Comprehensive Vision Evaluation
Primary Care Optometrists provide comprehensive ocular, vision and related care to a diverse population of patients. Students attending Pacific University's College of Optometry begin learning primary care procedures their first semester. During the next two years, techniques for a vision examination are taught. When students enter their third year they begin patient care. Fourth year students spend the full year seeing patients either at preceptorship sites or at one of the school's clinics. During this time, student interns master the skills required to perform a comprehensive vision examination.
The primary care exam sequence can be grouped into four general areas:
- CASE HISTORY
- REFRACTIVE STATUS (near-sighted, far-sighted, etc.)
- BINOCULAR & ACCOMODATIVE STATUS (eye-teaming and focusing ability)
- OCULAR HEALTH
The exam sequence begins with a case history. This is an important part of the examination as it can indicate what the problem may be even before any testing is completed. History is obtained in the following areas:
- chief complaint
- visual and ocular history
- general health history
- medication usage
- allergies to medications
- family eye and medical histories occupational visual requirements recreational visual requirements
Depending on responses during the case history, the standardized examination can be customized to fit the needs of the patient. Following the case history, the exam continues by assessing the visual acuity of the patient.
Visual Acuity is taken at the beginning of each office visit and is used as one of the techniques to monitor the patient's current visual status. Acuities are tested by having the patient report what can be seen in the distance and at near with and without their current correction. In most cases, a standard Snellen Acuity Chart is used as the target.
Entrance Tests are used to initially define the patient's visual abilities, ocular health and related systemic health status. The following areas are assessed:
- patient appearance-a head tilt or turn can be a clue to an eye problem such as a compromised extraocular muscle.
- external ocular and facial areas-signs such as excessive forehead wrinkling, lid droop or squinting give clues to ocular problems.
- pupillary responses-changes or alterations in pupil size, shape or reaction to light serve as important diagnostic clues when assessing a patient's visual and neurological functioning.
- ocular motility tests-eye movements are tested at near using a fixation bead to assess extraocular muscle function.
- cover tests-provide information about eye alignment.
- near point of convergence-the closest point at which both eyes together are able to see a single image.
- near point of accommodation-the closest point at which the image is seen clearly.
- stereopsis-provides information about the ability to see three dimentionally.
- color vision-can provide clues to some retinal diseases or inherited color vision abnormalities.
- confrontation fields-screening test for peripheral vision.
The keratometer is an instrument used to measure the curvature of the front surface of the cornea. Findings are used when fitting contact lenses and are an initial indicator of astigmatism.
When evaluating the refractive status (near sightedness, farsightedness, etc.) of the patient, students at Pacific University are taught a battery of tests. Depending on a patient's ocular complaints, a customized examination is given drawing on this battery of tests. When analyzing the refractive error, both subjective and objective sources of information are combined to determine the patient's ideal lens correction.
Several of the tests used during a vision exam are done using the phoropter, an instrument equipped with numerous lenses that can be used to find a specific lens combination that will provide clear and comfortable vision for the patient.
Retinoscopy is an objective method used to measure refractive error. It is useful in establishing a baseline or reference point from which to begin the refraction portion of the examination. It is especially useful with infants, nonverbal patients, and difficult refractive cases.
After retinoscopy has been completed, the patient is given a series of lens choices. This process helps fine tune the lenses that the patient likes best for both distance and near viewing. When the end point of this portion of the refraction has been reached, the patient's visual acuity is re-tested. Once the lens combination providing the best visual acuity is in place, the exam continues with an assessment of the patient's binocular and accomodative status.
BINOCULAR AND ACCOMMODATIVE STATUS
Eye-Teaming and Eye-Focusing
Additional tests for binocular function and accommodation (focusing ability) are incorporated into the examination depending on a patient's chief complaint, work and recreation requirements, age, and results of entrance testing.
With the lens combination providing the best visual acuity and most comfort in place, tests are conducted to evaluate the eye-teaming and focusing ability of the eyes. Results from these tests can uncover functional vision problems. For example, if a patient has an eye-teaming or binocular problem, he/she may experience difficulty seeing an object as single. What can result is double vision or fatigue when reading. An example of an eye focusing problem occurs when a patient sees blur in the distance after reading for a while.
OCULAR HEALTH EVALUATION
This technique provides a view of the retina, optic nerve and ocular media (cornea, lens, vitreous, etc). It can be used with a non-dilated pupil, however the field of view is smaller as compared to other fundus viewing techniques (such as BIO, see below).
Biomicroscopy "Slit Lamp"
The slit lamp provides a magnified, three dimentional view of the ocular structures and the surrounding tissues. It is used to perform ocular health assessments which include evaluation of:
* fit and management of contact lenses
As proficiency increases, additional techniques are added so that by the end of the students' training, the slit lamp can be used to assess the following:
Applanation Tonometry (Goldman)
Using the tonometry attachment, the slit lamp can be used to measure the intraocular pressure (IOP) of the eye. This is one of the tests used to evaluate the presence or absence of glaucoma.
This is a technique in which a contact lens with mirrors is used to evaluate the anterior chamber angle, a structure not visible otherwise. This method of angle examination is used when an angle is very narrow. If a narrow angle closes off, there is a risk of a pressure increase which can cause damage to the eye.
High Plus Lens Examination
When using a high magnification lens with the slit lamp, a highly detailed stereoscopic view of the retina and vitreous is possible. This type of view is crucial when examining these structures for evidence of disease.
Binocular Indirect Ophthalmoscopy (BIO)
BIO is a technique used to evaluate the entire retina and vitreous. Since both eyes are used, it provides a three dimentional view as opposed to the direct ophthalmoscope which provides a two dimentional view. BIO typically requires the pupils to be dilated.
Having completed a vision analysis, an assessment of the findings is given to the patient and a plan is presented. This plan could include a prescription for glasses or contact lenses, further testing, treatment of a disease or disorder, or a referral to another health care specialist.