Corneal Topography Research Articles

New Generation of Small Incision Lenticule Extraction (SMILE) Procedure for Myopic Astigmatism with High Astigmatism Value : A Case Series

Introduction : Myopic astigmatism is a refractive disorder which could cause visual impairment especially with high astigmatism value. It affects patients’ productivity and quality of life. The management for myopic astigmatism is challenging because no consensus on the ideal method was reached.
 Case Illustration : Case 1: 19-year-old male with Uncorrected Visual Acuity (UCVA) 3/60 in the right eye with a manifest refraction of S-3.25 C-2.00 x 0 and 2/60 in the left eye with a manifest refraction S-5.50 C-0.50 x 0. Case 2: 18-year-old male with UCVA 3/60 in both eyes with a manifest refraction of S-3.00 C-2.25 x 5 and S-2.50 C-2.00 x 0. Case 3: 18-year-old male with UCVA 3/60 in both eyes witha manifest refraction of S-2.75 C-2.00 x 0 and S-2.50 C-2.25 x 180. Slit lamp, fundus examination, corneal topography, tomography, epithelial thickness profile, and aberrometry were within normal limits. The patients underwent SMILE using Visumax 800 Femtosecond laser with 3-4 mm incision at 120°, optical zone between 6-6.8 mm and cap thickness between 100-120 ?m.
 Discussion : In this case series, SMILE was chosen because studies described SMILE as an effective and safe refractive procedure compared to Femtosecond Laser-assisted in situ keratomileusis (FS-LASIK). Target refraction is emmetropia without cyclotorsion adjustment, it showed that post operative UCVA in all eyes were 6/6 using Snellen chart and none of the eyes loss the BCVA.
 Conclusion : New Generation of SMILE as management of myopic astigmatism with high astigmatism value shows good result improving visual outcomes.

CONSISTENCY OF TBUT VS NIBUT MEASUREMENT FOR ASSESSMENT OF DRY EYE DISEASE IN COMPUTER VISION SYNDROME

Abstract
 Introduction & Objectives : The coronavirus disease (COVID-19) pandemic requires medical faculty students to attend distance lectures using computers for long periods of time which directly has an impact of computer vision syndrome (CVS) which can progress to dry eye disease (DED). One of the tear film stability tests is the Tear Break Up Time, both with the invasive tear break up time (TBUT) technique and the non- invasive tear break up time (NIBUT) technique. This study aims to determine the consistency of tear film stability measurements using these two techniques in medical faculty students who suffer from CVS with and without DED.
 Methods : 62 medical students of Udayana University were enrolled in this study and devided into two groups namely CVS with DED symptoms and CVS without DED symptoms. Both groups were underwent TBUT examination using fluorescein strips and cobalt blue filter with slitlamp biomicroscopic and NIBUT examination with the tear film analysis software from Medmont E300 corneal topography.
 Results : There was no significant difference between TBUT and NIBUT measurements in the DED group (p=0.1985) and in the Non-DED group (p=0.9336). There was no difference in the consistency of TBUT and NIBUT in the two groups (p=0.4550).
 Conclusion : Both techniques provide consistent results in assessing DED. NIBUT technique is faster and more convenient for patients also can be an alternative for practitioners to diagnose DED if it is not possible to use TBUT due to allergies or the unavailability of fluorescein at the clinic.

CAN RIGID GAS PERMEABLE (RGP) CONTACT LENS BE THE BEST OPTION FOR A KERATOCONUS PATIENT?

