Medical hypothesis, discovery & innovation in optometry

Background: Ascorbic acid has been suggested to be effective against chemical burns. It was first tested in rabbits before being implemented in human subjects. It was proven to be useful in treatments for different conditions, such as corneal chemical and thermal burns. Herein, we aimed to review the effects of ascorbic acid in the healing of chemical and thermal corneal burns.
Methods: We performed an electronic search of English literature in MEDLINE, clinicaltrials.gov, and Google Scholar, without time constraints. Articles were selected based on inclusion and exclusion criteria, using they keywords: Corneal Burn, AND Corneal Ulcer, AND Vitamin C. This yielded 17 English language articles focused on the effect of vitamin C on chemical or thermal corneal burn-induced ulcers.
Results: The 17 eligible studies that fulfilled the inclusion criteria included three retrospective, nonrandomized, comparative studies on human subjects and 14 in vivo, laboratory-based studies on rabbits (12 studies), rats (one study), as well as guinea-pigs (one study). Most studies showed benefits in using vitamin C as a prophylactic treatment to delay or stop corneal ulcer formation after chemical or thermal corneal burn.
Conclusions: Vitamin C is a very basic, inexpensive prescription and can be used to treat corneal ulcers following a variety of corneal burns. This review highlights the necessity for conducting randomized controlled trials to investigate the prophylactic role of vitamin C and to determine its minimum required dose for the management of corneal ulcers after different types of corneal burns.

Background: The purpose of this study was to evaluate the long-term outcomes of sutureless scleral-fixated intraocular lens (SFIOL) implantation at a tertiary referral center.
Methods: This retrospective observational study included 50 eyes of 43 consecutive patients who underwent sutureless SFIOL implantation by a single surgeon from January 2009 to December 2015. Indications for surgery were aphakia, dislocated intraocular lens (IOL), complicated cataract surgery (posterior capsule rupture, zonular dialysis, dropped nucleus), iris-clipped IOL with corneal decompensation, and lens with poor capsular support. Indication for surgery, visual acuity, ocular history, ocular comorbidities, intraoperative and postoperative complications, and the need for further surgery were analyzed.
Results: The analysis conducted on 50 eyes from 43 patients with a mean ± standard deviation (SD) follow-up of 16.64 ± 9.34 months. Patients were 27 (63%) men and 16 (37%) women with a mean ± standard deviation (SD) age of 53.36 ± 22.45 years (range 8-90 years). Final visual acuity was 6/18 or better in 39 eyes. SFIOL was stable and well centered in 48 eyes. SFIOL dislocation was noted in 2 eyes, retinal detachment in 1 eye, and worsening of diabetic cystoid macular edema in 1 eye. Two patients with pre-existing corneal decompensation from complicated cataract surgery had worsening of their condition
Conclusions: Sutureless SFIOL could be considered as a long-term option for the management of aphakia, dislocated IOL, and lens with poor capsular support. However, future studies with more subjects, longer follow-ups, and robust study design are needed to confirm the results of the present study.

Background: We evaluated and compared outcomes of laser-assisted in situ keratomileusis (LASIK) versus optical spectacle correction for the treatment of anisometropia in adult patients.
Methods: This prospective, randomized controlled clinical trial included 50 eyes of 50 patients. We randomly allocated participants to Group A (25 eyes with anisometropia assigned to LASIK treatment) and Group B (25 eyes with anisometropia assigned to optical spectacle correction). All patients underwent preoperative and postoperative visual acuity, subjective and cycloplegic refraction, fundus, slit-lamp, and corneal topography examinations.
Results: In Group A, at 1-month postoperatively, there were statistically significant differences in uncorrected distance visual acuity, corrected distance visual acuity, refractive sphere, cylinder, and spherical equivalent (SE) as compared to baseline. At 3-months postoperatively in Group A, SE showed good stability within ± 0.50 diopter (D) in 22 eyes (88%) and within ± 0.75 D in 23 eyes (92%), while two eyes had an SE beyond 1.00 D emmetropia. Five eyes had amblyopia with minimal improvement in two eyes in Group A after LASIK, and no improvement in three eyes treated with spectacles in Group B. Two amblyopic eyes had developed ocular deviations by the end of the study that referred to the strabismus unit.
Conclusions: Our outcomes revealed that LASIK was more effective and advantageous than spectacles in the treatment of different types of anisometropia in adults. However, future randomized trials should focus on optical versus surgical treatment of anisometropia and anisometropic amblyopia in both pediatric and adult patients, to verify these conclusions before generalizing this treatment modality.

