Severe Keratoconus Research Articles

Sociodemographic Predictors of Keratoconus (Severity, Treatment, and Progression) in a Tertiary Center in New York City.

To identify sociodemographic factors as predictors of keratoconus severity, progression, disease outcomes, and appropriate management in a tertiary care ophthalmology institute in the New York City metropolitan area. This is a retrospective chart review. Patients with keratoconus presenting at a tertiary eye institute in an urban setting seen between 2015 and 2022 were included. Sociodemographic data including age, sex, race, ethnicity, income derived from zip code, insurance coverage, and preferred language were recorded. These sociodemographic factors were analyzed as possible predictors of keratoconus severity at presentation (Amsler-Krumeich grades III and IV): patients presenting with acute hydrops, patients receiving corneal cross-linking or corneal transplant, patients showing 1 or more diopters of increase of Kmax during their follow-up, and patients having longer time between the provider's recommendation of corneal cross-linking and the time of the procedure. The retrospective review included 634 patients with a clinical diagnosis of keratoconus. Factors associated with severe keratoconus at presentation in the multivariate analysis were non-White (P < 0.001), lowest income (Q1) (P = 0.018), Q2 income (P = 0.012), and having Medicaid/Medicare coverage (P = 0.021). Medicaid/Medicare coverage was the only factor associated with acute hydrops (P < 0.001), and younger age was the only factor associated with disease progression (P < 0.001). Younger patients and patients with commercial insurance coverage were more likely to receive corneal collagen cross-linking (P < 0.001 and P < 0.001, respectively), whereas patients with Medicaid/Medicare coverage, lowest income, and non-White race were more likely to receive corneal transplantation (P = 0.012, P = 0.062, and P = 0.028, respectively). Medicaid/Medicare was the only factor associated with delay in receiving corneal collagen cross-linking (P = 0.013). Our study demonstrates that there are sociodemographic predictors of keratoconus disease severity, progression, and the type and the time of treatment the patients received. This confirms eye health disparities among patients with keratoconus.

Computer aided diagnoses for detecting the severity of Keratoconus

Abstract Problem Corneal topography instruments have limited parameter constraints for calculating precise defect ratios on the basis of the cone base area of the anterior axial curvature map for patients with Keratoconus (KC). Aim The aim of this study is to use thresholding-based segmentation and morphological techniques to calculate the pathological ratio of the keratoconic cornea through cone base area extraction for the detection of KC severity and tracking of disease development. Methods Data were collected from February 2022 to March 2023, comprising 97 cases from private clinics in southern Iraq. Disease severity was categorized into three stages, namely, mild, moderate, and severe, according to the topographic KC classification by a senior ophthalmologist. The Galilei system was used in obtaining the corneal topography images. The study proposed an image analysis method for corneal topography images using MATLAB R2020a. The method had four main steps: preprocessing, image segmentation, morphological processing, and pathological ratio calculation. Moreover, pathological ratio was compared with the KC severity through statistical analysis. A P-value less than 0.05 indicated statistically significant results. Results The majority of the cases in the mild category had a pathological ratio of ≤20%, and the moderate category had a higher prevalence ranging from 21 to 40%. The severe category had the highest distribution (&lt;40%). A P-value of &lt;0.001 indicated significant and clear link between KC stages and pathologic ratio. Conclusion The algorithm used for extracting the cone base area of the keratoconic cornea at different stages was validated by an ophthalmic specialist to ensure that the cone base area was appropriately extracted. The findings may help ophthalmologists to make informed decisions for patients with severe KC and assessments based on the percentage of corneal defects.

Longitudinal assessment of the progression of severe keratoconus based on corneal topography

We aimed to assess long-term disease progression in patients with severe keratoconus (KC). Clinical records of 125 patients (201 eyes) with severe KC followed-up for > 12 months were retrospectively analyzed. From these, 28 patients (31 eyes) were included. Corneal topography parameters evaluated included thinnest corneal thickness (TCT), maximum keratometry (Kmax), anterior and posterior mean corneal radii of 3 mm (aKM, pKM), steep keratometry, and KC screening indices. All patients wore rigid gas permeable contact lenses (RGPCLs) for an extended period. The median patient age and follow-up period were 20 (interquartile range [IQR] 17–22) years and 25 (15–38) months, respectively. Compared to baseline, the aKM, Kmax, and KC screening indices on the anterior corneal surface were reduced at the final follow-up (P < 0.05). No changes were observed in RGP-corrected visual acuity, TCT, pKM, or KC screening indices on the posterior corneal surface. The higher the baseline value, the greater the reduction in aKM and Kmax. Five patients (16%) experienced disease progression during follow-up. Patients with severe KC showed reduced anterior corneal surface curvature and no change in corneal thickness during an average follow-up period of 2–3 years while wearing RGPCLs.