Introduction : Keratoconus is a condition of cone-shaped cornea caused by stromal thinning. This disorder leads to visual disturbance due to irregular astigmatism, myopia, and corneal protrusion. A severe irregular astigmatism must be corrected by rigid gas permeable (RGP) contact lenses.
 Case Illustration : A 29 y.o female visited Ophthalmologist Clinic Subdivision of Refraction, Contact Lens, and Low Vision in RSKMM Provinsi Sumsel, complaining of discomfort while using her current glasses. Anamnesis, physical examination, and ophthalmologic examination were carried out. The patient then was maximally corrected of her refractive status, followed by contact lenses fitting and post- fitting evaluation.
 Discussion : Early ophthalmologic examination showed visual acuity of 6/60 ph 6/9 on both eyes. Corneal topography evaluation confirmed pattern of bilateral keratoconus, each 78% on right eye and 87% of left eye. Best-corrected visual acuity was 6/6 using S-3.50 C-7.00 180? (right eye) and S-4.00 C-6.00 170? (left eye). RGP fitting test was carried with trial lenses of S-4.00 D for both eyes with both base curve of 7.2 mm and diameter of 9.2 mm. Over-refraction showed result of S-3.50 D (right eye) and S-3.75 D (left eye) for both eyes to reach visual acuity of 6/6 and for patient to feel comfortable.
 Conclusion : While some period of adaptation was needed, severe keratoconus should be treated using RGP contact lenses to achieve a better prognosis. Accurate fitting test of RGP resulting in comfortable and satisfied outcome of patient.

The comparison of corneal densitometry in cases with glaucoma following childhood cataract surgery and juvenile glaucoma

PurposeTo compare the corneal densitometry (CD) in pediatric cases with glaucoma following childhood cataract surgery and juvenile open-angle glaucoma (JOAG).MethodsThis prospective comparative study involved 13 eyes with JOAG, 12 eyes with pseudophakic glaucoma, 13 eyes with aphakic glaucoma, and 15 control subjects. Pentacam HR Scheimpflug corneal topography was employed to evaluate corneal thickness (CCT) and CD values.ResultsThe mean intraocular pressure (IOP) and CCT were significantly higher in aphakic glaucoma cases than the other groups (p = 0.001). In aphakic eyes, the mean CD values were higher in most of the anterior, center, and posterior layers of 0–2 mm, 2–6 mm, 6–10 mm, and total zones (p < 0.001 for all). In pseudophakic eyes, the mean CD values were statistically similar with that of aphakic eyes and higher than that of JOAG and control eyes in all layers of 0–2 mm zone and in anterior layer of 10–12 mm and anterior and total layers of 2–6 mm zones (p < 0.05 for all). The CD values demonstrated significant correlations with CCT values in both aphakic and pseudophakic eyes. However, a significant correlation of CD values with IOP was only demonstrated in aphakic eyes (p = 0.01 for all).ConclusionThe probable effects of childhood cataract surgery especially aphakia might cause corneal backscatter of light and increased CD in all layers in all zones of the cornea. Increased CD values and its correlation with CCT and IOP in aphakic glaucoma eyes may be of importance in clinical management.

Rigid Gas Permeable (RGP) as Keratoconus Management After Corneal Collagen Cross-Linking (CXL) Procedure: a Case Report

Introduction : Rigid Gas Permeable (RGP) contact lenses are the mainstay for keratoconus patients and widely used. This case report presents RGP as a management for keratoconus after Corneal Collagen Cross- Linking (CXL) procedure.&#x0D; Case Illustration : A 22-year-old woman diagnosed with keratoconus since eight months ago, came for vision correction. She had CXL performed on both eyes. Ophthalmologic examination revealed uncorrected visual acuity of 0.63 in the right eye (RE) and 0.08 in the left eye (LE). Her best-corrected visual acuity (BCVA) was 1.0 in the RE with -0.75 D and 0.125 in the LE with -2.00 D. Anterior segment examination of the RE was unremarkable, but the LE has Vogt’s striae and Munson's sign (Figure 1). Corneal topography for the LE showed K1 64.7D/5.2 mm, K2 68.7D/4.9 mm, and Kmean 66.7D/5.1 mm. She was fitted with trial lens of BC 5.40 and the fit was loose. She then fitted with a BC of 5.50 mm showed a good fit result. RGP contact lenses were prescribed with S -8.50, BC 5.50, and 8.6 mm diameter for her LE and combined with spectacle for her RE. Her over-refraction BCVA of the LE was 0.9.&#x0D; Discussion : The management goals are to improve the patient’s visual acuity and to decrease the progression. The visual acuity of this patient improved after RGP fitting.&#x0D; Conclusion : The combination of CXL procedure and the use of RGP effective to increase visual acuity, regularity of corneal surface, and patient satisfaction. Keratoconus should be monitored regularly to avoid possible progressivity.

