Mathew Kurian

Intacs in advanced keratoconus.

Purpose: To evaluate the surgical outcomes of microthin intracorneal ring segment (INTACS) implantation in advanced keratoconus. Methods: INTACS implantation was performed in eyes with advanced keratoconus. The main outcome measures were uncorrected visual acuity, best spectacle-corrected visual acuity, change in mean refractive spherical equivalent (MRSE), and keratometry. Results: Intacs were implanted in 14 eyes with advanced keratoconus. At 6 months, uncorrected visual acuity improved from 0.05 ± 0.08 to 0.16 ± 0.11 (P < 0.05), and best spectacle-corrected visual acuity improved from 0.50 ± 0.23 to 0.67 ± 0.00 (P = 0.01). The spherical refractive error improved from −6.68 D ± 6.44 to −3.11 D ± 3.08 (P = 0.03), whereas the cylindrical refractive error improved from −4.89 D ± 1.91 to −3.64 D ± 1.27 (P = 0.04). The MRSE reduced from −9.13 D ± 5.62 to −4.93 D ± 3.19 (P = 0.01), and the average keratometry decreased from 53.01 D ± 3.70 to 49.42 D ± 3.79 (P < 0.05). The results were stable from 6 months to 1 year. The procedure showed 100% safety, and more than 60% tolerated contact lenses. Younger age, male sex, and minimum central pachymetry of more than 400 μm seemed to be associated with better outcomes. Conclusions: In this series, Intacs provided good results with respect to visual acuity, corneal topography, and MRSE in eyes with advanced keratoconus without major complications or the need for segment explanation. INTACS is potentially a safe and efficacious treatment option in the management of advanced keratoconus.

The KIDROP model of combining strategies for providing retinopathy of prematurity screening in underserved areas in India using wide-field imaging, tele-medicine, non-physician graders and smart phone reporting

Aim: To report the Karnataka Internet Assisted Diagnosis of Retinopathy of Prematurity (KIDROP) program for retinopathy of prematurity (ROP) screening in underserved rural areas using an indigenously developed tele-ROP model. Materials and Methods: KIDROP currently provides ROP screening and treatment services in three zones and 81 neonatal units in Karnataka, India. Technicians were trained to use a portable Retcam Shuttle (Clarity, USA) and validated against ROP experts performing indirect ophthalmoscopy. An indigenously developed 20-point score (STAT score) graded their ability (Level I to III) to image and decide follow-up based on a three-way algorithm. Images were also uploaded on a secure tele-ROP platform and accessed and reported by remote experts on their smart phones (iPhone, Apple). Results: 6339 imaging sessions of 1601 infants were analyzed. A level III technician agreed with 94.3% of all expert decisions. The sensitivity, specificity, positive predictive value and negative predictive value for treatment grade disease were 95.7, 93.2, 81.5 and 98.6 respectively. The kappa for technicians to decide discharge of babies was 0.94 (P < 0.001). Only 0.4% of infants needing treatment were missed. The kappa agreement of experts reporting on the iPhone vs Retcam for treatment requiring and mild ROP were 0.96 and 0.94 (P < 0.001) respectively. Conclusions: This is the first and largest real-world program to employ accredited non-physicians to grade and report ROP. The KIDROP tele-ROP model demonstrates that ROP services can be delivered to the outreach despite lack of specialists and may be useful in other middle-income countries with similar demographics.

Air-puff associated quantification of non-linear biomechanical properties of the human cornea in vivo

With the advent of newer techniques to correct refraction such as flapless laser procedure and collagen crosslinking, in vivo estimation of corneal biomechanical properties has gained importance. In this study, a new 3-D patient specific inverse finite element method of estimating corneal biomechanical properties from air-puff applanation was developed. The highlight of the model was inclusion of patient-specific corneal tomography, fiber dependent hyperelastic model, cross links between collagen lamellae and epithelium layer. A lumped mass, spring and dashpot model was included to model the resistance to motion and deformation of the eye globe caused by air-puff applanation. 10 normal eyes of 10 human subjects were used for the study. 3-D finite element models were constructed and custom routines were scripted for performing the inverse calculations. The model for each eye was perturbed to estimate the effect of measured intraocular pressure on the estimated biomechanical variables. The study demonstrated that the inverse method was effective in quantification of material properties and was sensitive to intraocular pressure alterations. Specifically, in vivo fiber dependent hyperelastic biomechanical properties of human corneas were estimated for the first time.

Visual quality after posterior chamber phakic intraocular lens implantation in keratoconus.

