Calculation of tunnel incision parameters during phacoemulsification in patients with previous anterior radial keratotomy

Background. The purpose was the choice of the type of tunnel incision on the basis of mathematical calculations in cataract patients with a previous anterior radial keratotomy. Materials and methods. During the calculations, the formula for the chord length of a circle was used: L = 2R · sin(α/2), where R is the radius of the cornea, α is the angle (in degrees) between the two corneal incisions. The chord length was measured on the limbus (upper edge of the tunnel incision) and 2 mm from the limbus (lower edge of the tunnel incision). The chord 2 mm from the limbus is more important because the distance between kerato­tomy incisions at this site is smaller. From 0.4 to 1.0 mm must be added to the width of the knife blade, depending on the type of postoperative corneal healing, which will be the key to crossing the incisions. Results. The most common knives are those 2.2 mm long with a tunnel length of 2 mm. Therefore, we perform calculations based on this knife in patients with 8 and 12 keratotomy incisions and a corneal diameter of 12 mm vertically and 11 mm horizontally. In patients with 8 keratotomy incisions, a 2.2 mm knife can be used for a corneal tunnel incision, and in patients with 16 incisions, it is impossible to use a corneal tunnel. Conclusions. In cataract patients who have previously undergone anterior radial keratotomy, a special approach is needed to the choice of tunnel incision. The choice of access depends on the diameter of the cornea, the number of keratotomy incisions and the width of the knife and is calculated using the formula for the chord length of a circle.

Incisional correction of corneal astigmatism during ‎phacoemulsification – a randomized trial

Background: Phacoemulsification is regarded as a type of refractive surgery by which it is possible to ‎reduce pre-existing corneal stigmatism.‎ This study aimed to evaluate the efficacy and safety of on-axis corneal incision with or without opposite clear corneal incisions (OCCI) to correct preoperative corneal astigmatism during uncomplicated phacoemulsification ‎surgeries.‎ Methods: A randomized, prospective, parallel two-arm interventional study, which included a ‎total 40 eyes from 40 patients, was conducted.‎ Patients were divided into two groups: 20 patients as controls underwent phacoemulsification with on-axis incision (CCI group), and 20 patients underwent phacoemulsification with OCCI (OCCI group). Results: Mean astigmatic correction was significantly higher in the OCCI group (0.665 vs 0.265 diopters, p-value <0.001), compared to the CCI group. Most of the parameters (surgical induced astigmatism, magnitude of error, and correction index) were significantly higher in the OCCI group compared to the CCI group (p-value <0.01). There were no ‎incision-related complications. Conclusions: Both incisional methods are useful methods for correction of preoperative corneal ‎astigmatism but OCCIs correct a higher amount of astigmatism than the on-axis clear ‎corneal incision.‎ Registration: ClinicalTrials.gov NCT04418986 (05/06/2020).

Experimental Study on Delivery Performance of an Automated Preloaded Intraocular Lens Injector System for Corneal and Sclerocorneal Incisions

Purpose. To evaluate delivery performance of an automated preloaded intraocular lens (IOL) injector systems (AutonoMe) in the porcine eyes. Methods. In the freshly excised porcine eyes, lens removal and IOL implantation were performed. There were 4 groups (10 eyes per group) with different incision site and size: 2.2-mm and 2.4-mm corneal incisions and 2.2-mm and 2.4-mm sclerocorneal incisions. Delivery performance and wound enlargement of AutonoMe were analyzed and compared with those of iTec and iSert from a previous study. Results. There were a few minor troubles associated with AutonoMe, such as overriding plunger within cartridge and trapped trailing haptic during IOL insertion, but the incidence was low. Other interactions were not observed, such as IOL adherence to plunger, sudden ejection of IOL, intrawound lens manipulation, IOL behavior, and gross damage to IOL. AutonoMe caused significantly less wound enlargement for both corneal and sclerocorneal incisions than other injector devices. Wound enlargement by using AutonoMe was significantly smaller with 2.4-mm corneal incision than with 2.2-mm corneal incision, but the final incision size was still smaller with 2.2-mm corneal incision. For sclerocorneal incisions, the amount of wound stretch was not different between 2.2 and 2.4 mm incisions. Conclusion. The wound enlargement caused by the automated preloaded insertion system, AutonoMe, was smaller than that of other preloaded injectors for both corneal and sclerocorneal incisions. There were a few minor technical events during IOL insertion, but the overall incidence was low.

Burst Pressures in Eyes with Clear Corneal Incisions Treated with ReSure Glue

Purpose. This study aims to measure burst pressures in 3 mm clear corneal incisions sealed with ReSure, a biodegradable hydrogel sealant, and to compare it to traditional 10-0 nylon sutures and unsealed controls. Design. An ex vivo animal study. Methods. 3 mm clear corneal incisions were performed in rabbit eyes (ex vivo). The burst pressure was determined, and then, the incisions were sealed with either ReSure glue or a single 10-0 nylon suture. Burst pressure measurements were repeated. Results. Fourteen eyes were included. The median burst pressure in the suture-control group (7 eyes) prior to suture application was 7 mmHg (range: 0–45); the median burst pressure in the 7 glue-controls was 36 mmHg (range: 5–61, p = 0.08 for the comparison of the two control groups). The median burst pressure in the glue group was 93 mmHg (range: 39–129, p = 0.043 when compared to glue-control). The median burst pressure in the suture group was 158 mmHg (range: 70–180, p = 0.018 when compared to suture-control). There was no statistically significant difference in burst pressure values between the glue and suture groups ( p = 0.08). Conclusion. In this study, ReSure glue applied to 3 mm clear corneal incisions provided sufficient resistance to elevated intraocular pressure when compared to controls. The results of this study suggest that ReSure glue may be comparable to a single 10-0 nylon suture in resisting fluid egress during the early postoperative period.

A STUDY ON COMPARISON OF KERATOMETRIC CHANGES BETWEEN PREINCISION AND SINGLE-STEPPED CLEAR CORNEAL INCISION IN PHACOEMULSIFICATION SURGERY

Phacoemulsication surgery is the most widely used technique for cataract surgery nowadays. It can be done by either pre-incision or by clear corneal incisions. Clear corneal incisions are becoming more popular option for cataract surgery and IOL (intraocular lens) implantation. The availability of foldable IOL that can be inserted through small incisions has created a trend for clear corneal incisions. To compare post-operative kera to metric changes after phacoemulsication surgery between pre-incision or tunnel-based incision and single stepped clear corneal incisions. Fifty patients undergoing phacoemulsication surgery in the Dept. Of Ophthalmology, Nilratan Sircar Medical College & Hospital, Kolkata, West Bengal. Both pre-incision and clear-corneal incision in phacoemulsication surgery results in surgically induced astigmatism post-operatively, but there was no signicant difference in post-operative induced astigmatism in between both techniques.