Impact of stimulant treatment on refractive errors and pupil diameter in attention deficit hyperactivity disorder.

The relationship between attention deficit hyperactivity disorder (ADHD) and visual impairment remains poorly understood, and the impact of visual impairment on the development of ADHD is uncertain. The aim of this study was to investigate the refractive profile and ocular biometric characteristics in patients diagnosed with ADHD and compare them with a control group. Additionally, we aimed to explore the potential influence of sex and medication intake. A cohort of 100 participants, including 50 individuals with ADHD and 50 age- and sex-matched control subjects, was included in this study. Ocular biometric parameters were measured, and refractive error was assessed using cycloplegic and non-cycloplegic autorefraction. Subgroup analyses were performed within the ADHD group based on sex, medication intake and age to investigate potential associations with the ocular findings. We observed no statistically significant differences in axial length, corneal topography parameters or anterior chamber characteristics between ADHD and control subjects. However, subgroup analysis within the ADHD group revealed that the prevalence of ametropia under cycloplegia was significantly higher in unmedicated (69.6%) compared to medicated (37.5%) (X2(2) = 7.320, p = 0.026) participants. Pupil diameter was significantly larger in medicated (3.91 mm) compared to unmedicated (3.58 mm; p = 0.017) individuals. Males had flatter (p = 0.004) and thicker (p = 0.008) corneas than females. Older ADHD participants had higher refractive error (p = 0.008 for non-cycloplegic and p = 0.0.003 for cycloplegic), axial length (p = 0.002) and corneal astigmatism (p = 0.049). Our study provides compelling evidence that individuals diagnosed with ADHD exhibit a similar incidence of refractive errors and ocular parameters compared to normal subjects. Nonetheless, the prevalence of refractive errors appears to be higher in unmedicated ADHD patients, suggesting the potential benefit of stimulant treatment. Additionally, stimulant use is associated with an increase in pupil diameter.

Evaluation of early period changes in intraocular pressure, ocular biometry and anterior segment after upper eyelid blepharoplasty.

To investigate the acute effects of upper eyelid blepharoplasty on intraocular pressure (IOP) and ocular biometric parameters. This prospective cross sectional study examined the eyes of 49 patients with dermatochalasis. Following a detailed ophthalmological examination, corneal topography was used to evaluate the eyes mesopic and photopic pupil diameter, anterior chamber depth, and corneal astigmatism on the day of surgery and on days first and seventh postoperatively. Ocular biometry was used to assess axial length and intraocular lens power. Goldmann applanation tonometry was used to measure intraocular pressure. Forty-nine eyes (26 males and 23 females) of 49 patients aged between 44 and 76years (mean 61 ± 7.9) were included in our study. The mean anterior chamber depth (ACD) was 2.90 ± 0.37mm preoperatively, 3.00 ± 0.29mm at postoperative day first, and 3.04 ± 0.29mm at postoperative day seventh, and the increase in anterior chamber depth was statistically significant (p < 0.001). The mean astigmatism values were measured as preoperative 0.73 ± 0.69 D, postoperative first day 0.93 ± 0.81 D, and postoperative seventh day 1.26 ± 0.90 D. The increase in astigmatism values was statistically significant (p < 0.001).The mean pupil diameter measurements in the mesopic environment were 4.20 ± 0.61mm preoperatively, 4.40 ± 0.59mm on the first postoperative day, and 4.39 ± 0.57mm on the seventh postoperative day, and there was a statistically significant difference between the three measurements (p = 0.03). The mean IOP measurements of the patients were 15.91 ± 3.51mmHg preoperatively, 16.81 ± 3.36mmHg on the first postoperative day, and 16.97 ± 3.13mmHg on the seventh postoperative day. The increase between these three measurements was statistically significant (p = 0.013). This study includes important insights into the potential acute phase impact of blepharoplasty surgery on ocular findings. Patients undergoing upper eyelid surgery should be informed about the possible change in ocular biometric parameters, intraocular pressure, and pupil diameter.

Barriers to the Diagnosis and Management of Keratoconus Among Optometrists in Kenya.