Dynamics of Corneal Swelling With Hypoosmolar Riboflavin After Induction During Corneal Collagen Crosslinking in Patients With Progressive Keratoconus.

To evaluate the rate of corneal swelling induced by hypoosmolar riboflavin in patients with progressive keratoconus (KCN) with corneal thickness <400 µm after the induction phase using riboflavin with 20% dextran during epithelium-off corneal crosslinking (CXL). Prospective, nonrandomized, single-center consecutive case series. Preoperative assessments included tomography, specular microscopy, and hysteresis. After epithelial debridement, riboflavin with 20% dextran (Photrexa Viscous; Glaukos, Burlington, MA) was applied at 2-min intervals during a 30-min induction phase. Eyes that dehydrated to a minimum corneal thickness (MCT) of <400 µm after induction (postinduction pachymetry) were recruited. Hypoosmolar riboflavin 0.146% (Photrexa; Glaukos) was used every 10 s to induce stromal swelling, with pachymetry performed every 30 s until the MCT was ≥400 µm (postswelling pachymetry). Corneal swelling rate was compared with variables using regression analysis. In 31 eyes of 31 patients, mean postinduction pachymetry was 338.4 ± 28.7 μm. Hypoosmolar riboflavin induced a postswelling pachymetry of 413.4 ± 15.0 μm over a mean of 5.2 ± 3.2 min, and the average stromal swelling rate was 10.3 ± 8.7 μm/30 s. All eyes reached a postswelling pachymetry MCT ≥400 µm and no cases were aborted. Eyes with highly severe KCN (Kmax >70 and Belin/Ambrosio enhanced ectasia display final D score >17) experienced quicker swelling (14.4 ± 12.8 μm/30 s and 14.9 ± 12.4 μm/30 s, respectively; P < 0.05 for both). A thicker postinduction pachymetry was moderately associated with a faster rate of swelling (rs = 0.389; P = 0.030). Hypoosmolar riboflavin 0.146% can be safely employed in thinner corneas, allowing for swelling to ≥400 µm for epithelium-off CXL. Associations between swelling rate, KCN severity, and postinduction pachymetry were determined, allowing for a more accurate prediction of procedure time during CXL.

Scleral contact lens for severe keratoconus with corneal hydrops: A case report

We describe a case of fitting a scleral contact lens for keratoconus management. A 37-year-old female has came for the keratoconus management opinion. She was using glasses for the last 20 years. She was presented with bilateral severe keratoconus with corneal hydrops, and it show high myopic. A standardized eye examination was thoroughly done in the hospital visual acuity, corneal oculyzer and slit lamp examination with IOP measurement. . The best spectacle corrected visual acuity was Right eye 6/60 with pinhole no improvement with the correction of -13.75/-2.00 x 35 and Left eye having best spectacle corrected visual acuity of counting finger- finger counting with pinhole no improvement with the correction of -14.00 dsph. Optimal fitting characteristics were found in terms of vault, centration and landing and coverage the final parameter that we selected base curve, diameter, power and sag value RE 7.34, 16.40 mm, -15.25/-1.00 X 40, 5.41; LE 6.75, 16.40, -19.25/-1.50 X 110, 5.68 respectively. With over refraction of this power visual acuity was 6/6p and 6/9 in right eye and left eye respectively. In this case we were fit the patient with miniscleral lens which are more comfortable, and the visual acuity was also improved and in the follow up of 3 months no ocular adverse effects were seen. This case report shows that in this patient a Maxim Scleral Lens could be fitted successfully for keratoconus management, providing good visual quality.