PURPOSE: To quantify image‐quality characteristics after correction of refractive error with a posterior chamber phakic intraocular lens (PC pIOL) in eyes with stable or stabilized keratoconus. SETTING: Narayana Nethralaya Postgraduate Institute of Ophthalmology, Bangalore, India. DESIGN: Case series. METHODS: Eyes with stable or stabilized keratoconus that had V4 Visian PC pIOL implantation for correction of refractive error were evaluated postoperatively for visual‐quality metrics. RESULTS: Ten eyes of 7 patients had PC pIOL implantation. The preoperative mean refractive spherical equivalent of −7.21 diopters (D) ± 2.25 (SD) decreased to −0.55 ± 1.53 D at 6 weeks and −0.44 ± 1.21 D at 6 months. The efficacy index was 0.72 and the safety index, 1.13. The mean modulation transfer function (MTF) was 18.96 ± 14.16 (≥30 cycles per degree = good), the Strehl ratio was 0.11 ± 0.07 (1 = perfect), and the objective scatter index (OSI) was 4.45 ± 3.29 (≥1.5 = significant scatter). The MTF correlated inversely with secondary coma (P=.026), negative vertical coma (P=.014), and the root mean square (RMS) of total aberrations (P=.010) and higher‐order aberrations (HOAs) (P=.015). The OSI was directly correlated with secondary coma (P=.021), secondary trefoil (P=.016), the RMS of total aberrations (P=.032), and HOAs (P=.050). CONCLUSION: In keratoconus, the refractive error could be corrected with the PC pIOL; however, the associated aberrations had an adverse impact on the ultimate visual quality and have to be addressed. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

Biometry with a new swept-source optical coherence tomography biometer: Repeatability and agreement with an optical low-coherence reflectometry device

Purpose To assess the repeatability of a new swept‐source optical coherence tomography (SS‐OCT) biometer (IOLMaster 700) and evaluate the agreement with an optical low‐coherence reflectometry (OLCR) biometer (Lenstar 900) in cataractous eyes. Setting Tertiary eyecare facility. Design Prospective evaluation of a diagnostic test. Methods Eyes of patients had 3 consecutive scans acquired by the same operator. The repeatability of measurements was assessed using the within‐subject standard deviation and coefficient of variation (CoV). Agreement between the mean measurements of each machine was evaluated. Results The study comprised 100 eyes of 100 patients. The median lens thickness and axial length (AL) measurements were significantly greater (P < .001) with SS‐OCT (4.29 mm and 23.5 mm, respectively, versus 4.25 mm and 23.4 mm, respectively); anterior chamber depth (ACD) was greater with OLCR (2.72 mm versus 2.70 mm, respectively) (P < .001). The within‐subject standard deviation and CoV of the AL (0.01 and 0.05, respectively) and the ACD (0.04 and 1.22, respectively) measurements showed lower variability with SS‐OCT (0.05 and 0.21, respectively, for AL; 0.06 and 1.99, respectively, for ACD) than with OLCR. Good agreement was seen for anterior segment measurements between the 2 devices. The 95% limits of agreement of most parameters fell within the test–retest variability of the parameters. The SS‐OCT biometer also showed better penetration in dense posterior subcapsular cataracts, measuring AL successfully in 96% of cases. Conclusions The new SS‐OCT biometer showed good repeatability and agreement with the OLCR biometer. The SS‐OCT biometer measured the AL with fewer dropouts compared with the OLCR even in dense cataracts. Financial Disclosure None of the authors has a financial or proprietary interest in any material or method mentioned.

Mechanical eye (globe) injuries in children.

PURPOSE The epidemiology of mechanical eye injuries in children was studied to identify the agents of injury and their contribution to the severity of visual loss and to suggest preventive measures. METHODS The mode, type, and severity of injury were correlated with the visual acuity 6 months after the injury in all children with mechanical eye injuries between January 1994 to January 1999. RESULTS Of the 68 children with mechanical eye injuries, the mode of injury was host (child) related in 12 (17.65%) patients, agent related in 40 (58.82%) patients, and environment related in 16 (23.53%) patients. Mild injuries were seen in 22 (32.35%) patients, 31 (45.59%) patients had moderate injuries, and 15 (22.06%) patients had severe injuries. None of the patients with host-related injuries had a severe injury. Six (66.67%) patients with host-related injuries had a good visual outcome and none had a poor outcome. Among patients with agent-related injuries, 11 (25%) had a good outcome, 14 (40%) patients had a fair outcome, and 10 (22.5%) patients had a poor outcome. Of the patients with environment-related injuries 3 (33.33%) each had good, fair, and poor visual outcomes. CONCLUSIONS Agent and environment-related injuries had a far worse outcome than host-related injuries. This epidemiological classification directly suggests practical preventive measures that can be adopted at home or at school to reduce the incidence and severity of ocular injuries. The other predictors of the final visual outcome were the severity of the injury at presentation and the necessity for a secondary surgical procedure.