Early diagnosis and management of keratoconus (KC) are important for limiting visual complications of the disease. This study aimed to explore the perspectives of optometrists on the barriers to effective diagnosis and management of KC in Kenya. An online questionnaire was distributed to optometrists in Kenya to collect data on barriers to the diagnosis and management of KC. The majority (60.9%) of optometrists were confident in retinoscopy and subjective refraction. Fewer were confident in the use of keratometers (46.4%) and corneal topographers (24.9%) and in the fitting of rigid gas permeable (RGP) contact lenses (25.0%). The most commonly reported barriers to improving their knowledge and skills were, limited continuous professional development opportunities (87.4%), high costs of conferences (86.1%) and the lack of diagnostic tools (79.5%). Impediments cited to diagnosing and managing KC effectively were a lack of national guidelines (64.9%), patient education material (71.5%), equipment (58.9%) and RGP supply (68.2%) and cost (67.5%). Most commonly reported barriers related to patients were compliance (91.4%), affordability (90.7%), RGP discomfort (89.4%), willingness to pay (88.1%) and the lack of patient education about KC (87.4%). This study showed that the lack of national guidelines, essential equipment and adequate practitioner knowledge and skills were barriers to KC diagnosis and management. Regulation of optometric education and clinical practice, development of national guidelines for diagnosis and management of KC, up-skilling of practitioners and cost-effective solutions for equipment procurement and maintenance may improve both access to, and quality of, care to patients with KC.

Artificial Tear Instillation-Induced Changes in Corneal Topography.

This study aims to compare changes of corneal topography (Galilei G4) before and after the instillation of artificial tears in patients with dry eye disease (DED). Corneal topography was performed in patients 1 min before and after artificial tear instillation. Two types of artificial tears were used: 1% polysorbate 80 (PSB) and 0.5% carboxymethylcellulose (CMC). Of 135 patients, PSB and CMC were instilled in 101 and 34 eyes, respectively. The average value of Sim K increased significantly after instillation (44.07 ± 2.26 diopter (D)) compared to before (43.90 ± 2.02 D, p = 0.006) the instillation of artificial tears. Mean Sim K astigmatism was statistically increased after PSB instillation (1.48 ± 2.17 D) compared to before instillation (1.31 ± 2.10 D, p = 0.049). An axis change of astigmatism 10° or more after artificial tear instillation was found in 51.9% of patients, and 30° or more in 20.0% of patients. Increased Sim K value and significant changes in the astigmatic axis in the corneal topography were observed after instillation of artificial tears in DED patients. PSB instillation had a greater effect on corneal keratometry values than CMC instillation.

One-Year Results of a Phase I/II Randomized, Double-Masked, Placebo-Controlled Study of Processed Amniotic Fluid Drops After PRK.

The aim of this study was to evaluate the 1-year outcomes of using processed amniotic fluid (pAF) postoperatively after photorefractive keratectomy (PRK). Sixty-one participants were randomized to receive either placebo or pAF drops. The drops were instilled 4 times daily for 1 week after PRK along with routine postoperative medications. The primary outcome measures included uncorrected visual acuity, topographic corneal irregularity measurement, and surface staining over 1 year. A statistically significant difference in uncorrected distance visual acuity between the placebo and treatment groups was seen at 1 month post-PRK, with a visual advantage evident in the pAF group. A suggestive difference in corneal irregularity measurement was also seen between the placebo and treatment groups at 1 month postsurgery, with less irregularity noted in the pAF group. No differences in uncorrected distance visual acuity or corneal irregularity measurement were found at 3, 6, and 12 months. There was also no significant difference in corneal staining scores between the 2 groups at any of the measured time points. This 1-year study evaluating the safety and efficacy of pAF as an additional postoperative topical medication after PRK demonstrated that pAF offered a mild visual advantage at 1 month post-PRK. There were no late adverse events, and the intervention proved safe at 1 year.

Correction Method for Optical Scaling of Fundoscopy Images: Development, Validation, and First Implementation.