Keratoconus presentation with respect to age, gender, and severity in Western India

Purpose: To study the demographic profile of keratoconus (KC) patients visiting a tertiary eye care hospital in Western India. Materials and Methods: This cross-sectional, observational study included newly diagnosed KC patients visiting our hospital between January 2018 and October 2022. Patient’s demographic details (self-reported age at first presentation, age at diagnosis, and sex) and mean maximum curvature (K Max) were collected. The patients were divided into age band of 5-year groups. A subanalysis of gender and severity was performed among groups. Spearman’s correlation coefficient was used to evaluate the relationship between KC severity and age. Results: A total of 536 patients with clinical KC were included. A self-reported age at first presentation was 19.4 ± 6.2 years. The mean age of diagnosis was 20.5 ± 6.0 years (range: 4–43 years). There were 61.6% (330) of males and 38.4% (206) of females (P &lt; 0.01). The mean K Max value was 59.2 ± 13.3 diopter (D). The mean K Max was not significantly different between the sexes, with the exception of the age range of 24–28 years, where females had more severe KC than males (P = 0.02). Among the included patients, 38.6% (207) of patients were pediatrics (≤18 years), while 61.4% (329) were adults (&gt;18 years). The mean K Max in pediatric KC (62.3 ± 15.1 D) was significantly higher than adult KC (57.3 ± 11.5), P &lt; 0.01. Severity of KC did not correlate with the age of the patients (r = −0.20, P = 0.04). Conclusion: KC presented at a younger age with moderate-to-severe stage of the disease, indicating the need for early KC detection in our population.

Inaptitude ophtalmologique dans les armées : étude épidémiologique multicentrique

This article aims to describe the causes of ophthalmological disqualification from the military services detected during specialist consultations conducted at Army Training Hospitals. This observational, cross-sectional, multicenter study retrospectively included individuals deemed as "unfit for military service" due to eye diseases identified during the specialist consultation conducted at 3 ATHs between January 2020 and December 2021. The data collected included age, medical and surgical history, reasons for ophthalmological disqualification, uncorrected distance visual acuity, best corrected distance visual acuity and cycloplegic refraction. Over this period, 133 subjects (98 men and 35 women) were included. Thirty-eight candidates (28.6%) were declared unfit due to a refractive error beyond the required limits, including 30 myopic subjects in excess of -10 diopters (D) and 8 hypermetropic subjects over +8 D. Twenty-five candidates (18.8%) were unfit under the age of 21 years due to corneal refractive surgery performed before the required age. Four subjects (3.0%) were unfit due to phakic intraocular lenses. Degenerative conditions were observed in 23 subjects (17.3%), including 21 patients with severe keratoconus. Other causes of incapacity were linked to oculo-orbital trauma in 11 subjects (8.3%), moderate or severe amblyopia in 7 patients (5.3%), congenital causes in 7 subjects (5.3%), inflammatory or infectious diseases in 7 candidates (5.3%), hereditary causes in 6 subjects (4.5%) and undetermined visual dysfunctions in 4 subjects (3.0%). The three main causes of ophthalmological disqualification were high ametropia, refractive surgery performed before the required age and keratoconus.

Repeatability of Epithelium Thickness Measured by an AS-OCT in Different Grades of Keratoconus and Compared to AS-OCT/Placido Topography

To compare agreement of corneal epithelium thickness (ET) between AS-OCT system (RTVue, Optovue) and AS-OCT/Placido topographer (MS-39, CSO) in eyes with different stages of keratoconus (KC), and to assess the repeatability of RTVue AS-OCT. Prospective reliability analysis. KC eyes were classified into forme fruste KC (FFKC), mild, moderate, and severe KC. Agreement was evaluated with Bland-Altman plots and 95% limits of agreement (LoA). The repeatability of RTVue was assessed via within-subject standard deviation (Sw), test-retest variability (TRT), coefficient of variation (CoV), and intraclass correlation coefficient (ICC). A total of 119 KC eyes were enrolled, with 21 being FFKC, 26 mild, 39 moderate, and 34 severe. The 95% LoA ranged between -5.9 and 4.8 µm for center epithelium thickness (CET), between -5.7 and 8.2 µm for thinnest epithelium thickness (TET). At 1-mm measuring points, the 95% LoA of superior, inferior, nasal, and temporal were -4.2 to 4.7 µm, -5.2 to 6.0 µm, -7.9 to 10.2 µm, and -11.2 to 6.0 µm. At 3-mm measuring points, the corresponding values were -2.8 to 9.3 µm, -2.0 to 13.0 µm, -4.6 to 9.6 µm, and -6.3 to 9.7 µm, indicating that the 2 instruments were not interchangeable without adjustment. Despite that the repeatability of RTVue measurements in KC patients were acceptable, repeatability decreased gradually with the peripheralization of the measurement points. The 2 OCT-based devices, RTVue and MS-39, do not provide interchangeable measurements of epithelium thickness in KC patients. Repeatability decreases in cases of more severe KC, emphasizing the importance of grading before clinical examination to avoid diagnostic errors.

