Medical hypothesis, discovery & innovation in optometry

Ocular dominance and refractive error: a cross-sectional study of 400 individuals at a tertiary eye hospital in eastern Nepal

Sanjay Kumar Sah, Sandip Das Sanyam, Pankaj Ray Adhikari, Rajiv Ranjan Karn — Thu, 31 Jul 2025 00:00:00 +0330

Background: Ocular dominance is the consistent preference of using one eye over the other during visual processing, a phenomenon analogous to hand dominance. Ocular dominance often aligns with the eye delivering clearer vision, but does not always correspond to superior visual acuity or refractive status. Mechanisms underlying ocular dominance remain unclear, particularly in individuals whose refractive errors have remained uncorrected since childhood. In this study, we investigated ocular dominance patterns and their association with refractive error and handedness in individuals without early optical correction.

Methods: In this cross-sectional study, we recruited individuals aged 16–40 years with refractive errors, who had no history of spectacle use since childhood, from Biratnagar Eye Hospital, Nepal. Participants underwent anterior and posterior segment examinations using slit-lamp, followed by non-cycloplegic retinoscopy and subjective refraction. Ocular dominance was assessed using the Hole-in-the-Card (Dolman’s) and Miles tests. Hand dominance was determined through standardized questioning and observation during tasks. Spherical equivalents (SEQ) were calculated, and anisometropia was defined as an interocular refractive difference equal or greater than 1.00 D.

Results: Four hundred participants (mean [standard deviation, SD] age 26.1 [6.0] years; 61.3% males) were assessed for ocular and hand dominance. Refractive error SEQ ranged from +9.25 D to –13.50 D (mean [SD] –1.75 [2.46] D). Myopia was most common among students (n = 93, 23.3%) and least common among tailors (n = 14, 3.5%). The most frequent dominance pattern was right-hand combined with right-eye dominance (n = 328, 82%). A strong, statistically significant association was found between ocular and hand dominance (P < 0.01; Cramer’s V= 0.73). Moderate but statistically significant associations were observed between refractive error type and both ocular (P < 0.01; V = 0.25) and hand dominance (P < 0.01; V = 0.21). The dominant eye was not always the eye with better visual acuity. Among the 103 individuals with anisometropia (25.8%), ocular dominance was not consistently accompanied by either the higher refractive error or better visual acuity.

Conclusions: In this study, we demonstrated a strong and statistically significant association between ocular and hand dominance, suggesting existence of a significant lateralization pattern among individuals with refractive error who had no history of spectacle use since childhood. While a right-hand/right-eye dominance pattern was predominant, variations such as cross-dominance and absence of ocular dominance were also observed. A moderate but significant association was found between the type of refractive error and both ocular and hand dominance, indicating that visual and motor lateralization may influence refractive development. The dominant eye did not consistently accompany by better visual acuity or greater refractive error in individuals with anisometropia, underscoring the complexity of ocular dominance and its clinical implications. These findings may aid in understanding visual behavior and inform clinical decisions related to refractive surgeries, amblyopia management, and binocular vision assessments. Further research is needed to explore the underlying neurophysiological mechanisms.

Efficacy of Rose-K lens in enhancing visual acuity and contrast sensitivity in keratoconus

Hussain ALkhalasi , Zoelfigar Dafalla Mohamed — Thu, 31 Jul 2025 00:00:00 +0330

Background: Keratoconus is a progressive, noninflammatory corneal ectasia that is characterized by corneal thinning and conical deformation, which leads to irregular astigmatism, myopia, and reduced visual quality. As the disease progresses, spectacles often become inadequate, necessitating the use of rigid gas-permeable or specialty contact lenses to restore vision. Traditional evaluations rely on high-contrast visual acuity tests, which alone do not capture functional vision impairments. A more comprehensive assessment includes contrast sensitivity (CS), a key predictor of real-world visual performance. The ROSE K2 XL semi-scleral lens offers tailored optical correction for irregular corneas. We investigated its efficacy in enhancing best-corrected distance visual acuity (BCDVA) and CS in patients with keratoconus.

Methods: In this prospective study, we recruited adults with varying keratoconus severities from the Armed Forces Hospital in Oman, between February and December 2024. The patients were fitted with ROSE K2 XL semi-scleral lenses to assess changes in BCDVA and CS. Participants who had undergone prior ocular surgery (except for corneal crosslinking) or who had other corneal pathologies were excluded. Baseline and post-fitting BCDVA were measured using a crowded Keeler logarithm of the minimum angle of resolution (logMAR) chart. CS was assessed using the Pelli–Robson chart under standardized photopic conditions. Keratoconus severity was graded using the Amsler–Krumeich classification system. All examinations were performed by the same experienced optometrist to ensure consistency and to reduce measurement variability.

