What is glaucoma?
Glaucoma effects millions of individuals in the United States, but over half of glaucoma patients don't know they have it. Although advanced technology is essential to detect this disease early, the sooner it is diagnosed, the lower the risk of eventual blindness.
The optic nerve connects the eyeball to the brain. In glaucoma, high pressure in the eye pushes on the optic nerve, causing damage to it. As the optic nerve becomes damaged, you begin to lose vision in the periphery. You don't notice it as first, but eventually it can cause tunnel vision and complete blindness.
Normal Vision Advanced Glaucoma
As this damage to the optic nerve occurs, the appearance of the optic nerve changes. As we look at the optic nerve from our microscope in the exam room, it looks like a disk with blood vessels coming out of a crater in the middle of it. This crater is called the "optic cup". Everyone has different degrees of optic cupping, but in glaucoma the optic cup always gets deeper and deeper. So when we see someone with deep optic cups, we don't know just by looking at it if the cups our deep naturally, with no loss of vision, or if they're deep because of glaucoma. Advanced testing needs to be done.
Testing for Glaucoma
There are several tests for glaucoma. The first test is tonometry to measure intraocular pressure. Most optometric practices utilize "air puff" technology. While this doesn't require an eyedrop to be instilled in the eye, most patients dislike the anticipation of the air puff, and most glaucoma specialists see the air puff as just a screening test.
Here at Sonoran Desert Eye Center, we use applanation or Goldmann Tonometry. Golmann Tonometry is aptly named, as it is the gold standard in measuring intraocular pressure. A yellow numbing drop is instilled in the eye, a blue light is shined onto a probe that gently touches the anterior surface of the cornea, and the examiner adjusts a dial to determine the pressure. As a patient, you don't feel anything and there is no damage to the cornea. Patients prefer Goldmann Tonometry to air puff tonometry.
Measurements of pressure in the eye can be effected by the thickness of the cornea. In patients with thin corneas, we read the pressures to be lower than they truly are, and in thick corneas, we read the pressures to be higher than they truly are. For appropriate diagnosis of glaucoma, the cornea thickness has to be measured using a device called a pachymeter. A numbing drop is put in the eye and a probe is gently touched to the surface of the cornea. The patient feels nothing. The examiner uses the pachymetry reading as another risk factor for glaucoma.
Normal pressure in the eye ranges from 9mmHg to 24mmHg. The average is 15mmHg. However, many individuals with intraocular pressures up to 30mmHg never have any damage from glaucoma, while others with pressures in the mid teens do. So we can't go by pressure measurements alone.
Slit lamp examination enables the doctor to look at the optic nerve cupping. As mentioned earlier, cupping can range from 0 to 1.0. Most normal individuals have a cupping of .3, but can range from 0 to .8 with no glaucoma. We start becoming alerted to the possibility of glaucoma in most individuals when the cupping reaches about 55.
Visual field testing is performed on an individual with optic nerve cupping and/or high intraocular pressure. At Sonoran Desert Eye Center, we use the Humphrey Visual Field Analyzer. It's a white bowl, one eye is covered, your chin is placed in a chin rest, and the machine flashes lights of various intensities and sizes in the bowl. You push a button when you think you see the light. Both eyes are tested and then the computer gives a printout of how well you see in the periphery. Usually, any defects are confirmed weeks later with a retest, since there can initially be errors in testing.
Treatment for Glaucoma
Treatment for glaucoma is generally very straightforward. It consists, in most cases, of eye drops that you instill in your eyes at bedtime. The goal is to lower the pressure in the eye a certain percentage, depending on the severity of your glaucoma. If one eyedrop alone is not, other eyedrops can be added.
If combinations of eyedrops do not lower the pressure enough, and if the glaucoma is severe enough, surgery is performed. There are laser surgeries if small degrees of pressure lowering is desirable and the glaucoma is not too severe. There are more advanced surgeries such as trabeculectomy, which creates a hole for fluid to leave the eye. For more advanced glaucoma, there are valves and shunts that can be surgically placed in the eye.
The key to successful glaucoma treatment is early detection and patient compliance with treatment eye drops and follow-ups. Depending on the severity of glaucoma and your response to treatment, follow-ups will vary, but generally a glaucoma patient follows-up in the clinic every 4 months.
While both optometrists and ophthalmologists are licensed to manage glaucoma, it is essential that the doctor feels comfortable diagnosing and treating glaucoma. Not all doctors of either profession are comfortable managing glaucoma, since most optometrist would rather manage visual problems and most ophthalmologists would rather manage cataract and refractive surgeries. Dr. Quaranta has spent over ten years managing thousands of glaucoma patients in Arizona and can diagnose and treat most cases. Above all else that he does, he enjoys managing glaucoma. He co-manages difficult cases with his mentor, Dr. John Lewis at Southwestern Eye Center.
Glaucoma testing is a part of regular eye examinations here at Sonoran Desert Eye Center. You can rest assured that you are in good hands with our doctor in our clinic.