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.&#x0D; 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.&#x0D; 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.&#x0D; 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.

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.

Accuracy of intraocular lens power formulas in eyes with keratoconus: Multi-center study in Japan.

To assess the accuracy of intraocular lens (IOL) power formulas, namely, SRK/T, Haigis, Barrett Universal II, Barrett True-K for keratoconus, Kane formula, and Kane formula for keratoconus, for cataract with keratoconus in Japanese eyes. Five surgical sites in Japan. A retrospective case series. Eyes with keratoconus undergoing cataract surgery were included. Postoperative refraction was compared with the prediction by the formulas. Visual acuity, manifest spherical equivalent, prediction error (PE), and mean absolute errors (MAEs) were determined 1month postoperatively. The PE within 0.50 diopter (D), 1.00 D, and 2.00 D were compared between IOL formulas. Subgroup analysis based on the steepest keratometry (stage 1, ≤ 48 D; stage 2, > 48 D and ≤ 53 D; and stage 3, > 53 D) was performed. The relationship between PE and preoperative biometric data were assessed. Fifty eyes were included. The MAE of the Barrett True-K for keratoconus, Kane keratoconus, and Kane formulas were significantly lower than that of Haigis. A statistically significant difference in the prediction accuracy within ± 0.50 D was found between Kane keratoconus and Haigis. The prediction accuracy of the Barrett True-K for keratoconus, SRK/T, and Kane within ± 1.00 D was statistically significant compared with that of Haigis. In stage 3, the Barrett True-K for keratoconus had a significantly lower MAE than SRK/T and Haigis. Keratoconus-specific formulas were more accurate than existing formulas in Japanese eyes. The Barrett True-K formula for keratoconus had higher prediction accuracy in severe keratoconus.

Assessing progression limits in different grades of keratoconus from a novel perspective: precision of measurements of the corneal epithelium

BackgroundTo assess repeatability and reproducibility of corneal epithelium thickness (ET) measured by a spectral-domain optical coherence tomographer (SD-OCT)/Placido topographer (MS-39, CSO, Florence, Italy) in keratoconus (KC) population at different stages, as well as to determine the progression limits for evaluating KC progression.MethodsA total of 149 eyes were enrolled in this study, with 29 eyes in the forme fruste keratoconus (FFKC) group, 34 eyes in the mild KC group, 40 eyes in the moderate KC group, and 46 eyes in the severe KC group. Employing the within-subject standard deviation (Sw), test-retest variability (TRT), coefficient of variation (CoV), and intraclass correlation coefficient (ICC) to evaluate intraoperator repeatability and interoperator reproducibility.ResultsThe repeatability and reproducibility of MS-39 in patients with KC were acceptable, according to ICC values ranging from 0.732 to 0.954. However, patients with more severe KC and progressive peripheralization of the measurement points had higher TRTs but a thinning trend. The current study tended to set the cut-off values of mild KC, moderate KC, and severe KC to 4.9 µm, 5.2 µm, and 7.4 µm for thinnest epithelium thickness (TET). When differences between follow-ups are higher than those values, progression of the disease is possible. As for center epithelium thickness (CET), cut-off values for mild KC, moderate KC, and severe KC should be 2.8 µm, 4.4 µm, and 5.3 µm. This might be useful in the follow-up and diagnosis of keratoconus.ConclusionsThis study demonstrated that the precision of MS-39 was reduced in measuring more severe KC patients and more peripheral corneal points. In determining disease progression, values should be differentiated between disease-related real changes and measurement inaccuracies. Due to the large difference in ET measured by MS-39 between various stages of disease progression, it is necessary to accurately grade KC patients to avoid errors in KC clinical decision-making.