Results: We enrolled 180 eyes from 90 participants with keratoconus (mean [standard deviation, SD] age: 29.2 [5.4] years; 65.6% [n = 59] female). Disease severity was classified as follows: stage I (n = 16, 8.9%), stage II (n = 52, 28.9%), stage III (n = 70, 38.9%), and stage IV (n = 42, 23.3%). After ROSE K2 XL lens fitting, the mean (SD) BCDVA improved significantly, from 0.90 (0.48) logMAR to 0.10 (0.11) logMAR (P < 0.001). The mean (SD) CS also increased significantly, from 0.96 (0.47) log CS to 1.90 (0.16) log CS (P < 0.001). Significant improvements in BCDVA and CS were observed across all disease stages (all P < 0.001), with the most pronounced gains found in cases of advanced keratoconus (stage IV).

Conclusions: Fitting ROSE K2 XL semi-scleral contact lenses in patients with keratoconus resulted in significant improvements in both BCDVA and CS across all disease severity levels. These findings show the clinical value of semi-scleral lenses for visual rehabilitation of keratoconus, particularly in the advanced stages, where conventional spectacles or lenses may offer limited benefits. Incorporating CS assessment with visual acuity evaluations provides a more comprehensive investigation of real-world visual function, supporting evidence-based lens selection to optimize patient outcomes. Future studies should explore the long-term effects of these lenses on corneal physiology and patient-reported quality of life.

Effect of adjunctive scleral buckling on the outcomes of pars plana vitrectomy in retinal detachment repair

Thu, 31 Jul 2025 00:00:00 +0330

Background: Rhegmatogenous retinal detachment (RRD) is a sight-threatening condition requiring prompt surgical repair. Pars plana vitrectomy (PPV) and scleral buckling (SB) are standard surgical interventions for RRD, but the added value of combining these treatments is debated. While PPV offers enhanced visualization and safety in complex RRD cases, SB may provide additional support in selected scenarios. However, the impact on functional outcomes, particularly contrast sensitivity (CS), remains unclear. In this study, we compared the anatomical success and visual function, including best-corrected distance visual acuity (BCDVA) and CS, between patients with primary RRD who were treated with PPV alone and those who were treated with combined PPV+SB.

Methods: This comparative cross-sectional study included consecutive patients with primary RRD who were treated at Madinah Teaching Hospital, Faisalabad, Pakistan, from October 2020 to July 2021. Participants underwent either 25-gauge PPV or 25-gauge PPV combined with SB, based on their clinical indications. BCDVA and CS were measured monocularly under standardized photopic conditions using the logarithm of the minimum angle of resolution (logMAR) visual acuity chart and the Pelli–Robson chart, respectively. Anatomical reattachment status was assessed by dilated fundus examination. Postoperative evaluations of BCDVA, CS, and anatomical reattachment rate were conducted at 1 day, 1 month, and 3 months after treatment.

Results: Ninety eyes of 90 patients with primary RRD were included (PPV: n = 45 eyes; PPV+SB: n = 45 eyes). The PPV group was approximately a decade younger (45.2 vs. 55.4 years, P < 0.05), while sex distribution was similar in both groups (P > 0.05). Anatomical success rates improved over 3 months, reaching 74.0% (n = 33) for PPV versus 62.2% (n = 28) for PPV+SB. PPV achieved significantly better final BCDVA (2.71 vs. 2.84 logMAR, P < 0.05). CS increased significantly over time in the PPV group (P < 0.05) but remained stable in the PPV+SB group (P > 0.05). Although the final CS was significantly higher in the PPV+SB group compared to the PPV group (P < 0.05), this difference reflected the higher baseline values in the former group. Overall, PPV alone provided greater anatomical and functional improvement over 3 months than did the combined surgery.

Conclusions: Standalone PPV achieved higher anatomical success rates and greater visual acuity improvement over 3 months than did combined PPV+SB, while CS gains favored PPV+SB, but largely reflected higher baseline values. Despite mixed evidence in the literature, our findings suggested that PPV alone may suffice for treating selected uncomplicated RRD cases. Further large, randomized studies are needed to clarify the optimal surgical approach across different patient and RRD profiles.

Outcomes of orthokeratology: a nine-year retrospective review from a university-based optometry clinic in Malaysia

Dawn Le Xuan Lah, Fakhruddin S. Barodawala — Thu, 31 Jul 2025 00:00:00 +0330

Background: Orthokeratology (Ortho-K) is a non-surgical approach to myopia management that uses specially designed gas-permeable lenses to reshape the cornea temporarily and improve vision. While its efficacy is established, real-world data from diverse clinical settings remain limited. In this study we aimed to support evidence-based, individualized Ortho-K practice in routine optometric care by evaluating corneal and visual outcomes, lens designs, and treatment costs at a university-based optometry clinic in Malaysia.