Although fundus photography is extensively used in ophthalmology, refraction prevents accurate distance measurement on fundus images, as the resulting scaling differs between subjects due to varying ocular anatomy. We propose a PARaxial Optical fundus Scaling (PAROS) method to correct for this variation using commonly available clinical data. The complete optics of the eye and fundus camera were modeled using ray transfer matrix formalism to obtain fundus image magnification. The subject's ocular geometry was personalized using biometry, spherical equivalent of refraction (RSE), keratometry, and/or corneal topography data. The PAROS method was validated using 41 different eye phantoms and subsequently evaluated in 44 healthy phakic subjects (of whom 11 had phakic intraocular lenses [pIOLs]), 29 pseudophakic subjects, and 21 patients with uveal melanoma. Validation of the PAROS method showed small differences between model and actual image magnification (maximum 3.3%). Relative to the average eye, large differences in fundus magnification were observed, ranging from 0.79 to 1.48. Magnification was strongly inversely related to RSE (R2=0.67). In phakic subjects, magnification was directly proportional to axial length (R2=0.34). The inverse relation was seen in pIOL (R2=0.79) and pseudophakic (R2=0.12) subjects. RSE was a strong contributor to magnification differences (1%-83%). As this effect is not considered in the commonly used Bennett-Littmann method, statistically significant differences up to 40% (mean absolute 9%) were observed compared to the PAROS method (P<0.001). The significant differences in fundus image scaling observed among subjects can be accurately accounted for with the PAROS method, enabling more accurate quantitative assessment of fundus photography.

Linear fitting of biconic surfaces for corneal modeling.

This paper presents a method for reconstructing the corneal surface. The proposed method was tested in 56 healthy and 15 post-orthokeratology corneas. The Medmont E300 Corneal Topographer was used to measure the anterior corneal elevation, and custom MATLAB scripts were employed for data analysis, fitting, and other computational processes. The results obtained were compared with the fitting to an ellipsoid and to a biconic, using an alternative method, showing similarities among the different approaches. Additionally, the advantages of this method and the biconic's generality over the ellipsoid were also demonstrated. In conclusion, the method proposed offers an approach with potential applications in the field of visual and ophthalmic optics related with modeling of the cornea and other optical surfaces.

Changes in Chord Mu (µ) Length Before and After Cataract Surgery

Aim: Comparison of chord  length, a potential marker that may gain importance especially in multifocal lens implantation, before and after phacoemulsification surgery and intraocular lens (IOL) implantation in patients with cataracts. Methods: This retrospective study included 33 eyes of 33 patients who underwent phacoemulsification surgery between December 2022 and February 2023. Corneal topography (Pentacam HR, Oculus, Wetzlar, optikgerate GmbH) was performed on each patient before and after surgery. The values obtained before and at least 3 months after surgery were compared using the Student-t test. Results: There were 18 (54.5%) males and 15 (45.5%) females among the 33 patients who participated in the study. The average age was 67.27 ± 10.93 years. The postoperative mean chord μ lenght was significantly lower than the preoperative mean chord μ lenght (p=0.002). Additionally, the mean postoperative pupil size was significantly lower than the mean preoperative pupil size (p=0.000). There is a weak positive relationship between the change in chord μ length and the change in pupil size, but this relationship is not statistically significant (p&gt;0.05). No statistically significant relationship was found between any of the other binary variables. Conclusion: Centralization is crucial in refractive surgery and multifocal IOL implantation to prevent high-order aberrations and photic phenomena. Therefore, it seems useful for surgeons to be familiar with chord μ measurements, especially regarding surgical preparation. It should be considered that changes in chord mu values may influence the development of photic phenomena. A decrease in chord mu after phacoemulsification may assist the surgeon in the preoperative decision-making process in patients at risk of photic phenomena or in patients with borderline values.

Analysis of Cytokine and Chemokine Level in Tear Film in Keratoconus Patients before and after Corneal Cross-Linking (CXL) Treatment.

