Assessment of Color Vision and Stereopsis in Patients With Normal Tension Glaucoma Presenting at Al Ehsan Welfare Eye Hospital

Background: Glaucoma is a progressive optic neuropathy and a leading cause of irreversible blindness worldwide, with an estimated 60 million cases in 2010 that rose to nearly 80 million by 2020. It may occur with or without elevated intraocular pressure (IOP) and often remains undetected until late stages. Normal tension glaucoma (NTG), a subtype of open-angle glaucoma, presents unique diagnostic challenges. Early detection through functional assessments such as color vision and stereopsis evaluation is critical for timely intervention and preservation of visual quality. Objective: This study aimed to determine the impact of NTG on color vision and stereopsis and to identify the type of color vision deficiency most frequently observed in young adults with NTG. Methods: A cross-sectional study was conducted on 93 NTG patients aged 15–35 years, including 61 males and 32 females, over a period of four months at Al Ehsan Welfare Eye Hospital, Lahore. Patients fulfilling the inclusion criteria underwent visual assessment. Visual acuity was measured with a Snellen chart and recorded in logMAR units. Color vision was analyzed using the Farnsworth D-15 test, while stereopsis was evaluated using the Titmus Fly Test. Intraocular pressure was assessed through applanation tonometry, and cup-to-disc ratio was documented by ophthalmoscopy. Results: Visual acuity analysis revealed mean values of 0.4153 for the right eye (OD) and 0.4409 for the left eye (OS). Color vision testing of the right eye showed 71 patients (76.3%) normal, 15 (16.1%) deutan deficiency, 5 (5.4%) protan deficiency, and 2 (2.2%) tritan deficiency. In the left eye, 63 patients (67.7%) had normal color vision, 18 (19.4%) deutan deficiency, 11 (11.8%) protan deficiency, and 1 (1.1%) tritan deficiency. Stereopsis ranged between 40 and 200 seconds of arc, with a mean of 91.61 and a standard deviation of ±34.74. Conclusion: This study demonstrated that NTG impairs functional visual parameters, with deutan deficiency being the most common color vision anomaly and significant stereopsis variability indicating depth perception compromise. Incorporating color vision and stereopsis testing into clinical evaluation may enable earlier diagnosis and enhance targeted management of NTG in young adults.