Visualizing Cataract Surgery through Ophthalmic Surgical Microscope: Role of an External Co-axial Illumination

Dear Editor, Cataract surgery is an inseparable part of an ophthalmic surgeon’s life. With advancement in technology, patients’ expectation toward seamless vision at all distances has increased. Thus, a surgeon has to take utmost care when performing the cataract surgery in terms of minimizing the intraoperative complications. A better visibility through an operating microscope is essential in advance eye surgery. Operating microscope has the ability to form enlarged and erect images for an operating surgeon. Operating system consists of an observation, illumination, and mechanical system. An observation system consists of an eyepiece, inverted prisms, magnification changer, and objective lens. Illuminating system uses various light sources such as xenon light bulbs, halogen light bulbs, or light-emitting diode and comprises coaxial illuminating system which allows the light to follow the same path as image. This coaxial illumination is useful for visualization of posterior capsule and for vitreous surgery. When coaxial illumination is reflected from the patient retina to the observer, it results in red reflex. The intense of red reflex helps the surgeon to maintain the adequate visualization during surgery as well as identify corneal and anterior segment abnormalities.[1] However, limited or absence of red reflex can be seen in cataractous eye such as intumescent cataracts or cataracts with accompanying pathology such as vitreous hemorrhages.[2,3] Previous generation microscopes used output module interface (OPMI, Carl Zeiss) comprising single light beam which is offset by 2° to produce shadow and better depth. These microscopes also have multiple angles of illuminations for obtaining adequate red reflex during different steps of surgery, but require frequent repositioning or adjustment of the microscope and patients eye. Furthermore, sometimes, it may not provide adequate red reflex throughout pupil, thus degrading visualization and thereby can affect surgical outcomes. The ability of microscopes to produce red reflex and maintaining it throughout the procedure varies with different microscopes. Various modern operating microscopes provide stable red reflex and include Lumera (Carl Zeiss Meditec Inc.), LuxOR (Alcon Laboratories Inc.), and Proveo (Leica Microsystems).[4] Lumera has xenon source stereo coaxial illumination provided by 6° oblique field illumination and 2 separate coaxial light beams aligned with microscope eyepiece for enhancing retroillumination and red reflex. LuxOR consist of 2 overlapping nearly collimated light beam aligned with microscope eyepiece along with third oblique light beam which provide large diameter red reflex zone and maintain the same stability irrespective of eye movements and pupil size. Proveo 8 consists of light-emitting diode which provides better depth of field. Although these microscopes provide superior and wider field of view, better contrast, and stable red reflex, they are exorbitant. Previously, endoilluminators have been introduced in anterior chamber during cataract surgery to overcome the problem of visibility due to poor intensity of red reflex. However, it possesses the risk of damage to the ocular structures.[3] The Omniglo is an innovative small external coaxial illumination system designed by Dr. Jaideep Kakadia which can be attached to existing previous generation surgical microscopes to enhance the perception of red reflex during cataract surgery. Various factors affect the stability of red reflex such as pupil size, iris pigment, retinal pigment, vitreous and corneal clarity, centration of the eye, and eye movements and eye rotation.[1,5] However, attachments such as Omniglo can enhance the visibility of red reflex during surgery and thereby help reduce the surgery time and rate of capsulorhexis-related complications. It consists of halogen spectrum light-emitting diode. As per manufacturing guidelines, it has a life of 35,000 working hours and can last for more than 100,000 surgeries at a rate of 20 min per surgery. These attachments are microscope compatible, affordable, and easy to attach. Figure 1 illustrates red reflex captured on the same patient during cataract surgery without [Figure 1a] and with Omniglo [Figure 1b] attached to Zeiss Visu 150 microscope.Figure 1: Red reflex captured during cataract surgery without (a) and with Omniglo (b)Thus, to conclude, modern surgical microscopes are equipped with better features for visualization and resolution of ocular structures for better surgical experience; however, they are exorbitant to accommodate in small surgical practices. On the other hand, basic ophthalmic surgical microscopes which consist of coaxial illumination and which do not provide adequate visualization can be supplemented by an external attachment such as Omniglo which has the ability to rejuvenate basic microscope by improving its ability to provide stable red reflex and enhance the visibility during cataract surgery. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.