Keratoconus (KC) is a degenerative corneal disorder whose aetiology remains unknown. The aim of our study was to analyse the expressions of cytokines and chemokines in KC patients before and after specified time intervals after corneal cross-linking (CXL) treatment to better understand the molecular mechanisms occurring before and after CXL in KC patients process of corneal regeneration.; Tear samples were gathered from 52 participants immediately after the CXL procedure and during the 12-month follow-up period. All patients underwent a detailed ophthalmological examination and tear samples were collected before and after CXL at regular intervals: 1 day before and after the surgery, at the day 7 visit, and at 1, 3, 6, 9, and 12 months after CXL. The control group consisted of 20 healthy people. 10 patients were women (50%) and 10 were men (50%). The mean age was 30 ± 3 years of age. Tear analysis was performed using the Bio-Plex 3D Suspension Array System. Corneal topography parameters measured by Scheimpflug Camera included: keratometry values (Ks, Kf), PI-Apex, PI-Thinnest, Cylinder.; All the 12 months post-op values of the KC patients' topographic measurements were significantly lower than the pre-op. As for the tear cytokine levels comparison between the patient and control groups, cytokine levels of TNF-α, IL-6, and CXCL-10, among others, were detected in lower amounts in the KC group. The pre-op level of IL-6 exhibited a significant increase the day after CXL, whereas comparing the day after the procedure to 12 months after CXL, this showed a significant decrease. Both TNF-α and IL-1 showed a significant decrease compared to the day before and after CXL. We observed significantly higher levels of IL-1β, IL-10, IFN-γ and TNF-α in moderate and severe keratoconus than in mild keratoconus (p < 0.05). We also demonstrated a statistically significant positive correlation between both pre-op and 12 months after CXL TNF-α, IFN-γ, IL-6 and Ks and Kf values (p < 0.05, r > 0); Alterations of inflammatory mediators in tear fluid after CXL link with topographic changes and may contribute to the development and progression of KC.

Outcome of combined cataract surgery and iris prosthesis implantation in iris melanoma patients previously treated with iridocyclectomy: A national retrospective non-comparative case series.

To examine complications, visual outcomes, photic patient-reported symptoms, corneal morphology, IOL tilt, and intraocular pressure after implantation of an intraocular lens (IOL) and iris prosthesis (IP) following iridocyclectomy. Patients with previous iridocyclectomy treated with an IOL and IP at the Copenhagen University Hospital Rigshospitalet between 2007 and 2018 were included in this national retrospective non-comparative case series. The assessment encompassed BCVA, PRO questionnaire, corneal topography, and anterior segment OCT. 45 patients were included. Eight of 45 patients were previously treated with ruthenium-106 brachytherapy in conjunction with iridocyclectomy. Six of 45 patients developed endothelial dysfunction four of whom had received ruthenium-106 brachytherapy. Five of 45 patients had subluxation of the IOL/IP complex due to incomplete zonula apparatus. BCVA improved for all patients after lens surgery. 26 patients participated in the invited follow-up examination. 19 of 26 (73%) reported none or mild photic symptoms after IP instalment. Five (19%) reported ongoing severe photic symptoms. The corneal astigmatism significantly increased after iridocyclectomy but did not change after lens surgery. Implantation of an IOL and IP is a safe procedure, alleviating photic symptoms in most patients. It comes with higher risk of complications due to a more demanding procedure and larger surgical traumas from previous treatments. Ruthenium-106 brachytherapy increases the complication risk. Corneal astigmatism is induced by iridocyclectomy but does not change after lens surgery.

Evaluation of the corneal topography based on deep learning.

The current study designed a unique type of corneal topography evaluation method based on deep learning and traditional image processing algorithms. The type of corneal topography of patients was evaluated through the segmentation of important medical zones and the calculation of relevant medical indicators of orthokeratology (OK) lenses. The clinical data of 1,302 myopic subjects was collected retrospectively. A series of neural network-based U-Net was used to segment the pupil and the treatment zone in the corneal topography, and the decentration, effective defocusing contact range, and other indicators were calculated according to the image processing algorithm. The type of corneal topography was evaluated according to the evaluation criteria given by the optometrist. Finally, the method described in this article was used to evaluate the type of corneal topography and compare it with the type classified by the optometrist. When the important medical zones in the corneal topography were segmented, the precision and recall of the treatment zone reached 0.9587 and 0.9459, respectively, and the precision and recall of the pupil reached 0.9771 and 0.9712. Finally, the method described in this article was used to evaluate the type of corneal topography. When the reviewed findings based on deep learning and image processing algorithms were compared to the type of corneal topography marked by the professional optometrist, they demonstrated high accuracy with more than 98%. The current study provided an effective and accurate deep learning algorithm to evaluate the type of corneal topography. The deep learning algorithm played an auxiliary role in the OK lens fitting, which could help optometrists select the parameters of OK lenses effectively.