Keratoconus Treatment Using Femtosecond Laser–Assisted Innovative Intracorneal Ring–Supported Graft Surgery: A Pilot Investigation

Purpose: To investigate clinical manifestations and response to a revision in the intrastromal corneal ring and implantation technique for the treatment of severe keratoconus at two private clinics in Iran. Methods: This prospective, non-comparative clinical study included 6 eyes from 6 patients treated with a new innovative sutureless ring-supported graft insertion technique. Refractive, topographic, corneal biomechanical, and anterior aberrometry outcomes were analyzed during the 6-month follow-up. Secondary variables included corneal stiffness and confocal microscopy. Results: No intraoperative and postoperative complications occurred. Six months after implantation of the RinGraft, the ring was centered at the pupil reflex, the eye was white and quiet, and the graft was clear. The mean topographic keratometry values decreased significantly postoperatively ( P = .025). Additionally, corneal stiffness increased significantly postoperatively ( P = .004). Anterior and posterior corneal aberrometry data collected over a 5-mm diameter revealed a significant decrease in higher order aberrations, spherical aberration, primary coma, and trefoil 6 months after surgery ( P = .019). Intraocular pressure changes were significantly greater than before surgery ( P = .006). Uncorrected distance visual acuity increased from 0.96 ± 0.52 logMAR preoperatively to 0.71 ± 0.22 logMAR postoperatively ( P = .078). No statistically significant change was found in corrected distance visual acuity ( P = .0221) Conclusions: Excellent structural support and stability of the cornea were observed immediately postoperatively and 6 months after RinGraft insertion. Considering the corneal instability and asymmetry, it appears to be a possible and safe therapy option for keratoconic eyes that can be performed easily. [ Journal of Refractive Surgery Case Reports. 2024;4(1):e1–e10.]

Performance of Corvis ST Parameters Including Updated Stress-Strain Index in Differentiating Between Normal, Forme-Fruste, Subclinical, and Clinical Keratoconic Eyes

PurposeThis study seeks to evaluate the ability of the updated stress strain index (SSIv2) and other Corvis ST biomechanical parameters in distinguishing between keratoconus with different disease stages, and normal eyes. DesignDiagnostic accuracy analysis to distinguish disease stages. Methods1084 eyes were included and divided into groups of normal (199 eyes), forme fruste keratoconus (FFKC, 194 eyes), subclinical keratoconus (SKC, 113 eyes), mild clinical keratoconus (CKC-I, 175 eyes), moderate clinical keratoconus (CKC-II, 204 eyes) and severe clinical keratoconus (CKC-III, 199 eyes). Each eye was subjected to a Corvis ST examination to determine the central corneal thickness (CCT), biomechanically corrected intraocular pressure (bIOP), SSIv2 and other eight Corvis parameters including the SSIv1, SP-A1, A1T, ARTh, IIR, DAM, DARatio2 and CBI. The sensitivity and specificity of these parameters in diagnosing keratoconus were analyzed through receiver operating characteristic curves. ResultsBefore and after correction for CCT and bIOP, SSIv2 and ARTh were significantly higher, and IIR and CBI were significantly lower in the normal group than in the FFKC group, SKC group and the 3 CKC groups (all P<0.05). There were also significant correlations between the values of SSIv2, ARTh, IIR, CBI and the CKC severity (all P<0.05). AUC of SSIv2 was significantly higher than all other Corvis parameters in distinguishing normal eyes from FFKC, followed by IIR, ARTh and CBI. ConclusionCorvis ST's updated SSI demonstrated superior performance in differentiating between normal and keratoconic corneas, and between corneas with different keratoconus stages. Similar, but less pronounced, performance was demonstrated by the IIR, ARTh and CBI.

Polymethylmethacrylate and Corneal Allogenic Intrastromal Ring Segments: Same Cornea, Different Optical Zones

Purpose: To present the first report of corneal allogenic intrastromal ring segment (CAIRS) insertion in a cornea with an existing polymethylmethacrylate (PMMA) segment each at a different optical zone. Methods: A 29-year-old man with severe keratoconus treated with PMMA ring segment implantation at a 7-mm optical zone and 375-µm depth presented with moderate improvement in visual acuity and topography. An allogenic segment was implanted at a depth of 260 µm and an optical zone of 5 mm without explantation of the existing segment. Results: There was additional topographic regularization and significant corneal flattening, with improvement in corrected distance visual acuity from 20/60 following PMMA insertion to 20/30 following CAIRS insertion. Corneal topography showed improvement in corneal regularity with centration of the cone on the corneal vertex and improvement in coma (from 1.69 diopters [D] @ 75° to 0.51 D @ 56° at 6-mm optical zone) and keratometric cylinder (from −6.47 D × 35° to −3.59 D × 18°). Conclusions: The implantation of CAIRS in an eye that has previously undergone synthetic segment implantation at a different optical zone was demonstrated to be a promising method for regularizing topography and improving vision in this case. [ Journal of Refractive Surgery Case Reports. 2023;3(3):e38–e41.]

