Comprehensive Eye Exams
Thorough evaluations of your vision and eye health, with screening for common conditions and early changes.
Comprehensive Eye Care · Rio Grande Valley
Clear vision, Expert Eye Care — for the Rio Grande Valley.
Full-service eye care from Dr. Errol O. Grannum for your whole family, with locations in Harlingen and McAllen.
From routine exams to advanced glaucoma care, experience personalized, bilingual eye care.
We protect and improve the way you see. Proudly serving the Rio Grande Valley since 1998.
Welcome to South Texas Eye Care
At South Texas Eye Care, we provide the full range of medical and surgical eye care for patients of every age — from comprehensive eye exams and cataract evaluation to diabetic eye care and dry eye treatment. Using advanced diagnostic technology, Dr. Errol O. Grannum delivers personalized, one-on-one care focused on understanding your eyes and your goals.
Our practice has deep roots in the South Texas community, and among our recognized strengths is a specialty focus on the diagnosis and management of glaucoma. Whether you need a routine check-up or specialized care, our team is here to help you see your best at both our Harlingen and McAllen offices.
Bilingual We proudly serve patients in English and Spanish.
A Specialty Focus
Glaucoma care, one of our featured specialties
While we provide complete ophthalmic care, South Texas Eye Care is recognized for our advanced capabilities in glaucoma diagnosis and management.
What is glaucoma?
Glaucoma is a group of eye conditions in which fluid pressure builds inside the eye and gradually affects the optic nerve, which carries images from your eye to your brain. The most common type, open-angle glaucoma, develops slowly and silently over time.
The “silent thief of sight”
Early glaucoma often has no symptoms at all, and vision that is lost to it cannot be recovered. That is why regular comprehensive eye exams and early detection matter so much — they allow us to find and address changes before they affect your daily life.
Who is at higher risk?
- Adults over 60 — including Hispanic and Mexican-American populations, who carry elevated risk (relevant across the RGV)
- People living with diabetes
- Anyone with a family history of glaucoma
- African-American adults over 40
How we diagnose & treat it
Diagnosis begins with a comprehensive exam, eye-pressure testing, and optic-nerve imaging or visual-field testing. When treatment is needed, options can include medicated eye drops, laser procedures (such as SLT — selective laser trabeculoplasty — or laser iridotomy), minimally invasive glaucoma surgery (MIGS), and traditional surgical options when appropriate.
There is no cure for glaucoma, but early diagnosis and consistent, ongoing management can help preserve your vision and slow its progression. The most important step is simply getting evaluated.
Schedule a Glaucoma Evaluation
Services & Conditions We Treat
Complete eye care, all in one practice
From everyday vision needs to specialized medical and surgical care — with glaucoma management as a featured strength.
Glaucoma Diagnosis & Management
A featured area of expertise: pressure testing, optic-nerve imaging, medical, laser, and surgical options.
Cataract Evaluation & Surgery
Evaluation and modern treatment for clouded lenses that blur vision and dull color and contrast.
Diabetic Eye Care
Monitoring and management of diabetic retinopathy to help protect vision for patients with diabetes.
Dry Eye Treatment
Relief for burning, gritty, or watery eyes with a plan tailored to the cause of your symptoms.
Macular Degeneration
Evaluation and ongoing care for age-related changes affecting central vision.
Laser Eye Procedures
In-office laser treatments including SLT, YAG, and iridotomy, performed with precision and care.
Medical & Surgical Eye Care
The full range of medical and surgical care to diagnose, treat, and manage conditions of the eye.
Meet Your Physician
Request an appointment with Dr. Grannum
Dr. Errol O. Grannum, MD
Board-Certified Ophthalmologist
Glaucoma Specialist
Fellowship-Trained
Bilingual Care (EN / ES)
Serving the RGV Since 1998
Education & Training
- Undergraduate — B.S. in Electrical Engineering, Massachusetts Institute of Technology (MIT)
- Medical School — Yale University
- Fellowship — University of Southern California
Dr. Errol O. Grannum brings a rare blend of engineering precision and medical expertise to eye care. After earning his Bachelor's degree in Electrical Engineering from MIT, he completed his medical degree at Yale University and fellowship training at the University of Southern California.