The effect of pterygium on front and back corneal astigmatism and aberrations in natural-light and low-light conditions

BackgroundTo investigate the effect of different sizes of pterygium on the front and back corneal topography, refractive changes and aberrations in natural-light and low-light conditions.MethodsSixty subjects with unilateral primary nasal pterygium were enrolled in this study. All the patients’ uncorrected, best spectacle-corrected visual acuity, corneal topographic aberration data in 3 mm and 7 mm areas were collected. The pterygium size was evaluated by the slit-lamp photography and Sirius Scheimpflug Analyzer.ResultsThe front topographic astigmatism values, corneal total aberrations, and higher-order aberrations in 3 mm and 7 mm areas were higher in the pterygium group than those in the control group. The pterygium horizontal length and thickness were moderately to strongly correlated with astigmatism and RMS of aberrations, while pterygium vertical length showed no or just mild correlation with the corneal astigmatism and aberrations. Compared to the readings in 3 mm area, the front and back corneal astigmatism and aberrations were larger in 7 mm area.ConclusionsPterygium led to visual impairment by inducing astigmatism and aberrations. In low-light condition, the visual function worsened due to increased corneal astigmatism values and aberrations.

Keratoconus cone location influences ocular biomechanical parameters measured by the Ocular Response Analyzer.

Keratoconus is characterized by asymmetry in the biomechanical properties of the cornea, with focal weakness in the area of cone formation. We tested the hypothesis that centrally-measured biomechanical parameters differ between corneas with peripheral cones and corneas with central cones. Fifty participants with keratoconus were prospectively recruited. The mean ± standard deviation age was 38 ± 13 years. Axial and tangential corneal topography were analyzed in both eyes, if eligible. Cones in the central 3mm of the cornea were considered central, and cones outside the central 3mm were considered peripheral. Each eye was then measured with the Ocular Response Analyzer (ORA) tonometer. T-tests compared differences in ORA-generated waveform parameters between cohorts. Seventy-eight eyes were analyzed. According to the axial topography maps, 37 eyes had central cones and 41 eyes had peripheral cones. According to the tangential topography maps, 53 eyes had central cones, and 25 eyes had peripheral cones. For the axial-topography algorithm, wave score (WS) was significantly higher in peripheral cones than central cones (inter-cohort difference = 1.27 ± 1.87). Peripheral cones had a significantly higher area of first peak, p1area (1047 ± 1346), area of second peak, p2area (1130 ± 1478), height of first peak, h1 (102 ± 147), and height of second peak, h2 (102 ± 127), than central cones. Corneal hysteresis (CH), width of the first peak, w1, and width of the second peak, w2, did not significantly differ between cohorts. There were similar results for the tangential-topography algorithm, with a significant difference between the cohorts for p1area (855 ± 1389), p2area (860 ± 1531), h1 (81.7 ± 151), and h2 (92.1 ± 131). Cone location affects the biomechanical response parameters measured under central loading of the cornea. The ORA delivers its air puff to the central cornea, so the fact that h1 and h2 and that p1area and p2area were smaller in the central cone cohort than in the peripheral cone cohort suggests that corneas with central cones are softer or more compliantcentrally than corneas with peripheral cones, which is consistent with the location of the pathology. This result is evidence that corneal weakening in keratoconus is focal in nature and is consistent with localized disruption of lamellar orientation.

Effect of corneal diameter on preoperative screening results for corneal refractive surgery.