Suprathreshold contrast perception of resolvable high spatial frequencies remain intact in keratoconus

Contrast detection thresholds are elevated with optical quality loss in keratoconus. This study hypothesized that suprathreshold contrast perception is also impaired in keratoconus, with the impairment being predictable from the pattern of loss in threshold-level performance. Contrast detection thresholds were determined across a range of spatial frequencies in 12 cases with mild to severe keratoconus and 12 age-similar controls. These values were used to predict the contrast needed to achieve perceptual matches between reference and test spatial frequency pairs (peak of CSF Vs. 0.3x, 0.5x, 2x or 3x spatial frequency from the peak) for stimuli at 10% and 50% suprathreshold contrast. Contrast thresholds predicted a 1.5 to 6.7-fold increase in the test pattern’s contrast to obtain a perceptual match with the reference pattern in keratoconus, relative to controls. Contrary to predictions, the empirical data of contrast matches between test and reference patterns were similar for higher than peak spatial frequencies at both contrast levels. However, as predicted, test patterns required higher contrast than the reference pattern for a perceptual match for lower than peak spatial frequencies. These results were similar to controls and invariant of disease severity, interocular asymmetry and short-term changes in optical quality. Unlike thresholds, suprathreshold contrast perception of resolvable high spatial frequencies appears immune to optical quality losses in keratoconus. These results are discussed in the context of the prevailing models of contrast constancy in healthy humans. Breakdown of contrast constancy at lower than peak spatial frequencies may reflect the properties of the testing paradigm employed here.

Keratoconic patient profile and management at public sector facilities in South Africa

Background: Keratoconus (KC) is a condition marked by thinning and protrusion of the cornea resulting in high myopia and irregular astigmatism. Knowledge of KC patients’ profiles and management approaches used can help to predict the needs of public hospitals to improve patient care.Aim: This study aimed to describe the profiles and management of KC patients.Setting: Capricorn district, Limpopo Province, South Africa.Methods: Medical records of 188 KC patients attending public hospitals of Capricorn District from January 2017 to December 2020 were reviewed. Data on patient profile and their management were collected and analysed.Results: The mean age of KC patients was 20.64 ± 6.82 years and the majority (56.9%) were males. Clinical findings were mean unaided visual acuity (UVA) of 0.19 ± 0.18, best corrected VA of 0.53 ± 0.24, spherical equivalence of -4.89 ± 9.17 dioptre (D), mean K of 57.37 ± 17 D and corneal astigmatism of -6.24 ± 4.27 D. A total of 54.5% of patients had severe KC. Bilateral KC was found in almost all patients (97.3%) and a mean K difference of 7.59 ± 6.08 D (p 0.001) between the better and the worse eye. The study found no significant difference in KC severity by age (p = 0.451) and gender (p = 0.819). Patients fitted with scleral lenses had the highest VA improvement of 0.44 ± 0.17.Conclusion: Most patients presented with bilateral and severe KC. Scleral lenses provided higher VA improvement than other methods.Contribution: The study aimed to present the clinical profile and management of keratoconic patients attending public sector facilities. Knowledge of the patterns of KC presentation may assist in the development of intervention strategies and guidelines for best practice in the management of KC, especially in public sector facilities.

Assessment of the effects of intrastromal injection of adipose-derived stem cells in keratoconus patients.