Methods: In this retrospective study, we analyzed clinical records of individuals fitted with Ortho-K lenses at SEGi EyeCare, SEGi University, between January 2015 and October 2024. Eligible individuals were identified via electronic health records and included if they completed key follow-up visits at 1-night, 1–2-weeks, and 1–3-months post-dispensing. Exclusion criteria included incomplete records or missed follow-up visits. Data extracted included unaided distance visual acuity (UADVA) in logarithm of the minimum angle of resolution (logMAR), corneal topography (flat and steep keratometry, eccentricity), pupil size, treatment-zone diameter, age, lens design, and total treatment cost. Measurements were obtained using the Tomey TMS-5 topographer. For each patient, both eyes were analyzed independently.

Results: Data from 30 eyes of 15 patients (mean age and standard deviation [SD]: 23.3 [9.1] years) were analyzed. Significant improvements in corneal curvature and UADVA were observed across follow-up visits (all P < 0.05). Mean (SD) steep keratometry decreased from 43.79 (1.87) D to 42.08 (2.17) D, and flat keratometry from 42.40 (1.61) D to 40.59 (2.31) D at the final visit (both P < 0.05). UADVA improved from 0.93 (0.36) logMAR to 0.23 (0.24) logMAR (P < 0.05) at the final visit. Pupil size and treatment-zone diameter remained stable (both P > 0.05), indicating consistent lens centration. The mean (SD) Ortho-K cost per patient was RM 3736.67 (514.25), equal to USD 846.20.

Conclusions: Ortho-K treatment at this university-based optometry clinic significantly improved corneal curvature, refractive error, and UADVA, with most clinical changes stabilizing within the first month of lens wear. The stability of pupil size and treatment-zone diameter suggests consistent lens performance. These findings affirm the effectiveness of Ortho-K as a non-surgical option for myopia management in real-world practice. Future studies should incorporate axial length measurements and extended follow-up to validate treatment efficacy in slowing myopia progression.

Melatonin as a potential biomarker in diabetic retinopathy

Mahdi Abounoori, SeyedParsa Sajjadifar, Kimia Daneshvar, Mohsen Pourazizi — Thu, 31 Jul 2025 00:00:00 +0330

Background: Diabetic retinopathy (DR) is a major complication of diabetes mellitus (DM). Melatonin protects against inflammation and oxidative stress. This review focuses on the literature comparing melatonin levels in patients with and without DR.

Methods: A thorough search of the PubMed/MEDLINE, Web of Science, and Embase databases was performed for articles published until April 2025. The inclusion criteria were studies reporting melatonin levels in patients with DR and control groups; studies involving human participants of any age, gender, or ethnicity; and investigations documented in scholarly publications. The exclusion criteria were as follows: animal studies; review articles; case reports; editorials; and conference abstracts; studies not available in English or lacking an English translation; and studies focusing on interventions altering melatonin levels rather than comparing levels between patients with DR and controls. Furthermore, we manually checked the reference lists of the included papers to identify any earlier series that were not initially found in our core search. The Newcastle-Ottawa Scale was used to evaluate study quality.

Results: Eight studies with 1004 participants published from 2011 to 2022 were included. The mean age of participants ranged from 39.9 to 72 years. Three studies assessed urinary melatonin excretion, three examined blood melatonin concentrations, one evaluated melatonin concentration in the aqueous humor, and one measured salivary melatonin levels. All samples were collected at night, except for three studies. All studies utilized enzyme-linked immunosorbent assay to measure melatonin concentration, except for the one study, which employed high-performance liquid chromatography. Numerous studies have indicated that patients with DM exhibit reduced melatonin levels relative to healthy controls, and that individuals with DR show lower levels than those without DR. Patients with proliferative DR exhibit reduced nocturnal urinary excretion of 6-sulfatoxymelatonin. Melatonin levels in the aqueous humor were elevated in patients with proliferative DR. Melatonin levels were negatively correlated with both the duration of DM and glycated hemoglobin levels.

Conclusions: The findings of this review suggest that patients with DM, particularly those with DR, exhibit altered melatonin production. Reduced systemic melatonin levels may correlate with increased risk and severity of DR. However, the majority of included studies had a case-control design, which hinders the ability to draw causal conclusions regarding the association between melatonin levels and DR. Moreover, confounding factors, including age, duration of DM, medication use, and lifestyle characteristics of participants, were not uniformly considered, and the limited sample sizes restrict the applicability of the results. Future investigations should emphasize longitudinal studies to clarify the temporal dynamics between melatonin levels and DR progression Additional investigations are required to clarify the function of melatonin in the pathogenesis of DR and its viability as a therapeutic target.

Treatment options for diabetic retinopathy in pregnancy

Mustafa Kayabasi, Omer Karti, Ali Osman Saatci — Thu, 31 Jul 2025 00:00:00 +0330

Letter to the Editor