What is more dangerous: wearing contact lenses or laser correction?

Until about 2006–2008, there was a widespread opinion among doctors that contact lenses were safer than laser vision correction. In general, this point of view had the right to life: the usual LASIK gave up to 6% of complications, which, by modern standards, is considered almost barbaric.

However, Dr. William Matter, Frederick Roundfelder and Larry Rich conducted a study comparing the risk of using contact lenses and the risks of laser correction.

In short, soft lenses are more dangerous in the long run, and anything that is not one-day is about 6 times more dangerous. Details below.

It is rather difficult to compare directly laser correction and wearing contact lenses: it is difficult to take, say, 10 thousand patients and make them wear a lens on one eye, and the second to operate. And wait 30 years. Naturally, this approach is quite problematic, and therefore Matter, Fraundfelder and Rich approached the question differently.
')

Infections

The main danger of contact lenses (in terms of significant degradation or loss of vision) is bacterial keratitis, that is, inflammation of the cornea. You take the lens conditionally with “dirty” hands, set it in the eye, pour it with almost saline solution - and a kind of Petri dish forms between the lens and the cornea, where bacteria begin to vigorously and actively proliferate. That is why all the instructions to the lenses five or six times written about the need for hygiene and what to do if the eye suddenly became ill, itched, reddened or something else happened.

From clinical practice, we know that just under 5% of bacterial keratitis leads to significant vision problems. The term “significant problems” refers to situations where, for example, when a patient has significantly decreased vision or needs a cornea transplant.

Next - there is a study by Dr. Chang that 3.5 people per 10 thousand lens carriers get corneal inflammation if they wear one-day lenses, and 20 people (per 10 thousand) if long-wearing lenses are used.

The next logical step is the extrapolation of data on these cases for 30 years. The question is whether the relationship is linear. For this, doctors conducted an additional study, plus raised archives - it turned out that the risk of bacterial keratitis varies slightly as patients wear the lens (the eye does not produce additional protective mechanisms to protect against bacteria coming under the lenses).

Thus, researchers took the risk of significant complications as 1% (1 case per 100 people) when wearing one-day soft contact lenses in a 30-year term. The risk of deterioration in the quality of life is 5% in a 30-year term (in general, it is worsening when the patient sees 2 lines less in the table).

Laser correction

Here, similar risks are easier to calculate. Based on the research of Dr. Chang (1 case of keratitis per 800 patients, of these cases, 25% affect the patient’s quality of life, that is, are partially irreversible), this is 1/3200. Further, the authors of the study operate with Hammond data (32,068 patients, 10-year cross-section) and data from their Portland Institute (18 thousand operations, not a single case in a 10-year term). The final result is about the same as that of Chang.

It is worth noting that there is no experience with laser correction as with lenses: 30-year practice is only with PRK, and the more “young” LASIK was considered, therefore, to some extent, the authors extrapolate somewhat unreasonably. Nevertheless, even taking into account errors, the risks of keratitis in the case of wearing lenses are clearly higher.

Let me remind you that the flap methods (as reviewed by LASIK) form a wide arc incision in the cornea - about 340 degrees, at least 15 millimeters. Then this cut is closed on top of the usual epithelium. The ReLEx SMILE method is significantly less invasive - the cut size is usually 2.5–3 mm, and, accordingly, the risks should be less in theory (there are no practical studies yet).

Other risks

I recall the total risks of complications of laser correction: LASIK - up to 6%, femtoLASIK - up to 2%, ReLEx SMILE - 0.5–1% (depending on the generation of the laser). Read more about the risks here .

What is the most dangerous thing when wearing a lens?

In the first place are recorded infections. On the second one - pererashivanie lenses and subsequent hypoxic changes. Even the most oxygen-permeable soft lenses have a time limit for wearing. Most often it is 8 hours (open the instructions to your own and check, this is important). Often, an under-examined patient puts them on at 8 o'clock in the morning, and then takes it off at about 10 pm. The practical result is a lack of oxygen, the growth of vessels from the limbal opaque zone (and in the cornea there are usually no vessels and should not be) and their penetration into the cornea. With the subsequent unpleasant changes that with a long misuse of the lenses become irreversible.

