Diseases & Conditions

This link from the National Institute of Health (NIH) and the National Eye Institue (NEI) gives patients information about Age Related Macular Degeneration, from basic, to more in depth studies. Fundus photo below shows a retina with dry type macular degeneration. The dry type is more common than the wet type, in which there is unwanted growth of pathological blood vessels. There is a genetic link to this disease--parents with ARMD have 30% chance of passing it on to their children. Various new therapies attempt to limit neovascularization in the wet type ARMD, using lasers or injections of Anti-Vascular Endothelial Growth Factor (VEGF causes the unwanted vessels to grow in disease process). The Age-Related Eye Disease Study (AREDS) - sponsored by the Federal government's National Eye Institute that was published in a 2001 article in Archives of Opththalmology found that taking high levels of antioxidants and zinc can reduce the risk of developing advanced age-related macular degeneration (AMD) by about 25 percent.This major clinical trial closely followed about 3600 participants with varying stages of AMD. The results showed that the AREDS formulation, while not a cure for AMD, may play a key role in helping people at high risk for developing advanced AMD keep their remaining vision.

 The dry type of ARMD is less serious and the only therapy is daily supplemental oral vitamins containing antioxidants and zinc.  Several companies make formulation available specifically for people at risk, which includes, in addition to the vitamins and minerals in the AREDS study, Lutein and Zeaxanthin, which are primary carotenoids found in the retina and which some believe may be appropriate for people with frequent exposure to sunlight.     In addition to the NEI site, information about the disease is also available from the Macular Degeneration Partnership (www.AMD.org).

Astigmatism is a common vision condition that occurs when either the front surface of the eye, the cornea is slightly irregular in shape (corneal astigmatism), or the crystalline lens located within the eye just behind the cornea, is irregular in shape (lenticular astigmatism). Various objects have been used to describe this distorted shape.  If we think of the normal cornea as being spherical like the side of a basketball or soccer ball, then the cornea that has an astigmatic shape might be considered as being like the shape of the side on an American football, or a teaspoon.  The curvature is different in each orientation or direction. This irregular shape of the cornea prevents light from focusing properly on the photoreceptive cells located in the retina in the back of the eye. As a result, vision may be blurred at all distances. 

The name astigmatism is derived from "a", meaning without, and "stigma", meaning point, because in the condition of astigmatism, light is not focused to a point.

In the most common type of astigmatism, regular astigmatism, the curvature of the cornea or crystalline is greater in one direction than it is 90 degrees away from that direction. There is also a condition known as irregular astigmatism when the curves of greater and lesser curvature are not 90 degrees apart, but this is usually the result of corneal diseases such as Keratoconus or from corneal injury.  Regular astigmatism is the natural occurring form and is one of the most common vision problems that people have. The result is that objects appear brighter or sharper focus in one direction than they are in another direction 90 degrees away. Vertical lines may appear sharper than horizontal lines, or vice versa.  The lines that our out of focus might be in any direction.  This direction corresponds to the direction in the cornea or crystalline lens that is either flatter or steeper than the curvature of cornea or crystalline lens 90 degrees away.  The direction of blur is called the axis of astigmatism and the amount is called the cylinder.

Someone with uncorrected astigmatism might see a figure of radial lines of equal darkness in a distorted manner, such as the figure pictured to the left. If we consider the lines as pointing to numbers on a clock, if all the lines were the same darkness, a person with astigmatism with axis in the direction of 4:00 to 10:00 would see the lines less clear in the 4:00 to 10:00 direction than the lines in the 2:00 to 8:00 direction. (The illustration to the left is from the website The Joy of Visual Perception at www.yorku.ca/eye). When the lens prescription is written to correct the condition, the direction of astigmatism, the axis, is expressed in degrees of a semicircle, with the lines in the 3:00-9:00 o'clock direction expressed as the 180 degree axis, the lines in the 12:00-9:00 o'clock direction expressed as axis 90 degrees and the lines around the clock dial in between expressed as other degrees between 0 and 180.  The distortion in the cornea or crystalline lens in astigmatic eyes causes light to focus either in front or in back of the retina. Corrective cylinder lenses focus all the light in the same place precisely on the retina, as it is in a normal eye.