To evaluate the efficacy and safety of intrastromal transplantation of adipose-derived stem cells (ASCs) in keratoconus patients. This study was conducted on 8 eyes of 8 patients with moderate to severe keratoconus. In the patients, ophthalmic assessments including visual acuity, refraction, slit lamp examination, fundoscopy, corneal topography, and confocal microscopy were performed. Autologous stem cells were used. The isolated stem cells were injected into the corneal stroma by using femtosecond laser. Surgical procedure was similar to intracorneal ring implantation. All patients were re-assessed 1, 3, and 6mo after surgery. The baseline mean visual acuity was 0.48±0.18 and improved to 0.66±0.17 after surgery and final acuity increased by 1.85±0.80 lines (P=0.001). The mean spherical refraction of patients improved 0.34±0.35 D (P=0.039), and the mean cylindrical refraction of patients improved 0.84±0.23 D (P=0.016). The mean flat keratometry decreased 0.78±0.71 D (P=0.017), and the mean steep keratometry decreased 0.59±0.68 D (P=0.023). The mean central corneal thickness of patients improved of 6.29±4.47 µm (P=0.03). The mean keratocyte density at the anterior and middle stroma of cornea increased (P<0.05) but remained stable at the posterior stroma after 6mo. All patients had no complications and their corneas remained transparent. Intrastromal transplantation of ASCs has positive effects on vision and refractive parameters in most patients with keratoconus. After six months, visual acuity improved moderately, corneal parameters reduced slightly, and stromal keratocytes density increased. This modality is safe, and patients do not have any complications.

Visual Outcomes of Cataract Surgery in Patients With Keratoconus Using Toric and Non-toric Lenses

To compare the accuracy and outcomes of different intraocular lens (IOL) power calculation formulas in eyes with keratoconus undergoing cataract surgery with toric and non-toric IOLs. This was a consecutive retrospective case series study including patients from the Cornea Service at the Department of Ophthalmology and Visual Sciences at the University of British Columbia, Vancouver, Canada, from 2000 to 2020. Keratoconus was diagnosed based on corneal topography and clinician opinion. Patients who underwent topography-guided photorefractive keratectomy, intracorneal ring segments implantation, or corneal transplant were excluded. The manifest spherical equivalent, prediction errors, and median absolute errors were calculated. Descriptive statistics were expressed as mean ± standard deviation. There were 160 eyes from 101 patients; 136 eyes received non-toric lenses and 24 eyes received toric lenses. Most patients had mild disease (< 48.00 diopters [D]) when stratified by steep keratometry values. Patients with severe disease (> 53.00 D) were significantly more hyperopic following surgery (P < .05). The Barrett Universal II (0.26 D, inter-quartile range [IQR] = 0.4), Holladay 2 (0.31, IQR = 1.2), and SRK/T (0.42, IQR = 0.86) formulas had the lowest median absolute error. The postoperative prediction error following toric lens insertion was not significantly different than following non-toric lens insertion, and the mean absolute astigmatism was significantly reduced with toric lenses. The Barrett Universal II, Holladay 2, and SRK/T were the most accurate IOL power calculation formulas in patients with keratoconus undergoing cataract surgery. Hyperopic surprise was increased in severe keratoconus. Toric IOLs may be considered in patients with mild keratoconus. [J Refract Surg. 2023;39(5):319-325.].

Changes in corneal biomechanical parameters in keratoconus eyes with various severities after corneal cross-linking (CXL): A comparative study.

To compare changes in corneal biomechanical parameters one year after corneal cross-linking (CXL) in keratoconus (KCN) eyes of different severities. Seventy-five eyes with mild, moderate, and severe grades of KCN (n = 24, 31, and 20 eyes, respectively) that were treated with CXL, based upon the standard Dresden protocol, were included. The corneal biomechanical assessment was performed using Corvis ST and Ocular Response Analyzer (ORA). Changes in Corvis's dynamic corneal response (DCR) parameters and ORA's derived parameters (corneal hysteresis (CH), and corneal resistance factor (CRF)) were assessed whilst the corneal thickness and intraocular pressure were considered as covariates. There was no statistically significant difference in the corneal biomechanical parameters obtained using both devices after surgery separately in different KCN grades, except for the deformation amplitude (DA) in the severe KCN group (P = 0.017). Changes in the classic parameters of the highest concavity phase of Corvis ST (peak distance, radius, and DA) were more positive and in the newer parameters (integrated inverse radius (IIR), deformation amplitude ratio (DAR)) more negative in the severe group compared to the other groups. Also, the mean change in CH (P = 0.710), and CRF (P = 0.565), showed a negative shift in higher grades of KCN; however, there was no significant difference in the mean changes of all parameters between different groups. (P > 0.05). Similar changes in the Corvis ST and ORA parameters in mild, moderate, and severe KCN indicate biomechanical stability and the effective role of CXL in stopping the progressive nature of keratoconus in eyes of varying severities one year after CXL.