Another reason to wear lenses is to frustrated pharmacists. I have repeatedly met patients who wear two-week lenses a week, leaving them overnight. Because the pharmacy said that you can wear two weeks, taking off for the night (well, or a week all the time). Remember: this is probably the most dangerous thing you can do with lenses. Check the instructions, carefully read what is the maximum duration of blocking access of oxygen to the eye and violation of osmotic processes in the cornea, that is, the period of wearing the lens.

All the rest is rather horror stories or shortcomings of old models of lenses. The following risks are possible:

• Erosion of the cornea, that is, damage to the eye as a result of friction on the lens and the simultaneous disruption of the exchange of tear fluid. As a rule, either the result of wearing the lens is greater than it should be (especially for those who are just starting to wear lenses and believe that a recommendation about 4 hours in the first weeks is a reinsurance), or a result of prolonged wearing of one-day lenses. The main symptom is blurring of vision. In the initial stages it is treated very simply, after 2 days the injury site is covered with epithelium. But if you run - may form an ulcer or other persistent phenomena. It becomes dark in the eyes - you must immediately remove the lenses and wait a bit. It does not work - running to the ophthalmologist, the speed of circulation here solves a lot.
  
  
• Banal allergies, most often - to a solution in which the lenses are cleaned or stored. As a rule, in the future nothing serious, in 7–10 days everything is normalized. There are complex toxic reactions in response to solutions, but they are extremely rare. Corniocylare irritation is more likely: in the symptoms itching and burning when wearing the lens and the feeling that it remains in the eye after removal (this is a toxic lesion).
  
  
• Giant papillary conjunctivitis. In 1998, risks were assessed from 1.8% to 15% depending on the types of lenses, since there have been no studies (theoretically, the risks have been greatly reduced due to oxygen-permeable one-day wearing lenses). This infection can wait for the active phase from 3 weeks to 4 years, then a characteristic thickening appears on the upper eyelid, and mucus begins to fall into the eye. If you catch in time - it will end in unpleasant, but not very painful washes. Skip - there will be multiple complications, in particular, all this "joy" can cause deep keratitis. It is very easy to diagnose conjunctivitis in the early stages of discomfort when wearing lenses, but a rare patient comes to the doctor at the same time.
  
  
• Keratitis of various origins. In addition to the already described bacterial, on the lenses or on the hands you can carry a fungus or viruses. Complications - corneal ulcers with acute pain, photophobia. Particularly interesting is acanthamous keratitis - these are microorganisms living in water. Lenses create ideal reproduction conditions for them. If you miss this type of keratitis (one of the most likely for carriers of lenses) - with a high probability will be corneal opacities.
  
  
• Long wearing lenses cause thinning of the cornea (keratocytes lose their ability to synthesize new tissue). This can happen even with proper wearing of lenses 3-5 years after use.
  
  
• In the case of a reaction to hypoxia (lack of oxygen), the main complication is manifested - the formation of new vessels. The patient does not feel anything, but the first changes are visible in the diagnosis almost immediately. The third stage - tissue with vessels grows between the Bowman's membrane and the epithelium, this (together with other related changes within the eye) has a serious effect on vision.

Since the publication of the main domestic studies, at least two generations of one-day contact lenses with a good oxygen permeability have appeared, therefore, in theory, the risks should be reduced. However, the main factors (the introduction of infection, squeezing the eyes, impaired circulation, etc.) remain.

Practice

1. Contact lenses for long wear almost 6 times more dangerous than one-day. It makes sense to think about changing the type of lenses to day. Well, or even about their need.
   
   
2. Always wash or disinfect hands when putting on and removing lenses. If you can't do it with guaranteed clean hands, don't do it better. Please note: in the instructions for your lenses, most likely, there is a phrase about the fact that you need to carry glasses for such a case (and it is not there by chance).
   
   
3. Be very careful when cleaning lenses for long periods of time and when to use them. Do not wear lenses with scratches or tears, this dramatically increases the risk of superficial keratitis.
   
   
4. Dry eyes after removing the lens is a sign of swelling. If there is such a thing - it’s better not to wear lenses for the next two weeks, and think about replacing them with glasses or making a correction.
   
   
5. Glasses are generally safer than lenses. Wear them whenever you can. You can not live without lenses - think about hard night lenses, they are safer compared to one-day ones (but glasses are even safer). About these lenses and their features will tell in detail later.