Cataract is a clouding of the crystalline lens within the eye.  Clicking on the underlined title above takes you to the National Institute of Health patient guide to cataracts and cataract surgeries. Cataracts are a very common condition of aging, but can be present at birth (congenital), or caused by trauma, exposure to ultra violet light, and exacerbated by medications and other diseases.  Along with the clouding, there can also be a change of thickness of the crystalline lens, and a change in the refractive error  of the eye associated with cataracts.  If the clouding is not too bad, the refractive changes, such as an increase in myopia, can be alleviated by changing the prescription in eyeglasses or contact lenses. Cataract surgery is usually done when patients complain about their best corrected vision--the glasses no longer provide adequate vision.  If the clouding progresses and vision is further diminished, the patient is referred  to a cataract surgeon to have the cataract removed surgically using a procedure called phacomulcification (or phaco), and at the same time a man-made replacement lens (IOL or Intra Ocular Lens) is placed in the eye, usually within the lens capsule (or bag), which is located directly posterior (behind) the iris. IOLs placed within the capsule are referred to as posterior IOLs.  Sometimes IOLs are placed anterior to (in front of) the iris and called a anterior IOLs.  Anterior IOLs are used when the lens capsule is missing or sometimes in young healthy phakic eyes (eyes with intact crystalline lens). The phakic eyes would be ones  without cataracts, and the procedure is done  as a form of refractive surgery in younger patients with  high amounts of refractive error.  When patients are older and develop cataracts the anterior IOL is removed along with the cataract and replaced with a posterior IOL.  If the capsule is intact the  most common procedure in cataract surgery is phaco with posterior IOL done as an outpatient procedure by the surgeon. Very few complications are seen with this procedure, and the most common complication macular edema is  almost always successfully treated with eye drop medications. In fact, a majority of senior citizens have successful cataract surgery done at some point in their life. Because the IOL has refractive power, the vision most patients obtain after cataract surgery is often better than the vision the patient had before the cataract, especially if the patient had a significant refractive error (myopia or hyperopia) before having the cataract.  It is not uncommon for patients who have put off having the first eye done for fear of surgery, to rush to have the second eye done as soon as possible. For video of this procedure click here  (requires Flash plug-in). Generally the power of the IOL corrects the distance vision of the patient and reading glasses are still needed for close vision following cataract surgery.  

Several multifocal IOLs are now available. There are two ways that a near focus can be put into an IOL along with a distance focus--either by putting multiple focus segments in the lens (like multifocal or bifocal lenses in glasses and contact lenses), or by having the lens accomodate by changing its shape or position in the eye--accomodating like a young natural crystalline lens.   The Crystalens® (seen below) is the first and only accomodating lens. It was first approved by the FDA in November, 2003, and new and better versions of it have been developed since then. The newest version, Crystalens HD™ has improved optics and was approved by the FDA in 2008. The hinged hapics, or carrier, of the Crystalens® is flexible, and moved by the ciliary muscle of the eye  often eliminating the need for post-op reading glasses.

Another multifocal implant device is the Alcon AcrySof® ReSTOR® IOL , often referred to as the "ReStor" lens.  This multifocal IOL is placed in the lens capsule similar to traditional single vision IOLs, but the lens has concentric circular rings, which act as a diffraction grating to incorporate distance, intermediate and near focuses into the lenses.  Other IOLs in this category are the Array and ReZoom™ lenses (both made by Advance Medical Optics).  The concentric ring design is able to bring more near focus into these lenses than the accomodating Crystalens™., but people sometimes find that their distance vision isn't as good because there may be glare at night caused by the rings. There also is a difference between how near and intermediate distances are perceived when comparing the ReSTOR® and  the  ReZoom™ designs, with the ReSTOR® perhaps being better for near and the ReZoom™   providing better intermediate vision.  It is not uncommon for surgeons to put different type of mulifocal IOLs in each eye to try to balance the positives and negative affects of each. The mulifocal IOLs correct myopic, hyperopic, and presbyiopic refreactive errors of the eye, but they do not correct astigmatism. All of these multifocal devices are considered premium options by insurance companies and Medicare, and patients must pay  a premium charge for these lenses, above and beyond insurance imbursements for standard single vision IOLs used in cataract surgery. To correct for astigmatism it is possible to do an ancillary procedure along with the IOL, such as LASIK surgery.

Dr Elman is not a surgeon, but as an optometrist he examins  for cataracts, and once they are diagnosed he makes  recommendations and referrals for treatment, included pre and post op exams for various IOLs.  It is important for patients to be followed after these surgical procedures for possible complications.

