided LASIK for myopia and astigmatism].

OBJECTIVE: To investigate the efficacy and safety of wavefront guided (WG) LASIK for the myopia and astigmatism. METHODS: This study is a randomized control trial. 42 cases (78 eyes) were collected in the study through the routine examinations and wavefront analysis, which were divided into two groups (A and B). The value of Z (3, -1) being less than -0.15 microm was evaluated as Group A (24 cases, 45 eyes); The value of Z (3, -1) being more than +0.15 microm was as Group B (18 cases, 33 eyes). Both A and B were also divided into two subgroups (test and control). WG-LASIK was performed in tested groups, and classic LASIK was performed in control group. Visual quality, wavefront examination, and CSF were analyzed after surgery 3-6 months compared with that of preoperation. RESULTS: In the earlier period of post-operation time, diopters of the two groups were both slightly overcorrected, and then began to decrease slightly later and the diopters of both tested and control groups were corrected perfectly. RMSh of tested group increased higher than that of control group when Z (3, -1) was negative and the CSF in control group was better than that in test group after WG-LASIK in Group A. RMSh of tested group increased lower than that of control group when Z (3, -1) was positive and the CSF in tested group was better than that in control group after WG-LASIK in Group B. CONCLUSIONS: These results suggest that retaining negative vertical coma and removing positive vertical coma were beneficial to the visual function after the WG-LASIK, which could save the corneal tissue reasonably in order to improve visual quality effectively.