Background: Presbyopia is the normal progressive waning of accommodation with loss of the visual ability to focus on objects residing at different distances. Presbyopia exacts a cost in quality of life and professional efficiency of many people over 40 years of age. Presbyopia is likely to be 1 of the main pressing visual concerns of the 21st century, given that life expectancy is increasing, resulting in an aging population. This review aimed to address the 3 strategies of the pharmacological treatment for presbyopia.
Methods: A review on PubMed/MEDLINE, Google Scholar, and Clinicaltrials.gov was performed to investigate the English literature on pharmacological treatment for presbyopia from beginning-of-year 2012 to September 30, 2020.
Results: In addition to the treatment of presbyopia with glasses or contact lenses, new surgical strategies have been developed, some of which have been successful. However, during the last decade, a new, promising, non-invasive option for treating presbyopia has emerged: the pharmacological approach. Many researchers have developed 3 different lines of investigation from different assumptions, on a pharmacological basis. The first consisted of producing miosis, to take advantage of a pharmacologically induced pinhole effect, increasing depth-of-focus, and thus improving uncorrected near visual acuity. The second aimed to rehabilitate accommodation binocularly to enable good vision at all distances. Finally, the third approach attempted to rehabilitate lost elasticity in the human crystalline lens.
Conclusions: None of the 3 discussed pharmacological strategies for treating presbyopia, prescribed globally, but patients of restoring accommodation strategy can adhere locally, where they are sold so far as master prescriptions.

Background: The effectiveness of cataract surgery depends on preoperative biometric data, including the axial length (AL), keratometric value (K), anterior chamber depth (ACD), and the accuracy of the intraocular lens power (IOLp) calculation. Five generations of IOLp calculation formulas have been developed. This review summarizes these formulas and focuses on the characteristics, advantages, and disadvantages of each. Moreover, it compares the results of several formulas used in patients with specific characteristics.
Methods: The authors searched PubMed and Google Scholar, using keyword combinations including IOLp, formulas, AL, ACD, K, and diopters (D). Two hundred recent articles that referred to IOLp calculation formulas and their effectiveness when used preoperatively in cataract surgery were retrieved and analyzed.
Results: Each generation has advantages and disadvantages for individual patients, and the selection of the most appropriate IOL differs due to patients’ different ALs. The shorter or longer the eye is, the less accurate some formulas become. Formulas such as SRK-T, Holladay, SRK-II, Hoffer, and Binkhorst II seem to have comparable efficacy. However, studies have indicated that Hoffer is superior for short eyes. In contrast, SRK/T appears to be slightly more superior for long eyes. The fifth-generation formulas also appear to be very promising.
Conclusions: Based on the available literature, there is no gold standard as yet that can be used for all patients. Instead, each patient should be managed individually depending on their particular eye characteristics.

Background: We aimed to evaluate higher-order aberrations (HOAs) following wavefront-guided photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) in patients with myopia and myopic astigmatism.
Methods: This retrospective observational case-control study included patients who underwent wavefront-guided PRK (40 eyes of 20 patients) or LASIK (40 eyes of 20 patients) between August 2018 and November 2018 at the refractive surgery unit of Kayseri City Hospital Eye Clinic, Turkey. The corrected distance visual acuity (CDVA), manifest refraction, corneal topography, and HOAs were evaluated preoperatively and 3 months postoperatively in all patients.
Results: The mean age ± standard deviation (SD) was 27.13 ± 5.54 years and 29.10 ± 4.38 years in the PRK and LASIK groups, respectively (P = 0.06). Both groups had a mean CDVA of 1.00. The mean ± SD of spherical and spherical equivalent values was -2.09 ± 1.56 diopter (D) and -3.03 ± 1.72 D in the PRK group and -2.23 ± 1.69 D and -3.35 ± 1.71 D in the LASIK group, respectively (P = 0.58). When the preoperative and postoperative HOAs and root mean square (RMS) values (for a 6-mm pupil diameter) were compared in the PRK group, a significant difference was found in vertical coma and total RMS values (P = 0.003 and P less than 0.001, respectively); in the LASIK group, there was a significant difference in preoperative and postoperative vertical coma and total RMS values (P = 0.0.001 and P less than 0.001, respectively). There was no significant difference in preoperative and postoperative vertical coma values between the two groups (P = 0.735 and P = 0.583, respectively).
Conclusions: In terms of HOAs, total RMS values decreased significantly and vertical coma values increased significantly at 3 months postoperatively in both PRK and LASIK groups. However, there were no differences between the two groups.