For nearly three decades, Dr. Grannum has proudly cared for the Rio Grande Valley, offering comprehensive ophthalmic services with a recognized focus on the diagnosis and management of glaucoma.
Patients value his attentive, unhurried approach and his commitment to making sure every person — in both English and Spanish — fully understands their eye health.
Why Choose Us
Trusted, personal eye care close to home
Full-service for the family
Comprehensive eye care for every age, from children's vision to senior eye health.
Advanced Glaucoma Care
State-of-the-art diagnostic imaging and early-detection tools to monitor and manage glaucoma accurately.
Community Rooted — Two convenient locations
Proudly bilingual and dedicated to serving the diverse population of the Rio Grande Valley with compassion.
Personalized & Unhurried
We take the time to answer your questions transparently, ensuring you understand your eye health entirely.
A Look Inside
Inside our practice
A glimpse of the type of offices and equipment you'd expect to see during a visit as well as the team caring for you.
In Our Patients' Words
What patients say
At South Texas Eye Care, we pride ourselves on delivering premium attention and service to our wonderful patients.
Request an Appointment
Let's get you scheduled
Share a few details and our team will reach out to confirm a time at the location that works best for you.
Thank you — your request has been received
Our team will reach out using the contact details you provided to confirm a date and time. There's nothing more you need to do right now; we look forward to seeing you.
For medical emergencies or sudden vision loss, call 911 or go to the nearest emergency room.
Protecting your vision starts with a visit
Whether it's a routine exam or specialized glaucoma care, we're ready to help you see your best.
Request an Appointment
Our Locations
Two offices across the Rio Grande Valley
Harlingen Office
1645 Treasure Hills Blvd, Harlingen, TX 78550
Mon–Sat: 8:00 AM – 5:00 PM
McAllen Office
2010 S Cynthia St STE 107, McAllen, TX 78503
Mon–Sat: 8:00 AM – 5:00 PM
Frequently Asked Questions
Answers to common questions
A few things patients often ask before their visit. If you don't see your question here, please reach out — we're glad to help.
For most visits, you don't need a referral. Some insurance plans — especially HMOs — do require a referral from your primary care provider before seeing a specialist, so we recommend checking with your plan. If you're unsure, give us a call and we'll help you find out.
We accept a range of major insurance plans, including those listed below. Coverage can vary by individual plan, so please call our office with your insurance details and we'll be glad to verify your benefits before your visit.
- Blue Cross Blue Shield — Medicare, PPO
- Cigna — PPO
- Elevance — EPO, HMO, Medicaid, Medicare, POS, PPO
- HCSC — HMO
- Humana — Medicare, PPO
- Molina — HMO, Medicare
- Regence Health Plans — PPO
Don't see your plan? Call us — this list isn't exhaustive and we're happy to check.
Please bring a photo ID, your insurance card, a list of any medications you take, and your current glasses or contact lenses. If you've seen another eye doctor, any records or a referral (if your plan requires one) are helpful. Because some exams include dilation, you may want to bring sunglasses and consider arranging a ride home.
Plan for about an hour for a comprehensive exam. Many exams include dilating drops, which can leave your vision blurry and more sensitive to light for a few hours afterward, so it's a good idea to bring sunglasses and, if possible, have someone available to drive you.
As a general guide, adults with no known problems benefit from an exam every one to two years, and once a year if you're over 60 or have diabetes, a family history of glaucoma, or other risk factors. Dr. Grannum will recommend a schedule tailored to your eyes and overall health.
Yes. Early glaucoma often has no symptoms at all, which is why it's called the “silent thief of sight.” A comprehensive exam with eye-pressure testing and an evaluation of the optic nerve is the most reliable way to detect it early — when it's most treatable.
There's no cure, but with early diagnosis and consistent management — medicated drops, laser, or surgery as needed — most people are able to preserve their vision and slow the disease's progression.
Yes — we proudly provide care in both English and Spanish, so you and your family can feel comfortable and fully understand your eye health.
Contact Us
Get in touch
Call Us
Harlingen & McAllen:
(956) 687-3937
Visit Us
1645 Treasure Hills Blvd, Harlingen, TX 78550
2010 S Cynthia St STE 107, McAllen, TX 78503