This links to a website about color blindness or, more correctly, color deficiency. It was created by Frank Dutton, a web designer in Louisiana.  Briefly, it describes the condition, causes, and effects of color deficiency. The primary purpose, however, is to furnish a set of color charts to aid the color blind in working with computer colors, most especially on the internet and in web sites. There is also some really nice software (shareware/freeware) here for checking colors onscreen on your computer - great for anyone, but especially for the colorblind! An example of a test chart for color deficiency is shown to the right. The individual with normal color vision will see a square and circle revealed in the dot pattern. An individual with Red/Green (the most common) color blindness will see only the circle revealed in the dots. -- Dr E

Microbial keratitis is a severe infection of the cornea. Risk factors for infection include trauma (generally with plant material), chronic ocular surface diseases, immunodeficiencies, and rarely, contact lens use (1--3). An estimated 30 million persons in the United States wear soft contact lenses; the annual incidence of microbial keratitis is estimated to be 4--21 per 10,000 soft contact lens users, depending on whether users wear lenses overnight (4). Fungal keratitis is a condition more prevalent in warm climates; in the southernmost United States, up to 35% of microbial keratitis cases are fungal keratitis, compared with 1% in New York (5,6). In the first quarter of 2006 there were a number of patients that were diagnosed with fusarium keratitis who had used B & L ReNu contact lens solution (6).  The proportion of fungal keratitis attributable to Fusarium spp. also varies by region, from 25% to 62% (1,2,5). First-line treatment includes topical and oral antifungal medications; patients who do not respond to medical treatment usually require surgical intervention, including corneal transplantation (3). Fusarium keratitis is not transmitted from person to person.

References

1. Rosa RH Jr, Miller D, Alfonso EC. The changing spectrum of fungal keratitis in south Florida. Ophthalmology 1994;101:1005--13.
2. Tanure MA, Cohen EJ, Sudesh S, Rapuano CJ, Laibson PR. Spectrum of fungal keratitis at Wills Eye Hospital, Philadelphia, Pennsylvania. Cornea 2000;19:307--12.
3. Thomas PA. Fungal infections of the cornea. Eye 2003;17:852--62.
4. Poggio EC, Glynn RJ, Schein OD, et al. The incidence of ulcerative keratitis among users of daily-wear and extended-wear soft contact lenses. N Engl J Med 1989;321:779--83.
5. Liesegang TJ, Forster PK. Spectrum of microbial keratitis in south Florida. Am J Ophthalmol 1980;90:38--47.
6. MA Barry, MD, J Pendarvis, MPH, Boston Public Health Commission, et al. Fusarium Keratitis --- Multiple States, 2006 CDC Dispatch April 10, 2006

Common signs of farsightedness include difficulty in concentrating and maintaining a clear focus on near objects, eye strain, fatigue and/or headaches after close work, aching or burning eyes, irritability or nervousness after sustained concentration. The illustration for this is from the American Optometric Association.

by John W. Elman, OD

Presbyopia is an age related vision condition in which the crystalline lens of the eye has lost a significant amount of  its flexibility,  making it difficult for the presbyope to focus on close objects, even though distance vision is unaffected. Presbyopia is a natural part of the aging process of the eye. It is not a disease and it cannot be prevented.

Presbyopia may seem to occur suddenly, but the actual loss of flexibility takes place over a number of years. Presbyopia usually becomes noticeable in the early to mid-forties. See the section on this website titled  How the eye focuses on near objects for a more detailed explanation of the loss of flexibity of the crystalline lens that occurs with aging.

Presbyopia may occur without any previous eye condtions, or it may occur in combination with preexisting conditions, such as astigmatism, myopia or hyperopia.   The presbyope who previously had hyperopia (farsightedness), will continue to have hyperopia, but will find that more power is now needed in corrective lenses for near vision, as  well as the power needed for distance vision, and that in addition to a problem with close vision,  distance vision is also worse than it was.  For those who were previously myopic, or nearsighted, presbyopia makes near vision worse while wearing the myopic distance corrective lenses, even though the younger myope previously could see clearly at all distances with corrective lenses. Occasionally myopic presbyopes experience better distance vision than previously, with a concurrent decrease in their myopic lens prescription power. Those with astigmatism continue to have that condition, but find that the lens power that worked for distance vision no longer works for near vision.