Decision making nomogram for intrastromal corneal ring segments in keratoconus

Purpose: To create a nomogram for the insertion of intrastromal corneal ring segments (ICRS) (Intacs® ) in eyes with keratoconus. Setting: Tertiary eye care center in South India. Materials and Methods: This prospective, non-randomized, interventional case series used a self-designed decision-making nomogram for the selection of ICRS in keratoconus patients based on the centration of the cone, mean refractive spherical equivalent (MRSE), and mean keratometry (Km) values. The 3, 6, and 12 months clinical outcomes were compared to historical controls. Primary endpoints were improvement in uncorrected and best-corrected vision and change in the keratometric values. Results: Group A comprised of 52 eyes of 50 patients that followed the nomogram, while Group B comprised of 25 eyes of 23 non-nomogram historical controls matched for baseline parameters. In Group A, the uncorrected distance visual acuity (UDVA) improved from 0.16 ± 0.15 to 0.25 ± 0.16 (P < 0.001), corrected distance visual acuity (CDVA) from 0.58 ± 0.2 to 0.69 ± 0.21 (P = 0.022), MRSE from -5.41 ± 4.94 to -1.71 ± 2.88 (P < 0.001), Km from 51.77 ± 5.45 to 48.63 ± 4.37 (P < 0.001), and astigmatism reduced from 5.86 ± 2.61 to 4.91 ± 2.72 diopters (P < 0.001).In Group B, improvement in the average MRSE was from -6.44 ± 5.32 to -3.26 ± 2.82 (P < 0.013) and in the average Km from 53.64 ± 5.32 to 50.31 ± 5.02 (P < 0.001). Other parameters did not improve significantly. A statistically significant difference was present in the percentage of patients achieving a good clinical outcome between the two groups (P < 0.001; Chi-square). Conclusion: The nomogram provides a means to choose the appropriate ICRS, hence improving the outcome in patients with keratoconus.

Intrastromal corneal ring segments for management of keratoconus

Keratoconus is a progressive corneal ectasia, which can be managed both by conservative measures like glasses or contact lenses in non-progressive cases or surgical procedures like collagen crosslinking (CXL) with or without adjuvant measures like intrastromal corneal rings segments (ICRS) or topography guided ablation. Various kinds of ICRS are available to the surgeon, but it is most essential to be able to plan the implantation of the ring to optimize outcomes. Aims: The aim of this study is to evaluate the visual outcome and progression in patients of keratoconus implanted with ICRS. Materials and Methods: Two different types of ICRS-Intacs (Addition Technology) and Kerarings (Mediphacos Inc.) were implanted in 2 different cohorts of patients and were followed-up to evaluate the outcome of the procedure. All patients underwent a complete ocular examination including best spectacle corrected visual acuity, slit lamp examination fundus examination, corneal topography and pachymetry. The ICRS implantation is done with CXL to stop the progression of the disease. Improvement in uncorrected visual acuity (UCVA), best spectacle corrected visual acuity and topographic changes were analyzed. Results: A significant improvement in keratometry and vision was seen in both groups. Conclusion: ICRS have been found to reduce corneal irregularity and flatten keratometry with improvement in UCVA and best corrected visual acuity.

Modified Technique for Epinucleus Removal in Posterior Polar Cataract

The authors describe a novel technique for the removal of the sub-incisional epinucleus in cases of posterior polar cataracts. After the removal of the nucleus, the epinucleus is removed from the quadrant opposite to the section by aspiration using the phaco probe. Then hydrodissection is performed to dislodge the sub-incisional epinucleus, which is aspirated out. The rate of posterior capsular rupture decreased considerably with this technique because it reduced the manipulations required.

Macular edema in Asian Indian premature infants with retinopathy of prematurity: Impact on visual acuity and refractive status after 1-year.

Purpose: To report the impact of transient, self-resolving, untreated “macular edema” detected on spectral domain optical coherence tomography in Asian Indian premature infants with retinopathy of prematurity (ROP) on visual acuity (VA) and refraction at 1-year of corrected age. Materials and Methods: Visual acuity and refraction of 11 infants with bilateral macular edema (Group A) was compared with gestational age-matched 16 infants with ROP without edema (Group B) and 17 preterms infants without ROP and without edema (Group C) at 3, 6, 9 and 12 months of corrected age using Teller Acuity Cards and cycloplegic retinoscopy. Sub-group analysis of the previously described pattern A and B macular edema was performed. Results: Visual acuity was lower in infants with macular edema compared with the other two control groups throughout the study period, but statistically significant only at 3 months. Visual improvement in these infants was highest between the 3rd and 6th month and plateaued by the end of the 1st year with acuity comparable to the other two groups. The edema cohort was more hyperopic compared to the other two groups between 3 and 12 months of age. Pattern A edema had worse VA compared to pattern B, although not statistically significant. Conclusion: Macular edema, although transient, caused reduced VA as early as 3 months of corrected age in Asian Indian premature infants weighing <2000 g at birth. The higher hyperopia in these infants is possibly due to visual disturbances caused at a critical time of fovealization. We hypothesize a recovery and feedback mechanism based on the principles of active emmetropization to explain our findings.