Red, Swollen Eyes with Blood Vessels in Dogs: Distinguishing Conjunctivitis from Corneal Ulcers

When your dog's eyes appear red, swollen, or have visible discharge, it can be difficult to determine whether it's mild conjunctivitis or a corneal ulcer requiring urgent treatment. Understanding the differences between these conditions helps you make the right decision quickly, preventing delayed treatment that could affect your dog's vision.

## Conjunctivitis: The Most Common Eye Problem

Conjunctivitis is the most common cause of red, swollen eyes in dogs, referring to inflammation and redness of the conjunctiva (the white part of the eye).

**Common Symptoms:**
* Bloodshot, red sclera
* Yellow or green mucus discharge
* Frequent blinking or squinting
* Pawing at the eye area

**Possible Causes:**
* Bacterial, viral, or fungal infections
* Allergic reactions (pollen, dust, etc.)
* Foreign body irritation or ingrown eyelashes
* Friction caused by dry eye syndrome

It's worth noting that conjunctivitis in dogs is usually non-infectious, while in cats it's predominantly infectious.

## Corneal Ulcers: A Warning Sign Not to Be Ignored

Corneal ulcers involve damage or erosion of the corneal surface and are more serious than conjunctivitis. Without timely treatment, they can cause permanent vision damage.

**Typical Symptoms:**
* Excessive tearing
* Severe light sensitivity, avoiding bright lights
* Cloudy or hazy cornea
* Obvious pain with frequent blinking

**High-Risk Breeds:**
Brachycephalic breeds such as Shih Tzus, Bulldogs, Pugs, and Pekingese have more prominent eyes and incomplete eyelid closure, making their corneas prone to injury or dryness and putting them at higher risk for corneal ulcers.

## How to Make a Preliminary Assessment

| Feature | Conjunctivitis | Corneal Ulcer |
|---------|---------------|---------------|
| Pain Level | Mild discomfort | Obvious pain |
| Corneal Appearance | Clear and transparent | Cloudy or hazy |
| Light Sensitivity | Not obvious | Very obvious |
| Discharge | Yellow-green mucus | Excessive tears |

Veterinarians use fluorescein dye to examine the cornea—if an ulcer is present, it will glow fluorescent green. This is the most accurate diagnostic method.

## Home Observation and When to See a Vet

**Situations Where You Can Observe First:**
* Mild redness with normal energy and appetite
* No obvious pain or light sensitivity
* Discharge is clear or light yellow

**Situations Requiring Immediate Veterinary Care:**
* Cornea appears cloudy or hazy
* Dog constantly pawing at the eye
* Eye completely unable to open
* Symptoms persist for more than 24 hours without improvement

Eye conditions often present with similar clinical symptoms. When you cannot determine the cause, seek veterinary examination promptly. With proper eye drop use and regular follow-ups, significant improvement typically occurs within one week.

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**References:**
* [Common Dog Eye Redness Issues | How to Handle Conjunctivitis - MomoVet](https://momovet.com/2022/03/25/dogconjunctivitis/)
* [A Must-Read Guide on Corneal Ulcers in Dogs and Cats - Wuo Wuo](https://wuo-wuo.com/report/42-pet/1069-eye-191126)
* [What to Do About Red, Swollen Eyes in Dogs? - Moreson](https://www.moreson.com.tw/moreson/blog-detail/furkid-knowledge/pet-Illness-and-medical/dog-eye-swelling/)

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