Treatment for presbyopia usually requires wearing glasses and/or contact lenses, which allow for a different focus for near and distance. The option may be reading glasses, which are removed for distance, or multifocal lenses, such as bifocals, trifocals, progressive additions and other options. These type lenses are divided into two or more sections and each section of the lens has a different power which focuses at different distances.   When contact lenses are used the options include having contact lenses for distance and wearing reading glasses over them for close vision, bifocal or multifocal contact lenses, or monovision, where one eye is fit with a lens to focus close and the other eye is fit with a lens to focus for distance or modified combinations of lenses and modes of wear.  

There are several new surgical procedures, utiliizing various artificial implanted lens devices which can also be used to correct presbyopia and restore near vision to those who have lost it do to the aging process. The surgical precedures all carry a certain amount of risk, and cost many times the amount of glasses or contact lenses.  Even with these surgical procedures,  glasses are sometimes needed for certain tasks, although many people having these procedures can do without glasses most of time.   In all of the surgical  procedures the  organic crystalline lens of the eye is removed leaving most of the natural lens capsule intact. The lens capsule is a transparent bag or sac  that envelops the natural organic crystalline lens. Only the front of the lens capsule is opened during implant surgery, and the lens capsule is used to hold the artificial intraocular lens implant(IOL).  

The lens in the eye can be replaced with a plastic intra ocular lens implant (IOL) called the Crystalens™. (shown above). The center optical portion of the .Crystalens™. is smaller than the original natural crystalline lens it replaces, but the outer carrier or haptic portion of the implant is a flexible spring-like material, which is tucked into the peripheral edges of the lens capsule bag. Like a focusing camera that has a lens that moves back and forth to allow focusing at different distances,  focusing ability is maintained in an eye with a Crystalens™. implant  by the still active ciliary muscle, pulling and releasing tension on fibers(called zonules) at the periphery of the bag which displaces the artificial Crystalens™. forward within the eye when focusing on near objects.  The Crystalens™. accomodates no greater than 1.00 or 1.75 dioptors, does not correct astigmatism, and while it generally gives good distance and intermediate vision, people find they still may need reading glasses for small close work.  Another implant device is the Alcon AcrySof® ReSTOR® IOL , often referred to as the "ReStor" lens.  It is placed in the lens capsule similar to traditional single vision IOLs, but the lens has concentric circular rings, which act as a diffraction grating to incorporate distance, intermediate and near focuses into the lenses.  Other IOLs in this category are the Array and ReZoom™ lenses (made by Advance Medical Optics).  The concentric ring design is able to bring more near focus into these lenses than the accomodating Crystalens™.,  The ReZoom design features an optimized multifocal surface (Balance View Optics) with five optical zones that optimize light distribution on the retina for varying lighting conditions and pupil sizes, but people sometimes find that their distance vision isn't as good because there may be glare at night caused by the rings. And of course the optical zone of the Crystalens™  is smaller than either the natural crystalline lens of the eye or the other multifocal IOLs, which could also cause glare problems at night, especially if the user has a larger pupil.  Usually these surgical precedures  are considered, along with the traditional single vision IOLs,  when people have cataract surgery, when the crystalline lens of the eye has not only become hard because of presbyopia, but has also become clouded.  Even in cataract surgery these multifocal devices are considered premium options by insurance companies and Medicare, and patients must pay  a premium charge for these lenses, above and beyond insurance imbursements. When the surgical implants are done to correct presbyopia in someone without a cataract it is called a Clear Lens Extraction (CLE)  and is considered to be entirely an elective procedure by medical insurance companies, who therefore  pay nothing towards these procedures.  A very good summary of options for presbyopia is contained on Dr. Wallace's LA Sight website. 

Despite claims by various lens makers that youth can be restored and presbyopia can be vanquished by various multifocal corrective options, all treatments for presbyopia involve some compromise.  Distance vision is not as good with a bifocal contact lens as it is with a single vision contact lens. Whenever a lens has multiple focuses there is less area of the lens available for any particular focusing distance than there is in dedicated single vision lenses (Single vision lenses are ones where the entire lens is made for a single focusing distance--for far distance focus only or for near focus only). The problems and limits of multifocal lenses are true whether we're talking about glasses, contact lenses, or intraocular lens implants.  Although the Crystalens™. is probably the closest thing so far to bringing back lost presbyopic accomodation, its ability to do this is limited to less than 2.00 Diopters.

It is the job of the optometrist and opthalmologist who prescribe these devices to present the various  presbyopic treatment options to each patient.  Given this information, it is hoped that together patient and doctor can make the best choices, based on the patient's history and lifestyle.