To investigate the impact of different corneal diameters on corneal morphology and biomechanical outcome during preoperative screening for corneal refractive surgery. A retrospective analysis was conducted on 300 patients who underwent corneal refractive surgery at Eye and ENT Hospital, Fudan University between October 2023 and December 2023. All patients had no history of keratoconus or previous corneal surgery. Patients were categorized into two groups based on corneal topography measurements: (1) normal corneal diameter group (n=159), those with corneal diameter ranging from 11.5 mm to 12.0 mm; (2) abnormal corneal diameter group (n=141), those with corneal diameter smaller than 10.0 mm or larger than 12.5 mm. Corneal thickness, morphologic data, and biomechanical data were measured using Pentacam corneal topography. Correlation analysis was conducted to explore the relationship between corneal diameter and various corneal topography and biomechanical data. Significant differences were observed in corneal topography data including BFSf (F=43.21), BFSb (F=30.24), Df (F=15.32), Dp (F=32.36), Da (F=9.66), D (F=58.36), PPIavg (F=32.64), and ARTmax (F=12.06) between the groups (P<0.05). Additionally, BFSf, BFSb, Db, Dp, D, and PPIavg exhibited statistically significant differences between any two groups (P<0.05). Significant differences were also found in Df, Da, and ARTmax between small and large corneas, as well as between normal-sized and large corneas (P<0.05). Correlation analysis indicated negative correlations between corneal diameter and A1V (r=-0.12), HCdArcLength (r=-0.17), CBI (r=-0.27), bIOP (r=-0.13), Df (r=-0.025), PPIavg (r=-0.028), and TBI (r=-0.27). Conversely, BFSf (r=0.009), BFSb (r=0.001), PD (r=0.15), and ARTH (r=0.37) displayed positive correlations with corneal diameter. Corneal diameter significantly affects preoperative screening for corneal refractive surgery. Smaller corneal diameters exhibit a greater influence on the corneal topography BAD analysis system.

Effect of Corneal Collagen Crosslinking with Riboflavin in Patients of Progressive Keratoconus: A Prospective Cohort Study

Introduction: Keratoconus is a non inflammatory disease characterised by progressive corneal thinning that results in a cone-like ectasia, irregular astigmatism, and decreased vision. Advanced disease can result in corneal scarring and blindness, necessitating penetrating keratoplasty. The only treatment believed to have the ability to stop or decrease the progression of keratoconus is Collagen Cross-Linking (CXL). Aim: To evaluate the efficacy of corneal collagen cross-linking with riboflavin (C3R) in patients with keratoconus by studying the outcomes in terms of Uncorrected Visual Acuity (UCVA), Best Corrected Visual Acuity (BCVA), manifest refraction, and corneal topography. Materials and Methods: A hospital-based prospective cohort study was conducted at the Regional Institute of Ophthalmology, Government Medical College, Thiruvananthapuram, Kerala, India from June 2017 to June 2018. Fifteen eyes of 12 patients who underwent corneal collagen cross-linking for progressive keratoconus were included. Routine ophthalmological examinations was done for all patients. Patients under the age of 35 years with progressive keratoconus, an average K value not exceeding 60 D, and who had not undergone any other surgical modalities of treatment were included in the study. Patients with scarred cornea or hydrops, active ocular infection, or pachymetry &lt;400 µm were excluded. Detailed informed consent was obtained from all patients before surgery. Preoperative UCVA, BCVA cylinder, Spherical Equivalent (SE), and topography values were obtained. All patients were followed-up at three and six months postoperative period to look for changes in UCVA, BCVA, manifest refraction, and corneal topography. Data were expressed as the mean±Standard Deviation (SD) pre- and postoperatively and analysed statistically using the paired t-test, with p&lt;0.05 considered statistically significant. Analysis was conducted using Statistical Package for Social Sciences (SPSS) version 16.0. Results: On follow-up at six months post-treatment, UCVA (log MAR) improved from 0.87±0.40 to 0.65±0.35 (p-value=0.001), and BCVA (log MAR) changed from 0.37±0.21 to 0.17±0.22 (p-value=0.001). K max decreased from 54.90±6.05 to 52.67±5.02 (p-value=0.001), and K min decreased from 48.14±4.24 to 45.93±4.07 (p-value=0.001). Astigmatism and SE also showed statistically significant improvement post-procedure (p-value 0.001 and 0.002, respectively). Astigmatism reduced from -3.50±1.58 to -2.90±1.37. SE reduced from -4.93±3.92 to -4.28±3.48. No significant complications were noted in any of the patients. Conclusion: The CXL is an effective procedure for stabilising the progression of keratoconus, thus reducing the burden of preventable blindness and the need for keratoplasty.